### Abstract

Numerical solutions of full Navier-Stokes and energy equations for two dimensional laminar free convection between two concentric spheres are obtained for P_{r}=0.7~120, R_{a}=1~103 and radius ratios of outer to inner spheres r_{2}/r_{1}=560. With decrease of r_{2}/r_{1}, 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 P_{r}=0.7 and R_{a}=1, the heat transfer coefficient at r_{2}/r_{1}≥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.

Original language | English |
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Pages (from-to) | 1314-1319 |

Number of pages | 6 |

Journal | Transactions of the Japan Society of Mechanical Engineers Series B |

Volume | 53 |

Issue number | 488 |

DOIs | |

Publication status | Published - Jan 1 1987 |

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### All Science Journal Classification (ASJC) codes

- Condensed Matter Physics
- Mechanical Engineering

### Cite this

*Transactions of the Japan Society of Mechanical Engineers Series B*,

*53*(488), 1314-1319. https://doi.org/10.1299/kikaib.53.1314