Heat penetration coefficient

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The heat penetration coefficient is a material-specific characteristic value from thermodynamics , which is specified in the unit :

With

If two halbunendlich expanded bodies with different initial temperatures and brought into perfect thermal contact, it can contacting temperature (the temperature of the contact surface. E.) With the heat penetration coefficient , and the two substances are determined:

This formula can also be used to estimate the initial contact temperature of finite bodies.

The heat penetration coefficient can be practically experienced if you touch different substances at the same temperature with your bare hand:

  • Substances with a high heat penetration coefficient (e.g. metals ) are perceived as particularly cold if their temperature is below that of the skin.
  • Substances with a low heat penetration coefficient (e.g. insulation materials or wood ), on the other hand, are perceived as warmer at the same temperature.

The same applies when the body is warmer than the skin.

Heat penetration coefficient of some substances
material
Insulation material ( mineral fibers ) 0.06
cork 0.10
Wood 0.4 ... 0.5
rubber 0.6
human skin 1.0 ... 1.3
Glass 1.3 ... 1.5
water 1.6
concrete 1.8 ... 2.2
steel 14.0
copper 36.0

A related quantity is the thermal diffusivity .

literature

  • Wolfgang M. Willems, Kai Schild: Thermal protection. Basics - calculation - evaluation, 2nd edition, Springer Fachmedien, Wiesbaden 2013, ISBN 978-3-658-02570-0 .

Individual evidence

  1. Hans Dieter Baehr, Karl Stephan: Heat and mass transfer . 4th edition Springer, Berlin 2004, p. 172, ISBN 3-540-40130-X

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