本文選題：長波透明漫射灰體　切入點：輻射傳熱　出處：《蘭州交通大學》2014年博士論文　論文類型：學位論文

【摘要】：目前,大量輕質(zhì)透明材料(各種玻璃、有機聚合物薄膜)在各種民用建筑圍護結(jié)構(gòu)表皮(外窗、透明幕墻、膜結(jié)構(gòu)表皮等)、農(nóng)業(yè)建筑棚膜中的應(yīng)用日益廣泛。在取得采光、視覺美觀、以及促進農(nóng)作物生長等功能效果的同時,其保溫隔熱的熱工性能也很重要,因此有必要對這類材料構(gòu)造在實際建筑熱環(huán)境中的傳熱機理進行研究。本文建立了單層和雙層中空透明建筑表皮兩側(cè)室內(nèi)外隔離環(huán)境之間的全波長輻射傳熱穩(wěn)態(tài)計算模型,并利用數(shù)值迭代法求解。模型綜合考慮了環(huán)境長波熱輻射、太陽短波熱輻射、透明表皮表面附近對流傳熱、表皮自身導熱、以及雙層表皮封閉空氣間層的對流導熱綜合傳熱等多種傳熱方式和途徑,為透明建筑表皮的工程簡化傳熱計算提供了重要依據(jù)。相對于非透明建筑表皮的傳熱過程,透明建筑表皮最大的不同就在于對輻射傳熱的選擇透過性,即具有不同的長波輻射透射率和太陽輻射透射率(短波輻射透射率),這就大大增加了傳熱過程的復雜性,這也是本文核心的創(chuàng)新點。“透明建筑表皮”是土木建筑學科的語言描述,從傳熱學的角度描述,當長波輻射透射率不隨波長和方向變化時,即可稱為“長波透明漫射灰體”,經(jīng)理論推算驗證,本文建立的計算模型同時適用于長波透明漫射灰體(玻璃、有機聚合物薄膜材料)和非透明漫射灰體(磚、石、混凝土等材料)組成的建筑圍護結(jié)構(gòu)表皮的穩(wěn)態(tài)傳熱計算。也就是說,長波透明漫射灰體計算模型當材料的長波輻射透射率趨近于零時的形式等效于傳統(tǒng)的非透明漫射灰體的計算模型。利用上述模型,本文選擇了普通透明玻璃、低輻射玻璃、PVC聚氯乙烯薄膜和ETFE乙烯四氟乙烯薄膜四種具有代表性的透明材料構(gòu)成的單層和雙層透明建筑表皮共九種方案,根據(jù)各種透明材料的熱物性參數(shù)和透射率特性計算分析了九種方案的系統(tǒng)總熱流強度、總傳熱系數(shù)、太陽輻射得熱系數(shù)、有效長波輻射透射系數(shù)和表面長波輻射換熱系數(shù)五個傳熱特性指標。其中本文定義的有效長波輻射透射系數(shù)是描述透明建筑表皮受實際環(huán)境長波透射輻射作用影響程度的重要指標。傳熱特性指標的基本變化規(guī)律是:(1)長波輻射透射率越大的材料,無太陽輻射時,系統(tǒng)總熱流強度、總傳熱系數(shù)、有效長波輻射透射系數(shù)、表面長波輻射換熱系數(shù)越大,即長波透射輻射對系統(tǒng)傳熱起到正向增強作用;(2)有太陽輻射時情況會復雜化,冬季工況下長波透射輻射對系統(tǒng)傳熱起反向削弱作用(有利于保溫和增加室內(nèi)得熱),而夏季工況下長波透射輻射對系統(tǒng)傳熱起正向增強作用(不利于隔熱和減小室內(nèi)得熱);(3)太陽輻射得熱系數(shù)的變化規(guī)律主要與各層材料太陽輻射透射率和吸收率有關(guān),太陽輻射透射率越大則太陽輻射得熱系數(shù)越大(不利于遮陽),太陽輻射吸收率越大則太陽輻射得熱系數(shù)越小(有利于遮陽)。此外,本文將上述計算模型中的三個環(huán)境邊界計算條件作為敏感性因素,對單層普通透明玻璃、單層ETFE薄膜、普通雙層中空玻璃、雙層ETFE薄膜四種具有代表性的透明建筑表皮的系統(tǒng)總熱流強度、有效長波輻射透射系數(shù)和太陽輻射得熱系數(shù)三個主要的傳熱特性指標的影響程度進行了分析,這三個敏感性因素是:透明表皮與室內(nèi)表面面積比、透明表皮兩側(cè)對流換熱系數(shù)、兩側(cè)隔離環(huán)境表面溫度與空氣溫度的差異。分析結(jié)果表明,太陽輻射得熱系數(shù)與上述三個敏感性因素無關(guān),三個敏感性因素對系統(tǒng)總熱流強度和有效長波輻射透射系數(shù)的影響程度是:(1)透明表皮與室內(nèi)表面面積比的影響程度甚微,工程計算中可忽略;(2)透明表皮兩側(cè)對流換熱系數(shù)的影響程度較小,傳熱特性指標計算結(jié)果偏差小于5%的情況下,在工程計算中可忽略;(3)兩側(cè)隔離環(huán)境表面溫度與空氣溫度的差異影響程度較大,當透明建筑表皮不受太陽輻射作用時,兩側(cè)隔離環(huán)境表面溫度與空氣溫度的小溫差差異對透明表皮傳熱特性指標的影響程度相對較小,當透明建筑表皮受太陽輻射作用時,室外環(huán)境表面溫度與空氣溫度的大溫差差異對傳熱特性指標的影響程度相對較大,在工程計算中所選擇的傳熱特性指標計算結(jié)果偏差小于5%的情況下,可忽略其影響,否則不可忽略。一般溫室效應(yīng)認為普通硅酸鹽透明玻璃的長波輻射透射率很小,長波透射輻射可以忽略。為此,本文在理論模型基礎(chǔ)上,采用水循環(huán)加熱法實驗驗證了單層普通硅酸鹽透明玻璃長波透射輻射的存在性。本文最后對建筑表皮隔離兩側(cè)室內(nèi)外環(huán)境的傳熱系統(tǒng)各表面輻射特性(溫度、發(fā)射率等)為非均勻性時的傳熱模型作了初步探索,采用基于蒙特卡洛法的輻射傳熱數(shù)值計算方法對一簡單的封閉隔離環(huán)境之間隔以導熱系數(shù)無限大的薄板的二維輻射傳熱問題進行了數(shù)值求解。為今后進一步從傳熱學的角度研究長波透明漫射灰體隔離環(huán)境間的輻射傳熱課題奠定一定基礎(chǔ)。
[Abstract]:At present, a large number of light transparent materials (glass, organic polymer film) in the epidermis of various civil building envelope (windows, transparent curtain wall, membrane structure, skin etc.) and application of agricultural building films are increasingly widespread. In lighting, visual appearance, and promote the effect of the growth of crops and other functions at the same time, the thermal performance of the heat preservation the insulation is also very important, so it is necessary to study the heat transfer mechanism of this kind of material structure in the actual building thermal environment. This paper establishes single-layer and double-layer hollow transparent building skin on both sides of indoor and outdoor environment between the isolated full wavelength calculation model of radiative heat transfer in steady state, and solved by numerical iteration method. The model considers the long wave thermal radiation, solar radiation heat, near the transparent skin surface