Effect of temperature-dependent viscosity on forced convection heat transfer from a cylinder in crossflow of power-law fluids |
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| Authors: | AA Soares JM Ferreira L Caramelo J Anacleto RP Chhabra |
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| Affiliation: | 1. Departamento de Física, Universidade de Trás-os-Montes e Alto Douro, Apartado 1013, 5001-801 Vila Real, Portugal;2. CITAB/UTAD, Quinta de Prados, Apartado 1013, 5001-801 Vila Real, Portugal;3. IFIMUP and IN – Institute of Nanotechnology, Departamento de Fisica da Faculdade de Ciencias da Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal;4. Department of Chemical Engineering, Indian Institute of Technology, Kanpur 208 016, India;1. State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling 712100, China;2. Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, Huazhong Agricultural University, Wuhan 430070, China;3. University of Chinese Academy of Sciences, Beijing 100049, China;1. School of Information Science and Technology, Zhanjiang Normal University, Zhanjiang 524048, China;2. State Key Laboratory of Software Engineering, Wuhan University, Wuhan 430079, China |
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| Abstract: | The steady, two-dimensional and incompressible flow of power-law fluids across an unconfined isothermal heated circular cylinder is investigated numerically to ascertain the effect of temperature-dependent viscosity on the flow and forced convection heat transfer phenomena. Extensive numerical results elucidating the variation of the heat transfer characteristics and drag coefficient on the severity of temperature dependence of viscosity (0 ? b ? 0.5), power law index (0.6 ? n ? 1.6), Prandtl number (1 ? Pr ? 100) and Reynolds number (1 ? Re ? 30) are presented. The coupled momentum and energy equations are expressed in the stream function/vorticity formulation and solved using a second-order accurate finite difference method to determine the local and surface-averaged Nusselt numbers, the drag coefficient, and to map the flow domain in terms of the temperature and flow fields near the cylinder. The variation of viscosity with temperature is shown to have a substantial effect on both the local and surface-averaged values of the Nusselt number. As expected, the results also suggest that the rate of heat transfer shows positive dependence on the Reynolds number and Prandtl number. Furthermore, stronger the dependence of viscosity on the temperature, the greater is the enhancement in the rate of heat transfer. Finally, all else being equal, shear-thinning fluid behaviour facilitates heat transfer while the shear-thickening behaviour has deleterious effect on heat transfer. |
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