DeTomaso Mailing List: February 00, Message #237

Sounds fantastic, but is it.  If you wanted to experiment with 100% 
inhibited propylene glycol you could try the "Seirra" environmentally safe 
stuff available everywhere.  But is it better, or is it marketing.

Lets use some data to cloud the issue.(ASHRAE Fundamentals,Sec 18.7-9)

@ 200 F       Water        Ehtylene Glycol       Propylene Glycol

heat cap
btu/lb-F       1.0              0.63                   0.69
(more is better)

Viscosity
cp             0.3              2.5                    3.0
(less is better)

Boiling point
Point F        212              388                    369
(more is better)

Max contact
temp F         n/a              300                    300

Thermal
Conductivity   0.38             0.13                   0.10

1.  So,  With the reduced heat capacity, you would have to pump 30-35% more 
glycol (more mass) to transfer the same energy as water, or raise the 
temperature of the glycol (heat=mass x heat cap x temp rise).

2.  And as the viscosity of the fluid increases the pumping frictional 
losses increase, thus moving less fluid for the same speed.  This increases 
the temperature (see 1).

3.  A little temp increase that should be ok, right? The boiling point is 
much higher for the glycols.  But what about caburization temp?  At 300 F 
the glycols start to thermally decompose (scorch).  Is this a problem?

4.  And finally, the thermal conductivity (a measure of how fast the fluid 
adsorbes or gives up heat) is a third of that of water.  This again tends to 
raise the temp.

I'm guessing if you ran pure antifreeze or the sierra product or the Evans 
NPG in your Pantera it would run VERY warm.  You would have to get a new 
guage to read that warm, 260-300.  It wouldn't boil over, but would it cook 
the glycol to cylinders walls in the water jacket.

Corrosion inhibited water is probably better for a stock pantera cooling 
system.

FWIW
4130
______________________________________________________
Get Your Private, Free Email at http://www.hotmail.com