Abstract
Because of the depletion of the stratospheric ozone layer, CFCs and HCFCs are on the way to the phase out. HFCs are one of the promising alternatives, but they have large global warming potential. From the viewpoints of ozone depletion and global warming, natural working fluids for compression heat pumping systems are being watched with keen interest especially in European countries. In the present study, cycle performances of propane, ammonia and carbon dioxide as a working fluid are calculated, and are compared with those of HCFC22. A theoretical fundamental heat pump cycle and a fundamental cycle with secondary refrigerant are selected for comparison; besides, a liquid injection cycle for ammonia and an internal heat exchange cycle for carbon dioxide are calculated. The effects of heat transfer characteristics and pressure drop in heat exchangers on heat pump performance are evaluated.
