Mixed convection boundary layer flow from a horizontal circular cylinder in a nanofluid

Abstract

Purpose

The purpose of this paper is to study the steady mixed convection boundary layer flow of a nanofluid past a horizontal circular cylinder in a stream flowing vertically upwards for both cases of a heated and cooled cylinder.

Design/methodology/approach

The resulting system of nonlinear partial differential equations is solved numerically using an implicit finite‐difference scheme known as the Keller‐box method. This method is very efficient for solving boundary layer problems.

Findings

The solutions for the flow and heat transfer characteristics are evaluated numerically for various values of the parameters, namely the nanoparticle volume fraction φ and the mixed convection parameter λ at Prandtl number Pr=1 and 6.2. Three different types of nanoparticles considered are Cu, Al₂O₃ and TiO₂ by using water‐based fluid with Pr=6.2. It is found that for each particular nanoparticle, as the nanoparticle volume fraction φ increases, the skin friction coefficient and heat transfer rate at the surface also increase, and it also leads to the increment of the value of mixed convection parameter λ which first gives no separation.

Research limitations/implications

The results of this paper are valid only up to the value of λ=λ₀ (<0) below which a boundary layer solution does not exist.

Practical implications

The results obtained can be used to explain the characteristics and applications of nanofluids, which are widely used as coolants, lubricants, heat exchangers and micro‐channel heat sinks. Nanofluids usually contain the nanoparticles such as metals, oxides, or carbon nanotubes, whereby these nanoparticles have unique chemical and physical properties.

Originality/value

The results of this paper are important for the researchers working in the area of nanofluids. The paper is well prepared and presented. The results are original, new and important from both theoretical and application point of views.

Citation

Tham, L., Nazar, R. and Pop, I. (2012), "Mixed convection boundary layer flow from a horizontal circular cylinder in a nanofluid", International Journal of Numerical Methods for Heat & Fluid Flow, Vol. 22 No. 5, pp. 576-606. https://doi.org/10.1108/09615531211231253