REFRIGERANT CHARGE MANAGEMENT SYSTEMS AND METHODS

BACKGROUND

The present disclosure relates generally to heating, ventilation, and air conditioning systems. A wide range of applications exist for heating, ventilating, and air conditioning (HVAC) systems. For example, residential, light commercial, commercial, and industrial systems are used to control temperatures and air quality in residences and buildings. Such systems often are dedicated to either heating or cooling, although systems are common that perform both of these functions. Very generally, these systems operate by implementing a thermal cycle in which fluids are heated and cooled to provide the desired temperature in a controlled space, typically the inside of a residence or building. Similar systems are used for vehicle heating and cooling, and as well as for general refrigeration. Many HVAC systems may utilize fans, or blowers, in operation. For example, fans may be used for expelling exhaust air, moving air through a heat exchanger, and drawing in return air. In certain instances, the HVAC system may have an optimal or desired charge level of refrigerant to operate efficiently. However, the optimal charge level may vary based on a mode of the HVAC system, such as a heating or cooling mode, an ambient temperature, a pressure of the refrigerant within the HVAC system, among other factors and parameters. However, in some instances, the charge level of the HVAC system may be static or difficult to change.

SUMMARY

The present disclosure relates to a passive refrigerant charge management system including a charge vessel configured to fluidly couple to a refrigerant circuit. The charge vessel includes a first portion having a compressible fluid and a second portion configured to contain refrigerant of the refrigerant circuit, wherein an amount of the refrigerant contained in the second portion is based on a first pressure of the refrigerant within the refrigerant circuit and a second pressure of the compressible fluid.

The present disclosure also relates to a heating, ventilation, and air conditioning (HVAC) system having a refrigerant circuit configured to flow a refrigerant and a charge vessel fluidly coupled to the refrigerant circuit, wherein the charge vessel is configured to passively adjust a refrigerant charge level of the refrigerant circuit based on a pressure of the refrigerant within the refrigerant circuit.

The present disclosure further relates to a heating, ventilation, and air conditioning (HVAC) system having a refrigerant loop, a condenser disposed along the refrigerant loop and configured to condense refrigerant of the refrigerant loop, and a charge vessel disposed along the refrigerant loop and configured to passively adjust a refrigerant charge of the refrigerant loop based on a discharge pressure of the refrigerant from the condenser.

DRAWINGS

FIG. 1 is a perspective view of a heating, ventilating, and air conditioning (HVAC) system for building environmental management that may employ one or more HVAC units, in accordance with an embodiment of the present disclosure;

FIG. 2 is a perspective view of an HVAC unit of the HVAC system of FIG. 1, in accordance with an embodiment of the present disclosure;

FIG. 3 is a perspective view of a residential split heating and cooling system, in accordance with an embodiment of the present disclosure;

FIG. 4 is a schematic view of a vapor compression system that may be used in an HVAC system, in accordance with an embodiment of the present disclosure;

FIG. 5 is a schematic view of a heat pump system having a passive charge management system, in accordance with an embodiment of the present disclosure;

FIG. 6 is a schematic view of an air conditioning system having a passive charge management system, in accordance with an embodiment of the present disclosure;

FIG. 7 is a schematic view of a charge vessel of the passive charge management systems of FIGS. 5 and 6, in accordance with an embodiment of the present disclosure; and

FIG. 8 is a schematic view of a charge vessel of the passive charge management systems of FIGS. 5 and 6, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

Heating, ventilation, and air conditioning (HVAC) systems may include an optimum or desired charge level, or a quantity of refrigerant, to operate efficiently. However, the optimal or desired charge level may fluctuate as an ambient temperature, a mode of the HVAC system, or a refrigerant pressure within the HVAC system changes. For example, as an outdoor temperature increases, some amount of refrigerant may collect or become backed up in the condensing heat exchanger of the HVAC system. The HVAC system may increase an input power of a pump to process the collected refrigerant, thereby decreasing an efficiency of the HVAC system. Indeed, in such instances, a decreased charge level may increase an efficiency of the HVAC system. Similarly, as an outdoor temperature decreases, the amount of refrigerant that is collected or backed up in the condensing heat exchanger may decrease. This may result in an incomplete column of liquid flowing to the expansion device from the heat exchanger, thereby decreasing an efficiency of the HVAC system. Indeed, in such instances, an increased charge level may increase an efficiency of the HVAC system.

