System and method for non-pressurized closed loop water subsystems for heating, ventilation, and air conditioning systems

Abstract

A heating, ventilation, and air conditioning system includes a first fluid and a second fluid, a heat exchanger, a refrigerant subsystem, and at least one closed loop subsystem. The heat exchanger includes a membrane for directing the first fluid through the heat exchanger and is configured for heat transfer between the first fluid and the second fluid. The membrane defines an inlet having an inlet height relative to a reference level. The closed loop subsystem transfers heat from the heat exchanger to the refrigerant subsystem and includes an expansion tank containing the first fluid. A liquid level of the first fluid within the expansion tank has a liquid level height relative to the reference level. The expansion tank is positioned relative to the heat exchanger such that the inlet height is greater than the liquid level height and the membrane is maintained in a collapsed configuration.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. nonprovisional patent application No. 17 / 033,416, filed on September 25, 2020, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] The field of this disclosure generally relates to heating, ventilation and air conditioning systems, and more specifically, to systems and methods for non-pressurized closed-loop water subsystems used in heating, ventilation and air conditioning systems. Background Technology

[0004] Heating, ventilation, and air conditioning (HVAC) systems can include multiple subsystems that enhance the heating, cooling, and moisture removal capabilities of the HVAC system. For example, an HVAC system may include a refrigerant subsystem, a hot water subsystem, and a chilled water subsystem, improving the system's efficiency. Furthermore, an HVAC system may include a heat exchanger with a membrane guiding the flow of heat exchange fluids through it. The heat exchanger enables the HVAC system to exchange heat between multiple heat exchange fluids simultaneously. To maintain a predetermined amount of heat transfer between the heat exchange fluids, the membrane remains in a contracted configuration. Specifically, the hot water and chilled water subsystems are open, unpressurized systems to maintain the membrane in a contracted configuration. However, contaminants can enter the hot water and chilled water subsystems, reducing their efficiency because they are open systems. Improvements to the system and related methods are needed.

[0005] This background section is intended to introduce the reader to various aspects of the art that may relate to the aspects described below and / or claimed in this disclosure. This discussion is intended to help provide the reader with background information in order to better understand the various aspects of this disclosure. Therefore, it should be understood that these statements are to be understood from this perspective and not as an admission of prior art. Summary of the Invention

[0006] In one aspect, a heating, ventilation, and air conditioning system includes a first fluid and a second fluid, a heat exchanger, a refrigerant subsystem, and at least one closed-loop subsystem. The heat exchanger includes a membrane for guiding the first fluid through the heat exchanger and is configured for heat transfer between the first fluid and the second fluid. The membrane defines an inlet having an inlet height relative to a reference horizontal plane. The closed-loop subsystem transfers heat from the heat exchanger to the refrigerant subsystem and includes an expansion tank containing the first fluid. The level of the first fluid within the expansion tank has a level height relative to the reference horizontal plane. The expansion tank is positioned relative to the heat exchanger such that the inlet height is greater than the level height, and the membrane remains in a contracted configuration.

[0007] In another aspect, a closed-loop subsystem for a heating, ventilation, and air conditioning system comprising a first fluid and a second fluid includes a heat exchanger and an expansion tank. The heat exchanger includes a membrane for guiding the first fluid through the heat exchanger. The membrane is configured for heat transfer between the first fluid and the second fluid. The membrane defines an inlet having an inlet height relative to a reference horizontal plane. The expansion tank contains the first fluid. The level of the first fluid within the expansion tank has a level height relative to the reference horizontal plane. The expansion tank is positioned relative to the heat exchanger such that the inlet height is greater than the level height, and the membrane remains in a contracted configuration.

[0008] In another aspect, a method of transferring heat from a refrigerant circuit of a heating, ventilation, and air conditioning (HVAC) system to a heat exchanger of the HVAC system using a closed-loop subsystem includes guiding a first fluid from a membrane of the heat exchanger to an expansion tank. The HVAC system includes a first fluid and a second fluid, the subsystem includes an expansion tank, and the heat exchanger includes a membrane. The membrane defines an inlet having an inlet height relative to a reference level. The level of the first fluid within the expansion tank has a level height relative to the reference level. The method also includes guiding the first fluid from the expansion tank to the membrane. The expansion tank is positioned relative to the heat exchanger such that the inlet height is greater than the level height, and the membrane remains in a contracted configuration. The method also includes using the membrane to exchange heat from the first fluid to the second fluid.

