Simulation Study On The Application Of Phase Change Wallboard In Solar Greenhouse

Solar greenhouse provides conditions for cross-season planting,It has been widely used in our country,especially in north China.In recent years,the construction area of solar greenhouse in China has been increasing year by year.Solar greenhouse has the advantages of simple equipment and low cost.Solar greenhouse has the advantages of simple equipment and low cost,but it also has the problems of high production cost and low production efficiency in winter.Solar greenhouse is in urgent need of transformation to energy-saving solar greenhouse.The wall of solar greenhouse bears multiple functions of heat storage,load bearing and heat preservation,and is one of the main sources of night heat in solar greenhouse.Phase change material(PCM)is a new type of highly efficient energy storage material,which can absorb or store a large amount of latent heat during phase change.If PCM is combined with the back wall of greenhouse,the heat storage capacity of solar greenhouse wall is expected to be greatly improved.Previous research on phase-change materials in solar greenhouses mainly includes two aspects: one is to develop phasechange materials suitable for solar greenhouses;the other is to study the actual effect of phase-change materials.The research methods are mostly experimental studies,and there is a lack of research on the heat transfer process of walls.Based on the above background,this paper takes the multi-layer phase-change wall of solar greenhouse as the object,and studies the heat transfer characteristics of the multi-layer phase-change wall of solar greenhouse and the application effect of phase-change material based on Fluent and Matlab software.The heat transfer model of multi-layer phase-change wall was established.For different phase-change materials and different wall materials,the influence of different layer thickness of phase-change material on the heat transfer process of multi-layer phase-change wall was simulated and studied by FLUENT software.The results show that the clay block wall has good heat storage and release capacity,but its thermal insulation is poor,and the thickness of the clay block wall is larger to meet the requirement of low thermal limit resistance in the design of solar greenhouse.Aerated concrete has the advantages of good heat preservation effect and small occupation area,but its heat storage and release capacity is poor,which is not conducive to the temperature control of solar greenhouse.Four different kinds of walls were constructed,and it was found by numerical simulation that there was an optimal thickness of phase change layer for different wall materials and different phase change materials.At the same time,it is found that there is a great difference in temperature variation between isothermal phase change materials and interval phase change materials.The heat balance equation of phase-change solar greenhouse was established and solved by MATLAB software programming,and the mathematical model was verified by experiments.Based on the established mathematical model,the temperature variation in the solar greenhouse with two different multi-layer phase change walls was simulated under different weather conditions in Handan area.The results show that under different weather conditions,PCM can control the thermal environment inside the greenhouse.In sunny days and cloudy days,PCM can reduce the peak and fill the valley of the air temperature inside the greenhouse and the inner surface temperature of the wall.Overcast days can increase the air temperature in the greenhouse and the inner surface temperature of the wall;Even on the coldest days in Handan,the temperature in the greenhouse can be raised.The temperature of greenhouse soil in 10 cm depth and20 cm depth can be improved to a certain extent.At the same time,compared with two different wall structures,it is found that the temperature control effect of phase change material on aerated concrete block wall is more significant.In this paper,the application of phase-change wall in solar greenhouse was studied by numerical simulation.The heat transfer characteristics of different walls and the influence of phase-change material on the air temperature in greenhouse were analyzed,and some conclusions about the heat transfer characteristics of phase-change wall and the application effect of phase-change material were obtained.The research results provide a certain reference value and theoretical basis for the application of phase change materials in solar greenhouse.