Airflow visualization and performance assessment for a roof ridge ventilator under wind using Schlieren photography technique

Abstract

In Taiwan, natural ventilation devices are installed in many high-ceiling buildings, and such devices become a natural smoke vent system when a fire breaks out. The improved ridge ventilators can lead to hot air exclusion while avoiding the effect of wind. Four modes of wind were adopted to carry out the model experiments in this research. Considering that ventilators have complex and curved geometries, the Schlieren photography technique was used to effectively display the flow pattern of hot air. Thermocouples were installed to measure temperatures at each opening. The Schlieren images and temperature values indicate that the heat flowed upwards significantly when the wind was calm. When the traditional ridge ventilator was installed, the wind had an inhibitory effect on the exhaustion of hot air in an internal space. After the improved ridge ventilators were installed, the wind blew like moderate breeze, and the removal effect of hot air was improved. The experimental results indicated that heat accumulation was not obvious. However, the outside air would gush into a building when the intensity of the wind became a strong breeze. The results showed the performance of traditional and improved roof ridge ventilators in different wind fields.

Keywords

• Flow visualization
• Performance assessment
• Roof ridge ventilator
• Schlieren photography technique
• Natural smoke vent system