convective heat transfer, heat transfer and its skin, double skin closed air layer convection conduction. Heat and other heat transfer way, simplified heat transfer building skin transparent engineering provides an important basis for the calculation of the heat transfer process. Compared with the non transparent building skin, transparent building skin, the biggest difference is that the radiative heat transfer through sexual selection, which has long wave radiation transmittance and solar radiation transmittance different (shortwave radiation transmission), which greatly increases the complexity of the heat transfer process, which is the core of innovation. The "transparent skin" is a civil subject language description, description from the perspective of heat transfer, when the long wave radiation transmittance with wavelength and direction change, can be called "long wave transparent diffuse gray body, the to verify the theoretical calculation, the model established in this paper is also applicable to the long wave transparent diffuse gray body (glass, organic polymer film materials) and non transparent diffuse gray (brick, stone, concrete body etc. Material) calculation of steady state heat transfer of building envelope is composed of the epidermis. That is to say, the calculation model of non transparent diffuse gray body wave transparent diffuse gray body model when the long wave radiation transmission material tends to zero is equivalent to traditional form. By using the above model, this paper chose the ordinary transparent glass, Low-E glass, monolayer a PVC PVC film and ETFE film and tetrafluoroethylene four transparent materials representative and double transparent building skin consists of nine types of programs, according to the various characteristics of transparent material thermal parameters and transmittance calculation analysis of the system total heat flux intensity of the nine schemes, the total heat transfer coefficient, solar heat gain coefficient, effective long wave radiation transmission coefficient and surface long wave radiation heat transfer coefficient is five. The effective index of the heat transfer characteristics of long wave radiation transmission coefficient is defined in this paper through the description of Ming Jian An important indicator of the degree to build the epidermis from the actual environment. The effects of long wave radiation heat transfer characteristics of the basic law index is: (1) the greater the longwave radiation transmittance material, no radiation, the total heat flux, heat transfer coefficient, the effective longwave radiation transmission coefficient, surface longwave radiative heat transfer coefficient is larger. The long wave radiation to the forward transmission enhancement of heat transfer system; (2) with the solar radiation will be complicated, long wave radiation transmission under winter condition reverse weakening effect on the heat transfer system (for insulation and indoor heat gain), and summer conditions of long wave transmission radiation has a positive effect on the heat transfer enhancement system (not conducive to heat insulation and reduce indoor heat); (3) the solar radiation variation coefficient of heat is mainly related to the material of each layer of solar radiation transmittance and absorption rate, the greater the solar radiation transmittance of solar