Experimental And Numerical Study On Flow And Heat Transfer Characteristics Of HFE7100 In Low Pressure Gradient Distribution Pin Fin Microchannel With Narrow Channel

With the electronic devices developing towards miniaturization and integration,high-power electronic chips are facing with severe thermal managements due to the high temperature produced during their operation.Presently,the chip background heat flux density has reached 100 W/cm~2,while the heat flux of local hotspots reaches up to1000 W/cm~2.The traditional air cooling technology is difficult to deal with such high heat flux.The microchannel cooling technology with liquid phase flow is the most promising chip thermal management method.The results show that the pin fin microchannel has high heat transfer efficiency,but most researches only focus on its heat transfer performance,and the pressure drop loss of the microchannel system has an important influence on its wide application.In this thesis,the low-pressure loss gradient pin fin distribution microchannels with narrow channels are proposed:Step-down pin fin gradient distribution microchannels(MPFC-BP)and three improved gradient distribution pin fin microchannels(MPFC-BP48,MPFC-BP2244,MPFC-BP264),by setting narrow channel in pin fin microchannel,better heat transfer performance is achieved and the pressure drop is reduced.The flow and heat transfer characteristics of dielectric coolant HFE7100 in different microchannels are also investigated experimentally and numerically,the heat transfer characteristics of different hotspots,Reynolds number,hotspot area and heat flux are studied in detail by numerical simulation.The main results are as follows::The experimental results show that the pressure drop loss in the gradient distribution pin fin microchannel can be effectively reduced by setting narrow channels,but the heat transfer capability will be reduced.The pressure drop loss of MPFC-BP is56.3%and 52.7%lower than that of the gradient distribution pin fin and uniform pin fin microchannels respectively when the volume flow rate is 120 ml/min.However,the uneven flow distribution in the microchannel can be effectively improved by setting pin fin groups in the narrow channel.The flow rate in the narrow channel is periodically interrupted and re-increased,and the heat transfer capacity is significantly enhanced when Reynolds number is 563,local Nu increased by 17.2%to 22.1%.MPFC-BP48,MPFC-BP2244 and MPFC-BP264 can handle 109 W/cm~2,120 W/cm~2 and 114 W/cm~2,respectively.Compared with MPFC-BP,the heat transfer limit is increased by 32.9%,46%and 39%,respectively,the pump power consumed is only 63 m W,67 m W and 68 m W,and the MPFC-BP2244 has the best heat transfer effect.It is found that the ability of hotspot thermal management of three improved type pin fin microchannels is significantly enhanced.The effect of hotspots in upstream(Hotspot 1,x=2 mm)or middle and downstream(Hotspot 2,x=6 mm)of the chip surface on the temperature distribution of three improved type pin fin microchannels is similar.The highest temperature at Hotspot 1 is always lower than that at Hotspot 2when the same hotspots exist in the upstream and the middle and lower reaches of the microchannel heating surface.The maximum temperature of Hotspot 2 on MPFC-BP is360.1 K,and the maximum temperature of MPFC-BP48,MPFC-BP2244 and MPFC-BP264 are 346.4 K,343.9 K and 343.6 K respectively when the hotspot heat flux is 500 W/cm~2 and the hotspot area is 0.49 mm~2.When the hotspot area is 0.25 mm~2and only the chip temperature is taken into account,the maximum temperature of MPFC-BP reaches 360 K when the hotspot heat flux is 800 W/cm~2.The maximum wall temperatures of MPFC-BP48,MPFC-BP2244 and MPFC-BP264 were 354.0 K,352.0K and 351.4 K respectively when the hotspot heat flux was 1000 W/cm~2.It is found that,regardless of the presence of non-uniform hotspots,the MPFC-BP2244 microchannel is divided into five zones by the uniform distribution of pin ribs in the narrow channel.The local heat transfer capacity is enhanced and the overall heat transfer performance of the microchannel is significantly improved,has the optimal heat transfer effect.In this thesis,the flow and heat transfer characteristics of low pressure loss cascade pin fin microchannels with narrow channels are studied by experimental and numerical methods,and the low pressure loss and high heat transfer performance are obtained,it provides a new idea and theoretical basis for the heat management of electronic chips with high heat flux density by using high performance microchannel radiator.