Analysis of the influence of selected factors on natural greenhouse ventilation

Sławomir Grabarczyk,L Lichołai,A Szalacha,J Szyszka,B Dębska,J Krasoń,P Miąsik

doi:10.1051/e3sconf/20184900036

Sławomir Grabarczyk, L Lichołai + Show 5 more

Open Access

https://doi.org/10.1051/e3sconf/20184900036

Copy DOI

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).

Highlights

Greenhouse ventilation in the summer is one of the main factors affecting the formation of the microclimate
The ventilation efficiency tests carried out by Kittas et al [2] show that roof ventilators are more effective than side vents
Natural ventilation in the summer period is carried out by opening roof ventilators with dimensions of 1.47 m x 30.78 m, two vents are located on the leeward side and two on the windward side of the greenhouse

Summary

Introduction

Greenhouse ventilation in the summer is one of the main factors affecting the formation of the microclimate. In the conditions of variable external climate in Poland, in greenhouses, mainly due to costs, thermal screens are used to reduce heat losses in the period of low temperatures and to allow shading of the greenhouse's floor area during high solar radiation. It prevents the use of side vents of greenhouses in the summer. The effect of shading screens on greenhouse ventilation was investigated by Lee and Short [1]. The effect of using thermal screens can be to reduce solar radiation and temperature in the greenhouse, and to reduce ventilation and increase the temperature inside the greenhouse. The ventilation efficiency tests carried out by Kittas et al [2] show that roof ventilators are more effective than side vents

Methods

Findings

Discussion

Conclusion