Return-Path: Received: from fed1rmmtao06.cox.net ([68.230.241.33] verified) by logan.com (CommuniGate Pro SMTP 4.2.8) with ESMTP id 611167 for flyrotary@lancaironline.net; Tue, 18 Jan 2005 00:17:53 -0500 Received-SPF: none receiver=logan.com; client-ip=68.230.241.33; envelope-from=daveleonard@cox.net Received: from davidandanne ([68.111.224.107]) by fed1rmmtao06.cox.net (InterMail vM.6.01.04.00 201-2131-117-20041022) with SMTP id <20050118051721.SCCT17071.fed1rmmtao06.cox.net@davidandanne> for ; Tue, 18 Jan 2005 00:17:21 -0500 From: "DaveLeonard" To: "Rotary motors in aircraft" Subject: RE: [FlyRotary] Re: Switching to Evans NPG+ Date: Mon, 17 Jan 2005 21:19:27 -0800 Message-ID: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0049_01C4FCDA.397A8F60" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook IMO, Build 9.0.2416 (9.0.2910.0) X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 In-Reply-To: Importance: Normal This is a multi-part message in MIME format. ------=_NextPart_000_0049_01C4FCDA.397A8F60 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 8bit Marv, I agree completely with everything you said. I fully plan to keep my pressure system in place and continue to monitor the pressure as a way to detect leaks. The beauty of NPG is that if the system does loose pressure, it does not change the ability to cool. You mention coolant vapor around hot spots. Evans touts its ability to resist that vapor film as one of its strongest points, and it makes sense. Even unpressurized 370 + degree boiling point is worlds better than the 265*F boiling point of pressurized 50/50. So I do believe that NPG will be better at preventing that vapor film than 50/50 even pressurized up into the 25psi range. I'm not saying that this stuff is magic. And I don't believe it can compensate for an inadequate cooling system (like pure water might), but it does offer some advantages that I am starting to appreciate. From the Evans Web site, here is some technical stuff: COMPARISON OF COOLANT PARAMETERS Water 50/50 EGW Evans NPG Evans NPG+ Boiling Point 121° C (250° F) (1 atm plus 15 psig) 129° C (264° F) (1 atm plus 15 psig) 187° C (369° F) (1 atm plus 0 psig) 191° C (375° F) (1 atm plus 0 psig) -------------------------------------------------------------------------- Viscosity 10° C (50° F) cp 1.2 5.0 115 58 80° C (176° F) cp .37 1.0 4.5 3.7 100° C (212° F) cp .28 0.7 2.8 2.3 -------------------------------------------------------------------------- Density 20° C (68° F) spec grav 1.00 1.066 1.038 1.091 20° C (68° F) lbs/gal 8.32 8.87 8.64 9.08 -------------------------------------------------------------------------- Specific Heat 80° C (176° F) Btu/lb/°F 1.00 0.81 0.68 0.64 100° C (212° F) Btu/lb/°F 1.01 0.82 0.71 0.66 -------------------------------------------------------------------------- Heat of Vaporization cal/mole 9,700 9,800 12,500 12,050 -------------------------------------------------------------------------- Vapor Pressure 80° C (176° F) mm Hg 360 270 8 6 80° C (176° F) kPa 475 360 11 8 -------------------------------------------------------------------------- Surface Tension 25° C (77° F) dyn/cm 72 56 36 44 -------------------------------------------------------------------------- > > Try and remember that the rules for what happens inside an engine > at sea level > are different than what goes on at 15,000 feet. While the NPG+ > may not boil > until 396*F at sea level, I'm certain that it's a different beast > at altitude. > The guy who engineered the Eagle was livid when we told him that Evans > recommended a pressureless system... part of the reason for the > pressure is to > keep the coolant pressed firmly against the metal surfaces it's trying to > cool. Even if you have a high boiling point, when the metal temperatures > exceed it the boiling will happen and without the pressure to > insure coolant > contact, pretty soon everything is surrounded by a cloud of PG > steam (well, > maybe not a "cloud", but all the hotspots will be working > overtime keeping the > coolant boiling next to them). Those metal temps quickly build, > the areas > where the coolant has turned to vapor grow, and the problem feeds > on itself > until the system goes completely out of control. At this point your > pressureless system vents itself, throwing out what's left of the > coolant and > the engine is toast. The point here is that there are more > reasons for having > a pressurized system in an airplane than meets the eye. > > One more thing... with a pressurized system you can alarm it for a low > pressure situation. If something goes wrong with the coolant > system (like you > spring a leak) the pressure will likely go down before you see a rise in > temps. If the system is setup to run at 20psi and you alarm it > at 15, when > you see that master warning you know that pretty soon you're > probably going to > overheat. Just another chance to get a jump on things that you pass up > without pressure. > > > > > >> Homepage: http://www.flyrotary.com/ > >> Archive: http://lancaironline.net/lists/flyrotary/List.html ------=_NextPart_000_0049_01C4FCDA.397A8F60 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Marv, I agree completely with everything you = said.  I fully=20 plan to keep my pressure system in place and continue to monitor the = pressure as=20 a way to detect leaks.  The beauty of NPG is that if the system = does loose=20 pressure, it does not change the ability to cool.

