Three-Way Heat Exchange Module With Controlled Fluid Flow

Abstract

A three-way heat exchanger includes an airflow inlet, an airflow outlet, a heat transfer fluid inlet manifold extending proximate the airflow outlet, and a heat transfer fluid outlet manifold extending proximate the airflow outlet. The heat exchanger also includes panel assemblies each including a frame defining a heat transfer fluid channel and a membrane positioned on the frame and defining a desiccant channel. The heat transfer fluid channel is connected to the heat transfer fluid inlet and outlet manifolds for channeling a flow of the heat transfer fluid therebetween counter to the airflow direction. Each panel assembly also includes a heat transfer fluid flow guide positioned in the heat transfer fluid channel to control the flow of the heat transfer fluid counter to the airflow direction.

Description

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority to India patent application No. 202311086763, filed Dec. 19, 2023, the entire disclosure of which is incorporated by reference.

FIELD

The field relates generally to heating, ventilation, and air conditioning (HVAC) systems, and more particularly, to HVAC systems and methods including three-way heat exchange modules for transferring heat between a heat transfer fluid, a liquid desiccant, and air.

BACKGROUND

Heating, ventilation, and air conditioning (HVAC) systems are known for their heating, cooling, and moisture removal capabilities for treating outside air that is circulated through an indoor space. The vapor compression cycle is widely used in HVAC systems to regulate the temperature and humidity of the outside air. Typically, outside air is cooled below its dew point temperature to allow moisture in the air to condense on an evaporator coil, thus dehumidifying the air. Since this process often leaves the dehumidified air at an uncomfortably cold temperature, the air is then reheated to a temperature more comfortable to a user. The process of overcooling and reheating the air can become very energy-intensive and costly.

In some applications, HVAC systems include a vapor compression system used in combination with a liquid desiccant dehumidification system to remove moisture from the outside air without cooling it below its dew point temperature. For example, HVAC systems may include a refrigerant sub-system that operates under the vapor compression cycle and an air treatment sub-system that uses heat transfer fluid and liquid desiccant to simultaneously absorb heat (sensible cooling) and moisture (latent cooling) from warm outside air to produce cooled and dehumidified indoor air. The air treatment sub-system may include three-way heat transfer equipment that facilitates sensible and latent cooling of the warm outdoor air using the heat transfer fluid and the liquid desiccant.

In operation of a three-way heat exchanger, the liquid desiccant and heat transfer fluid are channeled through the heat exchanger and heat is transferred between the liquid desiccant and the heat transfer fluid. An outdoor air stream is directed through the heat exchanger, and heat transfer fluid absorbs heat from the air stream while the liquid desiccant absorbs moisture from the air stream. The liquid desiccant may circulate between the three-way heat exchanger and a regeneration system, in which diluted liquid desiccant rejects the absorbed moisture into a sacrificial fluid. The refrigerant sub-system interfaces with the air treatment sub-system, whereby refrigerant in an evaporation stage of the vapor compression cycle absorbs heat from the heat transfer fluid in the three-way heat exchanger. The refrigerant is then channeled to a condensing stage in which the refrigerant rejects the absorbed heat into another fluid. Liquid desiccant treated by the regeneration system and heat transfer fluid treated by the refrigerant sub-system is then channeled back toward the three-way heat exchanger to again provide sensible and latent cooling of outside air.

Three-way heat exchangers may include panels that channel the heat transfer fluid and the liquid desiccant therethrough for absorbing heat and moisture from the air stream that flows between the panels. The heat transfer fluid and liquid desiccant may flow freely through the panels and distribute across respective flow channels in each panel. Free (e.g., uncontrolled) flow and distribution of the working fluids across the panels may result in a very high temperature differential between the air stream and the fluids at localized regions of the panels, which may negatively impact performance of the heat exchanger. A need exists for a three-way heat exchanger that adequately controls flow and/or distribution of the working fluids through the panels during operation of the heat exchanger. In particular, a need exists for a three-way heat exchanger that facilitates controlling working fluid flow and distribution through the panels to provide a controlled temperature differential between the working fluid and the air stream across the panels.

This background section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.

SUMMARY

One aspect is a three-way heat exchanger operable to transfer heat between a heat transfer fluid, a liquid desiccant, and air. The three-way heat exchanger includes an airflow inlet, an airflow outlet, a heat transfer fluid inlet manifold extending proximate the airflow outlet, and a heat transfer fluid outlet manifold extending proximate the airflow inlet. The three-way heat exchanger also includes panel assemblies arranged with airflow gaps defined between adjacent panel assemblies to allow the air to flow between the airflow inlet and the airflow outlet in an airflow direction. Each panel assembly includes a frame defining a heat transfer fluid channel. The heat transfer fluid channel is connected to the heat transfer fluid inlet and outlet manifolds for channeling a flow of the heat transfer fluid therebetween counter to the airflow direction. Each panel assembly also includes a membrane positioned on the frame and defining a desiccant channel for a flow of the liquid desiccant, and a heat transfer fluid flow guide positioned in the heat transfer fluid channel to control the flow of the heat transfer fluid counter to the airflow direction. The heat transfer fluid flow guide defines a heat transfer fluid flow path including a series of passageways, each passageway extending across the airflow direction.

Another aspect is a three-way heat exchanger operable to transfer heat between a heat transfer fluid, a liquid desiccant, and air. The three-way heat exchanger includes a heat transfer fluid inlet manifold, a heat transfer fluid outlet manifold, and panel assemblies arranged with airflow gaps defined between adjacent panel assemblies to allow the air to flow through the three-way heat exchanger. Each panel assembly includes a frame defining a heat transfer fluid channel. The heat transfer fluid channel is connected to the heat transfer fluid inlet and outlet manifolds for channeling a flow of the heat transfer fluid through the panel assembly. Each panel assembly also includes two membranes positioned on the frame, each membrane defining a desiccant channel separated from the heat transfer fluid channel, and a heat transfer fluid flow guide positioned in the heat transfer fluid channel. The heat transfer fluid flow guide includes a sheet body and baffles. The baffles define a first flow path on one side of the sheet body and a second flow path on another side of the sheet body. The first and second flow paths are separated by the sheet body.

Another aspect is a heat exchanger operable to transfer heat between a heat transfer fluid and air. The heat exchanger includes a heat transfer fluid inlet manifold, a heat transfer fluid outlet manifold, and panel assemblies arranged with airflow gaps defined between adjacent panel assemblies to allow the air to flow through the heat exchanger. Each panel assembly includes a frame connected to the heat transfer fluid inlet and outlet manifolds, two plates positioned on the frame, the plates and the frame defining a heat transfer fluid channel for channeling the heat transfer fluid through the panel assembly, and a heat transfer fluid flow guide positioned in the heat transfer fluid channel. The heat transfer fluid flow guide includes a sheet body, baffles on the sheet body, the baffles defining a flow path for the heat transfer fluid in the heat transfer fluid channel, and protrusions on the sheet body to maintain a height of the heat transfer fluid channel, measured between the plates, when the heat transfer fluid is flowed through the heat transfer fluid channel at a negative pressure.

Various refinements exist of the features noted in relation to the above-mentioned aspects. Further features may also be incorporated in the above-mentioned aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to any of the illustrated embodiments may be incorporated into any of the above-described aspects, alone or in any combination.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic flow diagram of a heating, ventilation, and air conditioning (HVAC) system.

FIG. 2 is a front perspective of a three-way heat exchanger included in the HVAC system of FIG. 1.

FIG. 3 is a front perspective of the three-way heat exchanger, with various components omitted to show internal components.

FIG. 4 is a rear perspective of the three-way heat exchanger.

FIG. 5 is a rear perspective of the three-way heat exchanger with various components omitted, similar to FIG. 3.

FIG. 6 is a left side elevation of the three-way heat exchanger with various components omitted, similar to FIGS. 3 and 5.

FIG. 7 is a right side elevation of an example panel assembly included in the three-way heat exchanger of FIGS. 2-6.

FIG. 8 is an exploded view of the panel assembly of FIG. 7.

FIG. 9 is a schematic section of the panel assembly taken along section line 9-9 in FIG. 7.

FIGS. 10A-10D are enlarged views of the sections A, B, C, and D, respectively, shown in FIG. 8.

FIG. 11 is a schematic showing flow of liquid desiccant and heat transfer fluid through the three-way heat exchanger of FIGS. 2-6.

FIG. 12 is a perspective of a frame of the panel assembly of FIG. 7 and an example flow guide.

FIG. 13 is a right side elevation of the frame and the flow guide.

FIG. 14 is a left side elevation of the frame and the flow guide.

FIG. 15 is an exploded view of the frame and the flow guide.

FIG. 16A is an isolated perspective of the flow guide.

FIGS. 16B-E are various magnified views of portions of the flow guide.

FIG. 17 is a schematic showing uncontrolled flow of heat transfer fluid in the panel assembly of FIG. 7.

FIG. 18 is a time lapse of heat signatures of the panel assembly in an operation with uncontrolled flow of the heat transfer fluid as shown in FIG. 17.

FIG. 19 is a modeled comparison of the dew point temperature of an air stream (left image) flowing between adjacent panel assemblies and the temperature of uncontrolled flow of heat transfer fluid (right image) as shown in FIG. 17.

FIG. 20 is a schematic showing controlled flow of heat transfer fluid in the panel assembly of FIG. 7 using the flow guide of FIGS. 12-16.

FIG. 21 is another schematic showing controlled and partially restricted flow of heat transfer fluid in the panel assembly of FIG. 7 using the flow guide of FIGS. 12-16.

FIG. 22 is a time lapse of heat signatures of the panel assembly in an example operation with controlled flow of the heat transfer fluid as shown in FIG. 20 or FIG. 21.

FIG. 23 is a modeled comparison of the dew point temperature of an air stream (left image) flowing between adjacent panel assemblies and the temperature of controlled flow of heat transfer fluid (right image) as shown in FIG. 20 or FIG. 21.

Corresponding reference characters indicate corresponding parts throughout the drawings.

DETAILED DESCRIPTION

FIG. 1 is a schematic diagram of a heating, ventilation, and air conditioning (HVAC) system 100. The HVAC system 100 includes sub-systems 102-106 and a liquid desiccant circuit 108 which facilitate the heating, cooling, and moisture removal capabilities of the system 100. The sub-systems of the HVAC system 100 include a refrigerant sub-system 102, a conditioner sub-system 104, and a regenerator sub-system 106. The conditioner sub-system 104 and the regenerator sub-system 106 are usable to respectively treat first and second inlet air streams 110 and 114, and may be referred to herein as air treatment sub-systems 104 and 106. The HVAC system 100 may include additional components or other components than those shown and described with reference to FIG. 1.

In an example operating mode of the HVAC system 100, the conditioner sub-system 104 removes heat from the first inlet air stream 110 and channels a conditioned outlet air stream 112 to a conditioned space (not shown), such as an interior of a building structure or vehicle. The conditioned outlet air stream 112 exiting the conditioner sub-system 104 may have a lower temperature than the first inlet air stream 110. Heat removed from the first inlet air stream 110 is transferred from the conditioning sub-system 104, to the refrigerant sub-system 102, and finally to the regenerator sub-system 106. The regenerator sub-system 106 transfers the heat into the second inlet air stream 114 and channels a heated outlet air stream 116 to the atmosphere.

The refrigerant sub-system 102 includes an evaporator 118, a condenser 120, a compressor 122, and an expansion valve 124. The compressor 122 may be any suitable compressor including, but not limited to, scroll, reciprocating, rotary, screw, and centrifugal compressors. The expansion valve 124 may be any suitable expansion valve, such as a thermal expansion valve. The expansion valve 124 may alternatively be any suitable expansion device, such as an orifice or capillary tube for example. The refrigerant sub-system 102 also includes a refrigerant loop 126 that circulates a working fluid, such as a refrigerant, between the evaporator 118, the compressor 122, the condenser 120, and the expansion valve 124. The refrigerant sub-system 102 may include additional components or other components than those shown and described with reference to FIG. 1.

In an example operation of the refrigerant sub-system 102, the refrigerant in the loop 126 is channeled as a low pressure gas refrigerant 128 toward the compressor 122. The compressor 122 compresses the gas refrigerant 128, which raises the temperature and pressure of the refrigerant. Pressurized, high temperature gas refrigerant 130 exits the compressor 122 and is channeled toward the condenser 120, where the high pressure gas refrigerant 130 is condensed to a high pressure liquid refrigerant 132. The liquid refrigerant 132 exiting the condenser 120 is channeled toward the expansion valve 124 that reduces the pressure of the liquid. The reduced pressure fluid refrigerant 134, which may be a gas or a mixture of gas and liquid after passing through the expansion valve 124, is then channeled toward the evaporator 118. The fluid refrigerant 134 evaporates to a gas in the evaporator 118, exiting the evaporator as the low pressure gas refrigerant 128. The gas refrigerant 128 is then channeled back toward the compressor 122, where the gas refrigerant 128 is again compressed and the process repeats. Circulation of the refrigerant in the loop 126 may be driven by the compressor 122, and, more particularly, by a pressure differential that exists between the pressurized, high temperature gas refrigerant 130 exiting the compressor 122 and the low pressure gas refrigerant 128 entering the compressor 122. The direction of flow of the refrigerant through the loop 126, as shown in FIG. 1, may be reversed to switch the heat transfer functions of the evaporator 118 and the condenser 120, and enable the HVAC system 100 to operate in various operating modes.