[0009] Various improvements exist to the features mentioned in the foregoing aspects. Other features may also be incorporated into the foregoing aspects. These improvements and additional features may exist individually or in any combination. For example, the various features discussed below with respect to any embodiment of the illustrated embodiments may be incorporated individually or in any combination into any aspect of the foregoing aspects. Attached Figure Description

[0010] Figure 1 It is a schematic flowchart of a heating, ventilation, and air conditioning (HVAC) system.

[0011] Figure 2yes Figure 1 An exemplary flowchart of the hot water subsystem is shown.

[0012] Figure 3 yes Figure 2 The diagram shows the first expansion tank and the second heat exchanger.

[0013] Figure 4 yes Figure 1 The diagram shows a schematic flow chart of the cold water subsystem.

[0014] Figure 5 Is using Figure 2 and Figure 4 The flowchart shown illustrates a method by which a closed-loop water subsystem transfers heat from a refrigerant loop to a heat exchanger.

[0015] Throughout the accompanying drawings, corresponding reference numerals denote the respective parts. Detailed Implementation

[0016] Figure 1 This is a schematic flow diagram of a heating, ventilation, and air conditioning (HVAC) system 100. While the HVAC system 100 can be any type of HVAC system, it is more efficient than existing HVAC systems because it includes subsystems 102-110 that improve the heating, cooling, and moisture removal capabilities of the system 100 compared to existing systems. Specifically, the HVAC system 100 includes a refrigerant subsystem 102, two water subsystems 104 and 106, a conditioning subsystem 108, and a regeneration subsystem 110. Water subsystems 104 and 106 include a hot water subsystem 104 and a cold water subsystem 106. The conditioning subsystem 108 removes heat and moisture from the flow of conditioned inlet air 112 and directs the flow of conditioned outlet air 114 to a structure or vehicle (not shown). The flow of regulated outlet air 114 has a lower temperature and humidity than the flow of regulated inlet air 112 because the regulating subsystem 108 has removed heat and moisture from the air. Subsystems 102-110 transfer heat and moisture from the regulating subsystem 108 to the regeneration subsystem 110. The regeneration subsystem 110 transfers heat and moisture to the flow of regeneration inlet air 116 and directs the flow of regeneration outlet air 118 into the atmosphere.

[0017] The regulating subsystem 108 shares a first heat exchanger 120 with the chilled water subsystem 106 and the regeneration subsystem 110, and is connected to the chilled water subsystem and the regeneration subsystem via the first heat exchanger. In this embodiment, the first heat exchanger 120 is a three-way heat exchanger that transfers heat from the flow of regulating inlet air 112 to a first fluid flow, and transfers heat and moisture from the flow of regulating inlet air 112 to a second fluid flow. The first heat exchanger 120 includes a moisture film (not shown) that allows both heat and moisture to be transferred from the flow of regulating inlet air 112 to the second fluid flow, and a membrane 122 that guides the first fluid flow through the first heat exchanger 120 and transfers heat from the flow of regulating inlet air 112 to the second fluid flow. In the illustrated embodiment, the first fluid flow is a water flow circulated by the chilled water subsystem 106, and the second fluid flow is a liquid desiccant flow circulated by the regulating subsystem 108 and the regeneration subsystem 110. In an alternative embodiment, the first fluid can be any fluid that enables the regulating subsystem 108 and the chilled water subsystem 106 to operate as described herein, and the second fluid can be any fluid that enables the regulating subsystem 108 and the regeneration subsystem 110 to operate as described herein. As described below, the chilled water subsystem 106 is a non-pressurized closed-loop subsystem that enables the first heat exchanger 120 to include non-pressurized elements, allowing the first heat exchanger to exchange heat between the regulating inlet air 112 flow, the first fluid flow, and the second fluid flow.

