Hvac System with Thermal Storage

This application claims the benefit of U.S. provisional patent application Ser. No. 63/650,123, filed May 21, 2024, the entire contents of which are incorporated herein by reference.

Exemplary embodiments of the present disclosure 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.

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 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.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, the thermal storage device and the condenser are arranged in parallel downstream from the compressor.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, the condenser and the thermal storage device are both fluidly connected to the outlet of the compressor.

In addition to one or more of the features described above, or as an alternative to any of the foregoing 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 is arranged downstream from the first outlet and the condenser is fluidly connected to and is arranged downstream from the second outlet.

In addition to one or more of the features described above, or as an alternative to any of the foregoing 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.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, 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.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, the phase change material is a melting salt.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, the valve is positioned downstream from the compressor and upstream from an inlet of the thermal storage device.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, the valve is adjustable between the plurality of positions to minimize a condensing temperature of the fluid.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, 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.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, at one of the plurality of positions, the fluid is provided to the condenser and the thermal storage device simultaneously.

According to an embodiment, 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.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, expanding the fluid output from the thermal storage device via a storage expansion device.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, providing the fluid from the storage expansion device to the evaporator.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, adjusting the valve directs only a portion of the fluid from the compressor to the thermal storage device containing the phase change material.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, 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.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, 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.

In addition to one or more of the features described above, or as an alternative to any of the foregoing 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 from the storage expansion device is mixed with the another portion of the fluid downstream from the expansion device.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, regenerating the phase change material during off-peak energy hours.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, regenerating the phase change material when the condensing temperature of the cooling fluid is less than the condensing temperature of the phase change material.

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, an example of an existing vapor compression systemhaving a closed fluid loop within which a refrigerant R or other fluid circulates is provided. As shown, the vapor compression systemincludes one or more compressors, a first heat exchanger, an expansion device, and a second heat exchanger. A fluid, such as a refrigerant for example, is configured to circulate through the vapor compression systemsuch as in a clockwise direction for example.

In operation, the compressorreceives a refrigerant vapor from the second heat exchangerand compresses it to a high temperature and pressure. The relatively hot refrigerant vapor is then delivered to the first heat exchangerwhere 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 exchangeris a heat rejection heat exchanger or a condenser. The cooled liquid refrigerant flows from the first heat exchangerto the expansion device, 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, the refrigerant R is provided to the second heat exchanger. Because heat is transferred from a secondary medium E, such as air for example, to the refrigerant R within the second heat exchanger, causing any refrigerant R in the liquid phase to vaporize, the second heat exchangerfunctions as a heat absorption heat exchanger or an evaporator. From the second heat exchanger, the low-pressure vapor refrigerant R returns to the compressorso that the cycle may be repeated.

With reference now to, in an embodiment, the vapor compression systemadditionally includes a thermal storage device. The thermal storage devicemay 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 disclosure.

The thermal storage devicemay be used to selectively cool the refrigerant R within the vapor compression cycle. In an embodiment, the thermal storage deviceis operable to cool the refrigerant within the vapor compression systemin place of the condenser. However, in other embodiments, the thermal storage deviceis operable in combination with the condenserto cool the refrigerant within the vapor compression system. The thermal storage devicemay be arranged in fluid communication with the compressor. In the illustrated, non-limiting embodiment shown in, the compressoris a two-stage compressor. Accordingly, the first stage of the compressorhas a first inletat a first suction pressure and a first outletat a first discharge pressure, and the second stage of the compressorsimilarly includes a second inletat a second suction pressure and a second outletat a second discharge pressure. The first discharge pressure is greater than the first suction pressure and is less than the second discharge pressure. The condenseris fluidly connected to the second outletof the compressor. In the illustrated, non-limiting embodiment, the thermal storage deviceis fluidly connected to the first outletof the compressor.

A valve Vmay be arranged within the at least one conduitfluidly coupling an inletof the thermal storage deviceto the compressor, such as the first outletfor example. The valve Vmay be adjustable between a plurality of positions to control the flow from the compressorto the thermal storage device. The valve Vmay be adjustable between a first or closed position in which no flow is provided from the compressorto the thermal storage deviceand a second or fully open position in which all of the flow provided to the compressoris output to the thermal storage device. However, it should be understood that in other embodiments, even when the valve Vis in a fully open position, only a portion of the flow of refrigerant R within the compressormay be provided to the thermal storage device. In such embodiments, refrigerant R may be provided from the compressorto the condenserand the thermal storage devicein parallel.

