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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.
Thermal conduction is the diffusion of thermal energy (heat) within one material or between materials in contact. The higher temperature object has molecules with more kinetic energy; collisions between molecules distributes this kinetic energy until an object has the same kinetic energy throughout.
Very high thermal conductivity measurements up to 22,600 w m −1 K −1 were reported by Fenton, E.W., Rogers, J.S. and Woods, S.D. in reference 570 on page 1458, 41, 2026–33, 1963. The data is listed on pages 6 through 8 and graphed on page 1 where Fenton and company are on curves 63 and 64.
is the thermal diffusivity, a material-specific quantity depending on the thermal conductivity, the specific heat capacity, and the mass density. The heat equation is a consequence of Fourier's law of conduction (see heat conduction ).
The thermal conductivity of a material is a measure of its ability to conduct heat.It is commonly denoted by , , or and is measured in W·m −1 ·K −1.. Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal conductivity.
A 2008 review paper written by Philips researcher Clemens J. M. Lasance notes that: "Although there is an analogy between heat flow by conduction (Fourier's law) and the flow of an electric current (Ohm’s law), the corresponding physical properties of thermal conductivity and electrical conductivity conspire to make the behavior of heat flow ...
The value of the Biot number can indicate the applicability (or inapplicability) of certain methods of solving transient heat transfer problems. For example, a Biot number smaller than about 0.1 implies that heat conduction inside the body offers much lower thermal resistance than the heat convection at the surface, so that temperature ...
Chapman–Enskog theory also predicts a simple relation between thermal conductivity, , and viscosity, , in the form =, where is the specific heat at constant volume and is a purely numerical factor. For spherically symmetric molecules, its value is predicted to be very close to 2.5 {\displaystyle 2.5} in a slightly model-dependent way.