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The Be number plays in forced convection the same role that the Rayleigh number plays in natural convection. In the context of mass transfer. the Bejan number is the dimensionless pressure drop along a channel of length : [4] {\displaystyle \mathrm {Be} = {\frac {\Delta p\,L^ {2}} {\mu D}}} where. is the dynamic viscosity.
The Nusselt number is the ratio of total heat transfer (convection + conduction) to conductive heat transfer across a boundary. The convection and conduction heat flows are parallel to each other and to the surface normal of the boundary surface, and are all perpendicular to the mean fluid flow in the simple case.
Dimensionless numbers (or characteristic numbers) have an important role in analyzing the behavior of fluids and their flow as well as in other transport phenomena. [1] They include the Reynolds and the Mach numbers, which describe as ratios the relative magnitude of fluid and physical system characteristics, such as density, viscosity, speed of sound, and flow speed.
A hot, less-dense material at the bottom moves upwards, and likewise, cold material from the top moves downwards. Convection (or convective heat transfer) is the transfer of heat from one place to another due to the movement of fluid. Although often discussed as a distinct method of heat transfer, convective heat transfer involves the combined ...
Adrian Bejan is a Romanian-American professor who has made contributions to modern thermodynamics and developed his constructal law. He is J. A. Jones Distinguished Professor of Mechanical Engineering at Duke University [1] [2] and author of the books Design in Nature, [3] The Physics of Life [4], Freedom and Evolution [5] and Time And Beauty. [6]
In fluid mechanics, the Rayleigh number (Ra, after Lord Rayleigh [1]) for a fluid is a dimensionless number associated with buoyancy -driven flow, also known as free (or natural) convection. [2][3][4] It characterises the fluid's flow regime: [5] a value in a certain lower range denotes laminar flow; a value in a higher range, turbulent flow.
Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, thermal convection, thermal radiation, and transfer of energy by phase changes.
In fluid mechanics (especially fluid thermodynamics), the Grashof number (Gr, after Franz Grashof [a]) is a dimensionless number which approximates the ratio of the buoyancy to viscous forces acting on a fluid. It frequently arises in the study of situations involving natural convection and is analogous to the Reynolds number (Re).