Numerical Analysis of Laminar Convective Condensation with the Presence of Noncondensable Gas Flowing Downward in a Vertical Channel

Abstract

The purpose of this paper is to study and perform a numerical analysis of the simultaneous processes of mass and heat transfer during the condensation process of a steam in the existence of noncondensable gas (NCG) inside a descending vertical channel. In this study, the flow of the vapor-air mixture is laminar and the saturation conditions are prevailing at the inlet of the channel. The coupled control equations for liquid film, interfacial conditions, and mixture flow are solved together using the approach of finite volume. Detailed and valuable results are presented both in the liquid condensate film and in the mixing regions. These detailed results contain the dimensionless velocity and dimensionless temperature profiles in both phases, the dimensionless mass fraction of vapor, the axial variation of the dimensionless thickness of the film liquid δ⁎, and the accumulated condensate rate Mr as well the local Nusselt number Nuy. The relative humidity at the inlet varies from 60% to 100% and the inlet temperature from 40°C to 80°C. The results confirm that a decrease in the mass concentration of NCG by the increasing the inlet relative humidity has a direct influence on the liquid film layer, the local number of Nusselt, and the variation of condensation rate accumulated through the channel. The results also designate that an increase of the inlet relative humidity and the inlet temperature ameliorates the condensation process. The comparison made for the coefficient of heat transfer due to condensation process and the condensate liquid film thickness with the literature results is in good concordance which gives more credibility to our calculation model.

Numerical Investigation of Influence of Nanoparticles Presence on Water Vapor Condensation Process inside a Vertical Channel

“…In recent times, since 2011, several authors have been interested in the study of condensation under various conditions and different geometries. These studies include the following: Giri et al [13], Li [14], Caruso et al [15,16], Zschaeck et al [17], Hammoudi et al [18], Hssain et al [19], Wu et al [20]. These authors carried out numerical studies of mixed and natural convection heat and mass transfers in different geometries and by different numerical methods.…”

“…Boundary Conditions. The boundary conditions in the transformed coordinates are prescribed below [13,19,28,29]:…”

Condensation of water vapor from humid air inside vertical channels formed by flat plates

“…(2017) for laminar film condensation of humid air along an inclined channel, where boundary layer equations were solved using the implicit finite difference method. By using the finite control volume approach, Ait Hssain provided a numerical solution of laminar convective condensation in the presence of NCG in the case of downward flowing humid air ( Ait Hssain et al., 2019 ). Besides, the author also investigated the influence of copper nanoparticles presence on the condensation performance ( Ait Hssain et al., 2021 ).…”