The conditioner sub-system 104 includes a first three-way heat exchanger 136 and a conditioner heat transfer fluid loop 138 that circulates a conditioner heat transfer fluid (e.g., water, a glycol-based fluid, or any combination thereof) to and from the first three-way heat exchanger 136. The conditioner sub-system 104 interfaces with the refrigerant sub-system 102 via the evaporator 118. In particular, the evaporator 118 is included in the refrigerant loop 126 and the conditioner heat transfer loop 138, and facilitates transfer of heat from the conditioner heat transfer fluid in the loop 138 into the fluid refrigerant 134 in the refrigerant loop 126. The conditioner sub-system 104 may include additional components or other components than those shown and described with reference to FIG. 1. For example, the conditioner sub-system 104 may include one or more pumps (not shown) for circulating the conditioner heat transfer fluid in the loop 138 between the first three-way heat exchanger 136 and the evaporator 118. Suitable pumps that may be included in the conditioner sub-system 104 include, for example, centrifugal pumps, diaphragm pumps, positive displacement pumps, or any type of pump suitable for transferring liquid. The conditioner sub-system 104 may include additional heat transfer equipment that transfers heat from the conditioner heat transfer fluid into the atmosphere, or vice versa, depending on the operational requirements of the HVAC system 100 and other factors (e.g., a temperature and/or humidity of the first air inlet stream 110).

In an example operation of the conditioner sub-system 104, the conditioner heat transfer fluid in the loop 138 is channeled toward the evaporator 118. The conditioner heat transfer fluid is cooled in the evaporator 118 as heat is transferred from the conditioner heat transfer fluid into the fluid refrigerant 134 in the loop 126 to produce the gas refrigerant 128. Cooled conditioner heat transfer fluid 140 exiting the evaporator 118 is channeled toward and enters the first three-way heat exchanger 136. The first inlet air stream 110 is also directed through the first three-way heat exchanger 136. The first three-way heat exchanger 136 transfers heat from the first inlet air stream 110 into the conditioner heat transfer fluid 140, thus heating the conditioner heat transfer fluid. The heated conditioner heat transfer fluid 142 exiting the first three-way heat exchanger 136 is channeled back toward the evaporator 118 and the process repeats.

The regenerator sub-system 106 includes a second three-way heat exchanger 144 and a regenerator heat transfer fluid loop 146 that circulates a regenerator heat transfer fluid (e.g., water, a glycol-based fluid, or any combination thereof) to and from the second three-way heat exchanger 144. The regenerator sub-system 106 interfaces with the refrigerant sub-system 102 via the condenser 120. In particular, the condenser 120 is included in the refrigerant loop 126 and the regenerator heat transfer loop 146, and facilitates transfer of heat from the pressurized gas refrigerant 130 in the refrigerant loop 126 into the regenerator heat transfer fluid. The regenerator sub-system 106 may include additional components or other components than those shown and described with reference to FIG. 1. For example, the regenerator sub-system 106 may include one or more pumps (not shown) for circulating the regenerator heat transfer fluid in the loop 146 between the three-way heat exchanger 144 and the condenser 120. Suitable pumps that may be included in the regenerator sub-system 106 include, for example, centrifugal pumps, diaphragm pumps, positive displacement pumps, or any type of pump suitable for transferring liquid. The regenerator sub-system 106 may include additional heat transfer equipment that transfers heat from the atmosphere into the regenerator heat transfer fluid, or vice versa, depending on the operational requirements of the HVAC system 100 and other factors (e.g., a temperature and/or humidity of the first air inlet stream 110).

In an example operation of the regenerator sub-system 106, the regenerator heat transfer fluid in the loop 146 is channeled toward the condenser 120. The regenerator heat transfer fluid is heated in the condenser as heat is transferred from the pressurized gas refrigerant 130 in the loop 126 into the regenerator heat transfer fluid to produce the liquid refrigerant 132. Heated regenerator heat transfer fluid 148 exiting the condenser is channeled toward and enters the second three-way heat exchanger 144. The second inlet air stream 114 is also directed through the second three-way heat exchanger 144. The second three-way heat exchanger 144 transfers heat from the regenerator heat transfer fluid into the second inlet air stream 114, thus cooling the regenerator heat transfer fluid. The heated outlet air stream 116 exiting the second three-way heat exchanger 144 has a greater temperature than the second inlet air stream 114. The cooled regenerator heat transfer fluid 150 exiting the three-way heat exchanger 144 is channeled back toward the condenser 120 and the process repeats.

The HVAC system 100 also includes the liquid desiccant circuit 108 that operates in conjunction with the sub-systems 102-106 to facilitate conditioning the first inlet air stream 110 by latent and sensible cooling. The liquid desiccant circuit 108 includes a liquid desiccant that is channeled between the first and second three-way heat exchangers 136 and 144. Suitable liquid desiccants that may be used in the liquid desiccant circuit 108 include, for example, desiccant salt solutions, such as solutions of water and lithium chloride (LiCl), lithium bromide (LiBr), calcium chloride (CaCl₂)), or any combination thereof, triethylene glycol, sodium hydroxide, sulfuric acid, and so-called ionic liquid desiccants, or organic salts that are liquid at room temperature and have organic cations and organic or inorganic anions.

The liquid desiccant circuit 108 may include one or more pumps (not shown) for channeling the liquid desiccant between the first three-way heat exchanger 136 and the second three-way heat exchanger 144. Suitable pumps that may be included in the liquid desiccant circuit 108 include, for example, centrifugal pumps, diaphragm pumps, positive displacement pumps, or any type of pump suitable for transferring liquid. The liquid desiccant circuit 108 may include one or more pumps for transferring the liquid desiccant from the second heat exchanger 144 toward the first heat exchanger 136 and one or more pumps for transferring the diluted liquid desiccant 154 from the first heat exchanger 136 toward the second heat exchanger 144.

Concentrated liquid desiccant 152 in the liquid desiccant circuit 108 is channeled toward the first three-way heat exchanger 136 of the conditioner sub-system 104, where the concentrated liquid desiccant 152 removes moisture from the first inlet air stream 110. The concentrated liquid desiccant 152 cooperates with the cooled conditioner heat transfer fluid 140 in the first three-way heat exchanger 136 to absorb heat and moisture from the first inlet air stream 110. The conditioned outlet air stream 112 exiting the first three-way heat exchanger 136 may have a lower humidity and/or a lower temperature than the first inlet air stream 110. The liquid desiccant, having absorbed moisture from the first inlet air stream 110, exits the first three-way heat exchanger 136 as diluted liquid desiccant 154.

The diluted liquid desiccant 154 is channeled toward the second three-way heat exchanger 144 of the regenerator sub-system 106, where the diluted liquid desiccant 154 rejects moisture into the second inlet air stream 114. The diluted liquid desiccant 154 cooperates with the heated regenerator heat transfer fluid 148 in the second three-way heat exchanger 144 to reject heat and moisture into the second inlet air stream 114. The heated outlet air stream 116 exiting the second three-way heat exchanger 144 thus has a greater humidity as well as a higher temperature than the second inlet air stream 114. The liquid desiccant, having rejected moisture into the second inlet air stream 114, exits the regenerator sub-system 106 as concentrated liquid desiccant 152. The concentrated liquid desiccant 152 exiting the second three-way heat exchanger 144 is channeled back toward the first three-way heat exchanger 136, and the process repeats.

The liquid desiccant circuit 108 may also include a desiccant-desiccant heat exchanger 156 for transferring heat from the concentrated liquid desiccant 152 that has exited the second three-way heat exchanger 144 to the diluted liquid desiccant 154 that has exited the first three-way heat exchanger 136. The desiccant-desiccant heat exchanger 156 may facilitate improving the functions of the liquid desiccant in the three-way heat exchangers 136 and 144. For example, the desiccant-desiccant heat exchanger 156 may reduce a temperature of the concentrated liquid desiccant 152 to provide greater cooling and dehumidifying capabilities of the first three-way heat exchanger 136. Additionally and/or alternatively, the desiccant-desiccant heat exchanger 156 may increase a temperature of the diluted liquid desiccant 154 to enable the diluted liquid desiccant 154 to desorb a greater amount of moisture in the second three-way heat exchanger 144. The desiccant-desiccant heat exchanger 156 may be an inline heat exchanger or any suitable heat exchanger that facilitates direct heat transfer between the concentrated liquid desiccant 152 and the diluted liquid desiccant 154. The desiccant-desiccant heat exchanger 156 may alternatively facilitate indirect heat exchange between the concentrated liquid desiccant 152 and the diluted liquid desiccant 154, such as via a vapor compression heat pump. Auxiliary heating and cooling sources (e.g., heating and cooling fluid, such as water) may also be utilized, in addition to or in lieu of the heat exchanger 156, to respectively heat the diluted liquid desiccant 154 and cool the concentrated liquid desiccant 152. The liquid desiccant circuit 108 may include additional components or other components than those shown and described with reference to FIG. 1.

Thus, in the example operating mode of the HVAC system 100, sensible cooling of the first inlet air stream 110 is facilitated by the first three-way heat exchanger 136 of the conditioner sub-system 104, which transfers heat from the inlet air stream 110 into the conditioner heat transfer fluid. The heat removed from the first inlet air stream 110 is then transferred sequentially between the sub-systems 104, 102, and 106 via the evaporator 118 and the condenser 120, and eventually is rejected into the second inlet air stream 114 via the second three-way heat exchanger 144. Latent cooling of the first inlet air stream 110 is also facilitated by the first three-way heat exchanger 136, which removes moisture from the inlet air stream 110 using the concentrated liquid desiccant 152. The moisture absorbed by the diluted liquid desiccant 154 is desorbed in the second three-way heat exchanger 144 into the second inlet air stream 114, which regenerates the concentrated liquid desiccant 152 that is then channeled back toward the first three-way heat exchanger 136.

The HVAC system 100 may operate in alternative operating modes than the example operating mode described above with reference to FIG. 1. The example operating mode of the HVAC system 100 described above may be considered a warm weather operating mode of the HVAC system 100, in which warm, humid air in the first inlet air stream 110 is cooled and dehumidified using the conditioner sub-system 104 and the heat and moisture removed is transferred by the sub-systems 102 and 106 and the liquid desiccant circuit 108 and rejected into the second inlet air stream 114 to produce the heated, humidified outlet air stream 116 that is directed into the warm, humid ambient. In a cold weather operating mode of the HVAC system 100, the operation of the sub-systems 102-106 and the liquid desiccant circuit 108 may be reversed such that the first three-way heat exchanger 136 heats and humidifies cool, dry air in the first inlet air stream 110 to produce warm air with a comfortable humidity level in the outlet air stream 112 that is channeled to a conditioned space. In the cold weather operating mode, the direction of flow of the refrigerant in the loop 126 and the liquid desiccant in the liquid desiccant circuit 108 may be reversed, such that the air treatment sub-systems 104 and 106 switch their respective functions, or intake and outlet vents for the first and second inlet air streams 110 and 114 may be rearranged and/or reconfigured such that the direction of airflow directed through the first and second three-way heat exchangers 136 and 144 is reversed, with the outlet air stream 112 being channeled toward the ambient environment and the outlet air stream 116 being channeled toward the conditioned space. In still other operating modes of the HVAC system 100, depending on the operational requirements and desired setpoint temperature and humidity level within the conditioned space, one of the air treatment sub-system 104 and 106 may be idle or omitted from the HVAC system 100. For example, the air treatment sub-system 106 may be omitted and the refrigerant sub-system 104 may reject or absorb heat from a refrigerant-air heat exchanger 120, depending on the operating mode of the HVAC system 100. Where the regenerator sub-system 106 is omitted or idle, liquid desiccant in the liquid desiccant circuit 108 that is cycled through the first three-way heat exchanger 136 may be regenerated or diluted, depending on the operating mode of the HVAC system 100, using auxiliary regeneration equipment, dilution tanks, or the like.

