REFRIGERANTS AND HEAT PUMPS FOR EFFICIENT USE OF LOW GRADE THERMAL ENERGY

Low grade thermal energy, such as solar energy, waste heat from industries and geothermal energy, extensively exists in the environment. Heat pumps (HPs), such as vapor compression, absorption, and adsorption HPs, can upgrade the low temperature thermal energy into high temperature heat for central heating or industrial manufacturing processes. The selection of suitable cycles and refrigerants is important for getting good performance of HPs. In this paper typical refrigerants of vapor compression, absorption, and adsorption HPs, such as R152a, R1233zd (E), R1234yf, R1234ze, R134a, R245fa, R717, R718, and R744, methanol, etc., are analyzed. Various HPs and refrigerant options are compared, and different factors, which are low grade heat sources, heat sinks, and temperature lifts, are analyzed. A broad-spectrum diagram of HP applications is provided for different working modes.