Performance evaluation of filter applications in fan-coil units during the 2015 Southeast Asian haze episode

Abstract

Fan-coil units (FCUs) see wide applications in buildings but few are integrated with high-quality filters for efficient particle removal. Driven by an attempt to protect the indoor space served by FCUs from elevated outdoor PM concentrations (e.g. periodic haze events in Southeast Asia), four different grades of filters (dust-spot efficiencies of 25%, 65%, 85% and 95%, denoted as F25, F65. F85, and F95 hereafter) were installed inside the cassette FCUs respectively in four similar rooms. Air exchange was controlled by the recirculation fans in FCUs and exfiltration via door gaps. Performance of the filters was evaluated through continuous monitoring of particle number concentrations. Energy consumption and noise levels were also recorded via field measurements. The overall particle removal efficiencies (via filter-integrated FCUs) generally increased with higher filter grades; however, F95 didn't provide a significant improvement over F85. Upgrading from F25 to F85 or F95 decreased the size-resolved particle I/O ratios significantly (from 0.19 to 0.65 to 0.06–0.24 depending on the particle sizes). Installation of F85 or F95 alone was not sufficient to reduce the indoor PM2.5 concentrations to the WHO guideline of 25 μg m−3 under moderate and heavy haze scenarios. F85 resulted in the lowest energy consumption in terms of chilled water energy and FCU electricity combined. F95 application led to the highest noise level at ∼46.6 dBA. The study advances the knowledge of particle attenuation effects by the FCU with different grades of filters and provides a basis for filter selection against compromised outdoor conditions in similar settings.