Abstract:The heat storage of back wall of the solar greenhouse reduces efficiency of ventilation and cooling. High temperature will stimulate plant water transpiration and reduce the utilization rate of water resources. Taking Beijing Tongzhou solar greenhouse as the research object, on the basis of the original upper and lower vents, the rear wall vents were added. Based on DO radiation model, component transport model and porous medium model, a computational fluid dynamics (CFD) model of solar greenhouse was established. The microenvironment of greenhouse under different ventilation modes was explored, and the transpiration characteristics of crops were obtained by combining crop transpiration model analysis. The results showed that the change of temperature would directly affect the intensity of crop transpiration, and the spatial distribution characteristics of the two were consistent. The high temperature of the greenhouse at noon, the opening of the back wall and the lower vent, compared with the original opening of the upper and lower vent, the airflow trend was similar, due to the reduction of part of the heat storage wall, the cooling efficiency was increased by 5.7%, and the transpiration was decreased by 0.020mm/h, the opening of the back wall, the upper and lower vent, the transpiration was decreased by 0.005mm/h. After opening the back wall and the upper vent, because the two vents were close to one side and far away from the crop, only the north side can be partially cooled, the cooling efficiency was reduced by 10.3%, the dehumidification efficiency was increased by 5.7%, and the transpiration was increased by 0.035mm/h. In addition, in the combination of vents, the lower vent was set in the windward direction, which can reduce the energy and momentum loss of the external wind and improve the ventilation cooling efficiency. The results provided a reference for the regulation of microenvironment in solar greenhouse.
