Convective heat transfer studies in dilute alumina and silica nanofluids flowing through a channel using Mach-Zehnder interferometry

Abstract

Convective heat transfer in dilute oxide nanofluids flowing through a channel was measured using the Mach-Zehnder interferometry, a non-intrusive measurement technique. The convective performance of two different concentrations (0.01 and 0.02 vol.%) of alumina and silica nanofluids were studied and compared with that of de-ionized (D.I) water. In the present work, fringe analysis based on Naylor and Duarte method, with appropriate modifications for liquids was used to measure the local heat transfer coefficients along the channel. Studies have previously been reported only on the effects of Reynolds number in the channel flow, at a single heat input. In the present work, experiments were conducted at a constant Reynolds number (200), for six different heat inputs in the range of 5 W to 30 W. At 30 W, the enhancement in average heat transfer coefficient for 0.02 vol.% alumina nanofluid was 15.9 ± 4.1%, while, 0.02 vol.% silica nanofluid showed a decrement of 11.9 ± 2.9% compared to D.I water. Silica nanofluids were found performing inferior to D.I water and alumina nanofluids for all heat inputs. The variations in the trend for silica nanofluids are explained in the light of thermophoretic effects, Brownian motion and disruption of boundary layer.