摘要
本文根据辐射传热和对流传热理论，利用Ｍａｔｌａｂ 程序结合太阳能热水器本身的尺寸以及与其有关的水和空气的物理弹性详细分析了影响平板式太阳能热水器热效率的因素包括太阳能热水器表面的太阳光辐射的吸收率αｓ 和辐射系数ε，太阳能热水器的水进口温度Ｔｃ，ｉｎ和流量ｍｃ 太阳辐射能力Ｇｓ，，环境大气温度Ｔｅ，大气辐射系数εｓｋｙ 以及太阳能热水器内部的总传热系数Ｕ。分析结果表明较高的太阳照射能力、环境温度和总传热系数有利于提高集热效率，而增加水量和水进口温度、热水器辐射系数和大气辐射系数则有相反的效果。
This paper is intended to estimate the radiation and convection heat transfer from a plat-plate solar collector used to heat water and evaluate the effects of the factors including solar absorptance α s ,emittance ε , entrance temperature of water T c,in , flow rate of water m c , solar irradiation G s , environmental temperature T e , sky emittance ε sky and overall heat transfer coefficient from the absorbing surface to the bulk water U on the collector efficiency η . Based on the related laws of radiation, convection, energy conservation, thermal properties of air and water and physical characteristics of referred flat-plate solar collector, a numerical MATLAB program is applied for calculating the temperature of absorbing surface T s , the exit temperature T c , and consequently η under the different conditions of factors mentioned above. The numerical method has shown that the increase of G s, T e or U will improve the collector efficiency but increase of m c ,ε, T c,in , and ε sky will inversely affect the collector efficiencies.
