ANALYSIS OF HIGH TEMPERATURE HEAT PUMPS APPLYING NATURAL WORKING FLUIDS

A cascade high-temperature heat pump applying propane as working fluid in the lower vapor compression cycle and butane as working fluid in the upper vapor compression cycle has been proposed. The task for the heat pumps was to heat up water from 95 degrees C to 115 degrees C while evaporating temperatures between 0 degrees C and 50 degrees C were analyzed to find at which temperature the combined cascade heat pump would be preferable versus a single working fluid system. The cascade system has been numerically analyzed, and COP's as high as 2.6 were possible to achieve with an evaporating temperature of only 20 degrees C. The heating capacity of the heat pump was calculated based on the commercially available compressor units and was found to be approximately 370 kW at an evaporating temperature of 20 degrees C.