[0018] The chilled water subsystem 106 shares a first heat exchanger 120 with the regulating subsystem 108 and an evaporator 124 with the refrigerant subsystem 102. As described below, the chilled water subsystem 106 transfers heat from the first heat exchanger 120 to the evaporator 124 or to the atmosphere. More specifically, the chilled water subsystem 106 may include additional heat transfer devices to transfer heat to the atmosphere. Residual heat is transferred to the refrigerant subsystem 102 via the evaporator 124. Furthermore, the chilled water subsystem 106 is a non-pressurized closed system, which prevents materials from the surrounding environment from entering the subsystem, thereby preventing contaminants from entering and contaminating the subsystem. As used herein, non-pressurized means the subsystem operates at 5 pounds per square inch (psig) or less.

[0019] The refrigerant subsystem 102 shares an evaporator 124 with the chilled water subsystem 106 and a condenser 126 with the hot water subsystem 104. The refrigerant subsystem 102 may also include an expansion valve (not shown) and a compressor (not shown). The refrigerant subsystem 102 transfers heat from the evaporator 124 to the condenser 126, and the condenser 126 transfers heat to the hot water subsystem 104. Specifically, the refrigerant subsystem 102 directs a third fluid flow from the evaporator 124 to the condenser 126, and the third fluid transfers heat from the evaporator 124 to the condenser 126. In this embodiment, the third fluid is a refrigerant. In alternative embodiments, the third fluid may be any fluid that enables the refrigerant subsystem 102 to operate as described herein.

[0020] The hot water subsystem 104 shares a second heat exchanger 128 with the regeneration subsystem 110 and a condenser 126 with the refrigerant subsystem 102. As described below, the hot water subsystem 104 transfers heat from the condenser 126 to the second heat exchanger 128 or to the atmosphere. More specifically, the hot water subsystem 104 may include additional heat transfer devices to transfer heat to the atmosphere. Residual heat is transferred to the regeneration subsystem 110 via the second heat exchanger 128. Furthermore, the hot water subsystem 104 is a non-pressurized closed system, which prevents materials from the surrounding environment from entering the subsystem, thereby preventing contaminants from entering and contaminating the subsystem. As used herein, non-pressurized means the subsystem operates at 5 psig or less.

[0021] The regeneration subsystem 110 shares a second heat exchanger 128 with and engages with the hot water subsystem 104 and the regulation subsystem 108 via the second heat exchanger. In this embodiment, the second heat exchanger 128 is a three-way heat exchanger that transfers heat from a first fluid flow to a flow of regeneration inlet air 116, and transfers both heat and moisture from a second fluid flow to a flow of regeneration inlet air 116. The second heat exchanger 128 includes a moisture film (not shown) that allows both heat and moisture to be transferred from the second fluid flow to the flow of regeneration inlet air 116, and a membrane 122 that guides the first fluid flow through the second heat exchanger 128 and transfers heat from the first fluid flow to the flow of regeneration inlet air 116 and the second fluid flow. In the illustrated embodiment, the first fluid flow is a water flow circulated by the hot water subsystem 104, and the second fluid flow is a liquid desiccant flow circulated by the regulation subsystem 108 and the regeneration subsystem 110. In an alternative embodiment, the first fluid can be any fluid that enables the regeneration subsystem 110 and the hot water subsystem 104 to operate as described herein, and the second fluid can be any fluid that enables the regeneration subsystem 110 and the regulating subsystem 108 to operate as described herein. As described below, the hot water subsystem 104 is a non-pressurized closed-loop subsystem that enables the second heat exchanger 128 to include non-pressurized elements, allowing the second heat exchanger to exchange heat between the flow of regeneration inlet air 116, the first fluid flow, and the second fluid flow.

[0022] Still refer to Figure 1The first heat exchanger 120 and the second heat exchanger 128 are substantially the same. In an alternative embodiment, the first heat exchanger 120 and the second heat exchanger 128 are different. Specifically, in this embodiment, both the first heat exchanger 120 and the second heat exchanger 128 include a membrane 122 for guiding a first fluid flow through the heat exchanger and for exchanging heat between the first fluid, the second fluid, and the air flow. In one embodiment, the membrane 122 is a non-rigid, flexible material that allows heat to be transferred into and out of the first fluid while preventing the first fluid from mixing with any other fluid, including the second fluid and the air flow. Specifically, the membrane 122 is a non-rigid, flexible material designed to operate without pressure (at 5 psig or less) and not designed to operate at considerable pressure (e.g., 10 psig). More specifically, in this embodiment, membrane 122 comprises a bladder or polymer bag that allows heat transfer to and from the first fluid while preventing the first fluid from mixing with any other fluid, including the second fluid and airflow, and operates at 5 psig or less. Membrane 122 is flexible because the material forming the membrane can bend without breaking, and the membrane is non-rigid because it can change size and shape without breaking. As described below, in this embodiment, membrane 122 is flexible and non-rigid because the membrane remains in a contracted configuration. In alternative embodiments, membrane 122 is formed of any material and has any degree of flexibility and rigidity that enables the first heat exchanger 120 and the second heat exchanger 128 to operate as described herein.

