Analysis of passive downdraught evaporative cooling windcatcher for greenhouses in hot climatic conditions: Parametric study and impact of neighbouring structures

Abstract

In hot climates, greenhouse cooling is essential to provide crops with suitable growth conditions. The combination of natural ventilation strategy such as windcatchers and evaporative cooling has the capability to decrease the energy requirement of greenhouses and provide improved conditions for the cultivation of crops. Although the windcatcher is a traditional architectural feature which originated in the Middle East, it has recently gained more attention and is increasingly being employed in buildings as a wind-driven cooling technique. This study aims to investigate the potential of a passive windcatcher and evaporative cooling system integrated into a greenhouse using computational fluid dynamics (CFD), validated with experimental data. Different wind speeds (1.96, 3.03, 4.87 and 6.07 m s−1) and ambient temperatures (30, 35, 40, 45 °C) and relative humidity (15, 25, 35 and 45%) were considered. The average error between measured and simulated results was 5.43% for the cross-flow ventilated greenhouse model and 4.55% for the evaporative cooling spray model. The results showed that the system could reduce the average indoor air temperature by up to 17.13 °C. The study explored the influence of different windcatcher heights and also the potential of fins installed in the windward openings to improve the uniformity of the ventilation airflow. The study also assessed the influence of neighbouring structures or other greenhouses on the ventilation performance. The results showed that the windcatcher provided higher airflow rates as compared to side openings when other structures surrounded the greenhouse.