對固體表面加熱之液晶熱像熱傳實驗方法

An Experimental Heat-Transfer Method Using Liquid Crystal Thermography with Surface Heating

吳佩學(Pey-Shey Wu) ； 劉家榮(Chia-Jung Liu) ； 賴祐民(Yow-Min Lai)

《科學與工程技術期刊》 3卷2期 (2007/06) Pp. 37-46

https://doi.org/10.7117/JSET.200706.0037

摘要

本研究基於對固體表面加熱之液晶熱像法的基本理論，建立了一套熱傳實驗系統與數據約化程序，並採用穩態實驗方法與對固體表面單步級加熱之暫態實驗方法，以具有前端未加熱長度的平板流，以及繞越長圓柱之橫向流進行實驗。結果顯示，利用穩態方法以及對固體表面單步級加熱之暫態方法所得之平板流局部熱傳係數結果與理論值吻合相當良好，充分確認了新建熱傳實驗系統軟硬體之正確性。繞越長圓柱之橫向流，利用新建之熱傳實驗系統進行實驗，所得之局部紐塞爾數結果與文獻上之數據比較，也非常合理。 最後輔以不準度分析之結果，將本研究之對固體表面加熱法與一般常用的對氣體步級加熱之暫態方法之優劣進行比較。

關鍵字

液晶熱像法 ； 穩態方法 ； 暫態方法 ； 步級加熱

並列摘要

An experimental heat-transfer system as well as a data reduction procedure was established in this study on the basis of the fundamental theory of liquid crystal thermography with heating at the solid surface. The system was tested by using both the steady-state and the transient methods with single-step heating at the surface. Two problems considered in the test were the flow over a flat plat with an unheated starting length and a uniformly heated cylinder in the cross flow. Both the steady-state and the transient experimental results of the local heat-transfer coefficients from the flat-plate problem agreed well with the analytical solution, thereby confirming the validity of the new system. The local Nusselt numbers in the cylinder-in-cross-flow problem obtained from the steady-state experiment also compared reasonably well with those in the literature.
An uncertainty analysis was also conducted to compare the present liquid crystal technique with the transient step-heating method in the gas temperature, which is now widely used.

並列關鍵字

liquid crystal thermography ； steady-state method ； transient method ； step heating