Enhancement of thermal comfort in a large space building

Abstract

Many large confined spaces in tropical countries employ a combination of natural ventilation and mechanical fans for space cooling purposes. However, due to low wind velocity and an inability of mechanical fans to remove warm air, this cooling method is not capable of providing a satisfactory thermal comfort to the occupants. This study aims to find out a simple strategy for improving the thermal comfort inside a mosque building in Malaysia. Field measurements were first carried out to acquire the airflow velocity, air temperature, relative humidity and mean radiant temperature inside the mosque, for a duration of one-year. These data were then used to calculate two thermal comfort indices namely predicted mean vote (PMV) and predicted the percentage of dissatisfied (PPD). A computational fluid dynamic (CFD) method was employed to predict airflow and temperature distributions and to examine the effects of installing exhaust fans on the thermal comfort condition inside the mosque. Parametric flow analyses were conducted to find out the arrangement of the exhaust fans that would produce highest improvement in the PMV and PPD thermal comfort indices. It was found that, under the present ventilation condition, both PMV and PPD values at the selected locations inside the mosque exceed the respective upper limits as recommended in the ASHRAE Standard-55, indicating that the thermal comfort inside the mosque is extremely hot. Results of parametric flow analyses show that installing ten exhaust fans with a 1-m diameter at the south-side wall, at the height of 6 m from the floor, has a potential of reducing the PMV index by 75–95% and the PPD index by 87–91%. This translates into a vast improvement in the thermal comfort inside the mosque building.