Numerical analysis for the problem of steady natural convection heat transfer by double diffusion from a heated cylinder buried in a saturated porous media

Author(s):  
CARLOS ALBERTO CHAVES ◽  
JOSÉ RUI CAMARGO ◽  
FRANCISCO JOSÉ GRANDINETTI ◽  
WENDELL DE QUEIROZ LAMAS ◽  
OSVAIR VIDAL TREVISAN
2015 ◽  
Vol 137 (7) ◽  
Author(s):  
Carlos Alberto Chaves ◽  
Wendell de Queiroz Lamas ◽  
Luiz Eduardo Nicolini do Patrocinio Nunes ◽  
Jose Rui Camargo ◽  
Francisco Jose Grandinetti

This paper aims to present numerical solutions for the problem of steady natural convection heat transfer by double diffusion from a heated cylinder buried in a saturated porous media exposed to constant uniform temperature and concentration in the cylinder and in the media surface. A square finite domain 3 × 3 and acceptance criterion converged solution with an absolute error under 1 × 10−3 were considered to obtain results presented. The Patankar's power law for approaching of variables calculated T, C, and ϕ also was adopted. In order of method validation, an investigation of mesh points number as function of Ra, Le, and N was done. A finite volume scheme has been used to predict the flow, temperature, and concentration distributions at any space from a heat cylinder buried into a fluid-saturated porous medium for a bipolar coordinates system. Examples presented show that the differences in the flow distribution caused not only when Rayleigh number range is considered but also when Lewis number range is considered. Further, increase in the Rayleigh number has a significant influence in the flow distribution when the concentration distribution is considered. Steady natural convection heat transfer by double diffusion from a heated cylinder buried in a saturated porous medium is studied numerically using the finite volume method. To model fluid flow inside the porous medium, the Darcy equation is used. Numerical results are obtained in the form of streamlines, isotherms, and isoconcentrations. The Rayleigh number values range from 0 to 1000, the Lewis number values range from 0 to 100, and the buoyancy ratio number is equal to zero. Calculated values of average heat transfer rates agree reasonably well with values reported in the literature.


1970 ◽  
Vol 6 (1) ◽  
Author(s):  
Ahmed F. Alfahaid, R.Y. Sakr ◽  
M. I. Ahmed

Natural convection in horizontal annular porous media has become a subject receiving increasing attention due to its practical importance in the problem of insulators, such as ducting system in high temperature gas-cooled reactors, heating systems, thermal energy storage systems, under ground cable systems, etc. This paper presents a numerical study for steady state thermal convection in a fully saturated porous media bounded by two horizontal concentric cylinders, the cylinders are impermeable to fluid motion and maintained at different, uniform temperatures.  The solution scheme is based on two-dimensional model, which is governed by Darcy-Oberbeck-Boussinesq equations. The finite element method using Galerkin technique is developed and employed to solve the present problem. A numerical simulation is carried out to examine the parametric effects of Rayleigh number and radius ratio on the role played by natural convection heat transfer in the porous annuli. The numerical results obtained from the present model were compared with the available published results and good agreement is observed. The average Nusselt number at the heating surface of the inner cylinder is correlated to Rayleigh number and radius ratio.Keywords: Natural convection, numerical investigation, saturated porous media, finite element method, concentric horizontal annuli.


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