EP4653782A1

EP4653782A1 - Hvac system with thermal storage

Info

Publication number: EP4653782A1
Application number: EP25177788.4A
Authority: EP
Inventors: Vishnu Sishtla; Chaitanya HALBE; Jin Zhu
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 2024-05-21
Filing date: 2025-05-20
Publication date: 2025-11-26
Also published as: US20250362039A1; CN120991497A

Abstract

A vapor compression system (20) includes a compressor (22), a condenser (24), an expansion device (26), and an evaporator (28) fluidly connected to form a closed fluid loop having a fluid circulating therethrough. A thermal storage device (30) including a phase change material (P) is fluidly connected to and is arranged downstream from an outlet of the compressor (22) relative to a flow of the fluid. A storage expansion device (50) is arranged downstream from the thermal storage device (30) and upstream from the evaporator (28) and a valve (V1) is adjustable between a plurality of positions to control the flow of the fluid from the compressor (22) to the thermal storage device (30).

Description

BACKGROUND

Exemplary embodiments of the present invention relate to the art of condensers, and more particularly, to a vapor compression system having various means for removing heat from a refrigerant therein.
Conventional vapor compression systems have a condenser that is sized based on a maximum load at a maximum ambient temperature. However, the maximum load and the maximum ambient temperature are not always present. Sizing the heat exchanger system for the maximum heat load at continuous duty cycle in the maximum expected ambient air condition results in an oversized, overweight, and overpowered condensing unit for those portions of the duty cycle that are not near the limits of the system. Further, because of the increased cost of electricity during peak hours, such as when the ambient temperature is greatest, it is desirable to shift operational reliance of a vapor compression cycle on electricity to off-peak times, such as during morning and nighttime hours.

BRIEF DESCRIPTION

According to a first aspect of the present invention, 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 and is arranged downstream from an outlet of the compressor relative to a flow of the fluid. A storage expansion device is arranged downstream from the thermal storage device and upstream from the evaporator and a valve is adjustable between a plurality of positions to control the flow of the fluid from the compressor to the thermal storage device.
Optionally, the thermal storage device and the condenser are arranged in parallel downstream from the compressor.
Optionally, the condenser and the thermal storage device are both fluidly connected to the outlet of the compressor.
Optionally, 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 is arranged downstream from the first outlet and the condenser is fluidly connected to and is arranged downstream from the second outlet.
Optionally, 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.
Optionally, an outlet of the expansion device is fluidly connected to an outlet of the storage expansion device at a location upstream from an inlet of the evaporator.
Optionally, the phase change material is a melting salt.
Optionally, the valve is positioned downstream from the compressor and upstream from an inlet of the thermal storage device.
Optionally, the valve is adjustable between the plurality of positions to minimize a condensing temperature of the fluid.
Optionally, the valve is arranged at a position 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 less than an ambient temperature.
Optionally, at one of the plurality of positions, the fluid is provided to the condenser and the thermal storage device simultaneously.
According to a second aspect of the present invention, a method of operating a vapor compression system includes providing a compressor, a condenser, an expansion device, and an evaporator fluidly connected to form a closed fluid loop, the closed fluid loop having a fluid circulating therethrough, comparing a condensing temperature of a cooling fluid with a condensing temperature of a phase change material to determine a lowest condensing temperature, in response to determining that the condensing temperature of the phase change material is the lowest condensing 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.
Optionally, expanding the fluid output from the thermal storage device via a storage expansion device.
Optionally, providing the fluid from the storage expansion device to the evaporator.
Optionally, adjusting the valve directs only a portion of the fluid from the compressor to the thermal storage device containing the phase change material.
Optionally, providing another portion of the fluid from the compressor to the condenser. The flow of the another portion of the fluid provided to the condenser is arranged in parallel with the flow of the fluid provided to the thermal storage device.
Optionally, mixing the portion of fluid at a location downstream from the thermal storage device with the another portion of the fluid at a location downstream from the condenser at a location upstream from the evaporator.
Optionally, 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 from the storage expansion device is mixed with the another portion of the fluid downstream from the expansion device.
Optionally, regenerating the phase change material during off-peak energy hours.
Optionally, regenerating the phase change material when the condensing temperature of the cooling fluid is less than the condensing temperature of the phase change material.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions are provided by way of example only, so as to better understand the invention, but should not be considered limiting in any way on the scope of the invention, which is defined by the claims. With reference to the accompanying drawings, like elements are numbered alike:

