Analysis of the role of sidewall vents on buoyancy-driven natural ventilation in parral-type greenhouses with and without insect screens using computational fluid dynamics

摘要: Computational fluid dynamics (CFD) was used to study the effect of greenhouse sidewall vents on buoyancy-driven natural ventilation, which is most difficult situation for cooling. A CFD model validated and then compare roof ventilation with combined vents. The effects distance between opposing presence anti-insect screens were investigated quantified. In a 20 span 152 m sidewalls, combining gave rate per unit ground area that twice only 3 22.8 m sidewalls but same vent area, seven times more obtained compared ventilation. 7 greenhouses 79% 48.3%, respectively, cross sectional had temperature difference inside outside greater than 4 °C, whereas these areas 23.4% 36.1%. latter case, hot located in centre houses. These results show that, contribution important even quite large critical small number spans. Numerical simulations an screen having porosity 25% showed air exchange reduced by 77–87%, depending size. reductions much larger those wind-driven It concluded maximise when wind speeds are low, should be used. Also, relatively narrow make better use