Analysis of the influence of selected factors on natural greenhouse ventilation

Abstract

In greenhouses, in order to maintain proper indoor air temperature, during the period of high values of solar radiation intensity, shading treatments using thermal screens and ventilation are applied. The research was carried out in a mono-span greenhouse in order to determine the effectiveness of natural ventilation. The object of analysis is a greenhouse with a thermal screen installed inside. The tests were carried out during the summer days. The effect of the research was to determine the ventilation air flow through the vents of the greenhouse on the basis of measurements and calculation analyzes. The dependence of the air flow on the windward and leeward side was determined from the wind speed and the temperature difference between the indoor and outdoor air. On the basis of calculations made from observation during shading of the cultivated area and with open ventilators, the coefficients of air exchange per unit floor area of the greenhouse were determined. It was established that at a wind speed exceeding 0.8 m/s, the air exchange rate in the tested greenhouse exceeds the value recommended by the American Society of Agricultural Engineers of 0.04 m3/(s.m2).