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Temperature Across Concrete Barrier

11/04/2010 10:31 AM

I need to calculate the thermal gradient across a 44 in thick concrete wall with a temperature differential of 350 F. Can some one point me to an equation to calculate temperatures across the cross section?

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#1

Re: Temperature Across Concrete Barrier

11/04/2010 11:13 AM

Assuming a steady state is reached, T = Tc + 350d/44; where:
T = temperature at distance d into the concrete from the colder side, and
Tc = temperature on the colder side.

Or, even simpler, 350/44 degrees per inch.

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#2
In reply to #1

Re: Temperature Across Concrete Barrier

11/04/2010 11:33 AM

Thank you. That will give me the straight line gradient which will be good for all practical purposes, however, what I am looking for is to plot a curve across the thickness which will depend on co-efficient of thermal condtivity for concrete and Delta T.

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#3
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Re: Temperature Across Concrete Barrier

11/04/2010 11:48 AM

It would be interesting to see an FEA-type simulation. If one side of the barrier is warmed (or cooled) quickly, there will be a steep gradient through a small but increasing thickness of the barrier, with the "heel" of the curve progressing through the barrier until the steady state is reached.

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#4
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Re: Temperature Across Concrete Barrier

11/04/2010 12:00 PM

Exactly! The curve will become flatter as it goes from high to low temp across the section and at a certain thickness it will become completely flat and there will be no heat transfer beyond that.

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#5
In reply to #3

Re: Temperature Across Concrete Barrier

11/04/2010 1:02 PM

For a plane wall, a temperature step ( + or -) and for constant thermal diffusibility there are already equations and a FEA simulation is not required.

To answer the previous question the temperature gradient can be determined wiyj help of conductivity if the heat flow/area unit is known. Since the total temperature drop is known what was suggested is totally sufficient provided that the wall is plane or that the ratio R/t is big for a round wall.

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