REFLECTOR:Re: NPG+
Chuck Jensen
reflector@tvbf.org
Mon, 19 Apr 2004 08:49:24 -0400
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John,
I think I've got it straight. You're right (which is probably not a
surprise to you), in that boiling does go on in a pressurized H2O cooling
system. Nucleate boiling forms right at the metal surface and when the
bubble moves away from the metal, they immediately collapse. This is a very
effective heat transfer mechanism. If pressure on the system is lost, then
a steam layer will form on the metal, heat transfer will suffer greviously
and it would be a good idea to have a landing site in mind. So, the NPG+
cooled engine probably runs hotter since it won't support nucleate boiling
for good heat transfer. Is that good?
Chuck
-----Original Message-----
From: reflector-admin@tvbf.org [mailto:reflector-admin@tvbf.org]On Behalf Of
John Dibble
Sent: Sunday, April 18, 2004 6:25 PM
To: reflector@tvbf.org
Subject: Re: REFLECTOR:Re: NPG+
The few psig of the sealed system simply raises the boiling point by a few
degrees - boiling still occurs, just at a higher temp. I'm simply not
buying the "insulation by the steam layer" concept. The steam layer is part
of the boiling process, specifically when the boiling rate is very high. I
question if a steam layer exists in an engine cooling system, but if it
does, it indicates a very high rate of heat transfer. If insulation did
happen, the steam generation would slow and the steam layer would collapse.
A non-boiling coolant will have a much lower heat transfer rate and that
translates to a higher temperature at the cylinder jacket wall.
The only way the NPG+ makes sense is if water-cooled engines have much lower
CHTs/EGTs than air-cooled and it is desirable to increase them.
John
Chuck Jensen wrote:
John,I can't pass up an opportunity to show my ignorance (and there are
many!), but I thought the reason for keeping the water coolant under
pressure was so it would not boil against the cylinder jacket. As we know,
water has a higher boiling point under pressure, so the few psig of the
sealed coolant system keeps the water from boiling when it hits the hot
engine components. When we take the cap off...every so carefully...that
relieves the pressure and the hot water near-instantly boils; spitting like
a cobra into the face of the unwary. The NPG+ article talks about how it
won't "boil" and leave a layer of steam against the hot metal. Steam is
actually quite a good insulator so the engine metal will get even hotter if
a layer of steam is present. NPG+ says, since their solution won't boil,
there will never been a steam layer that thermally insulates the engine
metal and thus the heat will be conducted away more efficiently; reducing
the potential for knock/predetonation.I got lost in the issue about the
engine running hotter with NPG+. Unless they mean the whole engine can run
hotter while critical components are kept cooler, which will reduce the
potential for mechanical damage from predetonation while enjoying the ever
so slight improvement of a hotter engine? Measuring such gains probably
falls in the realm of the new "Nanotechnology."With all that said, some of
their claims leave me thinking about the 'ole West Medicine Wagon and their
medicinal potions. When the claims start filling up a half-page, I start
thinking about half-truths.Chuck
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<DIV><SPAN class=359083212-19042004>John,</SPAN></DIV>
<DIV><SPAN class=359083212-19042004></SPAN> </DIV>
<DIV><SPAN class=359083212-19042004>I think I've got it straight. You're
right (which is probably not a surprise to you), in that boiling does go on
in a pressurized H2O cooling system. Nucleate boiling forms right at the
metal surface and when the bubble moves away from the
metal, they immediately collapse. This is a very effective heat
transfer mechanism. If pressure on the system is lost, then a steam layer
will form on the metal, heat transfer will suffer greviously and it would
be a good idea to have a landing site in mind. So, the NPG+ cooled engine
probably runs hotter since it won't support nucleate boiling for good heat
transfer. Is that good?</SPAN></DIV>
<DIV><SPAN class=359083212-19042004></SPAN> </DIV>
<DIV><SPAN class=359083212-19042004>Chuck</SPAN></DIV>
<BLOCKQUOTE dir=ltr style="MARGIN-RIGHT: 0px">
<DIV class=OutlookMessageHeader dir=ltr align=left><FONT
face=Tahoma>-----Original Message-----<BR><B>From:</B>
reflector-admin@tvbf.org [mailto:reflector-admin@tvbf.org]<B>On Behalf Of
</B>John Dibble<BR><B>Sent:</B> Sunday, April 18, 2004 6:25 PM<BR><B>To:</B>
reflector@tvbf.org<BR><B>Subject:</B> Re: REFLECTOR:Re:
NPG+<BR><BR></FONT></DIV>The few psig of the sealed system simply raises the
boiling point by a few degrees - boiling still occurs, just at a higher
temp. I'm simply not buying the "insulation by the steam layer"
concept. The steam layer is part of the boiling process, specifically
when the boiling rate is very high. I question if a steam layer exists
in an engine cooling system, but if it does, it indicates a very high rate of
heat transfer. If insulation did happen, the steam generation would slow
and the steam layer would collapse. A non-boiling coolant will have a
much lower heat transfer rate and that translates to a higher temperature at
the cylinder jacket wall. <BR>The only way the NPG+ makes sense is if
water-cooled engines have much lower CHTs/EGTs than air-cooled and it is
desirable to increase them.
<P>John
<P>Chuck Jensen wrote:
<BLOCKQUOTE TYPE="CITE">
<STYLE></STYLE>
<SPAN class=031475220-18042004>John,</SPAN><SPAN
class=031475220-18042004></SPAN><SPAN class=031475220-18042004>I can't pass
up an opportunity to show my ignorance (and there are many!), but I thought
the reason for keeping the water coolant under pressure was so it would not
boil against the cylinder jacket. As we know, water has a higher
boiling point under pressure, so the few psig of the sealed coolant system
keeps the water from boiling when it hits the hot engine components.
When we take the cap off...every so carefully...that relieves the pressure
and the hot water near-instantly boils; spitting like a cobra into the face
of the unwary. </SPAN><SPAN class=031475220-18042004></SPAN><SPAN
class=031475220-18042004>The NPG+ article talks about how it won't "boil"
and leave a layer of steam against the hot metal. Steam is actually
quite a good insulator so the engine metal will get even hotter if a layer
of steam is present. NPG+ says, since their solution won't boil, there
will never been a steam layer that thermally insulates the engine metal and
thus the heat will be conducted away more efficiently; reducing the
potential for knock/predetonation.</SPAN><SPAN
class=031475220-18042004></SPAN><SPAN class=031475220-18042004>I got lost in
the issue about the engine running hotter with NPG+. Unless they mean
the whole engine can run hotter while critical components are kept cooler,
which will reduce the potential for mechanical damage from predetonation
while enjoying the ever so slight improvement of a hotter engine?
Measuring such gains probably falls in the realm of the new
"Nanotechnology."</SPAN><SPAN class=031475220-18042004></SPAN><SPAN
class=031475220-18042004>With all that said, some of their claims leave me
thinking about the 'ole West Medicine Wagon and their medicinal
potions. When the claims start filling up a half-page, I start
thinking about half-truths.</SPAN><SPAN
class=031475220-18042004></SPAN><SPAN
class=031475220-18042004>Chuck</SPAN></BLOCKQUOTE></BLOCKQUOTE></BODY></HTML>
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