X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [24.25.9.102] (HELO ms-smtp-03-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 5.0.7) with ESMTP id 964542 for flyrotary@lancaironline.net; Wed, 01 Feb 2006 23:27:23 -0500 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.102; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-025-165.carolina.res.rr.com [24.74.25.165]) by ms-smtp-03-eri0.southeast.rr.com (8.13.4/8.13.4) with SMTP id k124QagG014361 for ; Wed, 1 Feb 2006 23:26:38 -0500 (EST) Message-ID: <000f01c627b0$df9ec710$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: sutability of NPG for rotary engine use Date: Wed, 1 Feb 2006 23:26:43 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_000C_01C62786.F66BAAF0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_000C_01C62786.F66BAAF0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hi Mike, I agree, You certainly don't have to keep the cooling system stock - = after all this IS experimentation. My point was that I did not believe = that NPG was suited to a 13B with a stock cooling system. You can = certainly disagree with that statement - but, I (and perhaps others) = would like to know why.=20 To better deal with the properties of NPG, I pointed out that you = would likely need to make some modifications such as increasing the flow = rate (pump speed) of the NPG as well as providing more power = (clog/serpentine belts) to the water pump to address the added = resistance due to its much higher viscosity that the 50/50 mixture. = Also as others have pointed out, you would probably not want to use = the GM cores (that many of us use) due to their smaller passages. So could the 13B coolant system be modified to better deal with some of = the NPG properties, no doubt in my mind that it is certainly possible to = do so. However, I am not convinced that there is sufficient benefit = derived from the use of NPG that modification over the stock system = designed for a 50/50 mixture would be justified (in my mind at least). =20 I am eager for some one do this experiment (other than me {:>)) - = however, based on what happened to Dave's engine after he replace the = 50/50 mixture with NPG - I would suggest proceeding cautiously. Not = saying NPG was the cause - we simply don't know at this time (and may = never), but that was the only change he made before having his severe = engine problems.=20 Also, one might care that should a 100% pure glycol (ethylene or = propylene) liquid land on a hot exhaust - the probability of ignition = and fire is fairly high and something that should be considered. = Having had a brake fire while on the ground, I do not care to have a = coolant fire in the air. However , I will retract my earlier statement that we ALL agree that NPG = is not suited for a 13B with a stock cooling system. It was mostly made = in jest in the first place. Best Regards Ed . ----- Original Message -----=20 From: Michael LaFleur=20 To: Rotary motors in aircraft=20 Sent: Wednesday, February 01, 2006 10:36 PM Subject: [FlyRotary] Re: sutability of NPG for rotary engine use Well, I'm not ready to agree with that conclusion yet. And who say's = we need to keep the cooling system stock? Mike Ed Anderson wrote: Thanks for your assessment, Monty. Scares me a bit that we all (more or less) agree that the NPG is = probably not well suited to the stock rotary coolant system {:>) Ed ----- Original Message -----=20 From: M Roberts=20 To: Rotary motors in aircraft=20 Sent: Wednesday, February 01, 2006 8:35 PM Subject: [FlyRotary] sutability of NPG for rotary engine use I wouldn't worry about the theory behind mdot*Cp*deltaT too much. = This has been tested thoroughly. As long as your Cp number is correct = the calculation will be nuts on. The place you get into trouble is = measuring the constants for Cp or for a heat transfer coefficient. Your = analysis looks good to me Ed. The point Ernest made is a valid one. Cp = is per unit mass. A more dense fluid will transfer more heat per volume = flow than a less dense fluid. Bill S. also makes some good points. The main thing I have to add is: it would be nice to know what the = convection coefficient is for NPG. That is what gives the heat transfer = between the hot metal and the coolant. A more viscous fluid would tend = to have a thicker boundary layer and less turbulence. That could cause = problems. The turbulence and mixing of the boundary layer help to = transfer heat.=20 I also would be cautious about the vapor pressure. Boiling is not = a bad thing. It is a good thing. The heat transfer coefficient for a = phase change (liquid to gas) is infinite. This helps to cool a hot spot. = We are talking about sub cooled boiling here where the bulk liquid is = cooler than the boiling point. Locally the liquid boils and transfers = all the heat the metal can move. The limiting factor is actually the = metal conduction for this case. The bubbles of vapor are cooled by the = surrounding coolant and collapse. Put a pot on the stove and watch as = you transfer from sub-cooled to nucleate and finally bulk boiling. You = can see the process happen.=20 Both bulk and nucleate boiling are to be avoided. Sub cooled = boiling, a thin boundary layer and turbulence are all good things. NPG = strikes out on all three. In addition it requires more power to pump and = the pressure drop through the evaporator core type coolers at low temps = is suspect.=20 In short: The 13b was developed to use water/glycol as a coolant. To properly validate NPG you need a dyno and a lot of = thermocouples, plus a way to measure the mass flow of the coolant, = pressure drops, pump power, and the heat transfer coefficient.=20 Anybody got that laying around in their hangar? Do you want to be a guinea pig? I would not use NPG. Monty ------=_NextPart_000_000C_01C62786.F66BAAF0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Hi Mike,
 
I agree, You certainly don't have to keep the = cooling=20 system stock - after all this IS experimentation.  My point was = that I did=20 not believe that NPG was suited to a 13B with a stock cooling = system.  You=20 can certainly disagree with that statement - but, I (and perhaps others) = would=20 like to know why. 
 
