Effects of Air Velocity on Thermal Comfort in Hot and Humid Climate

A subjective experiment was conducted to investigate the effects of high air velocity on thermal comfort. A total of 128 college-age students (64 males, 64 females) were asked to participate in the research work. Experiments were conducted in the environmental chamber at Chulalongkorn University from April to December 2002. The scope of the experiments were limited to the most common application where the subjects wore normal working dress and do office work. The study shows that Fanger's PMV Model [1] cannot correctly predict thermal sensation at high air velocity. A modified SET* for this experiment was determined and used as an environmental index in this study. This modified SET* provides an excellent fit to a large group of thermal sensation votes form the experiment. The study shows that a range of design air velocities, where most people (80 % or more) can aacept is between a modified SET*=23.0 to 26.3 C, and the best value where subjects give the highest percentage of satisfaction is at modified SET*=24.3 C. Results from air velocity sensation and preference vote indicated that 80% of the subjects were satisfied and felt NOT DRAUGHTY and NOT DISTURBED if air velocity was not greater than approximately 0.9 m/s. Air velocity greater than 0.9 m/s was acceptable only in situations where there were no other choices and the subjects were working under no stress conditions.