In the drawings,
While this invention is susceptible to embodiment in many different forms, there is shown in the drawings and will be described herein in detail specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not to be limited to the specific embodiments described.
The thermal energy storage unit 106 comprises an insulated tank 140 that houses the primary heat exchanger 160 surrounded by a thermal reservoir such as a phase change material (typically fluid/ice depending on the current system mode). The primary heat exchanger 160 further comprises a lower header assembly 156 connected to an upper header assembly 154 with a series of freezing and discharge coils 142 to make a fluid/vapor loop within the insulated tank 140. The upper and lower header assemblies 154 and 156 communicate externally of the thermal energy storage unit 106 with inlet and outlet connections.
The embodiment illustrated in
In charging mode, compressed high-pressure refrigerant leaves the air conditioner unit 102 through high-pressure liquid supply line 112 and is fed through an expansion device 130 to cool the thermal energy storage unit 106 where it enters the primary heat exchanger 160 through the lower header assembly 156 and is then distributed through the freezing coils 142 which act as an evaporator. Cooling is transmitted from the freezing coils 142 to the surrounding liquid phase change material 152 that is confined within the insulated tank 140 and freezes at least a portion of the phase change material 153 (ice) surrounding the freezing coils 142 and storing thermal energy in the process. Warm liquid and vapor phase refrigerant leaves the freezing coils 142 through the upper header assembly 154 and exits the thermal energy storage unit 106 returning to the air conditioner unit 102 through the low pressure return line 118 and is fed to the compressor 110 and re-condensed into liquid.
In cooling mode, cool liquid phase change material leaves the lower portion of the insulated tank 140 and is propelled by a pump 120 to a load heat exchanger 122 where cooling is transferred to a load with the aid of an air handler 150. This load heat exchanger 122 may be a single or multiple evaporators such as might be used to provide multi-zone cooling, mini-split evaporators or the like. Warm liquid leaves load heat exchanger 122 where the liquid is returned to header 154 of the thermal energy storage unit 106 and draws cooling from the solid phase change material 153 surrounding the coils.
Because the system isolates the primary refrigerant from a secondary phase change material loop, the system additionally allows the use of a variety of refrigerants to be used within the device. For example, one type of highly efficient refrigerant that may have properties that would discourage use within a dwelling (such as propane) may be utilized within the primary refrigerant loop, while a more suitable material (such as water, ammonia, slurry ice, brine, ethylene glycol, propylene glycol, various alcohols (Isobutyl, ethanol), sugar, other eutectic materials or the like) can be used for the secondary loop that may enter the dwelling. This allows greater versatility and efficiency of the system while maintaining safety, environmental and application issues to be addressed.
The embodiment illustrated in
The disclosed embodiment also functions in two principal modes of operation, charging (ice-make) and cooling (ice-melt) mode. Cooling mode is identical to that of
Cooling is transferred through the isolating heat exchanger 162 to a thermal energy storage unit 106 within a secondary refrigeration loop 103. This thermal energy storage unit 106 is comparable to that depicted in
Valves may be placed in various places within the secondary refrigerant loop 103 and external melt cooling loop 105 to allow multi-mode conditions with minimal complexity and plumbing. A pump 120 is placed in the external melt cooling loop 105 to pump cold liquid phase change material from the insulated tank 140 to the load heat exchanger 122 and back to the thermal energy storage unit 106 in cooling mode. This load heat exchanger 122 may be a single or multiple evaporators such as might be used to provide multi-zone cooling, mini-split evaporators or the like.
The present embodiment may function in two principal modes of operation, ice-make and ice-melt. In ice-make or charge mode, the primary refrigerant loop 102 is used to cool the primary side of the isolating heat exchanger 162 that transfers heat to the secondary refrigerant loop 103. The secondary refrigerant loop 103 can be either pump driven by adding a refrigerant pump within the loop, typically between the isolating heat exchanger 162 and the lower header assembly 156 (not shown), or gravity feed (as shown and described). The gravity feed system of
This self equalization that occurs during the ice build mode can be beneficial. Large stresses can be applied to the ice storage heat exchanger during uneven ice builds which can ultimately result in mechanical failure or rupture of the heat exchanger. Pump feed systems cannot self equalize because refrigerant is forced into each coil regardless of the amount of ice already surrounding the coil. Another advantage to a gravity feed system is the absence of a pump which requires a power source and also adds additional potential failure modes to the system.
In either gravity or pump fed systems, the secondary refrigerant loop 103 carries cooled condensed refrigerant to the thermal energy storage unit 106 where it enters the primary heat exchanger 160 through the lower header assembly 156 and is then distributed through the freezing coils 142 which act as an evaporator. Cooling is transmitted from the freezing coils 142 to the surrounding liquid phase change material 152 that is confined within the insulated tank 140 and freezes at least a portion of the phase change material 153 (ice) surrounding the freezing coils 142 and storing thermal energy in the process. Within the insulated tank 140, a portion of the phase change material remains liquid and typically will surround the solid material (although a slurry may also be used). This cold liquid phase change material 152 is drawn from the lower portion of the insulated tank 140 within the thermal energy storage unit 106 with a pump 120 and circulated through the load heat exchanger 122 and used to cool a heat load utilizing an air handler 150. Warm liquid phase change material 152 leaves the load heat exchanger 122 and is returned to the insulated tank 140 where it is cooled by melting the solid phase change material 153 (ice) surrounding the freezing coils 142.
