Numerical Investigation on Flow and Heat Transfer Characteristics of Jet Impinging Cooling through Variable-diameter Hole
A numerical investigation was conducted to study the flow and heat transfer performance of impinging jet cooling using variable-sized holes.Three different hole configurations,namely contraction hole,straight hole,and expansion hole,were designed for the impinging jet cooling system.The flow and heat transfer characteristics of the three hole configurations under different Reynolds numbers were compared.The effects of Reynolds number and hole configuration on the flow performance,heat transfer performance,and overall thermal performance of the impinging jet cooling were analyzed.Empirical correlations for the average Nusselt number,friction coefficient,and overall heat transfer coefficient of the different hole configurations were obtained as functions of the Reynolds number.The results showed that compared to the straight hole configuration,the friction coefficient of the contraction hole configuration increased by approximately16.67 to 21.09 times,and the average Nusselt number on the target surface increased by approximately 0.96 to 1.85 times for Reynolds numbers ranging from 6,000 to 30,000.On the other hand,the friction coefficient of the expansion hole configuration decreased by approximately 22.55%to 33.68%,and the average Nusselt number on the target surface decreased by approximately 5.62%to 10.85%.Among the three hole configurations,the contraction hole configuration exhibited the best heat transfer performance but the poorest flow performance.The straight hole configuration showed moderate heat transfer and flow performance,while the expansion hole configuration exhibited the lowest heat transfer performance but the best flow performance.When the Reynolds number was less than 24,000,the expansion hole configuration had the best overall thermal performance,followed by the straight hole configuration,while the contraction hole configuration had the worst overall thermal performance.When the Reynolds number was greater than or equal to 24,000,the overall thermal performance of the three hole configurations was close to each other.The findings of this study can provide valuable insights for the design of future advanced gas turbine internal cooling systems using variable-sized holes.
impingement coolingsingle jetvariable diameter holeflow performanceheat transfer performance
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