Non-metallic materials such as brick stone and brick are good absorbers of solar energy, especially if they have dark coloring. Material with low thermal conductivity insulators they do not absorb or transfer heat.
what is the exact physics behind it?
Ashish
Insulators have low thermal conductivity (W/m.K), so they are bad in conducting heat. The conduction heat transfer within a material is due to the molecules' motion, vibration, rotation, etc.
However, radiation heat transfer is different. It is due to electromagnetic waves. It depends on surface properties of the objects emissivity that can have a value from 0 (shiny mirror) to 1.0 (blackbody)
Dear Ahmad,
This depends on the reflection or absorption capacity of metals.
The electrons in metal are delocalised electrons and are free moving electrons so when they gain energy (heat) they vibrate more quickly and can move around, this means that they can pass on the energy more quickly so conduction is high for some metal. Some metals they do not hence they have less conduction. So they cannot transfer heat faster.
Ashish
The absorption of radiation in solids is a surface phenomenon. A rough black surface will have very high absorptivity for the solar radiation. If you like less absorption of the solar radiation, paint the surface white with a very smooth glossy finish of the surface.
All materials have some thermal conductivity; the metals have very high thermal conductivity while the insulators have very poor conductivity. The building materials' thermal conductivity lies in between but much smaller than the metals. For a wall exposed to the solar radiation, the temperature of the other side of the wall depends both on thermal conductivity and the heat capacity of the material of the wall (the two properties are combined as diffusivity).
However, I have not understood objective of your present project, i.e. whether you want to transfer the heat or retard it's transmission.
Dear Rajendra,
True.
Concept is thermal conductivity.
I was expecting more on the electron movement how it yield more absorption or less absorption in the metal they cause the heat transfer. are high electron movement or transfer will yield less absorption or high absorption?
Ashish
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