Effect of Rib Aspect Ratio on Heat Transfer and Friction in Rectangular Channels

This paper is an investigation of the heat transfer augmentation in the fully-developed portion of a 2:1 aspect ratio channel with orthogonal ribs at Reynolds numbers based on the open channel hydraulic diameter of 20,000, 30,000, and 40,000. Ribs are applied to the two opposite wide walls. The rib aspect ratio is varied systematically from 1, 3, and 5, with a constant rib height and constant rib pitch (rib pitch-to-height ratio of 10). The purpose of the study is to extend the knowledge of the performance of rectangular channels with ribs to include high aspect ratio ribs. Data reported includes the local Nusselt number augmentation as well as the friction factor augmentation. With increasing rib width, the overall heat transfer augmentation decreased accompanied by a reduction in pressure drop. © 2011 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved

Coupled capillary and gravity-driven instability in a liquid film overlying a porous layer.

In this work, we study the problem of onset of thermal convection in a fluid layer overlying a porous layer, the whole system being heated from below. We use Brinkman's model to describe the porous medium and determine the corresponding linear stability equations. The eigenvalue problem is solved by means of a modified Galerkin method. The behavior of the critical wave number and temperature gradient is discussed in terms of the various parameters of the system. We also emphasize the influence of the boundary conditions at the upper surface of the fluid layer; in particular, we examine the role of a free surface whose surface tension is temperature dependent (Marangoni effect). Comparison with earlier works is also made.Journal ArticleSCOPUS: ar.jSCOPUS: ar.jSCOPUS: ar.jinfo:eu-repo/semantics/publishe