Experimental And Model Study Of Rear Door Type Heat Pipe System Based On Micro-channel Evaporator

In this paper,a rear door type heat pipe system based on micro-channel evaporator is proposed.A micro-channel heat exchanger is used as the system evaporator.A plate heat exchanger is used as the system condenser.The system has two characteristics such as high heat transfer efficiency of micro-channel heat exchanger and better air flow organization of the rear door type,which is of great significance to cope with the heat dissipation of the high heat density cabinet and to improve the energy efficiency of the data center.In order to provide support and guidance for the practical application and design optimization of the system,the experimental and theoretical model of the rear door type heat pipe system based on micro-channel evaporator is studied in this paper.The effect of each system parameter on the heat transfer performance was experimentally analyzed.It was found that: 1)With the increase of the refrigerant filling rate,the heat transfer capacity of the system first increases and then decreases,and there is an optimal refrigerant filling rate.For example,the optimal refrigerant filling rate of the system using R22 as working fluid under standard conditions is 65%~75%.At this time,the heat exchange capacity reaches a maximum value of 7.9kW,and the temperature of the outlet air at each position of the rear door is the lowest;The temperature difference of the working fluid reaches the minimum.2)As the air volume of the rear door increases,the heat transfer capacity of the system increases,but the EER of the system changes smoothly and basically does not change.3)The heat transfer capacity of the system increases with the increase of the inlet air temperature of the rear door,and increases with the decrease of the inlet water temperature of the condenser,but the increase rate of the heat transfer capacity between the two decreases gradually.In addition,through the analysis of experimental data to analyze the effects of different working conditions and types of working fluid on the optimal refrigerant filling rate of the system,the following conclusions are obtained: 1)The optimal refrigerant filling rate increases with increasing of the inlet air temperature,and then its remains unchanged when the inlet air temperature beyond 40?.2)The optimal refrigerant filling rate increases with the increasing of inlet water temperature of the condenser.3)The optimal refrigerant filling rate for R134 a is basically in accordance with that for R22,while the maximum heat transfer capacity between them are different.In terms of theoretical model research,the heat transfer theory of the rear door type heat pipe system is first introduced,and the heat transfer calculation model of the system evaporator and condenser is established.Then,a numerical model of the micro-channel rear door type evaporator based on the Mixture model was established.The flow state of the working fluid in the evaporation section of the system was simulated by using the model.The bubble flow,plug flow,and ring shape flow etc appeared in the micro-channel rear door type evaporator.The flow pattern changes steadily,and the optimal refrigerant filling rate of the system is 58% to 62% by using the numerical model.Finally,the optimal refrigerant filling rate of the system is calculated to be 106% by establishing an optimal refrigerant filling rate calculation model,which is larger than the experimental value of the optimal refrigerant filling rate of the system.