Effects of temperature, air movement and initial metabolic rate on thermal sensation during transient state in the tropics

The effects of temperature, air movement and initial metabolic rate on transient thermal sensation at warm temperatures and high humidity among tropically acclimatized people were investigated. 26 tropically acclimatized subjects (13 males and 13 females) participated in the experiments with two different initial metabolic rates at temperatures of 24, 27 and 30 degrees C, relative humidity (RH) of 60% and air velocities ranging from 0.07 to 1.87 m/s. All the subjects participated in 18 sessions, each for 3.5 h. Thermal sensation in the first few minutes after entering the room moderated earlier with elevated air movement. Thermal sensation, thermal comfort and thermal acceptability reached steady-state within 15 and 25 min respectively at 27 and 30 degrees C with elevated air movement up to 1.87 m/s even at high initial metabolic rates. Air movement, temperature and initial metabolic rate had a great impact on immediate change in thermal sensation, comfort and acceptability after entry into an air-conditioned room from an outdoor environment. Thermal comfort was highly correlated with thermal sensation during the transient phase and it was observed that a much cooler thermal sensation than in steady-state was necessary for optimal thermal comfort during the transient state. When the initial metabolic rate decreased, the preferred thermal sensation for tropically acclimatized people showed a noticeable shift from cool (-1.87) to slightly cool (- 0.77).