Design and heat transfer performance of impinging jet arrays for physical tempering of ultra-thin glass
To meet the high-efficiency and uniform heat transfer requirements in the gas-suspended ultra-thin glass physical tempering heating furnace,a parametric design study on impinging jet arrays with return holes was conducted,particularly focusing on low jet heights.A three-dimensional numerical heat transfer model of high-temperature array jet impingement heat transfer was established,and the thermophysical properties of high-temperature gas were analyzed.Numerical simulations were conducted to investigate the effects of different design parameters on the transient heat transfer of impinging jets.Reynolds numbers(Re)ranging from 2000 to 10 000 were set.Under a certain mass flow rate,variations in the dimensionless reflux hole diameter(D1/D)from 1 to 3 and the dimensionless jet spacing(S/D)of 4,5,and 7 were considered.Surface-averaged Nusselt number and temperature variation coefficient were used to illustrate the performance in terms of average heat transfer and uniformity.The results indicated that in the impinging jet array model with return holes at low jet heights,as Re varies from 2000 to 10 000,the surface average Nusselt number increased by 243.3％,and heat transfer uniformity improved by 90.9％.The diameter of the return holes had a significant effect on heat transfer.The ratio of the diameter of the return hole to the diameter of the jet hole(D1/D)increased from 1 to 3,and the average Nusselt number first increased and then decreased.When D1/D=2,the average heat transfer effect showed a turning point,and the average Nusselt number was always higher than that of the corresponding traditional array jet.A smaller return holes diameter led to a gradual reduction in the maximum velocity difference between the return holes and the jet holes,thus demonstrating excellent heat transfer uniformity.Additionally,reducing the ratio of jet holes spacing to diameter(S/D)improved heat transfer uniformity.At S/D=4 and D1/D=1,the heat transfer uniformity was maximally improved by 46.24％compared to the corresponding traditional array jet impingement.These research findings provide a theoretical foundation for the design and application of efficient impinging jet structures.
ultra-thin glassimpinging jetreturn holesaverage heat transferheat transfer uniformity
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