|Authors: ||R. Gil, C.R. Bojaca, H. Casilimas, E. Schrevens, R. Suay|
|Keywords: ||CFD modeling, natural ventilation, airflow pattern|
In recent years many scientists have proved the existence of important temperature gradients associated to airflow variations inside greenhouses.
Under tropical conditions, greenhouses are ventilated through side and roof vents that are operated manually; and suffer from important temperature gradients.
The aim of this study was to analyze different ventilation configurations in order to maximize climate homogeneity inside the greenhouse.
This was carried out by evaluating different side and roof vents opening configurations, through the application of computational fluid dynamics (CFD) methods.
A five span greenhouse model (7 m height and 40 m width) was placed in the center of a 2D (height×width) computational domain of 20×240 m2. The greenhouse was equipped with five continuous ridge vents of fixed aperture, two continuous gutter to ridge roll-up vents (spans two and four), and two continuous lateral roll-up vents.
Six configurations combining the opening or closing of the sidewall and roof vents (fixed and roll-up) were evaluated.
The Navier-Stockes equations were solved using the software Fluent 6.3, for a standardized constant inlet velocity profile of 1 m s-1. The airflow pattern was evaluated by means of wind velocity across the horizontal profiles (1.5 m above the surface). The most widespread configuration of fixed ridge vents and sidewall vents fully opened showed an average wind speed of 0.70±0.21 m s-1. The proposed configuration of fully opened vents, including gutter to ridge roll-up ones, improved overall ventilation and got the highest average wind speed (0.77±0.25 m s-1), thus highlighting the importance of such new vents.
The other configurations considered did not show any improvement of the natural ventilation, but differences in airflow homogeneity were observed.
Areas located far away from the vents presented the lowest air velocities and consequently may explain high temperature spots.
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