Accordingly, the present disclosure is directed to heating, ventilation, and air conditioning (HVAC) systems and units, which may include a passive refrigerant charge management system. Particularly, the HVAC systems may include a charge vessel configured to accept varied amounts of refrigerant depending on conditions of the HVAC system and/or surrounding environment. The charge vessel may be a rigid container that is fluidly coupled to a liquid line of a refrigerant circuit of the HVAC system. Moreover, the charge vessel may be divided into two sections: a first section having a set amount of compressible fluid and a second section in fluid communication with liquid refrigerant of the HVAC system and configured to accept various amounts of refrigerant. The amount of refrigerant accepted in the second section may depend at least in part on a pressure of the refrigerant within the liquid line portion of the refrigerant circuit. The first and second sections are divided within the rigid container by a flexible divider, such as a bladder, membrane, or diaphragm. As discussed herein, the flexible divider may expand and contract in response to pressures of the refrigerant within the refrigerant circuit to adjust the refrigerant charge in the refrigerant circuit. For example, when the refrigerant pressure in the refrigerant loop is higher, the flexible membrane may deform to decrease a volume of the first section and thereby increase refrigerant charge accepted into the second section. Similarly, when the refrigerant pressure in the refrigerant loop is lower, the flexible membrane may deform to increase a volume of the first section and thereby decrease the refrigerant charge accepted into the second section. In other embodiments, the divider may be passively biased by a mechanical feature, such as a spring or other mechanism that applies force when compressed.

Turning now to the drawings, FIG. 1 illustrates a heating, ventilating, and air conditioning (HVAC) system for building environmental management that may employ one or more HVAC units. In the illustrated embodiment, a building 10 is air conditioned by a system that includes an HVAC unit 12. The building 10 may be a commercial structure or a residential structure. As shown, the HVAC unit 12 is disposed on the roof of the building 10; however, the HVAC unit 12 may be located in other equipment rooms or areas adjacent the building 10. The HVAC unit 12 may be a single package unit containing other equipment, such as a blower, integrated air handler, and/or auxiliary heating unit. In other embodiments, the HVAC unit 12 may be part of a split HVAC system, such as the system shown in FIG. 3, which includes an outdoor HVAC unit 58 and an indoor HVAC unit 56.

The HVAC unit 12 is an air cooled device that implements a refrigeration cycle to provide conditioned air to the building 10. Specifically, the HVAC unit 12 may include one or more heat exchangers across which an air flow is passed to condition the air flow before the air flow is supplied to the building. In the illustrated embodiment, the HVAC unit 12 is a rooftop unit (RTU) that conditions a supply air stream, such as environmental air and/or a return air flow from the building 10. After the HVAC unit 12 conditions the air, the air is supplied to the building 10 via ductwork 14 extending throughout the building 10 from the HVAC unit 12. For example, the ductwork 14 may extend to various individual floors or other sections of the building 10. In certain embodiments, the HVAC unit 12 may be a heat pump that provides both heating and cooling to the building with one refrigeration circuit configured to operate in different modes. In other embodiments, the HVAC unit 12 may include one or more refrigeration circuits for cooling an air stream and a furnace for heating the air stream.

A control device 16, one type of which may be a thermostat, may be used to designate the temperature of the conditioned air. The control device 16 also may be used to control the flow of air through the ductwork 14. For example, the control device 16 may be used to regulate operation of one or more components of the HVAC unit 12 or other components, such as dampers and fans, within the building 10 that may control flow of air through and/or from the ductwork 14. In some embodiments, other devices may be included in the system, such as pressure and/or temperature transducers or switches that sense the temperatures and pressures of the supply air, return air, and so forth. Moreover, the control device 16 may include computer systems that are integrated with or separate from other building control or monitoring systems, and even systems that are remote from the building 10.

FIG. 2 is a perspective view of an embodiment of the HVAC unit 12. In the illustrated embodiment, the HVAC unit 12 is a single package unit that may include one or more independent refrigeration circuits and components that are tested, charged, wired, piped, and ready for installation. The HVAC unit 12 may provide a variety of heating and/or cooling functions, such as cooling only, heating only, cooling with electric heat, cooling with dehumidification, cooling with gas heat, or cooling with a heat pump. As described above, the HVAC unit 12 may directly cool and/or heat an air stream provided to the building 10 to condition a space in the building 10.

