Simulation of temperature variations for various wall materials in Chinese solar greenhouses using computational fluid dynamics

Wall materials play an important role in heat conservation for Chinese solar greenhouses. External climatic conditions were used here as inputs in simulations of the temperature environments for layered wall, brick wall and polystyrene foam plate (PFP) wall greenhouses with a span of 12 meters. The predicted wall temperature profiles agreed well with existing experimental results. External climatic conditions measured on Feb. 18, 2004 were used as the input, with the predicted maximum air temperature for the layered wall greenhouse 0.8℃ higher than that for the brick wall greenhouse and that for the layered wall greenhouse 1.0℃ higher than that for the PFP wall greenhouse. The thermal sources in the three types of greenhouses in the morning before the felt insulation was rolled up off consisted of the inside layer of brick and part of the insulating layer for the layered wall. Temperature of one third of the inside wall for the brick wall was higher than air temperature inside the greenhouse. The wall temperatures inside the layered wall, the brick wall and the PFP wall were below the air temperature inside the greenhouses during the day with the thermal blanket unrolled. The model accurately predicts the air temperatures inside greenhouses with various kinds of walls, so it can be used to select wall structures based on the temperature profiles inside different walls.