Title

Influence of Nanofluids on Mixed Convective Heat Transfer over a Horizontal Backward-Facing Step

Document Type

Article

Publication Date

6-2011

Publication Source

Heat Transfer-Asian Research

Volume

40

Issue

4

Inclusive pages

287-307

DOI

10.1002/htj.20344

Publisher

John Wiley & Sons, Inc.

Place of Publication

United States

ISBN/ISSN

1523-1496

Peer Reviewed

yes

Abstract

Predictions are reported for laminar mixed convection using various types of nanofluids over a horizontal backward-facing step in a duct, in which the upstream wall and the step are considered adiabatic surfaces, while the downstream wall from the step is heated to a uniform temperature that is higher than the inlet fluid temperature. The straight wall that forms the other side of the duct is maintained at constant temperature equivalent to the inlet fluid temperature. Eight different types of nanoparticles, Au, Ag, Al2O3, Cu, CuO, diamond, SiO2, and TiO2, with 5% volume fraction are used. The conservation equations along with the boundary conditions are solved using the finite volume method. Results presented in this paper are for a step height of 4.9 mm and an expansion ratio of 1.942, while the total length in the downstream of the step is 0.5 m. The Reynolds number is in the range of 75 ≤ Re ≤ 225. The downstream wall was fixed at a uniform wall temperature in the range of 0 ≤ ΔT ≤ 30 °C which is higher than the inlet flow temperature. Results reveal that there is a primary recirculation region for all nanofluids behind the step. It is noticed that nanofluids without secondary recirculation region have a higher Nusselt number and it increases with Prandtl number decrement. On the other hand, nanofluids with secondary recirculation regions are found to have a lower Nusselt number. Diamond nanofluid has the highest Nusselt number in the primary recirculation region, while SiO2 nanofluid has the highest Nusselt number downstream of the primary recirculation region. The skin friction coefficient increases as the temperature difference increases and the Reynolds number decreases. © 2011 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library (

wileyonlinelibrary.com/journal/htj). DOI 10.1002/htj.20344

Keywords

mixed convection; horizontal backward-facing step; heat transfer enhancement; nanofluids

Disciplines

Engineering | Heat Transfer, Combustion | Other Mechanical Engineering

This document is currently not available here.

  Contact Author

Share

COinS