As shown in the illustrated embodiment of FIG. 2, a cabinet 24 encloses the HVAC unit 12 and provides structural support and protection to the internal components from environmental and other contaminants. In some embodiments, the cabinet 24 may be constructed of galvanized steel and insulated with aluminum foil faced insulation. Rails 26 may be joined to the bottom perimeter of the cabinet 24 and provide a foundation for the HVAC unit 12. In certain embodiments, the rails 26 may provide access for a forklift and/or overhead rigging to facilitate installation and/or removal of the HVAC unit 12. In some embodiments, the rails 26 may fit into “curbs” on the roof to enable the HVAC unit 12 to provide air to the ductwork 14 from the bottom of the HVAC unit 12 while blocking elements such as rain from leaking into the building 10.

The HVAC unit 12 includes heat exchangers 28 and 30 in fluid communication with one or more refrigeration circuits. Tubes within the heat exchangers 28 and 30 may circulate refrigerant, such as R-410A, through the heat exchangers 28 and 30. The tubes may be of various types, such as multichannel tubes, conventional copper or aluminum tubing, and so forth. Together, the heat exchangers 28 and 30 may implement a thermal cycle in which the refrigerant undergoes phase changes and/or temperature changes as it flows through the heat exchangers 28 and 30 to produce heated and/or cooled air. For example, the heat exchanger 28 may function as a condenser where heat is released from the refrigerant to ambient air, and the heat exchanger 30 may function as an evaporator where the refrigerant absorbs heat to cool an air stream. In other embodiments, the HVAC unit 12 may operate in a heat pump mode where the roles of the heat exchangers 28 and 30 may be reversed. That is, the heat exchanger 28 may function as an evaporator and the heat exchanger 30 may function as a condenser. In further embodiments, the HVAC unit 12 may include a furnace for heating the air stream that is supplied to the building 10. While the illustrated embodiment of FIG. 2 shows the HVAC unit 12 having two of the heat exchangers 28 and 30, in other embodiments, the HVAC unit 12 may include one heat exchanger or more than two heat exchangers.

The heat exchanger 30 is located within a compartment 31 that separates the heat exchanger 30 from the heat exchanger 28. Fans 32 draw air from the environment through the heat exchanger 28. Air may be heated and/or cooled as the air flows through the heat exchanger 28 before being released back to the environment surrounding the rooftop unit 12. A blower assembly 34, powered by a motor 36, draws air through the heat exchanger 30 to heat or cool the air. The heated or cooled air may be directed to the building 10 by the ductwork 14, which may be connected to the HVAC unit 12. Before flowing through the heat exchanger 30, the conditioned air flows through one or more filters 38 that may remove particulates and contaminants from the air. In certain embodiments, the filters 38 may be disposed on the air intake side of the heat exchanger 30 to prevent contaminants from contacting the heat exchanger 30.

The HVAC unit 12 also may include other equipment for implementing the thermal cycle. Compressors 42 increase the pressure and temperature of the refrigerant before the refrigerant enters the heat exchanger 28. The compressors 42 may be any suitable type of compressors, such as scroll compressors, rotary compressors, screw compressors, or reciprocating compressors. In some embodiments, the compressors 42 may include a pair of hermetic direct drive compressors arranged in a dual stage configuration 44. However, in other embodiments, any number of the compressors 42 may be provided to achieve various stages of heating and/or cooling. As may be appreciated, additional equipment and devices may be included in the HVAC unit 12, such as a solid-core filter drier, a drain pan, a disconnect switch, an economizer, pressure switches, phase monitors, and humidity sensors, among other things.

The HVAC unit 12 may receive power through a terminal block 46. For example, a high voltage power source may be connected to the terminal block 46 to power the equipment. The operation of the HVAC unit 12 may be governed or regulated by a control board 48. The control board 48 may include control circuitry connected to a thermostat, sensors, and alarms. One or more of these components may be referred to herein separately or collectively as the control device 16. The control circuitry may be configured to control operation of the equipment, provide alarms, and monitor safety switches. Wiring 49 may connect the control board 48 and the terminal block 46 to the equipment of the HVAC unit 12.

