Experimental Study of Film Condensation in a Rotating Paper Drum With a Scraper-Thick Film Case

Heat transfer in film condensation on the inside wall of a horizontally rotating paper drum with a scraper is studied experimentally. Four distinct heat transfer and/or hydrodynamic regions were observed: a laminar and gravitational flow of the condensate at low rotational Reynolds number, characterized by the appearance of accumulation, with unsteady heat transfer and hydrodynamic phenomena; a non-boundary layer region, characterized by the bore, with increasing heat transfer coefficients with increasing rotational Reynolds number; a filmlike region with the appearance of ripple, with slightly increasing heat transfer coefficients with increasing rotational Reynolds number; a rim film region without obvious wave because of the strong damping by centrifugal force, with slightly increasing then decreasing heat transfer coefficients with increasing rotational Reynolds number. The decrease of residual film thickness results in a slightly increase of heat transfer coefficients. The transport mechanism in every region is analyzed, and a comparison is made between the experiments and theory of solid film.