Heat transfer measurement in aluminium oxide nanofluid using rectangular Thermosyphon loop

Abstract

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.

Nanofluids are generally found to exhibit better thermophysical properties and heat transfer capabilities than the corresponding base fluids. Experimental and theoretical investigations on the forced and free convection behavior have reported superior heat transfer capability of nanofluids, except in a few cases. Studies on natural/free convective heat transfer in nanofluids have shown negative impacts when investigations were performed on a vertical column of the fluid. The absence of a pumping system makes natural circulation loops silent and also saves the energy for pumping the fluid. Since the thermosyphon loop resembles a forced circulation loop except for the absence of a pump, a nanofluid can be expected to yield enhanced heat transfer, compared to the base fluid. The present work captures the heat transfer performance of oxide nanofluids in a rectangular thermosyphon loop. The density gradient created by the temperature gradient between the heating and cooling sections, assisted by gravity, constitute the driving force in the loop. The temperature of the fluid at the inlet and exit of the heating sections and, on the pipe surface along the heating section is measured. The effect of the external heat input, concentration of nanofluids and average temperature of the cooling section on the heat transfer are investigated. The results have shown that the Al2O3 nanofluids have enhanced heat transfer characteristics as compared to water in rectangular thermosyphon loops.