Design And Testing Of Phase Change Wallboard For Greenhouse Applications

Phase change material is a new type of green energy resource,which has been widely concerned by scholars at home and abroad due to its high thermal conductivity,large latent heat of phase change,low price,non-flammability and many other advantages.A large number of studies show that if phase change materials are applied in greenhouse,it can improve greenhouse night temperature,reduce energy consumption,reduce harmful gas emissions,and realize energy conservation and emission reduction in solar greenhouse production.Starting from the characteristics of large temperature difference between day and night and excess heat at noon and insufficient heat at night in Urumqi sunlight greenhouse,this paper studies from four aspects of sunlight greenhouse temperature and light environment test,phase change material screening,composite phase change material preparation,phase change wall board design and performance test,and draws the main conclusions as follows:(1)Through testing the internal light and temperature environment of the solar greenhouse in Urumqi area,the analysis shows that the solar greenhouse in Urumqi area has good light and temperature conditions,but the temperature difference between day and night is large.If phase change materials are applied to the solar greenhouse in this area,the phase change characteristics of phase change materials can be used to improve the temperature environment of the solar greenhouse and reduce the temperature difference between day and night.(2)Through the test of the exothermic performance of the inorganic phase change materials commonly used in the four kinds of greenhouses,CaCl2·6H2O、Na2SO4·IOH2O、Na2CO3·1OH2O、Na2HPO4·12H2O,in the two media of air and cold water under different temperature conditions,the test concluded that CaCl2·6H2O Although there is a supercooling phenomenon,the phase transition temperature is appropriate and the heat release time is long.Considering the experiment,it is considered that CaCl2·6H2O can be further explored and applied in the greenhouse.(3)The effects of different mass ratios of MgCl2·6H2O and SrCl2·6H2O on the phase transition temperature and subcooling of CaCl2·6H2O were tested under different temperature conditions.According to the comprehensive comparison,it is considered that the addition of wt.30%MgCl2·6H2O and wt.1%SrCl2·6H2O is ideal for CaCl2·6H2O to reduce the phase transition temperature,the degree of subcooling,and increase the exothermic surface.(4)By calculating the heat and heat storage capacity of the greenhouse brick wall and the phase change wall panel,it can be seen that the heat and heat storage capacity ratio of the phase change wall panel is significantly higher than that of the greenhouse brick wall,indicating that the phase change wall panel is superior to the greenhouse brick wall in heat and heat storage capacity.The temperature change,heat flow change,heat storage and release during crystallization and melting of phase change wallboards with different thicknesses under laboratory conditions and greenhouse conditions are comprehensively compared,as well as the heat storage and release performance of phase change wallboards with different thicknesses and greenhouse brick walls.The experimental results show that phase change wallboards have larger heat storage capacity and higher heat storage and release efficiency than greenhouse brick walls,and their reasonable thickness should be between 2～3cm and 3 cm when applied to sunlight greenhouses in Urumqi region.