建筑透明表皮室内外热环境之间全波长辐射传热机理研究

发布时间：2018-03-20 00:18

本文选题：长波透明漫射灰体　切入点：辐射传热　出处：《兰州交通大学》2014年博士论文　论文类型：学位论文

【摘要】：目前,大量轻质透明材料(各种玻璃、有机聚合物薄膜)在各种民用建筑围护结构表皮(外窗、透明幕墙、膜结构表皮等)、农业建筑棚膜中的应用日益广泛。在取得采光、视觉美观、以及促进农作物生长等功能效果的同时,其保温隔热的热工性能也很重要,因此有必要对这类材料构造在实际建筑热环境中的传热机理进行研究。本文建立了单层和双层中空透明建筑表皮两侧室内外隔离环境之间的全波长辐射传热稳态计算模型,并利用数值迭代法求解。模型综合考虑了环境长波热辐射、太阳短波热辐射、透明表皮表面附近对流传热、表皮自身导热、以及双层表皮封闭空气间层的对流导热综合传热等多种传热方式和途径,为透明建筑表皮的工程简化传热计算提供了重要依据。相对于非透明建筑表皮的传热过程,透明建筑表皮最大的不同就在于对辐射传热的选择透过性,即具有不同的长波辐射透射率和太阳辐射透射率(短波辐射透射率),这就大大增加了传热过程的复杂性,这也是本文核心的创新点。“透明建筑表皮”是土木建筑学科的语言描述,从传热学的角度描述,当长波辐射透射率不随波长和方向变化时,即可称为“长波透明漫射灰体”,经理论推算验证,本文建立的计算模型同时适用于长波透明漫射灰体(玻璃、有机聚合物薄膜材料)和非透明漫射灰体(砖、石、混凝土等材料)组成的建筑围护结构表皮的稳态传热计算。也就是说,长波透明漫射灰体计算模型当材料的长波辐射透射率趋近于零时的形式等效于传统的非透明漫射灰体的计算模型。利用上述模型,本文选择了普通透明玻璃、低辐射玻璃、PVC聚氯乙烯薄膜和ETFE乙烯四氟乙烯薄膜四种具有代表性的透明材料构成的单层和双层透明建筑表皮共九种方案,根据各种透明材料的热物性参数和透射率特性计算分析了九种方案的系统总热流强度、总传热系数、太阳辐射得热系数、有效长波辐射透射系数和表面长波辐射换热系数五个传热特性指标。其中本文定义的有效长波辐射透射系数是描述透明建筑表皮受实际环境长波透射辐射作用影响程度的重要指标。传热特性指标的基本变化规律是:(1)长波辐射透射率越大的材料,无太阳辐射时,系统总热流强度、总传热系数、有效长波辐射透射系数、表面长波辐射换热系数越大,即长波透射辐射对系统传热起到正向增强作用;(2)有太阳辐射时情况会复杂化,冬季工况下长波透射辐射对系统传热起反向削弱作用(有利于保温和增加室内得热),而夏季工况下长波透射辐射对系统传热起正向增强作用(不利于隔热和减小室内得热);(3)太阳辐射得热系数的变化规律主要与各层材料太阳辐射透射率和吸收率有关,太阳辐射透射率越大则太阳辐射得热系数越大(不利于遮阳),太阳辐射吸收率越大则太阳辐射得热系数越小(有利于遮阳)。此外,本文将上述计算模型中的三个环境边界计算条件作为敏感性因素,对单层普通透明玻璃、单层ETFE薄膜、普通双层中空玻璃、双层ETFE薄膜四种具有代表性的透明建筑表皮的系统总热流强度、有效长波辐射透射系数和太阳辐射得热系数三个主要的传热特性指标的影响程度进行了分析,这三个敏感性因素是:透明表皮与室内表面面积比、透明表皮两侧对流换热系数、两侧隔离环境表面温度与空气温度的差异。分析结果表明,太阳辐射得热系数与上述三个敏感性因素无关,三个敏感性因素对系统总热流强度和有效长波辐射透射系数的影响程度是:(1)透明表皮与室内表面面积比的影响程度甚微,工程计算中可忽略;(2)透明表皮两侧对流换热系数的影响程度较小,传热特性指标计算结果偏差小于5%的情况下,在工程计算中可忽略;(3)两侧隔离环境表面温度与空气温度的差异影响程度较大,当透明建筑表皮不受太阳辐射作用时,两侧隔离环境表面温度与空气温度的小温差差异对透明表皮传热特性指标的影响程度相对较小,当透明建筑表皮受太阳辐射作用时,室外环境表面温度与空气温度的大温差差异对传热特性指标的影响程度相对较大,在工程计算中所选择的传热特性指标计算结果偏差小于5%的情况下,可忽略其影响,否则不可忽略。一般温室效应认为普通硅酸盐透明玻璃的长波辐射透射率很小,长波透射辐射可以忽略。为此,本文在理论模型基础上,采用水循环加热法实验验证了单层普通硅酸盐透明玻璃长波透射辐射的存在性。本文最后对建筑表皮隔离两侧室内外环境的传热系统各表面辐射特性(温度、发射率等)为非均匀性时的传热模型作了初步探索,采用基于蒙特卡洛法的辐射传热数值计算方法对一简单的封闭隔离环境之间隔以导热系数无限大的薄板的二维辐射传热问题进行了数值求解。为今后进一步从传热学的角度研究长波透明漫射灰体隔离环境间的辐射传热课题奠定一定基础。
[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.

【学位授予单位】：兰州交通大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU111

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