Numerical simulation of turbulent natural convection around spheres
Published 2020-10-27
Keywords
- heat transfer,
- natural convection,
- boundary layer,
- laminar zone,
- turbulent zone
- transition,
- Rayleigh number,
- Nusselt number,
- sphere,
- laminar model,
- turbulence model,
- k-ε model,
- Ansys Fluent ...More
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Copyright (c) 2020 Revista UIS Ingenierías
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Abstract
Most of the research that has been done on natural convection has focused its study on the laminar region and not much attention has been focused on the turbulent natural convection, that usually occurs when the Rayleigh number exceeds a certain critical value. Recent studies have shown that the correlations identified for this region are often imprecise. On the other hand, the numerical treatment of this problem presents difficulties related to the turbulence model used, since it is in the presence of a laminar-turbulent boundary layer in a laminar environment, therefore, the laminar model will underestimate the heat transfer, while the turbulent models will overestimate it. Transitional models and other options are available but are designed for turbulent environments. The present work proposes the numerical solution using the Ansys Fluent computer program of turbulent laminar convection around spheres without a turbulence model (laminar model) and using a k-ε turbulence model for low Reynolds numbers. The work should characterize the Rayleigh numbers from which the change from boundary layer to turbulent begins to change, as well as the position of the boundary layer detachment. The values obtained for the heat transfer with the laminar model showed very good agreement with experiments and correlations for low Rayleigh numbers, but lost precision from a certain Rayleigh value, an aspect that could be successfully corrected by incorporating the used turbulence model.
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References
[2] K. Kitamura, A. Mitsuishi, T. Suzuki, T. Misumi, “Fluid flow and heat transfer of high-Rayleigh-number natural convection around heated spheres,” International Journal of Heat and Mass Transfer, vol. 86, pp. 149-157, 2015, doi: 10.1016/j.ijheatmasstransfer.2015.02.081
[3] W. Amato, C. Tien, “Free convection heat transfer from isothermal spheres in water,” International Journal of Heat and Mass Transfer, vol. 15, no. 2, pp. 327-339, 1972, doi: 10.1016/0017-9310(72)90078-6
[4] B. Launder, D. Spalding, “The numerical computation of turbulent flows,” Computer Methods in Applied Mechanics and Engineering, vol. 3, no. 2, pp. 269-289, 1974, doi: 10.1016/0045-7825(74)90029-2
[5] D. Wilcox, “Formulation of the k-ω turbulence model revisited,” AIAA Journal, vol. 46, pp. 2823-2838, 2008, doi: 10.2514/1.36541
[6] F. Menter, “Two-equation Eddy-viscosity turbulence models for engineering applications,” AIAA Journal, vol. 32, no. 2, pp. 1598-1605, 1994, doi: 10.2514/3.12149
[7] R. Lantry, “A correlation-based transition model using local variables for unstructured parallelized CFD code,” Tesis doctoral, Universidad de Stuttgart, Alemania, 2006.
[8] S. Dmitriev, A. Kozelkov, A. Kurkin, N. Tarasova, V. Efremov, V. Kurulin, R. Shamin, M. Legchanov, “Simulation of turbulent convection at high Rayleigh numbers,” Modelling and Simulation in Engineering, vol. 2018, pp. 1-12, 2018, doi: 10.1155/2018/5781602
[9] A. Filippov, “Numerical simulation of experiments on turbulent natural convection of heat generating liquid in cylindrical pool,” Journal of Engineering Thermophysics, vol. 20 no. 1, pp. 64-76, 2011, doi: 10.1134/S1810232811010061
[10] S. Yang, V. Raghavan, G. Gogos, “Numerical study of transient laminar natural convection over an isothermal sphere,” International Journal of Heat and Fluid Flow, vol. 28, pp. 821-837, 2007, doi: 10.1016/j.ijheatfluidflow.2006.08.004
[11] A. Abir, M. Emin, “A comparative study of four low-Reynolds-number k-ε turbulence models for periodic fully developed duct flow and heat transfer,” Numerical Heat Transfer, Part B: Fundamentals, vol. 69, no. 3, pp. 234-248, 2016, doi: 10407790.2015.1097141
[12] Q. Wang, W. Li, Z. Chen, D. Kukulka, “Numerical analysis on natural convection in varios enclosures,” Numerical Heat Transfer, Part A: Applications, vol. 77, no. 4, pp.391-408, 2020, doi: 10.1016/j.ijthermalsci.2007.10.018
[13] F. Mebarek, R. Bessaih, “Numerical simulation of natural convection heat transfer of copper-watr nanofluid in a vertical cylindrical annulus with heat sources,” Thermophysics and Aeromechanics, vol. 26, pp. 325-334, 2019, doi: 10.1134/S0869864319030028
[14] Q. Yu, C. Zhang, Y. Wu, B. Sunden, “Experimental and numerical study of natural convection in botton-heated cylindrical cavity filled with molten salt nanofluids,” Journal of Thermal Analysis and Calorimetry, vo. 141, pp. 1207-1219, 2020, doi: 10.1007/s10973-019-09112-9
[15] K. Abe, T. Kondoh, Y. Nagano, “A new turbulence model for predicting fluid flow and heat transfer in separating and reattaching flows – I. flow field calculations,” International Journal of Heat and Mass Transfer, vol. 37, pp. 139-151, 1994, doi: 10.1016/0017-9310(94)00252-Q
[16] R. Arévalo, A. Abánades, L. Rebollo, “Numerical research of film boiling heat transfer around a vertical short cylinder flat or hemispherical ends,” Journal of Heat Transfer, vol. 138, pp. 1-7, 2016, doi: 10.1115/1.4033094
[17] R. Arévalo, D. Antúnez, L. Rebollo, A. Abánades, “Estimation of radiation coupling factors in film boiling around spheres by mean of computational fluid dynamics (CFD) tools,” International Journal of Heat and Mass Transfer, vol. 78, pp. 84-89, 2014, doi: 10.1016/j.ijheatmasstransfer.2014.06.063
[18] A. Abánades, R. Arévalo, L. Rebollo, “Numerical prediction of the mean temperature of the vapor film in film boiling heat transfer,” Computational Thermal Sciences, vol. 8, no. 1, pp. 1-10, 2016, doi: 10.1615/ComputThermalScien.2015014392