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Thermal performance of a propylene glycol/alumina nanofluid under internal developing laminar flow

Abstract:

The mechanisms involved in nanofluids thermal-hydraulic transport is still a not very well stablished subject. The nanoparticles distribution strongly affects the cross section velocity pattern under internal undeveloped laminar flow regime in a straight pipe. According to the proposed model, the nanoparticles driving mechanism is thermophoretic diffusion which is especially strong under high wall heat fluxes. This paper aims at the assessment of the uppermost limiting cases for the thermophoretic driving force in a nanofluid by dealing with a high Prandtl number base fluid like the propylene glycol and alumina nanoparticles. The generalized Soret coefficient for this nanofluid attains high values due to the high viscosity of the base fluid. The thermalhydraulic performance of this nanofluid has been obtained through a new CFD solver which includes both brownian and thermophoretic diffusion along with nanoparticles concentration and temperature effects over the transport properties. A 4.5 mm. diameter and 1, 010 mm length tube has been chosen as the case study under different heat fluxes and mass flow rates conditions for a 6% volumetric concentration of nanoparticles. It has been found that present pure base fluid and nanofluid results, based on test tube average transport properties, over pbkp_redict classical laminar flow regime Nusselt-Graetz correlations. In addition, for the same average velocity and tube entrance temperature, no appreciable heat transfer enhancement has been found by the flow of the nanofluid with respect to the base fluid.