FIG. 1 is a schematic diagram of a basic vapor compression system;
FIG. 2 is a schematic diagram of a vapor compression system including a thermal storage device;
FIG. 3 is a schematic diagram of a vapor compression system including another thermal storage device;
FIG. 4 is a cross-sectional view of the thermal storage device; and
FIG. 5 is a cross-sectional view of the thermal storage device.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures.
With reference now to FIG. 1, an example of an existing vapor compression system 20 having a closed fluid loop within which a refrigerant R or other fluid circulates is provided. 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 a refrigerant for example, is configured to circulate through the vapor compression system 20 such as in a clockwise direction for example.
In operation, the compressor 22 receives a 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 air or water for example. Accordingly, the first heat exchanger 24 is a heat rejection heat exchanger or a condenser. The cooled liquid refrigerant flows from the first heat exchanger 24 to the expansion device 26, such as an expansion valve for example, in which the refrigerant is expanded to a lower pressure where the temperature is reduced and the refrigerant may exist in a two-phase liquid/vapor state. From the expansion device 26, the refrigerant R is provided to the second heat exchanger 28. Because heat is transferred from a secondary medium E, such as air for example, to the refrigerant R within the second heat exchanger 28, causing any refrigerant R in the liquid phase to vaporize, the second heat exchanger 28 functions as a heat absorption heat exchanger or an evaporator. From the second heat exchanger 28, the low-pressure vapor refrigerant R returns to the compressor 22 so that the cycle may be repeated.
With reference now to FIGS. 2 and 3, in an embodiment, the vapor compression system 20 additionally includes a thermal storage device 30. The thermal storage device 30 may be filled with a phase change material P transformable between a first phase and a second phase. The phase change material P may be transformable between a solid and a liquid, or alternatively, between a liquid and a gas. In an embodiment, the phase change material P is a low temperature melting salt. However, other suitable phase change materials P, such as paraffin wax or ice for example, are also within the scope of the invention.
The thermal storage device 30 may be used to selectively cool the refrigerant R within the vapor compression cycle. In an embodiment, 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 may be arranged in fluid communication with the compressor 22. In the illustrated, non-limiting embodiment shown in FIG. 2, the compressor 22 is a two-stage compressor. Accordingly, 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 is 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.
A valve V1 may be arranged within the at least one conduit 40 fluidly coupling an inlet 42 of the thermal storage device 30 to the compressor 22, such as the first outlet 34 for example. The valve V1 may be adjustable between a plurality of positions to control the flow from the compressor 22 to the thermal storage device 30. The valve V1 may 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 of the flow provided to the compressor 22 is output to the thermal storage device 30. However, it should be understood that in other embodiments, even when the valve V1 is in a fully open position, only a portion of the flow of refrigerant R within the compressor 22 may be provided to the thermal storage device 30. In such embodiments, refrigerant R may be provided from the compressor 22 to the condenser 24 and the thermal storage device 30 in parallel.
Within the vapor compression system 20, refrigerant R output from the second outlet 38 of the compressor 22 is provided to the condenser 24, expansion valve 26, and evaporator 28 in series, as previously described. When the valve V1 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 may be configured to pass over or flow across the thermal storage device 30, or alternatively, or in addition, may flow through one or more passages that extend through the phase change material P within the thermal storage device 30, as will be described in more detail below. In embodiments where the phase change material P is a cool, low-temperature melting salt, heat from the refrigerant R output from the compressor 22 is transferred to the phase change material P. Over time, this heat may cause the phase change material P to change phases, such as from a solid to a liquid, or from a liquid to a gas for example. In the illustrated, non-limiting embodiment, the low-temperature melting salt may transform into a molten salt. As a result of this heat absorption, 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, where the refrigerant is expanded to a lower pressure, similar to the expansion valve 26. From the storage expansion device 50, the refrigerant R is provided to the second heat exchanger 28, where the refrigerant R is vaporized prior to returning to the first inlet 32 of the compressor 22. In embodiments where refrigerant R is provided to the condenser 24 and the thermal storage device 3o in parallel, the flow output from the expansion device 26 is mixed with the flow output from the storage expansion device 50 at a location upstream from an inlet of the evaporator 28.
In the non-limiting embodiment of FIG. 3, the thermal storage device 30 is arranged directly downstream from an outlet of the compressor 22. In such embodiments, the compressor 22 may be a single stage or a multistage compressor; however, in embodiments where the compressor 22 includes multiple stages, the thermal storage device 30 is located downstream from and is fluidly connected to the outlet 38 of the last stage of the compressor 22 via a conduit 52. Similar to the previous embodiment, a storage expansion device 50 may be arranged downstream from the thermal storage device 30 and upstream from the evaporator 28 relative to the flow of refrigerant R.
The condenser 24 may also be fluidly coupled to the outlet 38 of the compressor 22. In the illustrated, non-limiting embodiment, an inlet of the condenser 24 is fluidly connected to the conduit 52 via another conduit 54. The conduit 54 may be connected to the conduit 52 at any suitable location downstream from the outlet 38 and upstream from the inlet 42 of the thermal storage device 30. However, embodiments, where the conduit 54 is connected directly to the outlet 38 or alternatively, to the inlet 42 of the thermal storage device 30 are also contemplated herein.
