Performance improvement of an ejector cooling system with thermal pumping effect (ECSTPE) by doubling evacuation chambers in parallel

Abstract

The existing ejector cooling system with thermal pumping effect (S-ECSTPE) operates without consuming electricity, but has waste problems of thermal energy and chilling water. An innovative ECSTPE with double evacuation chambers in parallel (D-ECSTPE) can effectively mitigate these waste problems. The high-pressure vapor with high temperature (HPVHT) in one evacuation chamber, which is directly chilled by chilling water in the S-ECSTPE, is reused in the D-ECSTPE to pre-pressurize refrigerant in the other evacuation chamber. Performance improvement mechanisms of the D-ECSTPE are explained from both thermal energy transfer and mass transfer of the HPVHT. Case studies showed that the severer the waste problems of the S-ECSTPE, the greater COP increase and reduction in chilling water demand achieved by the D-ECSTPE. Also, the D-ECSTPE performed well with environment-friendly refrigerants (e.g., R1234yf, R161 and R1234ze(E)), which were unsuitable for the S-ECSTPE due to severe waste problems. Compared to the S-ECSTPE, the D-ECSTPE with R1234yf, R134a, R161, R1234ze(E), R1234ze(Z), R1233zd(E), R365mfc and R141b increased the COP by at least 49.44%, 26.30%, 22.33%, 19.38%, 4.39%, 3.55%, 2.14% and 1.77%, respectively, and reduced the chilling water demand by at least 29.77%, 18.04%, 15.55%, 13.86%, 3.36%, 2.76%, 1.72% and 1.37%, respectively. In all cases, the D-ECSTPE reduced the wasted thermal energy and chilling water of the S-ECSTPE by at least 65.83% and 81.14%, respectively, and its exergy efficiency was generally superior to those of the S-ECSTPE and conventional ejector cooling system. An additional increase in the number of paralleled evacuation chambers can further improve the system performance.