This paper presents a semi-empirical model of scroll compressors and proposes a methodology in order to extend this model to vapor-injection scroll compressors. The model takes into account the ideal evolution of the refrigerant throughout the compressor and considers the main sources of losses in the compression process. The model is able to predict the compressor and volumetric efficiencies in terms of ten empirical parameters, which have a direct physical interpretation. For the model validation, a series of four non-injected scroll compressors of different capacities were tested using R-290 and a scroll compressor with vapor-injection (SCVI) was characterized using R-407C. Results show a correct agreement between the experimental and calculated compressor efficiencies, with a maximum deviation of ±5%. Furthermore, the model estimates accurately the discharge temperature of the refrigerant, compressor power input, and refrigerant mass flow rate in the suction and injection port. Finally, the SCVI model response was evaluated by varying the intermediate pressure and the injection superheat.

Traditional heat pumps designs have been optimized for heating applications based on small secondary temperature lifts (around 5 K); however, in applications with other characteristic temperature lifts, different design criteria could be required. For instance, transcritical cycles have demonstrated to have a high efficiency for domestic hot water production with high water temperature lifts. This work presents the experimental results of a new water-to-water heat pump composed by the basic heat pump components (condenser, compressor, evaporator, expansion valve and liquid reliever) able to adapt its performance depending on the required water temperature lift. Domestic hot water production from grey water waste heat recovery has been chosen as experimental application to test this heat pump. Results show COP values up to 5.5 at the design condition (20-15ºC at the inlet-outlet of the evaporator and 10-60ºC at the inlet-outlet of the condenser) and an optimal degree of subcooling of 47K.

No abstract