Within the vapor compression system, refrigerant R output from the second outletof the compressoris provided to the condenser, expansion valve, and evaporatorin series, as previously described. When the valve Vis at least partially open, refrigerant R at an intermediate pressure is provided from the first outletto the inletof the thermal storage device. The refrigerant R may be configured to pass over or flow across the thermal storage device, 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, 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 compressoris 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 outletof the thermal storage deviceis cooler than the refrigerant R provided at the inletof the thermal storage device. The at least partially cooled refrigerant R is then provided to a downstream storage expansion device, identified at, where the refrigerant is expanded to a lower pressure, similar to the expansion valve. From the storage expansion device, the refrigerant R is provided to the second heat exchanger, where the refrigerant R is vaporized prior to returning to the first inletof the compressor. In embodiments where refrigerant R is provided to the condenserand the thermal storage devicein parallel, the flow output from the expansion deviceis mixed with the flow output from the storage expansion deviceat a location upstream from an inlet of the evaporator.

In the non-limiting embodiment of, the thermal storage deviceis arranged directly downstream from an outlet of the compressor. In such embodiments, the compressormay be a single stage or a multistage compressor; however, in embodiments where the compressorincludes multiple stages, the thermal storage deviceis located downstream from and is fluidly connected to the outletof the last stage of the compressorvia a conduit. Similar to the previous embodiment, a storage expansion devicemay be arranged downstream from the thermal storage deviceand upstream from the evaporatorrelative to the flow of refrigerant R.

The condensermay also be fluidly coupled to the outletof the compressor. In the illustrated, non-limiting embodiment, an inlet of the condenseris fluidly connected to the conduitvia another conduit. The conduitmay be connected to the conduitat any suitable location downstream from the outletand upstream from the inletof the thermal storage device. However, embodiments, where the conduitis connected directly to the outletor alternatively, to the inletof the thermal storage deviceare also contemplated herein.

The vapor compression systemincludes a valve Voperable to control a flow of refrigerant provided to at least one of the thermal storage deviceand the condenser. In an embodiment, the valve Vis arranged at the intersection between the conduits,. However, embodiments where the valve Vis arranged at another suitable location are also within the scope of the disclosure. The valve Vmay be adjustable between a first or closed position in which no flow is provided from the compressorto the thermal stage deviceand a second or fully open position in which all of the flow provided to the compressoris output to the thermal storage device. However, in other embodiments, even when the valve Vis in a fully open position, a portion of the flow of refrigerant R output from the compressormay be provided to the thermal storage deviceand another portion of the refrigerant R may be provided to the condenserin parallel. In embodiments where refrigerant R is provided to both the thermal storage deviceand the condensersimultaneously, the refrigerant R output from the storage expansion devicemay be mixed with the refrigerant R output from the expansion deviceat a location upstream from the evaporator.

The valve Vin each ofmay 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 Vis 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, 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, thereby resulting in energy savings.

In each of the embodiments disclosed in, the thermal storage devicehas a limited capacity for operation as a condenser. Once the entirety of the phase change material P within the thermal storage devicehas 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 deviceis sized to have a capacity such that the thermal storage deviceis 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, 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 devicemay 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 systemsillustrated 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 condenserand the thermal storage deviceand the evaporatorfor example, are contemplated herein.

Various examples of a thermal storage deviceare illustrated in more detail in. In the non-limiting embodiment of, the thermal storage deviceincludes an outer housing or shelldefining an internal cavity. A substantially hollow internal shell or bodyis arranged within the internal cavityand may be oriented coaxially with a longitudinal axis of the outer housing. Although the inner bodyand the outer housingare illustrated as being substantially similar in shape, embodiments where the inner bodyand outer housinghave different shapes are also contemplated herein. As shown, one or more ribsmay extend between an exterior surface of the inner bodyand an interior surface of the outer housingto affix the inner bodyto the outer housing. Further, in some embodiments, the one or more ribsmay divide the portion of the cavityarranged between the inner bodyand the outer housinginto a plurality of compartments.

In an embodiment, the phase change material P, such as a salt material for example, is arranged within the cavity, 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 housingand the regeneration fluid RF may be configured to flow through the interiorof the inner body, as shown in. However, in other embodiments, such as shown in, the refrigerant may be configured to flow through the interiorof the inner bodyand the regeneration fluid RF may be configured to flow about an exterior surface of the outer housing. In such embodiments, one or more finsmay be positioned about and protrude from the exterior of the outer housingto 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 bodymay 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 condenseror the thermal storage deviceto cool the refrigerant R output from the compressorbased 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 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, element components, and/or groups thereof.

While the present disclosure 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 thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims.