Numerical and experimental investigation of high concentration aqueous alumina nanofluids in a two and three channel heat exchanger

Abstract

Nanofluids are often able to provide a method to increase the possible heat transfer of a system, with relatively few detrimental factors created by its inclusion. The use of nanofluids and their optimal concentrations has become an area of great interest as of late, with different nanofluid concentrations being key to a systems success or hindrance. The aim of this work is to examine the impact of nanofluid concentration on the possible heat transfer for different heat sink types containing porous media. In this work, both a numerical and experimental investigation into the impact of an aluminum oxide nanofluid on a fluid flow-based system comprised of porous open-cell aluminum foam to examine their impact on the thermal performance of the system was conducted. The porous media implemented in the experimental work was made of a 6061-T6 aluminum with a porosity of 0.91 and a permeability of 2.3869 × 10−7 m2. The experimental work was carried out for a large range of applied heat flux values varying from 3.8328 W cm-2 to 10.3737 W cm−2. The nanofluid examined was also subjected to varying flow rates. The nanofluid concentration was varied from 1% vol and 2% vol Al2O3–water mixture. The nanofluid was suspended in distilled water and mixed using a magnetic mixer. The performance of the work was examined through the Nusselt number to determine the possible thermal enhancement presented by the nanofluid. The use of high concentration (1% vol) nanofluid paired with the use of two different channel designs, both containing porous media resulted in an average thermal enhancement 15% and a maximum enhancement of 24.5% when compared to that of the 2% vol alumina nanofluid.

Keywords

• Nanofluid
• Alumina
• Porous medium
• Forced convection
• Navier Stokes formulation
• Darcy-Brinkman model