Embodiments of the invention relate to refrigeration systems and in particular to a refrigeration system including a phase-change material.
Refrigeration systems compress and circulate a refrigerant throughout a closed-loop heat transfer fluid circuit to transfer heat to and from a climate controlled space. In a basic refrigerant system, a heat transfer fluid vapor is compressed in a compressor from a lower pressure to a higher pressure and delivered to a downstream heat rejection heat exchanger, commonly referred to as a condenser. From the condenser, where heat is typically transferred from the heat transfer fluid to an ambient environment or to a secondary heat transfer fluid, high-pressure refrigerant flows to an expansion device where it is expanded to a lower pressure and temperature and then is routed to an evaporator. In the evaporator, the heat transfer fluid vaporizes and cools the air in the conditioned environment or the secondary heat transfer fluid. From the evaporator, the refrigerant vapor is returned to the compressor.
Embodiments of the invention include a thermal energy storage assembly having a first pipe configured to have a heat transfer fluid flow through a bore of the first pipe. A second pipe surrounds the first pipe. A phase change material fills the space between the first pipe and the second pipe, the phase change material storing thermal energy from the heat transfer fluid.
Additional embodiments include a refrigeration system including a cooling unit configured to cool a heat transfer fluid and a thermal energy storage assembly. The thermal energy storage assembly is configured to circulate the heat transfer fluid from the cooling unit and back to the cooling unit to refrigerate a compartment. The thermal energy storage assembly includes a first pipe configured to have the heat transfer fluid flow through a bore of the first pipe and a second pipe surrounding the first pipe. A phase change material fills the space between the first pipe and the second pipe and stores thermal energy from the heat transfer fluid, or releases thermal energy to the heat transfer fluid.
Additional embodiments of the invention include a mobile refrigeration vehicle including a refrigerated compartment having a thermal energy storage assembly attached to at least one wall of the refrigerated compartment. The thermal energy storage assembly includes a first pipe configured to have the heat transfer fluid flow through a bore of the first pipe and a second pipe surrounding the first pipe. A phase change material fills the space between the first pipe and the second pipe and stores cold thermal energy from or release cold thermal energy to the heat transfer fluid.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
Conventional refrigeration systems for vehicles utilize eutectic plates filled with mineral salt solutions to provide refrigeration. Embodiments of the present invention provide refrigeration using a first pipe enclosed within a second pipe, with a phase change material filling the area between the two pipes. A heat transfer fluid flows within the first pipe and the phase change material exchanges heat with the heat transfer fluid to maintain a target area at a desired temperature.
The heat transfer fluid is transmitted from the evaporator assembly 120 to the thermal energy storage assembly 130. In one embodiment, the thermal energy storage assembly 130 is located in a compartment that is to be refrigerated. For example, in one embodiment, the thermal energy storage assembly 130 is located in the walls of the compartment, or the thermal energy storage assembly 130 may be attached to the walls of the compartment. Valves 131 and 132 control the flow of the heat transfer fluid to and from the thermal energy storage assembly 130. A pump 133 may be used to control a rate of flow of the heat transfer fluid to and from the thermal energy storage assembly 130. The cooling load split between cooling return air and the heat transfer fluid can be controlled by varying the flow rate of the heat transfer fluid. The pump 133 is turned on when the thermal storage is charged and discharged through the evaporator 120. The cooling of the air from the thermal energy storage assembly 130 can also be done by running the pump 133 to circulate the heat transfer fluid between the thermal energy storage assembly 130 and the evaporator 120, while the compressor 124 is turned off, or with the compressor 124 turned on to boost the cooling capacity with the stored cold thermal energy.
In the present specification and claims, a phase change material is defined as a material that has a melting temperature (from solid to liquid) at which it absorbs heat while maintaining a substantially constant temperature. In other words, as the phase change material is heated up from a temperature below the melting temperature to the melting temperature, the temperature of the phase change material rises accordingly. However, when the phase change material reaches its melting temperature, the temperature of the phase change material remains substantially the same as it absorbs heat, before all the phase change material becomes liquid. Accordingly, the phase change material located between the first pipe 221 and the second pipe 222 of the present invention acts as a robust refrigeration material that is able to absorb heat from an atmosphere that is being cooled, and that may be refreshed, or cooled, by the heat transfer fluid in the bore 223 of the first pipe 221.
In embodiments of the invention, the first and second pipes 221 and 222 may be made of any material, according to the design considerations of the refrigeration system in which the thermal energy storage assembly 220 is located. In one embodiment, one or both of the first and second pipes 221 and 222 is made of metal. In another embodiment, one or both of the first and second pipes 221 and 222 is made of plastic or another polymer. In addition, while the first and second pipes 221 and 222 are illustrated as having circular cross-sectional shapes, embodiments of the invention encompass pipes having any cross-sectional shapes, including squares, ovals, any other geometric shape, or any other shape.
While the vehicle 400 of
Embodiments of the present invention include a unique configuration of an evaporator cooling a load, such as air circulating inside a truck, container or other compartment. The configuration includes charging a thermal storage and cooling the compartment air in a parallel mode. The refrigerant cools the air at the same time cools the heat transfer fluid which is circulated to the thermals storage assembly to charge the phase change materials. In embodiments of the invention, the stored refrigeration capacity can be discharged to the load either with or without the compression unit running, effectively increasing the maximum capacity for faster pull down.
In one embodiment, some of the circuits of an evaporator coil for a heat transfer fluid flow though to charge/discharge the thermal storage. This configuration effectively has better thermodynamic efficiency compared with a configuration using multiple heat exchangers. In addition, in one embodiment, the thermal storage (e.g. phase change material) is embedded in the insulation wall, reducing the cost for insulating an independent storage container. In one embodiment, plastic materials are used for the storage devices to eliminate metal corrosion. For example, referring to
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
Filing Document | Filing Date | Country | Kind |
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PCT/US2014/043834 | 6/24/2014 | WO | 00 |
Number | Date | Country | |
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61871666 | Aug 2013 | US |