Patent Application
20240328643
The present invention relates to air conditioning systems and, more specifically, to an air conditioning system employing liquid desiccants.
The most common method of air conditioning is vapor compression. Vapor compression systems use electricity intensive compressors and high Global Warming Potential (GWP) refrigerants. GWP refrigerants can be volatile and can enter the atmosphere upon leaking. Other air conditioning systems utilize dessicant systems which use hot air to pull moisture off of the desiccant during regeneration. That hot moisture is then exhausted to the outside, going unused. Other thermoresponsive air conditioning systems use solid desiccants. These solid desiccants cannot be easily pumped throughout the system.
Therefore, what is needed is systems and methods for convenient and energy efficient liquid dessicant-based air conditioning that has the ability to pump the liquid desiccant through the system. For example, systems where the liquid can be easily pumped through highly efficient counterflow heat and mass exchangers.
The present disclosure relates to processes and systems for air conditioning. An exemplary embodiment of the present disclosure provides an air conditioning system including a lower critical solution temperature (LCST) liquid desiccant, a heater, a separator, an absorber, and a desorber. The lower critical solution temperature (LCST) liquid desiccant can be configured to have a moderate phase liquid configured to separate into a weak phase liquid and strong phase liquid upon heating. The heater can be configured to transfer heat to the moderate phase liquid to separate the moderate phase liquid into the weak phase liquid and the strong phase liquid. The separator can be configured to physically separate the weak phase liquid and strong phase liquid. The absorber can be configured to receive the strong phase liquid. The strong phase liquid absorbs moisture from air thereby dehumidifying the air. The desorber can be configured to receive the weak phase liquid wherein the weak phase liquid desorbs moisture to air thereby cooling the desorber through evaporative cooling.
In any of the embodiments disclosed herein, the air conditioning system can further include a recuperator configured to transfer heat to the moderate phase liquid from the weak phase liquid and the strong phase liquid.
In any of the embodiments disclosed herein, the air conditioning system can further include an air-to-air heat exchanger configured to receive the dehumidified air from the absorber and the humidified air from the desorber and transfer heat from the dehumidified air to the humidified air.
In any of the embodiments disclosed herein, the air conditioning system can further include one or more liquid-to-air heat exchangers to transfer heat from one or more of the weak phase liquid or strong phase liquid to ambient.
In any of the embodiments disclosed herein, the air conditioning system can further include a first fan that blows air over the absorber to reduce its temperature.
In any of the embodiments disclosed herein, the air conditioning system can further include a second fan that blows air over the desorber, thereby cooling the air passing over the desorber.
In any of the embodiments disclosed herein, the air conditioning system can further include a secondary desorber configured to receive the weak phase liquid leaving the desorber, wherein the weak phase liquid desorbs moisture to air.
In any of the embodiments disclosed herein, the absorber can include a plurality of channels with downward flowing strong phase liquid and upward flowing air and a plurality of heat exchanger fins extending from an exterior of the absorber channels.
In any of the embodiments disclosed herein, the desorber can include a plurality of channels with downward flowing strong phase liquid and upward flowing air and a plurality of heat exchanger fins extending from an exterior of the absorber channels.
In any of the embodiments disclosed herein, the heater can include a section of pipe with LCST liquid desiccant flowing in it, wherein the section of pipe comprises a dark color exterior to absorb energy from the sun.
In any of the embodiments disclosed herein, the heater can include one or more of solar heat, waste heat, gas heat, or electric heat.
In any of the embodiments disclosed herein, the recuperator can include a first heat exchanger configured to transfer heat from the weak phase liquid to the moderate phase liquid and a second heat exchanger configured to transfer heat from the strong phase liquid to the moderate phase liquid.
In any of the embodiments disclosed herein, the recuperator can include a single heat exchanger that has the moderate phase liquid flowing in a first direction and the weak and strong phase liquid flowing in a second direction, wherein the moderate, weak, and strong phase liquids are all physically separated.
In any of the embodiments disclosed herein, the air conditioning system can further include a desiccant storage tank configured to store excess LCST liquid desiccant.
In any of the embodiments disclosed herein, the separator can include a separation tank configured to separate, via gravity, the weak phase liquid and the strong phase liquid.
In any of the embodiments disclosed herein, the air conditioning system can further include a combined desiccant storage tank configured to store excess LCST liquid desiccant and separation tank configured to separate, via gravity, the weak phase liquid and the strong phase liquid.
