The Study On Fluid Natural Convective Heat And Mass Transfer Within Porous Media Containing Dip Angle

In nature and engineering practice, there are many porous media with dip angle generally. For example, the contact surface of insulation material and indoor form porous medium containing angle with horizontal, the contact surface of coal and rock in coal and rock mass form porous medium containing angle with horizontal. Research of fluid heat and mass transmission in porous media with dip angle is good for knowing distribution of flow field, temperature field and concentration field more accurately and creating comfortable indoor environment providing theoretical reference. It can provide necessary condition for the development of building energy efficiency, in order to prevent spontaneous combustion of coal seam, to reduce gas accident and hot damage in mine and to protect the safety of workers providing the theoretical basis.Building indoor residential environment and coal mine safety are the background of this paper depending on the theory of natural convection heat and mass transfer in porous media. Porous medium physical model of different contact surface angle is establish. Laminar mathematical model of considering cross coupling effect when temperature gradient and concentration gradient exist is introduced, and turbulence mathematical model of ignoring cross coupling effect when temperature gradient and concentration gradient exist is introduced and mathematical model is converted into dimensionless form. Using theoretical analysis, numerical calculation method, further studying when considering cross coupling effect, and dip angle, dimensionless parameters and diffusion rule number have an effect on the isotropic porous medium of containing dip angle laminar fluid flow, heat and mass transfer, and put forward influence law; further researching when ignoring cross coupling effect, dip angle have an effect on turbulence natural convection heat and mass transfer in isotropic porous medium, and dip angle have an effect on turbulence natural convection heat and mass transfer in two direction isomerism porous medium; contrastively analyze the above two cases of heat and mass transfer rate, obtaining difference and contact. Obtaining different Ra corresponding to velocity of vertical direction in the isotropic and two direction isomerism porous medium containing dip angle, obtain critical velocity of vertical direction from laminar turning into turbulence in porous medium containing dip angle.Study results show that:when flow is laminar in the isotropic porous media, with increase of dip angle, strength of fluid flow enhances in porous media, heat transfer to be weaken, mass transfer to be enhanced. With increase of Ra and N, flowing faster, enhancing heat and mass transfer. with increase of Le,flow intensity to be weakened, heat transfer rate remaining unchanged, mass transfer rate faster. With increase of SCT, flowing faster, heat transfer rate remaining unchanged, mass transfer rate faster. With increase of DTC, flowing faster, heat transfer rate faster, mass transfer rate remaining unchanged. The change of dip angle do not affect dimensionless parameters on the influence law of laminar fluid flow and heat mass transfer within the isotropic porous media. When the flow is turbulent, with increase of dip angle, fluid flow intensity is strong and weak within isotropic porous media, heat and mass transfer rate fasting and slowing alternant, no monotonous change rule. When the flow is turbulent, with increase of dip angle, the variation tendency of heat and mass transfer rate within two direction isomerism porous medium is same with the variation tendency of heat and mass transfer rate within isotropic porous media. Obtain the vertical direction critical velocity of laminar turnning into turbulent is v=17.825 m· s-1.