heat transfer improvments 1

[mcguire]

I'm a materials guy who has made thousands of tons of stainless steel for pipe and tube. My question is, would there be value in a micro surface finish on heat exchanger surfaces (one that does alter dimensions or change traditional surface appearance; not a coating) which causes low surface energy, therefore hydropohobicity? It has been widely accepted that this would cause drop-wise condensation and nucleation sites for boiling with a many-fold increase in heat transfer rates, but I would like to hear what the real practioners in the field think.
Michael McGuire
This was posted on another forum, but it was suggested I poll this group.

Michael McGuire

 

[davefitz]

I thought that union carbide had patented that technology 30 yrs ago, primarily used in clean clean cryogenic fluids applications.In normal water cooled power plants, the the trace impurities normally expereienced would foul the micro cavities , rendering them useless. maybe try the new supercritical CO2 plants.

"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick

 

[mcguire]

Thanks, Davefitz
Ill try to look that up. we have seen a enhanced resistance to impurity pick-up, but I see the logic in what you cite. We have found cavity size to have a critical upper limit, so if I can find the original Union Carbide patent, I'll post the comparison.

Michael McGuire

 

[mcguire]

Davefitz
Thanks very much again. There was a lot of work done from 1980 to 2000, which used three principles:
1. Attaching fine particles to surfaces to increase area exposed and render flow more turbulent. These would be expected to foul.
2 Lining with a low surface energy material, such a PTFE, to cause droplet formation. Such liners are short-lived because of their fragility.
3. Reverse embossing protrusions onto the surface to create turbulence. This works only to alter when the flow is otherwise laminar, a small segment of for enhancement.

Our principle is making indentations sufficiently fine that pick-up of solids and wetting of the surface is much decreased. The size is proprietary for the moment, but it is enough to make a bare stainless or titanium surface behave permanently like closely to a PTFE surface, i.e. contact angle about 90 degrees. See photo below in the attachment.

Michael McGuire