The numerical simulation of an evaporating multifraction vapor-droplet mixture of methane in a pipe taking into account the swirling flow

This work is a numerical study of the thermo-hydrodynamics in the flow of a methane vapor-droplet mixture in a device for heating mixtures of gases and liquids. The subject of the research are the physical processes occurring in liquefied natural gas regasification apparatuses. The purpose of the work is to reveal the regularities of the dynamics of a polydisperse vapor-droplet mixture in a pipe with heated walls. The dynamics of the carrier medium are described by Navier-Stokes equations for a compressible heat-conducting medium, taking into account the exchange of mass, momentum, and energy with the dispersed phase. The dispersed phase included several fractions of different sizes. Each fraction is described by equations consisting of the continuity equation for the average density, the conservation equations for the momentum components, and the thermal energy conservation equation, taking into account the interaction of the multi-fraction dispersed phase with the carrier medium. The mathematical model takes into account the swirl of the flow using the tangential components of the velocity vectors of the carrier phase and fractions of the dispersed phase. The equations of the motion of the carrier medium and the fractions of the dispersed phase are solved by the McCormack explicit finite-difference method of the second order. To overcome numerical oscillations, a scheme of nonlinear corrections of the grid function is used. At each time step, the main part of the computational algorithm is supplemented by a droplet evaporation model with a subsequent correction of the hydro- and thermodynamic parameters of the mixture. The results showed a significant difference in the intensity of evaporation of the fractions of the liquid methane phase of the mixture, which have different sizes of dispersed inclusions, it was also determined that during the movement of the evaporating mixture, the highest pressure of the vapor phase is observed near the inflow of the methane mixture into the pipe with heated walls. These regularities can be applied in devices working with gas-liquid media.