[0023] Membrane 122 is filled with a first fluid and positioned close to a second fluid and airflow within the first heat exchanger 120 and the second heat exchanger 128. In some embodiments, membrane 122 is in physical contact with at least one of the second fluid and airflow to facilitate enhanced heat transfer between the first fluid, the second fluid, and the airflow. For example, membrane 122 may be immersed in the second fluid flow and / or the airflow to facilitate enhanced heat transfer between the first fluid, the second fluid, and the airflow. The first heat exchanger 120 and the second heat exchanger 128 are non-pressurized heat exchangers because they include a non-pressurized element (membrane 122), and portions of the heat exchangers are designed to be non-pressurized (operating at 5 psig or below).

[0024] To facilitate enhanced heat transfer between the first fluid, the second fluid, and the airflow, membrane 122 is maintained in a contracted configuration during operation of the first heat exchanger 120 and the second heat exchanger 128. The contracted configuration increases the surface area to volume ratio of membrane 122, increases the heat transfer coefficient, and enhances the overall heat transfer between the first fluid, the second fluid, and the airflow. If membrane 122 is filled with the first fluid, causing it to expand like a balloon, a portion of the first fluid inside the balloon-shaped membrane is not close to the second fluid and / or the airflow, thus reducing heat exchange between the internal portion of the first fluid and the second fluid and / or the airflow. However, if membrane 122 is maintained in a contracted configuration, all of the first fluid within the membrane is close to the second fluid and / or the airflow, thereby increasing heat exchange between the first fluid and the second fluid and / or the airflow. As described below, water subsystems 104 and 106 are arranged and operated to maintain membrane 122 in a contracted configuration. More specifically, water subsystems 104 and 106 are arranged and operated as unpressurized systems to maintain negative pressure at the inlets 130 of the first heat exchanger 120 and the second heat exchanger 128, thereby keeping the membrane 122 in a contracted configuration.

[0025] Figure 2 This is a schematic flow diagram of the hot water subsystem 104. The hot water subsystem 104 includes a second heat exchanger 128, a condenser 126, a first pump 132, a first air-to-first fluid heat exchanger 134, a second air-to-first fluid heat exchanger 136, a first air inlet 138, and a first expansion tank 140. In this embodiment, the first pump 132 is a centrifugal pump that receives a first fluid flow from the second heat exchanger 128 and pumps the first fluid to the condenser 126, the first air-to-first fluid heat exchanger 134, the second air-to-first fluid heat exchanger 136, the first air inlet 138, and the first expansion tank 140. However, in alternative embodiments, the pump 136 can be any type of pump that enables the hot water subsystem 104 to operate as described herein. Furthermore, the first air-to-first fluid heat exchanger 134 and the second air-to-first fluid heat exchanger 136 can be any type of heat exchanger that transfers heat from the first fluid to the air flow.

[0026] In the illustrated embodiment, the first air inlet 138 is an air eliminator located downstream of the condenser 126, the first air-to-first fluid heat exchanger 134, and the second air-to-first fluid heat exchanger 136. Air may be entrained in the first fluid (water), and this entrained air can cause operational problems with the heat exchangers 128, 134, and 136, as well as the first pump 132. The first air inlet 138 removes entrained air from the first fluid, thereby improving the operation of the hot water subsystem 104. Additionally, the first air inlet 138 is coupled to the first expansion tank 140 and includes an inlet that allows an operator to add or fill the hot water subsystem 104 with the first fluid.

