Ventilation effectiveness and contaminant distribution in an occupied space conditioned with low exergy ventilation technologies in the tropics

Abstract

Low exergy concept can be implemented in air conditioning system of the tropical buildings through a reduction of the difference between operational temperature of cooling system and indoor space whilst meeting thermal comfort requirements. Decentralized dedicated outdoor air system (DDOAS) coupled with radiant cooling system (RCS) are low exergy designs which can potentially reduce exergy destruction in cooling system of buildings while providing adequate air quality for occupants. In this study, ventilation effectiveness of a DDOAS-RCS design with floor supply – ceiling exhaust (FS-CE) and radiant ceiling panel has been investigated in an experimental setup located in Singapore. Air change efficiency (ACE) and contaminant removal effectiveness (CRE) of the designed system have been determined using tracer gas step down test under various ventilation rates. The results showed that ACE of DDOAS-RCS design with FS-CE distribution is close to that of mixing strategy and there is no significant difference for five considered ventilation rates in the range of 0.44-0.92 lit/s/m2. It was also found that each change in occupancy for the space with 70 m3 volume at ventilation rate of 0.62 lit/s/m2 takes about two hours to reach a steady state CO2 concentration and this change happens gradually throughout the space.