The vapor compression system 20 includes a valve V1 operable to control a flow of refrigerant provided to at least one of the thermal storage device 30 and the condenser 24. In an embodiment, the valve V1 is arranged at the intersection between the conduits 52, 54. However, embodiments where the valve V1 is arranged at another suitable location are also within the scope of the invention. The valve V1 may be adjustable between a first or closed position in which no flow is provided from the compressor 22 to the thermal stage device 30 and a second or fully open position in which all of the flow provided to the compressor 22 is output to the thermal storage device 30. However, in other embodiments, even when the valve V1 is in a fully open position, a portion of the flow of refrigerant R output from the compressor 22 may be provided to the thermal storage device 30 and another portion of the refrigerant R may be provided to the condenser 24 in parallel. In embodiments where 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 may be mixed with the refrigerant R output from the expansion device 26 at a location upstream from the evaporator 28.
The valve V1 in each of FIGS. 2 and 3 may be operable based on one or more parameters, such as an outside or ambient temperature and the cost of electricity for example. In an embodiment, the valve V1 is operable to redirect at least a portion of the refrigerant flow R, and in some embodiments the entire flow of refrigerant R, based on the temperature used to condense the refrigerant. When external air is used to condense the refrigerant R at the condenser 24, the condensing temperature is the temperature of the ambient air. When the phase change material P is used to condense the refrigerant R, the phase change temperature, such as the melting temperature of the salt for example, is the condensing temperature. Relying on the material having the lowest condensing temperature to condense the refrigerant can limit the operation of the compressor 22, thereby resulting in energy savings.
In each of the embodiments disclosed in FIGS. 2 and 3, the thermal storage device 30 has a limited capacity for operation as a condenser. Once the entirety of the phase change material P within the thermal storage device 30 has transformed from the first phase to the second phase, the phase change material P in the second phase is no longer capable of absorbing heat from the refrigerant R. In an embodiment, the thermal storage device 30 is sized to have a capacity such that the thermal storage device 30 is operable as a condenser for several hours, such as two or more hours, three or more hours, four or more hours, five or more hours, six or more hours, seven or more hours, eight or more hours, nine or more hours, or ten or more hours for example. In an embodiment, the thermal storage device has a condenser capacity between two and eight hours, such as between two and six hours or between four and six hours.
Further, to regenerate the thermal storage device 30, such as by transforming the phase change material P from the second phase back to the first phase, a flow of a cool regeneration fluid RF, such as ambient air or water for example, may be provided thereto. In such embodiments, the cool regeneration fluid is configured to absorb heat from the phase change material P until the substantial entirety of the phase change material P has returned to the first phase. The regeneration fluid RF may be the same fluid as the cooling fluid, or alternatively, may be different therefrom. In an embodiment, regeneration of the thermal storage device 30 may be performed when the ambient temperature has lowered, such as during the early morning or at night for example, or at an off-peak time when energy charges are reduced, also referred to herein as off-peak energy hours. For example, regeneration may be performed when the condensing temperature of the regeneration fluid (or the cooling fluid) is less than the condensing temperature of the phase change material P. It should be understood that the various vapor compression systems 20 illustrated and described herein are intended as an example only and that a vapor compression system having another configuration, such as including an economizer heat exchanger arranged between at least one of the condenser 24 and the thermal storage device 30 and the evaporator 28 for example, are contemplated herein.
Various examples of a thermal storage device 30 are illustrated in more detail in FIGS. 4 and 5. In the non-limiting embodiment of FIG. 4, the thermal storage device 30 includes an outer housing or shell 60 defining an internal cavity 62. A substantially hollow internal shell or body 64 is arranged within the internal cavity 62 and may be oriented coaxially with a longitudinal axis of the outer housing 60. Although the inner body 64 and the outer housing 60 are illustrated as being substantially similar in shape, embodiments where the inner body 64 and outer housing 60 have different shapes are also contemplated herein. As shown, one or more ribs 66 may extend between an exterior surface of the inner body 64 and an interior 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 may divide the portion of the cavity 62 arranged between the inner body 64 and the outer housing 60 into a plurality of compartments.
In an embodiment, the phase change material P, such as a salt material for example, is arranged within the cavity 62, such as within one or more of the plurality of compartments. In such embodiments the refrigerant R may be configured to flow about an exterior surface of the outer housing 60 and the regeneration fluid RF may be configured to flow through the interior 68 of the inner body 64, as shown in FIG. 4. However, in other embodiments, such as shown in FIG. 5, the refrigerant may be configured to flow through the interior 68 of the inner body 64 and the regeneration fluid RF may be configured to flow about an exterior surface of the outer housing 60. In such embodiments, one or more fins 70 may be positioned about and protrude from the exterior of the outer housing 60 to increase the heat transfer between the thermal storage device and the regeneration fluid RF. However, it should be understood that in other embodiments, the interior of the inner body 64 may be filled with the phase change material P and the refrigerant R may be configured to flow through one or more of the compartments and the regeneration fluid RF may be configured to flow through one or more compartments.
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 temperatures associated with each, the overall energy required to operate the vapor compression cycle, particularly during peak energy times may be reduced.
The term "about" is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. 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, element components, and/or groups thereof.
While the present invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements of the described embodiment(s) without departing from the scope of the present invention, as defined by the claims. In addition, many modifications may be made to adapt a particular situation or material to the teachings herein without departing from the scope of the invention. Therefore, it is intended that the present invention not be limited to the particular embodiment disclosed, but that the present invention will include all embodiments falling within the scope of the claims.