Still with reference to FIG. 1, the first three-way heat exchanger 136 and the second three-way heat exchanger 144 have substantially the same configuration. In alternative embodiments, the first three-way heat exchanger 136 and the second three-way heat exchanger 144 may have a different configuration. Although the conditioner sub-system 104 and the regenerator sub-system 106 are shown in FIG. 1 to include one three-way heat exchanger 136 and 144, respectively, any suitable number of three-way heat exchangers 136 and 144 may be included in the respective sub-system 104 and 106. The number of three-way heat exchangers 136 included in the conditioner sub-system 104 may be the same or different than the number of three-way heat exchangers 144 included in the regenerator sub-system 106. Where the conditioner sub-system 104 includes multiple three-way heat exchangers 136, the heat exchangers 136 may operate in series, in parallel, or any combination thereof. Where the regenerator sub-system 106 includes multiple three-way heat exchangers 144, the heat exchangers 144 may operate in series, in parallel, or any combination thereof.

Referring now to FIGS. 2-5, an example three-way heat exchanger 200 for use in an air treatment sub-system of the HVAC system 100 of FIG. 1 will now be described. The three-way heat exchanger 200 may be implemented as a first three-way heat exchanger 136 in the conditioner sub-system 104 and/or as a second three-way heat exchanger 144 in the regenerator sub-system 106. FIG. 2 is a front perspective of the three-way heat exchanger 200. FIG. 3 is a front perspective of the three-way heat exchanger 200 with various components omitted to show internal components of the three-way heat exchanger 200. FIG. 4 is a rear perspective of the three-way heat exchanger 200. FIG. 5 is a rear perspective of the three-way heat exchanger 200 with various components omitted, similar to FIG. 3.

The three-way heat exchanger 200 has a dimension in the X-axis, Y-axis and Z-axis, respectively. The X-axis, Y-axis and Z-axis are each mutually perpendicular. As described herein with respect to the three-way heat exchanger 200 and components of the heat exchanger 200 when assembled, dimensions in the Z-axis may be referred to as a “height,” dimensions in the Y-axis may be referred to as a “length,” and dimensions in the X-axis may be referred to as a “width.” The three-way heat exchanger 200 defines a lateral direction in the X-axis, a longitudinal direction in the Y-axis, and a vertical direction in the Z-axis. The X-axis may also be referred to herein as a lateral axis, the Y-axis may also be referred to herein as a longitudinal axis, and the Z-axis may also be referred to herein as a vertical axis. The three-way heat exchanger 200 has respectively opposite first and second lateral sides 202 and 204, first and second longitudinal sides 206 and 208, and first and second vertical sides 210 and 212. The first and second lateral sides 202 and 204 are spaced apart in the lateral direction, the first and second longitudinal sides 206 and 208 are spaced apart in the longitudinal direction, and the first and second vertical sides 210 and 212 are spaced apart in the vertical direction. Directional terms are used for solely for description of the three-way heat exchanger 200 and the spatial relation of the components of the heat exchanger. The examples shown and described are not limited to any particular orientation.

The three-way heat exchanger 200 includes a set of panel assemblies 214 arranged in succession or series in the lateral direction between the first lateral side 202 and the second lateral side 204. The individual panel assemblies 214 will be described in more detail below with reference to FIGS. 7-10. Each panel assembly 214 is in the form of a plate structure that has an internal heat transfer fluid channel through which a heat transfer fluid, such as the conditioner heat transfer fluid in the loop 138 or regenerator heat transfer fluid in the loop 146, flows. Each panel assembly 214 also includes liquid desiccant channels on opposite sides of the heat transfer fluid channel. A liquid desiccant, such as the concentrated liquid desiccant 152 or the diluted liquid desiccant 154 in the liquid desiccant circuit 108, flows through the liquid desiccant channels. Liquid desiccant flowing through the liquid desiccant channels is separated from the heat transfer fluid flowing through the heat transfer fluid channel of the respective panel assembly, and heat is exchanged between the liquid desiccant in the liquid desiccant channels and the heat transfer fluid flowing through the heat transfer fluid channel. Airflow gaps 216, also referred to as air gaps 216, are defined between adjacent panel assemblies 214 in the lateral direction. Each airflow gap 216 extends primarily in the vertical and longitudinal directions.

Any suitable number of panel assemblies 214 may be included in the three-way heat exchanger 200. For example, the three-way heat exchanger 200 may include from 1 to 200 panel assemblies 214, from 1 to 100 panel assemblies 214, from 50 to 200 panel assemblies 214, from 50 to 100 panel assemblies 214, such as one panel assembly, ten panel assemblies 214, twenty panel assemblies 214, thirty panel assemblies 214, forty panel assemblies 214, fifty panel assemblies 214, sixty panel assemblies 214, seventy panel assemblies 214, eighty panel assemblies 214, ninety panel assemblies 214, 100 panel assemblies 214, or greater than 100 panel assemblies 214.

The panel assemblies 214 are supported on a base 240 at the second vertical side 212 of the three-way heat exchanger 200. The panel assemblies 214 extend substantially parallel to one another between the base 240 and the first vertical side 210 of the three-way heat exchanger 200. The panel assemblies 214 may, in an example operation of the three-way heat exchanger 200, deviate from a substantially parallel extent as fluid flows through the panel assemblies 214 and/or as air flows through the air gaps 216 between adjacent panel assemblies 214.

The three-way heat exchanger 200 includes a first end plate 218 and a second end plate 220 at the first and second lateral sides 202 and 204, respectively. The end plates 218, 220 may also be referred to as end covers or end sheets. The end plates 218 and 220 may provide lateral support for the set of panel assemblies 214 and enclose an interior 222 of the three-way heat exchanger 200 at the first and second lateral sides 202 and 204. The end plates 218 and 220 are omitted from FIGS. 3 and 5 to show the arrangement of the panel assemblies 214, the airflow gaps 216 defined between adjacent panel assemblies 214, and the interior 222 of the three-way heat exchanger 200 in greater detail.

Each end plate 218 and 220 includes alignment apertures 258 and 260, respectively, for receiving clamping assemblies (not shown) used to clamp the panel assemblies 214 together. Example clamping assemblies suitable for use in the three-way heat exchanger 200 are described in U.S. patent application Ser. No. 18/490,984, filed Oct. 20, 2023, the disclosure of which is incorporated by reference in its entirety.

The interior 222 of the three-way heat exchanger 200 may be enclosed at the first and second vertical sides 210 and 212 of the three-way heat exchanger by the set of panel assemblies 214. For example, adjacent panel assemblies 214 may be connected and/or in contact with one another at opposite vertical ends to seal the respective airflow gap 216 defined therebetween at the opposite vertical ends and to enclose the interior 222 of the three-way heat exchanger at the first and second vertical sides 210 and 212. Additionally and/or alternatively, the three-way heat exchanger 200 may include vertical end plates (not shown) to enclose the interior 222 at the first and second vertical sides 210 and 212.

The three-way heat exchanger 200 includes an airflow inlet 224 on the first longitudinal side 206 and an airflow outlet 226 on the second longitudinal side 208. The airflow inlet 224 and the airflow outlet 226 are respectively defined by longitudinal side panels 228 and 230 of the three-way heat exchanger 200. For example, the longitudinal side panels 228 and 230 may include openings in the form of grated or grille openings, shutters, louvers, dampers, or may have any other suitable open configuration to enable airflow to enter into and exit the three-way heat exchanger 200. In some examples, one or both of the longitudinal side panels 228 and 230 may include a filter to filter particulate and/or contaminants from an air stream that is treated by the three-way heat exchanger 200. The airflow inlet 224 and the airflow outlet 226 are in communication with the airflow gaps 216 defined between the adjacent panel assemblies 214, and allow an inlet air stream (e.g., the first or second inlet air stream 110 or 114 in FIG. 1) to flow in an airflow direction (indicated by the arrow 278 in FIG. 2) through the three-way heat exchanger 200 in the longitudinal direction (e.g., horizontally). The airflow direction 278 is in the longitudinal direction in the illustrated example. The airflow direction 278 may be additionally and/or alternatively be in the lateral and/or vertical directions. The longitudinal side panels 228 and 230 are omitted from FIGS. 3 and 5 to show the arrangement of the panel assemblies 214, the airflow gaps 216 defined between adjacent panel assemblies 214, and the interior 222 of the three-way heat exchanger 200 in greater detail.

The three-way heat exchanger 200 also includes heat transfer fluid inlet 232 and outlet 234 and liquid desiccant inlet 236 and outlet 238. Heat transfer fluid (e.g., circulating in one of the heat transfer fluid loops 138 or 146 in FIG. 1) enters into and exits the three-way heat exchanger 200 via the heat transfer fluid inlet 232 and outlet 234, respectively. Liquid desiccant (e.g., circulating the liquid desiccant circuit 108 in FIG. 1) enters into and exits the three-way heat exchanger 200 via the liquid desiccant inlet 236 and outlet 238, respectively. The locations of the heat transfer fluid inlet 232 and outlet 234 and the liquid desiccant inlet 236 and outlet 238 may vary depending on a desired flow direction of the heat transfer fluid and the liquid desiccant through the panel assemblies 214. The liquid desiccant inlet 236 and the heat transfer fluid outlet 234 may be defined by (e.g., made integral with) the end plate 218 and the liquid desiccant outlet 238 and the heat transfer fluid inlet 232 may be defined by (e.g., made integral with) the end plate 220. Alternatively, the heat transfer fluid inlet 232 and outlet 234 and the liquid desiccant inlet 236 and outlet 238 may each be defined by a conduit (e.g., a pipe, tube, hose, or other suitable fluid conduit) that extends longitudinally through an opening in the respective end plate 218 and 220.

Referring to FIGS. 7-9, an example panel assembly 300 suitable for use as the individual panel assemblies 214 will now be described. In the example three-way heat exchanger 200, all the panel assemblies 214 have substantially the same configuration as the panel assembly 300 shown in FIGS. 7-9. The panel assemblies 214 will be referred to as the panel assemblies 300 hereinafter for convenience of description. Some of or all the panel assemblies 214 may include additional components, fewer components, or other components than the panel assembly 300.

FIG. 7 is a right side elevation of the example panel assembly 300. FIG. 8 is an exploded view of the panel assembly 300. FIG. 9 is a schematic section of the panel assembly 300 taken along section line 9-9 in FIG. 7. The spatial relation of components of the panel assembly 300 will be described with respect to the X-axis, Y-axis, and Z-axis, and the lateral direction, longitudinal direction, and vertical direction defined by the three-way heat exchanger 200. The panel assembly 300 will also be described in the orientation when implemented and installed in the three-way heat exchanger 200. Directional terms are used to describe components of the panel assembly 300 solely for convenience of description. The examples shown and described are not limited to any particular orientation.

The panel assembly 300 includes a frame 302 that defines first and second vertical ends 304 and 306, in the Z-axis, first and second lateral faces 305 and 307, in the X-axis, and first and second longitudinal ends 308 and 310, in the Y-axis, of the panel assembly 300. The frame 302 includes opposite first and second header sections 312 and 314 respectively located at the first and second vertical ends 304 and 306. The frame 302 also includes a middle section 316 between the opposite header sections 312 and 314. The header sections 312 and 314 respectively define liquid desiccant header areas 320 and 322. The middle section 316 defines a heat transfer fluid area 324. The liquid desiccant header areas 320 and 322 are separated from the heat transfer fluid area 324 by portions of the frame 302 that respectively extend between the heat transfer fluid area 324 and one of the liquid desiccant header areas 320 and 322.

The panel assembly 300 also includes first and second plates 326 and 328 disposed on opposite lateral faces of the frame 302, covering the middle section 316 of the frame 302. The first and second plates 326 and 328 be a sheet of material that is, for example, less than 0.5 inch thick, or less than 0.25 inch thick, and the plates 326, 328 may also be referred to as “heat exchange sheets” or “sheets.” The first and second plates 326 and 328 may be attached to the frame 302 or may be made integral with the frame 302. Suitable techniques for attaching the plates 326 and 328 to the frame 302 may include, for example, welding (e.g., laser, induction, or radio-frequency welding), adhesive bonding, thermal bonding, or another suitable technique for joining materials together. Additional detail on attaching the plates 326 and 328 to the frame 302 is described, for example, in U.S. Pat. No. 11,022,330, issued on Jun. 1, 2021, U.S. Pat. No. 10,921,001, issued on Feb. 16, 2021, the disclosure of which is incorporated by reference in its entirety.

The frame 302 and the plates 326 and 328 may be made from dissimilar but compatible materials for welding together. For example, the frame 302 and the plates 326 and 328 may each be made from the same or different thermoplastic or polymer materials. The material used for the frame 302 and the plates 326 and 328 may also be selected based on its compatibility with the liquid desiccant used in the three-way heat exchanger 200. Suitable polymer materials for the frame 302 and the plates 326 and 328 include, for example, polyolefins (e.g., polypropylene and/or polyethylene), acrylonitrile butadiene styrene (ABS), and combinations thereof. The plates 326 and 328 may include additives that improve properties such as laser-absorbing and conductivity properties, as well as the strength and/or stiffness of the plates 326 and 328. In other examples, the frame 302 and the plates 326 and 328 may be made from any other suitable materials that enable the three-way heat exchanger 200 to function as described.

