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Nusselt number. In thermal fluid dynamics, the Nusselt number (Nu, after Wilhelm Nusselt [1]: 336 ) is the ratio of total heat transfer to conductive heat transfer at a boundary in a fluid. Total heat transfer combines conduction and convection. Convection includes both advection (fluid motion) and diffusion (conduction).
These first Heisler–Gröber charts were based upon the first term of the exact Fourier series solution for an infinite plane wall: (,) = = [ + ], [1]where T i is the initial uniform temperature of the slab, T ∞ is the constant environmental temperature imposed at the boundary, x is the location in the plane wall, λ is the root of λ * tan λ = Bi, and α is thermal diffusivity.
Grashof number. 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).
The Churchill–Bernstein equation is a correlation and cannot be derived from principles of fluid dynamics. The equation yields the surface averaged Nusselt number, which is used to determine the average convective heat transfer coefficient. Newton's law of cooling (in the form of heat loss per surface area being equal to heat transfer ...
The Rayleigh number is defined as the product of the Grashof number (Gr), which describes the relationship between buoyancy and viscosity within a fluid, and the Prandtl number (Pr), which describes the relationship between momentum diffusivity and thermal diffusivity: Ra = Gr × Pr. [4][3] Hence it may also be viewed as the ratio of buoyancy ...
Dropwise condensation is useful in powerplant heat exchangers, thermal desalination, self-cleaning surfaces, and heating and air conditioning. The total amount of heat transfer through a single droplet is a function of its radius and the size distribution over the condensation surface. The important factors which are involved in the mechanism ...
The general definition of the heat transfer coefficient is: where: : heat flux (W/m²); i.e., thermal power per unit area, : difference in temperature between the solid surface and surrounding fluid area (K) The heat transfer coefficient is the reciprocal of thermal insulance. This is used for building materials (R-value) and for clothing ...
Heat transfer physics describes the kinetics of energy storage, transport, and energy transformation by principal energy carriers: phonons (lattice vibration waves), electrons, fluid particles, and photons. [1][2][3][4][5] Heat is thermal energy stored in temperature-dependent motion of particles including electrons, atomic nuclei, individual ...