Experimental investigation of the effects of inlet cooling air temperature on the occupants’ local thermal sensation in the under-floor air distribution system

In recent years, the applications of under-floor air distribution (UFAD) systems have commonly increased for ventilation of office buildings. In the present study, the effects of inlet cooling air temperature from the diffusers of under-floor air distribution system have been experimentally investigated on the occupants’ local thermal sensation. In the experiments, the inlet air temperature is controlled at 12°C, 16°C and 20°C, and the inlet velocity is kept constant. Also, the room thermal conditions have been controlled at the mean temperature of 24±0.5°C and mean relative humidity of 25±2%. During the experiment, 8 healthy male subjects with common office clothing and metabolic rate were exposed to an under-floor air distribution system for 30 min and their thermal sensation and satisfaction were assessed on the basis of thermal comfort standards. Based on the results, the head and chest thermal sensations are not significantly depended on inlet temperature. But, by decreasing the inlet temperature, the thermal sensation and satisfaction of hands and feet are decreased. Moreover, the results indicated that the overall body thermal sensation is significantly depended on the sensation of the body parts with extreme thermal conditions. Also, the results show that the feeling of air movement can be increased during the time; so, the subjects reported about 75% draught discomfort after 30 min exposure to UFAD system.