PERFORMANCE STUDY OF ENHANCED DISPLACEMENT VENTILATION COUPLED WITH PERSONALISED VENTILATION IN THE TROPICS

Abstract

The need for energy-efficient air distribution systems that provide satisfactory thermal comfort and air quality to all occupants in an indoor environment is becoming increasingly urgent. Non-conventional ventilation systems have begun to surface and their use popularised in the last decade. The displacement ventilation (DV) system and personalised ventilation (PV) system are two such systems that have been researched on that provide improved thermal comfort and air quality in indoor spaces. The enhanced DV (EDV) system is developed to improve the performance of DV in the tropics, however poor inhaled air quality is one major problem of this novel system. This study focuses on the performance assessment of the EDV coupled with PV in the tropics. A two-pronged approach of objective measurements and subjective evaluation by tropically acclimatised subjects is adopted. Descriptive and inferential statistical analysis was carried out using SPSS software. Repeated-measures ANOVA was performed to study if there are significant differences between the EDV standalone system and the coupled EDV-PV system at two different flow rates. Paired-samples t-test was adopted as a post-hoc analysis to compare which pair of conditions differ significantly from each other. Subsequently, mixed ANOVA was performed to analyse if there are any significant differences between the three ambient temperatures studied. Results from the objective study indicate that the EDV-PV system is able to achieve a desired temperature stratification similar to that of the conventional DV system, with improved performance through the reduction of the average temperature around the occupant. Findings from the pollutant study demonstrated that the inherent problem of poor inhaled air quality caused by the EDV system is alleviated through the coupling with PV. Compared to traditional mixing system, the EDV-PV is able to increase the amount of personalised air inhaled by occupant by up to 45%. Human response data demonstrated that tropical subjects rated the thermal and air movement acceptability of the EDV-PV system favourably at warmer ambient temperatures. The coupling of PV is able to reduce the percentage dissatisfied due to weak air movement by up to 50%. The study has demonstrated the potential applicability of EDV-PV system in the tropics, with its ability to provide enhanced thermal comfort and improved air quality at the breathing zone without energy penalty. It is suggested that future research be carried out to study a wider range of PV temperature and flow rates.