Numerical Simulation Of Heat Sink With Combined Micro Channels And Jet Arrays For High Heat Flux Density

Cooling of high heat flux density has become a bottleneck that impedes the development of techniques in many fields. The heat flux density is beyond the ability of conventional cooling methods as the advances in the miniaturization of electronic devices, the increase of laser power and the speed of supersonic craft. This thesis investigates the cooling method of high heat flux density.Based on the excellent heat transfer characteristics of mini/micro-channel and impinging jet, the cooling effect of heat sink with combined micro-channels and jet arrays (MCJA) is investigated by FLUENT firstly. The results show such combination can greatly improve the temperature uniformity of the heated surface. Under the fixed pump power, heat flux density, and the total width of fin and channel, there exist optimum depth of channel and optimum width of the side wall that make the heated surface temperature minimum. The correlation of heat transfer is obtained for MCJA based on the numerical results.The cooling effect of the heat sink with combined pillar fins and jet arrays (PFJA) is numerically investigated. The pillar fins are expected to destroy and disturb the velocity boundary layer and to enhance heat transfer. Four kinds of arrangements are considered. The simulations show that two of them have better heat transfer performance and their structure sizes are further optimized for fixed pump power and heat flux. Optimum depth of channel and width of fins are still existed with constant total width of pillar and channel. Correlation of heat transfer is also fitted for these two structures. The cooling effect of MCJA and PFJA is compared according to the thermal resistance defined by the entransy dissipation. The results show that MCJA is superior to PFJA for small width of pillar fins but is inferior for larger width of pillar fins when the total width of pillar and channel is fixed and the pillar width is the same, and the critical width of pillar fins is increased with the pump power. The PFJA structure has the lowest thermal resistance if only the total width of pillar and channel is fixed.The mini/micro-channel is applied to the cooling scramjet strut. Four structures of heat sink are studied. The effects of the width of channel and wall, the thickness from channel to the strut outer surface on the surface heat flux density, the temperatures of the cooling liquid and strut are investigated. The simulations show that the structure with the cooling liquid entering at the strut end and passing along the strut surface has best performance among the four structures for fixed pump power.The researches of this thesis demonstrate that mini/micro-channel heat sink has excellent cooling capacity, and its combination with jet arrays can significantly improve the uniformity of surface temperature. Such a combination structure has great potential in removing high heat flux density.