Experimental investigation on performance of heat pump air circulation evaporating separation system for saline wastewater treatment

There is a gradual increase in the discharge of saline wastewater which is harmful to the environment and human health. A novel heat pump air circulation evaporating separation (HP-ACES) system for saline wastewater treatment is proposed and experimentally investigated. The results show that the system evaporation efficiency ( SEE ) initially decreases before increasing with the expansion valve opening at different refrigerant charges. However, the SER increases by 0.67 kg/h at 1.21 kg refrigerant charge while they descend and then rise at 1.53 and 1.86 kg refrigerant charges. Noted that the effects of expansion valve opening on the SER and SEE are lessened with refrigerant charge. Moreover, there exist the optimal values of total air flow and air flow proportion of packing concentration tower at which the SER and SEE peak, and both of the solution concentration and cooling water flow negatively affect the SER and SEE . Besides, compared with similar evaporating separation systems, the HP-ACES system has higher energy efficiency for treating high saline wastewater and the SEE ranges from 0.86 to 1.64 kg/kWh (5–25 % CaCl 2 solution). However, the SEE is low, and it is necessary to reveal the cause and propose the optimization schemes in the future. • A novel heat pump air circulation evaporating separation system is experimented. • The maximum SER and SEE are 2.66 kg/h and 1.64 kg/kWh. • Effect of expansion valve opening on SER relies on refrigerant charging quantities. • There is an optimum total air flow at which SEE and SER peak. • Solution concentration and cooling water flow has negative effects on system.