Recommendations for waterblock 3

[ccjung]

Hi,

I am in development of a waterblock that will be used in continuous service in a saltwater aquarium.

I have previously Hard Anodized some aluminum pieces but have had one or two units fail.

I need a conductive material that has also been treated for corrosion resistance in a continuous saltwater service environment.

I know that Titanium is the best choice, but economic constraints prevent this.

Is there any recommendations on an anodization or PTFE coating?

Any recommendations on material? I had been using 6061 and Type III, CL 2 Hard Anodize and would like to know if there is a better alternative, like EN.

Thanks in advance

Chris

 

[EdStainless]

Could it be plastic with conductive straps/tabs/inserts?
Continious saltwater service really requires Ti, 6%Mo SS, or 70/30 Cu/Ni. Cu is toxic so I wouldn't use any lower alloy Cu grades (brass or bronze).

How long does it need to last? What happens when it fails?
You might use a lower alloy stainless (2205 or 317L) and accept a reasonable life.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[ccjung]

Hi EdStainless

Thank you very much for taking your time to answer my question.

It can be plastic if I can get similar heat transfer properties. The other part is since the contact time is relatively short, I count on some of the materials heat capacity to keep a large thermal gradient between the waterblock and fluid.

I chose aluminum because of its high heat capacity and good thermal conductivity, but am open to any materials with similar characteristics.

I would like this part to last at least 2 years but would prefer much longer service out of it.

Ill look into the cost effectiveness of the materials you mentioned.

Any other suggestions? Is there a treatment better than Type III CL2 for aluminum in Saltwater service?

Thanks again

Chris

 

[DAVIDSTECKER]

6061 does not work below the water line.
Try 5086. It is what they make the ships hulls from.

 

[ccjung]

Thank you.

Based on some preliminary research (preliminary now) I am now kicking the idea of the part being made of copper (due to its thermal conductivity) and gold plate or electroless Nickel.

Does anyone think this is a possible alternative?

If not, would a ceramic based material be suitable.

I have really learned alot from this forum and thank everyone in advance.

Chris

 

[rnd2]

ccjung
Could tell us a bit more about the block and how it operates? dimensions could be helpful.Metals thermally more conductive than non-metals other than diamond, but, depending what is required,it might well be possible to get by with completely corrosion free non-metallic composite material. Is your maximum operating temp for the block away from water less than 120 deg. C. ?

 

[ccjung]

Thanks for your replies and sorry for the delay.

The waterblock is intended to make contact with the aquarium water. The waterblock is cooled by a thermoelectric module, and water is passed through the waterblock.

In my preliminary designs, I was using 6061 AL and a pass through device.

I am now considering direct contact with the thermoelectric module and using delrin as the material for the waterblock.

I was seeking a more thermally conductive material such as AL, but now, I am reconsidering the design to allow the water to be in direct contact with the Thermoelectric module.

I would like to use Titanium, but its thermal conductivity is relatively low compared to AL, and in order to be cost effective, the pieces relatively small.

Any other suggestions would be nice.

The current production version of the device is at:

http://nanotuners.nanocustoms.com/nanotuners/product_info.php?cPath=34&products_id=79

I have had great success with this device, but the fear of pitting or pinholes leaves me a bit worried, since AL is not good in a saltwater aquarium.

Thanks in advance

Chris

 

[rnd2]

OK. I am getting more of a "handle" on what is required.
The heat transfer rate is reasonably ameable. I don't believe you need metal for this.
Here is my suggestion.
(I am assuming that it is desirable that you need a food grade resin as the bloch is in direct contact with aquarium water.)
For your initial research,
Select a vinyl ester resin such as Dow 411 or equivalent.
Fill with as much barium sulphate powder as you can possibly manage until a dough consistency is achieved.
Roll the dough into thin sausages to remove the trapped air. Sprinkle barium suphate powder onto your rolling board to prevent sticking. Mould your piece. Test to see if the heat transfer rate is adequate. I think you will find it will be.
There are other materials you can use such powdered metal or as zinc oxide but they will kill the fish.

 

[unclesyd]

If you use thin wall sections of Titanium the material's heat conductivity factor would essentially drop out of the equation and your heat transfer will depend on the film factors.