ANALYSIS OF CONJUGATED PROCESSES OF FILM EVAPORATION AND CONDENSATION IN A TUBULAR HEAT EXCHANGER †
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2016-06-23
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Abstract
This paper investigates coupled phase changes by forced convection from co-current flows of liquid
films and vapour-air mixtures in a tubular heat exchanger. Evaporation occurs in the inner tube and
condensation in the annulus region. Heat and mass transfers in the liquid films and the vapour-gas
mixtures are described by the conservation equations of momentum, energy and diffusion. An
appropriate change of coordinates is introduced in order to obtain a computational mesh with
straight liquid-mixture interfaces along the walls. The governing equations are discretized by an
implicit finite differences method and solved using an efficient numerical methodology. The
distributions of axial velocity, temperature and vapour concentration in all regions of the tubes are
determined from iterative procedures with a high convergence rate. The current analysis also
provides the axial evolutions of film thicknesses, heat flux, condensation and evaporation rates in
the whole domain. In addition, the effects of the inlet parameters of Reynolds number, relative
humidity, pressure and liquid flow rate on the heat transfer characteristics, the evaporation and
condensation rates are also investigated. This article is protected by copyright. All rights reserved