同心球間具放射、吸收與非等向性散射之傳導合輻射熱傳研究

Abstract

本文對兩同心球體之間具有放射、吸收及非等向性散射之介質其 傳導及漫射交互影響下之穩態及暫態熱傳現象做一理論分析。假設兩 球面為灰體、且具有溫射及反射特性，同時保持不同之均勻溫度。對 輻射熱傳部份，本文採用P-3近似法求解。對暫態熱傳情況，本文採 用了時間掃描法(Timemarching algorithm)來處理非穩態能量方程式。 在本文中，有關幾何參數、半徑參數、散射參數(single scattering albedo)、散射相函數(scattering phase function)等等對於介質內 之溫度分佈及熱傳量之影響均做仔細的探討。為了驗證本文中所採用 方法之準確度，本文將一些結果與先前的研究做比較，並得到極佳之 精確度。 在本文中，一種顆粒直徑大約為70埃的超微顆粒絕熱材料Aerosil 380作為實際的例子。應用本文的方法，分析此種超微顆粒絕熱材料 在同心球之間的熱傳現象。主要目標是為了建立此種系統之熱傳模 式，並預測平均溫度、固體顆粒分量以及幾何參數對溫度分佈及熱傳 量之影響。由結果發現在高溫邊界附近輻射熱傳量有一最高值出現。

The steady and transient energy transfers by simultaneous conduction and radiation in an absorbing, emitting, and anisotropically-scattering medium has been investigated theoretically. The medium is confined between two concentric, gray, diffuse and/or specular spherical surfacew which are isothermal but at uniform temperatures. The P3-approximation method is ultilized to solve the radiative heat flux. for transient energy transfer case, a time-marching algorithm is proposed to deal with unsteady energy equatioin. The effects of geometric parameter, geometric radius, single scattering albedo, conduction-to-radiation parameter, and the scattering phase function on the temperature distribution and the heat flux in the medium are examined. In order to demonstrate the accuracy of this methodology, the results of the present study are compared with those of previous study. In this study, an SiO2 ultra-fine powder called Aerosil 380 with particle diameters close to 70 A has also been utilized as an example. The goal is to determine the primary heat transfer mode in the system and to set up models for predicting the effects of mean temperature, solid volume fraction, and geometric parameter on the temperature distribution and total heat flux in the medium. It was found that radiative transfer contribution on the total heat flux has optimal value.