Comment on the comment by V. A. F. Costa, IJTS 49 (9) (2010) 1874–1875, on the paper by I. A. Badruddin, Z. A. Zainal, Z. A. Khan, Z. Mallick “Effect of viscous dissipation and radiation on natural convection in a porous medium embedded within vertical annulus”, IJTS 46 (3) (2007) 221–227

Abstract: A comment on a recent paper about the combined effects of radiation and viscous dissipation on the convection in an annular porous enclosure has raised the problem of the role played by the viscous dissipation and the pressure work contributions in buoyant flows. The aim of this further comment is to show that the criticism expressed by Costa on the model of the viscous dissipation effect employed in the paper by Badruddin and co-workers is unjustified. [ABSTRACT FROM AUTHOR]