Recent content by xtronics

Emissivity (sometimes called emittance) of copper can vary from 0.7 to .88 but for electrical work 0.4 is pretty good guess - that is not near zero - emissivity varies from 0 to 1!

I did quite a bit of digging - and found the work and formulas of fusing currents etc. The convection effect is quite small if the wire is horizontal - and not that big if vertical. If you can point me to a reference that disagrees I would be interested. The practical results seem to support...

Sometimes when designing it is nice to start in the correct ballpark. I have it all worked out and wrote it up here: http://wiki.xtronics.com/index.php/Wire-Gauge_Ampacity#Watts_generated_in_a_Wire Now if I could only find believable emissivity numbers for bare Manganin and enamel coated...

I've found the basic solution. Irradiation dominates to the point you can ignore conduction in still air. Because Q is about = Ah(T1-T2) h =about 4(e)(5.67e-8W/(m^2 K^4)(298K)^3 or h = about 6e W/m^2 K h is the radiation heat transfer coefficient and e is emissivity...

I'm looking for some number to use for a heat transfer coefficient of bare wire in still air. but not having much luck. This number just needs to get me into the ball park - I know it would be rather complex to solve with precision. Think of it this way - I have a length of wire dissipating x...