What is the max free air heat transfer coefficient(film coefficient)?

[Askara]

what is the max free air heat transfer coefficient(film coefficient)? at 1000 c?

i have a object that is at 1000 degree c by applying 900watt. i model it solid edge and apply heat generation load of 900 watt, from what i research air convection is 5-25 w/m^2/k. but when i apply that in the thermal analysis with solid edge. i get a massive number.

it only go back to 1000 degree c by applying convective file coefficient of like 400 w/m^2/k? why is that? is 400 w/m^2/k even possible?
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[Chestermiller]

At 1000 c, radiative heat transfer is going to dominate over convective. Try calculating the heat transfer rate from radiative heat transfer.