FIG. 3 illustrates a residential heating and cooling system 50, also in accordance with present techniques. The residential heating and cooling system 50 may provide heated and cooled air to a residential structure, as well as provide outside air for ventilation and provide improved indoor air quality (IAQ) through devices such as ultraviolet lights and air filters. In the illustrated embodiment, the residential heating and cooling system 50 is a split HVAC system. In general, a residence 52 conditioned by a split HVAC system may include refrigerant conduits 54 that operatively couple the indoor unit 56 to the outdoor unit 58. The indoor unit 56 may be positioned in a utility room, an attic, a basement, and so forth. The outdoor unit 58 is typically situated adjacent to a side of residence 52 and is covered by a shroud to protect the system components and to prevent leaves and other debris or contaminants from entering the unit. The refrigerant conduits 54 transfer refrigerant between the indoor unit 56 and the outdoor unit 58, typically transferring primarily liquid refrigerant in one direction and primarily vaporized refrigerant in an opposite direction.

When the system shown in FIG. 3 is operating as an air conditioner, a heat exchanger 60 in the outdoor unit 58 serves as a condenser for re-condensing vaporized refrigerant flowing from the indoor unit 56 to the outdoor unit 58 via one of the refrigerant conduits 54. In these applications, a heat exchanger 62 of the indoor unit functions as an evaporator. Specifically, the heat exchanger 62 receives liquid refrigerant (which may be expanded by an expansion device, not shown) and evaporates the refrigerant before returning it to the outdoor unit 58.

The outdoor unit 58 draws environmental air through the heat exchanger 60 using a fan 64 and expels the air above the outdoor unit 58. When operating as an air conditioner, the air is heated by the heat exchanger 60 within the outdoor unit 58 and exits the unit at a temperature higher than it entered. The indoor unit 56 includes a blower or fan 66 that directs air through or across the indoor heat exchanger 62, where the air is cooled when the system is operating in air conditioning mode. Thereafter, the air is passed through ductwork 68 that directs the air to the residence 52. The overall system operates to maintain a desired temperature as set by a system controller. When the temperature sensed inside the residence 52 is higher than the set point on the thermostat, or the set point plus a small amount, the residential heating and cooling system 50 may become operative to refrigerate additional air for circulation through the residence 52. When the temperature reaches the set point, or the set point minus a small amount, the residential heating and cooling system 50 may stop the refrigeration cycle temporarily.

The residential heating and cooling system 50 may also operate as a heat pump. When operating as a heat pump, the roles of heat exchangers 60 and 62 are reversed. That is, the heat exchanger 60 of the outdoor unit 58 will serve as an evaporator to evaporate refrigerant and thereby cool air entering the outdoor unit 58 as the air passes over outdoor the heat exchanger 60. The indoor heat exchanger 62 will receive a stream of air blown over it and will heat the air by condensing the refrigerant.

In some embodiments, the indoor unit 56 may include a furnace system 70. For example, the indoor unit 56 may include the furnace system 70 when the residential heating and cooling system 50 is not configured to operate as a heat pump. The furnace system 70 may include a burner assembly and heat exchanger, among other components, inside the indoor unit 56. Fuel is provided to the burner assembly of the furnace 70 where it is mixed with air and combusted to form combustion products. The combustion products may pass through tubes or piping in a heat exchanger, separate from heat exchanger 62, such that air directed by the blower 66 passes over the tubes or pipes and extracts heat from the combustion products. The heated air may then be routed from the furnace system 70 to the ductwork 68 for heating the residence 52.

FIG. 4 is an embodiment of a vapor compression system 72 that can be used in any of the systems described above. The vapor compression system 72 may circulate a refrigerant through a circuit starting with a compressor 74. The circuit may also include a condenser 76, an expansion valve(s) or device(s) 78, and an evaporator 80. The vapor compression system 72 may further include a control panel 82 that has an analog to digital (A/D) converter 84, a microprocessor 86, a non-volatile memory 88, and/or an interface board 90. The control panel 82 and its components may function to regulate operation of the vapor compression system 72 based on feedback from an operator, from sensors of the vapor compression system 72 that detect operating conditions, and so forth.

