Study On Flow And Heat Transfer Characterizations Of Micro-jet In A New Structure Cooler

Main objective of this study was to design a more efficient cooling scheme for electronic components.A new structure micro-jet cooler with return channels was designed on the basis of traditional air-cooling technology.In the present study,the flow and heat transfer characterizations of microjet cooler were investigated by experimental and numerical methods respectively,and the performance parameters of the cooler were obtained.Multiple-micro-jet was simulated,and the results showed that cross-flow has a complex influence on the micro-jet cooling.Then,a new-type micro-jet cooler with return channels was designed.It was found that compared to the micro-jet cooling without return channels,the crossflow interference would be reduced or even eliminated and the cooling performance ofthe cooler was improved.The experimental and numerical results at different operation parameters and different structure parameters were obtained by controlling single-valued variables.The jet Reynolds number ranged from 5000 to 6800,and the fluid form of micro-jet movement will be disturbed by surrounding fluid for a lower jet Reynolds number.When jet Reynolds number was higher,the influence of Reynolds number could be ignored,and the temperature difference on the cooling surface was lower.The input heat flux only affected the temperature distribution of cooling surface.The investigations were also conducted at dimensionless jet-to-plate spacing ratio(H/d)from 1 to 14.The impinging jet was weak with H/d increased.For H/d in the range of 1-6,the temperature difference on the cooling surface is lower and the performance of cooler is perfect;for H/d in the range of 8-14,micro-jet motion trajectory would deviated,and temperature difference on the cooling surface,is higher,those phenomena were more significant with the increase of H/d.The dimensionless jet-to-plate spacing ratio(S/d)from 3 to 5,the influence of S/d could be neglected,and the temperature distribution of cooling surface was uniform.The average Nusselt numbers by the empirical equation was correlated.The error between calculated results by experimental empirical equation and experimental results was no more than 9.21%,and the error between calculated results by empirical equation and numerical results is only 2.96%.For jet Reynolds number ranged from 5000 to 6800,the pressure loss in the range of 9-130kPa,the energy efficiency coefficient in the range of 0.06-0.95,and the thermal resistance in the range of 0.4K-2.0K/W.The results showed that,cooling effect of cooler was the best when H/d was 4;optimal performance of cooler was obtained by using Matlab for multi-objective optimization when jet Reynolds number was 6095.Under those conditions,the thermal resistance was 0.6693 K/W,the energy efficiency coefficient was 0.23,and the average temperature of coo ling surface was 41 ℃.In briefy,the return channels can solve the problem of cross-flow disturbance.For the inlet temperature is 21℃,jet Reynolds number in the range of 5000-6800,the maximum heat transfer coefficient is 2858W/(m2·K).The micro-jet has strong heat transfer ability,and micro-jet cooler has a good prospect for the cooling of electronic components.