The plates 326 and 328 envelop and seal the heat transfer fluid area 324 of the frame, defining a heat transfer fluid channel 330 of the panel assembly 300 between the plates 326 and 328 (see FIG. 9). As described below, in an example operation of the three-way heat exchanger 200, heat transfer fluid flows between the plates 326 and 328 through the heat transfer fluid channel 330 and liquid desiccant flows over an outer surface of the plates 326 and 328, opposite the heat transfer fluid channel 330. The plates 326 and 328 isolate the liquid desiccant from the heat transfer fluid in the channel 330, and allow heat to transfer between the liquid desiccant and the heat transfer fluid. The plates 326 and 328 may extend over one or both of liquid desiccant header areas 320 and 322 and define openings (e.g., apertures 360) that align with the one or both of the liquid desiccant header areas 320 and 322 to enable liquid desiccant to flow therethrough. In the example panel assembly 300, each of the plates 326 and 328 includes a series of apertures 360 located adjacent the liquid desiccant header 320 and a series of apertures 362 located adjacent the liquid desiccant header area 322. Liquid desiccant may flow through the apertures 360 and 362 of each plate 326 and 328 to enter and/or exit the liquid desiccant header area 320 and 322, respectively.

A flow guide 400 (shown, e.g., in FIG. 12) may be positioned in the heat transfer fluid channel 330 to control flow and/or distribution of the heat transfer fluid in the heat transfer fluid channel. The flow guide 400 may also maintain a width of the heat transfer fluid channel under negative pressure, facilitate constant flow rates of the heat transfer fluid through the channel 330, and/or provide turbulation of the heat transfer fluid to increase heat transfer with the liquid desiccant and air flowing over the outer surfaces of the plates 326 and 328. The flow guide 400 is described in more detail below. A wide variety of materials may be used for the flow guide 400. For example, the flow guide 400 may include the same polymer material as the plates (e.g., polyolefins, ABS, or combinations thereof). Additionally and/or alternatively, the flow guide 400 may include polyethylene terephthalate (PETG).

Referring again to FIGS. 7-9, the panel assembly 300 also includes membranes 332 and 334 disposed on the opposite lateral faces 305 and 307 of the frame 302. In other examples, only one of the membranes 332 or 334 may be included in the panel assembly 300. The membranes 332 and 334 cover the outer surfaces of the plates 326 and 328. As shown in FIG. 9, liquid desiccant channels 336 and 338 are respectively defined between the membrane 332 and the plate 326 and the membrane 334 and the plate 328. The membranes 332 and 334 also envelop and seal the liquid desiccant header areas 320 and 322. Each liquid desiccant channel 336 and 338 connects the liquid desiccant header areas 320 and 322 in fluid communication. As described below, in an example operation of the three-way heat exchanger 200, liquid desiccant flows through one of the liquid desiccant header areas 320 or 322, into the liquid desiccant channels 336 and 338, over the outer surfaces of the plates 326 and 328 and behind the membranes 332 and 334, and finally into the other one of the liquid desiccant header areas 320 or 322. The plates 326 and 328 limit contact between the liquid desiccant flowing in the liquid desiccant channels 336 and 338 and heat transfer fluid flowing through the heat transfer fluid channel 330, and enable heat to transfer therebetween. In examples where only one of the membranes 332 or 334 is included in the panel assembly 300, only one liquid desiccant channel 336 or 338 may be defined between the membrane 332 or 334 and the plate 326 or 328. In these examples, the plate 326 or 328 on the lateral face 305 or 307 opposite the liquid desiccant channel 336 or 338 may envelop and seal the liquid desiccant header areas 320 and 322 and restrict flow of liquid desiccant opposite the liquid desiccant channel 336 or 338.

The membranes 332 and 334 are attached to one of the lateral faces 305 and 307, respectively, of the frame 302 to envelop and seal the liquid desiccant header areas 320 and 322. The membranes 332 and 334 may additionally and/or alternatively be attached to the outer surface of the respective plate 326 and 328, which may facilitate maintaining a width of the liquid desiccant channels 336 and 338 and/or limiting a propensity of the membranes 332 and 334 to bulge outward when liquid desiccant flows through the liquid desiccant channels 336 and 338. The membranes 332 and 334 may be attached to the lateral faces 305 and 307 of the frame 302 and/or the outer surfaces of the plates 326 and 328 using any suitable technique, such as adhesive bonding, heat sealing, or welding, for example. The membranes 332 and 334 may be respectively attached to the plates 326 and 328 directly by heat sealing or welding where compatible materials (e.g., polyolefins) are used for the membranes 332 and 334 and the respective plates 326 and 328. An outer bonding layer (not shown) may be applied over the outer surfaces of the plates 326 and 328 to improve the quality or case of forming the heat seals or welds with the respective membranes 332 and 334. The outer surfaces of the plates 326 and 328 may include raised patterns or dot features (not shown) to which the membranes 332 and 334 are adhered, heat sealed, or otherwise attached. The raised patterns may be formed on the frame 302 and/or plates 326 and 328 by thermoforming, embossing, or other suitable techniques. Attaching the membranes 332 and 334 to the dot features or raised patterns may provide an additional advantage of facilitating uniform distribution of the liquid desiccant across the liquid desiccant channels 336 and 338 in the longitudinal direction and reducing stresses that can lead to warping of the plates 326 and 328. Warping of the plates 326 and 328 may degrade the ability to transfer heat and moisture between the heat transfer fluid, the liquid desiccant, and air that flows across the membranes 332 and 334 in an example operation of the three-way heat exchanger 200. Additional detail on attaching the membranes 332 and 334 to the frame 302 and the respective plates 326 and 328 is described in U.S. Pat. No. 11,022,330, issued on Jun. 1, 2021, and U.S. Pat. No. 10,921,001, issued on Feb. 16, 2021, the disclosures of each of which are hereby incorporated herein by reference in their entirety.

The membranes 332 and 334 are made of a vapor-permeable material that permits transfer of water vapor therethrough to enable liquid desiccant flowing in the liquid desiccant channels 336 and 338 to absorb moisture from and desorb moisture into air flowing across the membranes 332 and 334. In some examples, the membranes 332 and 334 may each be made from a polypropylene material or other suitable vapor-permeable polymer material. The vapor-permeable material used for the membranes 332 and 334 may be microporous (e.g., having a pore size less than 0.5 micrometers (μm)). Examples of suitable microporous membranes are disclosed in U.S. Pat. No. 9,101,874, issued on Aug. 11, 2015, the disclosure of which is hereby incorporated by reference herein in its entirety. By way of example, suitable commercially available membrane include the EZ2090 polypropylene, microporous membrane from Celgard. Microporous membranes 332 and 334 may have 40-80% open area, pore sizes of less than 0.5 μm, and a thickness of less than 100 μm. Some example microporous membranes may have greater than 80% open area. One suitable membrane is approximately 65% open area and has a thickness of approximate 20 μm. This type of membrane is structurally very uniform in pore size and is thin enough to not create a significant thermal barrier. Other possible membranes include membranes from 3M, Lydall, and other manufacturers. The membranes 332 and 334 may include any suitable vapor-permeable material that permits water transfer therethrough to enable the liquid desiccant in the liquid desiccant channels 336 and 338 to absorb moisture from or desorb moisture into air flowing over the membranes 332 and 334.

The frame 302 defines a liquid desiccant inlet port 340 that feeds liquid desiccant into the liquid desiccant header area 320 and a liquid desiccant outlet port 342 that receives liquid desiccant from the liquid desiccant header area 322. The liquid desiccant inlet port 340 is defined in a first corner flange 364 of the frame 302. The first corner flange 364 of the frame 302 is part of the first header section 312 and is located adjacent to the liquid desiccant header area 320 at the first vertical end 304 and the second longitudinal end 310 of the panel assembly 300. The liquid desiccant outlet port 342 is defined in a second corner flange 366 of the frame 302. The second corner flange 366 is part of the second header section 314, and is located adjacent to the liquid desiccant header area 322 at the second vertical end 306 and the first longitudinal end 308 of the panel assembly 300. Thus, the first and second corner flanges 364 and 366, and the liquid desiccant inlet and outlet ports 340 and 342 respectively defined therein, are located on opposite longitudinal and vertical ends of the panel assembly 300.

As represented by the flow lines 344 in FIGS. 7 and 9, in an example operation of the three-way heat exchanger 200, liquid desiccant is supplied into the liquid desiccant header area 320 of the panel assembly 300 via the liquid desiccant inlet port 340, flows through each of the liquid desiccant channels 336 and 338 and into the liquid desiccant header area 322, and exits the panel assembly 300 via the liquid desiccant outlet port 342. In the illustrated example, the liquid desiccant flows vertically downward in the desiccant channels 336, 338. As such, the liquid desiccant flows across (or intersects) the airflow direction 278 (FIG. 2). The liquid desiccant also flows in the longitudinal direction, in the same longitudinal direction as the airflow direction 278, as a result of the liquid desiccant inlet port 340 being located at the first longitudinal end 308 of the frame 302 and the liquid desiccant outlet port 342 being located at the second longitudinal end 310. The liquid desiccant may have alternative flow horizontal and/or longitudinal directions. The flow direction(s) of the liquid desiccant in the channels 336, 338 may vary depending, for example, on the orientation of the panel assemblies 300 in the heat exchanger 200, location of the liquid desiccant inlet and outlet ports 340, 342, and/or to which liquid desiccant header area 320, 322 the liquid desiccant is supplied and from which header area the liquid desiccant exits.

The frame 302 also defines a heat transfer fluid inlet port 346 that feeds heat transfer fluid into the heat transfer fluid channel 330 and a heat transfer fluid outlet port 348 that receives heat transfer fluid from the heat transfer fluid channel 330. The heat transfer fluid inlet port 346 is defined in a third corner flange 368 of the frame 302. The third corner flange 368 of the frame 302 is part of the second header section 314 and the middle section 316. The third corner flange 368 is located adjacent to heat transfer fluid channel 330, at the second longitudinal end 310 and proximate to the second vertical end 306 of the panel assembly 300. The heat transfer fluid outlet port 348 is defined in a fourth corner flange 370 of the frame 302. The fourth corner flange 370 is part of the first header section 312 and the middle section 316. The fourth corner flange 370 is located adjacent to the heat transfer fluid channel 330, at the first longitudinal end 308 and proximate to the first vertical end 304 of the panel assembly 300. Thus, the third and fourth corner flanges 368 and 370, and the heat transfer fluid inlet and outlet ports 346 and 348 respectively defined therein, are located on opposite longitudinal and vertical ends of the panel assembly 300. Additionally, the first and fourth corner flanges 364 and 370, and the liquid desiccant inlet port 340 and the heat transfer fluid outlet port 348 respectively defined therein, are both located proximate to the first vertical end 304, on opposite longitudinal ends of the panel assembly. The second and third corner flanges 366 and 368, and the liquid desiccant outlet port 342 and the heat transfer fluid inlet port 346 respectively defined therein, are both located proximate to the second vertical end 306, on opposite longitudinal ends of the panel assembly.

As represented by the flow lines 350 in FIGS. 7 and 9, in an example operation of the three-way heat exchanger 200, heat transfer fluid is supplied into the heat transfer fluid channel 330 of the panel assembly 300 via the heat transfer fluid inlet port 346, flows therethrough, and exits the panel assembly 300 via the heat transfer fluid outlet port 348. In the illustrated example, the heat transfer fluid flows vertically upward in the channel 330. As such, the flow direction of the heat transfer fluid is across (or intersects) the airflow direction 278 (FIG. 2) and counter (or directionally opposite) to the flow of the liquid desiccant in the channels 336 and 338. The heat transfer fluid also flows in the longitudinal direction, counter (or directionally opposite) to the airflow direction 278, as a result of the heat transfer fluid inlet port 346 being located at the second longitudinal end 310 of the frame 302 and the heat transfer fluid outlet port 348 being located at the first longitudinal end 308. The heat transfer fluid may have alternative flow directions. The flow direction(s) of the heat transfer fluid in the channel 330 may vary depending, for example, on the orientation of the panel assemblies 300 in the heat exchanger 200, location of the heat transfer fluid inlet and outlet ports 346, 348, and/or through which port 346, 348 the heat transfer fluid enters the channel 330 and through which port the heat transfer fluid exits the channel 330.

