Numerical Study of Turbulent Mixed Convection Heat Transfer in a Semi-Circle Cavity Contains a Rotating Cylinder (original) (raw)
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Experimental Study of Mixed Convection in a Cavity with a Rotating Cylinder
Journal of Advanced Research in Fluid Mechanics and Thermal Sciences, 2020
Mixed convection in a semicircle enclosure of radius 0.15 m and length 0.75 m is studied experimentally. An insulated rotation cylinder is fixed at the center of the cavity to improve the heat transfer coefficient, the bottom wall of the enclosure is subjected to constant heat flux while the external curved wall is exposed to the ambient temperature. Cavity is placed horizontally and vertically and the angular velocities (62.8,83.73,125.6) rad/s. Results show an improvement of heat transfer coefficient with increasing angular velocity and with the horizontal and vertical cavity positioning.
International Journal of Heat and Mass Transfer
A numerical study has been carried out to investigate the combined forced and natural convection heat transfer in a differentially heated 3D obstructed cavity with a thermally insulated rotating circular cylinder. The cavity has a hot stationary bottom wall and a cold top lid-driven wall, and all the other walls completing the domain are motionless and adiabatic. The simulations are performed for different Reynolds numbers, Re = 5000, 10000, 15000 and 30000, and for dimensionless rotational speeds of the cylinder, 0 ≤ Ω ≤ 10. The performance of two turbulence methods, Large Eddy Simulation (LES) and Unsteady Reynolds-Averaged Navier-Stokes (URANS), has been evaluated in this research. The flow and thermal fields are studied through flow vectors, isotherm contours and iso-surfaces temperature, as well as through the average Nusselt number (Nuav) and velocity components. The results demonstrate clearly that the flow patterns and the thermal fields are influenced strongly by increasing either the rotating cylinder speed or the Reynolds number. Furthermore, both LES and URANS solutions can capture the essential feature of the primary eddies in the cavity. But this study has shown convincing evidence that only the LES method can predict the structure details of the secondary eddies that have profound effects on the heat transfer behaviour within the enclosure.
Heat transfer modelling in a rotating cavity using the SST k-ω turbulence model
Archives of Mechanics
Heat transfer simulation in a cylindrical cavity rotating around its axis and lim-ited by two metal discs were presented. The object of the calculations was to compare the shear stress transport k-ω (SST k-ω) turbulence model with the renormalization group k-ε and k-ω turbulence models. The calculation results were compared with the results of experiments described in literature. Values of the Nusselt number for the cavity walls were compared depending on three dimensionless numbers used to describe heat transfer in a cavity: the Grashof number Gr and the Reynolds numbers Re z and Re Φ . Flow structures in a rotating cavity were compared for selected thermal and flow conditions. The computations were performed using the ANSYS CFX 14 commercial code. Notations a inlet opening radius, mm, b cavity outer radius, mm, d disc thickness, mm , Bo natural convection participation Gr/(Re z) 2 , Gr Grashof number, β 1 ∆T Re 2 Φ , h specific static enthalpy, J/kg I identity tensor, Nu Nusselt n...
Turbulent heat transfer in a rotating cavity
Recent Advances in Computational Mechanics, 2014
The paper is a survey of the authors' results of their numerical investigation of a turbulent flow with heat transfer in a rotating cavity. Computations are performed for different geometrical parameters (aspect ratios L = 25-45, curvature parameters Rm = 1.8) and Reynolds numbers (up to 7 · 10 5 ). Attention is focused on the near wall area that is crucial for modeling purposes. The authors present budget of transport equations, distributions of Kolmogorov and Taylor scales, analysis of structural parameters. The obtained results are compared with the experimental and numerical data published in literature (Kasagi 1999-2003, b, Littell & Eaton 1994 as well as with the theoretical solutions. The computations are performed using SVV (the spectral vanishing viscosity method). Parallelization of the code allows us to perform computations on the meshes with up to 34 million collocation points.
Proceedings of 2nd International Multi-Disciplinary Conference Theme: Integrated Sciences and Technologies, IMDC-IST 2021, 7-9 September 2021, Sakarya, Turkey, 2022
This study examines the influence of a rotating cylinder on heat transmitted by mixed convection in an air-filled square space. The appropriate mathematical models for continuous, incompressible, 2-dimensional, laminar flows with Boussinseq's approach are solved numerically, where constant fluid properties have been used. The most important parameters examined are: the angular velocity (Ω = 0-1000) and the angle of inclination (Ɵ = 0-90 o), the study has been carried out with the Rayleigh number (Ra = 10 4), the Prandtl number (Pr = 0.7). The results show that the streamlines are affected by the angular velocity, where the forced convection becomes dominant at high values of angular velocity. The rotation of the cylinder has an effect on the heat exchange between the walls of the cavity and the fluid. Finally the average Nusselt number is increased with increases of angular velocity and decreases as inclination angles change from horizontal to vertical position. A good agreement has been achieved by comparing the results of this work with other previous work.
