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Abstract: This paper investigates the behaviour of two non-mixing fluids flowing in a heated curved channel. In simulating this immiscible fluid flow, a multi-phase model based on VOF approach is developed for steady, turbulent, incompressible fluid flow through curved channel. The analysis examines the influence of centrifugal forces arising from channel curvature on the phase distribution and flow patterns, and their impact on the thermal characteristics. Unique flow features are identified through the interactions between the fluid phases and vortex structures of the immiscible flow in curved channels. The convective heat transfer in curved channel is appraised in relation to the behaviour of fluid components and curved channel flow parameters. Finally, the study presents a Second-Law irreversibility analysis whereby a thermal optimisation technique is developed for immiscible fluid flow through heated curved channels. [Copyright &y& Elsevier]

Fluid flow through curved ducts is essentially characterised by the secondary flow effects due to duct curvature and cross-sectional flow geometry. Such flows produce vortex structures making the fluid behaviour vastly different than those in straight ducts while intrinsically promoting forced convection through fluid mixing. Examining the unique features of secondary flow and wall heat transfer, this paper presents a numerical simulation on the fluid flow through curved elliptical ducts, including circular geometry. The study develops and validates a novel numerical model based on three-dimensional vortex structures (helicity) and a curvilinear mesh system to overcome previous modelling limitations. Considering several duct aspect ratios, flow rates and wall heat fluxes, computations are performed to obtain the flow patterns and thermal characteristics. Parametric influences on flow features and forced convection are described through physical interpretation. The onset of vortices due to secondary flow instability is carefully examined in relation to the duct aspect ratio and flow rate. Appraising their merits, two techniques are developed for accurate detection of secondary flow instability and integrated into the computational process, which was not previously feasible. An approach based on the Second Law irreversibility is evaluated for thermal optimisation of fluid flow through curved elliptical ducts. [ABSTRACT FROM AUTHOR]

Abstract: A numerical study was conducted to investigate the fluid flow and heat transfer characteristics of a square microchannel with four longitudinal internal fins. Three-dimensional numerical simulations were performed on the microchannel with variable fin height ratio in the presence of a hydrodynamically developed, thermally developing laminar flow. Constant heat flux boundary conditions were assumed on the external walls of the square microchannel. Results of the average local Nusselt number distribution along the channel length were obtained as a function of the fin height ratio. The analysis was carried out for different fin heights and flow parameters. Interesting observations that provide more physical insight on this passive enhancement technique, and the existence of an optimum fin height are brought out in the present study. [Copyright &y& Elsevier]