HVAC system with thermal storage

Abstract

A vapor compression system includes a compressor, a condenser, an expansion device, and an evaporator fluidly connected to form a closed fluid circuit having a fluid circulating therethrough. A heat storage device including a phase change material is fluidly connected to the outlet of the compressor and disposed downstream of the outlet of the compressor with respect to the flow of fluid. A storage expansion device is disposed downstream of the heat storage device and upstream of the evaporator, and the valve is adjustable between a plurality of positions to control flow of fluid from the compressor to the heat storage device.

Description

TECHNICAL FIELD

[0001] Exemplary embodiments of the present disclosure relate to the field of condensers, and more particularly, to a vapor compression system having various means for removing heat from refrigerant therein. BACKGROUND

[0002] Conventional vapor compression systems have condensers sized based on maximum load at maximum ambient temperature. However, maximum load and maximum ambient temperature do not exist at all times. Sizing a heat exchanger system for maximum heat load at continuous operating cycle for maximum expected ambient air conditions results in a condensing unit that is oversized, overweight, and overpowered for portions of the operating cycle that do not approach system limits. Furthermore, due to increased cost of electricity during peak hours, such as when ambient temperatures are highest, it is desirable to shift the operating dependency of the vapor compression cycle to off-peak hours, such as during morning and nighttime hours. SUMMARY

[0003] According to an embodiment, a vapor compression system includes a compressor, a condenser, an expansion device, and an evaporator fluidly connected to form a closed fluid loop having a fluid circulating therethrough. A thermal storage device including a phase change material is fluidly connected to an outlet of the compressor and disposed downstream of the outlet of the compressor relative to a flow of the fluid. A storage expansion device is disposed downstream of the thermal storage device and upstream of the evaporator, and a valve is adjustable between a plurality of positions to control a flow of the fluid from the compressor to the thermal storage device.

[0004] In addition to one or more of the features described above, or as an alternative. the thermal storage device and the condenser are disposed in parallel downstream of the compressor.

[0005] In addition to one or more of the features described above, or as an alternative. the condenser and the thermal storage device are each fluidly connected to the outlet of the compressor.

[0006] In addition to one or more of the features described above, or as an alternative to any of the previous embodiments, the compressor includes a first stage having a first outlet and a second stage having a second outlet. The thermal storage device is fluidly connected to and disposed downstream of the first outlet, and the condenser is fluidly connected to and disposed downstream of the second outlet.

[0007] In addition to one or more of the features described above, or as an alternative to any of the previous embodiments, the condenser is operable to receive the fluid at a first pressure, and the thermal storage device is operable to receive the fluid at a second pressure. The first pressure is greater than the second pressure.

[0008] In addition to one or more of the features described above, or as an alternative to any of the previous embodiments, the outlet of the expansion device is fluidly connected to the outlet of the storage expansion device at a location upstream of the inlet of the evaporator.

[0009] In addition to one or more of the features described above, or as an alternative to any of the previous embodiments, the phase change material is a molten salt.

[0010] In addition to one or more of the features described above, or as an alternative to any of the previous embodiments, the valve is located downstream of the compressor and upstream of the inlet of the thermal storage device.

[0011] In addition to one or more of the features described above, or as an alternative to any of the previous embodiments, the valve can be adjusted between multiple positions to minimize the condensation temperature of the fluid.

[0012] In addition to one or more of the features described above, or as an alternative to any of the previous embodiments, when the phase change temperature of the phase change material is below the ambient temperature, the valve is arranged to direct the flow of fluid from the compressor to the thermal storage device.

[0013] In addition to one or more of the features described above, or as an alternative to any of the previous embodiments, fluid is simultaneously supplied to the condenser and the thermal storage device at one of a plurality of locations.

[0014] According to an embodiment, a method of operating a vapor compression system includes: providing a compressor, a condenser, an expander, and an evaporator with fluid connections to form a closed fluid loop, the closed fluid loop having a fluid circulating through it; comparing the condensation temperature of a cooling fluid with the condensation temperature of a phase change material to determine a minimum condensation temperature; and, in response to determining the condensation temperature of the phase change material as the minimum condensation temperature, adjusting a valve to direct fluid from the compressor to a heat storage device containing the phase change material, and removing heat from the fluid via the phase change material.

[0015] In addition to one or more of the features described above, or as an alternative to any of the previous embodiments, the fluid output from the thermal storage device is expanded via a storage expansion device.