In some embodiments, the vapor compression system 72 may use one or more of a variable speed drive (VSDs) 92, a motor 94, the compressor 74, the condenser 76, the expansion valve or device 78, and/or the evaporator 80. The motor 94 may drive the compressor 74 and may be powered by the variable speed drive (VSD) 92. The VSD 92 receives alternating current (AC) power having a particular fixed line voltage and fixed line frequency from an AC power source, and provides power having a variable voltage and frequency to the motor 94. In other embodiments, the motor 94 may be powered directly from an AC or direct current (DC) power source. The motor 94 may include any type of electric motor that can be powered by a VSD or directly from an AC or DC power source, such as a switched reluctance motor, an induction motor, an electronically commutated permanent magnet motor, or another suitable motor.

The compressor 74 compresses a refrigerant vapor and delivers the vapor to the condenser 76 through a discharge passage. In some embodiments, the compressor 74 may be a centrifugal compressor. The refrigerant vapor delivered by the compressor 74 to the condenser 76 may transfer heat to a fluid passing across the condenser 76, such as ambient or environmental air 96. The refrigerant vapor may condense to a refrigerant liquid in the condenser 76 as a result of thermal heat transfer with the environmental air 96. The liquid refrigerant from the condenser 76 may flow through the expansion device 78 to the evaporator 80.

The liquid refrigerant delivered to the evaporator 80 may absorb heat from another air stream, such as a supply air stream 98 provided to the building 10 or the residence 52. For example, the supply air stream 98 may include ambient or environmental air, return air from a building, or a combination of the two. The liquid refrigerant in the evaporator 80 may undergo a phase change from the liquid refrigerant to a refrigerant vapor. In this manner, the evaporator 38 may reduce the temperature of the supply air stream 98 via thermal heat transfer with the refrigerant. Thereafter, the vapor refrigerant exits the evaporator 80 and returns to the compressor 74 by a suction line to complete the cycle.

In some embodiments, the vapor compression system 72 may further include a reheat coil in addition to the evaporator 80. For example, the reheat coil may be positioned downstream of the evaporator relative to the supply air stream 98 and may reheat the supply air stream 98 when the supply air stream 98 is overcooled to remove humidity from the supply air stream 98 before the supply air stream 98 is directed to the building 10 or the residence 52.

It should be appreciated that any of the features described herein may be incorporated with the HVAC unit, the residential heating and cooling system 50, or other HVAC systems. Additionally, while the features disclosed herein are described in the context of embodiments that directly heat and cool a supply air stream provided to a building or other load, embodiments of the present disclosure may be applicable to other HVAC systems as well. For example, the features described herein may be applied to mechanical cooling systems, free cooling systems, chiller systems, or other heat pump or refrigeration applications.

As set forth above, embodiments of the present disclosure are directed to a passive charge management system of the HVAC unit 12, the residential heating and cooling system 50, and/or the vapor compression system 72, any of which may referred to as an HVAC system 100. For example, FIGS. 5 and 6 are embodiments of a heat pump system 102 of the HVAC system 100 and of an air conditioning system 103 of the HVAC system 100, respectively, which may utilize a passive charge vessel 105 to passively manage the charge level of the HVAC system 100.

To illustrate, the following discussion focuses on FIG. 5, which is a schematic representation of the heat pump system 102 of the HVAC system 100. In certain embodiments, the heat pump system 102 may include a reversing valve 106, such as a four-way valve. Thus, the HVAC system 100 may include the indoor HVAC unit 56 having the heat exchanger 62 discussed above, such as an indoor heat exchanger 108, and the outdoor HVAC unit 58 having the heat exchanger 60 discussed above, such as an outdoor heat exchanger 110. A compressor, such as the compressor 74 discussed above, along with the reversing valve 106, may be selectively actuated to drive refrigerant through a refrigerant circuit 112 in a first direction 120. Similarly, the compressor 74 and the reversing valve 106 may be selectively actuated to drive refrigerant through the refrigerant circuit 112 in a second direction 122, opposite of the first direction 120.

