# Heat transfer coefficient of cylinder in free air?

1. Apr 28, 2013

let say a cylinder(steel) is 6 cm diameter and length of 3.5 cm length. and is heated to 1000 degree c.

in a room of free air and room temperature of 20.

will convective heat transfer dominate? it radiation is negligible?
what would the convective heat transfer be?
what power(watt) is needed to maintain the 1000 degree ?

2. Apr 28, 2013

### Alt-Bringer

im assuming introducing an electric current into the cylinder is what heats it,
and that 1000c wont melt it (i dont know conversions)
and that "free" air means a normal environment (no vacum pressuer etc.)

i think convection or random air circulation would be the major dissapent of heat, if thats what you mean
hot metal from my very limited experiance dosent radiate well, ie you can put you hand near a fresh weld and as long as you dont touch it your fine
by the small amount of convection pulling cool air tward it and normal air circulation spreading it around

thats not saying you dont get decent radiant heat, but that its kept to an area of a few inches
where as somthing like fire radiates in a relativley large area

3. Apr 28, 2013

### mechwill

If the steel cylinder is the only heat source in the system without any fan but the system has small air circulation, it is a natural convection. The melting point for steel is around 1370 C, so theoretically, it will not melt.

However, if you look at how the hot iron was taken out of the furnace and you see the red glowing part of the iron, it is primary light radiation heat transfer. Personally, I haven't seen if there is any red glowing part on the steel when it reaches to 1000C. But let's assume it's black steel.