Theoretical study of variable viscosity nanofluids flow in microchannels

Monaledi, Ramotjaki (2020-12)

Thesis (PhD)--Stellenbosch University, 2020.


ENGLISH ABSTRACT: The study of fluid flow and heat transfer through a microchannel is an important research area due to its wide applications in engineering and industrial processes. Some practical applications include problems dealing with cooling, lubrication of porous bearings, petroleum technology, ground water hydrology, drainage and purification processes. A nanofluid is the suspension of nanoparticles in a base fluid. Nanofluids are capable of heat transfer enhancement due to their high thermal conductivity. For practical applications of nanofluids, research in nanofluids convection is significant. Due to their enhanced properties, nanofluids can be used in the deficiency of technical and biomedical applications such as nanofluid coolant in electronics cooling, vehicle cooling and transformer cooling. This study considered the detailed analysis of both single and two-phase Couette and Poiseuille flow behaviour and heat transfer using this innovative fluid as working fluid through a microchannel. Useful results for the velocity, temperature, nanoparticles concentration profiles, skin friction and Nusselt number were obtained and discussed quantitatively. The effects of important governing flow parameters on the entire flow structure were examined. In this thesis, a more realistic modified Buongiorno’s nanofluid model is proposed and utilized to examine the impact of nanoparticles’ injection and distribution on inherent irreversibility in a microchannel Poiseuille flow of nanofluid with variable properties. The governing nonlinear differential equations are obtained and tackled numerically using the shooting method coupled with the Runge-Kutta-Fehlberg integration scheme. Graphical results showing the effects of the pertinent parameters on the nanofluid velocity, temperature, nanoparticles concentration, skin friction, Nusselt number, Sherwood number, entropy generation rate and Bejan number are presented and discussed quantitatively.

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