[0027] Figure 3 This is a schematic diagram of a first expansion tank 140 and a second heat exchanger 128, showing the position of the first expansion tank relative to the second heat exchanger. The first expansion tank 140 includes a housing 142 and a bladder 144 positioned within the housing. The bladder 144 includes a flexible bladder or polymer bag containing a first fluid. The housing 142 defines an orifice 146 that allows fluid communication between the interior 148 of the housing and the atmosphere. The orifice 146 maintains the interior 148 of the housing 142 at atmospheric pressure. Furthermore, because the bladder 144 is flexible, the bladder and the first fluid within it are also maintained at atmospheric pressure. Additionally, the housing 142 has a width 150 and a length 152 that maintains the level 154 of the first fluid within the bladder within a predetermined range 156. Specifically, the width 150 and length 152 are determined such that changes in the volume of the first fluid within the hot water subsystem 104 due to temperature variations do not cause the level 154 of the first fluid within the bladder to exceed or fall below the predetermined range 156.

[0028] like Figure 3 As shown, the inlet 130 of the second heat exchanger 128 is positioned at an inlet height 158 ​​relative to a reference level 160, and a predetermined range 156 is positioned at a range height 162 relative to the reference level 160. The inlet height 158 ​​is greater than the range height 162, such that the inlet 130 of the second heat exchanger 128 is maintained above (or higher than) the level 154 of the first fluid within the capsule 144. That is, the range height 162 is less than the inlet height 158, such that the level 154 of the first fluid within the capsule 144 is maintained below (or lower than) the inlet 130 of the second heat exchanger 128. Furthermore, the first fluid is guided from the capsule 144 to the membrane 122. Because the level 154 of the first fluid within the capsule 144 is maintained below (or lower than) the inlet 130 of the second heat exchanger 128, the pressure at the inlet of the second heat exchanger remains negative. The negative pressure causes the membrane 122 to contract into a contracted configuration, thereby increasing the heat transfer coefficient and the overall heat transfer between the first fluid, the second fluid, and the airflow. Therefore, the relative positions of the first expansion tank 140 and the second heat exchanger 128 keep the membrane 122 in a contracted configuration. More specifically, the relative position of the first fluid level 154 within the capsule 144 and the inlet 130 of the second heat exchanger 128 maintains the pressure at the inlet of the second heat exchanger under negative pressure, thus keeping the membrane 122 in a contracted configuration. Furthermore, the capsule 144 allows the hot water subsystem 104 to be a non-pressurized closed system, while simultaneously allowing the first fluid within the capsule to be maintained at atmospheric pressure.

[0029] The orifice 146 maintains the first fluid within the capsule 144 at atmospheric pressure, and the capsule 144 prevents contaminants from entering the hot water subsystem 104 while allowing the first fluid within the capsule to remain at atmospheric pressure. The combination of the arrangement of the capsule 144, orifice 146, and inlet height 158 ​​relative to the level 154 of the first fluid within the capsule 144 enables the hot water subsystem 104 to maintain the pressure at the inlet 130 of the second heat exchanger 128 at a negative pressure. This negative pressure at the inlet 130 of the second heat exchanger 128 allows the membrane 122 to remain in a contracted configuration and enables the second heat exchanger 128 to include non-pressurized elements. The combination of the arrangement of the capsule 144, orifice 146, and inlet height 158 ​​relative to the level 154 of the first fluid within the capsule 144 enables the hot water subsystem 104 to maintain the pressure at the inlet 130 of the second heat exchanger 128 at a negative pressure, thereby allowing non-pressurized elements to be included within the second heat exchanger 128. Furthermore, by keeping the inlet 130 of the second heat exchanger 128 under negative pressure, the membrane 122 is kept in a contracted configuration, thereby increasing the surface area to volume ratio of the membrane, increasing the heat transfer coefficient, and increasing the overall heat transfer between the first fluid, the second fluid, and the air flow.

[0030] In an alternative embodiment, the hot water subsystem 104 includes additional equipment to maintain the inlet 130 of the second heat exchanger 128 under negative pressure, instead of arranging the second heat exchanger 128 and the first expansion tank 140 to maintain the membrane 122 in a contracted configuration. For example, the hot water subsystem 104 may include a fluid power device (e.g., a pump) or piping fitting (e.g., an orifice plate) to maintain the inlet 130 of the second heat exchanger 128 under negative pressure. The hot water subsystem 104 may include any equipment that allows the subsystem to be a closed system while still maintaining the inlet 130 of the second heat exchanger 128 under negative pressure.

