Technique and human perception of intermittent air velocity variation

Härtill 6 uppsatser Diss. (sammanfattning) Stockholm : Kungliga Tekniska högskolan, 2005 Teknologie doktorsexamen Objectives. The main objective of the present thesis was to evolve a controlled intermittent velocity field and to examine the impact of this type of dynamic indoor climate on human’s psychology and physiology. The prediction was that intermittent velocity variation could provide occupants with the desired cooling without causing draught and that this intermittent change of the indoor climate would influence peoples’ affect and cognitive performance. Methods. All experiments were performed in a classroom-like environment where groups of subjects were exposed to a temperature increase and step changes in air velocity. The changes or intermittent variations in air velocity consisted of elevated speed during five minutes, which were repeated three times. To reduce the influence of individual thermal preferences all measures were collected twice and the statistical analyses were based on the change scores in these measures. Results. The obtained results showed that, intermittent velocity variation may provide occupants with the desired cooling without causing draught. Subjects exposed to velocity variations were significantly less affected by the temperature rise in the room, compared to the control group. Moreover, the method reduced the expected increase of occupants who perceived the temperature condition as uncomfortable. The findings concerning air movements demonstrate that very few perceived the condition as draughty, after being exposed to the three high velocity pulses. The results concerning affect showed a significant effect on high activation, in the temperature range 21 - 24 o C when the velocity variations made the subjects rate the temperature as slightly lowered over time, they kept their level of activation. In the higher temperature interval, 25 - 27 o C, unactivated unpleasantness increased and activated pleasantness decreased significantly more in subjects in the constant velocity condition than it did for subjects in the velocity variation condition. In sum, all results concerning affect, the significant ones and tendencies point in the same direction. Subjects exposed to velocity variation report changes, over time, indicating higher activation and more positive feelings. No differences in cognitive performances were shown between the air velocity conditions. However, a tendency to a significant result (p = 0.10) in an attenti