Another exemplary embodiment of the present disclosure provides a method of air conditioning. The method can include heating a lower critical solution temperature (LCST) liquid desiccant to a temperature higher than ambient temperature so that the LCST separates from a moderate phase liquid to a strong phase liquid and a weak phase liquid, separating the strong phase liquid from the weak phase liquid, cooling the strong phase liquid and the weak phase liquid, absorbing water from air to the strong phase liquid, thereby dehumidifying the air, desorbing water from the weak phase liquid to air, thereby humidifying the air and cooling, via evaporative cooling, ambient, and recombining the strong phase liquid with the weak phase liquid.
In any of the embodiments disclosed herein, the method can further include exchanging heat from the dehumidified air to the humidified air.
In any of the embodiments disclosed herein, heating can be achieved at least partially by heating with a recuperator configured to transfer heat from the weak phase and strong phase liquids to the moderate phase liquid.
In any of the embodiments disclosed herein, heating can be achieved at least partially by heating by a section of pipe with LCST flowing in it. The section of pipe can be a dark color to absorb energy from the sun.
In any of the embodiments disclosed herein, heating can be achieved at least partially by heating by one or more of solar heat, waste heat, gas heat, or electric heat.
Another exemplary embodiment of the present disclosure provides an air conditioning system including a lower critical solution temperature (LCST) liquid desiccant configured to have a moderate phase liquid configured to separate into a weak phase liquid and strong phase liquid upon heating, an outside portion, and an inside unit.
The outside portion can include a recuperator, a heater, a separator, an absorber, and an air-to-air heat exchanger.
In any of the embodiments disclosed herein, the recuperator can be configured to transfer heat to the moderate phase liquid from the weak phase liquid and the strong phase liquid.
In any of the embodiments disclosed herein, the heater can be configured to transfer heat to the moderate phase liquid to separate the moderate phase liquid into the weak phase liquid and the strong phase liquid.
In any of the embodiments disclosed herein, the separator can be configured to physically separate the weak phase liquid and strong phase liquid.
In any of the embodiments disclosed herein, the absorber can be configured to receive the strong phase liquid wherein the strong phase liquid absorbs moisture from outside air thereby dehumidifying the outside air.
In any of the embodiments disclosed herein, the inside unit can include a desorber configured to receive the weak phase liquid wherein the weak phase liquid desorbs moisture to inside air thereby cooling the desorber through evaporative cooling and a liquid-to-liquid heater configured to transfer heat from the weak phase liquid entering the desorber to the weak phase liquid leaving the desorber. The heat exchanger can be configured to receive the dehumidified outside air from the absorber and the humidified inside air from the desorber and transfer heat from the dehumidified outside air to the humidified inside air.
The following detailed description of specific embodiments of the disclosure will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the disclosure, specific embodiments are shown in the drawings. It should be understood, however, that the disclosure is not limited to the precise arrangements and instrumentalities of the embodiments shown in the drawings.
To facilitate an understanding of the principles and features of the present disclosure, various illustrative embodiments are explained below. The components, steps, and materials described hereinafter as making up various elements of the embodiments disclosed herein are intended to be illustrative and not restrictive. Many suitable components, steps, and materials that would perform the same or similar functions as the components, steps, and materials described herein are intended to be embraced within the scope of the disclosure. Such other components, steps, and materials not described herein can include, but are not limited to, similar components or steps that are developed after development of the embodiments disclosed herein.
In any of the embodiments disclosed herein, the air conditioning system (100) can further include a recuperator (160) configured to transfer heat to the moderate phase liquid (110c) from the weak phase liquid (110a) and the strong phase liquid (110b).
In any of the embodiments disclosed herein, the air conditioning system (100) can further include an air-to-air heat exchanger (170) configured to receive the dehumidified air from the absorber (140) and the humidified air from the desorber (150) and transfer heat from the dehumidified air to the humidified air.
In any of the embodiments disclosed herein, the air conditioning system (100) can further include one or more liquid-to-air heat exchangers (180) to transfer heat from one or more of the weak phase liquid (110a) or strong phase liquid (110b) to ambient.
In any of the embodiments disclosed herein, the air conditioning system (100) can further include a first fan (190) that blows air over the absorber (140) to reduce its temperature.
