Thermal Environment Model In Chinese Solar Greenhouse Based On VB And MATLAB And Structure Optimization

Chinese solar greenhouse is one unique greenhouse type in china, with low cost, energy-saving and good economic benefits. Wall played an important role in heat storage and heat preservation. However, there is low using efficiency of soil derived from unreasonable wall structure. Based on the previous work of experts, the simulation model of thermal environment in Chinese solar greenhouses with VB and MATLAB was established. Experiments were done to validate the model and some optimization for typical region was implemented. The conclusions were as follows:In this paper the solar radiation, heat radiation, heat convection, heat conduction, natural ventilation, water demonstrating were described quantitatively. And the impacts on thermal environment were analyzed. According to thermodynamic law of conservation of mass and energy and heat transfer theory, a group of differential equations on thermal balance of cover, thermal balance of indoor air, thermal balance of north wall, thermal balance of soil, thermal balance of north roof, thermal balance of plant and mass balance of water vapor were built. The feature of model is that layers of north wall,soil and north roof were considered respectively. The latent heat of water was considered in each equation. The simulation model was developed with MATLAB procedures, used to solve differential equations, and good user interface of VB, The COM builder made the MATLAB function as component. Which was dependent from MATLAB environment. VB could transfer this component. The outside meteorological data, greenhouse structure parameters, parameters of north wall, north roof, soil, plant and cover. The temperatures of different parts at different time could be calculated.Comparing the measured data of environment factors in greenhouse with the simulated values,IA of indoor air temperature was 0.74, IA of north wall surface temperature was 0.83, IA of soil surface temperature was 0.79。It was shown that model could simulate the temperature change generally.The regional structure optimizations for typical greenhouse were calculated by model. Some results were found: to meet lowest indoor temperature of 8℃in the night, the thickness of clunch wall in Beijing was 0.70m, the thickness of clunch wall in Shenyang was 1.20m, the thickness of clunch wall in Shouguang was 0.65m. The temperature increased when added some heat insulation materials inside or outside north roof. If the thickness of heat insulation was 0.20m, the increase temperature was up to 1.3℃.