Study on Laminar Natural Convection Heat Transfer from a Hemisphere with Uniform Heat Flux Surface

• Published in: Journal of thermal science Vol. 28; no. 2; pp. 232 - 245
• Main Authors: Zhang, Jian, Liu, Jie, Lu, Wenqiang
• Format: Journal Article
• Language: English
• Published: Heidelberg Science Press 01.04.2019; Springer Nature B.V
• Subjects: Adiabatic flow; Boundary conditions; Classical and Continuum Physics; Coefficient of friction; Computational fluid dynamics; Curvature; Dependence; Drag coefficients; Engineering Fluid Dynamics; Engineering Thermodynamics; Fluid flow; Free convection; Grashof number; Heat and Mass Transfer; Heat flux; Heat transfer; Heating; Laminar heat transfer; Mathematical models; Physics; Physics and Astronomy; Pressure drag; Temperature profiles; Viscosity; natural convection; hemisphere; heat transfer correlations; uniform heat flux; numerical simulation
• ISSN: 1003-2169; 1993-033X
• DOI: 10.1007/s11630-018-1051-y

By employing the modified model based on Bejan et al., laminar natural convection heat transfer from a hemisphere with uniform heat flux surface has been numerically investigated. Extensive results of two different surface boundary conditions are obtained for a wide range of Grashof numbers (10 ≤ Gr ≤ 10 7 ) and Prandlt number of 0.72. The characteristics of heat transfer and fluid flow are analyzed in terms of isotherm contours and streamline patterns, radial and tangential velocities, dimensionless temperature profiles, local friction and pressure drag coefficients, as well as local and average Nusselt numbers. Meanwhile, the effects of Grashof number and adiabatic surface on flow motion and heat transfer have been studied. No recirculation zone or flow separation generates over the top of the hemisphere compared to the isothermal sphere. Owing to the curvature effect, the maximum values of local friction and pressure drag coefficients appear at the corner point B. Comparisons with the previous results are also reported in detail. All the results are in good agreement with the numerical data. Moreover, both local and average Nusselt numbers show a positive dependence on Grashof number. The values of the non-adiabatic case are smaller than that of the adiabatic case due to the preheating effect. Finally, two precise and general correlations of average Nusselt number varying with Grashof numbers have been presented, which can provide an effective prediction for the heat transfer rate in engineering applications, and offer academic values for the future research.