Effect of Cross-Ventilation and Solar Irradiation on IAQ as a function of Roof Angle

¹ M.Sc., Department of Mechanical Engineering, Istanbul Technical University, Istanbul, 34437, Turkey
² Ph.D., Department of Mechanical Engineering, Istanbul Technical University, Istanbul, 34437, Turkey

^* Corresponding author: atalara@itu.edu.tr

Abstract

Natural ventilation is the most conventional and one of the significant alternative applications for energy efficiency. Cross-ventilation is commonly used in hospitals, shopping centres or greenhouses. In this study, cross-ventilation for a greenhouse was investigated. The greenhouse buildings may differ in design depending on the region and climate. Therefore, when natural ventilation methodology is carried out in these buildings, the effect of solar radiation should also be taken into consideration. There have been many studies on natural ventilation in the literature, but while these studies have been conducted, the impact of solar irradiation has never been combined. In the present study computational geometry was created according to 4 different roof inclinations: 0°, 15°, 30°, and 45° - provided that the inlet and outlet opening positions are fixed. Moreover, each inclination was simulated at the following hours of the day: 10:00, 13:00 and 16:00 in June. The hex-dominant grid was created for a computational domain using Cut-cell method and Renormalization-group (RNG) k-ε turbulence model provides the best results and efficient computational cost. In addition to this, Discrete Ordinates (DO) radiation model with SIMPLE algorithm was implemented for solar radiation effect. In order to decrease the temperature of the reference line, the evaporating cooling methodology was performed and a new PVC cover material was applied. Numerical predictions show that solar irradiance combined with roof inclination and outlet opening position has a significant effect on velocity and temperature distribution inside the building space. The air mass flow rate which aspirates from outlet increases considerably when the inclination angle is increased, also flow character changes according to configurations. Evaporative cooling creates a decrease in temperatures on the reference line up to 2 – 2.5°C when compared with the reference model.