Defrost for transcritical vapor compression system
AssigneeThermo King Corporation
InventorsMichal Hegar, Marketa Kopecka, Michal Kolda, Vaclav Rajtmajer
Life of this patent
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Abstract
A method of defrosting a transcritical vapor compression system having a compressor for compressing a refrigerant, a first heat exchanger for cooling the refrigerant during a cooling mode, an expansion valve for decreasing the pressure of the refrigerant, and a second heat exchanger for cooling a space during the cooling mode. The method includes attaining a superheated refrigerant condition in a defrost mode of the transcritical vapor compression system and defrosting the second heat exchanger in the defrost mode by directing the superheated refrigerant to the second heat exchanger without bypassing the first heat exchanger.
Claims19
A method of defrosting a transcritical vapor compression system operable in a cooling mode and a defrost mode, the transcritical vapor compression system having a compressor for compressing a refrigerant, the compressor having a compressor inlet and a compressor outlet and operating at a first speed/frequency during the cooling mode, a first heat exchanger for cooling the refrigerant during the cooling mode, an expansion valve for decreasing the pressure of the refrigerant, the expansion valve having a variable opening, and a second heat exchanger for cooling a space during the cooling mode, the method comprising:
- decreasing the speed/frequency of the compressor during the defrost mode to a second speed/frequency lower than the first speed/frequency and greater than zero;
- directing a superheated refrigerant gas from the compressor directly to the first heat exchanger during the defrost mode, then directing the superheated refrigerant gas from the first heat exchanger directly to the expansion valve during the defrost mode, then directing the superheated refrigerant gas from the expansion valve directly to the second heat exchanger during the defrost mode;
- and
- defrosting the second heat exchanger with the superheated refrigerant gas.
A transcritical vapor compression system, comprising:
- a compressor for compressing a refrigerant, the compressor having a compressor inlet and a compressor outlet;
- a first heat exchanger for cooling the refrigerant;
- an expansion valve for decreasing the pressure of the refrigerant, the expansion valve having a variable opening;
- a second heat exchanger for heating the refrigerant;
- and
- a controller programmed to decrease the speed/frequency of the compressor during a defrost mode, programmed to determine a desired superheat temperature, programmed to compare the desired superheat temperature with a measured temperature proximate the compressor inlet, and programmed to adjust the expansion valve based on the comparison between the desired superheat temperature and the measured temperature during the defrost mode,
- wherein the controller is programmed to direct a superheated refrigerant gas from the compressor directly to the first heat exchanger during the defrost mode, then direct the superheated refrigerant gas from the first heat exchanger directly to the expansion valve during the defrost mode, then direct the superheated refrigerant gas from the expansion valve directly to the second heat exchanger during the defrost mode.
Dependencies are inferred from the claim text.