Experimental investigation of thermal comfort with stratum ventilation using a pulsating air supply

Abstract

This study proposes an innovative ventilation strategy combining stratum ventilation with a pulsating air supply to improve thermal comfort. The experiments were conducted in a classroom with two rows of seated occupants. Four cases of pulsating air supply conditions were designed, including different combinations of room air temperatures (27 and 28 °C), supply airflow rates (7.9 and 9.0 air changes per hour), and pulsed cycle durations (2 and 5 min). One case with a constant air supply was also considered for comparison. Air velocity and temperature distributions in the occupied zone were measured, and subjective responses to the thermal environments were collected. Twenty-five subjects were recruited for the subjective investigations, and these subjects performed sedentary work and wore summer clothing with a typical thermal insulation of 0.49 clo. Results showed that with the pulsating air supply, more than 87% of subjects reported thermally comfortable, and the thermal environments satisfied the requirements in ISO 7730 up to Category A. Compared to the conventional constant air supply, the pulsating air supply provided comparable thermal sensation in the two rows, decreased the percentage dissatisfied due to draft from 34% to 8%, and decreased the percentage reporting thermal discomfort from 16% to 4%. These improvements reflect the benefits of the dynamic airflows in the occupied zone created by the pulsating air supply. The time-averaged predicted mean vote (PMV) and predicted percentage dissatisfied (PPD) were demonstrated to be applicable for the dynamic thermal environment created by the proposed stratum ventilation with a pulsating air supply.