As described further below, the flow guide 400 (shown, e.g., in FIG. 12) may be positioned in the heat transfer fluid channel 330 to control flow and/or distribution of the heat transfer fluid in the heat transfer fluid channel. The flow guide 400 may define one or more flow paths 402 that direct the heat transfer fluid as it flows through the channel 330. The flow path(s) 402 may include a series of passageways through which the heat transfer fluid flowing through the channel 330 is redirected. For example, where the heat transfer fluid flows as illustrated in FIGS. 7 and 9, that is, vertically upward through the channel 330 across the airflow direction 278 and horizontally opposite the airflow direction between the ports 346, 348, the flow guide 400 may redirect the heat transfer fluid through the flow path(s) 402 to facilitate controlling the heat transfer fluid from prematurely reaching an area of the heat transfer fluid channel 330 proximate the first longitudinal end 308 of the frame 302. The flow path(s) 402 may include a series of passageways that define a winding path (e.g., a serpentine shape) such that the heat transfer fluid winds (e.g., “snakes”) through the heat transfer fluid channel 330 without prematurely reaching the first longitudinal end 308. The flow guide 400 may also separate the flow path(s) 402 from a portion of the area of the heat transfer fluid channel 330 proximate the first longitudinal end 308 such that the heat transfer fluid is limited or restricted from flowing into those areas.

FIGS. 10A-10D are enlarged views of the sections A, B, C, D, respectively, of the frame 302 shown in FIG. 8, and depict the corner flanges 364-370 in greater detail. In particular, FIGS. 10A-10D show microchannels or apertures that provide fluid connection between the ports 340, 342, 346, and 348 and the respective fluid areas defined in the panel assembly 300. As shown in FIGS. 10A and 10B, the heat transfer fluid inlet port 346 is connected to the heat transfer fluid area 324 by apertures 352 (FIG. 10B) and the heat transfer fluid outlet port 348 is connected to the heat transfer fluid area 324 by apertures 354 (FIG. 10A). The heat transfer fluid area 324 defines the heat transfer fluid channel 330 when sealed on the opposite lateral faces 305 and 307 of the frame 302 by the plates 326 and 328. As indicated by the flow lines 350 in FIGS. 10A and 10B, heat transfer fluid enters the heat transfer fluid channel 330 from the inlet port 346 via the apertures 352 and exits the channel 330 into the outlet port 348 via the apertures 354.

As shown in FIGS. 10C and 10D, the liquid desiccant inlet port 340 is connected to the first liquid desiccant header area 320 by apertures 356 (FIG. 10C) and the liquid desiccant outlet port 342 is connected to the second liquid desiccant header area 322 by apertures 358 (FIG. 10D). As indicated by the flow lines 344 in FIGS. 10C and 10D, liquid desiccant enters the first liquid desiccant header area 320 from the inlet port 340 via the apertures 356, flows into and through the liquid desiccant channels 336 and 338 (FIG. 9), into the second liquid desiccant header area 322, and exits the header area 322 into the outlet port 342 via the apertures 358. In the illustrated example of FIGS. 10A-10D, each of the apertures 352-358 include two apertures. Any suitable number of apertures may be used for the apertures 352-358. In some examples, a greater number of apertures may be used for some of the apertures 352-358 than the other apertures 352-358. The number, size, and/or shape of the apertures 352-358 may be the same or different. The number of apertures, as well as the size and shape, used for each of the apertures 352-358 may also vary between panel assemblies 300.

FIGS. 10A-10D also show example features of the panel assembly 300 that may facilitate connecting adjacent panel assemblies 300 together when installed in the three-way heat exchanger 200. For example, when panel assemblies 300 are arranged in series and installed in the heat exchanger 200, the corner flanges 364-370 of the frames 302 of adjacent panel assemblies 300 may be connected. As shown, each corner flange 364-370 includes one or more snap fittings 372. The snap fittings 372 extend in the lateral direction from the first lateral face 305 of the frame 302, and a corresponding bore 374 (shown in FIG. 6) depends into the second lateral face 307 at the location laterally opposite the snap fitting 372. Each corner flange 364-370 includes two snap fittings 372 and corresponding bores 374 in the illustrated example. In other examples, more or fewer snap fittings 372 and corresponding bores 374 may be included at the corner flanges 364-370. The corner flanges 364-370 may include the same or a different number of snap fittings 372 and corresponding bores 374. Suitably, a corresponding bore 374 is included for each snap fitting 372 in each corner flange 364-370. When the panel assemblies 300 are arranged in series and installed in the heat exchanger 200, each snap fitting 372 of the corner flanges 364-370 of the frame 302 of one of the panel assemblies 300 is received by one of the corresponding bores 374 of the corner flanges 364-370 of the frame 302 of a laterally adjacent panel assembly 300 to directly connect adjacent panel assemblies 300.

Each corner flange 364-370 also includes one or more alignment holes 376 extending therethrough in the lateral direction. In the illustrated embodiment, the corner flanges 364-370 each include two alignment holes 376, labeled in FIGS. 10A-D as a first alignment hole 376a and a second alignment hole 376b. The first alignment holes 376a of each corner flange 364-370 are located longitudinally inboard of the second alignment holes 376b and adjacent to respective corners of the heat transfer fluid area 324. In other examples, more or fewer alignment holes 376 may be included at the corner flanges 364-370. The corner flanges 364-370 may include the same or a different number of alignment holes 376. When the panel assemblies are arranged in series and installed in the heat exchanger 200, the alignment holes 376 of the corner flanges 364-370 of the frames 302 of the panel assemblies 300 receive a corresponding clamping assembly (not shown) used to clamp the panel assemblies 300 together. The first alignment holes 376a of the panel assemblies 300 correspond to one of the alignment apertures 258 of the first end plate 218 and one of the alignment apertures 260 of the second end plate 220 (shown in FIGS. 2 and 4). The second alignment holes 376b receive a corresponding clamping assembly (not shown). The second alignment holes 376b do not correspond to alignment apertures 258 and 260 in the end plates 218 and 220, such that the clamping assemblies received by the second alignment holes 376b extend through the panel assemblies 300 but not the end plates 218 and 220.

Still referring to FIGS. 10A-10D, each of the corner flanges 364-370 includes flange collar 378 circumscribing the respective fluid port 340, 342, 346, 348 defined in the corner flange. The flange collars 378 extend in the lateral direction from the first lateral face 305 of the frame 302. Each corner flange 364-370 also includes a corresponding grooved mouth 380 that depends into the second lateral face 307 and circumscribes the respective fluid port 340, 342, 346, 348 at the location laterally opposite the flange collar 378. When the panel assemblies 300 are arranged in series and installed in the heat exchanger 200, each flange collar 378 of the corner flanges 364-370 of the frame 302 of one of the panel assemblies 300 is received by one of the corresponding grooved mouths 380 of the corner flanges 364-370 of the frame 302 of a laterally adjacent panel assembly 300 to directly connect adjacent panel assemblies 300. The flange collars 378 each include a set of piloting teeth 382 that facilitate aligning the flange collars 378 with the corresponding grooved mouths 380 and inserting the flange collars 378 therein. The piloting teeth 382 may include a piloting feature (e.g., a chamfer) for easier insertion of the teeth and the flange collar 378 into the corresponding grooved mouth 380. Elastomeric seals (not shown), such as an O-ring, may be seated within each of the grooved mouths 380 and to create a fluid-tight seal between the adjacent panel assemblies 300 at the adjacent fluid ports 340, 342, 346, 348 when the flange collars 378 are inserted into the grooved mouths 380.

With additional reference to FIGS. 3 and 5, and to FIG. 6 which shows a left elevation of the three-way heat exchanger 200 with various components omitted similar to FIGS. 3 and 5, the panel assemblies 300 are arranged in succession or series in the lateral direction as described above. In FIGS. 3, 5, and 6, the plates 326 and 328 and the membranes 332 and 334 are omitted for convenience of illustration. When assembled and installed in the three-way heat exchanger 200, for each pair of adjacent panel assemblies 300, the membrane 332 of one of the panel assemblies 300 faces the membrane 334 of the other one of the panel assemblies 300. The airflow gaps 216 are defined between the adjacent membranes 332 and 334. Each panel assembly 300 may have a reduced width over the middle section 316, such that the panel assemblies 300 are spaced apart over their adjacent middle sections 316 to define the airflow gaps 216. Additionally and/or alternatively, the airflow gaps 216 may be defined and maintained by standoffs or spacers 386 between the middle sections 316 of adjacent panel assemblies 300. The standoffs or spacers 386 extend in the lateral direction outward from the middle section 316 proximate the longitudinal ends 308 and 310. The middle section 316 of each frame 302 may additionally and/or alternatively include the snap fittings 372 and the corresponding bores 374 (as shown in FIGS. 6 and 7) proximate the longitudinal ends 308 and 310. The snap fittings 372 and corresponding bores 374 located on the middle section 316 of the frame 302 may facilitate connecting adjacent panel assemblies 300 at the adjacent middle sections. The snap fittings 372 and corresponding bores 374 may be included in addition to the spacers 386. Alternatively, the spacers 386 may in some examples be the snap fittings 372 which engage the bores 374 of the adjacent panel assembly 300 to connect the adjacent panel assemblies and maintain the width of the airflow gaps 216.

The panel assemblies 300 are arranged in the three-way heat exchanger 200 such that, for each panel assembly, the first and second lateral faces 305 and 307 of the frame 302 are respectively oriented toward the first and second lateral sides 202 and 204 of the three-way heat exchanger 200. The first and second longitudinal ends 308 and 310 are respectively located at the first and second longitudinal sides 206 and 208 of the three-way heat exchanger 200, and the first and second vertical ends 304 and 306 are respectively located at the first and second vertical sides 210 and 212 of the three-way heat exchanger 200.

The ports 340, 342, 346, and 348 of the panel assemblies 300 align to define respective manifolds of the three-way heat exchanger 200 extending in the lateral direction through which heat transfer fluid and liquid desiccant flow to and from the panel assemblies 300 between the first and second lateral sides 202 and 204. The liquid desiccant inlet ports 340 of the panel assemblies 300 align to form a liquid desiccant inlet manifold 242 that extends between the first and second lateral sides 202 and 204 proximate to the first vertical side 210 and the second longitudinal side 208 of the three-way heat exchanger 200. The liquid desiccant outlet ports 342 of the panel assemblies 300 align to form a liquid desiccant outlet manifold 244 that extends between the first and second lateral sides 202 and 204 proximate to the second vertical side 212 and the first longitudinal side 206 of the three-way heat exchanger 200. The heat transfer fluid inlet ports 346 of the panel assemblies 300 align to form a heat transfer fluid inlet manifold 246 that extends between the first and second lateral sides 202 and 204 proximate to the second vertical side 212 and the second longitudinal side 208 of the three-way heat exchanger 200. The heat transfer fluid outlet ports 348 of the panel assemblies 300 align to form a heat transfer fluid outlet manifold 248 that extends between the first and second lateral sides 202 and 204 proximate to the first vertical side 210 and the first longitudinal side 206 of the three-way heat exchanger 200.

The panel assemblies 300 may include O-rings or other elastomeric scaling members that form liquid-tight seals between the aligning ports 340, 342, 346, and 348 of the adjacent panel assemblies to prevent fluid from leaking out of the respective manifolds 242-248. For example, as described above, elastomeric seals (not shown), such as an O-ring, may be seated within each of the grooved mouths 380 and to create a fluid-tight seal between the adjacent panel assemblies 300 at the adjacent fluid ports 340, 342, 346, 348 when the flange collars 378 are inserted into the grooved mouths 380. In some examples, the elastomeric seals 384 are radial seals (e.g., radial O-ring seals). Moreover, in each of the corner flanges 364-370, the snap fittings 372, corresponding bores 374, and the alignment holes 376 collectively surround the fluid port 340, 342, 346, 348 defined in the corner flange, which may facilitate creating and maintaining a fluid-tight seal between the adjacent ports 340, 342, 346, 348 that define the manifolds 242-248.

As shown in FIGS. 3 and 5, conduits 250, 252, 254, and 256 are used to fluidly connect the heat transfer fluid inlet 232 and outlet 234 and the liquid desiccant inlet 236 and outlet 238 to a respective manifold for heat transfer fluid and liquid desiccant entering and exiting the three-way heat exchanger 200. The liquid desiccant inlet 236 is fluidly connected to the liquid desiccant inlet manifold 242 by the conduit 250. The liquid desiccant outlet 238 is fluidly connected to the liquid desiccant outlet manifold 244 by the conduit 252. The heat transfer fluid inlet 232 is fluidly connected to the heat transfer fluid inlet manifold 246 by the conduit 254. The heat transfer fluid outlet 234 is fluidly connected to the heat transfer fluid outlet manifold 248 by the conduit 256. The conduits 250-256 may include any suitable fluid conduit (rigid and/or flexible) that enables heat transfer fluid and liquid desiccant to flow between the respective inlet and outlet and manifold, including, for example and without limitation, pipes, hoses, tubes, and combinations thereof. Each conduit 250-256 may be attached to the respective manifold 242-248 by coupling an end of the conduit to an end panel assembly 300 (i.e., the panel assembly 300 immediately adjacent to the lateral side 202 or 204) at the appropriate one of the ports 340, 342, 346, and 348. The conduits 250-256 may be attached to the appropriate port 340, 342, 346, and 348 of an end panel assembly 300 using any suitable means, include fasteners, threads, clamps, and the like.

