Development of a heat pump system for high-temperature heat supply with heat recovery using methanol as the refrigerant.

High-temperature heat supply in the range of 100 to 200°C is required for some processes in industries, such as washing, drying, and sterilizing. Efficient energy utilization is an important concern for these processes. In this study, a heat pump system operating between two heat sources at 100 and 200°C was constructed as a feasibility study. Firstly, methanol is selected as the refrigerant in a preliminary survey from the view point of similarities to widely-used refrigerants. The constructed system was a simple refrigerating cycle consisting of a two-stage reciprocating compressor and heat exchangers. In the experiments, it could be demonstrated by the system to heat silicone oil to 200°C with the evaporating temperature at 100°C. The coefficient of the performance (COP) of the operation was 2.16 due to low adiabatic efficiency of the compressor. It is expected from the analysis of loss in each component that this system can achieve a COP over 3 by improving the overall adiabatic efficiency of the compressor and by deducing heat loss from the connecting section from the compressor to condenser.