Effect of ventilation fan on thermal comfort in a medium size mosque

Abstract

A mosque is a place for the Muslims to perform their congregational prayers and other communal religious activities in Malaysia and other Islamic countries. Most of the mosques in Malaysia are not thermally comfortable. Thermal comfort inside a confined space is essential for health, well-being as well as productivity. A traditional method to provide thermal comfort inside the Malaysian mosque is by using natural ventilation and wall, ceiling and stand fans. However, this method is not capable of providing adequate thermal comfort due to low average wind velocity, and limitation of the fans to displace the warm air. The goal of this study is to identify ways to improve thermal comfort in a chosen mosque located in Johor Bahru. Field measurements were first carried out to determine the airflow velocity, temperature, humidity and mean radiant temperature inside the mosque. The measurements were performed from 11 a.m. to 3 p.m., in the middle of each month, for a one-year duration. Thermal comfort inside the mosque was determined by evaluating the Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD) indices. The findings showed that the PMV and PPD indices inside the mosque are outside the comfort range stipulated in the ASHRAE Standard-55. A computational fluid dynamics (CFD) method was employed to predict the distribution of airflow velocity, humidity, and air temperature inside the mosque. The CFD models were validated based on the measured airflow velocity, humidity, and air temperature. A grid independent test (GIT) was done to reduce the effects of meshing on the results while grid convergence index (GCI) was carried out to estimate the discretization error. A parametric analysis was carried out to identify a suitable number of exhaust fans and their placements that would give the greatest improvement on both the PMV and PPD values. The results showed that by placing ten exhaust fans with 1-meter diameter on the south-side wall of the prayer hall produces a more uniform airflow distribution, increases airflow velocity by 84% and decreases air temperature and humidity by 16% and 6.3%, respectively. In addition, the PMV and PPD improved by 78% and 90%, respectively. This study has shown that a proper selection of the number and placement of exhaust fans could improve thermal comfort in a large confined space.