iMechanica - Comments for " How to find the average temperature a surface? ABAQUS -Heat transfer -user subroutine "
https://imechanica.org/node/12800
Comments for " How to find the average temperature a surface? ABAQUS -Heat transfer -user subroutine "enheat transfer
https://imechanica.org/comment/19343#comment-19343
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<p><em>In reply to <a href="https://imechanica.org/node/12800"> How to find the average temperature a surface? ABAQUS -Heat transfer -user subroutine </a></em></p>
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Radiation is significant at extreme temperatures only, and depends on the emissivity coefficient. Do you intend to melt the thing ?</p>
<p>I guess that heat conduction through the concrete is much more significant and faster than the heat convection through the air. You might even dispose of it. </p>
<p>But if you insist: the "average temperature of the void surface for sink temperature" evolves with time, as the concrete is heating. My understanding is that in this case you impose convection dictated by the temperature of other concrete elements, irrespective of the air temperature within the void. You'd push Watts across the void even if the air is hotter than the concrete.</p>
<p>My approach would be to model the void with elements that feature temperature as a degree of freedom. Then define two surfaces: one for the concrete around the circumference, another one for the circumference of these elements that represent the air. Set a constant film coefficient, and let the air have the same initial temperature (=sink temperature). Conduction should occur. The air should gain temperature. Within the air heat is conducted (not convected), so set the heat conductivity coefficient for air. </p>
<p>For heat transfer coefficients and heat conductivity you might want to consult the "VDI Heat Atlas" by VDI Gesellschaft (VDI = Union of German Engineers) or other reference books. </p>
<p>When you have assembled your model make a comparison: only heat conduction and heat conduction combined wíth convection. Is convection significant ?</p>
<p>Done (in my humble opinion, but I didn't deal much with heat transfer).
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Ruhr-University<br />
Bochum<br />
Germany
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</ul>Tue, 17 Jul 2012 19:12:01 +0000Frank Richtercomment 19343 at https://imechanica.orgError | iMechanica