metalization of solar high temperature absorber pipes

[nikoslarissis]

I have to make greater the absorptance of a pipe from Fe on a solar system with concetration. High Temperature 400 - 500 degree C. May be a arc or flame spray with black chromium make the job. Thank you for your help and any idea.
Nikos

[kschewe]

I have to make greater the absorptance of a pipe from Fe on a solar system with concetration. High Temperature 400 - 500 degree C. May be a arc or flame spray with black chromium make the job. Thank you for your help and any idea.
Nikos

i guess you can spray it with 444mxc or 444 powder, which has chrome content. it will be a grey color though. they might have a high heat powder coating available now days in black.

[MichiganMan]

There are HT paints designed for this type of environment (HT). A few things to consider...

How quickly does the system come up to temperature and how often does it cycle up/down in temp? Presumably since it is solar it will cycle at least once a day, and it likely heats relatively slowly, but these factors play an important role in selection of the coating. I think unless these are known, however, all we are doing is guessing.

A few different things could work for you, and I suppose some testing would be a good idea. I suspect that the coarse texture of arc spray would be helpful in trapping more of the energy (more angles, surface area, etc.), but I admittedly have done nothing of this sort before, so it may warrant testing an arc sample along side a finer coating (plasma, HV*F, etc).

I believe Dampney manufactures a number of products that could be used in this situation, and it may be worth looking up their technical/engineering staff for discussion.

I suppose if you have the time for testing you could paint one piece, thermal spray one piece and thermal spray and paint a third to see how much impact there is on the result. In the end it is probably splitting hairs which method will provide the best result, but if it noticably impacts the efficiency of your system, then it may be a critical component of the design.

[plasmajet1990]

I have to make greater the absorptance of a pipe from Fe on a solar system with concetration. High Temperature 400 - 500 degree C. May be a arc or flame spray with black chromium make the job. Thank you for your help and any idea.
Nikos

You can try with TiO2 powder (flame spray) in a thin layer.

ion

[djewell]

I suggest coating the pipes with a dense copper or aluminum coating, then sealing it with high temperature paint to prevent oxidation.

[sreenuvundela]

I agree with djewell suggestion.

Dense copper or aluminum coatings exhibit good conductivity but to get optimum conductivity of these coatings, heat treatment (Stress relieving) required because during coating hardening will occur (Rapid solidification of particles leads to hardening).

After heat treatment of copper coating, by applying black color paint on coating, you can increase absorbity.

Regards,

SREENIVAS