Thought exercise: Mercury as a liquid coolant.

[Saberus]

Purely hypothetical here, and some hard math on efficiency would be appreciated.

Provided we had a setup that used plastics and mercury-safe alloys, and there were no leaks in the system to create potential health and environmental hazard, would mercury make a good liquid coolant?

It's just a crazy idea I had this morning, seeing liquid metal pumping through a machine would just look insanely awesome. But further reflection leads me to think it's beyond being made practical for a myriad of reasons.

As an aside, is there an alternative that looks like liquid metal without all the hazards?

 

[hunter315]

Mercury would actually be an awful coolant, its specific heat is far too low. Mercury has a specific heat of only 0.140 compared to water's 4.186 which means that in order to cool a system with mercury you would have to have a flow rate 30x higher to be able to absorb enough heat from the CPU and GPU to keep them at the same temperature that a water loop would. This ignores the change in viscosity totally messing up water blocks and radiators.

 

[pigsinspace72]

Now, if you were pumping liquid hydrogen through the pipes, that would make great cooling as it has spefic heat capacity of like 14

 

[Saberus]

Mercury would actually be an awful coolant, its specific heat is far too low. Mercury has a specific heat of only 0.140 compared to water's 4.186 which means that in order to cool a system with mercury you would have to have a flow rate 30x higher to be able to absorb enough heat from the CPU and GPU to keep them at the same temperature that a water loop would. This ignores the change in viscosity totally messing up water blocks and radiators.

Well, to be fair let's also consider that mercury is denser (13.534g/cc) than water (1g/cc). since specific heat refers to one gram, 13.534 * 0.14 = ~1.895, or about 45% the thermal capacity of water by volume. Still not that great.

Viscosity of mercury is 1.526, water is ~1, and ethylene glycol is 16.1, so mercury is close to water in terms of ability to flow.

Mass per volume I can see being a problem with pumps, especially centrifugal types.

As said, this is just a thought exercise. In reality I understand that it's cool, but impractical, and pretty dangerous.

Regarding my extra question, does anyone know of a fluid that looks like liquid metal that's not so heavy/dangerous?

 

[4Ryan6]

Some water cool for performance some for looks, if you're just after looks here's some silver colored coolant for U. (Personally I'd just run distilled water)

http://www.performance-pcs.com/cata...info&cPath=59_381_1071_1073&products_id=40728

 

[manofchalk]

Mercury to my knowledge is one of the few room temperature liquids that has a better heat carry capability than water, but as mentioned is impractical/unsafe to use and expensive as all hell.

You might want to check out the Mayhems Aurora series of dye's. I think they have a silver dye that might achieve what you want. Though do be aware that it is not intended for everyday use. Pour it in the loop, take photos then drain and clean the thing is what Mayhem recommend.

Now, if you were pumping liquid hydrogen through the pipes, that would make great cooling as it has spefic heat capacity of like 14

Liquid Hydrogen is ~33°K, or around -250°C. Its ability to carry heat doesnt even matter from a practical standpoint, the bigger concern is how do you keep it cold to stop it evaporating. Usually the answer is more of it, because its going too.

 

[Saberus]

Thanks for the links to the fluids, and for all the input.

 

[4Ryan6]

Thanks for the links to the fluids, and for all the input.

There's plenty of different colored coolants and dyes available, and some have actually gelled inside the system and blocked off the coolant flow, which needless to say is bad, very bad.

I personally suggest maybe going with colored tubing and keep the coolant as additive free as possible, nothing cools better than Steam Distilled water with as little additives as you can get away with.

I use 100% pure steam distilled water with zero additives and not even a silver kill coil, I've been running it like that now over a year, just inspected, flushed, and refilled my system back in May, and saw no problems, at all.

 

[terry4536]

It is also remarkably heavy. Many years ago I had a physical chemistry lab that required mercury. The mercury was dispensed in a 125ml squirt bottle. When I picked it up, I was expecting something like a typical water bottle. That little bottle must of weighed close to ten pounds. I had to do a double take to my chagrin.

 

[terry4536]

And no, unless you are talking about cooling a nuclear reactor, mercury isn't a practical coolant.


The mercury vapor of liquid mercury is quite toxic.

 

[Pinhedd]

Mercury would be downright terrible to use in a cooling setup, and not even for reasons of heat transfer.

Mercury readily bonds to other metals, including copper and especially aluminium. These compounds are called amalgams, and are used for various purposes that require a soft but workable metal. Over time the cooling loop would quite literally solidify, if it doesn't corrode the block to nothing first.

Then there's the fact that it's 13 times denser than water, and would most likely overwhelm any household pump that tries to move it.