In any of the embodiments disclosed herein, the air conditioning system can further include a second fan (200) that blows air over the desorber (150), thereby cooling the air passing over the desorber (150).
In any of the embodiments disclosed herein, the air conditioning system (100) can further include a secondary desorber (210) configured to receive the weak phase liquid (110a) leaving the desorber (150), wherein the weak phase liquid (110a) desorbs moisture to air.
In any of the embodiments disclosed herein, the absorber (140) can include a plurality of channels (142) with downward flowing strong phase liquid (110b) and upward flowing air and a plurality of heat exchanger fins (144) extending from an exterior of the absorber channels.
In any of the embodiments disclosed herein, the desorber (150) can include a plurality of channels (152) with downward flowing strong phase liquid (110b) and upward flowing air and a plurality of heat exchanger fins (154) extending from an exterior (142a) of the absorber channels (142).
In any of the embodiments disclosed herein, the heater (120) can include a section of pipe (122) with LCST liquid desiccant (110) flowing in it, wherein the section of pipe comprises a dark color exterior to absorb energy from the sun.
In any of the embodiments disclosed herein, the heater (120) can include one or more of solar heat, waste heat, gas heat, or electric heat.
In any of the embodiments disclosed herein, the recuperator (160) can include a first heat exchanger (162) configured to transfer heat from the weak phase liquid (110a) to the moderate phase liquid (110c) and a second heat exchanger (164) configured to transfer heat from the strong phase liquid (110b) to the moderate phase liquid (110c).
In any of the embodiments disclosed herein, the recuperator (160) can include a single heat exchanger (161) that has the moderate phase liquid (110c) flowing in a first direction (166) and the weak (110a) and strong phase liquid (110b) flowing in a second direction (168), wherein the moderate (110c), weak (110a), and strong (110b) phase liquids are all physically separated.
In any of the embodiments disclosed herein, the air conditioning system (100) can further include a desiccant storage tank (220) configured to store excess LCST liquid desiccant (110).
In any of the embodiments disclosed herein, the separator (130) can include a separation tank (132) configured to separate, via gravity, the weak phase liquid (110a) and the strong phase liquid (110b).
In any of the embodiments disclosed herein, the air conditioning system (100) can further include a combined desiccant storage tank 220) configured to store excess LCST liquid desiccant (110) and separation tank (132) configured to separate, via gravity, the weak phase liquid (110a) and the strong phase liquid (110b).
In any of the embodiments disclosed herein, for example as illustrated in
In any of the embodiments disclosed herein, heating (302) can be achieved at least partially by heating (302) with a recuperator configured to transfer heat from the weak phase and strong phase liquids to the moderate phase liquid.
In any of the embodiments disclosed herein, heating (302) can be achieved at least partially by heating (302) by a section of pipe with LCST flowing in it. The section of pipe can be a dark color to absorb energy from the sun.
In any of the embodiments disclosed herein, heating (302) can be achieved at least partially by heating (302) by one or more of solar heat, waste heat, gas heat, or electric heat.
The outside portion (105) can include a recuperator (160), a heater (120), a separator (130), an absorber (140), and an air-to-air heat exchanger (170).
In any of the embodiments disclosed herein, the recuperator (160) can be configured to transfer heat to the moderate phase liquid (110c) from the weak phase liquid (110a) and the strong phase liquid (110b).
In any of the embodiments disclosed herein, the heater (120) can be configured to transfer heat to the moderate phase liquid (110c) to separate the moderate phase liquid (110c) into the weak phase liquid (110a) and the strong phase liquid (110b).
In any of the embodiments disclosed herein, the separator (130) can be configured to physically separate the weak phase liquid (110a) and strong phase liquid (110b).
In any of the embodiments disclosed herein, the absorber (140) can be configured to receive the strong phase liquid (110b) wherein the strong phase liquid (110b) absorbs moisture from outside air thereby dehumidifying the outside air.
In any of the embodiments disclosed herein, the inside unit (240) can include a desorber (150) configured to receive the weak phase liquid (110a) wherein the weak phase liquid (110a) desorbs moisture to inside air thereby cooling the desorber (150) through evaporative cooling and a liquid-to-liquid heater (230) configured to transfer heat from the weak phase liquid (110a) entering the desorber (150) to the weak phase liquid (110a) leaving the desorber (150). The heat exchanger (170) can be configured to receive the dehumidified outside air from the absorber (140) and the humidified inside air from the desorber (150) and transfer heat from the dehumidified outside air to the humidified inside air.
