| The greenhouse solar heat collection is the most important way to warm up the greenhouse.It is the focus of current research that collecting excess solar energy in the greenhouse to provide heat for the greenhouse under extreme weather conditions for multiple days.In order to solve the following problems of greenhouse heat storage devices:the use of single insulation materials,simple structure design,large heat loss,and limited heat storage capacity.Conducted the following research:Setting up a multi-phase change heat storage structure to increase the heat storage capacity of the heat storage device;Designing composite heat insulation material combination;Optimizing the design of the hot water storage tank and constructing the actual heat storage mathematical model.The main research conclusions are as follows:1.Screening and thermodynamic testing of 22 kinds of insulation materials and design a composite external insulation structure that combines multiple heat storages.The best thermal insulation combination for greenhouse water tanks is thermal insulation coating+aerogel+rubber and plastic thermal insulation cotton.When the thickness of the composite material is100 mm,its heat transfer coefficient is 0.283 W·m-2·k-1.The thickness of the greenhouse water tank insulation material is in the range of 80-120 mm.It can not only ensure a lower heat dissipation rate,but also control construction costs.2.The heat storage device with phase change material can improve the heat storage capacity of the water tank under different working conditions.The phase change hot water storage tank with annular phase change arrangement has better heat storage effect.The hot water storage tank using the combination of three phase change materials can adjust the heat release process of the water tank,and it achieves the purpose of slowly releasing heat.Compared with the pure water tank,the mixed phase change combinationⅡmakes the water tank reach 50℃to extend 570 min.CombinationⅢincreases heat storage 251.2 KJ and makes the water tank reach 40℃to extend 690 min.Combination I is between the other two combinations.3.Optimize the water tank structure according to the actual heat storage device heat dissipation model.The greenhouse water tank should be designed such that the ratio of height to bottom diameter is 1:1,and the volume is 6-10 m3.Establish a calculation model for the actual heat storage of the water tank,the size of the water tank and the phase change filling volume.The heat storage device configuration is calculated according to the actual heat load of the two greenhouses in Yangling.When the temperature is increased by 5℃in the greenhouse,the phase-change heat storage medium accounts for 16.67%of the total volume of the heat storage device:The theoretical total volume of the heat storage device that needs to be configured in the large-span solar greenhouse is 6.88 m3;The theoretical total volume of the thermal storage device that needs to be configured in the traditional solar greenhouse is5.89 m3. |
