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標題: | 迴路熱管動態特性與啟動暫態特性研究 Study of Dynamics Behavior and Start-up Transient Characteristics of Loop Heat Pipes |
作者: | Huan-Hsiang Huang 黃煥翔 |
指導教授: | 黃秉鈞 |
關鍵字: | 迴路熱管,動態行為,暫態行為,系統識別,啟動分析, Loop heat pipes,Loop Heat Pipes,Dynamic Behavior,Transient Behavior,System Identifycation,Startup of Loop Heat Pipe, |
出版年 : | 2009 |
學位: | 博士 |
摘要: | 本研究旨在探討迴路熱管(LHP)的動態行為,推導出迴路熱管的動態模型,並探討迴路熱管的動態行為、設計參數穩定度及啟動暫態特性。從迴路熱管能量平衡方程式可以得到迴路熱管動態模型,從模型中可以得知,迴路熱管是一個隨著操作條件變化的多變量系統,另外將材料物體性質代入模型中,可以將迴路熱管化簡為一個二階的系統,並透過識別實驗來修正動態模型,然後運用此一動態模型來進行溫度控制器的設計,並利用調整冷凝器散熱風扇的風量去控制蒸發器的溫度,其控制誤差為 0.5 oC,符合控制器的設計規格且具有抗干擾能力。在設計參數穩定度分析方面,根據分析結果可得知,增加毛細結構孔隙度及工作流體潛熱會造成迴路熱管不穩定,其餘參數如毛細結構熱傳導係數、液態工作流體熱傳導係數、毛細結構有效熱傳導係數、毛細結構長度及工作流體的沖灌量等皆不影響穩定性。在迴路熱管啟動暫態分析部分,根據分析的結果,迴路熱管的啟動暫態行為可以分成四種模式,分別是:(1)失敗模式;(2)震盪模式;(3)超越量模式;(4)常態模式。因為影響迴路熱管的啟動暫態原因很多,本研究針對工作流體、毛細結構的毛細力、工作流體充填量、迴路長度、熱負載及操作角度等參數,在不同的啟動暫態模式下進行測試,並識別出每個啟動暫態模型,來找出不同參數對啟動暫態特性的影響,其中以蒸發器的毛細力影響最顯著。 The present study is to understand the dynamic behavior of a loop heat pipe (LHP) and deriving the dynamic model of a LHP. In addition, the stability analysis of the designed parameter and the analysis of start-up transient characteristics of a LHP are studied. The dynamic model of a LHP can be derived by the energy balance equation of a LHP. As a result, it is found that the system dynamics of a LHP is a multivariable system changing with operating conditions. The material properties are used in the model, which can be reduced a second-order system. Moreover, the model can be re-vised by the identified experiment. The dynamic model is used to develop a PI con-troller that the temperature of evaporator can be controlled within a deviation of 0.5 degree by changing the mass flow of a fan in the condenser. According to the results of stable analysis, porosity and latent heat of working fluid make unstable for the operation of a LHP except the thermal conductivity of wick, the thermal conductivity of liquid working fluid, the effectively thermal con-ductivity of wick, the length of wick, and charged volumes of working fluid. Final part of the present study has been carried out to test the start-up characte-ristics and behavior of a LHP with the different parameters, which are heat loads, orientation, working fluid, capillary forces, tube length, and charging volume. It is also found that the start-up phenomena of a LHP can be classified into four modes according to the heat loads: (1) failure mode,(2) oscillating mode, (3) overshoot mode, and (4) normal mode. System identification is used to identify those parameters of the start-up characteristics of a LHP and also to determine the relation-ship among those different factors affected the characteristics of a LHP in this study. The results show the major factor is the capillary forces and the secondary factors are working fluid, tube length, and charging volume. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/26104 |
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顯示於系所單位: | 機械工程學系 |
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