板式熱交換器之熱流模擬與熵增分析; The numerical simulation of thermofluids and entropy generation in plate heat exchangers

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題名:	板式熱交換器之熱流模擬與熵增分析;The numerical simulation of thermofluids and entropy generation in plate heat exchangers
作者:	李國楨;Guo-jen Li
貢獻者:	機械工程研究所
關鍵詞:	數值模擬;板式熱交換器;山形紋板片;壓降;熱傳;紊流;熵增加;Heat transfer;Pressure drop;Chevron plate;Plate heat exchangers;Numerical simulation;Turbulent flow;Entropy generation
日期:	2010-07-16
上傳時間:	2010-12-08 13:43:24 (UTC+8)
出版者:	國立中央大學
摘要:	本研究建立三維全尺寸的K070山型紋板式熱交換器模型，以數值模擬分析板式熱交換器的流場、壓降及熱傳特性，並以熱力學第二定律的熵增定理分析板式熱交換器的系統，找出最佳操作雷諾數。本研究的模型共有三個流道，工作流體為水，考慮的流道雷諾數介於300-12000之間，以ANSYS FLUENT套裝軟體進行層流和紊流分析，並與經驗關係式及解析解作驗證。本研究預測的摩擦因子與其他研究學者提出的關係式接近，紊流部份誤差小於5%，層流部份平均誤差約11%。熱傳方面，由模擬結果得到冷水側及熱水側的熱傳關係式，預測值落於其他研究提出的關係式範圍之內，最大誤差小於36%。熵增加的分析結果顯示，K070型板式熱交換器的流道雷諾數為3900時，總熵增加最低，系統效率可達到理論的最大值。本研究成功建立出多流道考慮共軛熱傳的板式熱交換器模型，且預測結果具有一定準確度，能在板式熱交換器的研發初期快速驗證設計理念，提供研究人員設計與改良的依據。 In this study, a three dimensional calculation with real-size geometry of K070 chevron plate heat exchanger which consisted of thee flow channels have been conducted. The characteristics of flow, pressure drop and heat transfer in plate heat exchangers are investigated numerically. Also, the analyses of second law of thermodynamics (i.e. entropy generation) are presented. The numerical simulations are carried out using ANSYS FLUENT with water as working fluid in the Reynolds number (Re) range from 300-12000, which cover laminar and turbulent regime, and numerical results were validated with empirical and analytical correlations. The numerical friction factors are found in good agreement within 5% for turbulent flow and average error of 11% for laminar flow with empirical correlations. Nusselt number (Nu) correlations of cold and hot water side which obtained by numerical results have been proposed. Values of numerical Nu correlations agree within empirical and analytical correlations. Deviations of computed Nu with empirical and analytical correlations are up to 36%. The analyses of entropy generation indicate that the optimal Re of K070 plate heat exchangers is 3900. A model of three channels chevron plate heat exchanger considered conjugate heat transfer has been established. It can be useful to verify the design concepts in the early research and development.
顯示於類別:	[機械工程研究所] 博碩士論文

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