Acceptance of thermal conditions and energy use of three ventilation strategies with six exhaust configurations for the classroom

The paper describes an experimental study from forty-eight subjects about the acceptable thermal conditions under three ventilation strategies with six exhaust configurations, including mixing ventilation (MV), displacement ventilation (DV), and four exhaust types of stratum ventilation (ceiling-level-exhausted “SV”, rear-low-level-exhausted “SV-1”, front-low-level-exhausted “SV-2” & rear-middle-level-exhausted “SV-3”) serving a confined 8.8 m × 5.1 m × 2.4 m (h) classroom. Tests were carried out in a specially constructed test chamber designed to represent a typical small-medium sized classroom in Hong Kong. Thermal comfort analyses were carried out under specific supply flow rates, room temperatures, and air speeds in three ventilation strategies with six exhaust configurations. From the collected data, SV at 26 °C & 10 ACH and SV-3 at 28 °C & 15 ACH are achieved 100% of acceptable vote, the highest percentage of 97.3%, scoring neutral (0), are under the SV-3 at 28 °C & 10 ACH. The thermal satisfaction acceptance percentage in stratum ventilation strategies can be improved by increasing the air flow supply from 10 to 15 ACH at the elevated indoor condition of 26.8 °C, 27.3 °C and 26.4 °C by SV, SV-1 and SV-3 respectively, but not under MV, DV and SV-2. It implies that the thermal comfort will be affected no only by the temperature and air supply flow, but also by difference ventilation strategies in this study of three ventilation strategies with six exhaust configurations. This result indicates that SV-3 can satisfy human perception of comfort with least value of energy consumption, due to higher neutral temperature in comparison with the other ventilation strategies.