HEAT TRANSFER DURING HEAT CARRIER FLOW IN A VERTICAL POROUS MICROCHANNEL

Abstract

Heat transfer with a steady flow of coolant in a vertical microchannel filled with a porous medium is considered. The influence of porosity, the slippage effect on the wall, and the Rayleigh number on heat transfer are analyzed.
 The simulation results showed that with an increasing of the porosity parameter M (decrease permeability), the flow velocity decreases, the velocity jump on the wall also decreases, and the velocity profile becomes more filled. With an increase in the Rayleigh number, the relative flow velocity decreases, the shape of the velocity profile changes, it becomes M-shaped. At high Rayleigh numbers, the effect of free convection becomes predominant, and the shift of the maximum velocity to the channel wall is associated with a decrease in the density of the medium near the wall.
 With an increase in the Rayleigh number and the parameter M, the temperature jump on the wall decreases, local temperature values tend to the wall temperature values, the shape of the temperature profile aligns.
 An increase in the Knudsen number decreases the heat transfer rate. This is due to an increase in the temperature jump on the wall, which causes degradation in the conditions of thermal interaction between the liquid and the wall.The dynamics of change of the relative Nusselt number with increasing Rayleigh number shows that there is an inversion of the influence of the porosity parameter M on the heat transfer coefficient. With small values of Ra, with an increase in the parameter M, the heat transfer coefficient increases, since the temperature jump on the wall decreases. At Ra = 400, the effect of porosity is not observed.
 At high values of Ra, the intensity of heat transfer decreases but not so sharply as at low of Ra. That effect is caused from decreasing rate flow near the wall.