Numerical Simulation For Flow And Heat Transfer Characteristics Of Inlet Structure In Porous Wick Micro-channel Evaporator

The porous wick micro-channel evaporator widely applied in high power electronic equipment cooling systems can not only supply the driving force,but also has amounts of features ranging from high cooling efficiency,high reliability to small size and so on.It has become an important way to control the interface temperature in high heat flux thermal management.In this paper,thyristor which is popular in electronics industry is supposed to be an object whose single side is cooled and a three-dimensional model of the porous wick micro-channel evaporator is established.ANSYS is adopted to investigate the flow and heat transfer in the porous wick micro-channel evaporator.First of all,the condition of steady-state single-phase flow in the evaporator is simulated to analyze the influence of three structure parameters(groove width Ww,groove depth Hv and fin width Wf)on the flow and heat transfer characteristics.The numerical results show that the effect of three structure parameters on the flow and heat transfer is significant.The small groove width,large groove depth and small fin width can effectively improve the heat transfer performance and ensure the evaporator flow resistance in a reasonable range.Furthermore,the optimum groove size of the porous wick micro-channel evaporator is supposed to be Ww=0.7mm,while the depth of the channel is Hv=2mm and the width of the fin is Wf=0.7mm.With the optimum channel size,the influence of heat flux on flow and heat transfer in the single-phase cooling process is discussed.The results show that although the increase of the inlet flow rate with various heat flux can improve the performance of heat exchanging,the flow resistance will gain a sharp growth,too.Meanwhile,when the heat flux is within 35.4 W/cm~2,from the results of single-phase flow simulation,the temperature and flow resistance of the evaporator can be kept within a reasonable range.Secondly,the physical process of evaporation in porous wick micro-channel evaporator under constant heat flux condition is studied by means of Mixture model.The influence of the inlet flow rate,storage chamber position and the entrance location on the heat transfer performance of the evaporator is analyzed in detail.After that,the temperature field,velocity field and liquid-vapor interface position in evaporator under different structure conditions were obtained.Numerical results show that the inlet flow rate of the evaporator has a significant effect on flow and heat transfer performance.The higher inlet flow rate,the better temperature performance,the larger flow resistance of the evaporator and the higher stable position of liquid-vapor interface in the wick.Hence there exists an optimal inlet flow rate v=4.2m L/min when the evaporator heating temperature of surface meets requirement and the velocity of the outlet gas phase is located in a reasonable range and the liquid-vapor interface is stable at approximately 70 percent height of the wick.The position of the storage chamber in porous wick micro-channel evaporator has an important influence on heat transfer characteristics or flow resistance,and that the storage chamber is at the bottom of the evaporator is better than that at the side of the evaporator.The effect of entrance location in the evaporator is not obvious.These optimization results provide reference data for improving the performance of the porous wick micro-channel evaporator.