Under conditions in which the refrigerant flows from the indoor heat exchanger 108 to the outdoor heat exchanger 110 in the first direction 120, the HVAC system 100 may activate the fan 64 to evaporate refrigerant within the outdoor heat exchanger 110 and activate the blower 66 to pass air over the indoor heat exchanger 108, which condenses the refrigerant. Thus, the air passing over the indoor heat exchanger 108 is heated and provided to an interior space of the building 10 or residence 52. When the refrigerant flows in the second direction 122 from the outdoor heat exchanger 110 to the indoor heat exchanger 108, the indoor heat exchanger 108 alternatively operates as an evaporator, thus enabling the HVAC system 100 provide cooled air to the interior space of the building 10 or residence 52. Moreover, an expansion valve, such as the expansion device 78, is shown between the indoor heat exchanger 108 and the outdoor heat exchanger 110. Particularly, a first expansion device 124 may be utilized while the refrigerant is flowing in the first direction 120 and a second expansion device 126 may be utilized while the refrigerant is flowing in the second direction 122. The first and second expansion devices 124, 126 may also utilize a first one-way valve 128 and a second one-way valve 130, respectively, depending on a direction of flow of the refrigerant through the heat pump system 102. For example, when the refrigerant flows in the first direction 120, the refrigerant may flow through the second one-way valve 130 and through the first expansion device 124. When the refrigerant flows in the second direction 122, the refrigerant may flow through the first one-way valve 128 and through the second expansion device 126.

The following discussion focuses on FIG. 6, which is a schematic view of an embodiment of the air conditioning system 103 of an embodiment of the HVAC system 100. The air conditioning system 103 may function in a manner similar to the heat pump system 102 when the refrigerant within the heat pump system 102 flows in the second direction 122 and/or to the vapor compression system 72 of FIG. 4. That is, the air conditioning system 103 may utilize the outdoor heat exchanger 110, the expansion device 78, the indoor heat exchanger 108, and the compressor 74. For example, the compressor 74 may compress the refrigerant and deliver it to the outdoor heat exchanger 110, which functions as a condenser. Indeed, the outdoor heat exchanger 110 may condense the refrigerant to a liquid state. From the outdoor heat exchanger 110, the refrigerant may flow through the expansion device 78 to the indoor heat exchanger 108, which functions as an evaporator. Indeed, the refrigerant may undergo a phase change from a liquid state to a vaporous state as the refrigerant flows through the indoor heat exchanger 108. From the indoor heat exchanger 108, the refrigerant may flow to the compressor 74 to continue through the refrigerant circuit 112.

Further, in both FIGS. 5 and 6, the HVAC system 100 includes the charge vessel 105 configured to accept varying amounts of refrigerant, or charge, from the HVAC system 100, depending at least in part on a pressure of the refrigerant within the HVAC system 100. First, it should be noted that a charge level of refrigerant may refer to the quantity of refrigerant within a system. Further, an optimum, desired, or target charge level of the HVAC system 100 may depend on various conditions of the HVAC system 100, such as ambient temperatures and/or a mode of the HVAC system 100. Indeed, as mentioned above, an efficiency of the HVAC system 100 may benefit from having a decreased charge level when the ambient temperature is high and may benefit from having an increased charge level when the ambient temperature is low. Moreover, a discharge pressure of the HVAC system 100 may be affected by the ambient temperatures. As used herein, the discharge pressure may refer to the pressure of the refrigerant in the refrigerant circuit 112 after being discharged from the compressor 74. Further, it is to be understood that the discharge pressure of the condenser 74 may be positively correlated to refrigerant pressures throughout the refrigerant circuit 112 before the expansion device. Therefore, discussions of trends, such as increases or decreases, of the discharge pressure from the compressor 74 may also refer to corresponding trends of pressures throughout the refrigerant circuit 112 before the expansion device, and more specifically, to refrigerant pressures located downstream of the condensing heat exchanger, where the charge vessel 105 may be fluidly coupled. Indeed, it is to be further understood that, in certain embodiments, the discharge pressure may refer to the pressure downstream of the condensing heat exchanger.

In the heat pump system 102, the outdoor heat exchanger 110 may function as the condensing heat exchanger when the refrigerant is flowing in the second direction 122. Correspondingly, the indoor heat exchanger 108 may function as a condensing heat exchanger when the refrigerant is flowing in the first direction 120. Further, in the air conditioning system 103, the outdoor heat exchanger 110 may always function as a condensing heat exchanger while the air conditioning system 103 is in operation. In certain embodiments, the charge vessel 105 may be located within the outdoor HVAC unit 58 when the HVAC system 100 is a split HVAC system, such as the system shown in FIG. 3.