In any of the embodiments disclosed herein, the outside unit (105) can include a secondary desorber(
The following examples further illustrate aspects of the present disclosure. However, they are in no way a limitation of the teachings or disclosure of the present disclosure as set forth herein.
In one representative embodiment, the invention includes a thermally-driven air conditioning system that provides both dehumidification and cooling, without the use of high Global Warming Potential refrigerants or an external water supply, and it consumes little electricity. To accomplish this, the working fluid in the system is a thermoresponsive liquid desiccant that possesses a lower critical solution temperature. The desiccant first absorbs moisture from the air, providing dehumidification. Then, the desiccant is heated with a “free” heat source like solar- or waste-heat, which causes the desiccant to separate into two phases. One phase is mostly water while the other phase is mostly desiccant. The two phases are cooled back down to ambient temperature, and the mostly-water phase is used to evaporatively cool the building, owing to its high water activity. No compressor is needed, only fans and pumps, which greatly reduces the electricity consumption.
One embodiment of the invention includes of an air conditioning system that uses a lower critical solution temperature (LCST) liquid desiccant to absorb moisture from and evaporatively cool building air. This invention is the first air conditioning to utilize an LCST liquid as the working fluid. The regeneration of the liquid desiccant is heat-driven, eliminating the need for the compressors that are required in common vapor compression air conditioning systems. The phase behavior of the LCST liquid allows for phase separation-based regeneration, a novelty when compared to traditional liquid desiccants. Additionally, in this invention, the water absorbed from the air is used for evaporative cooling, a process that is not used in traditional air conditioning systems.
The invention can be used for temperature and humidity control of air in buildings. The LCST liquid desiccant both lowers the temperature and humidity of the air, providing air that is within the bounds of thermal comfort and healthy humidities. The invention can be used to create both large-scale air conditioning systems (central air conditioner) and small-scale systems (ductless or window air conditioners).
The first process in the invention is the sensible heating, which raises the temperature of the desiccant. In
The second process in the invention is the latent heating. This is the heat required to phase separate the LCST liquid desiccant. This is the primary energy input to the system. In
The third process is sensible cooling, which is achieved with the recuperator in
The fourth process in the invention is further sensible cooling, in which the LCST liquid desiccant is cooled down to ambient temperature. This can be achieved with a liquid-to-air heat exchanger that blows ambient air over coils through which the desiccant flows.
The fifth process has two parts. First is the water vapor absorption of the strong desiccant phase. In this process, the desiccant is pumped through a column, along with air. As the air passes over the desiccant in the absorber (140), water is transferred from the air to the desiccant.
The second part of the fifth process is the desorption of water vapor from the weak desiccant. This process absorbs heat (i.e., produces cooling), so this portion of the system is located inside of the building. Cool desiccant and cool, dry building air enter the desorption unit, again in the counterflow arrangement. The air absorbs moisture from the desiccant, which dries out the desiccant, humidifies the air, and produces evaporative cooling. To keep the device at constant temperature, building air is blown over the exterior of the desorption unit; this provides cooling to the building. The desiccant leaving this desorption unit is sent to a heat exchanger to cool the desiccant entering the desorption unit.
The air leaving the desorption unit is cool but humid, so it can't be sent back into the building. The final process involves the warm, dry air leaving the absorption unit and the cool, humid air leaving the desorption unit being sent to a heat exchanger. This warms the cool, humid air and cools the warm, dry air. The humid air is then exhausted to the outside, while the cool, dry air is sent to the building.
If the cool (room temperature) desorption unit is unable to sufficiently dry out the weak desiccant, a second, ambient temperature desorption unit can be used. In this case, the weak desiccant desorbs more of its water content to outside air at ambient temperature. The desiccant leaving the desorption and absorption units are then recombined, thereby completing the cycle.
The invention, as generally described in
The invention could also be used to construct a ductless or window air conditioning unit. For the window unit, the outdoor portion of the system would simply be placed in the back of the device, while the indoor portion would be placed in the front of the device. The window unit would then be placed such that the back of the unit is exposed to the outside air and the front of the unit is inside of the building (much like in a traditional window air conditioning unit).
