关于热力学、热量传递和质量传递,以及流体工程的 A-Z 指南
中文 English Русский Português Español Français Deutsch 关于我们 编辑 联系我们 访问 Begell House
View in A-Z Index

Rayleigh number, Ra, is a dimensionless term used in the calculation of natural convection.

where g is acceleration due to gravity, β' is coefficient of thermal expansion of the fluid, ΔT is temperature difference, x is length, ν is kinematic viscosity and κ is thermal diffusivity of the fluid. Gr is the Grashof Number and Pr is the Prandtl Number.

The magnitude of the Rayleigh number is a good indication as to whether the natural convection boundary layer is laminar or turbulent. For a vertical surface, for example, the transition takes place when Ra ≈ 109. Various examples of the relationship between the magnitude of natural convective heat transfer and Rayleigh number are given in the following reference.

REFERENCES

Hewitt, G. F., Shires, G. L. and Bott, T. R. (1994) Process Heat Transfer, CRC Press.

References

  1. Hewitt, G. F., Shires, G. L. and Bott, T. R. (1994) Process Heat Transfer, CRC Press.
浏览次数: 80145 创建日期: 2 February 2011 最后修改日期: 7 February 2011 © Copyright 2010-3921 返回顶部
A-Z 索引 作者/编辑 语义地图 视觉画廊 贡献 Guest