Development of Electrostatic-Precipitator-Type Air Conditioner for Reduction of Fine Particulate Matter in Subway

Abstract

This study developed a highly efficient electrostatic precipitator (ESP) type air conditioner to reduce the particulate matter (PM) concentration in a subway station. A polyethylene terephthalate film coated carbon sheet nonmetallic electrode was used as a collection plate to reduce the weight instead of the metallic collection plate, and the carbon fiber ionizer was used to minimize the ozone generation. When the flow velocity in a duct was 1 m/s with −5.0 kV applied to the ionizer and −5.0 kV to the collection plates, the 0.3- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m PM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</sub> removal efficiency increased up to 97.47%. Holes in the collection plates were used to attach connecting tubes to maintain a constant distance. The strength and shape of the electric field were analyzed using COMSOL. The electric field quickly dissipated in the hole areas, and the field strength converged to 0. The collection plates were extended to compensate for the reduced collection area due to the holes. As a result, when the flow rate in the duct was 1 m/s, −5.0 kV was applied to the ionizer, and the electric field strength was up to −1.5 kV/mm, the PM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</sub> removal efficiency was increased to 99.08%. This behavior resembled that of conventional collection plates. The ESP developed in this study corresponds to a higher MERV13 grade than the MERV10 grade filter currently installed in the air conditioner of the subway station and has almost no pressure drop, so it is expected to contribute to the improvement of air quality and energy efficiency of subway stations.