应用于日光温室墙体的相变材料热物性优化研究

STUDY ON OPTIMIZATION OF THERMOPHYSICAL PROPERTIES OF PHASE CHANGE MATERIALS USED IN SOLAR GREENHOUSE WALLS

建立日光温室计算传热模型,以室内空气温度和墙体内表面温度为指标,通过实验方法验证了所建立的传热模型准确性,最后分析相变材料相变温度、相变焓、导热系数、密度等热物性对室内最低温度和相变蓄热率的影响规律,确定被动式相变蓄热墙体和主-被动式相变蓄热墙体的最佳相变材料热物性,阐明了实际应用时相变材料选择原则。研究结果表明,所建立的日光温室传热模型具有较高准确性,可用于日光温室墙体相变材料热物性优化;主-被动式相变蓄热墙体最佳相变材料的相变温度为27℃,相变焓为200 kJ/kg,导热系数为0.35 W/(m·K),密度为440 kg/m3,被动式相变蓄热墙体最佳相变材料的相变温度为26℃,相变焓为200 kJ/kg,导热系数为0.35 W/(m·K),密度为792 kg/m3;最佳相变材料热物性应用时,2种墙体室内最低温度均可达到15.0℃,但是被动式相变蓄热墙体的相变蓄热率较主-被动式相变蓄热墙体减小29.5%。本研究可为相变材料在日光温室的高效利用提供参考。

The heat transfer calculation model of solar greenhouse was established.Its accuracy was validated by experimental methods with the indicators of the indoor air temperature and the inner surface temperature of the wall.Finally,the influence of different thermophysical properties of phase change materials,namely phase change temperature,heat of fusion,thermal conductivity and density,on the indoor minimum temperature and the phase change heat storage rate was analyzed,then the optimal thermophysical properties of phase change materials applied for both phase change heat storage walls were determined,and the selection principle of phase change material in practical application was clarified.The results show that the developed heat transfer calculation model of solar greenhouse has a high accuracy,with the average error of indoor air temperature of 0.31℃and the average error of inner surface temperature of 1.34℃.The developed heat transfer calculation model can be used for the optimal thermophysical properties of phase change materials used in solar greenhouse walls.The optimal thermophysical properties of phase change material applied for the active-passive phase change heat storage wall included the phase change temperature of 27℃,the phase change enthalpy of 200 kJ/kg,the thermal conductivity of 0.35 W/(m·K),the density of 440 kg/m3.The optimal thermophysical properties of phase change material applied for the passive phase change heat storage wall included the phase change temperature of 26℃,the phase change enthalpy of 200 kJ/kg,the thermal conductivity of 0.35 W/(m·K),the density of 792 kg/m3.The minimum indoor air temperature of the solar greenhouse with the optimal phase change material could reach 15.0℃,but the phase change heat storage rate of the passive phase change heat storage wall was 46.4%,which was 29.5%lower than that of the active-passive phase change heat storage wall.This study can provide a reference for the application of phase change materials in solar greenhouse.