Low-E玻璃U值及其影响因素的计算分析

Calculation and Analysis of U Value for Low-E Glass Units

应用传热学原理,分析了Low-E玻璃构件传热基本过程,给出了总传热系数U值计算的详细表达式,并在计算机上进行了数值计算,研究了各种参数对U值的影响。计算结果表明:玻璃厚度对U值影响不明显;影响U值的主要因素是气体间隔层厚度和玻璃的辐射率;随着气体间隔层厚度增加,U值逐渐降低,达最低值后缓慢上升,有一个最佳的厚度;随着辐射率降低,U值逐渐降低,但U值与辐射率并不呈现简单的线性关系,对给定的Low-E玻璃构件,有一个极限U值。

Heat transfer processes through a Low - E glass unit were analyzed and a set of mathematical equations for overall heat transfer coefficient, i.e. U value was established. U value was then calculated by a computer. The influences of glass thickness, gas gap between two glass sheets, type of filling gas, and the emissivity of Low - E glass coating on U value have been studied. Calculated results show that U value is not sensitive to glass thickness. The gas gap between two glass sheets and the emissivity of Low - E glass coating have substantial effects on U value. With increasing gas gap between two glass sheets the U value gradually decreases to a critical point, and then slowly goes up. Therefore, there exists an optimal gas gap. With decreasing emissivity of Low - E glass coating the U value gradually decreases. The relationship between U value and coating emissivity is not a simple linear function. There is a minimal U value for a given Low - E unit.