Physical modelling of natural ventilation through screens and windows in greenhouses

Abstract

An experimental and theoretical study of air exchange through porous screens and window openings in greenhouses was conducted in order to characterize the influence of the resistance of porous screens and window openings on airlow and to characterize wind velocities and air temperature differences which derive these flows. Fluctuations in wind velocity were related to the mean wind velocity through a parameter which is evaluated based on a power spectrum analysis. In turn, wind pressure was related to this mean wind velocity such that the turbulence was taken into account. The relationship between air exchange through porous screens or window openings and the driving potential was studied based on an approach derived from fluid mechanics. The predictions made of airflow versus wind pressure and temperature differences agree reasonably well with experimental data, differences between them being less than 20%, in general.