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

黃煥翔(Huan-Hsiang Huang)

指導教授 ： 黃秉鈞

國立臺灣大學/工學院/機械工程學研究所/博士(2009年)

https://doi.org/10.6342/NTU.2009.10281

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。

關鍵字

迴路熱管 ； 動態行為 ； 暫態行為 ； 系統識別 ； 啟動分析

並列摘要

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.

並列關鍵字

Loop heat pipes ； Loop Heat Pipes ； Dynamic Behavior ； Transient Behavior ； System Identifycation ； Startup of Loop Heat Pipe

參考文獻

[2] Riehl, R. R. and Dutra, T. Development of an experimental loop heat for application in future space missions. Applied Thermal Engineering. 2005, Vol. 25, pp. Vol. 25, 101-112.

[3] Maidanik, Y. F., et al. Heat Transfer Apparatus. 4515209 U.S., 1985.

[4] Maidanik, Y. F. et al. Design and Investigation of Methods of Regulation of Loop Heat Pipe for Terrestrial and Space Applications. Institute of Thermophysics, Ural Division of the Russian Academy of Sciences, SAE Technical Paper. 1994, p. 941407.

[5] Maidanik, Y. F., Fershtater, Y. G. and Solodovnik, N. N. Loop Heat Pipes: Design, Investigation, Prospects of Use in Aerospace Technics. SAE Paper No.941185. 1994.

[6] Dickey, J. T. and P., Peterson G. Experimental and Analytical Investigation of a Capillary Pumped Loop. Journal of Thermophysics and Heat Transfer. 8, 1994, Vol. 3, 602-607.