Human Response to Personalized Ventilation Combined with Chilled Ceiling

Personalized ventilation (PV) improves inhaled air quality, because it provides fresh air to each workstation and directly to occupant’s breathing zone. Previous research was focused on combining PV with additional total volume air distribution, i.e. mixing ventilation or displacement ventilation, which was responsible for keeping the design air temperature conditions in the occupied zone.

Removing room sensible heat load with radiant cooling systems enables reduction of required supply airflow rates which can make it possible to use the PV as a single ventilation system in the room. Furthermore, the use of radiant ceiling cooling will provide operative temperature lower than the air temperature and will improve further occupants’ thermal comfort at warm environment.

Therefore combining PV with chilled ceiling may be an effective way to provide thermal comfort in rooms at temperature higher than the recommended in the standards upper temperature limit of 26°C. In this paper response of 24 human subjects to a PV combined with chilled ceiling system (CCPV) is compared with the response to mixing ventilation combined with chilled ceiling (CCMV).

Participants were provided with control of direction and flow rate of the air supplied from the PV. Air quality and thermal comfort perceived by subjects were studied during 3-h. exposures. Room air temperature was kept at 26°C and 28°C. Supplied air temperature (by PV and mixing ventilation) was 3 K lower than room air temperature.

Average supply/return water temperature for chilled ceiling was 15,5/16,8°C at room air temperature of 26°C and 19,5/20,6°C at 28°C. During the experiment the subjects were performing typical office tasks at workstations with computers. Exposure included also increased activity level office work for a period of 25 min.

At the workstation PV provided overall thermal sensation close to neutral, whereas thermal sensation above neutral was reported during the exposure with CCMV. In the room away from the workstations the thermal sensation and its’ acceptability was similar with both systems. Immediately after the increased activity period subjects’ thermal sensation ranged between warm and hot.

After returning to the workstations the use of PV helped subjects to improve their thermal sensation much faster (5 min) compared to the CCMV (30 min). Air at workstation was perceived as more fresh with CCPV than with CCMV. Percentage of dissatisfied with air quality was lower in the cases with CCPV system compared to CCMV.

Both studied systems created similar thermal and air quality conditions in the occupied zone outside of the workstations.