The conduits 250 and 256 extend between the end plate 218 and the end panel assembly 300 at the first lateral side 202. The conduits 252 and 254 extend between the end plate 220 and the end panel assembly 300 at the second lateral side 204. The conduits 250 and 256 may extend through the end plate 218 to respectively define the inlet 236 or the outlet 234, may be coupled to the respective inlet 236 or outlet 234 that is defined by the end plate 218, or may be made integral with the end plate 218 and the respective inlet 236 or outlet 234 defined by the end plate 218. The conduits 252 and 254 may extend through the end plate 220 to respectively define the outlet 238 or the inlet 232, may be coupled to the respective outlet 238 or inlet 232 that is defined by the end plate 220, or may be made integral with the end plate 220 and the respective outlet 238 or inlet 232 defined by the end plate 220.

Each of the manifolds 242-248 may be closed at the lateral side 202 or 204 of the heat exchanger 200 opposite of the inlet or outlet to which the manifold is connected. The liquid desiccant inlet manifold 242 may be closed at the second lateral side 204, the liquid desiccant outlet manifold 244 may be closed at the first lateral side 202 opposite the liquid desiccant inlet manifold 242, the heat transfer fluid inlet manifold 246 may be closed at the first lateral side 202, and the heat transfer fluid outlet manifold 248 may be closed at the second lateral side 204 opposite the heat transfer fluid inlet manifold 246. The manifolds 242-248 may be closed at the respective lateral sides 202 or 204 by the end plate 218 or 220 (shown in FIGS. 2 and 4). In particular, the end plate 218 may plug the ports 342 and 346 of the panel assembly 300 at the end of the panel assemblies 300 that is adjacent to the first lateral side 202 to close the manifolds 244 and 246 at the first lateral side 202. The end plate 220 may plug the ports 340 and 348 of the panel assembly 300 at the end of the panel assemblies 300 that is adjacent to the second lateral side 204 to close the manifolds 244 and 246 at the second lateral side 204. Additionally and/or alternatively, end caps or plugs 272 and 274 (see FIG. 11) may be inserted into or otherwise disposed over the ports 342 and 346, respectively, of the panel assembly 300 adjacent to the first lateral side 202 to close the manifolds 244 and 246 at the first lateral side 202, and end caps or plugs 270 and 276 (see FIG. 11) may be inserted into or otherwise disposed over the ports 340 and 348, respectively, of the panel assembly 300 adjacent to the second lateral side 204 to close the manifolds 244 and 246 at the second lateral side 204.

Referring now to FIG. 11, operation of the three-way heat exchanger 200 will now be described. FIG. 11 is a schematic showing an interior view of the three-way heat exchanger 200 to depict flow of liquid desiccant and the heat transfer fluid through the manifolds 242-248 and the panel assemblies 300. In the schematic of FIG. 11, panel assemblies 300 are depicted with features exaggerated and/or simplified for convenience of illustration and description.

In an example operation of the heat exchanger 200, an inlet air stream (e.g., the first or second inlet air stream 110 or 114 shown in FIG. 1) enters via the airflow inlet 224 and flows through the air gaps 216 defined between adjacent panel assemblies 300 in the airflow direction 278. The air flowing through the air gaps 216 is treated by liquid desiccant, indicated by the flow lines 344, and heat transfer fluid, indicated by the flow lines 350, that are channeled through each of the panel assemblies 300. In some operations, the liquid desiccant 344 is concentrated liquid desiccant 152 from the liquid desiccant circuit 108 and the heat transfer fluid 350 is conditioner heat transfer fluid from the conditioner sub-system 104 shown in FIG. 1, and the heat exchanger 200 is used to cool and dehumidify the air flowing through the air gaps 216. In other operations, the liquid desiccant 344 is diluted liquid desiccant 154 from the liquid desiccant circuit 108 and the heat transfer fluid 350 is regenerator heat transfer fluid from the regenerator sub-system 106 shown in FIG. 1, and the heat exchanger 200 is used to heat and reject moisture into the air flowing through the air gaps 216.

The liquid desiccant 344 flows into the liquid desiccant inlet manifold 242 from the first lateral side 202, via the liquid desiccant inlet 236 and the conduit 250 (shown in FIGS. 3-5). The liquid desiccant 344 enters into the liquid desiccant header area 320 of each panel assembly 300 from the liquid desiccant inlet manifold 242 via the apertures 356. In each panel assembly 300, the liquid desiccant 344 flows from the liquid desiccant header area 320, into the liquid desiccant channels 336 and 338 via the apertures 360 on each plate 326 and 328 (shown in FIGS. 7 and 8), downward through the liquid desiccant channels 336 and 338, and into the liquid desiccant header area 322 via the apertures 362 on each plate 326 and 328 (shown in FIGS. 7 and 8). As the liquid desiccant 344 flows behind the membranes 332 and 334 of the panel assemblies 300, the liquid desiccant 344 absorbs moisture from or desorbs moisture into the air flowing through the air gaps 216 adjacent to the membranes 332 and 334. Moisture is permitted to permeate through each of the membranes 332 and 334 to enable the moisture to transfer between the liquid desiccant 344 and air in the air gaps 216. The liquid desiccant 344, having absorbed or desorbed moisture, exits each panel assembly 300 from the respective liquid desiccant header area 322 via the apertures 358, and flows through the liquid desiccant outlet manifold 244 toward the second lateral side 204. The liquid desiccant 344 exits the heat exchanger 200 via the conduit 252 and the liquid desiccant outlet 238 (shown in FIG. 5).

The heat transfer fluid 350 flows into the heat transfer fluid inlet manifold 246 from the second lateral side 204, via the heat transfer fluid inlet 232 and the conduit 254 (shown in FIGS. 4 and 5). The heat transfer fluid 350 enters into each panel assembly 300 from the heat transfer fluid inlet manifold 246 via the apertures 352. In each panel assembly 300, the heat transfer fluid 350 flows upward through the heat transfer fluid channel 330. The heat transfer fluid 350 flowing through the channel 330 is in thermal communication with the liquid desiccant 344 flowing through the liquid desiccant channels 336 and 338. Heat is transferred between the heat transfer fluid 350 and the liquid desiccant 344 to remove heat from or reject heat into the air flowing through the air gaps 216, depending on the operating mode of the heat exchanger 200. The heat transfer fluid 350, having absorbed or rejected heat, exits each panel assembly 300 via the apertures 354, and flows through the heat transfer fluid outlet manifold 248 toward the first lateral side 202. The heat transfer fluid 350 exits the heat exchanger 200 via the conduit 256 and the heat transfer fluid outlet 234 (shown in FIGS. 3-5).

The direction of flow of the heat transfer fluid 350 and the liquid desiccant 344 in the illustrated embodiment is by way of example only, and may change in other embodiments of the heat exchanger 200. For example, the liquid desiccant 344 may flow upward through the desiccant channels 336 and 338 on the panel assemblies 300. In these examples, the direction of flow of the liquid desiccant 344 through the liquid desiccant inlet 236 and outlet 238 and the liquid desiccant inlet and outlet manifolds 242 and 244 would also be reversed. The heat transfer fluid 350 may flow downward through the heat transfer channels 330 of the panel assemblies 300. In these examples, the direction of flow of the heat transfer fluid 350 through the heat transfer fluid inlet and outlets 232 and 234 and the heat transfer fluid inlet and outlet manifolds 246 and 248 would also be reversed. The liquid desiccant 344 and the heat transfer fluid 350 flow in counter-flow relation in the illustrated example, but may flow in the same direction through the panel assemblies in alternative examples.

Referring now to FIGS. 12-16, one, some, or all the panel assemblies 300 may include the flow guide 400 positioned in the heat transfer fluid channel 330 between the plates 326, 328. FIG. 12 is a perspective of the example flow guide 400 shown positioned in the heat transfer fluid area 324 defined by the frame 302. FIGS. 13 and 14 are right and left side elevations, respectively, of the frame 302 and the flow guide 400. FIG. 15 is an exploded view of the frame 302 and the flow guide 400. FIG. 16A is an isolated perspective of the flow guide 400, and FIGS. 16B-E are various magnified views of portions of the flow guide 400. When the panel assembly 300 is assembled and includes the flow guide 400, the plates 326 and 328 are attached to the frame 302 as described above such that the flow guide 400 is positioned in the heat transfer fluid channel 330 defined between the plates 326 and 328. The flow guide 400 defines one or more flow paths 402 (two flow paths 402a and 402b in the illustrated example) that control flow of the heat transfer fluid through the heat transfer fluid channel 330, described in more detail below. The flow guide 400 may be positioned in the heat transfer fluid area 324 without directly connecting or attaching the flow guide 400 to the frame 302. In this way, during operation, the flow guide 400 may be able to “float” in heat transfer fluid flowing through the heat transfer fluid channel 330.

The flow guide 400 includes a main body 404 that is formed as a panel or sheet. The main body 404 may also referred to as a sheet body 404. The sheet body 404 is made of a suitable structural material to enable the flow guide to function as described. In use, the flow guide 400 is immersed in heat transfer fluid (e.g., water, a glycol-based fluid, or any combination thereof) and may suitably be made of a polymer material that provides structure to the sheet body 404 and facilitates limiting chemical interactions between the flow guide 400 and the heat transfer fluid. For example, the sheet body 404 may include PETG. Additionally and/or alternatively, the sheet body 404 may include the same polymer material as the plates (e.g., polyolefins, ABS, or combinations thereof). The material used for the sheet body 404 may also be suitable or conducive for forming the flow guide 400 as a one-piece unit, with features (e.g., the sheet body 404, cut-outs 406, baffles 408, flow restrictor 410, alignment cut-outs 416, protrusions 418, and/or dimples 420) of the flow guide 400 being made integrally from one material. For example, the flow guide 400 may be made as a one-piece unit from a polymer material such as PETG. The flow guide 400 may be made as a one-piece unit using, for example, vacuum forming or any other suitable thermoforming technique.

The sheet body 404 is sized and shaped to substantially span the heat transfer fluid area 324. In the illustrated example, in which two plates 326 and 328 and two membranes 332 and 334 are attached to the lateral faces 305 and 307 of the frame 302, the sheet body 404 partitions or separates the heat transfer fluid area 324 into a first heat transfer fluid area 324a (FIGS. 12 and 13) and a second heat transfer fluid area 324b (FIG. 14). When the plates 326 and 328 are attached to the frame 302, the first heat transfer fluid area 324a defines a first portion of the heat transfer fluid channel 330 between the sheet body 404 and the plate 326, and the second heat transfer fluid area 324b defines a second portion of the heat transfer fluid channel 330 between the sheet body 404 and the plate 328. The sheet body 404 may be substantially non-porous such that the sheet body 404 limits or restricts the heat transfer fluid from flowing therethrough between the first portion and second portions of the heat transfer fluid channel 330. Alternatively, the sheet body 404 may include pores or other openings that allow flow of the heat transfer fluid channel between the first portion and second portions of the heat transfer fluid channel 330.

The sheet body 404 is sized, shaped, and positioned in the heat transfer fluid channel 330 to enable the heat transfer fluid entering from the heat transfer fluid inlet port 346 via the apertures 352 (FIG. 10B) to flow into both portions of the heat transfer fluid channel 330 and subsequently exit from both portions of the heat transfer fluid channel 330 into the outlet port 348 via the apertures 354 (FIG. 10A). In the illustrated example, the flow guide 400 includes two cut-outs 406a and 406b defined at longitudinally and vertically opposite corners of the sheet body 404, relative to the orientation of the flow guide 400 when positioned in the heat transfer fluid area 324. As such, when the flow guide 400 is positioned in the heat transfer fluid area 324, a first cut-out 406a is located proximate the heat transfer fluid inlet port 346 and a second cut-out 406b is located proximate the heat transfer fluid outlet port 348. The cut-outs 406 define areas in the heat transfer fluid channel 330 that are not partitioned into separate portions by the sheet body 404. The heat transfer fluid entering the heat transfer fluid channel 330 from the inlet port 346 first flows into the area defined by the first cut-out 406a. The heat transfer fluid then flows into both portions of the heat transfer fluid channel 330, on both sides of the flow guide 400. Flow of the heat transfer fluid on both sides of the flow guide 400 may be facilitated by alternating dimples 420 on the sheet body 404 that correspond to alternating protrusions 418 (shown, e.g., in FIG. 16E), described further below. The heat transfer fluid flows through both portions of the heat transfer fluid channel, directed by the flow paths 402a and 402b on both sides of the sheet body 404, towards the second cut-out 406b. The heat transfer fluid then flows into the area defined by the second cut-out 406b, and subsequently exits the heat transfer fluid channel 330 into the outlet port 348 via the apertures 354.