You mention = coolant=20 vapor around hot spots.  Evans touts its ability to resist that = vapor film=20 as one of its strongest points, and it makes sense.  Even = unpressurized 370=20 + degree boiling point is worlds better than the 265*F boiling point of=20 pressurized 50/50.  So I do believe that NPG will be better at = preventing=20 that vapor film than 50/50 even pressurized up into the 25psi = range.

I'm=20 not saying that this stuff is magic.  And I don't believe it can = compensate=20 for an inadequate cooling system (like pure water might), but it does = offer some=20 advantages that I am starting to appreciate.

From the Evans Web = site,=20 here is some technical stuff:
COMPARISON OF COOLANT = PARAMETERS
    Water 50/50 EGW Evans NPG Evans=20 NPG+
           
Boiling Point   121=B0 C (250=B0 F)
(1 atm=20 plus 15 psig)		 129=B0 C (264=B0 F)
(1 atm=20 plus 15 psig) 		187=B0 C (369=B0 F)
(1 atm=20 plus 0 psig) 		191=B0 C (375=B0 F)
(1 atm=20 plus 0 psig)
Viscosity          
    10=B0 C (50=B0 F) cp 1.2 5.0 115 58
    80=B0 C (176=B0 F) cp .37 1.0 4.5 3.7
   100=B0 C (212=B0 F) cp .28 0.7 2.8 2.3
 
Density          
    20=B0 C (68=B0 F) spec grav 1.00 1.066 1.038 1.091
    20=B0 C (68=B0 F) lbs/gal 8.32 8.87 8.64 9.08
Specific Heat          
    80=B0 C (176=B0 F) Btu/lb/=B0F 1.00 0.81 0.68 0.64
   100=B0 C (212=B0 F) Btu/lb/=B0F 1.01 0.82 0.71 0.66
Heat of Vaporization cal/mole 9,700 9,800 12,500 12,050
Vapor Pressure          
    80=B0 C (176=B0 F) mm Hg 360 270 8 6
    80=B0 C (176=B0 F) kPa 475 360 11 8
Surface Tension          
    25=B0 C (77=B0 F) dyn/cm 72 56 36 44

 
 


>
> Try and remember that the rules for what happens = inside an=20 engine
> at sea level
> are different than what goes on at = 15,000=20 feet.  While the NPG+
> may not boil
> until 396*F at = sea=20 level, I'm certain that it's a different beast
> at=20 altitude.
>  The guy who engineered the Eagle was livid when = we told=20 him that Evans
> recommended a pressureless system... part of the = reason=20 for the
> pressure is to
> keep the coolant pressed firmly = against=20 the metal surfaces it's trying to
> cool.  Even if you have a = high=20 boiling point, when the metal temperatures
> exceed it the boiling = will=20 happen and without the pressure to
> insure coolant
> = contact,=20 pretty soon everything is surrounded by a cloud of PG
> steam=20 (well,
> maybe not a "cloud", but all the hotspots will be = working
>=20 overtime keeping the
> coolant boiling next to them).  Those = metal=20 temps quickly build,
> the areas
> where the coolant has = turned to=20 vapor grow, and the problem feeds
> on itself
> until the = system=20 goes completely out of control.  At this point your
> = pressureless=20 system vents itself, throwing out what's left of the
> coolant = and
>=20 the engine is toast.  The point here is that there are more
> = reasons=20 for having
> a pressurized system in an airplane than meets the=20 eye.
>
> One more thing... with a pressurized system you can = alarm=20 it for a low
> pressure situation.  If something goes wrong = with the=20 coolant
> system (like you
> spring a leak) the pressure = will likely=20 go down before you see a rise in
> temps.  If the system is = setup to=20 run at 20psi and you alarm it
> at 15, when
> you see that = master=20 warning you know that pretty soon you're
> probably going = to
>=20 overheat.  Just another chance to get a jump on things that you = pass=20 up
> without pressure.
>
>  =20 <marv>
>  
>
> >>  = Homepage: =20 http://www.flyrotary.com/
> >> =20 Archive:   http://lancaironline.net/lists/flyrotary/List.html=20

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