In
heat transfer
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, ...
, the thermal conductivity of a substance, ''k'', is an
intensive property
Physical properties of materials and systems can often be categorized as being either intensive or extensive, according to how the property changes when the size (or extent) of the system changes. According to IUPAC, an intensive quantity is on ...
that indicates its ability to conduct
heat
In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is al ...
. For most materials, the amount of heat conducted varies (usually non-linearly) with temperature.
Thermal conductivity
The thermal conductivity of a material is a measure of its ability to conduct heat. It is commonly denoted by k, \lambda, or \kappa.
Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal ...
is often measured with
laser flash analysis
The laser flash analysis or laser flash method is used to measure thermal diffusivity of a variety of different materials. An energy pulse heats one side of a plane-parallel sample and the resulting time dependent temperature rise on the backsid ...
. Alternative
measurements
Measurement is the quantification of attributes of an object or event, which can be used to compare with other objects or events.
In other words, measurement is a process of determining how large or small a physical quantity is as compared t ...
are also established.
Mixtures may have variable thermal conductivities due to composition. Note that for gases in usual conditions, heat transfer by
advection
In the field of physics, engineering, and earth sciences, advection is the transport of a substance or quantity by bulk motion of a fluid. The properties of that substance are carried with it. Generally the majority of the advected substance is al ...
(caused by
convection
Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the convec ...
or
turbulence
In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to a laminar flow, which occurs when a fluid flows in parallel layers, with no disruption between ...
for instance) is the dominant mechanism compared to
conduction
Conductor or conduction may refer to:
Music
* Conductor (music), a person who leads a musical ensemble, such as an orchestra.
* Conductor (album), ''Conductor'' (album), an album by indie rock band The Comas
* Conduction, a type of structured f ...
.
This table shows thermal conductivity in
SI units
The International System of Units, known by the international abbreviation SI in all languages and sometimes Pleonasm#Acronyms and initialisms, pleonastically as the SI system, is the modern form of the metric system and the world's most wid ...
of watts per metre-kelvin (W·m
−1·K
−1). Some measurements use the imperial unit
BTU
The British thermal unit (BTU or Btu) is a unit of heat; it is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. It is also part of the United States customary units. The modern SI u ...
s per foot per hour per degree Fahrenheit ( =
Sortable list
This concerns materials at atmospheric pressure and around .
Analytical list
Thermal conductivities have been measured with longitudinal heat flow methods where the experimental arrangement is so designed to accommodate heat flow in only the axial direction, temperatures are constant, and radial heat loss is prevented or minimized. For the sake of simplicity the conductivities that are found by that method in all of its variations are noted as L conductivities, those that are found by radial measurements of the sort are noted as R conductivities, and those that are found from periodic or transient heat flow are distinguished as P conductivities. Numerous variations of all of the above and various other methods have been discussed by some G. K. White, M. J. Laubits, D. R. Flynn, B. O. Peirce and R. W. Wilson and various other theorists who are noted in an international Data Series from Purdue University, Volume I pages 14a–38a.
This concerns materials at various temperatures and pressures.
See also
*
Laser flash analysis
The laser flash analysis or laser flash method is used to measure thermal diffusivity of a variety of different materials. An energy pulse heats one side of a plane-parallel sample and the resulting time dependent temperature rise on the backsid ...
*
List of insulation material
This is a list of insulation materials used around the world.
Typical R-values are given for various materials and structures as approximations based on the average of available figures and are sorted by lowest value.'' R-value at 1 n'' giv ...
*
R-value (insulation)
In the context of construction, the R-value is a measure of how well a two-dimensional barrier, such as a layer of insulation, a window or a complete wall or ceiling, resists the conductive flow of heat. R-value is the temperature difference per ...
*
Thermal transmittance U-factor or U-value
*
Specific heat capacity
In thermodynamics, the specific heat capacity (symbol ) of a substance is the heat capacity of a sample of the substance divided by the mass of the sample, also sometimes referred to as massic heat capacity. Informally, it is the amount of heat t ...
*
Thermal conductivity
The thermal conductivity of a material is a measure of its ability to conduct heat. It is commonly denoted by k, \lambda, or \kappa.
Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal ...
*
Thermal conductivities of the elements (data page)
Thermal conductivity
Notes
* Ref. CRC: Values refer to 27 °C unless noted.
* Ref. CR2: Values refer to 300 K and a pressure of "100 kPa (1 bar)", or to the saturation vapor pressure if that is less than 100 kPa. The notation (P=0) denotes ...
*
Thermal diffusivity
In heat transfer analysis, thermal diffusivity is the thermal conductivity divided by density and specific heat capacity at constant pressure. It measures the rate of transfer of heat of a material from the hot end to the cold end. It has the SI ...
*
Thermodynamics
Thermodynamics is a branch of physics that deals with heat, work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these quantities is governed by the four laws of the ...
References
Bibliography
*
External links
Heat Conduction Calculator*
ttp://www.electronics-cooling.com/2006/08/thermal-conductivity-of-solders/ Thermal Conductivities of Solders* Thermal conductivity of air as a function of temperature can be found a
James Ierardi's Fire Protection Engineering Site* Non-Metallic Solids: The thermal conductivities of non-metallic solids are found in about 1286 pages in the TPRC Data Series volume 2 at the PDF link here (Identifier ADA951936): http://www.dtic.mil/docs/citations/ADA951936 with full text link https://apps.dtic.mil/dtic/tr/fulltext/u2/a951936.pdf retrieved February 2, 2019 at 10:15 PM EST.
* Gasses and Liquids: The thermal conductivities of gasses and liquids are found in the TPRC Data Series volume 3 at the PDF link here (Identifier ADA951937): http://www.dtic.mil/docs/citations/ADA951937 with full text link https://apps.dtic.mil/dtic/tr/fulltext/u2/a951937.pdf retrieved February 2, 2019 at 10:19 PM EST.
* Metals and Alloys: The thermal conductivities of metals are found in about 1595 pages in the TPRC Data Series volume 1 at the PDF link here: http://www.dtic.mil/docs/citations/ADA951935 with full text link https://apps.dtic.mil/dtic/tr/fulltext/u2/a951935.pdf retrieved February 2, 2019 at 10:20 PM EST.
* Specific Heat and Thermal Radiation: Primary sources are found in the TPRC data series volumes 4 — 9, links: https://apps.dtic.mil/dtic/tr/fulltext/u2/a951938.pdf, https://apps.dtic.mil/dtic/tr/fulltext/u2/a951939.pdf, https://apps.dtic.mil/dtic/tr/fulltext/u2/a951940.pdf, https://apps.dtic.mil/dtic/tr/fulltext/u2/a951941.pdf, https://apps.dtic.mil/dtic/tr/fulltext/u2/a951942.pdf and https://apps.dtic.mil/dtic/tr/fulltext/u2/a951943.pdf retrieved at various times February 2 and 3, 2019.
* Vacuums: Vacuums and various levels of vacuums and the thermal conductivities of air at reduced pressures are known at http://www.electronics-cooling.com/2002/11/the-thermal-conductivity-of-air-at-reduced-pressures-and-length-scales/ retrieved February 2, 2019 at 10:44 PM EST.
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