[0031] Figure 4 This is a schematic flow diagram of the chilled water subsystem 106. The chilled water subsystem 106 includes a first heat exchanger 120, an evaporator 124, a second pump 164, a third air-to-first fluid heat exchanger 166, a fourth air-to-first fluid heat exchanger 168, a second air inlet 170, and a second expansion tank 172. The chilled water subsystem 106 operates in a manner substantially similar to that of the hot water subsystem 104. Specifically, the chilled water subsystem 106 is a closed system, and the second expansion tank 172 and the first heat exchanger 120 are arranged as described above to maintain the membrane 122 in the first heat exchanger 120 in a contracted configuration.

[0032] Figure 5This is a flowchart of method 200 for transferring heat from the refrigerant loop of an HVAC system to a heat exchanger of an HVAC system using a closed-loop water subsystem. The subsystem includes an expansion tank, and the heat exchanger includes a membrane. Method 200 includes guiding a first fluid from the membrane of the heat exchanger 202 to the expansion tank. Method 200 also includes guiding the first fluid from the expansion tank 204 to the membrane. The expansion tank is positioned relative to the heat exchanger such that the level of the first fluid within the expansion tank is positioned below the inlet of the first fluid in the heat exchanger. The position of the first fluid level in the expansion tank relative to the inlet of the heat exchanger keeps the membrane in a contracted configuration. Method 200 also includes using the membrane to exchange heat from the first fluid 206 to a second fluid.

[0033] The HVAC system described herein includes multiple subsystems for removing heat and moisture from an airflow. Specifically, the HVAC system includes a refrigerant subsystem, a hot water subsystem, and a chilled water subsystem, which improves the efficiency of the HVAC system. The hot water and chilled water subsystems are non-pressurized closed systems to prevent contaminants from entering the subsystems. The HVAC system also includes a heat exchanger having a membrane that guides the flow of heat exchange fluids through the heat exchanger. The heat exchanger enables the HVAC system to exchange heat between multiple heat exchange fluids simultaneously. To maintain a predetermined amount of heat transfer between the heat exchange fluids, the membrane remains in a contracted configuration. Devices within the hot water and chilled water subsystems are arranged to maintain the membrane in a contracted configuration. Specifically, each of the hot water and chilled water subsystems includes an expansion tank comprising a shell and a bladder. The shell defines an orifice that exposes the interior of the shell and the bladder to the environment and maintains the fluid within the bladder at atmospheric pressure. The bladder prevents contaminants from entering the system, thereby closing the subsystem while allowing the fluid within the bladder to remain at atmospheric pressure. The housing is sized and shaped to maintain the fluid level within the bladder within a predetermined range. The expansion tank and heat exchanger are positioned such that the membrane inlet is positioned above a predetermined range. Therefore, the membrane inlet is maintained under negative pressure, and the membrane remains in a contracted configuration. Thus, the HVAC system described herein includes a non-pressurized, closed subsystem that also maintains the membrane in a contracted configuration.

[0034] The exemplary implementations of HVAC systems and operating methods have been described in detail above. The systems and methods are not limited to the specific implementations described herein; rather, components of the systems and methods can be used independently and separately from other components described herein. For example, the systems described herein can be used in systems other than HVAC systems.

[0035] When elements are introduced in this disclosure or in embodiments thereof, the articles “a,” “an,” “the,” and “the” are intended to indicate the presence of one or more of the elements. The terms “comprising,” “including,” “containing,” and “having” are intended to be inclusive and mean that additional elements may be present in addition to the listed elements. The use of terms indicating a particular orientation (e.g., “top,” “bottom,” “side,” etc.) is for ease of description and does not require any particular orientation of the object being described.

[0036] Since various changes can be made to the above structures and methods without departing from the scope of this disclosure, it is intended that all content contained in the above description and shown in the accompanying drawings should be interpreted as illustrative rather than restrictive.

