Resistive Heating: Approximate Calculation Needed

[osmansafa]

Hi all, I have made a simulation of resistive heating in Comsol which is basically a gold wire surrounded by air is exposed to 0.1 V and I got the temperature distribution. The numbers seem really high (The temperature is at 2000 K where the ambient temperature is 293) and I would like to make an approximate calculation. I used the heat transfer coefficient formula (heat transfer coefficient equals heat input over surface area times temp. difference) but the temperature difference is 75 K.
What do I miss here? Thank you in advance.

 

[Aaron Barnard]

You may be missing the effects of thermal conductivity in your model. Heat transfer coefficient is a measure of the rate of heat transfer per unit area, and it depends on the thermal conductivity of the medium. Generally, if you are dealing with air, the thermal conductivity is much lower than that of gold, so the heat transfer coefficient for air will be much lower than for gold. This means that the temperature difference between the wire and the air will be less than the 75K you calculated. You should also consider the size of the wire, as the thermal conductivity will vary depending on its thickness.