Regenerator performance using freezing concentration for heat source tower heat pump system

Freeze concentration has a good regeneration effect and is easy for latent heat utilization. The electronic expansion valve opening has a great impact on the icing process. Hence, to investigate variations in the freezing process and gain the optimum regeneration effect, a solution regenerator was tested under different system-side control strategies. The solution volume flow was 5 m3/h and the electronic expansion valve opening degree (OEEV) was from 100% to 50%. For ice-covering growth, ice in low opening degree spent a long time to cover the plate. The area of ice under 100% to 65% OEEV was 1.43 times that under 50% OEEV. Peak velocities from 100% to 50% OEEV all appeared in the early stage of icing development. Moreover, the low opening degree made the ice distribute unevenness. The percentage slope of 100% OEEV was 1.23% and that of 50% OEEV was 3.46%. In addition, decreasing ice thickness uniformity was beneficial to the separation process. The separation ratio from 100% to 50% OEEV was 49.51%, 51.67%, 57.88%, and 74.54%, respectively. Both the low average thickness growth rate and high separation ratio were beneficial to increase the regeneration concentration. The effective specific ice production rate was from 100% to 50% OEEV was 5.99 kg/kWh, 6.18 kg/kWh, 6.94 kg/kWh, and 6.88 kg/kWh, respectively. Results showed that 65% OEEV operation was optimum for the solution regenerator unit using freeze concentration.