title: Heat transport in bubbling turbulent convection.
abstract: Boiling is an extremely effective way to promote heat transfer from a hot surface to a liquid due to numerous mechanisms, many of which are not understood in quantitative detail. An important component of the overall process is that the buoyancy of the bubble compounds with that of the liquid to give rise to a much-enhanced natural convection. In this article, we focus specifically on this enhancement and present a numerical study of the resulting two-phase Rayleigh-Bénard convection process in a cylindrical cell with a diameter equal to its height. We make no attempt to model other aspects of the boiling process such as bubble nucleation and detachment. The cell base and top are held at temperatures above and below the boiling point of the liquid, respectively. By keeping this difference constant, we study the effect of the liquid superheat in a Rayleigh number range that, in the absence of boiling, would be between 2 × 10(6) and 5 × 10(9). We find a considerable enhancement of the heat transfer and study its dependence on the number of bubbles, the degree of superheat of the hot cell bottom, and the Rayleigh number. The increased buoyancy provided by the bubbles leads to more energetic hot plumes detaching from the cell bottom, and the strength of the circulation in the cell is significantly increased. Our results are in general agreement with recent experiments on boiling Rayleigh-Bénard convection.
authors.affiliation: Physics of Fluids, Faculty of Science and Technology, Mesa+ Institute and J. M. Burgers Center for Fluid Dynamics, University of Twente, 7500 AE Enschede, The Netherlands. rajaram.lv@gmail.com
authors.forename: Rajaram
authors.initials: R
authors.lastname: Lakkaraju
authors.forename: Richard J A M
authors.initials: RJ
authors.lastname: Stevens
authors.forename: Paolo
authors.initials: P
authors.lastname: Oresta
authors.forename: Roberto
authors.initials: R
authors.lastname: Verzicco
authors.forename: Detlef
authors.initials: D
authors.lastname: Lohse
authors.forename: Andrea
authors.initials: A
authors.lastname: Prosperetti
mesh_terms: D018481:Convection; D006358:Hot Temperature; D008956:Models, Chemical; D044367:Phase Transition; D044366:Transition Temperature
keywords: boundary layers; latent heat; point bubble model; simulations; two-phase convection