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Subject: [FlyRotary]
Re: NPG + use in aircraft??
How do you know which "boiling is occuring?Is the
Nucleate boiling detectable?
Georges B.
Nucleate boiling will
most likely, but not necessarily, occur at high power level and high coolant
temps, and you will see coolant pressure probably about equal to cap
pressure. Film boiling will is evidenced by max cooling temps, high and
fluctuating pressure (spikes exceeding cap pressure) as large steam bubbles
form and collapse. Large amounts of coolant will likely be lost if the
condition isn’t remedied very promptly.
Al G.
-------Original Message-------
Subject:
[FlyRotary] Re: NPG + use in aircraft??
George B.;
Nucleate boiling
(small steam bubbles forming and dissipating) provides the highest heat
transfer coefficient from the surface to the coolant; better than no boiling.
Film boiling, on the other hand, is when there is a layer of steam
between surface and coolant, and the heat transfer coefficient drops
precipitously. The occurrence of film boiling is a very bad thing,
causes serious hot spots in the walls, and can damage the engine.
Al G.
P.S. Can we dis
the background on these messages?
-----Original Message-----
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Echo Lake Fishing Resort (Georges Boucher)
Sent: Monday, June
27, 2005 11:51 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: NPG +
use in aircraft??
"boiling removes heat" I
have a hard time understanding that quote. When racers started using PG
they were able to run 15:1 compression on "pump" fuel
due to the fact that boiling
coolant created hot spots in the combustion chambers & in turn causes
pre-ignition (they also reversed the coolant flow direction to bring the
cooled coolant to the hottest part of the system, & all this with no
pressure cap. The one disadvantage I see in the 13b is that it can't handle
the potential higher boiling point of PG. I have a 3.0 L V6 that I reversed
the cooling system on to use in the Christavia (that was before I got
hooked on the 13B)
-------Original
Message-------
Subject: [FlyRotary] Re: NPG + use in
aircraft??
Has anyone used the NPG+ coolant in
an aircraft? What are the pros and cons?
NPG+ is standard issue in the 912S,
and perhaps the 912 also. If I'm not mistaken, Dave Leonard
is running NPG+ now, and I'm running NPG-R.
The Evan's marketing folks can give
you way more pros than I can think of, but I do think it's
working very well. The primary benefit is the fact that it's
native boiling point is in the 375F range, so you don't have to
worry about a cascade effect of boil over if you unexpectedly run hot, lose
pressure, etc. It's also not supposed to be subject to localized
boiling around hot spots in the engine. Evan's claims this as a big
benefit, but others, such as Tracy, think this boiling helps remove heat. It's a
bit more environmentally friendly too, so it won't hurt the rats in John's
hanger.
The high boiling temp means that
you don't need to run a pressurized system, which is my favorite
part. There's less stress on the system, and any leak that occurs,
will be much slower (initially) than if there was pressure. I
added an air separator tank, with a level sensor inside, so if I get a
leak, I'll know about it before it gets to the level of the top of the
engine. That was the best detection method I could think
of.
The down side is the cost, and the
fact that it doesn't transfer heat as effectively as traditional EG/water
mix. Your temps will almost certainly go up some, but at least you
won't boil over.
If the oil temp is below 180 F
but the coolant is above 220F, is this detrimental to the 13B??
Define "above" :-)
I don't think there's anything harmful about 220F, or a bit over that for
coolant, since cars do it all the time. I believe the power will
be reduced a bit at those temps though, and perhaps there will be more wear
on the engine. I've heard that, but can't say if
it's significant, or even true.
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