The Investigation Of Dimple's Structural Optimization In Microchannel For Heat Transfer Enhancement

With people's continuous pursuit of high-performance electronic products,the heat generation rate of electronic products in unit volume is increasing,resulting in the problem of thermal barrier,which cannot be ignored,and it is an inevitable trend to explore more effective ways of heat dissipation.The dimple in microchannel strengthens heat transfer with producing small resistance,and it is also easy to be manufactured.Therefore,it is becoming more and more popular with researchers and scholars.In this thesis,numerical simulation and multi-island genetic algorithm are combined to optimize the shape of the dimples in microchannel in the range of global parameter under laminar flow condition.The dimple with the traditional spherical shape is simulated for contrast.It is found that the separation of fluid in the front of edge go against heat transfer.The number and size of vortex generated,the impact of the fluid on the leeward side and fluid's reattachment are the key factors affecting the heat transfer.Dimple in microchannel with different Reynolds number Re and different diameter is optimized by using multi-island genetic algorithm,the deepest point of the optimized dimple shift to downstream along the center line of the flow,and the depth of depression is increased.With the increase of Reynolds number Re,the ratio of the resistance coefficient of the optimized dimple to that of the smooth channel f/f₀,Nusselt number ratio Nu/Nu₀ and the value of comprehensive performance parameter PEC increase.With the increase of the dimple diameter,the values of f/f₀,Nu/Nu₀ and PEC increase.As the period length L of the heat transfer unit decrease,the heat transfer is enhanced and the resistance is increased,and the comprehensive performance of the microchannel heat exchanger is better.Therefore,the cycle length L of heat transfer units should be minimized under the condition of processing conditions.The dimple in microchannel has good flow and heat transfer performance,and its application prospect is good,and it is of great significance to optimize the shape of the dimples in microchannel.