In charging mode, the thermal energy storage unit 106 acts as an evaporator and cooling is transmitted to fluid that is confined within the thermal energy storage unit 106 thus storing thermal energy. Warm liquid and vapor phase refrigerant leaves the freezing coils 142 through the upper header assembly 154 and exits the thermal energy storage unit 106 returning to the isolating heat exchanger 162 and re-condensed into liquid.
In ice-melt or cooling mode, the primary refrigerant loop 102 can continue to cool, can be shut down, or can be disengaged. Cool liquid refrigerant is drawn from the thermal energy storage unit 106 and is pumped by a pump 120 to the load heat exchanger 122 where cooling is transferred to a load with the aid of an air handler 150. The warm mixture of liquid and vapor phase refrigerant leaves the load heat exchanger 122 where the mixture is returned to the thermal energy storage unit 106 now acting as a condenser. Vapor phase refrigerant is cooled and condensed by drawing cooling from the cold fluid or ice. As with the embodiment of
The disclosed embodiment also functions in the two modes of operation, charging and cooling with the addition of a direct cooling mode. Cooling mode is identical to that of
In direct cooling mode the thermal energy storage unit 106 is bypassed and a by-pass refrigeration loop 107 delivers condensed refrigerant leaving the air conditioner unit 102 directly to a primary side of a bypass heat exchanger 198 and is then returned to the air conditioner unit 102. The secondary side of the bypass heat exchanger 198 is in communication with the load heat exchanger 122 with the external melt cooling loop 105. Valves 194 and 196 can be used isolate this loop from the thermal energy storage unit 106, while additional valves 188 and 189 can be used to remove the isolating heat exchanger 162 from the primary refrigerant loop 101 and facilitate the by-pass refrigeration loop 107. As with previous embodiments, a pump 120 is placed in the external melt cooling loop 105 to pump cold liquid phase change material that from secondary side of the bypass heat exchanger 198 to the load heat exchanger 122 and back. An air handler 150 is utilized in conjunction with the load heat exchanger 122 to provide cooling to a heat load. This load heat exchanger 122 may be a single or multiple evaporators such as might be used to provide multi-zone cooling, mini-split evaporators or the like.
Whereas
In cooling mode, cool liquid phase change material leaves the lower portion of the insulated tank 140 and is propelled by a pump 120 to a primary side of an intermediate heat exchanger 123 where cooling is transferred from the external melt cooling loop 205 to a secondary refrigerant loop 203. Warm liquid leaves the intermediate heat exchanger 123 and is returned to the upper portion of the thermal energy storage unit 106 and the warm liquid draws cooling from the solid phase change material 153 surrounding the coils. The secondary refrigerant loop 203 flows through the secondary side of the intermediate heat exchanger 123 drawing cooling from the fluid on the primary side and warming the liquid phase change material. This cools and condenses the refrigerant which is either propelled by a refrigerant pump 121 (as shown) or driven by a gravity fed thermosiphon (not shown) to a load heat exchanger 122 where the refrigerant is expanded and cooling is delivered to a heat load with the aid of an air handler 150. The warm mixed or vapor phase refrigerant is then returned to the intermediate heat exchanger 123 to complete the secondary refrigerant loop 203.
As with the embodiment of
By utilizing such an embodiment current dwellings that use standard air conditioning systems may be readily adapted or retrofit to a thermal storage system by the addition of a thermal energy storage unit 106, expansion device 130, Intermediate heat exchanger 123, pump 120 and refrigerant pump 121. Because the system isolates the primary refrigerant from a secondary phase change material loop and a secondary refrigerant, the system additionally allows the use of a variety of refrigerants to be used within the device. The disclosed embodiments therefore provide a refrigerant-based thermal storage system method and device wherein an isolated external melt cooling loop is utilized to transfer cooling to a heat load utilizing a phase change material.
It is also possible to utilize the secondary refrigerant loop 203 of the embodiment of
The foregoing description of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and other modifications and variations may be possible in light of the above teachings. The embodiment was chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and various modifications as are suited to the particular use contemplated. It is intended that the appended claims be construed to include other alternative embodiments of the invention except insofar as limited by the prior art.
This application is based upon and claims the benefit of U.S. provisional application No. 60/822,034, entitled “Thermal Energy Storage and Cooling System with Isolated External Melt Cooling”, filed Aug. 10, 2006, the entire disclosure of which is hereby specifically incorporated by reference for all that it discloses and teaches.
Number | Date | Country | |
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60822034 | Aug 2006 | US |