[0016] In addition to one or more of the features described above, or as an alternative to any of the previous embodiments, fluid is supplied from the storage expansion device to the evaporator.

[0017] In addition to one or more of the features described above, or as an alternative. the regulating valve directs only a portion of the fluid from the compressor to the thermal storage device containing the phase change material.

[0018] In addition to one or more of the features described above, or as an alternative. to any of the previous embodiments, another portion of the fluid is provided from the compressor to the condenser. The flow of the other portion of the fluid provided to the condenser is arranged in parallel with the flow of the fluid provided to the thermal storage device.

[0019] In addition to one or more of the features described above, or as an alternative. to any of the previous embodiments, the portion of the fluid at a location downstream of the thermal storage device is mixed with the other portion of the fluid at a location downstream of the condenser at a location upstream of the evaporator.

[0020] In addition to one or more of the features described above, or as an alternative. to any of the previous embodiments, the portion of the fluid output from the thermal storage device is provided to a storage expansion device, and the portion of the fluid downstream of the storage expansion device is mixed with the other portion of the fluid downstream of the expansion device.

[0021] In addition to one or more of the features described above, or as an alternative. to any of the previous embodiments, the phase change material is regenerated during a non-peak energy period.

[0022] In addition to one or more of the features described above, or as an alternative. to any of the previous embodiments, the phase change material is regenerated when a condensing temperature of the cooling fluid is lower than a condensing temperature of the phase change material. BRIEF DESCRIPTION OF DRAWINGS

[0023] The following description should not be considered limiting in any way. Referring to the drawings, like elements are numbered alike:

[0024] Figure 1 is a schematic diagram of a basic vapor compression system;

[0025] Figure 2 is a schematic diagram of a vapor compression system including a thermal storage device according to an embodiment;

[0026] Figure 3 is a schematic diagram of a vapor compression system including a thermal storage device according to another embodiment;

[0027] Figure 4 is a cross-sectional view of a thermal storage device according to an embodiment; and

[0028] Figure 5 is a cross-sectional view of a thermal storage device according to another embodiment.DETAILED DESCRIPTION DETAILED DESCRIPTION

[0029] Reference is made to the drawings, wherein the detailed description of one or more embodiments of the disclosed devices and methods is set forth by way of example and not by way of limitation.

[0030] Reference is now made to the drawings, in which Figure 1 An example of an existing vapor compression system 20 is provided, having a closed fluid circuit within which a refrigerant R or other fluid circulates. As shown, the vapor compression system 20 includes one or more compressors 22, a first heat exchanger 24, an expansion device 26, and a second heat exchanger 28. A fluid, such as for example a refrigerant, is configured to circulate through the vapor compression system 20 in a clockwise direction, for example.

[0031] In operation, the compressor 22 receives refrigerant vapor from the second heat exchanger 28 and compresses it to a high temperature and pressure. The relatively hot refrigerant vapor is then delivered to the first heat exchanger 24, where it is cooled and condensed to a liquid state via a heat exchange relationship with a cooling medium C, such as for example air or water. Thus, the first heat exchanger 24 is a heat rejection heat exchanger or condenser. The cooled liquid refrigerant flows from the first heat exchanger 24 to the expansion device 26, such as for example an expansion valve, where the refrigerant expands to a lower pressure, with a decrease in temperature, and can exist in a liquid / vapor two-phase state. The refrigerant R is provided from the expansion device 26 to the second heat exchanger 28. The second heat exchanger 28 functions as a heat absorption heat exchanger or evaporator, as any refrigerant R in the liquid phase evaporates due to heat transfer from a secondary medium E, such as for example air, to the refrigerant R within the second heat exchanger 28. The low pressure vapor refrigerant R returns from the second heat exchanger 28 to the compressor 22 to repeat the cycle.

[0032] Reference is now made to the drawings, in which Figure 2 and Figure 3 In embodiments, the vapor compression system 20 additionally includes a thermal storage device 30. The thermal storage device 30 can be filled with a phase change material P that is capable of transitioning between a first phase and a second phase. The phase change material P can be capable of transitioning between a solid and a liquid, or alternatively between a liquid and a gas. In embodiments, the phase change material P is a low temperature molten salt. However, other suitable phase change materials P, such as for example paraffin or ice, are also within the scope of the present disclosure.

[0033] The thermal storage device 30 can be used to selectively cool the refrigerant R within the vapor compression cycle. In embodiments, the thermal storage device 30 is operable to cool the refrigerant within the vapor compression system 20 in place of the condenser 24. However, in other embodiments, the thermal storage device 30 is operable in combination with the condenser 24 to cool the refrigerant within the vapor compression system 20. The thermal storage device 30 can be disposed in fluid communication with the compressor 22. In Figure 2 In the illustrated non-limiting embodiment shown in FIG. 1, the compressor 22 is a two-stage compressor. Thus, the first stage of the compressor 22 has a first inlet 32 at a first suction pressure and a first outlet 34 at a first discharge pressure, and the second stage of the compressor 22 similarly includes a second inlet 36 at a second suction pressure and a second outlet 38 at a second discharge pressure. The first discharge pressure is greater than the first suction pressure and less than the second discharge pressure. The condenser 24 is fluidly connected to the second outlet 38 of the compressor 22. In the illustrated non-limiting embodiment, the thermal storage device 30 is fluidly connected to the first outlet 34 of the compressor 22.

[0034] The valve VI can be disposed within at least one conduit 40 fluidly coupling an inlet 42 of the thermal storage device 30 to the compressor 22, such as, for example, the first outlet 34. The valve VI can be adjustable between a plurality of positions to control the flow from the compressor 22 to the thermal storage device 30. The valve VI can be adjustable between a first or closed position, in which no flow is provided from the compressor 22 to the thermal storage device 30, and a second or fully open position, in which all flow provided to the compressor 22 is output to the thermal storage device 30. However, it should be appreciated that in other embodiments, only a portion of the flow of refrigerant R within the compressor 22 can be provided to the thermal storage device 30, even when the valve VI is in the fully open position. In such embodiments, the refrigerant R can be provided from the compressor 22 in parallel to the condenser 24 and the thermal storage device 30.

[0035] Within the vapor compression system 20, refrigerant R output from the second outlet 38 of the compressor 22 is provided in series to the condenser 24, the expansion valve 26, and the evaporator 28, as previously described. When the valve VI is at least partially open, refrigerant R at an intermediate pressure is provided from the first outlet 34 to the inlet 42 of the thermal storage device 30. The refrigerant R can be configured to flow over or across the thermal storage device 30, or alternatively or additionally, can flow through one or more channels extending through the phase change material P within the thermal storage device 30, as will be described in greater detail below. In embodiments in which the phase change material P is a cold, low temperature molten salt, heat from the refrigerant R output from the compressor 22 is transferred to the phase change material P. Over time, this heat can cause the phase change material P to change phase, such as, for example, from a solid to a liquid, or from a liquid to a gas. In the illustrated, non-limiting embodiment, the low temperature molten salt can transition to a molten salt. As a result of this endothermic process, the refrigerant R provided at the outlet 44 of the thermal storage device 30 is cooler than the refrigerant R provided at the inlet 42 of the thermal storage device 30. The at least partially cooled refrigerant R is then provided to a downstream storage expansion device, identified at 50, in which the refrigerant expands to a lower pressure, similar to the expansion valve 26. The refrigerant R is provided from the storage expansion device 50 to the second heat exchanger 28, in which the refrigerant R is evaporated before being returned to the first inlet 32 of the compressor 22. In embodiments in which the refrigerant R is provided in parallel to the condenser 24 and the thermal storage device 30, the stream output from the expansion device 26 is mixed with the stream output from the storage expansion device 50 at a location upstream of the inlet of the evaporator 28.

[0036] In Figure 3 In the illustrated, non-limiting embodiment, the thermal storage device 30 is disposed directly downstream of the outlet of the compressor 22. In such embodiments, the compressor 22 can be a single stage or a multi-stage compressor; however, in embodiments in which the compressor 22 includes multiple stages, the thermal storage device 30 is located downstream of the outlet 38 of the last stage of the compressor 22 and is fluidly connected to the outlet 38 via a conduit 52. Similar to the previous embodiments, the storage expansion device 50 can be disposed downstream of the thermal storage device 30 and upstream of the evaporator 28 with respect to the flow of refrigerant R.

[0037] The condenser 24 can also be fluidly coupled to the outlet 38 of the compressor 22. In the illustrated, non-limiting embodiment, the inlet of the condenser 24 is fluidly connected to the conduit 52 via another conduit 54. The conduit 54 can be connected to the conduit 52 at any suitable location downstream of the outlet 38 and upstream of the inlet 42 of the thermal storage device 30. However, embodiments in which the conduit 54 is directly connected to the outlet 38 or alternatively the inlet 42 of the thermal storage device 30 are also contemplated herein.

