Performance Analyses for the Design of a Machine Tool Cooler System Retrofitted with Eco-Friendly Refrigerants

The machine tool coolers are the best managers of coolant temperature in avoiding the deviation of spindle centerline for machine tools. Machine tools with more accurate and stable machining precision for the working piece cannot be developed without the accurate control of the temperature rise by appropriate cooling. However, the machine coolers are facing the compressed schedule to phase out the HCFC refrigerant. Therefore, it's essential to apply eco-friendly refrigerants to replace HCFC refrigerant. In this study, both the first law efficiency and second law efficiency of the machine tool cooler system have been studied comprehensively. The exergy destruction rate of each component and the parametric study of overall system after retrofitting have been investigated and compared thoroughly. Experiment investigation has been conducted as well to evaluate the first law efficiency and second law efficiency (exergy efficiency) of the retrofitted cooler system. The results reveal that the best performances in terms of coefficient of performance (COP) and exergy efficiency could be identified under different operating conditions for HCFC22 and its alternatives. The compressor and the heat exchanger must be optimized after retrofitting because of higher exergy destruction rate. It is feasible to identify the losses in system components and to improve the thermodynamic efficiency for the retrofitted machine cooler system.