Greenhouse ventilation rates through combined roof and side openings: An experimental study

Abstract

A simple statistical relation between the ventilation rate of a greenhouse and its roof and side openings was proposed and tested on experimental data. This relation combines thermal buoyancy and wind effects as driving forces of the natural ventilation. It is shown that both effects are dependent on the total area of openings. The wind effect is related to a global wind-dependence coefficient. In our experimental conditions the wind effect predominates over the chimney effect when the ratio of wind velocity to the square root of air temperature difference becomes greater than 1. The comparison between the combined roof and side ventilation system and the roof alone system shows that for typical conditions of temperature difference (=5 K), the first ventilation system is more efficient than the second for wind velocities smaller than 2.5 ms-1 because of the significant role of the chimney effect.