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I am trying to find the specific current needed to heat up a wire to a specific temperature. The wire material is kanthal. With a thermal conducitivty of 22 W/mK. I've calculated the resistance, from the resistivty and the dimensions of the wire.

If I want the wire temperature to be, say 1000 degrees. How do I find how much current I need? How’s the relationship between the effect and temperature?

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  • \$\begingroup\$ You can't know the power requirement without knowing the power loss to air or whatever you are heating at the desired temperature. You need to consider heat loss through conduction, convection and radiation. Once you have that - there's your power requirement. \$\endgroup\$ – Transistor Sep 21 '16 at 9:20
  • \$\begingroup\$ Just to add to @Transistor's comment : best case, that's several hundred pages of reading until you have some idea of the issues. Worst case, the relationship is ill-defined enough that you still need to experiment, measure, and adjust your model of the relationship until you get an acceptable result. \$\endgroup\$ – Brian Drummond Sep 21 '16 at 11:12
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    \$\begingroup\$ I heated 10cm of 0.2mm kanthal wire to over 1000 degrees C with around 7A in free air (I have access to a thermal camera). 10A melted it. As the temperature goes up, the radiated heat goes up. You can calculate radiated and convected heat, but it is difficult due to unknown emissivity of the wire (which also changes once the wire has been hot and tarnishes) and the convection figures are normally given for flat surfaces of a modest size. I'm afraid you have to "suck it and see". Kanthal wire has a very small temperature coefficient of resistivity, but it is your best way to measure the temp. \$\endgroup\$ – Matthew Sep 21 '16 at 21:35

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