Sharif Digital Repository

This paper addresses the challenge of improving the performance of heat pumps (HPs) in cold-climate conditions by applying refrigerant mixtures. The potential benefits of implementing R-32/CO2 zeotropic refrigerant mixtures in three different residential air-source HPs for cold climates are studied. The cases considered are conventional residential HP, HP with a variable mixture control system, and HP with a variable compressor speed. The seasonal performance of a heating system with these air-source HPs, supplemented with an auxiliary electric heater, is studied in the cold-climate city of Montreal, Canada. To this aim, a detailed screening HP model previously developed is modified and... 

Effects of the amount and mode of input energy to an active multi-stage solar still were investigated in this work. To control the input energy, an electrical heater controlled by a PLC was utilized to simulate the energy absorbed by solar collectors. The study of the amount of input energy indicated that the freshwater production was a quadratic function of the collector over basin area (CBA) ratio. It was also found that stages 1 to 4 produced about 36%, 26%, 20% and 18% of the overall yield, respectively. Moreover, the effect of employing a thermal energy storage (TES) on the system performance was studied by comparing the mode of feeding energy according to the daily solar radiation...