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標題: Computer Analysis of Heat Transfer Enhancement due to Ring-Type Ribs in Circular Tubes.
作者: 蔡維屏
關鍵字: computational fluid dynamics
heat transfer enhancement
ring-type protrusion
Nusselt number
friction factor
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摘要: ABSTRACT Heat transfer performance of common shell-and-tube heat exchangers is very dependent on the magnitude of the convection heat transfer coefficient of the tubes using in the heat exchanges. This work used computational fluid dynamics (CFD) simulation approach, adopting the Realizable k-ε model in the ANSYS FLUENT commercial software, to investigate the heat transfer enhancement of circular tubes with internal ring-type protrusions. By comparing the simulated result to experimental data reported in the literature, the validity of the CFD appraoch was verified. In this work, eleven sets of heat tranfer data of circular tubes with different ring-type protrusions were presented. The p/d value of the three tubes is 1.45, while the e/d values were 0.043, 0.069 and 0.1 respectively. Among the three sets of data, two were compared with the experimental data. The result (e/d =0.043) shows the error is 17 %, The result (e/d =0.069) shows the error is 3.6 %; Due to lack of experimental data for comparsion, the accuracy of the other one (e/d =0.1) is uncertain . From the three sets of data, the heat transfer characteristics of the heat tranfer enhancing tubes can be qualitatively observed. That is, for a specific tube, when Nu value increases with the Re value; for different tubes, the e/d value increases, both Nu and f values increases. The result also shows that the width of the protrusions has a minor effect on the Nu value.
摘要 一般管殼式熱交換器的性能主要取決於圓管於執行熱交換時的熱對流係數之大小,因此熱傳增強管之應用對管殼式熱交換器性能之提昇有相當之重要性。本文以計算流體力學(CFD)的方式進行流體與熱傳之模擬,研究中使用ANSYS FLUENT軟體,以Realizable k-ε紊流模式對內部具有突出環節之銅管進行模擬分析,藉由比較文獻實驗中得到的數據,以驗證模擬分析之可靠性。最後共完成11組具有突出環節之銅管之熱傳資料,其中p/d值同為1.45,而e/d值則分別為0.043、0.069與0.1,分析結果顯示其中兩組之平均紐塞數與實驗值分別有17 %與3.6 %的誤差,另一組(e/d=0.1)則因無實驗值可作比較,其數據的準確度尚待確認,但從這三組數據中可以定性化的觀察到,對同一支銅管而言, Re值愈大,Nu值則愈大;對不同之銅管而言,e/d值愈高,其整體的Nu值與f值亦會相對變大。研究結果亦顯示,環節軸向寬度對Nu值之影響不大。
文章公開時間: 2017-08-31
Appears in Collections:機械工程學系所



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