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The present work deals with the numerical investigation of forced convection flow and heat transfer in a finned concentric annulus. The outer cylinder is axially finned while the rotating inner cylinder has a smooth surface. Our research focus on the impact of the fin inclination angle on heat transfer enhancement in rotating annular channels. Tests were carried out for different geometrical configurations using fins with inclined angle (α = 30°, 60°, 90° and 120°). Numerical study is based on effective Reynolds number and Taylor number. The results obtained using the code ANSYS-Fluent with SST k-ω turbulence model show a good agreement between the experimental and the numerical results. In the presence of rotational flow (Ta = 1.14 × 106), the results indicate that α =120° is the optimal case which improves significantly the heat and mass transfer inside the finned channel.

The effect of radial flow injection on the heat transfer characteristics of a Taylor–Couette–Poiseuille flow in an annulus is numerically investigated using the SST k-ω turbulence model. Th...

In this paper, we investigate the effects of an imposed axial flow on hydrodynamic instabilities’ Couette-Taylor flow in the case where the wall of the inner cylinder of the system is grouved. Without imposed axial flow, the basic flow of a fluid between two coaxial cylinders known by Couette flow, which is characterized by several temporal and spatial symmetries. The increase in the rotation causes the breaking of these symmetries. In both cases where the surface of the inner cylinder is smooth and grooved, five different flow regimes can be determined: Taylor vortex flow (TVF), wavy vortex flow (WVF), and Modulated Wavy vortex flow (MWVF). Each time the flow passes from one hydrodynamic regime to another until it enters a state of turbulence, which is characterized by the destruction of all the symmetries that existed at the beginning. In addition, when an axial flow is imposed on a Taylor-Couette flow, new helical vortex structures are observed in both cases (with and without surface groove). The influence of surface structures (grooves) on the shear stress of the wall is discussed with and without axial base flow. A spatio-temporal description of several flow models was obtained using firstly, a visualization’s qualitative study using kalliroscope particles. Secondly, a quantitative study by polarography using simple probes have been used to characterize the impact of vortex structures on the Couette-Taylor flows without and with an axial flow on the transfer.

The purpose of this work is to model turbulent Taylor-Couette-Poiseuille flows submitted to a temperature gradient. These flows are relevant in many industrial applications including rotating machineries and more especially for the effective cooling of electric motors. Several turbulence closures (k-ω SST, RSM and LES) are first compared in the isothermal case and validated against the reliable experimental data of Escudier and Gouldson [1]. A detailed analysis of the coherent structures within the boundary layers is proposed. The model offering the best compromise between computational cost and accuracy is then used to perform more computations in the configuration with a temperature gradient considered by Kuosa et al. [2]. In their system, the air flow enters the rotor-stator cavity radially. Correlations for the average Nusselt numbers along the rotor and stator as a function of the control parameters (rotation rate, air flow rate, Prandtl number) are provided and compared with data available in the literature [3].

This paper presents the results of fluid flow and convection heat transfer in concentric and eccentric annuli between two cylinders using a three-dimensional computational fluid dynamics model. Effects of rotational speed ( n = 0, 150, 300, and 400 rpm) and eccentricity (ε = 0, 0.15, 0.3, 0.45, and 0.6) on axial and tangential velocity distribution, pressure drop and forced convection heat transfer are investigated for radii ratios (η) of 0.2, 0.4, 0.6, and 0.8, Reynolds number 2.0 × 103–1.236 × 105, Taylor number 1.47 × 106–1.6 × 1010, and Prandtl number 3.71–6.94. The parameters cover many applications, including rotary heat exchangers, mixers, agitators, etc. Nusselt numbers and friction factors for stationary and rotated concentric and eccentric annuli are correlated with four dimensionless numbers. The results revealed that when the speed of the inner cylinder increases from 0 to 400 rpm, the friction factor increases by 7.7%–103% for concentric and 8.2%–148% for eccentric annuli, whereas Nusselt number enhances by 37%–333% for concentric and 44%–340% for eccentric annuli. The radius ratio has a substantial effect on the heat transfer and pressure drop in annuli. The eccentricity enhances the heat transfer up to 12%, whereas its effect on the friction factor is not monotonic as it depends on Reynolds number, radii ratios, and rotational speed.

This work experimentally investigates the heat transfer characteristics of Taylor–Couette–Poiseuille flow in an annular channel by mounting longitudinal ribs on the rotating inner cylinder. The ranges of the axial Reynolds number (Re) and the rotational Reynolds number (ReΩ) are Re = 30–1200 and ReΩ = 0–2922, respectively. Three modes of the inner cylinder without/with longitudinal ribs are considered. A special entry and exit design for the axial coolant flow reveals some interesting findings. The value of Nusselt number (Nu) is almost minimal at the inlet of the annular channel, and then sharply rises in the axial direction. The average Nusselt number ( Nu ¯ ) increases with Re. Nu increases rapidly with ReΩ at low Re (such as at Re = 30 and 60) but that the effect of ReΩ decreases as the value increases (such as at Re = 300–1200). The ratio Nu ¯ / Nu ¯ 0 increases with ReΩ and exceed two at all Re and in the test modes. The heat transfer is typically promoted by mounting longitudinal ribs on the rotating inner cylinder, especially at Re = 300 and 600. When Re = 300 or 600 and ReΩ > 2000, the Nu ¯ of the system with ribs reaches around 1.4 times that of Nu ¯ A ( Nu ¯ in mode A). Under a given pumping power constraint (PRe3), the Nu ¯ of the system with ribs (modes B and C) generally exceeds that without ribs (mode A), while the difference between the values of Nu ¯ in modes B and A slowly falls as PRe3 increases. Additionally, mode B (with ribs) is preferred for high heat transfer when PRe3 4.5 × 1013.

Turbulent flows in an opened Taylor-Couette system with an axial throughflow is studied here by the means of large eddy simulations. The ultimate industrial application is the effective cooling of the rotor-stator gap of an electrical motor.

The vortex structure of immiscible liquid-liquid Taylor-Couette-Poiseuille flow was studied using photographic techniques. Several parameters were considered, including the feed composition and the inner cylinder rotation rate. For certain feed compositions and sufficiently large rotation rates a translating banded structure, which consisted of alternating aqueous and organic-rich vortices, persisted indefinitely. At lower rotation rates, either a spatially homogeneous emulsion evolved or sustained oscillations between the banded and homogeneous structures developed.

In this article, we derive a rigorous characterization of the boundary-layer and interior separations in the Taylor-Couette-Poiseuille (TCP) flow. The results obtained provide a rigorous characterization on how, when and where the propagating Taylor vortices (PTV) are generated. In particular, contrary to what is commonly believed, we show that the PTV do not appear after the first dynamical bifurcation, and they appear only when the Taylor number is further increased to cross another critical value so that a structural bifurcation occurs. This structural bifurcation corresponds to the boundary-layer and interior separations of the flow structure in the physical space.