Draught perception in intermittent ventilation at neutral room temperature: Fid-Bau Portal

Draught perception in intermittent ventilation at neutral room temperature

Tawackolian, K. / Lichtner, E. / Kriegel, M.

Abstract This study questions the extent which steady-state calculation methods for the draught rate according to ISO 7730 are applicable to intermittent ventilation, especially with pulse durations shorter than 30 s. 37 subjects were exposed to intermittent ventilation in a cooling scenario at neutral room temperature, i.e.in an ambient that was neither warm nor cool. Two displacement air diffusers supplied the air alternatingly, 50% of the time from each side. The operation profile of each diffuser thus corresponded to a square waveform. The diffuser supply air temperature was at 19 °C while the room temperature was controlled to thermally neutral conditions at 22 °C. Two subjects sat directly in front of large air diffusers and were therefore located in the core region of a free jet with the cool air blowing from behind. The subjects were asked to evaluate their thermal comfort for nine conditions with air velocities between 0.2 ms⁻¹ ^and0.6 ms⁻¹ and pulse durations between 10 s and 30 s. In intermittent ventilation, the discomfort was higher than in steady ventilation at the same maximum velocity. Draught perception increased with increasing velocity and with increasing pulse duration. Due to the enhanced mixing with ambient air in intermittent ventilation, the average air temperature 25 cm in front of the diffusers could be increased by 0.5 K.