radiation The heat coefficient is larger (for shading), solar radiation absorption rate the greater the solar heat gain coefficient is small (for shading). In addition, the calculation model of the three boundary conditions as the environment sensitive factors of single-layer ordinary transparent glass, single layer ETFE thin film, double-layer hollow glass, total heat flux intensity of double layer ETFE film four representative transparent architectural surface, the influence degree of the effective longwave radiation transmission coefficient and solar heat gain coefficient of the three main indexes of heat transfer characteristics were analyzed, the three sensitivity factors are: transparent skin and interior surface area ratio, transparent skin on both sides of the convection the heat transfer coefficient, the difference of both sides of the isolation environment of surface temperature and air temperature. The analysis results show that the solar heat gain coefficient has nothing to do with these three sensitive factors, three sensitive factors of the system The influence degree of the total heat flux intensity and long wave radiation transmission coefficient is: (1) the degree has little effect on the transparent skin and interior surface area ratio, and can be neglected in engineering calculation; (2) transparent skin on both sides of the convective heat transfer coefficient influence index of heat transfer calculation results deviation is less than 5%, can be ignored in engineering calculation; (3) influence on both sides of the isolation environment of surface temperature and air temperature is larger, when the transparent building skin from the sun's radiation, the influence degree of small temperature difference at the isolation environment surface temperature and air temperature on the heat transfer characteristics of transparent skin is relatively small, when the transparent building skin by solar radiation when the influence degree of large temperature differences in outdoor environment of surface temperature and air temperature on the heat transfer characteristics of the index is relatively large, the heat transfer characteristics of index selection in engineering calculation Result the error is less than 5%, it can be neglected, otherwise can not be ignored. The greenhouse effect that longwave radiation transmittance of Portland transparent glass is very small, long wave radiation can be neglected. Therefore, based on the theoretical model, the water circulation heating experiment verifies the existence of radiation single Portland long wave transmission. Finally, transparent glass heat transfer system of the skin isolation of both indoor and outdoor environment, the surface radiation characteristics (temperature, emissivity) made a preliminary exploration for the non-uniform heat transfer model of the two-dimensional radiative transfer calculation method of radiative heat transfer numerical Monte Carlo method based on a simple isolation between closed environment the vibration plate to infinite thermal conductivity were solved numerically. For further research from the perspective of heat transfer wave transparent diffuse gray body The subject of radiation heat transfer in isolation environment will lay a certain foundation.

【學位授予單位】：蘭州交通大學
【學位級別】：博士
【學位授予年份】：2014
【分類號】：TU111

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