If an electrical or gas heater is used as the heat source for the invention, then the desiccant can be regenerated at any time. However, if a solar heater is used, then sunlight is only present to regenerate the desiccant during the day. One option to circumvent this intermittency of the heat source is to install thermal energy storage, which absorbs heat from the sun during the day and could be used to regeneratively heat the desiccant throughout the night. The other option is to install a tank with an excess of desiccant. In fact, a desiccant tank is already shown in
The first set of advantages can be seen when comparing the invention to the most common method of air conditioning: vapor compression. Vapor compression systems use electricity intensive compressors and high Global Warming Potential (GWP) refrigerants. The LCST liquid air conditioning invention does not use any compressors, only pumps and fans, which consume far less electricity than compressors. The invention also does not use high GWP refrigerants; the LCST liquids in the invention are not volatile and thus do not enter the atmosphere upon leaking, like traditional refrigerants do.
The second set of advantages can be seen when comparing the invention to traditional liquid desiccant air conditioning systems. Traditional desiccant systems use hot air to pull moisture off of the desiccant during regeneration. That hot moisture is then exhausted to the outside, going unused. In the LCST liquid air conditioning invention, regeneration is achieved not with hot air but with phase separation. This allows the desorption of water to become a useful process: indirect evaporative cooling of the conditioned air.
The third set of advantages can be seen when comparing the invention to other thermoresponsive air conditioning systems that use solid desiccants. These solid thermoresponsive desiccants are regenerated through phase transition, just like the liquid desiccant in this invention. However, the solid desiccants cannot be easily pumped throughout the system, while the liquid desiccants in this invention can. The ability to pump the liquid desiccant through the system provides both convenience and efficiency, as the liquid can be easily pumped through highly efficient counterflow heat and mass exchangers.
The most promising commercial application for this invention is building air conditioning systems. These range from large central air conditioning systems in residential and commercial buildings, to small window units for single rooms. The global air conditioning market was $179.64 billion in 2020, and the current air conditioning system that dominates the market is the vapor compression system. This invention would be more environmentally friendly and yield lower operational costs than the vapor compression system, thereby making it desirable to consumers and giving it the opportunity to significantly penetrate this large market.
While the most obvious use for this invention is building air conditioning, this invention could also be used for refrigeration and food storage. The invention can efficiently provide air at low temperatures and humidities, which could be useful for food preservation. However, refrigeration requires lower temperatures than building air conditioning (it is easier to achieve human thermal comfort than it is to achieve food safe conditions). The lowest temperature that this system could achieve is limited by psychrometrics (namely, the wet bulb temperature of the secondary air), and it would be unlikely to achieve temperatures lower than 10° C. with this invention.
Another possible application of this invention is for humidity control in data centers. Data centers require relative humidities between 45 to 55% to prevent electrostatic discharge. This invention provides a highly efficient method of dehumidification that would require little electricity input. This would be desirable for data centers, which seek to reduce their operational costs as much as possible. This could allow this invention to significantly penetrate the roughly $8 billion market3 of data center humidity and temperature control.
It is to be understood that the embodiments and claims disclosed herein are not limited in their application to the details of construction and arrangement of the components set forth in the description and illustrated in the drawings. Rather, the description and the drawings provide examples of the embodiments envisioned. The embodiments and claims disclosed herein are further capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purposes of description and should not be regarded as limiting the claims.
Accordingly, those skilled in the art will appreciate that the conception upon which the application and claims are based may be readily utilized as a basis for the design of other structures, methods, and systems for carrying out the several purposes of the embodiments and claims presented in this application. It is important, therefore, that the claims be regarded as including such equivalent constructions.
Furthermore, the purpose of the foregoing Abstract is to enable the United States Patent and Trademark Office and the public generally, and especially including the practitioners in the art who are not familiar with patent and legal terms or phraseology, to determine quickly from a cursory inspection the nature and essence of the technical disclosure of the application. The Abstract is neither intended to define the claims of the application, nor is it intended to be limiting to the scope of the claims in any way.
This application claims the benefit of U.S. Provisional Application Ser. No. 63/329,572 filed on 11 Apr. 2022, which is incorporated herein by reference in its entirety as if fully set forth below.
This invention was made with government support under grant/award number DOE-EERE-RPP-IBUILD-2020 awarded by the Department of Energy. The government has certain rights in the invention.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2023/065629 | 4/11/2023 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63329752 | Apr 2022 | US |
