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In heat transfer, the thermal conductivity of a substance, k, is an intensive property that indicates its ability to conduct heat. For most materials, the amount of heat conducted varies (usually non-linearly) with temperature. [1] Thermal conductivity is often measured with laser flash analysis. Alternative measurements are also established.
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.
An example of a new source of heat "turning on" within an object, causing transient conduction, is an engine starting in an automobile. In this case, the transient thermal conduction phase for the entire machine is over, and the steady-state phase appears, as soon as the engine reaches steady-state operating temperature .
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 gaseous and liquid nonmetals have very low densities, melting and boiling points, and are poor conductors of heat and electricity. [20] The solid nonmetals have low densities and low mechanical strength (being either hard and brittle, or soft and crumbly), [ 21 ] and a wide range of electrical conductivity.
Thermal contact resistance is significant and may dominate for good heat conductors such as metals but can be neglected for poor heat conductors such as insulators. [2] Thermal contact conductance is an important factor in a variety of applications, largely because many physical systems contain a mechanical combination of two materials.
These intumescent materials produce a light char which is a poor conductor of heat, thus retarding heat transfer.Typically the light char consists of microporous carbonaceous foam formed by a chemical reaction of three main components: ammonium polyphosphate, pentaerythritol, and melamine. [2]
Typically, this is a course grained sand or organic material. The sand is quite porous which makes it a poor conductor of heat. During extreme wind events, this sand or organic matter is carried onto the snow patch. The snow lying underneath the porous sand is protected from the heat and does not erode away.