Study on flow and heat transfer performance of single jet impingement cooling through variable-diameter hole

Abstract

In this work, the heat transfer and flow characteristics of single jet impinging cooling with three types of hole configurations, namely converging hole, straight hole, and expanded hole, were compared and analyzed numerically. The influence laws of Reynolds number, outlet-to-inlet diameter ratio, and impinging height ratio on the heat transfer, flow, and comprehensive thermal performance of the converging-hole impinging cooling were intensively investigated. Finally, the empirical correlations were fitted and the sensitivity of performance variables to influencing parameters were analyzed for the converging-hole impinging cooling. The results show that the converging hole exhibits the superlative heat transfer performance but the poorest flow performance. The expanded hole exhibits the poorest heat transfer performance but the superlative flow performance. As Re>24,000, the comprehensive thermal performance of the three types of hole configurations is similar. For the converging-hole impinging cooling, when Re increases from 6,000 to 30,000 under various structural parameters, the average Nusselt number increases by approximately 1.62 to 2.65 times, and the comprehensive thermal coefficient increases by approximately 1.58 to 2.45 times. As the outlet-to-inlet diameter ratio increases from 0.5 to 0.9 under various Re, the pressure loss coefficient of the converging-hole impinging cooling decreases by approximately 91.47% to 92.95%, and the corresponding average Nusselt number decreases by 43.61% to 60.07%. When the impinging height ratio is 2.0, the converging-hole impinging cooling exhibits lower pressure loss coefficients. The parameter sensitivity analysis shows that the average Nusselt number of converging-hole impinging cooling is sensitive to changes in the outlet-to-inlet diameter ratio and Reynolds number, but insensitive to changes in the impinging height ratio. The pressure loss coefficient is highly sensitive to changes in the outlet-to-inlet diameter ratio, but insensitive to changes in the Reynolds number and impinging height ratio. The comprehensive thermal coefficient is highly sensitive to changes in the Reynolds number, but insensitive to changes in the outlet-to-inlet diameter ratio and impinging height ratio.