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A little thermo Re: Block Heaters

To: Spridgets <spridgets@Autox.Team.Net>, team-thicko@Autox.Team.Net
Subject: A little thermo Re: Block Heaters
Date: Sun, 24 Oct 2004 08:00:28 -0700 (PDT)
--- Rick Lindsay <rick@stoolhead.com> wrote:
>    Perhaps I am missing something but I'll ask
> anyway.  An antifreeze 
> solution is slang for 'coolant'.  It adds anti-boil

Yes, antifreeze (ethylene glycol,"EG", anyway) has a
higher BP than water (in a 50 - 50 mix at sea level
it's around 230-240F, if memory serves).  BUT - water
has a much higher specific heat than EG, 1.0 vs. ~.57.
 What this means is a given unit of mass flow rate of
water will carry ~40% more heat away than a given unit
of mass of EG. The EG/water mix does still win
slightly for "the ability to be under the boiling
point" at a given pressure,  BUT....we care more about
absolute temperature than not boiling.  That is, you
want a spridget at around 180-185.  What Bud does is
add water wetter to straight water in accordance with
racing regs to keep the slippery stuff out of the car
and off the track.  Water wetter is a surfactant, it
reduces the surface tension of the water, and allows
it to contact a greater surface area and dlets the
fluid do a better job of heat conduction.  It DOES NOT
raise the boiling point, but it does increase heat
transfer, so you run cooler.  EG alone has a lower
surface tension than water, but, again, a lower
specific heat. 50/50 water/EG vs. 100% water is pretty
much a push in terms of heat transfer.  Water + water
wetter will keep you running cooler.  EG/Water/Wetter
is best, but illegal on the track.  

So, Bud, I generally drain and pull the radiator and
block for the winter anyway!




=====
Ron Soave

"And another thing.....when I gun the motor, I want the whole world to think 
it's coming to an end." 

- Homer Simpson


                
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