When the ambient temperature is high, the discharge pressure of the HVAC system 100 may increase. Similarly, when ambient temperatures are low, the discharge pressure of the HVAC system 100 may decrease. For example, as discussed above, when the ambient temperature increases, excess refrigerant may gather at the condensing heat exchanger, and the HVAC system 100 may increase a power input to the compressor 74, thereby increasing the discharge pressure. Similarly, when the ambient temperature decreases, the condensing heat exchanger may output an incomplete column of liquid refrigerant, thereby decreasing discharge pressure. Indeed, the HVAC system 100 may benefit from a decreased charge level when the ambient temperature is high and may benefit from an increased charge level when the ambient temperature are low. Therefore, the charge vessel 105 is configured to remove refrigerant charge from the refrigerant circuit when the discharge pressure is high and to add refrigerant charge when the discharge pressure is low.

To this end, the charge vessel 105 is divided into a first section 142, which contains a compressible fluid, and a second section 144, which is in fluid communication with the liquid refrigerant of the refrigerant loop 112. The first section 142 may be fluidly isolated from the second section 144 and may contain a pre-determined amount of a compressible fluid, such as an inert gas. Indeed, the first section 142 may include nitrogen, helium, neon, argon, any combination thereof, or any other suitable compressible fluid. The first section 142 and the second section 144 may be separated by a divider 146, such as a bladder, a membrane, and/or a diaphragm. Therefore, as the discharge pressure of the HVAC system 100 increases, the charge vessel 105 may accept an increased amount of refrigerant, or charge, into the second section 144.

The pressures of first section 142 and the second section 144 are substantially in equilibrium while the volumes of the first section 142 and the second section 144 are inversely related. To elaborate, as the discharge pressure increases, the pressure within the second section 144 correspondingly increases, thereby flexing the divider 146 to increase a volume of the second section 144. As a result, a volume of the first section 142 decreases, which increases a pressure of the first section 142 to substantially match the pressure within the second section 144. Similarly, as the discharge pressure decreases, the pressure within the second section 144 correspondingly decreases, thereby flexing the divider 146 to decrease a volume of the second section 144. Thus, a volume of the first section 142 increases, which decreases a pressure of the first section 142 to substantially match the pressure within the first section 144.

To help illustrate, FIGS. 7 and 8 are schematic diagrams of a cross section of the charge vessel 105 when the discharge pressure is high and when the discharge pressure is low, respectively. As discussed herein, the charge vessel 105 may passively manage the charge within the refrigerant loop 112 of the HVAC system 100. In other words, the charge vessel 105 may add or withdraw charge from the HVAC system 100 in direct response to, or as a direct result of, a changing discharge pressure within the HVAC system 100. Indeed, the amount of refrigerant added or withdrawn from the system may be directly proportional to the discharge pressure. For example, as discussed above, as the discharge pressure increases, the amount of refrigerant contained within the second section 144 may proportionally increase. Similarly, as the discharge pressure decreases, the amount of refrigerant contained within the second section 144 may proportionally decrease. Further, it should be understood that, in some embodiments, the amount of refrigerant added or withdrawn from the HVAC system 100 or charge vessel 105 may also be at least partially dependent on an elasticity of the divider 146.

As shown, the first and section sections 142, 144 may be contained within a rigid outer shell 150 and are separated by the divider 146. In certain embodiments, the compressible fluid contained within the first section 142 may be completely encapsulated by the divider 146. That is, the divider 146 may function as an elastic sac/bladder that lines the interior surface of the first section 142 of the charge vessel 105. In some embodiments, the compressible fluid of the first section 142 may be contained by, and in contact with, both an interior surface of the charge vessel 105, such as an interior surface of the shell 150, and the divider 146. For example, in such embodiments, the divider 146 may be coupled to the interior surface of the charge vessel 105 along a line 152.

