Numerical Simulation Of North Wall Structure And Temperature Condition Of Chinese Solar Greenhouse

The rear wall of solar greenhouse is not only the load-bearing carrier,but also the most important thermal insulation and heat storage structure.There are many materials for building solar greenhouse wall,and the thickness varies depending on the temperature conditions in different regions.To study the material and structure of the wall building for a solar greenhouse in a certain area,it is often necessary to build a greenhouse with different walls and conduct at least one year of actual environmental parameter measurement to obtain more accurate results.This research method not only takes a long time,but also difficult to measure the performance of the greenhouse under various meteorological conditions.Moreover,it is impractical to construct multiple solar greenhouses with various types of walls and make them function normally.In this paper,the thermal characteristics of solar greenhouse rear walls using clay bricks,fly ash bricks and perforated bricks of slabs and benzene boards are applied in the Shenyang area through numerical simulation of computational fluid dynamics(CFD)simulation.The CFD analysis method was used to simulate the greenhouse temperature field and airflow field,and a three-dimensional mathematical model with different wall thicknesses and building materials was constructed.The experiment compares the numerically simulated air temperature in the solar greenhouse and the temperature inside the rear wall with the experimentally measured values.The results are in good agreement,which provides a reference for the numerical simulation study and verifies the feasibility of the CFD numerical simulation method.The results are as follows: the clay brick rear wall thickness of solar greenhouse in Shenyang increased significantly from 170 mm to 370 mm,and the greenhouse warming effect was remarkable,the effect decreased when it increased to 570 mm.Under the premise of ensuring high thermal insulation and heat storage capacity,the construction cost was saved as much as possible,and the rear wall thickness was 370 mm.Among the commonly used clay bricks,fly ash bricks and porous bricks,porous bricks had the fastest thermal conductivity and the least heat storage.The thermal characteristics of clay bricks and fly ash bricks were not much different.However,the actual application results showed that these three walls had little effect on the night temperature of the solar greenhouse.Clockwise air vortex would be formed in the solar greenhouse at night under confined conditions.The air velocity at the edge of the vortex near the shed membrane and the surface of the soil was the largest(0.235m/s),and the air velocity near the center of the vortex was low.In the first half of the night,the vortex center was near the ground at the front foot of the solar greenhouse.Later in the night,it gradually moved back and rose.Before dawn,it moved below the roof to about 2/3 height from the ground.The air vortex will cause low temperature areas inside the crop group,and it is necessary to use internal insulation to cover the airflow movement.The air vortex will cause low temperature areas inside the crop group,and it is necessary to use internal insulation to cover the airflow movement.