Abstract:
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 activepassive 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 of200 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.