Aluminium vs PU

[Lepetit]

Hello all,

I want to use aluminium pipes in a cooling system in which it will reach -25ºC (243K) with water-methanol as coolant, can be this a problem because of the corrosions of the aluminium?. Also I would like to know if aluminium can be activaed by radiation, because this fact can be a problem in my cooling system.

Now, I have the calculations with PU pipes and the system loses around 10ºC in a pipe of 1mm thickness. Can be it possible?

Thank you all in advance.

Cheers.

 

[btrueblood]

Yes, methanol will corrode aluminum (it breaks down the oxide layer on the surface of the aluminum). You might consider using a glycol coolant instead, or consult manufacturers of corrosion inhibitors for either type of anti-freeze.

What kind of radiation? Neutron bombardment can embrittle aluminum. Not sure how using PU (which I interpret as polyurethane) will help, it will be damaged by radiation equally, or possibly more rapidly, than Aluminum.

 

[Lepetit]

Thank you,
1) Yes, it will be bombard by neutrons and also PU is polyurethan (sorry for the misunderstanding).
2) The problem to use another coolant is the range of temperatures that I want to work.
3) Using Polyurethan you avoid the radioactivity activation but the problem is its thermal conductivity (much lower that aluminium). I don't know exactly the time to activate the aluminium ( I know that the time it needs is longer that copper for example).

Thank you again.

Cheers

 

[btrueblood]

Um, ok, you mean the time before the material itself becomes radioactive. I was speaking to the degradation of the material itself. I think the coolant itself may become radioactive, so not sure where the concern is.

 

[racookpe1978]

PolyUrethane is a very poor conductor, it will do very poorly as your material.

But nuclear bombardment by neutrons is a atom-isotope matter, not a material (compound of different chemicals) matter. C25+H42+N2+O6 So, what is being bombarded? Hydrogens, many carbons, a little bit of trace nitrogen and oxygen from the original mix, plus any contaminates? What else is in the PU that will get activated?

Why not stainless steel? Zirconium too expensive?

 

[Lepetit]

Yes the coolant can be activated too, but the problem (under the point of view of the project) affect more in the pipes because you can be in touch with them.

You are right, PU is a bad conductor; because of this I want to use anoher material. I need to improve as much as possible the heat transfer due to the stability of the desired temperature.

The problem of stainless steel (I considered it) it's the weight of the steel if you compare with aluminium or even the PU. About Zirconium...I need to get more information first.

Thank you all

Cheers

 

[racookpe1978]

A science fiction writer once wrote, "When scrounging for replacement parts, I can find them cheap, good quality, or quickly. Pick two of the three."

Same goes for scheduling fabrication work: Fast, Cheap, or Good Quality. Pick two.

For your material? All you want is: Low cost, low weight, high strength, low neutron absorption cross-section (low barn number, or no radiation effects after absorption), high heat transfer coefficient, good machining and welding properties, easy accessibility, no thermal growth with neutron absorption, no loss of strength or flexibility after absorption and neutron collision, easy disposition of scrap and residue, non flamable metal or metal flakes/dust/debris, non-toxic to machinists/general public/users, easy to store, easy (and legal) to ship once activated, easy (non-lethal) to dis-assemble once activated, etc.

Put those requirements in order of priority. You will find Miraculium in the Periodic Table right after Unobtanium. 8<)

 

[Lepetit]

I know that it is impossible to have all the properties of the world in only one material, that is the reason what I am asking for some doubts that I have...

The priority order:
- not activated in short terms of time (in case I need to replace it)
- good thermal conductivity in order to improve the cooling system
- low weight would be really nice (aluminium weight it's perfect)

These are all my requirements, but of course maybe I can't reach all the goals that I am looking for. After I have all the info that I can collect I will make a decision trying to be as close as possible to my requirements.

Thank you by the way