Different Wall Structures Actively Store Heat And Humidity Of Solar Greenhouse Performance Analysis

In the development of solar greenhouse in recent years,the prefabricated solar greenhouse has the advantages of fast forming and short construction period.However,how to optimize the structure and back wall materials of the prefabricated solar greenhouse to improve the thermal insulation and heat storage performance of the greenhouse needs to be further tested and explored.In this study,three assembled modular solar greenhouses were tested,namely,assembled gravel module greenhouse(A),assembled water module greenhouse(B),and assembled earth module greenhouse(C).The local traditional brick and concrete wall greenhouse(D)was used as a control.An integrated active heat storage circulation system is set up in the test greenhouse.The thermal and humidity characteristics of the greenhouse are analyzed and the thermal performance of the integrated active heat storage circulation system is calculated.Finally,the integrated active heat storage circulation system is optimized by combining with the test,and the theoretical demonstration is carried out.The main results are as follows:(1)Firstly,through the calculation and comparison of the thermal performance of the back wall of the test greenhouse,it is concluded that the specific heat capacity of the thermal storage layer material and the total thermal resistance of the wall of the back wall of the test greenhouse A,B and C are the largest in greenhouse B,followed by greenhouse C,and greenhouse A is relatively small.The total thermal inertia index,wall delay time and attenuation multiple of test greenhouse B are all greater than those of greenhouse A and C,that is,the heat storage and insulation performance of the back wall of greenhouse B is better than that of greenhouse A and C,and it has better thermal stability.(2)Through the comparison of indoor and outdoor temperature between the test greenhouse and the control greenhouse under typical weather conditions,the average daily temperature of test greenhouse A,B and C was higher than that of control greenhouse D.The test and comparison results of the whole month show that the indoor temperature of test greenhouse A,B and C is better than that of control greenhouse D.The temperature of greenhouse B is the best,followed by greenhouse C,greenhouse A is relatively low,that is,greenhouse B has better heat storage and insulation performance.(3)The comparison results of temperature test on the wall at different depths are as follows: Under different typical weather conditions,the temperature of the water sac in the wall of greenhouse B is slightly lower at the depth of 20 cm near the top of the tank.Under sunny conditions,the thickness of the wall heat storage layer of Greenhouse C is 600～700mm,and more than 700 mm is the stable layer.Under cloudy conditions,the thickness of the heat storage layer is 300～400 mm,and more than 400 mm is the stable layer.In typical weather,the heat storage layer thickness of greenhouse A is greater than 600 mm.The temperature variation trend of underground soil in the three test greenhouses was the same,because the temperature gradually decreased from the soil surface to the depth of 40 cm.The temperature of underground soil in greenhouse B was better than that in greenhouse A and C.(4)The differences of the three test greenhouses in the performance of active heat storage and release are as follows: under sunny conditions,daytime or night operation of the fan can improve the thermal environment of the greenhouse,and save more costs than all-day operation.The fan running at night can increase the night temperature of the greenhouse under cloudy conditions.No matter what kind of weather conditions,the energy efficiency ratio of heat storage stage and heat release stage of greenhouse B system is greater than that of greenhouse A and C,indicating that the system has better energy-saving effect when operating in greenhouse B.(5)Calculate and analyze the ratio of active heat storage,heat release and energy efficiency of the optimized active heat storage circulation system(NS for short)under different operating conditions,and compare the differences with the pre-optimized active heat storage circulation system(OS for short).Under any weather conditions,the ratio of heat storage,heat release and energy efficiency of NS in the heat storage stage and heat release stage is far greater than that of OS.It can be concluded that the heat transfer performance of the optimized active heat storage circulation system NS is better than that of the pre-optimized system OS,so the optimization design theory of the NS active heat storage circulation system is feasible.In summary,the thermal performance of the three test greenhouses A,B and C is better than that of the control greenhouse D,and the heat preservation and storage performance of test greenhouse B is better than that of greenhouse A and C.The integrated heat storage circulation system can store and release more heat under more reasonable operating conditions,and improve the temperature in the greenhouse.The design optimization of active heat storage circulation system is carried out,and the feasibility of the optimized design scheme is proved by theoretical demonstration.Therefore,the modular assembly solar greenhouse and integrated active heat storage circulation system have good practical value for the winter production of crops,and can be popularized and applied in a certain area.