Further, the charge vessel 105 may be in fluid communication with the refrigerant loop of the HVAC system 100 via a conduit 154. More specifically, the conduit 154 may fluidly couple the charge vessel 105 to a liquid refrigerant portion 155 of the refrigerant loop 112, which may substantially contain liquid refrigerant due at least in part to its downstream position relative to the condensing heat exchanger. To this end, the charge vessel 105 may be configured to accept refrigerant that is substantially in the liquid phase. In this manner, the charge vessel 105 is configured to accept a greater mass of refrigerant than if the charge vessel 105 was in fluid communication with a portion of the HVAC system 100 containing vapor refrigerant. In some embodiments, the conduit 154 may be coupled to a corresponding conduit of the refrigerant circuit 112 at a bottom of the corresponding conduit. Therefore, the charge vessel 105 may receive less vapor refrigerant in embodiments where vapor refrigerant is present because the liquid refrigerant may tend to be disposed lower in the corresponding conduit, as liquid refrigerant is denser than vapor refrigerant. In some embodiments, the charge vessel 105 is configured to hold approximately 10 to 20% of the total charge of the HVAC system 100. In some embodiments, the charge vessel 105 is configured to hold approximately 1 to 2 pounds of refrigerant.

In certain embodiments, the conduit 154 may include a valve 156, such as a shut-off valve, which may close to separate the charge vessel 105 from the refrigerant circuit 112. Further, in some embodiments, the charge vessel 105 may include a pressure sensor 160 configured to measure/detect/determine a pressure within the charge vessel 105, and more specifically, within the first section 142 and/or the second section 144. The valve 156 and the pressure sensor 160 may be communicatively coupled to a controller 162, such as the control panel 82. The controller 162 may include a processor 164, which may represent one or more processors, such as an application-specific processor. The controller 162 may also include a memory device 166 for storing instructions executable by the processor 166 to perform the methods and control actions described herein for the HVAC system 100. The processor 164 may include one or more processing devices, and the memory 166 may include one or more tangible, non-transitory, machine-readable media. By way of example, such machine-readable media can include RAM, ROM, EPROM, EEPROM, CD-ROM, or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to carry or store desired program code in the form of machine-executable instructions or data structures and which can be accessed by the processor 164 or by any general purpose or special purpose computer or other machine with a processor. In certain embodiments, the controller 162 may keep the valve 156 open while the pressure of the charge vessel 105 is within a minimum and maximum threshold pressure range. That is, if the pressure of the charge vessel 105 exceeds the maximum threshold or falls below the minimum threshold, the controller 162 may actuate the valve 156 to seal the charge vessel 105 from the refrigerant circuit 112 of the HVAC system 100.

Accordingly, the present disclosure is directed to providing systems and methods for passive refrigerant charge management. Particularly, heating, ventilation, and air conditioning (HVAC) systems may include a charge vessel fluidly coupled to the refrigerant circuit of the HVAC system. The charge vessel includes a first portion having a compressible fluid and a second portion fluidly coupled with the refrigerant circuit and configured to accept various amounts of refrigerant in response to a pressure within the refrigerant circuit to increase an efficiency of the HVAC system. The pressure of the refrigerant within the refrigerant circuit may depend on an ambient temperature of the HVAC system. Keeping this in mind, as the ambient temperature changes, the optimal, target, or desired charge level of the HVAC system may also change. Particularly, as the ambient temperature increases, the desired charge level may decrease and as the ambient temperature decreases, the desired charge level may increase. Therefore, the charge vessel is configured to increase efficiency of the HVAC system by automatically removing refrigerant charge from the refrigerant circuit as the ambient temperature increases and by automatically adding refrigerant charge to the refrigerant circuit as the ambient temperature decreases.

While only certain features and embodiments of the present disclosure have been illustrated and described, many modifications and changes may occur to those skilled in the art, such as variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, such as temperatures or pressures, mounting arrangements, use of materials, colors, orientations, and so forth, without materially departing from the novel teachings and advantages of the subject matter recited in the claims. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the present disclosure. Furthermore, in an effort to provide a concise description of the exemplary embodiments, all features of an actual implementation may not have been described, such as those unrelated to the presently contemplated best mode of carrying out the present disclosure, or those unrelated to enabling the claimed embodiments. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation specific decisions may be made. Such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure, without undue experimentation.

REFRIGERANT CHARGE MANAGEMENT SYSTEMS AND METHODS

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