Multi-indicator evaluation on ventilation effectiveness of three ventilation methods: An experimental study

Enhancing ventilation effectiveness can improve indoor air quality (IAQ). Both contaminant removal effectiveness (CRE) and air change effectiveness (ACE) are widely used to evaluate ventilation effectiveness. They reflect two different aspects of IAQ, and an analysis based exclusively on ACE or CRE has important limitations. Firstly, this study is to evaluate the overall IAQ integrating ACE and CRE by using multi-indicator methods. Secondly, this study is to find out an indicator to best characterize the overall IAQ. Twenty-four experiments with different combinations of three ventilation methods (i.e. mixing ventilation (MV), displacement ventilation (DV) and stratum ventilation (SV)), four air exchange rates and two point pollutant source locations are conducted in a simulated office. Three multi-indicator methods are applied and compared, including Z-score method, Rank Sum Ratio method, and Technique for order preference by similarity to an ideal solution (TOPSIS). The results show that, for ACE, in the occupied zone, DV performs best with the values of 0.76–0.84; in the breathing zone, SV performs best with the values of 1.21–1.35. For the overall IAQ, in the occupied zone, DV performs best (ranking in the top 4–33%), followed by SV (ranking in the top 38–92%), and then MV (ranking in the top 50–100%); in the breathing zone, SV performs best (ranking in the top 8–54%), followed by DV (ranking in the top 4–79%), and then MV (ranking in the top 58–100%). All the three evaluation methods indicate that CRE is more representative than ACE for measuring overall IAQ.