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Peter Mackay
09-04-2007, 07:50 AM
Hi there, first post so be kind!!!
Can anyone suggest a suitable eutectic solution mix that provides phase change at minus 5c and another mix for minus 22c. Has to be compatible with metals copper and stainless steel. Tried the glycol blends but the eutectic point is too wide. Thanks in anticipation ;)

lana
09-04-2007, 10:52 AM
Hi Peter Mackay,
Welcome to this forum.

Try Calcium Chloride 29% (by mass) freezing temp. -48°C.
OR Sodium Chloride 23% (by mass) freezing temp. -21°C.

Check the compatibility with copper first.

Hope this helps.

Peter Mackay
10-04-2007, 02:46 AM
Thanks Iana for your quick reply,

But we can't use salts with copper / stainless steel.
:)

US Iceman
10-04-2007, 05:22 AM
Hi Peter, first of all let me welcome you to the RE forums.



...that provides phase change at minus 5c and another mix for minus 22c...


Is the phase change you are looking for from crystalline to liquid? Are you trying to use this mode of phase change for a thermal storage concept?

Or, are you looking for a phase change from liquid to vapor states?

Peter Mackay
10-04-2007, 08:16 AM
Thanks US Iceman,

I am looking for something better than the ethyl glycol mix for a phase change of liquid> solid and return. The ethyl glycol we use now has a wide phase change temperature range and a relatively low latent heat value. Just hoping there is something with a narrower phase change point and higher latent heat factor.

Regards....Peter

Peter_1
10-04-2007, 10:24 PM
Thanks Iana for your quick reply,

But we can't use salts with copper / stainless steel.
:)
Why you think this isn't possible? We have SS eutectic plates with copper coils filled with salt it since 15 years.

They find in the sea copper coins from the Roman time.

The glycol are just made to avoid freezing up, therefore they're mostly used as a secondary coolant medium.
They mostly forms separate cristals which become a solution with a high viscosity but that's also why you can't store big latent heat in it. The plates filled with a glycol solution defrost very fast.

Do once for yourself the test with a glycol/water solution and a salt/water solution in a simple domestic freezer. Solidify both complete in a same recipient and watch/time then afterwards once the defrost proces.
You will see it for yourself.

US Iceman
11-04-2007, 03:00 AM
I am looking for something better than the ethyl glycol mix for a phase change of liquid> solid and return.


I am thinking your process is something of a proprietary nature and do not want to impose on you by asking too many questions, but it is the only way I know how to help.

Without knowing very much about the process I can only assume you need the solid to liquid phase change material because of the manner in which the cooling is implemented in your process.

To my knowledge, the general category of salts is probably the best way of approaching this. A lot of the PCM's (phase change materials) have a proprietary formulation I believe, or at least that is what I seem to remember reading.

If your process is stationary, why not use a common refrigerant? They are phase change materials.;)

Peter Mackay
11-04-2007, 10:28 AM
Thanks Peter_1 Your experience with salt is surprising. I will rethink using salts.

Peter Mackay
11-04-2007, 10:33 AM
Hello again US Iceman.. the application is to have the solution solidify on a system run cycle then thaw during off cycles. (Copper evaporator in a stainless steel tank filled with phase change material) Have tried many eutectic brews but still hoping to find something with a greater latent heat factor and a narrower phase change temperature point. Thanks for your interest.

Peter_1
11-04-2007, 12:35 PM
Try once diffrent products in your domestic freezer, you will find the biggest latent heat with pure salt.
Don't tell this to your client and sell this 'special solution' for 25$/kg ;) :D :p
Just joking...or perhpas not.:cool:
We insert first the salt in the plates and then fill it up with normal tap water.
Make that the plates have an inner curve so that it can expand a little. Put therefore some http://www.toolstation.nl/images/library/stock/webtables/36870.jpg on it an tighten them fast.


What's the English name for this tool?

Peter Mackay
11-04-2007, 01:02 PM
Thanks again Pete,
We call that tool a clamp.
I will experiment some more with salt.

Peter M

Peter_1
11-04-2007, 06:33 PM
Here are some examples, plates are +/-10 t o13 years old.

Peter Mackay
11-04-2007, 11:49 PM
Thanks again Peter_1

Poida
22-11-2007, 12:34 PM
Hello all
In relation to the discussion earlier in the year regarding eutectic solutions. I am interested in the salt solutions as an alternative to glycol but why do so many producers use glycol based fluids in transport and marine application in preferrence? My own application is domestic and stationary.
Does anybody have a contact for prepared salt based solutions in Australia?
Ta!

Peter_1
23-11-2007, 12:19 AM
Just poor ordinary kitchen salt in it in the right concentration and fill further with pure water. That's all.
Try it once in your own freezer with salt in diffeerent concentrations and also with some antifreeze like used in cars or teh expensive antifrogen. Freeze the solutions and once frozen, set it outside and monitor the melting process.
This is a test which doesn't cost anything but which can learn you a lot practical experience.