Effect Of Wind Deflector On Environmental Factors In Soalr Greenhouse And Structure Optimization Of Wind Deflector

The crop near the vent in a solar greenhouse which is located in cold arid areas will become undesirable growth or even be death because of the cold wind. An wind deflector is set usually near the vent to resist the damage of the cold wind. Two greenhouses in normal production respectively characterized by ordinary(control group) and wind deflector (experimental greenhouse) are studied by testing their internal temperature continuously. Temperature and air velocity differences between experimental and control group greenhouses are explored through numerical simulation. The size of areas cultivated crops which average temperature below 20℃ is regared as evaluation index, it changes with the variation of wind deflector structure parameters in CFD modle under different velocity inlet. According to nonlinear curve fitting for evaluation index, best structure parameter of wind deflector is determined.Eleven observation points of air temperature are fixed up in the experimental and control group greenhouses. Two observation points are respectively fixed up in the centre of east and west wall. Three observation points along the span direction on topsoil are fixed to test soil surface temperatures. One temperature observation and a wind velocity observation are fixed near the vent. An automatic meteorological station was used to monitor the climate around greenhouses. Numerical models based on CFD method el these two types of greenhouses in natural ventilation are built. Computed zones included the whole interspace. Steady model was used and viscous model is standard k-epsilon; using discrete ordinates describe the radiation model; natural convection driven by buoyancy is fit for boussinesq assumption; the gravity is considered in operating conditions. Boundary conditions are determined by the data measured on January 15 2015.It is concluded that in the areas cultivated crops, air temperature in experimental greenhouse is higher than it in control group greenhouse. The maximum of temperature difference between the two greenhouses are 4.2℃ while the minimum is 1℃. Airflow becomes circumfluence clockwise in experimental greenhouse, while it becomes circumfluence anticlockwise in control group greenhouse. The best windward length is 0.84m and the best oblique angle is 76° in order to ensure the land surface temperature of most arable zones are higher than 20℃ under condition of natural ventilation when the vent is 0.3m wide and the bottom is 0.25m high.