Temperature variations with various enclosure material thermal property for a Chinese solar greenhouse

Abstract.

Chinese solar greenhouse (CSG) enclosures have a south roof, a north roof and walls (a north wall and side walls). Large thermal masses in the north wall, north roof and soil enable the CSG to produce vegetables during the winter without auxiliary heating. The relationship between the CSG enclosure material properties and the inside thermal environment was investigated by varying the thermal conductivity and specific heat of various parts of a 12 m span CSG with predictions of the internal thermal environment using a previously validated computational fluid dynamics (CFD) model. The thermal conductivity or specific heat was changed one at a time to half or double the base case value in the thermal blanket on the south roof, the north roof and the heat storage layer or insulation layer of the north wall. The results show that the air temperature was much higher than in the original CSG design when using half of the thermal conductivity for the south roof blanket, with the air temperature more than 2°C higher during the night, while the other thermal property changes in the south roof blanket and in the other parts changed the inside air temperature by less than 0.2°C. When the total north wall thickness was increased from 0.6 m to 0.72 m with the same thickness of the heat storage layer near the inside surface, the air temperature increased by nearly 1°C during the night. The surface temperatures changes resulting from the enclosure material changes were also analyzed. This simulation results can be used to improve CSG enclosure material selection and wall construction methods.