板式熱交換器之流場模擬與流動分佈不均勻態分析; Numerical analysis of flow and flow maldistribution in plate heat exchangers

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Title:	板式熱交換器之流場模擬與流動分佈不均勻態分析;Numerical analysis of flow and flow maldistribution in plate heat exchangers
Authors:	曾廣彬;Guang-bin Tzeng
Contributors:	機械工程研究所
Keywords:	流動分布不均勻;壓降;山型紋板片;板式熱交換器;計算流體力學;Computational fluid dynamics;Plate heat exchanger;Chevron plate;Flow maldistribution;Pressure drop
Date:	2010-07-18
Issue Date:	2010-12-08 13:43:27 (UTC+8)
Publisher:	國立中央大學
Abstract:	大多數板式交換器的實驗研究僅量測板式熱交換器之性能，並無觀測板式熱交換器內部流場，故本文以FLUENT套裝軟體針對K050、K070及K200山型紋板片進行三維數值模擬分析，首先針對K070板片以不同紊流模型進行模擬分析，結果顯示Realizable k-ε模式最準確；模擬的摩擦因子與實驗最大誤差僅8%，具有相當高地準確性；並測試定溫、定熱通量及對流邊界條件之差異，得知採用對流邊界條件最接近實際流場。本文之數值模擬經驗證對於板式熱交換器熱流場具有一定精確度，接著探討K050、K070及K200流場及流動分布不均勻之現象；由模擬結果顯示K050及K070板片在低雷諾數(302)時流場大多為十字交叉流，當雷諾數提高為4075時則可發現部份流場轉變為曲折流；K200板片在大範圍的雷諾數（從302至4187）皆維持十字交叉流。各板片中以K200板片分布不均勻現象最明顯，若能針對入出口區波紋的配置做改良，則可降低接近入出口區不均勻流動之現象。本文之模擬結果可作為熱交換器之設計人員設計與改良板式熱交換器的依據。 In the present study, the thermal convection characteristics and pressure drop in a corrugated chevron plate of real-size plate heat exchangers have been investigated. A commercial CFD code FLUENT is employed to simulate the water through the channel. The consequence of comparison the different turbulent model with empirical correlations for friction factor shows that Realizable k-ε model has better accuracy, the maximum error is only 8%. This study also test the performance of three thermal boundary conditions (constant wall temperature, heat flux and convection type conditions), and find the convection boundary condition is the most realistic for a plate heat exchanger. Through a series of verification, the accuracy of numerical model in this work has been established. The numerical result shows the flow and temperature pattern and flow maldistribution. The flow patterns are cross flow for the plates of K070 and K050 when Reynolds number is 302. When Reynolds number increases upto 4075, the zig-zag flow could be found for the cases of K070 and K050. On the other hand, The flow pattern is kept as cross flow type for K200 plate for whole range of Reynolds number (from 302 upto 4178). The K200 case has the most severe maldistribution among theee plates. Based on numerical study, adjust the layout of corrugation can reduce the level of flow maldistribution. The simulation results can provide a valuable design guide on improving the performance the plate heat exchanger.
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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