Study On Flow And Heat Transfer Characteristics Of Gas/Liquid Pump Coupled Annual Energy Recovery System

It is an effective measure to reduce the energy consumption of air conditioning system by recovering some energy from the exhaust air by energy recovery device.The pump driven loop heat pipe energy recovery device uses phase change heat transfer,which has very good heat transfer capacity.There are two driving modes,which are driven by liquid pump and by gas pump.This paper studies the heat transfer characteristics and the temperature difference condition of the two kinds of heat pipe energy recovery devices in summer and winter working condition through simulation and experimental research.A gas/liquid pump coupled driven multi loop heat pipe energy recovery device is proposed,which is made by coupling the two loop heat pipes in parallel,and the simulation and experimental research are carried out.The details are as follows:（1）The mathematical model of pump driven loop heat pipe energy recovery device is established,and the influence of refrigerant flow,indoor and outdoor temperature difference on the operating characteristics of the two kinds of energy recovery devices is analyzed.The results show that: for the gas pump driven loop heat pipe,in summer,the cooling capacity and EER of the device increase with the increase of temperature difference;in winter,the heating capacity of the device first increases steadily with the increase of temperature difference,when it increases to a certain value,the temperature difference continues to increase,the heating capacity tends to be stable,and EER increases with the increase of temperature difference.Increasing the refrigerant flow can improve the heat transfer of the device,but it will lead to the decrease of EER.For the liquid pump driven loop heat pipe,the heat transfer,temperature efficiency and EER of the device increase with the increase of temperature difference in summer and winter.Increasing the refrigerant flow has little effect on the heat transfer of the device,but it will lead to the decrease of EER.（2）The performance of three kinds of pump driven loop heat pipe energy recovery devices under different temperature difference was compared and analyzed by using the simulation model.The results show that the performance of the gas pump driven loop heat pipe is better than that of the liquid pump driven loop heat pipe in summer;the performance of the gas pump driven loop heat pipe is better than that of the liquid pump driven loop heat pipe in winter when the temperature difference is small（?< 24.5℃）,while the performance of the liquid pump driven loop heat pipe is better in winter when the temperature difference is large（? 24.5℃）.The gas/liquid pump coupled driven multi loop heat pipe energy recovery device has ideal heat recovery effect.In summer and winter working condition,the heat transfer and temperature efficiency of the device is higher than that of single loop gas pump driven loop heat pipe and liquid pump driven loop heat pipe.（3）The test results show that the cooling capacity and temperature efficiency of the coupled system are higher than those of the gas pump system and the liquid pump system in summer.The EER of the gas pump system is slightly higher than that of the coupled system,and the EER of the liquid pump system is significantly higher than that of the other two systems.In winter,the heating capacity and temperature efficiency of the coupled system is the highest,and that of the liquid pump system is the smallest,but the heating rate of the gas pump system is less than that of the other two systems.The EER of the gas pump system is slightly higher than that of the coupled system,and the EER of the liquid pump system is significantly higher than that of the other two systems.（4）Considering the temperature efficiency and system energy efficiency,in summer,when the temperature difference is less than 5.3℃,the gas pump system should be used;when the temperature difference is greater than 5.3℃,the coupled system should be used;in winter,when the temperature difference is less than 9.5℃,the gas pump system should be used;when the temperature difference is greater than9.5℃,the coupled system should be used.