Material with Variable Thermal Resistance

[runandrew]

Hello,

 

I am looking if there is a material that has variable thermal resistance as its temperature changes.

 

Please refer to the image below.

 

I am trying to find a material that as heat is added to the outer surface, the inside surface can only reach a desired temperature. So in a sense, the material regulates the temperature at T1.

For example: if the outside surface temperature, T2, was at 80C then inside surface temperature, T1, would be held at 60C at steady state.

 

 

 

 

Thanks,

 

Andrew

[swansont]

A material that undergoes a phase change will behave this way. Add heat to a pot of water and it will stay at 100 ºC (or a block of ice at 0 ºC) and the temperature will stay there until there's no more material in that state. It's possible you could have a solid that undergoes a change from one lattice state to another that behaves somewhat similarly. A change in heat capacity won't limit the temperature, but it would affect the rate of temperature increase. It would also change the mechanical properties.

[cypress]

Outside of what swansont suggested during a dynamic state, there is no material that could stave off a temperature differential as described indefinitely, since that would require unbounded thermal resistance. To maintain steady T2 and T1 temperatures requires heat flux across the T1 boundary and therefore a heat sink in the center white space.

[CaptainPanic]

There is nothing that will keep the heat out forever... nothing at all.

 

If the outside is 80, no matter what kind of fancy solution you find, the inside will eventually (assymptotically) approach 80 degrees as well.

 

The only solution to keep the inside lower than 80 degrees is cooling. A flow of water or air for example, at the right flowrate, can provide just the cooling you need. Any outlet for heat is good enough.

Insulation will merely slow the heating down. A material with variable thermal resistance will also just slow it down, not stop it.

 

Btw, I believe that all materials have a thermal conductivity which is a function of the temperature... although they are not a strong function.

Edited September 10, 2010 by CaptainPanic

[Newbies_Kid]

How about a sandwich material which consist of 3 different layers?. The inner layer must has less thermal conductivity than the outer layer, while the layer in between is a solid heat sink. What do you think?