[0038] The vapor compression system 20 includes a valve VI that is operable to control the flow of refrigerant provided to at least one of the thermal storage device 30 and the condenser 24. In embodiments, the valve VI is disposed at the intersection between the conduits 52, 54. However, embodiments in which the valve VI is disposed at other suitable locations are within the scope of the present disclosure. The valve VI can be able to adjust between a first or closed position in which no flow is provided from the compressor 22 to the thermal storage device 30 and a second or fully open position in which all flow provided to the compressor 22 is output to the thermal storage device 30. However, in other embodiments, even when the valve VI is in the fully open position, a portion of the flow of refrigerant R output from the compressor 22 can be provided to the thermal storage device 30 and another portion of the refrigerant R can be provided to the condenser 24 in parallel. In embodiments in which refrigerant R is provided to both the thermal storage device 30 and the condenser 24 simultaneously, the refrigerant R output from the storage expansion device 50 can be mixed with the refrigerant R output from the expansion device 26 at a location upstream of the evaporator 28.

[0039] Figure 2 and Figure 3 The valve VI in each of the embodiments disclosed in

[0040] In Figure 2 and Figure 3 In each of the embodiments disclosed in

[0041] Further, to regenerate the thermal storage device 30, such as by transitioning the phase change material P from the second phase back to the first phase, it can be provided with a cold regeneration fluid RF, such as a flow of, for example, ambient air or water. In such embodiments, the cold regeneration fluid is configured to absorb heat from the phase change material P until substantially all of the phase change material P returns to the first phase. The regeneration fluid RF can be the same fluid as the cooling fluid, or alternatively, can be different. In embodiments, regeneration of the thermal storage device 30 can be performed when ambient temperatures are reduced, such as, for example, during early morning hours or at night, or at off-peak times when energy costs are reduced (also referred to herein as off-peak energy periods). For example, regeneration can be performed when the condensing temperature of the regeneration fluid (or cooling fluid) is lower than the condensing temperature of the phase change material P. It should be understood that the various vapor compression systems 20 shown and described herein are intended only as examples, and vapor compression systems having other configurations are contemplated herein, such as, for example, including an economizer heat exchanger disposed between the condenser 24 and the thermal storage device 30 and the evaporator 28.

[0042] Figure 4 and Figure 5 Various examples of the thermal storage device 30 are shown in greater detail in Figure 4 In non-limiting embodiments of the thermal storage device 30, the thermal storage device 30 includes an outer housing or shell 60 that defines an interior cavity 62. A substantially hollow inner shell or body 64 is disposed within the interior cavity 62 and can be oriented coaxially with a longitudinal axis of the outer housing 60. While the inner body 64 and the outer housing 60 are shown as being substantially similar in shape, embodiments are also contemplated herein in which the inner body 64 and the outer housing 60 have different shapes. As shown, one or more ribs 66 can extend between an outer surface of the inner body 64 and an inner surface of the outer housing 60 to affix the inner body 64 to the outer housing 60. Further, in some embodiments, the one or more ribs 66 can divide a portion of the cavity 62 disposed between the inner body 64 and the outer housing 60 into multiple compartments.

[0043] In embodiments, a phase change material P, such as, for example, a salt material, is disposed within the cavity 62, such as within one or more of the multiple compartments. In such embodiments, the refrigerant R can be configured to flow around an outer surface of the outer housing 60, and the regeneration fluid RF can be configured to flow through an interior 68 of the inner body 64, as shown in Figure 4 However, in other embodiments, such as Figure 5As shown, the refrigerant can be configured to flow through the interior 68 of the inner body 64, and the regeneration fluid RF can be configured to flow around the outer surface of the outer housing 60. In such embodiments, one or more fins 70 can be positioned around and protrude from the exterior of the outer housing 60 to increase heat transfer between the thermal storage device and the regeneration fluid RF. However, it should be appreciated that in other embodiments, the interior of the inner body 64 can be filled with the phase change material P, and the refrigerant R can be configured to flow through one or more of the compartments, and the regeneration fluid RF can be configured to flow through one or more of the compartments.

[0044] By determining whether to use the condenser 24 or the thermal storage device 30 to cool the refrigerant R output from the compressor 22 based on the corresponding condensing temperature associated with each, the total energy required to operate the vapor compression cycle can be reduced, particularly during peak energy moments.

[0045] The term "about" is intended to encompass a degree of error with respect to a stated number that is expected to occur due to the equipment with which the application is made, the particular number used, and the like.

