A comparative theoretical study on Al2O3 and γ-Al2O3 nanoparticles with different base fluids over a stretching sheet

• Alumina and γ-alumina nanofluids over a stretching sheet are investigated for the first time.
• Experimental based viscosity and thermal conductivity models used for γ-alumina fluids.
• The same nanoparticles show different effects on temperature profile with water and ethylene glycol.
• An excellent agreement is observed between present analytical and numerical results.

Nanoparticles provide potentials in augmenting the performance of convective heat transfer. In view of this, the present investigation provides comparative analytical and numerical studies on alumina and γ-alumina nanoparticles with different base fluids over a stretching sheet. Ethylene glycol and water are considered as base fluids. Boundary layer flow of γ-alumina nanofluid over a stretching sheet is considered first time in this article. The viscosity and thermal conductivity models which are derived from experimental data (Maiga et al., 2004, 2005) used for γ-alumina nanofluids and Brinkman viscosity and Maxwell’s thermal conductivity models are used for alumina nanofluids. Governing boundary layer equations are solved both analytically and numerically using confluent hypergeometric function and fourth order Runge–Kutta method with shooting technique respectively. The results obtained for the velocity profile, temperature profile, skin friction coefficient and reduced Nusselt number are presented through plots. It is predicted that the same nanoparticles have different behavior on temperature profile with water and ethylene glycol.

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