儲熱系統之熱流特性研究; Study on the flow and thermal characteristics of heat storage system

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Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/43501

Title:	儲熱系統之熱流特性研究;Study on the flow and thermal characteristics of heat storage system
Authors:	高慈妤;Tzu-Yu Kao
Contributors:	機械工程研究所
Keywords:	儲熱系統;相變化材料;enthalpy-porosity;無因次熔化時間;enthalpy-porosity method;phase change material;heat storage system
Date:	2010-07-14
Issue Date:	2010-12-08 13:42:51 (UTC+8)
Publisher:	國立中央大學
Abstract:	本文主旨為利用數值方法探討圓柱內相變化材料的總熔化時間、熔化情形與熱流現象。數值模擬所考慮的相關參數及其範圍：貝克勒數Pe=1.6×10^2~6.4×10^3 、史蒂芬數Ste=0.001~1、縱橫比=2~8 、熱傳導係數比值k=0.001~500；最後探討不同工作流體與相變化材料對系統內熱流現象的影響。結果發現高貝克勒數、高史蒂芬數、高熱傳導係數的情況下，液體流動現象明顯，相變化材料的平均溫度較高、熔化速度較快，因而整體熔化時間較少。而幾何參數的縱橫比則是數值越大，熔化完的流體受重力影響的自然對流現象明顯，而使流動速度增大。另外，工作流體與相變化材料的關係中，中溫與高溫的工作流體，若以總熔化時間與儲熱量兩方考量下，KF為最佳使用的材料。最後可以推導出總無因次熔化時間與貝克勒數Pe、史蒂芬數Ste、縱橫比、熱傳導係數比值k的關係式。 This study investigates the thermal and flow characteristics of an energy storage system using phase-change materials (PCM). The governing dimensionless equations of the problem and boundary conditions are formulated and solved numerically by using the enthalpy-porosity method with the control volume approach. The melting process, the total melting time, and the effects of several parameters are discussed. The dimensionless parameters considered include the Peclet number, the Stefan number, the aspect ratio, and the thermal conductivity ratio of the PCM to the heat transfer fluid. Results show that, for cases of high Peclet number, high Stefan number or high thermal conductivity ratio, the melting time is reduced due to the enhancement of heat transfer and the circulation of the PCM. For intermediate and high temperature PCM energy storage systems, KF is the best material to use. Correlations between the dimensionless total melting time of the PCM and the Peclet number, Stefan number, aspect ratio and the thermal conductivity ratio are also derived for different conditions.
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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