A novel CO2 refrigeration system achieved by CO2 solid–gas two-phase fluid and its basic study on system performance

In this report, a new CO2 refrigeration system is introduced, which can achieve a refrigeration capability below the CO2 triple point of −56.6 °C. The proposed CO2 refrigeration system consists of two thermodynamic cycles arranged in cascade, where one is a CO2 trans-critical cycle and another is a trans-triple-point cycle. An experimental set-up is constructed and tested in order to obtain a basic knowledge about this CO2 system. Based on the measured data, it is concluded that the built CO2 refrigeration system can operate continuously and stably, although dry ice particles exist in the closed CO2 loops. An average COP (a ratio of cooling energy to the compressor power consumption) is measured at 2.45 in the present experiment range for the low-pressure system of the experimental set-up. In addition, the influence of the condensation temperature on the refrigeration cycle is investigated and more studies are needed for the future optimization work.