Experimental Investigation on the Performance of a Novel Thermo-Mechanical Refrigeration System Driven by an Expander-Compressor Unit

In this work, the performance of innovative thermo-mechanical refrigeration (TMR) system is investigated experimentally. The TMR system consists of power loop coupled with cooling loop through an expander-compressor unit (ECU). The ECU function is to convert the thermal energy supplied to the power loop to heat a pressurized working fluid into mechanical energy to compress the refrigerant of the cooling loop. In the present setup, the power loop is replaced with an air compressor to provide pressurized air to drive the ECU at a desired pressure of 620 kPa. Using R134a as a refrigerant, the performance of the ECU-based refrigeration system is systematically tested for various operating conditions including refrigerant mass, evaporator pressure, temperature and flow rate of the water used for evaporation and condensation loads. All tests are performed at two operating frequencies of the ECU (0.50 Hz and 0.33 Hz). At the optimum refrigerant charged mass, the results show that the average coefficient of performance (COP) at 0.50 Hz varies (over a wide range of testing conditions) from 1.57 to 2.73 at cooling capacity from 0.14 kW to 0.56 kW. At 0.33 Hz, the COP varies from 1.56 to 2.39 at cooling capacity from 0.25 kW to 0.50 kW. Moreover, the evaporator temperature reaches less than -10oC at 0.50 Hz and -9.60 oC at 0.33 Hz. These experimental results prove that the COP of the ECU-based refrigeration system is three times higher than the ejector-based systems and 2.70 times higher than the organic Rankine cycle-based systems