## Abstract

Numerical solutions of full Navier-Stokes and energy equations for two dimensional laminar free convection between two concentric spheres are obtained for Pr equals 0. 7 to approximately 120, Ra equals 1 to approximately 10**3 and radius ratios of the outer to inner sphere r//2/r//1 equals 5 to approximately 60. With decrease of r//2/r//1 the heat transfer coefficient for the inner sphere decreases first due to suppression of convective flow and transfer. The heat transfer coefficient at r//2/r//1 greater than equivalent to 60 can be regarded as that for a single sphere immersed in an infinite medium for Pr equals 0. 7 and Ra equals 1. The higher the Rayleigh number, the smaller is the radius ratio at which Nusselt number can be regarded as that for a single sphere. An accurate correlation equation for the Nusselt number is proposed. A correlation equation for the relation among drag forces induced by free convection flow, Rayleigh number and Prandtl number is also presented.

Original language | English |
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Pages | 55-60 |

Number of pages | 6 |

Publication status | Published - 1987 |

## All Science Journal Classification (ASJC) codes

- Engineering(all)