The Effect of Air Velocity on Thermal Comfort

Abstract

Experiment 1 investigated oscillating vs fixed fans. Eight males were exposed to seven conditions in each of three temperatures (25.6, 27.8, and 30 C (78, 82, 86 F); all at 50% rh). The seven conditions were: still air, velocity of 0.4, 0.8 and 1.2 m/s from a fixed fan, and mean velocity of 0.3, 0.5, and 0.7 m/s from an oscillating fan. For equal comfort, for every increase of mean air velocity of 0.1 m/s (between 0.4 and 1.2 m/s), environmental temperature can be increased by .27 C for the oscillating fan and by 0.40 C for the fixed fan. At the same mean velocity, oscillating fans are voted more comfortable than fixed fans. Experiment 2 investigated the effect of a small directional axial-flow desk fan on comfort at 26.1 C (79 F). The 16 females tested fan off vs a 1.5 m/s flow on all six combinations of: torso vs face impact of air stream, and impact from straight ahead, 30° to the right, and 60° to the right. Angle was not significant. The use of the fan was equivalent to a decrease of air temperature of 0.63 C (i.e., 0.1 m/s = 0.042 C). Thus the personal desk fan can be used as a “fine tuner” in an acceptable environment. Those wearing glasses preferred air on the face, those wearing contacts preferred the torso; those wearing neither were divided. Thus fan placement should be left to the individual.