Co2 refrigeration system

Abstract

A CO2 refrigeration system comprises a refrigeration circuit in which circulates CO2 refrigerant between a compression stage in which the CO2 refrigerant is compressed. A condensation stage is provided in which the CO2 refrigerant releases heat and is accumulated in a condensation reservoir. An evaporation stage is provided in which the CO2 refrigerant is expanded to a gaseous state to absorb heat from a fluid for refrigeration, with at least a portion of CO2 refrigerant exiting the evaporation stage being directed to a supra-compression circuit comprising a supra-compression stage in which the portion of CO2 refrigerant is compressed. A heat exchanger is provided by which the compressed CO2 refrigerant is in a heat-exchange relation with a secondary-refrigerant circuit, such that the compressed CO2 refrigerant releases heat to a secondary refrigerant used for heating purposes. Pressure-regulating means control a pressure of the compressed CO2 refrigerant being returned to the condensation stage.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This patent application claims priority on U.S. Patent Application No. 61 / 107,689, filed on Oct. 23, 2008, No. 61 / 166,884, filed on Apr. 6, 2009, and No. 61 / 184,021, filed on Jun. 4, 2009.FIELD OF THE APPLICATION[0002]The present application relates to refrigeration systems, and more particularly to refrigeration systems using CO2 refrigerant.BACKGROUND OF THE ART[0003]With the growing concern for global warming, the use of chlorofluorocarbons (CFCs) and hydrochloro-fluorocarbons (HCFCs) as refrigerant has been identified as having a negative impact on the environment. These chemicals have non-negligible ozone-depletion potential and / or global-warming potential.[0004]As alternatives to CFCs and HCFCs, ammonia, hydrocarbons and CO2 are used as refrigerants. Although ammonia and hydrocarbons have negligible ozone-depletion potential and global-warming potential as does CO2, these refrigerants are highly flammable and therefore represent a r...

AI Technical Summary

Benefits of technology

[0024]In accordance with a second embodiment of the present application, there is provided a method for relieving CO2 refrigerant pressure from evaporators during a defrost cycle, comprising: providing a pressure-relief valve for each evaporator line, the pressure relief-valve opening at a pressure threshold; feeding CO2 refrigerant to at least one evaporator in the evaporator line to defrost the evaporator; exhausting the evaporator from the CO2 refrigerant with the pressure-relief valve when the CO2 refrigerant pressure is above the pressure threshold; and directing the exhausted CO2 refrigerant to an accumulator in a refrigeration cycle.

Problems solved by technology

Although ammonia and hydrocarbons have negligible ozone-depletion potential and global-warming potential as does CO2, these refrigerants are highly flammable and therefore represent a risk to local safety.

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