Modeling of heat and mass transfer in a hydrocarbon fluid under inductive heating

Abstract

Results of numerical simulations of the thermal action on a high-viscosity hydrocarbon fluid with temperature-dependent viscosity and thermal conductivity are presented. A system of equations of thermal convection in the Boussinesq approximation is used as the constitutive equations to describe the convection of the hydrocarbon fluid. The dynamics of the temperature field and convective structures in the fluid is studied. The spatial motion of the fluid is found to be locally nonuniform; the motion is accompanied by vortex flows; as a result, two regions with significantly different temperatures are formed in the medium. Introduction.Results of experimental research of heating of heavy hydrocarbon systems by an inductive heater and results of mathematical modeling of this experiment were reported in [1]. The thermal convection of the fluid was taken into account by introducing an effective thermal conductivity. The fluid under study was a heavy hydrocarbon system, which has extremely low values of fluidity and thermal conductivity at low temperatures. Based on results of experimental and numerical studies, a conclusion was drawn that the effective thermal conductivity became substantially increased with increasing temperature, which was a consequence of the emergence of local spots of vortex motion of the fluid in regions where the temperature exceeded some threshold value corresponding to the beginning of fluidity. The spatial region where this motion occurred and the temperature field in this region displayed permanent irregular changes, which was observed visually and was recorded by temperature gauges located inside the reservoir. A mathematical model of heating of a heavy hydrocarbon system in a closed reservoir is proposed in the paper to describe the effects noted above. The model takes into account not only the effect of temperature on viscosity and thermal conductivity of the fluid, but also the presence of free convective motion of the fluid.Mathematical Model. We consider a closed metallic reservoir whose base is covered by a concrete layer, and there is an inductor tube in the center. The space between the inductor tube and the outer wall of the reservoir is filled by a high-viscosity hydrocarbon fluid. Some part of the inductor tube wall is heated by the inductor tube; as a result, the fluid becomes heated. The computational domain corresponding to the physical model described above is schematically shown in Fig. 1. The problem is solved in an axisymmetric formulation in a cylindrical coordinate system with the origin in the center of the reservoir base and with the z axis directed upward, perpendicular to the base. From the viewpoint of mathematical modeling, the physical model is a multilayer system consisting of the inductor tube, concrete layer, and hydrocarbon medium (see Fig. 1). The temperature field is calculated in each layer; the velocity field of the convective flow of the fluid is additionally determined in the hydrocarbon medium.

Physical and mathematical modeling of high-frequency electromagnetic exposure of hydrocarbon media

“…4 and 5) is more uniform than that during induction heating [10,14], most of the liquid volume is covered by convective flow (see Fig. 4), which significantly accelerates the heat transfer in the liquid.…”