[0046] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising", when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0047] While the present disclosure has been described with reference to one or more exemplary embodiments, those skilled in the art will understand that various changes in form and detail can be made therein without departing from the spirit and scope of the disclosure. Additionally, many modifications can be made to adapt a particular situation or material to the teachings of the disclosure without departing from the central scope thereof. Therefore, it is intended that the disclosure not be limited to the particular embodiment disclosed as the best currently contemplated mode of carrying out this disclosure but that the disclosure will include all embodiments falling within the scope of the claims.

Claims

1. A vapor compression system comprising: a compressor, a condenser, an expansion device, and an evaporator fluidly connected to form a closed fluid loop having a fluid circulating therethrough; a thermal storage device comprising a phase change material, the thermal storage device fluidly connected to an outlet of the compressor and disposed downstream of the outlet of the compressor relative to a flow of the fluid; a storage expansion device disposed downstream of the thermal storage device and upstream of the evaporator; and a valve adjustable between a plurality of positions to control the flow of the fluid from the compressor to the thermal storage device. The thermal storage device and the condenser are disposed in parallel downstream of the compressor.

2. The vapor compression system of claim 1, wherein, The condenser and the thermal storage device are each fluidly connected to the outlet of the compressor.

3. The vapor compression system of claim 2, wherein, The compressor comprises a first stage having a first outlet and a second stage having a second outlet, the thermal storage device is fluidly connected to and disposed downstream of the first outlet, and the condenser is fluidly connected to and disposed downstream of the second outlet.

4. The vapor compression system of claim 2, wherein, The condenser is operable to receive the fluid at a first pressure, and the thermal storage device is operable to receive the fluid at a second pressure, the first pressure being greater than the second pressure.

5. The vapour compression system of any of claims 1 to 4, wherein, An outlet of the expansion device is fluidly connected to an outlet of the storage expansion device at a location upstream of an inlet of the evaporator.

6. The vapour compression system of any of claims 1 to 5, wherein, The phase change material is a molten salt.

7. The vapour compression system of any of claims 1 to 6, wherein, The valve is positioned downstream of the compressor and upstream of an inlet of the thermal storage device.

8. The vapour compression system of any of claims 1 to 7, wherein, The valve is adjustable between the plurality of positions to minimize a condensation temperature of the fluid.

9. The vapour compression system of any of claims 1 to 8, wherein, The valve is disposed at a location to direct the flow of the fluid from the compressor to the thermal storage device when a phase change temperature of the phase change material is below an ambient temperature.

10. The vapor compression system of claim 9, wherein, At one of the plurality of positions, the fluid is provided to both the condenser and the thermal storage device simultaneously.

11. The vapour compression system of any of claims 1 to 10, wherein, 12. A method of operating a vapor compression system comprising: providing a compressor, a condenser, an expansion device, and an evaporator fluidly connected to form a closed fluid loop having a fluid circulating therethrough; comparing a condensation temperature of a cooling fluid to a condensation temperature of a phase change material to determine a lowest condensation temperature; in response to determining that the condensation temperature of the phase change material is the lowest condensation temperature, adjusting a valve to direct the fluid from the compressor to a thermal storage device containing the phase change material; and removing heat from the fluid via the phase change material.

13. The method of claim 12, further comprising expanding the fluid output from the thermal storage device via a storage expansion device.

14. The method of claim 13, further comprising providing the fluid from the storage expansion device to the evaporator. Adjusting the valve to direct only a portion of the fluid from the compressor to the thermal storage device containing the phase change material. ​ 15. The method of any one of claims 12 to 14, wherein, ​ 16. The method of claim 15, further comprising providing another portion of the fluid from the compressor to the condenser, the flow of the fluid provided to the condenser being arranged in parallel with the flow of the fluid provided to the thermal storage device.

17. The method of claim 16, further comprising mixing the portion of fluid at a location downstream of the thermal storage device with the another portion of the fluid at a location downstream of the condenser at a location upstream of the evaporator.

18. The method of claim 17, wherein, the portion of the fluid output from the thermal storage device is provided to a storage expansion device, the portion of the fluid downstream of the storage expansion device being mixed with the another portion of the fluid downstream of the expansion device.

19. The method of any of claims 12-18, further comprising regenerating the phase change material during off-peak energy periods.

20. The method of any of claims 12-19, further comprising regenerating the phase change material when the condensing temperature of the cooling fluid is lower than the condensing temperature of the phase change material.

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