Experimental investigation on thermo-physical properties and subcooled flow boiling performance of Al2O3/water nanofluids in a horizontal tube

Abstract

In the present experimental work, forced convective flow boiling heat transfer under subcooled region was analysed with Al2O3/water nanofluid flow in a horizontal tube. Nanofluids at various wt.% such as 0.01%, 0.05%, 0.1%, 0.5% and 1% were prepared using two-step method. Stability of nanofluids was measured using Zeta potential analysis. Thermo-physical properties such as the thermal conductivity and viscosity of all test samples were estimated over 25°C-65 °C. An experimental test rig was setup to study the convective heat transfer using nanofluids. The effects of concentration, heat flux, flow rate, surface roughness on heat transfer coefficient were measured. The experimental result showed good stability in nanofluids without any surfactants. A significant increase in convective heat transfer coefficient (HTC) was found due to enhancement in the thermo-physical properties of nanofluids. Increase in pressure drop was registered with the rise of concentration and flow rate. Finally, performance evaluation criterion (PEC) showed that Al2O3 nanofluids can increase the overall thermal performance of the system by 94% in comparison with pure water.