Heat Exchanger Design for CO2 Cycle with a Linear Compressor

Abstract

Hermetic linear compressors already have been developed for subcritical cycles, especially for small-capacity refrigeration systems, which have a refrigeration capacity less than 500 W and have demonstrated better performance potential than conventional compressors. In this paper, the performance potential of a transcritical carbon dioxide (CO2) cycle with a linear compressor is explored for medium-temperature refrigeration systems, which have a return air temperature range from −2°C to 6°C, through CO2 cycle simulation using compressor efficiencies measured. In addition, the design of the heat exchanger for such systems was practiced. The simulated results of the transcritical CO2 cycle performance showed that the cooling capacity was 235 W at 40.5°C ambient temperature and the coefficient of performance was 1.31 at 32.2°C ambient temperature. The heat exchangers were then designed using a verified heat exchanger design software. As a target application, a 200 liter effective volume refrigerator cabinet was selected, and its refrigeration load was evaluated by using load calculation software. When the CO2 linear compressor with suitably designed heat exchangers was applied to the selected refrigeration cabinet operating at medium temperature refrigeration conditions, the simulated results showed that the designed CO2 system based on a linear compressor could provide sufficient refrigeration capacity.