Porous media natural convection

P. Cheng, Natural Convection Porous Medium External Flows, in Natural Convection Fundamentals and Applications, S. Kakac, W. Aung, and R. Viskanta eds., pp. 475-513, Hemisphere Publishing, Washington, DC, Springer-Verlag, Berlin, 1985. 

Daccord G, Lenormand R (1987) Fractal patterns from chemical dissolution. Nature 325 41 3 Daccord G, Lietard O, Lenormand R (1993) Chemical dissolution of a porous medium by a reactive fluid, 2, Convection vs. reaction behavior diagram. Chem Eng Sci 48 179-186 Darmody RG, Thorn CE, Harder RL, Schlyter JPL, Dixon JC (2000) Weathering implications of water chemistry in an arctic-alpine environment, north Sweden. Geomorphology 34 89-100 Dijk P, Berkowitz B (1998) Precipitation and dissolution of reactive solutes in fractures. Water Resour Res 34 457-470... 

The reduction of the thickness of the flow channel, as discussed earlier, is equivalent to introducing more surface area per unit volume of medium. High surface areas inhibit all flow, including natural convective flow. One can increase relative surface areas by going to thinner tubes or channels, or by using a fine granular or porous support medium. Both approaches are used in electrophoresis as discussed in a subsequent chapter. 

Natural convective flows in porous media occur in a number of important practical situations, e.g., in air-saturated fibrous insulation material surrounding a heated body and about pipes buried in water-saturated soils. To illustrate how such flows can be analyzed, e.g., see [20] to [22], attention will be given in this section to flow over the outer surface of a body in a porous medium, the flow being caused purely by the buoyancy forces resulting from the temperature differences in the flow. The simplest such situation is two-dimensional flow over an isothermal vertical flat surface imbedded in a porous medium, this situation being shown schematically in Fig. 10.25. 

Discuss how the analysis of natural convective flow over a vertical flat plate in a saturated porous medium must be modified if there is a uniform heat flux rather than a uniform temperature at the surface. 

Bejan, A. and Tien, C.L., Natural Convection in a Horizontal Porous Medium Subjected to an End-to-End Temperature Difference , J. Heat Transfer, Vol. 100. pp. 191-198, 1978. 

Oosthuizen, P.H. and Paul, J.T., Natural Convective Flow in a Square Cavity Partly Filled with a Porous Medium", Proc. 1987 ASME/JSME Thermal Engineering Joint Conf, Vol. 2. Am. Soc. Mech. Eng.. New York, 1987, pp. 407-412. 

Oosthuizen, P.H., Natural Convection in an Inclined Suuure F.nclosure Partly Filled with a Porous Medium and with a Partially Heated Will". Heat Transfer in Porous Media and Two-Phase Flow. ASME HTD-Vol. 302. Energy- Sources Technology Conference and Exhibition. Houston. TX. 1995, pp. 29-42. 

Oosthuizen. PH. and Naylor. D.. Natural Convective Heat Transfer from a Cylinder in an Enclosure Partly Filled w ith a Porous Medium, Ini. J. Sumer. L riiods Heat and Fluid Flow. Vol. 6, No. 6. pp. 51-63. 1996. 

Bejan, A. and Poulikakos. D.. The NonDarcy Regime for Vertical Boundary Layer Natural Convection in a Porous Medium , Int. J. Heat Mass Transfer, Vol. 27, pp. 717-722, 1984. 

J. W. Elder, Steady Natural Convection in a Porous Medium Heated From Below, /. Fluid Mech. (27) 29-48,1967. 

M. R. Fand, T. E. Steinberger, and P. Cheng, Natural Convection Heat Transfer From a Horizontal Cylinder in a Porous Medium, Int. J. Heat Transfer (29/1) 119-133,1986. 

Das, S.S., Mohanty, M., Panigrahi, S.K., Padhy, R.K., Sahu, M., 2012. Radiative heat and mass transfer effects on natural convection Couette flow through a porous medium in the slip flow regime. Int. J. Renew. Energy Technol. Res. 1, 1-14. 

A further complication arises in forced convection in fabric, which is a porous medium. There may be significant thermal dispersion, i.e., heat transfer due to hydrodynamic mixing of the fluid at the pore scale. In addition to the molecular diffusion of heat, there is mixing due to the nature of the fabric. 

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