适于温室应用的无机相变材料放热特性

Exothermic Characteristics of Inorganic Phase Change Materials Suitable for Greenhouse Applications

为了研究温室常用CaCl2·6H2O、Na2CO3·10H2O、Na2SO4·10H2O、Na2HPO4·12H2O四种无机相变材料在不同环境条件下的放热特性,实验设置冷水和空气两种介质条件,分别在5℃、10℃和15℃温度条件下凝固,测试四种相变材料在不同介质和温度条件下的相变温度和过冷度。实验结果表明,CaCl2·6H2O相变温度为30℃左右,15℃条件下不能凝结放热。Na2CO3·10H2O相变温度为31℃左右,Na2SO4·10H2O放热不稳定,相变潜热小,5℃条件下纯在明显的二次放热现象,Na2HPO4·12H2O相变温度为33℃左右。比较不同环境条件下的过冷度得出空气环境中相变材料的过冷度均小于冷水环境中。随着温度的升高,CaCl2·6H2O的过冷度逐渐减小,Na2CO3·10H2O的过冷度逐渐增大,Na2SO4·10H2O、Na2HPO4·12H2O的过冷度没有明显变化。过冷度与冷却环境中传热介质的导热性能有关,导热性能越强(水的导热性能强于空气),相变凝固过程中持续放热时间越短。

In order to explore exothermic characteristics of four inorganic phase change materials of CaCl2·6H2O,Na2CO3·10H2O,Na2SO4·10H2O and Na2HPO4·12H2O under different environmental conditions,the experimental conditions were set between cold water and air.The phase change temperature and supercooling degree of four phase change materials under different media and temperature conditions were tested in 5,10 and 15℃temperature solidification.Experimental results showed that phase change temperature of CaCl2·6 H2O was about 30℃,it could not condense and release heat at 15℃;the phase transition temperature of Na2CO3·10H2O is about 31℃,the heat release of Na2SO4·10H2O was unstable,the latent heat of phase transition was small,and the secondary heat release phenomenon was obvious at 5℃;the phase transition temperature of Na2HPO4·12H2O was about 33℃.Supercooling degree of phase change materials in air environment was lower than that in cold water environment by comparing supercooling degree under different environmental conditions.With the increase of temperature,the supercooling degree of CaCl2·6 H2O decreased gradually,while that of Na2CO3·10H2O increased gradually.The supercooling degree of Na2SO4·10H2O and Na2HPO4·12H2O had no obvious change.The degree of supercooling was related to thermal conductivity of heat transfer medium in cooling environment.The stronger the thermal conductivity(the thermal conductivity of water was stronger than that of air),the shorter the continuous heat release time in the phase change solidification process.