In the illustrated example, the flow guide 400 is used in the panel assembly 300 in which two plates 326 and 328 and two membranes 332 and 334 are attached to the lateral faces 305 and 307 of the frame 302. In this example, as described above, the sheet body 404 suitably partitions or separates the heat transfer fluid area 324 into the first heat transfer fluid area 324a (FIGS. 12 and 13) and the second heat transfer fluid area 324b (FIG. 14), and defines the flow paths 402a and 402b in both portions of the heat transfer fluid channel 330. The heat transfer fluid in the flow path 402a may primarily exchange heat with the liquid desiccant flowing between the membrane 332 and the plate 326 and the air stream flowing adjacent the membrane 332. The heat transfer fluid in the flow path 402b may primarily exchange heat with the liquid desiccant flowing between the membrane 334 and the plate 328 and the air stream flowing adjacent the membrane 334. In other examples, some or all the panel assemblies 300 may include one membrane (e.g., one of the membranes 332 or 334) and one desiccant channel 336 or 338. In such examples, it may not be necessary for the flow guide 400 to partition the heat transfer fluid channel 330 into two portions, and instead the flow guide 400 may define a single flow path 402 on one side of the sheet body 404, adjacent the one desiccant channel 336 or 338.

The flow guide 400 also includes baffles 408 on both sides of the sheet body 404. The baffles 408 define the flow paths 402a and 402b, which are indicated by flow lines in FIGS. 12-14. Each flow path 402a and 402b includes a series of passageways in the heat transfer fluid channel 330. Adjacent passageways are partially separated by the baffles 408, and connect end-to-end to form the flow paths 402a and 402b. The baffles 408 operate to direct the heat transfer fluid 330 through the flow paths 402a and 402b. In the illustrated embodiment, each baffle 408 is located at complementing positions on both sides of the sheet body 404, such that the flow paths 402a and 402b complement each other in shape and in number of passageways. The baffles 408 and the sheet body 404 may be made integrally from one material (e.g., a polymer material such as PETG). The baffles 408 and the sheet body 404 may be made integrally from one material using vacuum forming or another suitable thermoforming technique. Referring to the magnified section of the flow guide 400 shown in FIG. 16C, the baffles 408 have an “S” or “sine wave” profile such that each baffle 408 is on both sides of the sheet body 404 at complementing locations.

In the example flow guide 400, two baffles 408 are located on each side of the sheet body 404, defining three passageways of the flow paths 402a and 402b. More or fewer baffles 408 may be included. The number of baffles 408 may vary depending, for example, on the desired number of passageways of the flow paths 402a and 402b. The baffles 408 may be suitably spaced depending, for example, on the number of baffles 408 and/or a desired dimension of each passageway of the flow paths 402a and 402b. The baffles 408 may be arranged on the sheet body 404 such that the passageways of the flow paths 402a and 402b may have the same or different dimensions. When the flow guide 400 is positioned in the heat transfer fluid area 324, the baffles 408 may have any suitable orientation to enable the flow guide 400 to function as described. For example, the location and orientation of the baffles 408 may vary depending on a desired shape of the flow paths 402a and 402b and direction of flow of the heat transfer fluid.

In the example flow guide 400, each baffle 408 extends vertically on the sheet body 404, relative to the orientation of the flow guide 400 when positioned in the heat transfer fluid area 324. The baffles 408 are spaced longitudinally from each other and a passageway of the flow path 402a or 402b is defined on each side of each baffle 408. Each baffle 408 extends from one vertical end of the sheet body 404 and terminates prior to the other vertical end. The vertical end of the sheet body 404 from which a baffle 408 extends alternates between adjacent baffles. As such, the passageways defined by the baffles 408 each extend vertically and adjacent passageways connect horizontally in the longitudinal direction, forming a winding path (e.g., the serpentine shape of the flow paths 402a and 402b shown in FIGS. 12-14). The baffles 408 redirect the heat transfer fluid through the flow paths 402a and 402b such that the heat transfer fluid winds or “snakes” through the heat transfer fluid channel 330, flowing in alternating vertical directions, and ultimately vertically upward and longitudinally between the heat transfer fluid inlet port 346 and the outlet port 348.

As described above, in an example operation of the three-way heat exchanger 200, the heat transfer fluid flows in the heat transfer fluid channel 330 vertically across (or intersects) the airflow direction 278 (FIG. 2) and longitudinally counter (or longitudinally opposite) to the airflow direction 278. The flow guide 400 facilitates controlling the heat transfer fluid from prematurely reaching an area of the heat transfer fluid channel 330 proximate the first longitudinal end 308 of the frame 302. FIG. 17 is a schematic of free or “uncontrolled” flow of the heat transfer fluid (represented by the flow line 350a) in the heat transfer fluid channel 330, that is, in the absence of a flow guide 400. As shown, the free or uncontrolled flow of heat transfer fluid 350a distributes horizontally (longitudinally) and vertically across the heat transfer fluid channel 330 as the heat transfer fluid 350a flows from the heat transfer fluid inlet port 346 to the outlet port 348. When uncontrolled, the heat transfer fluid 350a entering the heat transfer fluid channel 330 may initially have the propensity to flow horizontally toward the first longitudinal end 308 of the frame 302, before flowing vertically upward toward the outlet port 348 proximate the first vertical end 304. An example of this tendency is shown in FIG. 18, which is an example time lapse of heat signatures of a panel assembly 300 in an operation without the flow guide 400 and shows cold heat transfer fluid flowing initially toward the first longitudinal end 308 of the panel assembly. The flow of the heat transfer fluid in FIG. 18 is from the bottom left to the top right of the panel assembly 300.

The propensity for the heat transfer fluid to initially flow toward the first longitudinal end 308 when uncontrolled may negatively impact performance of the three-way heat exchanger 200 as it creates a relatively high temperature differential between the heat transfer fluid 350a and the air stream (e.g., the first or second inlet air stream 110 or 114 in FIG. 1) at localized regions of the panel assemblies 300 (e.g., proximate the first longitudinal end 308 and the second vertical end 306). For example, the localized, high temperature differential regions of the panel assemblies 300 may degrade overall performance and/or efficiency of the three-way heat exchanger 200 as the heat transfer between the air stream and the heat transfer fluid is not uniform across the panel assemblies 300. In addition, when the three-way heat exchanger 200 is used to condition hot, humid air, the relatively high temperature differential at these localized regions may result in a large amount of moisture condensing on the membranes 332, 334. Condensation can result when the temperature within the three-way heat exchanger 200 is below the dew point temperature of the air stream flowing therethrough. The probability of condensation can be estimated by comparing the temperature of the heat transfer fluid within the panel assemblies 300 to the dew point temperature of the air stream flowing through the airflow gaps 216-a dew point temperature significantly higher than the adjacent coolant temperature would indicate a high probability of condensation forming within the heat exchanger 200. FIG. 19 is a modeled comparison of the dew point temperature of an air stream (left image) flowing through the airflow gaps 216 and the temperature of heat transfer fluid (right image) flowing free or uncontrolled (without a flow guide 400) through a panel assembly 300. As shown in FIG. 19, there are localized regions proximate the bottom of the heat transfer fluid channel 330 (where the uncontrolled heat transfer fluid has the propensity to flow horizontally counter the airflow direction 278) at which the temperature of the heat transfer fluid may be significantly below the dew point temperature of the air stream, increasing the probability of condensation forming on the membranes 332, 334 adjacent these regions. Such condensation on the membranes 332, 334 may negatively affect the performance of the heat exchanger 200, for example, by reducing effective mass transfer between the air stream and the liquid desiccant, restricting air flow, increasing pressure drop through the airflow gaps 216, and increasing moisture build up in and around the panel assemblies 300.

The flow guide 400 suitably operates to control flow and/or distribution of the heat transfer fluid in the heat transfer fluid channel 330 through the flow paths 402a and 402b, using the baffles 408, to prevent the heat transfer fluid from prematurely reaching the area of the channel 330 proximate the first longitudinal end 308 of the frame 302. FIG. 20 is a schematic of “controlled” flow of the heat transfer fluid (represented by the flow line 350b) in the heat transfer fluid channel 330 using the flow guide 400, where the heat transfer fluid 350b flows through the flow channels 402a and 402b (FIGS. 12-14) defined by the baffles 408. As shown, the controlled flow of heat transfer fluid 350b winds or snakes through the flow paths 402a and 402b, intersecting the airflow direction 278 through each vertical passageway as the heat transfer fluid 350b flows from the heat transfer fluid inlet port 346 to the outlet port 348. The baffles 408 facilitate eliminating the propensity of the heat transfer fluid to flow initially horizontally toward the first longitudinal end 308 of the frame 302, which in turn eliminates the disadvantages of the uncontrolled heat transfer fluid flow described above with reference to FIGS. 17-19. FIG. 22 is an example time lapse of heat signatures of a panel assembly 300 in an example operation when the flow guide 400 is used and shows controlled flow of cold heat transfer fluid through the heat transfer fluid channel 330 (from the bottom left to the top right pf the panel assembly). As compared to the heat signatures shown in FIG. 18, the heat signatures in FIG. 22 show that the flow guide 400 facilitates a more evenly distributed and well-controlled temperature differential between the air stream and the heat transfer fluid across the panel assembly 300. FIG. 23 is a modeled comparison of the dew point temperature of an air stream (left image) flowing through the airflow gaps 216 and the temperature of heat transfer fluid (right image) with controlled flow facilitated by the flow guide 400 through a panel assembly 300. As shown in FIG. 23, compared to FIG. 19, the existence of localized regions at which the temperature of the heat transfer fluid is significantly below the dew point temperature of the air stream is greatly reduced or eliminated when the flow of the heat transfer fluid is controlled as shown in FIG. 20. Thus, the flow guide 400 suitably operates to significantly decrease the probability of condensation forming within the three-way heat exchanger 200.

Referring again to FIGS. 12-16, and with additional reference to the schematic of FIG. 21, the flow guide 400 may also include a flow restrictor 410 that is located on the sheet body 404 proximate the first longitudinal end 308 when the flow guide 400 is positioned in the heat transfer fluid area 324. The flow restrictor 410 operates to restrict or limit the heat transfer fluid from entering an area of the heat transfer fluid channel 330 proximate the first longitudinal end 308. This “restricted area” is indicated at 412 in FIG. 21. The flow restrictor 410 may, similar to the baffles 408, be located at complementing positions on both sides of the sheet body 404, such that the flow restrictor 410 separates the flow path 402a from a restricted area 412a (FIGS. 12 and 13) in the first portion of the heat transfer fluid channel 330 and separates the flow path 402b from a restricted area 412b (FIG. 14) in the second portion of the heat transfer fluid channel 330. For example, the flow restrictor 410, the baffles 408, and the sheet body 404 may be made integrally from one material (e.g., a polymer material such as PETG), using, for example, vacuum forming or another suitable thermoforming technique. The flow restrictor 410 may have the “S” or “sine wave” profile similar to the baffle 408 shown in FIG. 16C such that the flow restrictor 410 is on both sides of the sheet body 404 at complementing locations.

In the example flow guide 400, the flow restrictor 410 extends vertically and horizontally (longitudinally) on the sheet body 404, relative to the orientation of the flow guide 400 when positioned in the heat transfer fluid area 324. The flow restrictor 410 is spaced longitudinally from one of the baffles 408 and a passageway of the flow path 402a or 402b is defined therebetween. The flow restrictor 410 extends from one vertical end of the sheet body 404, proximate the second vertical end 306 of the frame 302, and terminates vertically prior to the other vertical end (proximate the outlet port 348) and extends horizontally toward the first longitudinal end 308 to define the restricted areas 412a and 412b separated from the flow paths 402a and 402b. The flow restrictor 410 has an “L” shape in the illustrated example but may have other shapes to enable the flow restrictor to function as described. As the heat transfer fluid (represented by the flow line 350c in FIG. 21) winds or “snakes” through the flow paths 402a and 402b, between the heat transfer fluid inlet port 346 and the outlet port 348, the flow restrictor 410 operates to prevent the heat transfer fluid from reaching the restricted areas 412a and 412b of the channel 330 proximate the first longitudinal end 308 of the frame 302. As a result, the flow restrictor 410 may further prevent condensation with the three-way heat exchanger 200 by reducing or eliminating the existence of localized regions at which the temperature of the heat transfer fluid is significantly below the dew point temperature of the air stream.

The flow guide 400 may be sized such that a clearance 414 (shown in FIGS. 13, 20, and 21) is defined between a top vertical end of the sheet body 404 and the topmost portion of the heat transfer fluid channel 330 when the flow guide 400 is positioned therein. The clearance 414 is defined above one or more baffles 408 located at the vertical end of the sheet body 404, and the clearance is connected to one or more of the passageways of the flow paths 402a and 402b. The heat transfer fluid may contain entrained air bubbles, which limit or impede vertically downward flow of the heat transfer fluid in the flow paths 402a and 402b. The clearance 414 facilitates capturing entrained air from the flow of the heat transfer fluid, allowing the air to pass therethrough while the heat transfer fluid is directed vertically downward through the connected passageway(s) of the flow paths 402a and 402b. Suitably, the clearance 414 is sized to capture entrained air while limiting or preventing the heat transfer fluid from flowing therethrough and bypassing the connected passageway(s) of the flow paths 402a and 402b.

