Research On Application Of Liquid-vapor Separation In Air Source Heat Pump Water Heater

Air energy,known as a renewable energy source,is becoming increasingly valued in the current context,where environment is commonly emphasized.Air source heat pump water heater(ASHPWH)is recognized as a remarkable technology due to its ability of ener gy saving and has thus been widely employed in various field.In this paper,the simulations and experiments carried out of the ASHPWH.In the experiment,ASHPWH is operated under different conditions.The experimental results show that during operations under changing conditions,the average heat capacity is improved by 9.36%,whereas the heating time is shortened by 10.71%.Additionally,the COP is improved by 0.39%.The main reason thereof is that the average evaporation temperature is increased by 3.39℃ and the refrigerant mass flow rate is increased by 1.93g/s.Comparison experiment between ASHPWHs equipped with liquid-vapor separation microchannel condenser(LMC)and convention microchannel condenser(CMC)respectively is further studied.Furthermore,in order to analyze the interactions between condenser/water tank and system performance,time-divided tests are supplemented based on the standard procedure.It is found that the average power of the system equipped with LMC(LHPWH)is 4.31% lower compared to the system equipped with CMC(CHPWH),whereas the COP of LHPWH is increased 4.88% in comparison to CHPWH.Specifically,the LMC has lower pressure drop and less severe flow misdistribution than the CMC.Moreover,less stratification and higher overall heat transfer coefficients are also observed in the LMC.FLIR confirms that there exists the liquid-vapor separation in the LMC.It is expected to obtain higher performance if the path arrangements of LMC is optimized.In the simulation,this paper establishes a numerical calculation model of the condenser and the water tank having dynamic feature.It is verified using the experimental data obtained in the study.The results show that the maximum error between the calculation results of the model and the experimental data is within 30%,and the average error is with 20%.The validated model then used to perform pass arrangement optimization of CMC and LMC.The results indicate that the number of pass runs has a great impact on the performance of the condenser,and LMC has great potential in the pass arrangement optimization.The research results above illustrate that the liquid-vapor separation condensation technology can also reduce the pressure drop and increase the heat transfer coefficient in unsteady systems such as ASHPWH.It is concluded that the application of LMC with reasonable pass arrangement in ASHPWH will significantly improve its system performance.