TY - JOUR

T1 - A numerical analysis of free convection around an isothermal sphere. Effects of space and prandtl number

AU - Takamatsu, Hiroshi

AU - Fujii, Motoo

AU - Fujii, Tetsu

PY - 1987

Y1 - 1987

N2 - Numerical solutions of full Navier-Stokes and energy equations for two dimensional laminar free convection between two concentric spheres are obtained for Pr=0.7~120, Ra=1~103 and radius ratios of outer to inner spheres r2/r1=560. With decrease of r2/r1, the heat transfer coefficient for the inner sp. here decreases first due to suppression of convective flow and then increases as the conduction heat transfer becomes predominant. For Pr=0.7 and Ra=1, the heat transfer coefficient at r2/r1≥60 can be regarded as that for a single sphere immersed in an infinite medium. The higher the Rayleigh number, the smaller the radius ratio at which the Nusselt number can be regarded as that for a single sp. here. An accurate expression of the Nusselt number is proposed. An expression for the relation among drag force induced by free convection flow, Rayleigh number and Prandtl number is also presented.

AB - Numerical solutions of full Navier-Stokes and energy equations for two dimensional laminar free convection between two concentric spheres are obtained for Pr=0.7~120, Ra=1~103 and radius ratios of outer to inner spheres r2/r1=560. With decrease of r2/r1, the heat transfer coefficient for the inner sp. here decreases first due to suppression of convective flow and then increases as the conduction heat transfer becomes predominant. For Pr=0.7 and Ra=1, the heat transfer coefficient at r2/r1≥60 can be regarded as that for a single sphere immersed in an infinite medium. The higher the Rayleigh number, the smaller the radius ratio at which the Nusselt number can be regarded as that for a single sp. here. An accurate expression of the Nusselt number is proposed. An expression for the relation among drag force induced by free convection flow, Rayleigh number and Prandtl number is also presented.

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U2 - 10.1299/kikaib.53.1314

DO - 10.1299/kikaib.53.1314

M3 - Article

AN - SCOPUS:0023331423

VL - 53

SP - 1314

EP - 1319

JO - Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B

JF - Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B

SN - 0387-5016

IS - 488

ER -