Pseudoplastic natural convection flow and heat transfer in a cylindrical vertical cavity partially filled with a porous layer

Abstract

Purpose

This paper aims to theoritically investigate the free convection flow and heat transfer of a non-Newtonian fluid with pseudoplastic behavior in a cylindrical vertical cavity partially filled with a layer of a porous medium.

Design/methodology/approach

The non-Newtonian behavior of the pseudoplastic liquid is described by using a power-law non-Newtonian model. There is a temperature difference between the internal and external cylinders. The porous layer is attached to the internal cylinder and has a thickness of D. Upper and lower walls of the cavity are well insulated. The governing equations are transformed into a non-dimensional form to generalize the solution. The finite element method is used to solve the governing equations numerically. The results are compared with the literature results in several cases and found in good agreement.

Findings

The influence of the thickness of the porous layer, Rayleigh number and non-Newtonian index on the heat transfer behavior of a non-Newtonian pseudoplastic fluid is addressed. The increase of pseudoplastic behavior and increase of the thickness of the porous layer enhances the heat transfer. By increase of the porous layer from 0.6 to 0.8, the average Nusselt number increased from 0.15 to 0.25. The increase of non-Newtonian effects (decrease of the non-Newtonian power-law index) enhances the heat transfer rate.

Originality/value

The free convection behavior of a pseudoplastic-non-Newtonian fluid in a cylindrical enclosure partially filled by a layer of a porous medium is addressed for the first time.

Citation

Ayoubi Ayoubloo, K., Ghalambaz, M., Armaghani, T., Noghrehabadi, A. and Chamkha, A.J. (2020), "Pseudoplastic natural convection flow and heat transfer in a cylindrical vertical cavity partially filled with a porous layer", International Journal of Numerical Methods for Heat & Fluid Flow, Vol. 30 No. 3, pp. 1096-1114. https://doi.org/10.1108/HFF-06-2019-0464