As described above, the flow guide 400 may be positioned within the heat transfer fluid area 324 of the frame 302 without directly attaching the flow guide to the frame, such that the flow guide is able to float in the heat transfer fluid channel 330. Suitably, the flow guide 400 includes one or more alignment features 416 that complement a corresponding alignment feature 388 of the frame 302 for positioning and orienting the flow guide 400 in the heat transfer fluid area 324. The corresponding alignment features 388 and 416 may ensure that the baffles 408 and the flow restrictor 410 are properly oriented to function as described. In the illustrated example of FIGS. 12-16, the sheet body 404 includes an alignment cut-out 416 that complements an alignment tab 388 located on the frame 302. The alignment tab 388 extends longitudinally into the heat transfer fluid area 324 proximate the first longitudinal end 308, and is received by the alignment cut-out 416 of the flow guide 400 when properly positioned and oriented. In other examples, the alignment features 388 and 416 may have any suitable location on the frame 302 and the flow guide 400, respectively, to facilitate positioning and orienting the flow guide in the heat transfer fluid area 324.

Referring to FIG. 16, the flow guide 400 also includes protrusions 418 on both sides of the sheet body 404. The protrusions 418 and the sheet body 404 (as well as the baffles 408 and/or the flow restrictor 410) may be made integrally from one material (e.g., a polymer material such as PETG). For example, the protrusions 418 and the sheet body 404 may be made integrally from one material using vacuum forming or another suitable thermoforming technique. Each protrusion 418 on one side of the sheet body 404 has a corresponding dimple 420 on the other side of the sheet body. The protrusions 418 are arranged such that each side of the sheet body 404 has alternating protrusions 418 and dimples 420.

In an example operation of the three-way heat exchanger 200, the flow rate of the heat transfer fluid may be such that the heat transfer fluid channel 330 is at negative pressure (e.g., below atmospheric pressure). This may create the opportunity for the plates 326, 328 to “collapse” inward, which restricts or impedes flow of the heat transfer fluid through the panel assembly 300. The protrusions 418 extend from the sheet body 404 a suitable width to facilitate maintaining a width of the heat transfer fluid channel 330, measured between the plates 326, 328. In particular, the protrusions 418 facilitate maintaining the width of the heat transfer fluid channel 330 by reducing or eliminating the propensity of the plates 326, 328 to collapse inward when the heat transfer fluid is flowed through the heat transfer fluid channel at a negative pressure (e.g., below atmospheric pressure). The protrusions 418 and the corresponding dimples 420 may additionally and/or alternatively facilitate constant flow rates of the heat transfer fluid through the channel 330, and/or provide turbulation of the heat transfer fluid to increase heat transfer with the liquid desiccant and air flowing over the outer surfaces of the plates 326 and 328.

As shown in the magnified view of FIG. 16E, the first cut-out 406a of the flow guide 400, which is located adjacent the inlet port 346 when the flow guide is positioned in the heat transfer fluid channel 330, may be located on the sheet body 404 such that some of the protrusions 418 and dimples 420 are partially cut off. The first cut-out 406a and the cut off protrusions 418 and dimples 420 may create a suitable contour of the sheet body 404 at the first cut-out 406a to guide the heat transfer fluid entering the heat transfer fluid channel 330 to flow on each side of the sheet body 404. In particular, the cut off protrusions 418 and dimples 420 may define discrete inlets for the heat transfer fluid entering the heat transfer fluid channel 330 from the inlet port 346 to flow into both portions of the heat transfer fluid channel 330, on both sides of the flow guide 400.

Example HVAC systems described include one or more three-way heat exchangers for removing heat and moisture from a flow of air and/or rejecting heat and moisture into a flow of air. An example three-way heat exchanger includes panel assemblies arranged in series and defining air gaps for air to flow therebetween. Heat transfer fluid and liquid desiccant are channeled through manifolds to each panel assembly to treat the air flowing through the air gaps. The operational efficiency and lifetime of the three-way heat exchanger is improved by a flow guide positioned in a heat transfer fluid channel of one, some, or all the panel assemblies. The flow guide facilitates controlling flow and/or distribution of the heat transfer fluid being channeled through the panel assemblies. The flow guide may direct the heat transfer fluid to flow along controlled flow paths that prevent the heat transfer fluid from prematurely reaching areas of the heat transfer fluid channel where a significant temperature differential between the heat transfer fluid and the air may otherwise exists. This facilitates reducing the propensity for heat transfer to concentrate at localized regions of the panel assemblies, which may degrade overall performance and/or efficiency of the three-way heat exchanger. Additionally and/or alternatively, the controlled flow of the heat transfer fluid facilitated by the flow guide may reduce or eliminate the propensity for large amounts of moisture to condense within the heat exchanger which otherwise would negatively impact performance and/or efficiency of the heat exchanger. Additional technical benefits that may be provided by the flow guide include, but are not limited to including, maintaining a width of the heat transfer fluid channel under negative pressure, facilitating constant flow rates of the heat transfer fluid through the panel assembly, providing turbulation of the heat transfer fluid to increase heat transfer with the liquid desiccant and air, and/or improving manufacturability of the flow guide which may be made as a one-piece unit from a single material.

Example embodiments of HVAC systems and methods of operating the systems are described above in detail. The systems and methods are not limited to the specific embodiments described herein, but rather, components of the system and methods may be used independently and separately from other components described herein. For example, the systems described herein may be used in systems other than HVAC systems.

When introducing elements of the present disclosure or the embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” “containing” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. The use of terms indicating a particular orientation (e.g., “top”, “bottom”, “side”, “vertical”, “lateral”, “longitudinal”, etc.) is for convenience of description and does not require any particular orientation of the item described.

The terms “about,” “substantially,” “essentially” and “approximately,” and their equivalents, when used in conjunction with ranges of dimensions, concentrations, temperatures or other physical or chemical properties or characteristics is meant to cover variations that may exist in the upper and/or lower limits of the ranges of the properties or characteristics, including, for example, variations resulting from rounding, measurement methodology or other statistical variation.

As various changes could be made in the above constructions and methods without departing from the scope of the disclosure, all matter contained in the above description and shown in the accompanying drawing(s) shall be interpreted as illustrative and not in a limiting sense.

Claims

1. A three-way heat exchanger operable to transfer heat between a heat transfer fluid, a liquid desiccant, and air, the three-way heat exchanger comprising: an airflow inlet and an airflow outlet;a heat transfer fluid inlet manifold extending proximate the airflow outlet and a heat transfer fluid outlet manifold extending proximate the airflow inlet; andpanel assemblies arranged with airflow gaps defined between adjacent panel assemblies to allow the air to flow between the airflow inlet and the airflow outlet in an airflow direction, each panel assembly comprising: a frame defining a heat transfer fluid channel, the heat transfer fluid channel being connected to the heat transfer fluid inlet and outlet manifolds for channeling a flow of the heat transfer fluid therebetween counter to the airflow direction;a membrane positioned on the frame and defining a desiccant channel for a flow of the liquid desiccant; anda heat transfer fluid flow guide positioned in the heat transfer fluid channel to control the flow of the heat transfer fluid counter to the airflow direction, the heat transfer fluid flow guide defining a heat transfer fluid flow path including a series of passageways, each passageway extending across the airflow direction.

2. The three-way heat exchanger of claim 1, wherein the heat transfer fluid flow guide comprises a sheet body and baffles located on the sheet body, wherein the baffles define the heat transfer fluid flow path.

3. The three-way heat exchanger of claim 2, wherein the baffles are located on both sides of the sheet body and define a first heat transfer fluid flow path on one side of the sheet body and a second heat transfer fluid flow path on another side of the sheet body.

4. The three-way heat exchanger of claim 3, wherein the first and second heat transfer fluid flow paths are complementary, and wherein the heat transfer fluid flow paths each define a winding path.

5. The three-way heat exchanger of claim 3, wherein each panel assembly comprises two membranes, each membrane positioned on one side of the frame, wherein one membrane defines a first desiccant channel and another membrane defines a second desiccant channel, wherein the first heat transfer fluid flow path is defined between the sheet body and the first desiccant channel and the second heat transfer fluid flow path is defined between the sheet body and the second desiccant channel.

6. The three-way heat exchanger of claim 5, wherein each panel assembly comprises two plates, each plate positioned between one of the membranes and the frame, wherein the plates separate the desiccant channels from the heat transfer fluid channel.

7. The three-way heat exchanger of claim 6, wherein the heat transfer fluid flow guide includes protrusions on the sheet body to maintain a width of the heat transfer fluid channel, measured between the plates, when the heat transfer fluid is flowed through the heat transfer fluid channel at a negative pressure.

8. The three-way heat exchanger of claim 1, wherein the airflow direction is horizontal and the passageways of the heat transfer fluid flow path each extend vertically across the airflow direction.

9. The three-way heat exchanger of claim 8, wherein a clearance is defined in the heat transfer fluid channel above the heat transfer fluid flow guide, the clearance being connected to one or more of the passageways of the heat transfer fluid flow path to capture entrained air from the flow of the heat transfer fluid.

10. The three-way heat exchanger of claim 1, wherein, for each panel assembly, an area of the heat transfer fluid channel located proximate the airflow inlet of the three-way heat exchanger is separated from the heat transfer fluid flow path by the heat transfer fluid flow guide.

11. A three-way heat exchanger operable to transfer heat between a heat transfer fluid, a liquid desiccant, and air, the three-way heat exchanger comprising: a heat transfer fluid inlet manifold and a heat transfer fluid outlet manifold; andpanel assemblies arranged with airflow gaps defined between adjacent panel assemblies to allow the air to flow through the three-way heat exchanger, each panel assembly comprising: a frame defining a heat transfer fluid channel, the heat transfer fluid channel being connected to the heat transfer fluid inlet and outlet manifolds for channeling a flow of the heat transfer fluid through the panel assembly;two membranes positioned on the frame, each membrane defining a desiccant channel separated from the heat transfer fluid channel; anda heat transfer fluid flow guide positioned in the heat transfer fluid channel, the heat transfer fluid flow guide comprising: a sheet body; andbaffles defining a first flow path on one side of the sheet body and a second flow path on another side of the sheet body, wherein the first and second flow paths are separated by the sheet body.

12. The three-way heat exchanger of claim 11, wherein the sheet body is shaped to allow the heat transfer fluid in the heat transfer fluid channel to flow on each side of the sheet body through each flow path.

13. The three-way heat exchanger of claim 11, wherein each flow path includes a series of passageways to define a winding path.

14. The three-way heat exchanger of claim 11, wherein the frame and the heat transfer fluid flow guide have complementing alignment features for orienting the heat transfer fluid flow guide in the heat transfer fluid channel.

15. The three-way heat exchanger of claim 11, wherein the baffles and the sheet body are made integrally of one material.

16. The three-way heat exchanger of claim 11, wherein each panel assembly comprises two plates, each plate positioned between one of the membranes and the frame to separate the desiccant channels from the heat transfer fluid channel, and wherein the heat transfer fluid flow guide includes protrusions on the sheet body to maintain a width of the heat transfer fluid channel, measured between the plates, when the heat transfer fluid is flowed through the heat transfer fluid channel at a negative pressure.

17. A heat exchanger operable to transfer heat between a heat transfer fluid and air, the heat exchanger comprising: a heat transfer fluid inlet manifold and a heat transfer fluid outlet manifold; andpanel assemblies arranged with airflow gaps defined between adjacent panel assemblies to allow the air to flow through the heat exchanger, each panel assembly comprising: a frame connected to the heat transfer fluid inlet and outlet manifolds;two plates positioned on the frame, the plates and the frame defining a heat transfer fluid channel for channeling the heat transfer fluid through the panel assembly; anda heat transfer fluid flow guide positioned in the heat transfer fluid channel, the heat transfer fluid flow guide comprising: a sheet body;baffles on the sheet body, the baffles defining a flow path for the heat transfer fluid in the heat transfer fluid channel; andprotrusions on the sheet body to maintain a width of the heat transfer fluid channel, measured between the plates, when the heat transfer fluid is flowed through the heat transfer fluid channel at a negative pressure.

18. The heat exchanger of claim 17, wherein the baffles, the protrusions, and the sheet body are made integrally of one material.

19. The heat exchanger of claim 18, wherein the one material is a polymer material.

20. The heat exchanger of claim 17, wherein the heat transfer fluid flow guide is able to float in the heat transfer fluid channel.