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Condensate heat transfer for transcritical carbon dioxide refrigeration system

Condensate heat transfer for transcritical carbon dioxide refrigeration system description/claims

Benefit is claimed of U.S. Patent Application 60/663,912, entitled “CONDENSATE HEAT TRANSFER FOR TRANSCRITICAL CARBON DIOXIDE REFRIGERATION SYSTEM” and filed Mar. 18, 2005. Copending application docket 05-258, entitled HIGH SIDE PRESSURE REGULATION FOR TRANSCRITICAL VAPOR COMPRESSION SYSTEM and filed on even date herewith, discloses prior art and inventive cooler systems. The present application discloses possible modifications to such systems. The disclosures of said applications are incorporated by reference herein as if set forth at length.

The invention relates to refrigeration. More particularly, the invention relates to beverage coolers.

As a natural and environmentally benign refrigerant, CO2 (R-744) is attracting significant attention. In most air-conditioning operating ranges, CO2 systems operate in transcritical mode. An example of a transcritical vapor compression system utilizing CO2 as working fluid comprises a compressor, a gas cooler, an expansion device, an evaporator and the like (see FIG. 1). The major difference between transcritical and conventional operation is that heat rejection in the gas cooler is in the supercritical region because the critical temperature for CO2 is 87.8 F. Consequently, pressure is not solely dependent on temperature and this opens additional control and optimization issues for system operation.

FIG. 1 schematically shows transcritical vapor compression system 20 utilizing CO2 as working fluid. The system comprises a compressor 22, a gas cooler 24, an expansion device 26, and an evaporator 28. The exemplary gas cooler and evaporator may each take the form of a refrigerant-to-air heat exchanger. Airflows across one or both of these heat exchangers may be forced. For example, one or more fans 30 and 32 may drive respective airflows 34 and 36 across the two heat exchangers. A refrigerant flow path 40 includes a suction line extending from an outlet of the evaporator 28 to an inlet 42 of the compressor 22. A discharge line extends from an outlet 44 of the compressor to an inlet of the gas cooler. Additional lines connect the gas cooler outlet to expansion device inlet and expansion device outlet to evaporator inlet.

An electronic expansion valve is usually used as the device 26 to control the high side pressure to optimize the COP of the CO2 vapor compression system. An electronic expansion valve typically comprises a stepper motor attached to a needle valve to vary the effective valve opening or flow capacity to a large number of possible positions (typically over one hundred). This provides good control of the high side pressure over a large range of operating conditions. The opening of the valve is electronically controlled by a controller 50 to match the actual high side pressure to the desired set point. The controller 50 is coupled to a sensor 52 for measuring the high side pressure.

As the airflow 36 passes over the heat exchanger 28, cooling of the airflow 36 causes the condensation of water out of that airflow. Disposal of that water may need to be addressed. One way involves using the heat rejection heat exchanger to heat the water to induce its evaporation. An example of such a system 60 is shown in FIG. 2.

In the illustrated system 60, components similar to those of the system 20 are shown with like numerals. For illustration, the control and sensor components are hidden. The gas cooler 62 is split into first and second sections 64 and 66. Along the refrigerant flowpath 66, the first section 64 is upstream of the second section 66. The sections 64 and 66 may be along a common air flowpath to receive a common airflow 68 (e.g., driven by a fan 70) or may be on separate air flowpaths (e.g., driven by separate fans). If on a common air flowpath, the first section may be upstream/downstream of the second section.

Water condensed from the airflow 36 is collected by a collection system 80. An exemplary system 80 includes a pan 82 to which the water is delivered. A portion of the first section 64 is positioned to be immersed in a water accumulation in the pan. Heating of the water by the first section 64 encourages evaporation of the water.

For advantageous performance, however, the condensate may preferably be exposed to a more downstream section of the heat rejection heat exchanger. A bottle cooler system includes means for using atmospheric water condensate from the evaporator to draw heat from the condenser.

The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

FIG. 1 is a schematic view of a prior art refrigeration system.

FIG. 2 is a schematic view of another prior art refrigeration system.

FIG. 3 is a schematic view of an inventive refrigeration system.

FIG. 4 is a side schematic view of a display case bottle cooler including a refrigeration and air management cassette.

• Provisional Patent
• Utility Patent

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