possible liquid to cool with

[Denovin]

Mercury
Does anyone know anything about the freezing point of mercury? its viscosity at low temperatures? How much heat it can hold as compared to water? Mercury would be ideal because heat from metal transfers better to metal (in most cases) and Mercury is a metal. Its pretty damn quick to atleast.. a little on the ground is.. Pumping it might be a different factor. Also is it a possiblity of being corrosive?

The only drawbacks that I am already aware of are, its toxic, and probebly very expensive.

[dicki]

mercury will be hugely expensive, though its heat transfer abilities would be good...

i think the expense, danger, difficulty in pumping and the expense would put most people off...

dicki

[Gregorach]

Yep, in addition to the ridiculous expense of the mercury itself, you're going to have to spend truly, madly, deeply silly amounts of money to get a pump that can move it. And it's not just a bit toxic - it's really toxic. I suspect that to build a system using mercury you'd need to get some kind of HAZMAT license (and if you don't then you bleedin' well should). Then of course there the wonderful question of chemical compatibility...

Still, it's gotta be at least theoretically possible - after all the nuclear industry builds cooling systems using pressurised liquid sodium. Now how does that sound? ;)

[evilmatt]

mercurys properites here (http://www.webelements.com/webelements/elements/print/Hg/heat.html) and here (http://environmentalchemistry.com/yogi/periodic/Hg.html)

nasty stuff tho, aparantly it used to be used as a laxative in victorian times so my chemist friend says

[nitan]

mercury in liquid form is not toxic. Its the vapour that is really bad for you as it is easily inhaled, so unless you handle it without protection or drink it u shud be ok. Also mercury could pose some issues as it expands and contracts a lot with varying temps (hence it is used in thermometers). You would need some form of header tank so it could change volume as it got warmer and colder...

Just my $0.02

[illmatik]

A pump capable of moving mercury (which will have an operating temp of 100+ degrees to boot and will require its own cooling system) is going to run you a lot of dough, not to mention require frequent routine maintenance, with which you run the risk of being poisioned everytime you drain the system to service the impeller mechanism. Since mercury is a heavy metal, it is going to put a great strain and wear down parts. My pop works in R&D for a major pharmaceutical firm, and assembles and reassembles systems like these (not mercury, but other high viscosity fluid systems) all day long. As cool as it would be, it's probably not worth it when a mach I can be had for ~$500 and give more predictable, reliable performance.

[Gregorach]

True, mecury in its liquid form is not toxic. However, that's kinda like saying that gasoline in its liquid form is not flammable - entirely true, but completely pointless since the liquid starts vapourising immediately on exposure to the atmosphere. ;) The thermal expansion is a problem that hadn't occurred to me though...

I believe mercury was also popular for treating the "sailor's disease" - it was injected into the affected parts using crude syringes! :eek: The Victorians also used arsenic as a tonic, IIRC...

[nitan]

yes you are right...essentially its not a path worth pursuing...but there must be better coolants than water that can be easily pumped using eheims and what not.

The constraints are:

Liquid at ambient temp ranges
Same viscousity as water
Non toxic
non corrosive to the metals and tubing used

erm...cant think of anything else right now...in the middle of trying to build an AD forest...:(

[evilmatt]

yeah back then medicine was a bit like russian roulette good chance it'll do nothing or it'll kill you.

The more gore a surgeon had on his apron and what have you the better he was considered to be. I think that went for the intruments too.

<crazy idea>
mercury conducts right maybe you could rig up some sort of electro dynamic pump.
I would guess it would depend on wether you could charge the mercury. Might require some fairly hefty voltages and HT supply not very good with electro static senstive stuff near it.
</crazy idea>

[Player0]

Water has better cooling properties than Mercury. Mercury has a lower specific heat I beleive. Something that makes it inadequite, anyway.

[Denovin]

Has anyone tried 200 proof Grain alcohol (Everclear) at very low temps?
Or whats the other type of alcohol?
I heard good things about it mixed with water, because it moves alot faster.

[ralf_c]

ma mamma told me to stay the hell away from mercury:P

i remember holding a sealed container of that stuff as a kind, thats stuff was freking heavy. a fuid like that will kill your average pump, not worth the headache.

[Gregorach]

Well, it's amazing what you can find out from a quick Google search: Specific Heat Capacities for Different Liquids and Fluids (http://www.engineeringtoolbox.com/24_151.html). Turns out mercury has a truly lousy SHC at 0.14 kJ/kg K, which is approximately 40 times less than water. So, if my maths is right, then even accounting for the high density of mercury (specific gravity of 13.6) mercury can transport less heat per unit volume than water.

The only fluid on that list with a SHC greater than water is ammonia. However, it's lower density again means less heat per unit volume - plus its even nastier to work with than mercury...

There's a reason that water is the most commonly used liquid coolant - it really is the most efficient. The only reason to use other fluids is when you need to operate outwith the temperature / pressure envelope for liquid water.

[Denovin]

the idea of mercury came to me because I remembered that the heat transfer from metal to other objects isnt as good as metal to metal. I was thinking that maybe the mercury could transfer the heat faster. But then again, I was just throwing that out there.

Now as for cooling with sub 0 C I hear that Methynol (alcohol.. rubbing alcohol right?) Mixed with water, a 50/50 combo works much better because it flows faster/smoother then water, and you can get sub 0 temps off it.

I know alcohol doesnt freeze nearly as well as water. So maybe dropping the temps WAY low with pure alcohol to use instead of water as coolent. But then again, when you get that low in temps, you could cause cold damage to certian parts.

[Gregorach]

Yeah, you could certainly use alcohol to get sub-zero, but ethyl glycol (antifreeze) might be a better choice. Again, the problem with using pure alcohol or antifreeze is that it's SHC isn't very good as compared to water. Plus any form of pure alcohol has certain dangers - flammability is the main one that springs to mind... ;)