Effect of preferable wind directions on personal thermal comfort of occupants in the air-conditioned office in hot-humid climate

Abstract

The utilization of a desk fan in the personal thermal comfort (PTC) method is a thermal adaptation that provides indoor comfort and energy-saving for office applications due to the high energy consumption of ACs in the HVAC sector. Researchers have conducted numerous studies on this utilization. However, the question of which wind direction provides thermal comfort for respondents remains an issue, along with the effect of different wind directions on thermal comfort and its influence on skin temperature. Field measurements were conducted inside an air-conditioned office room at a set point temperature of 29.0 °C, involving 400 questionnaire samples from 20 respondents. There were three stages of desk fan configurations; Stage 1 No-fan, Stage 2 Single fan, and Stage 3 Dual fan configurations. The result showed that most respondents preferred wind direction from front and head. Meanwhile, left and right were least favoured. Different wind directions from fans successfully lowered the heat sensation perceived by respondents up to 53% compared to the no-fan configuration. It improved the overall comfort from slightly uncomfortable to moderately comfortable, on a scale of 3.5 to 2.4, under the indoor temperature of 28.6 °C. Respondents' initial average skin temperature during no-fan configuration, ranging from 33.9 to 35.4 °C, was lowered during fan configurations, recorded at 33.2–34.5 °C. PTC setup used in the study also provides lower energy consumption, ranging from 8-20%, compared to low AC set point temperatures of 20.0 and 24.0°C commonly used in hot and humid tropical countries.