受限不同擋板外形之衝擊噴流於平板表面熱傳之數值模擬

Numerical simulation for heat transfer from a plane surface due to different baffle shapes under impinging jet

徐美琪(MEI-CHI HSU)

指導教授 ： 翁輝竹

中原大學/工學院/機械工程學系/碩士(2022年)

https://doi.org/10.6840/cycu202201589

摘要

本論文完成受限不同擋板外形之衝擊噴流於平板表面熱傳之數值模擬研究，主要探討不同外形之擋板放置於噴嘴出口不同位置對衝擊板上努賽爾數的影響，考量變因為擋板形狀、擋板擺放位置以及在高雷諾數與低雷諾數下流體運動情形對衝擊板散熱性的影響。在一開始，本研究先進行文獻數值驗證以及網格獨立性測試，挑選出符合時間成本及數值精準度的網格單元數以便後續研究，透過Ansys內建的 Workbench Fluent 軟體增設擋板於噴嘴出口處，最後求解其流體衝擊於固定熱通量之衝擊板上的熱傳分析。
　　結果發現，增加擋板能夠大幅提升局部的努賽爾數，並且擋板位置遠離噴嘴出口，其努賽爾數最大峰值位置也會向噴流中心靠近，但是努賽爾數也會稍微降低。在平均努賽爾數方面，有增加擋板的衝擊噴流都有較佳散熱效果，而其中又以三角形擋板於高雷諾數，距離噴嘴出口位置 1 mm 條件下有最佳散熱效果，最大努賽爾數峰值可提升 75%，整體平均努賽爾數則增加 12%。矩形擋板雖沒有其餘擋板熱傳表現幅度明顯，但其在噴流中心軸造成的低壓區改善了最小努賽爾數的現象。在增加擋板情況下，雖然總體的平均努賽爾數增加幅度並不顯著，但是在局部散熱方面有位置的可控性並且可以大幅提升其努賽爾數最大峰值。

關鍵字

衝擊噴流 ； 對流熱傳 ； 擋板外形 ； 擋板位置

並列摘要

This study is conducted with numerical simulation for heat transfer from a plane
surface due to different baffle shapes under impinging jet. It mainly discusses the influence of different baffle shapes on the Nusselt number of the impinging plate when the baffles with different shapes are placed at different positions of the nozzle outlet. Consider the influence of the shape of the baffle, the placement of the baffle, and the fluid motion on the heat dissipation of the impingement plate at high and low Reynolds numbers.
It was found that increasing the baffle plate can greatly increase the local Nusselt number, and the baffle plate is far away from the nozzle outlet, and the
maximum peak position of the Nusselt number is also closer to the center of the jet, but the Nusselt number is also slightly reduced. In terms of the average Nusselt number, the impingement jet with the increase of the baffle has better heat dissipation effect, and the triangular baffle has the best heat dissipation effect under the condition of high Reynolds number and 1 mm from the nozzle outlet position. The peak Nusselt number can be increased by 75%, and the overall average Nusselt number can be increased by 12%. Although the heat　transfer performance of the square baffle is not as obvious as that of the other baffles, the low pressure area caused by the central axis of the jet improves the phenomenon of the minimum Nusselt number. In the case of adding baffles, although the overall average Nusselt number does not increase significantly, it has directional controllability in terms of local heat dissipation and can greatly increase its maximum peak Nusselt number.

並列關鍵字

Impinging jet ； Convective heat transfer ； Shape of baffle ； Position of baffle

參考文獻

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