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Heat transfer from current-heated wire to ambient air
Posted Apr 3, 2012, 12:00 p.m. EDT Heat Transfer & Phase Change Version 4.2 1 Reply
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Dear all,
as indicated in the title, the setup of my simulation looks as follows: a wire, with an applied current which causes a heat generation. The wire is surrounded by a block of air which yields a cooling of the former. For a more detailed view and to see my settings for this simulation have a look at the attached file.
Here a short summary of what I've done and what is the result:
1. Joule heating, active only in the wire-domain.
2. Applying groung, currrent=> heating of the wire.
3. Temp. of the wire-boundaries: T2 (Temp. of the air)
4. heat transfer in fluids, active only in the air-domain.
5. outer boundaries of the air-block set to 293K.
6. inner boundaries of the air-block set to T (Temp. of the wire)
Therefore, I should obtain a coupling of the Temperature of the wire and the surrounding air, however the temperature of the wire rises linearly with time (an asymptotical behaviour is expected).
It looks as if the surrounding air gets heated by the wire, but the latter experiences no cooling by the air. Why is this the case? By applying 3. from above I should get a cooling of the wire.
thank you in advance,
greetings,
Michael
ps.: The number of available modules is limited to the ones mentioned above plus "heat transfer in solids".
as indicated in the title, the setup of my simulation looks as follows: a wire, with an applied current which causes a heat generation. The wire is surrounded by a block of air which yields a cooling of the former. For a more detailed view and to see my settings for this simulation have a look at the attached file.
Here a short summary of what I've done and what is the result:
1. Joule heating, active only in the wire-domain.
2. Applying groung, currrent=> heating of the wire.
3. Temp. of the wire-boundaries: T2 (Temp. of the air)
4. heat transfer in fluids, active only in the air-domain.
5. outer boundaries of the air-block set to 293K.
6. inner boundaries of the air-block set to T (Temp. of the wire)
Therefore, I should obtain a coupling of the Temperature of the wire and the surrounding air, however the temperature of the wire rises linearly with time (an asymptotical behaviour is expected).
It looks as if the surrounding air gets heated by the wire, but the latter experiences no cooling by the air. Why is this the case? By applying 3. from above I should get a cooling of the wire.
thank you in advance,
greetings,
Michael
ps.: The number of available modules is limited to the ones mentioned above plus "heat transfer in solids".
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1 Reply Last Post Apr 3, 2012, 3:33 p.m. EDT
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Posted:
1 decade ago
The air is drawing some heat away from the wire, but at a very low rate because of its very low thermal diffusivity. It would take a very long time to reach steady state. In reality it will not take that long because of convection in the air which you are not modeling and also because of heat loss by radiation. These factors will also reduce the steady-state temperature. Also, the current density that you put in the wire is very high.
Nagi Elabbasi
Veryst Engineering
Nagi Elabbasi
Veryst Engineering