Condution in low pressure vacuum
Condution in low pressure vacuum
(OP)
Does the conductivity coefficient between surfaces change is the conduction takes place in a low pressure vacuum? Does the lack of atmosphere significantly change conduction?
I can imagine if two surfaces had 100% contact, that the atmosphere would have no effect, but most surfaces have some level of micro-roughness that prevents 100% contact over the overlapping area.
Any leads on this would be appreciated?
The materials I'm interested in would be a heated or chilled roller (probably steel or chrome plated) to stainless steel, polyester, and polyimide films.
I can imagine if two surfaces had 100% contact, that the atmosphere would have no effect, but most surfaces have some level of micro-roughness that prevents 100% contact over the overlapping area.
Any leads on this would be appreciated?
The materials I'm interested in would be a heated or chilled roller (probably steel or chrome plated) to stainless steel, polyester, and polyimide films.





RE: Condution in low pressure vacuum
Air is an insulation medium, This is the reason they use hollow walls in house building. I should imagine if you remove the air, you will improve heat transfer properties in the vacuum space.
Offshore Engineering&Design
RE: Condution in low pressure vacuum
RE: Condution in low pressure vacuum
But you are correct about the roughness of the contact surfaces between two materials.
The heat transfer is not pure conduction. Radiation and convection are are also in the mix.
A vacuum would reduce convection, so I suspect that overall heat transfer would decrease.
Chief,
So how do you explain the Dewer Vacuum Flask, aka the Thermos Bottle?
RE: Condution in low pressure vacuum
Consider Al to Al; the air path is probably irrelevant, because Al is such a good conductor that air doesn't really help it much. Consider alumina to alumina, the air path is probably irrelevant again, because the bulk alumina is such a poor conductor that air wouldn't do much to help.
TTFN
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RE: Condution in low pressure vacuum
So, following variables are of importance
thermall mass of film
film/roller temperature
area of contact
roller speed
film tension
film/roller surface roughness
Please fill us in on the details
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