Effects of Slip Boundaries on Mixed Convection of Al2O3-water Nanofluid in Microcavity

Subject Areas : Mechanical Engineering

A. R.  Rahmati ¹ (Department of Mechanical Engineering, University of Kashan, Iran)
T.  Azizi ² (Department of Mechanical Engineering, University of Kashan, Iran)
S. H.  Mousavi ³ (Department of Mechanical Engineering, University of Kashan, Iran)
A.  Zarareh ⁴ (Department of Mechanical Engineering, University of Kashan, Iran)

Received: 2014-11-17 Accepted : 2015-03-15 Published : 2015-06-01

Keywords: Knudsen Number, Mixed Convection, Nano fluid, Microcavity, Slip Flow,

Abstract :

Due to the importance of the slip effect on modeling of microchannel and microcavity, numerical investigations have been introduced in this work for studying the mixed convection of Al2O3-water nanofluid in a square microcavity. Governing equations are discretized and solved using the Finite Volume Method and SIMPLER algorithm. The Knudsen number is selected between 0.001 and 0.1 to consider slip velocity and the temperature jump boundary conditions in slip flow regime. In this study we investigate the influence of the Knudsen number on the average Nusselt number and heat transfer rate of Al2O3-water nanofluid. Results shows that the average Nusselt number is the function of Richardson number, Knudsen number and volume fraction of nanoparticles. Increasing the Richardson number, makes the forced convection less effective and leads in reduction of the Nusselt number. Hence, increasing the Knudsen number, leads to the temperature gradient reduction and reducing the average Nusselt number. As a result, the average Nusselt number could be enhanced up to 10.93% by using nanoparticles in the base fluid.

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