Local discomfort caused by draft perception in a space served by displacement ventilation system in the tropics

This paper reports a subjective study in a field environmental chamber (FEC) served by a displacement ventilation (DV) system. Sixty tropically acclimatised subjects, 30 males and 30 females, were engaged in sedentary office work for 3 h. The subjects were exposed to three vertical air temperature gradients (nominally 1, 3 and 5K center dot m(-1)) between 0.1 and 1.1 m heights and three room air temperatures (20, 23 and 26 degrees C) at 0.6 m height. The object of this work was to investigate effects of temperature gradient and room air temperature on local discomfort due to air movement at different thermal sensations. The results indicated that vertical temperature gradient had an insignificant impact on draft perception. Draft perceptions at foot, calf, thigh and arm were affected by both overall and local thermal sensations. A cold sensation would increase the risk of draft complaints and a warm sensation would increase the percentage dissatisfied due to insufficient air movement.