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.
Highlights
The natural ventilation provides energy efficiency when used in the place of conventional mechanical air conditioning methods
Winddriven cross-ventilation is used to balance fresh air distribution and it can be applied with a saw-tooth roof which performs as windcatcher because of the underpressure region behind the building, this configuration enables more air mass flow rate and more uniform and higher daylight intensity levels
The outlet, which is located in the leeward part of the building helps to extract air from indoor and there is an average gain of 22% air volume flow rate with 45° roof inclination with respect to flat roof configuration [1]
Summary
The natural ventilation provides energy efficiency when used in the place of conventional mechanical air conditioning methods. Wind-driven cross ventilation was investigated with solar heat flux and optimization research was carried out using evaporative cooling. This material can help to reject heat and reflect long wave infrared radiation (IR) [7]. In order to decrease the average temperature in the greenhouse and to ease plant growth, evaporative cooling is used as one of the alternative methods for zero energy solution. Wind-driven cross ventilation combined with solar irradiation based on optimization methods for decreasing temperature was investigated. The roles of higher absorptivity coverage material and evaporative cooling on space temperature distribution were studied for selected roof inclinations
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