Integration of a Thermoelectric Subcooler into a Carbon Dioxide Transcritical Vapor Compression Cycle Refrigeration System

Abstract

A thermoelectric (TE) subcooler was designed and fabricated to subcool CO2 exiting a gas cooler of a transcritical vapor compression cycle test system. The thermoelectric modules operated at efficiencies greater than the baseline system, increasing capacity and the overall coefficient of performance (COP) of the entire system. Subcooling of the CO2 before the expansion device led to a reduced optimum high side pressure, resulting in greater COP improvement that cannot be achieved in conventional refrigerant vapor compression systems utilizing a TE Subcooler. Improvements in COP of 10% were demonstrated with a corresponding capacity increase of 13%. A capacity increase of 24% was demonstrated at a comparable COP as the baseline system. Theoretical analysis of a combined Expander-TE Subcooler system, in which the electric power required by the TE Subcooler is provided by an expander-generator, was shown to provide a 30% increase in COP with a corresponding 24% increase in capacity.