Choosing a heater band for vacuum system bakeout

[JoJoQuinoa]

Hello,

I'm trying to find the right wattage heater band for a cylindrical vacuum chamber that is stainless steel (304), ~2ft in length, ~0.5ft in diameter, and ~0.5 in thick.

From a quick google search, I was able to calculate the required wattage for bring the chamber up to and constant at 200C from room temperature. The bake time will be 1 hour from room temp to the desired temp and 11 hours at the desired temp. However, what I'm confused on is how to account for the heat loss to the air. Is it significant to be accounted for?

Thanks in advance,

 

[Tom.G]

See Example 9.2 on page 14 of this PDF file. Ball park guestimate from that example and its comments on radiation yields 2000W of heat loss to the environment.

https://www.researchgate.net/profile/Kifah_Sarraf/post/What_should_the_force_in_the_momentum_conservation_equation_be_in_a_natural_convection_problem_that_has_air_as_the_working_fluid/attachment/59d636d579197b80779943b1/AS%3A390557672198147%401470127613757/download/Chapter9_Free-Convection_Bergman_6th-ed.pdf

(above found with:
https://www.google.com/search?&q=convection+loss+200C+to+free+air)

(I hope there are some experts around here to chime in!)

Cheers,
Tom

 

[Dullard]

A couple of notes:
A device like this would typically be thoroughly insulated (mineral wool). Without insulation, local cooling will allow a large gradient across the unit.

SS is a horrible thermal conductor. You will get better uniformity (and regulation) with multiple heater bands.