Waterless coolant

[kenmorton]

What is the general feeling about the waterless engine coolants ?
Been looking at some stuff with a boiling point up around 200c suposed to be friendly to all engine types and works at a lower pressure 5 - 7 psi.
But are they any good at transfering heat ?

[greenv8s]

As long as it doesn't actually boil, heat transfer and specific heat capacity is more important than boiling point. Put another way, by the time you've boiled a normal water+antifreeze mix you're hot enough to start damaging the engine, so raising the boiling point doesn't get you any advantage. I guess this stuff is going to cost more than tap water?

[deltafox]

Its called Propylene Glycol and it enables you to run a zero pressure cooling system.
It dosent have quite as high a capacity for carrying heat as water, but it dosent corrode your engine either........ all depends on what you want to do.

[Pigeon]

Propylene glycol is actually a worse bet than normal ethylene glycol. PG has worse figures for specific heat capacity, viscosity, boiling point, and effect on boiling/freezing point when mixed with water. Its main advantage over EG is that it is much less toxic and can therefore be used in food processing plants where EG cannot. For running an engine without water in the coolant, neat EG is better than neat PG. For getting maximum cooling out of a given cooling system, neat water with a suitable pressure cap is better than an antifreeze mixture, since any addition of either EG or PG to water reduces its SHC and increases its viscosity.

[chuntington101]

is there any liquids that have a higher speciufic heat capacity than water??????

i now some sollar power stations in the US use a perticular liqued, heated by the sun, that is then used to heat water!?!?!?!?!?! dont know anything about the SHC of ti though.

Chris.

PS, or you could just run methanol and run a smaller cooling system and have more power!

shame about the miles to the gallon though!

[cyberface]

Molten sodium is pretty good at conducting heat, some nuclear power stations use it as a coolant and many exhaust valves are sodium filled to conduct heat away from hot spots.

As a general engine coolant additive, I'd ensure you use pure sodium rather than mixing it with water, as mild trouble could result in this case.

[Pigeon]

It's a good enough conductor but I don't know if its specific heat capacity is anything very impressive. It's used as a nuclear power station coolant because it doesn't interact with neutrons very much so it doesn't bugger up the chain reaction. It also freezes at 93 deg C IIRC, which would make it a bit of a problem for an engine... you'd be better off using sodium-potassium alloy which is liquid at room temperature.

[cyberface]

I thought it was the gallium-indium alloy which was liquid at room temperature? (getting off topic here )

[Pigeon]

That certainly sounds reasonable, given the low melting point of gallium - a quick google confirms it and also suggests various other possibilities such as gallium-zinc and gallium-tin. Specific heat capacity by weight is probably about the same, but specific heat capacity by volume is quite a bit better due to the higher density, so it'd certainly be better for cooling engines (to get back on topic). No good for nuclear reactors though (veering off topic again) as it'd absorb too many neutrons.

[cyberface]

Well I've got a 100 gram lump of pure indium sitting next to my computer, so if I were to acquire some gallium I could make some of this liquid alloy....

It's pretty clear that the common use of sodium in exhaust valves testifies to the thermal conductivity of such liquid metals, but the alkali metals in particular are bloody dangerous if the engine were to blow up... gallium and indium are pretty much non toxic but heavy for an engine coolant - esp. mid engined cars with front radiators contain a good quantity of coolant, and the added mass would be a problem. Pumping the damn stuff around the engine would also require more energy, reducing efficiency, and viscosity may change dramatically with temperature (unlike water, as long as you don't freeze the stuff).

This is a fairly crazy thread now, but since I like the air cooled engine in my car, I already have 'waterless coolant'

[love machine]

Very interesting indeed, I'd stick with H2O myself, with a dash of phosphoric acid. My guess is that liquid metals could get fun with things like alloy heads. Alkali Metals would get interesting if you had any sort of leak. They'd have the flourine off PTFE hoses and form compounds with allsorts, then you would get clags, precipitates, crusts and all sorts. Interesting about the melting point of those alloys. Also, Na/K are hugely expensive.

[Marquis_Rex]

Air cooling is more than a cooling medium (albeit a poor one) but more a way of life!