Experiments and Simulations of Laminar Forced Convection With Water–Alumina Nanofluids in Circular Tubes

Abstract

This work reports fundamental experimental-theoretical research related to heat transfer enhancement in laminar channel flow with nanofluids, which are essentially modifications of the base fluid with the dispersion of metal oxide nanoparticles. The nanofluids were synthesized by a two-step approach, using a dispersant and an ultrasound probe or a ball mill for alumina nanoparticles dispersion within the aqueous media. The theoretical work involves the proposition of an extension of the thermally developing flow model that accounts for the temperature variation of all the thermophysical properties, including viscosity and the consequent variation of the velocity profiles along the thermal entry region. The simulation was performed by making use of mixed symbolic-numerical computation on the Mathematica 7.0 platform and a hybrid numerical-analytical methodology (generalized integral transform technique, GITT) in accurately handling the governing partial differential equations for the heat and fluid flow problem formulation with temperature dependency in the thermophysical properties. Experimental work was also undertaken based on a thermohydraulic circuit built for this purpose, and sample results are presented to verify the proposed model. The aim is to confirm that both the constant properties and temperature-dependent properties models, besides available correlations previously established for ordinary fluids, provide adequate prediction of the heat transfer enhancement observed in laminar forced convection with such nanofluids and within the experimented Reynolds number range.

Investigation Into Effective Viscosity, Electrical Conductivity, and pH of γ-Al2O3-Glycerol Nanofluids in Einstein Concentration Regime

“…A number of research efforts aimed at understanding the dynamics of nanofluids thermal properties have been published such as thermal conductivity [10][11][12][13], viscosity [14][15][16], convective heat transfer [17,18], electrical conductivity [19][20][21], specific heat capacity [22], thermal diffusivity [23] , density [24]. However, the search for a lasting explanation to the anomalous behaviours of nanofluids as depicted from different literatures continues.…”

Heat transfer coefficient: a review of measurement techniques

“…Cerqueira et al [77] and Moreira et al [78] measured the HTC during forced convection inside a tube using waterbased nanofluids as fluid. Nanofluids are the mixing of a base fluid and nanometric-scale particles in order to improve fluid properties, like thermal conductivity [79].…”