Experimental Investigation On Mixed Refrigerants For Moderately High Temperature Heat Pump

Moderately high temperature heat pump can produce higher level heat from huge quantity of low temperature waste heat to meet the heat demand of general process,and have a promising development.However,selecting the appropriate working fluids is still an important factor that limits the development of the technology.In this paper,several mixed working fluids were screened out by theoretical calculation.The performance of different working fluids were investigated experimentally under responding condition.Theoretical cycle performances of several refrigerants such as R124,R152a,R245fa,R152a/R124 and R152a/R245fa are calculated and analyzed.And then experiments with the heat source inlet water temperature of 40-50 ? and heat sink inlet water temperature of 70?85 ? were carried out.Working fluids were charged into a 4.5 kW heat pump.Among the pure refrigerants,R152a can't work stably under high temperature condition.R124 performs better than R245fa while heat source inlet water temperature is low.Mass ratios of R152a/R124 were 50/50,30/70 and 20/80 while mass ratio of R152a/R245fa were 30/70,50/50 and 70/30.Results show that R152a/R124(30/70)and R152a/R245fa(30/70)perform better than others considering the heating performance and cycling efficiency.With the heat source inlet water temperature of 50 ? and heat sink inlet water temperature of 70 ?,the electric COP of the two mixtures are both higher than 3.0 with the latter being slightly higher.But as to the heating performance,the former is 19.0%higher than the latter,which could be as high as 15.2 kW.In practice,a heat pump charged with R152a/R124(30/70)is used in photovoltaic solar thermal lithium bromide air conditioning system to produce the heat and cool the heat source water.The hot water outlet temperature is about 90 °C and the heating power reaches 12.9 kW,the electrical COP reaches 2.26 or more,no trip phenomenon appears.