In the study of solar greenhouses, microclimate, soil, and back walls have an important influence on the greenhouse thermal environment because of their good heat storage and release characteristics. The transpiration of crops makes indoor humidity increase sharply, which is the main factor affecting indoor humidity distribution. Therefore, it is of great significance to grasp the microclimate change law of solar greenhouses and study the coupling effect of thermal and humidity environment. In this paper, based on computational fluid dynamics (CFD), a three-dimensional model of the thermal and humidity environment of a solar greenhouse is established, and the indoor temperature and humidity distribution under the influence of soil, crops, and back walls are considered. The CFD model initialization uses binary fitting functions to fit the temperature distribution of soil, back wall, and air. The distribution law of the temperature field and relative humidity field of the solar greenhouse under three different working conditions is simulated, that is, the insulation is uncovered and the ventilation window is closed during the day (G1), the insulation is uncovered and the ventilation window is opened during the day (G2), and the insulation is put down and the ventilation window is closed at night. (G3). The results show that the simulation results are in good agreement with the actual results under the three working conditions, and this paper can provide a reference for the improvement of the greenhouse structure and environmental regulation.

Optimization of Chinese solar greenhouse building parameters based on CFD simulation and entropy weight method

In order to quantitatively analyze the light radiation environment inside Chinese solar greenhouse (CSG) and select reasonable building design parameters, a CSG solar radiation environment model reflecting various factors such as geographical location, outside solar radiation, orientation and building parameters, front roof shape, and covering materials was studied. The model considered the impact of both cloudy and sunny weather conditions on the inside solar radiation environment, and established a simulation calculation method for inside direct radiation and scattered radiation. When calculating solar scattered radiation, the ground reflected radiation and atmospheric longwave radiation was considered. When calculating the transmittance of covering material, a structural shading loss and dust film model was introduced to calculate its impacts on the transmittance. The model was validated experimentally in a CSG at Yongqing in Hebei Province, China. The results showed that the model can effectively simulate the solar radiation of various points such as the ground and wall in the greenhouse at any time, with an average relative error of 8.19% between the simulated and measured values. Based on the established model, the impact of the geographical location, azimuth angle, and building parameters of CSG on inside solar radiation were analyzed. The research results can provide theoretical references and relevant data for the wall and soil heat storage, crop planting, and energy balance of enclosure structures in CSG.