Theoretical study of a novel oil-free co-rotating scroll compressor integrated into a hybrid absorption heat pump cycle.

Hybrid absorption heat pumps (Osenbrück cycle and Hybrid wet compression cycle) are known for high temperature lifts, low-pressure ratios and wide capacity control. They are well suited for processes with the occurrence of significant heat sink and heat source temperature glides. Environmentally friendly working fluids such as ammonia/water mixtures offer advantages for system performance and play an important role for the future of heat pump applications. However, the main challenges of these cycles are the requirement of oil-free compressors suitable for high temperature lifts that may cope with two phase flows. In this paper a theoretical integration of a novel oil-free co-rotating scroll compressor into a Hybrid absorption heat pump (for cooling and heating) is presented. This compressor has been experimentally characterized and modeled with air and varying rates of water ingestion; the main advantages are that it can operate in both dry and wet conditions without additional internal lubrication. Also, the absence of lubricant allows the oil-free compressor to be used in refrigeration heat pumps. Maximum COP values of 3.3 and 4.3 are determined for cooling and heating mode, respectively. The cycle operates in cooling mode with sink water temperatures of 45°C/70°C and chilled water temperatures of 20°C/6°C, while in heating mode with chilled water of 80°C/40°C and heating production from 80°C to 175°C. Maximum temperature lifts of 56K for cooling mode and 110K for heating mode are determined.