Hydrodynamic Instability and Heat Transfer Analysis of Nanoflow in Semi-Porous Microchannels
Date
2019-03-11
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Abstract
This dissertation focuses on the simulation of nanofluid and fluid flow in a semi-porous microchannel. Despite the wide applications of nanoparticles in recent years, there are still some nano-exclusive phenomena which render the performance of the nanofluid unpredictable. The nano-scale specific properties can be positive or negative depending on the nanoparticle and the surrounding conditions, ignoring which, result in imprecise predictions. Therefore, this dissertation analyzes the hydrodynamic and thermal behavior of nanofluid and fluid flow in semi-porous microchannels, employing the Lattice Boltzmann method. First, the flow instabilities in nanofluid flow in a porous microchannel are studied. It is shown that the nanoparticle effect on instability is highly-dependent on its properties and the surrounding conditions. It is also revealed that nanoparticles behave differently at various viscous regimes, and the instability is controlled by the physical and chemical properties of the nanoparticles. The second part focuses on the heat transfer behavior of the porous microchannel in the presence of nanofluid. It is shown that the nanoparticle distribution plays important roles in heat transfer. Particle size and surface energy are also found to change the whole picture of heat transfer and therefore, a characteristic curve is introduced, using which, nanoparticles can safely improve heat removal. In the third section, the analysis of the second part is extended to randomly distributed pin-based microchannels with special attention to nanoparticle adsorption on pin surfaces. Statistical analysis shows that various random realizations behave differently, and an averaged behavior can be found. Nanoparticle adsorption on the pin surface is found to have double-edged effects and can be beneficial or detrimental to heat removal. Finally, the hydrodynamic and thermal behavior of partially-porous microchannel are analyzed. It is revealed that, unlike the fully-porous microchannel, the thermal performance of these systems is complicated. The study shows existence of hydrodynamic and thermal critical porous medium heights where the impact of the porous medium becomes imperative. A particle tracing technique is adopted to explain the underlying physics and a mathematical model is proposed to explain the interplay between the critical points and the hydrodynamic, geometric, and thermal parameters.
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Keywords
Nanoparticles, LBM, Microchannel, Heat Transfer, Flow Dynamics
Citation
Zargartalebi, M. (2019). Hydrodynamic instability and heat transfer analysis of nanoflow in semi-porous microchannels (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.