Claims

A vapor compression system (20), comprising:
a compressor (22), a condenser (24), an expansion device (26), and an evaporator (28) fluidly connected to form a closed fluid loop having a fluid circulating therethrough;

a thermal storage device (30) including a phase change material (P), the thermal storage device being fluidly connected to and arranged downstream from an outlet of the compressor relative to a flow of the fluid;

a storage expansion device (50) arranged downstream from the thermal storage device and upstream from the evaporator; and

a valve (V1), the valve being adjustable between a plurality of positions to control the flow of the fluid from the compressor to the thermal storage device.
The vapor compression system of claim 1, wherein the thermal storage device and the condenser are arranged in parallel downstream from the compressor.
The vapor compression system of claim 2, wherein the condenser and the thermal storage device are both fluidly connected to the outlet (38) of the compressor.
The vapor compression system of claim 2, wherein the compressor includes a first stage having a first outlet (34) and a second stage having a second outlet (38), the thermal storage device being fluidly connected to and arranged downstream from the first outlet and the condenser being fluidly connected to and arranged downstream from the second outlet.
The vapor compression system of any of claims 1-4, 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.
The vapor compression system of any of claims 1-5, wherein an outlet of the expansion device is fluidly connected to an outlet of the storage expansion device at a location upstream from an inlet of the evaporator.
The vapor compression system of any of claims 1-6, wherein the phase change material is a melting salt.
The vapor compression system of any of claims 1-7, wherein the valve is positioned downstream from the compressor and upstream from an inlet of the thermal storage device, and/or
wherein, at one of the plurality of positions, the fluid is provided to the condenser and the thermal storage device simultaneously.
The vapor compression system of any of claims 1-8 wherein the valve is adjustable between the plurality of positions to minimize a condensing temperature of the fluid,
optionally wherein the valve is arranged at a position 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 less than an ambient temperature.
A method of operating a vapor compression system (20), comprising:
providing a compressor (22), a condenser (24), an expansion device (26), and an evaporator (28) fluidly connected to form a closed fluid loop, the closed fluid loop having a fluid circulating therethrough;

comparing a condensing temperature of a cooling fluid with a condensing temperature of a phase change material (P) to determine a lowest condensing temperature;

in response to determining that the condensing temperature of the phase change material is the lowest condensing temperature, adjusting a valve (V1) to direct the fluid from the compressor to a thermal storage device (30) containing the phase change material; and

removing heat from the fluid via the phase change material.
The method of claim 10, further comprising:
expanding the fluid output from the thermal storage device via a storage expansion device (50), and/or

providing the fluid from the storage expansion device to the evaporator.
The method of any of claims 10-11, wherein adjusting the valve directs only a portion of the fluid from the compressor to the thermal storage device containing the phase change material.
The method of claim 12, further comprising providing another portion of the fluid from the compressor to the condenser, a flow of the fluid provided to the condenser being arranged in parallel with the flow of the fluid provided to the thermal storage device.
The method of claim 13, further comprising mixing the portion of fluid at a location downstream from the thermal storage device with the another portion of the fluid at a location downstream from the condenser at a location upstream from the evaporator,
optionally wherein the portion of the fluid output from the thermal storage device is provided to a storage expansion device (50), the portion of the fluid downstream from the storage expansion device being mixed with the another portion of the fluid downstream from the expansion device.
The method of any of claims 10-14, further comprising:
regenerating the phase change material during off-peak energy hours, and/or

regenerating the phase change material when the condensing temperature of the cooling fluid is less than the condensing temperature of the phase change material.