Forced Convection Heat Transfer in a Cylindrical Porous Media exposed to Constant Wall Heat Flux.

Document Type : Research Studies

Author

Mechanical Power Engineering Department., Faculty of Engineering., El-Mansoura University., Mansoura., Egypt.

Abstract

Forced convection heat flow in a cylindrical packed bed is examined numerically.  The bed is filled with saturated spherical beads porous media and is exposed to a  constant wall heat flux. Besides the energy equation, the generalized from. of the  momentum equation including the non-Darcian effects such as the variable porosity,  flow inertia, and viscous friction is considered, and the finite difference method is used. 
The results have been obtained numerically for sphere beads (3≤ d8 mm diameter),  ratio of the particle diameter to the pipe radius 0.05 ≤ D 0.5, and nondimensional  pressure gradient B up to 108. The non-Darcian effects have a significant influence on  the behavior of the temperature, thermal entry length. and Nusselt number across and at  the channel wall. The channeling phenomenon near the walls enhanced the thermal  communication between the fluid/solid matrix. composite and the walls. This fact yielded  an overall 21 percent increase in the value of the Nu in the fully developed region,  compared to the value predicted when the Darcy model was used. The results gives  complete information about the flow structure and heat transfer for the expressed ranges  of parameters. Also, useful correlations reporting the dependence of the thermal entry  length on the problem parameters (d, D, B) were reported. A direct dependence of the  thermal entry length on Re exists and gives the same correlation that obtained for the  pure fluid flow case:  
XE ͠= 0.1 Re
To verifY the numerical results a comparison have been done with the numerical  results obtained by Poulikakos and Renken [11], Kays and Crawford [26] and Petukhov  [27]. The comparison shows a very good agreement for the presented results and proves  the validity of the model.  

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