Effect of Al₂O₃ nanoparticles on laminar, transient and turbulent flow of isopropyl alcohol

The laminar, transient and turbulent heat transfer and hydrodynamic of a new nanofluid isopropanol/Al₂O₃ is investigated in a closed flow loop with a horizontal mini-channel test section (3.5 mm inner diameter) under uniform heat flux conditions. The experiments performed at various inlet temperatures (15, 25, 35 °C), mass flow rates (from 0.00076 to 0.041 kg/s) and nanoparticle concentrations (0.387, 0.992, 3.12, 4.71 mass%). We found that despite the pressure drop increases with Reynolds number and nanoparticles mass fraction the dependence of friction factor for the isopropanol/Al₂O₃ nanofluid remains the same as for the base fluid. The heat transfer performance of isopropanol/Al₂O₃ nanofluid was evaluated in two ways (i) depending on the Reynolds number and (ii) product of the mass flow rate and specific heat capacity. The first approach indicates to significant enhancement of the heat transfer coefficient with addition of nanoparticles in all range of experimental parameters. The second approach shows no effect of nanoparticles on the heat transfer coefficient in laminar flow and its deterioration in transient and turbulent flows. Both effects of nanoparticles on the heat transfer are attributed to change in intensity of the turbulence in nanofluids compared to the base fluids. Finally, an influence of nanoparticles on the start of laminar-turbulent transition was examined.