考慮熱輻射效應之非絕熱和絕熱各種形狀的管或容器的可靠一維熱傳特性之計算用程式研發

The development of a programming to calculate the reliable one-dimensional heat transfer characteristics of non-insulated and insulated ducts or containers with various shapes considering the heat radiation effec

蕭朝全(Chao-Chuan Siao)

指導教授 ： 黃景良

共同指導教授 ： 陳文立

崑山科技大學/工程學院/機械工程研究所/碩士(2009年)

https://doi.org/10.6828/KSU.2009.00016

摘要

非絕熱和絕熱之管和容器常應用於工業和建築物中。由於熱輻射方程式包含了溫度四次方的計算，造成在數學上的分析非常複雜。所以大部分的專家和學者認為，基於以往的經驗，絕熱表面與外界環境之間的溫差不大，熱輻射因素便可被忽略以簡化分析。然而，本文發現，對於非絕熱和很薄隔熱材的絕熱管或容器，若忽略熱輻射效應，在低的空氣對流熱傳係數和高的表面放射率的條件下，將產生非常大的誤差。尤其是當外流體溫度與環境溫度不等時其誤更大。故本文將熱輻射效應納入考量，求解出非絕熱和絕熱之圓形管、橢圓形管、矩形管、正多邊形管、圓球體、橢圓球體和矩形立方體之可靠一維熱阻計算模型。應用該可靠一維熱傳計算模型所得結果與使用CFD所得較正確解比較，其誤差與隔熱材之厚度相關，大多在0.1%~3%之間。同時，故本文將該可靠一維熱傳計算模型，完成相對應之非絕熱和絕熱之圓形管、橢圓形管、矩形管、正多邊形管、圓球體、橢圓球體和矩形立方體之熱傳可靠近似解之計算程式，以供相關工程快速熱傳分析之用。

關鍵字

絕熱 ； 熱輻射 ； 放射率 ； 圓形管 ； 橢圓形管 ； 矩形管 ； 正多邊形管 ； 圓球體 ； 橢圓球體 ； 矩形立方體

並列摘要

The non-insulated and insulated ducts and containers are commonly applied in the industries and various buildings. Because the heat radiation equation contains the 4th order exponential of temperature which is very complicate in calculations. Most heat transfer experts recognized from their own experiences that the heat radiation effect can be ignored due to the small temperature difference between insulated surface and surroundings. On the contrary, it is found in this paper that neglecting the heat radiation effect is likely to produce large errors of non-insulated and thin-insulated ducts or containers in situations of ambient air with low external convection heat coefficients and larger surface emissivity, especially while the ambient air temperature is different from that of surroundings and greater internal fluid convection coefficients. While considering heat radiation effect, the reliable one-dimensional thermal resistance models of the relative non-insulated and insulated circular, oval, rectangular, regular pologonal duct or non-insulated and insulated spherical, oblique spherical and rectangular container are found by comparing with the accurater CFD results. Most the errors are within 0.1~3% relative to the insulated thinckness. Meanwhile, we apply these reliable one-dimensional thermal resistance models to develop programmings for non-insulated and insulated circular, oval, rectangular, regular pologonal duct or non-insulated and insulated spherical, oblique spherical and rectangular container considering heat radiation. The engineer can easily apply these programming to complete their heat transfer analysis quickly.

並列關鍵字

insulation ； heat radiation ； emisivity ； circular duct ； oval duct ； rectangular duct ； regular pologonal duct ； spherical container ； oblique spherical container ； rectangular container

參考文獻

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