  To better deal with the properties of = NPG,   I=20 pointed out that you would likely need to make some modifications such = as=20 increasing the flow rate (pump speed) of the NPG as well as providing =  more=20 power (clog/serpentine belts)  to the water pump to address the = added=20 resistance due to its much higher viscosity that the 50/50 = mixture. =20 Also  as  others have pointed out, you would probably not want = to use=20 the GM cores (that many of us use)  due to their smaller=20 passages.
 
So could the 13B coolant system be modified to = better deal=20 with some of the NPG properties, no doubt in my mind that it is = certainly=20 possible to do so.  However, I am not convinced that there is = sufficient=20 benefit derived from the use of NPG that modification over the stock = system=20 designed for a 50/50 mixture would be justified (in my mind at = least). =20
 
I am eager for some one do this experiment = (other than me=20 {:>))  - however, based on what happened to Dave's engine = after he=20 replace the 50/50 mixture with NPG - I would suggest proceeding=20 cautiously.  Not saying NPG was the cause - we simply don't know at = this=20 time (and may never), but that was the only change he made before having = his=20 severe engine problems. 
 
 Also, one might care that should a 100% = pure glycol=20 (ethylene or propylene)  liquid  land on a hot exhaust - the=20 probability of ignition and fire is fairly high and  something that = should=20 be considered.  Having had a brake fire while on the ground, I do = not care=20 to have a coolant fire in the air.
 
However , I will retract my earlier statement = that=20 we ALL agree that NPG is not suited for a 13B with a stock cooling=20 system.  It was mostly made in jest in the first = place.
 
Best Regards
 
Ed
 
 
 
.
 
 
----- Original Message -----
From:=20 Michael LaFleur
Sent: Wednesday, February 01, = 2006 10:36=20 PM
Subject: [FlyRotary] Re: = sutability of=20 NPG for rotary engine use

Well, I'm not ready to agree with that conclusion = yet. And=20 who say's we need to keep the cooling system=20 stock?

Mike

Ed Anderson <eanderson@carolina.rr.com&g= t;=20 wrote:
Thanks for your assessment, = Monty.
 
Scares me a bit that we all (more or less) = agree that=20 the NPG is probably not well suited to the stock rotary coolant = system=20 {:>)
 
Ed
-----=20 Original Message -----
From:=20 M=20 Roberts To:=20 Rotary motors in = aircraft=20 Sent:=20 Wednesday, February 01, 2006 8:35 PM Subject:=20 [FlyRotary] sutability of NPG for rotary engine use

I wouldn't worry about the theory = behind=20 mdot*Cp*deltaT too much. This has been tested thoroughly. As long = as your=20 Cp number is correct the calculation will be nuts on. The place = you get=20 into trouble is measuring the constants for Cp or for a heat = transfer=20 coefficient. Your analysis looks good to me Ed. The point Ernest = made is a=20 valid one. Cp is per unit mass. A more dense fluid will transfer = more heat=20 per volume flow than a less dense fluid. Bill S. also makes some = good=20 points.
 
 
The main thing I have to add is: = it would be=20 nice to know what the convection coefficient is for NPG. That is = what=20 gives the heat transfer between the hot metal and the coolant. A = more=20 viscous fluid would tend to have a thicker boundary layer and less = turbulence. That could cause problems. The turbulence and mixing = of the=20 boundary layer help to transfer heat.
 
I also would be cautious about = the vapor=20 pressure. Boiling is not a bad thing. It is a good thing. The heat = transfer coefficient for a phase change (liquid to gas) is = infinite. This=20 helps to cool a hot spot. We are talking about sub cooled boiling = here=20 where the bulk liquid is cooler than the boiling point. Locally = the liquid=20 boils and transfers all the heat the metal can move. The limiting = factor=20 is actually the metal conduction for this case. The bubbles of = vapor are=20 cooled by the surrounding coolant and collapse. Put a pot on = the=20 stove and watch as you transfer from sub-cooled to nucleate and = finally=20 bulk boiling. You can see the process happen. 
 
Both bulk=20 and nucleate boiling are to be avoided. Sub cooled = boiling,=20 a thin boundary layer and turbulence are all good = things. NPG=20 strikes out on all three. In addition it requires more power to = pump and=20 the pressure drop through the evaporator core type coolers at low = temps is=20 suspect. 
 
In short:
 
The 13b was developed to use = water/glycol as=20 a coolant.
 
To = properly validate NPG you=20 need a dyno and a lot of thermocouples, plus a way to measure the = mass=20 flow of the coolant, pressure drops, pump power, and the heat = transfer coefficient.
 
Anybody got that laying around in = their=20 hangar?
 
Do = you want to be a=20 guinea pig?
 
I would not use NPG.
 
Monty

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