Washing the air: enhanced condensation of water on aerosols to enable their removal

Abstract

Previous theory (Clement 1985 Proc. R. Soc. A 398 , 307–339.) is applied to calculate water vapour condensation on aerosol in a chamber with a hot water base, a cooled roof and insulated walls. The fractional aerosol condensation of the water vapour is given by the surface condensation numbers, Cn , at the water surface and the roof. The magnitude of the aerosol condensation rate, M , per unit area of the base is then obtained from theory using heat transfer correlations. The central well-mixed turbulent region in the chamber is generally equilibrated, and maximum and minimum values of M are obtained from the limits of complete vapour condensation, and no condensation, in the boundary layers, respectively. Practically all their difference arises in the cold boundary layer where the supersaturation reaches up to 3 for no condensation. Results for M are obtained for water temperatures of 70 and 80°C and roof temperatures of 5–30°C, and range from 0.1 to 1.0 g m −2  s −1 . Chamber properties are compared to those of the Pi chamber used to investigate cloud condensation. Estimations for aerosol growth in the chamber are made for varying chamber heights and aerosol number concentrations, N . Passage of air through such a chamber could effectively grow aerosols of even the highest N up to an easily removable size range in a matter of seconds, enabling the cleaning of polluted air, including that containing viruses.