In article <5399019e$0$29988$c3e8da3$>,
 Steven D'Aprano <> wrote:

> On Wed, 11 Jun 2014 08:48:36 -0400, Roy Smith wrote:
> > In article <53984cd2$0$29988$c3e8da3$>,
> >  Steven D'Aprano <> wrote:
> > 
> >> Yes, technically water-cooled engines are cooled by air too. The engine
> >> heats a coolant (despite the name, usually not water these days) which
> >> then heats the air.
> > 
> > Not water???  I'm not aware of any water-cooled engines which use
> > anything other than water.  Well, OK, it's really a solution of ethylene
> > or propylene glycol in water, but the water is what does most of the
> > heat transfer.  The glycol is just there to provide freezing point
> > depression and boiling point elevation.
> Would you consider it fair to say that, say, vinegar is "not water"? 
> Depending on the type of vinegar, it is typically around 5-10% acetic 
> acid, and the rest water. Spirit vinegar can be as much as 20% acetic 
> acid, which still leaves 80% water.

In a car, the water is the important part (even if it's only a 50% 
component).  The primary job of the circulating coolant is to absorb 
heat in one place and transport it to another place.  That requires a 
liquid with a high heat capacity, which is the water.  The other stuff 
is just there to help the water do its job (i.e. not freeze in the 
winter, or boil over in the summer, and some anti-corrosive action 
thrown into the mix).

When you said, "usually not water these days", that's a misleading 
statement.  Certainly, it's "not pure water", or even "just water".  But 
"not water" is a bit of a stretch.

With vinegar, the acetic acid is the important component.  The water is 
just there to dilute it to a useful working concentration and act as a 
carrier.  People are 90% water too, but I wouldn't call a person 
"water".  I would, however, as a first-order description, call the stuff 
circulating through the cooling system in my car, "water".

> Back in the day, car radiators were *literally* water-cooled in the sense 
> that the radiator was filled with 100% water. You filled it from the tap 
> with drinking water. In an emergency, say broken down in the desert, you 
> could drink the stuff from the radiator to survive. If you tried that 
> with many modern cars, you would die a horrible death.

But, I could do that right now, with my car (well, not the drinking 
part) .  In an emergency, I could fill my cooling system with pure 
water, and it would work well enough to get me someplace not too far 
away where I could get repairs done.

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