Study On Optimization Of System And Components In Compression-Ejector Heat Pump

The ejector is often used in heat pump system instead of traditional throttling parts,playing an important role in decreasing the energy loss.In such a system,the ejector and gas-liquid separator have a significant effect on the system performance.The thermodynamic model of the transcritical CO₂ compression-ejector heat pump system was established.Compared with the conventional system,the effects of discharge pressure,evaporation temperature and outlet temperature of gas cooler were analyzed.The effect of the gas-liquid separator on the system was also analyzed.The results showed that compared with the conventional heat pump system,the COP increased by35.7%～75.2%,the exergy loss decreased by 30.9～130.5k W,the exergy efficiency increased by 8.3%～51.3%;When the efficiency of the gas-liquid separator decreased from 1 to 0.8,the entrainment ratio decreased by 36.3%～64.3%,the COP decreased by6.3%～42.4%.The adjustable ejector was designed.The internal flow condition,the influence of the needle position and the quality of the primary stream were analyzed.It was found that compared with the fixed ejector,the pressure drop through the main nozzle,the throat velocity and gas volume fraction increased by 69.6%,8.2%and 2.4%.When the needle adjustment ranged from 0 to 0.8mm,the motive nozzle flow rate decreased by 0.8%～8.4%,and the entrainment ratio increased by 7%～25.7%.When the quality of the primary stream increased from 0 to 0.4,the gas volume fraction increased,the pressure first decreased and then increased,but the variation of the velocity was opposite,and the entrainment ratio first increased and then decreased,all reaching the extreme value when the quality was 0.1.The preliminary design and optimization of centrifugal gas-liquid separator were carried out,the results showed that compared with the gravity gas-liquid separator,the gas volume fraction of bottom port decreased by 43%.Under the simulated conditions,increasing the diameter of cylinder,decreasing the insertion depth of overflow port and the angle of cone section can increase the liquid volume fraction of bottom port by 57.1%,2.3%and 41.3%,respectively.It is valuable for the optimization design of the transcritical CO₂ ejector-expansion heat pump system,the ejector and the gas-liquid separator.It offers a new thought for the performance improvement of heat pump systems.Figure 47;Table 2;Reference 95...