Applying desiccant to surfaces (aluminum sheet or PLA/PETG)

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Summary:
I would like to prototype building my own enthalpy wheel (https://en.wikipedia.org/wiki/Thermal_wheel) and I need to apply some desiccant to the surface of the material that I will be making the wheel out of. How can I do this?
I will either be using aluminum strips wound up, or 3d printing it out of PLA or PETG. How can I apply a coating of silica to the surface of either of these materials so that it can hold and release the moisture of the incoming air/outgoing air?

This is to manage heat and humidity in my campervan project.

Ideally It would be easiest to 3d print the wheel, and PETG has much better thermal conductivity than PLA plastic, but both are significantly lower than aluminum.
 

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  • #2
Tom.G
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After the wheel is constructed, use a spray adhesive on it then sprinkle the dessicant on. Then leave it alone for a bit. After the adhesive cures, shake off the excess dessicant.

Cheers,
Tom
<edit> Sprinkle gently so the dessicant doesn't bounce around and get covered with adhesive. </edit>
 
  • #3
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and would i just use pure silica powder? I would have to toss it around in a bag of it or something because the channels in the wheel will probably be around 1-2 inches deep and extremely narrow.

It would be much better if i could make a solution of it that i dip the part into
 
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Tom.G
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and would i just use pure silica powder? I would have to toss it around in a bag of it or something because the channels in the wheel will probably be around 1-2 inches deep and extremely narrow.

It would be much better if i could make a solution of it that i dip the part into
If you make a solution of silica and an adhesive you end up with the silica completely coated with adhesive; seems rather counter-productive.

Or perhaps you were thinking of applying adhesive to the disk then shaking the sticky disk in a bag of silica. Could work if you can stop the adhesive from filling the channels due to surface tension.

Another perhaps: Maybe you can find an adhesive, say a powder, that will adhere in a thin film to the disk with static electricity, and will cure with heat (or maybe UV). Coat the disk, shake in a bag of silica, cure.

Sounds like the fix is to change the aspect ratio of the channels and/or use a larger disk. :oldcry:

How about making the disk of spun polyester mat, the kind used in COVID-19 masks? Then you can soak the disk in a water or alcohol suspension of silica and then 'regenerate' it. Of course a frame is needed to hold the mat in a disk shape.

Or, the "obvious" is to ask a manufacturer how they do it. You may have to ask several of them before one responds with an answer beyond "No comment."

As a last resort, by a replacement disk for a commercial unit.

end of brainstorm

Cheers,
Tom
 
  • #5
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I think i just thought of a great way to do this. I will try to get silica powder, and then surround my 3d printed part in the powder, and then I bake it, this way it will maintain its shape and a thin film of silica will stick to the printed part.

people are already doing this with salt in order to reinforce 3d printed parts, so i assume it should work fine with silica powder.


Any thoughts on this idea?
 
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chemisttree
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Tom.G
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I think i just thought of a great way to do this. I will try to get silica powder, and then surround my 3d printed part in the powder, and then I bake it, this way it will maintain its shape and a thin film of silica will stick to the printed part.

people are already doing this with salt in order to reinforce 3d printed parts, so i assume it should work fine with silica powder.

Any thoughts on this idea?
Certainly worth trying! Nicely creative too.
I suggest trying it first on a small scale to work out all the 'unknowns.'

I have no experience in 3D printing, but an 'unknown' that comes to mind is you may have to apply some pressure (as in forcefully compacting the powder) to partially imbed the silica powder in the surface to get adhesion.

Cheers,
Tom
 
  • #8
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Try this.

Or this.
Thank you but im not seeing any relevant (how its made) info on either of those links. I hope i didnt miss anything.
 
  • #9
chemisttree
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Thank you but im not seeing any relevant (how its made) info on either of those links. I hope i didnt miss anything.
Did you read the patent? Column 2, lines 8-56, for example?

This picture on the Munters site should describe in enough detail what needs to be done.
1610223031008.jpeg


Impregnated filamentous material means fiberboard or cardboard and excelsior means wood shavings. Incorporating silica into that occurs during its manufacture. A slurry of fibers and silica is poured out onto a screen mold and residual moisture is pressed out (like how you make paper) and then dried. That’s “impregnated” paper. From that paper a cardboard stack is made. From the cardboard stack is cut out a round shape and then it is fixed to an arbor.

You are going to have lots of trouble if you can’t follow bread crumbs like these...
 
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  • #10
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Did you read the patent? Column 2, lines 8-56, for example?

This picture on the Munters site should describe in enough detail what needs to be done.
View attachment 275928

Impregnated filamentous material means fiberboard or cardboard and excelsior means wood shavings. Incorporating silica into that occurs during its manufacture. A slurry of fibers and silica is poured out onto a screen mold and residual moisture is pressed out (like how you make paper) and then dried. That’s “impregnated” paper. From that paper a cardboard stack is made. From the cardboard stack is cut out a round shape and then it is fixed to an arbor.

You are going to have lots of trouble if you can’t follow bread crumbs like these...

Thanks for your suggestion. Also a descant wheel is not an ERV wheel (which is why I specified I need to apply it to aluminum or a plastic capable of heat transfer). They do different things and are manufactured differently.
 

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