Claims

1. A heating, ventilation, and air conditioning system, the heating, ventilation, and air conditioning system comprising a first fluid and a second fluid, the heating, ventilation, and air conditioning system further comprising: A first heat exchanger includes a membrane for guiding the first fluid through the first heat exchanger, the membrane being configured for heat transfer between the first fluid and a second fluid, the membrane defining an inlet, wherein the first heat exchanger is positioned such that the inlet has an inlet height relative to a reference level. A refrigerant subsystem, the refrigerant subsystem comprising a third fluid; and At least one closed-loop subsystem, the closed-loop subsystem comprising a first fluid for transferring heat from a first heat exchanger to a second heat exchanger, the second heat exchanger for transferring heat from the first fluid to the third fluid in the refrigerant subsystem, the closed-loop subsystem comprising: An expansion tank containing the first fluid, wherein the expansion tank is positioned such that the level of the first fluid within the expansion tank has a height relative to a reference level, wherein the expansion tank is positioned relative to the first heat exchanger such that the inlet height is greater than the height, and such that the pressure at the inlet is maintained under negative pressure to keep the membrane in a contracted configuration.

2. The heating, ventilation, and air conditioning system of claim 1, wherein, The expansion tank includes a shell and a bladder-like component positioned within the shell.

3. The heating, ventilation, and air conditioning system of claim 2, wherein, The length and width of the housing are configured to maintain the liquid level of the first fluid within a predetermined range.

4. The heating, ventilation, and air conditioning system according to claim 2, wherein, The housing defines an opening that exposes the interior of the housing and the first fluid within the bladder to the environment and maintains it at atmospheric pressure.

5. The heating, ventilation, and air conditioning system according to claim 1, wherein, The membrane is a flexible membrane.

6. The heating, ventilation, and air conditioning system according to claim 1, wherein, The membrane is a non-rigid membrane.

7. A closed-loop subsystem for a heating, ventilation, and air conditioning system including a first fluid and a second fluid, said subsystem comprising: A heat exchanger including a membrane for guiding a first fluid through the heat exchanger, the membrane being configured for heat transfer between the first fluid and a second fluid, the membrane defining an inlet, wherein the heat exchanger is positioned such that the inlet has an inlet height relative to a reference horizontal plane; and An expansion tank containing the first fluid, wherein the expansion tank is positioned such that the level of the first fluid within the expansion tank has a level height relative to a reference level, wherein the expansion tank is positioned relative to the heat exchanger such that the inlet height is greater than the level height, and such that the pressure at the inlet is maintained under negative pressure to keep the membrane in a contracted configuration.

8. The subsystem according to claim 7, wherein, The expansion tank includes a shell and a bladder-like component positioned within the shell.

9. The subsystem according to claim 8, wherein, The length and width of the housing are configured to maintain the liquid level of the first fluid within a predetermined range.

10. The subsystem according to claim 8, wherein, The housing defines an opening that exposes the interior of the housing and the first fluid within the bladder to the environment and maintains it at atmospheric pressure.

11. The subsystem of claim 7 further includes an air inlet connected to the expansion tank for removing entrained air from the first fluid.

12. A method for transferring heat from a refrigerant circuit of a heating, ventilation, and air conditioning system to a heat exchanger of said heating, ventilation, and air conditioning system using a closed-loop subsystem, wherein, The heating, ventilation, and air conditioning system includes a first fluid and a second fluid, the subsystem includes an expansion tank, and the heat exchanger includes a membrane defining an inlet, the heat exchanger being positioned such that the inlet has an inlet height relative to a reference level, the expansion tank being positioned such that the level of the first fluid within the expansion tank has a level height relative to the reference level, the method comprising: The first fluid is directed from the membrane of the heat exchanger to the expansion tank; The first fluid is guided from the expansion tank to the membrane, the expansion tank being positioned relative to the heat exchanger such that the inlet height is greater than the liquid level height; Maintaining the pressure at the inlet of the membrane under negative pressure to keep the membrane in a contracted configuration; and The membrane is used to exchange heat from the first fluid to the second fluid.

13. The method according to claim 12, wherein, The subsystem further includes a condenser, and the method further includes directing the first fluid to the condenser and using the condenser to exchange heat between the first fluid and the refrigerant.

14. The method of claim 12, further comprising maintaining the pressure of the first fluid in the expansion tank at or near atmospheric pressure.

15. The method of claim 12, further comprising using an air inlet to remove entrained air from the first fluid.

16. The method of claim 12, further comprising pumping the first fluid from the membrane to the expansion tank.

Images