Research On Optimal Design Of Ejector In Transcritical R744 Water Source Heat Pump

Due to the refrigerant widely used at present has a high greenhouse effect,the natural working medium,R744,has attracted extensive attention because of the good environmental characteristics.But there are large throttling losses in transcritical R744 heat pump system.So that its energy efficiency is lower than the conventional heat pump system.Using ejector instead of throttle valve can significantly improve the system performance.But there are complex phenomena such as phase transition,shock wave and exergetic flow in the ejector.The geometry and size of the ejector have a great influence on the performance of the ejector.It is of great significance to study the flow mechanism of refrigerant in ejector and optimize its design.Through experiments,the actual operation performance of the transcritical R744 water source heat pump system was researched under typical heating and cooling working conditions.It was found that the addition of internal heat exchanger in the system can increase COP by 8%?10% and reduce exergy loss by 6%?12%.Through system thermodynamic analysis,the addition of ejector can increase COP by 11.8% and reduce exergy loss by 34%.The physical model and the mathematical model of two-phase flow ejector was established.The turbulence model and the grid irrelevance were investigated.The variations of internal pressure,velocity,volume fraction,exergy flux,shock wave and other parameters in the ejector were analyzed.The shape of suction chamber and mixing chamber was optimized through numerical simulation.It was found that the performance of cylindrical suction chamber is better than that of conical,and the performance of singleangle receding mixing chamber is better than that of double-angle one.The geometric parameters of the ejector mixing chamber were optimized.It was found that the area ratio and the length and diameter ratio have a great influence on the ejector performance.The results show that the optimal area ratio value is 8.3,and the optimal length and diameter ratio value is 8.1.Figure 47;Table 1;Reference 98...