Flow And Heat Transfer Characteristics Of Small-Aperture Circular Water Jet Cooling Conical Heat Sink

The heat flux of electronic devices continues to rise,due to its high integration,miniaturization and high energy consumption.The number of"thermally-failed"electronic products continues to increase,and cooling problems have become a major constraint to its development.As an efficient heat transfer technology,jet impingement is one of the most promising tools for removing high heat flux heat.In view of few studies on the jet impact cone heat sink,this paper uses the numerical simulation method to study the flow and heat transfer characteristics of the small-aperture circular nozzle jet impact cone heat sink.The main work is:Firstly,the simulation reliability of different turbulence models for the jet cooling cone heat sink is verified based on the experimental data.The Transition SST model has the highest reliability.The effect of the length of the nozzle on the exit velocity of the nozzle was investigated.The outlet flow of 50 times the length of the tube was fully developed and the length was defined as the length of the nozzle.Secondly,the basic flow and heat transfer characteristics of a small-aperture circular jet impact cone heat sink are systematically studied.According to the flow characteristics,the surface area is divided into stagnation region,conical surface jet region,conical edge region and wall jet region.The flow and heat transfer characteristics of different regions were analyzed.Heat transfer capacity of the stagnation region was significantly improved compared with the flat heat sink.In the conical edge region,flow separation and secondary jet appeared,resulting in heat transfer weakened firstly and after the enhancement.The heat transfer capacity of the cone heat sink is better than that of the flat heat sink in most cases.When 0<r/D_n<3,the cone heat sink has the best heat transfer capacity,which is up to 15%higher than the flat heat sink.Then,the Reynolds number(Re=5000-50,000),conical bottom angle(?=0?-70?),conical bottom fillet(R_u=0-2.0 mm)and conical top fillet(R_t=0.02-4.0 mm)were investigated.Increasing the Reynolds number can effectively reduce the heat sink temperature and improve the heat sink temperature uniformity.When Re=50,000,the temperature difference of the heat sink is reduced by 16.6 K.The heat transfer performance of the small angle cone heat sink is better.By reducing the angle between the bottoms of the cones,the secondary jet is weakened and the size of the horseshoe vortex is reduced.Increasing the top fillet weakens the heat transfer advantage of the stagnation zone.By changing the bottom fillet,the scale of the horseshoe vortex can be controlled.When the bottom chamfer R_u=4 mm,the horseshoe vortex disappears.Finally,according to the influence of structural parameters on the single jet,the cone size for multi-jet is designed:the bottom angle is 40?,the top fillet is R_t=0.5 mm and the bottom fillet is R_u=0.4 mm.Increasing the number of nozzle,the high temperature region shrinks toward the edge,and the overall temperature of the heat sink decreases.At Re=20,000 and 30,000,the j factor is small.When Re=5000,the j factor value is the largest.According to the variation of Nusselt number ratio and j factor,the heat transfer performance of heat sink is best when the small Reynolds number and multi-jet match.