Journal of Heat Transfer, 2015
Experimental and numerical results of heat transfer by mixed convection in a ventilated cavity are presented. The results were obtained for a 1.0 m × 1.0 m × 1.0 m cavity. The inlet and outlet dimensions were of 0.08 m × 0.08 m, and the air velocity at the inlet was set to 0.1 and 0.5 m/s. The left wall receives a uniform and constant heat flux whereas the right wall was maintained at a constant temperature. Experimental and numerical results of temperature profiles and heat transfer coefficients are presented and compared. The results showed that the variation of the Rayleigh number increases about 1% the percentage differences between experimental and numerical values, and the maximum percentage differences on heat transfer coefficients are 2.0% for Ra = 2.7 × 108 and 3.0% for Ra = 4.5 × 108.
Flow and heat transfer in a vertical open cavity with turbulent mixed convection is investigated experimentally and numerically. The internal size of the cavity is 1 m  1 m  1.2 m, with liquid nitrogen as the cold source and mica electronic heating plates as the heat source of the experiments. The velocity and temperature fields are obtained by hot-wire anemometry, particle image velocimetry and local temperature sensors for 4.6  10 4 Re 5.9  10 4 and Gr 1.8  10 13 . The secondary upward flow was found to occur near the heated walls. Three two-equation RANS turbulence models, RNG k-ε model, L-B Low Re k-ε model and SST k-u model, are used in the numerical simulation with the same boundary conditions as experiments. Through comparison with experimental data, Low Re k-ε model performs overall the best in the accuracy in solving mixed convection problems in large-scale vertical cavities with strong buoyancy force.
Mixed Convection in a Vented Square Cavity with a Heat Conducting Horizontal Solid Circular Cylinder
A finite element method based computational study of steady laminar mixed convection flow inside a vented square cavity with a heat conducting horizontal solid circular cylinder placed at the center of the cavity is carried out in this paper. The developed mathematical model is governed by the coupled equations of continuity, momentum and energy. The present work simulates practical systems such as cooling of electronic devices, ventilation of building etc. The effects of cylinder size and Richardson number on fluid flow and heat transfer performance are investigated. Richardson number is varied from 0.0 to 5.0 and the cylinder diameter is varied from 0.0 to 0.6. The results for the case of without cylinder are compared to those with cylinder to observe the effects cylinder on the flow and heat transfer inside the cavity. The phenomenon inside the cavity for the case of with and without cylinder is analyzed through streamline and isotherm patterns. It is found that the streamlines, isotherms, average Nusselt number at the heated surface, average temperature of the fluid in the cavity and dimensionless temperature at the cylinder center strongly depend on the Richardson number as well as the diameter of the cylinder.
2018
An experimental study for heat transfer process by mixed convection in the entrance region of annulus with uniformly heated stationary outer cylinder and rotating inner shaft has been carried out. The present study aimed to investigate the local and average heat transfer along the axial distance of outer cylinder in horizontal and vertical positions. The experimental setup consists of an annulus with a radius ratio of 0.37 and outer cylinder with a heated length of 1.12m. The experimental investigation was achieved within Reynolds number ranges from 1000 to 2400 and Taylor number values of 0, 158933, 225269, and 506856. Moreover, the Richardson number ranges between 1.09 (mixed convection) to 0.104 (forced convection) in vertical position, and between 1.05 (mixed convection) to 0.113 (forced convection) in horizontal position. The results showed that the local Nusselt number values increase when the heat flux, Reynolds number and Taylor number increase. It is found that the values o...
Applied Mathematical Modelling
A numerical study has been executed to analyze the effects of Reynolds and Prandtl number on mixed convective flow and heat transfer characteristics inside a ventilated cavity in presence of a heat-generating solid circular obstacle placed at the center. The inlet opening is at the bottom of the left wall, while the outlet one is at the top of the right wall and all the walls of the cavity are considered to be adiabatic. Galerkin weighted residual finite element method is used to solve the governing equations of mass, momentum and energy. Results are presented in terms of streamlines, isotherms, the average Nusselt number, the Drag force and the average fluid temperature in the cavity for different combinations of controlling parameters namely, Reynolds number, Prandtl number and Richardson number. The results indicate that the flow and thermal fields as well as the heat transfer rate, the Drag force and the average fluid temperature in the cavity depend significantly on the mentioned parameters.