利用最小平方有限元素法探討三維熱交換器中散熱圓管同軸及交錯排列對熱流場之影響

Application of least-squares finite element method on the study of flow and heat transfer in a 3-D heat exchangers with in-lined and staggered tubes

盧柏伸(Po-Shen Lu)

指導教授 ： 鄧志浩

中原大學/工學院/土木工程研究所/碩士(2006年)

https://doi.org/10.6840/cycu200600025

摘要

中文摘要
本文主要模擬三維熱交換器中散熱圓管同軸或交錯排列之熱流場影響，其數值方法是利用最小平方有限元素法（LSFEM）進行數值分析。本研究針對同軸和交錯兩種散熱圓管〈4排〉不同的排列方式進行模擬，在固定鳍片間距為〈8 fins/in〉下，模擬過程中假設流體為穩態流場、不可壓縮流體，並且在層流的狀態下〈Re=200至600〉通過熱交換器。觀察兩種不同管排列方式對壓降、壓力係數、熱傳係數、局部紐賽數的影響。
由數值模擬結果證明，在平均熱傳係數上，散熱圓管以交錯排列的方式下，交錯排列的平均熱傳係數比同軸排列高10-30%，此外，在不同雷諾數下，與高雷諾數相比，低雷諾數的影響較大。在壓降方面，散熱圓管以交錯排列的方式下，交錯排列比同軸排列有較高的壓降；在散熱圓管表面同軸排列和交錯排列的壓力係數的變化，在90度左右有所差異，且此區域，交錯排列比同軸排列第二根至第四根散熱圓管表面的局部紐賽數高25%-50%。整體上，數值結果與實驗測量相符。

關鍵字

最小平方有限元素法 ； 熱傳 ； 平板鳍片 ； 熱交換器

並列摘要

ABSTRACT
A numerical calculation procedure based on the least-squares finite element method (LSFEM) is employed to study the fluid flow and heat transfer in a 3-D heat exchangers with in-lined and staggered multiple–row (4 rows) tubes.
In this study, the fin pitch of the heat exchanger is 8 fins per inch and the fluid flow is assumed steady, incompressible, and laminar with Reynolds number ranging from 200 to 600.
In this paper the pressure drop, pressure coefficient, heat transfer coefficient, local Nusselt number and average Nusselt number for different geometric arrangements have been examined in detail.
The numerical results demonstrate that the average heat transfer coefficient of staggered arrangement is 10%-30% higher than that of the in-line one; also, it is effected more at low Reynolds number than at the high Reynolds number. The distribution of pressure drop of staggered array is higher than that of in-lined array. The variation of pressure coefficient at tube surface is dramatically for both the staggered and in-line arrangements for the angle less than 90 degree. The local Nusselt number of staggered array is higher 25%-50% than that of in-lined array for the tube row 2 to 4. Overall, the numerical results are in good agreement with the experimental measurement.

並列關鍵字

plate-fin and tube heat exchangers ； Least-squares finite element method ； heat transfer ； Heat exchanger

參考文獻

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