Return-Path: Received: from [65.54.169.53] (HELO hotmail.com) by logan.com (CommuniGate Pro SMTP 4.3c1) with ESMTP id 724198 for flyrotary@lancaironline.net; Thu, 10 Feb 2005 16:50:49 -0500 Received-SPF: pass receiver=logan.com; client-ip=65.54.169.53; envelope-from=lors01@msn.com Received: from mail pickup service by hotmail.com with Microsoft SMTPSVC; Thu, 10 Feb 2005 13:50:02 -0800 Message-ID: Received: from 4.174.0.49 by BAY3-DAV23.phx.gbl with DAV; Thu, 10 Feb 2005 21:49:54 +0000 X-Originating-IP: [4.174.0.49] X-Originating-Email: [lors01@msn.com] X-Sender: lors01@msn.com From: "Tracy Crook" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Heating the Fuel Date: Thu, 10 Feb 2005 16:49:51 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_003A_01C50F90.8A124E90" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: MSN 9 Seal-Send-Time: Thu, 10 Feb 2005 16:49:51 -0500 X-MimeOLE: Produced By MSN MimeOLE V9.10.0009.2900 X-OriginalArrivalTime: 10 Feb 2005 21:50:02.0995 (UTC) FILETIME=[79B1B430:01C50FBA] This is a multi-part message in MIME format. ------=_NextPart_000_003A_01C50F90.8A124E90 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable ALL of this discussion was based on the use of a wet-wing aluminum fuel = tank. The tank is the cooler. Lets assume that the fuel is indeed boiling. This is analogous to = piping steam into a cool metal tank. The steam will condense on the = walls of the tank (or the fuel in the tank) until the walls of the tank = get too hot. The question is how much heat will this tank with 175 MPH = air blowing on it dissipate before getting too hot. Bill says laminar = air will limit this to a great degree. I don't know. Back to real world data. I was able to cool my oil about 2 degrees = with return fuel cooling during cruise flight at 175 mph. I tried to = measure the temperature rise in the tank but the .1 degree resolution of = the instrument was too coarse to measure it. (40 minute test duration) = In other words, it didn't change significantly. This showed me that = the fuel flow needed to be much higher in order to get usable level of = cooling. It also showed that the fuel tank was far from it's maximum = heat dissipation capabilities. =20 Another useful factoid: The oil cooler will be giving about a 40 deg = delta (oil temp) at normal 13B oil flows and cruise power settings. =20 Tracy =20 <...it will be headed back to the tank where it will quickly be cooled = ..>How quickly? How exactly does does it cool it all that quickly? = You got a heat exchanger in the tank? How about if you're down to your = last 5 gal of fuel in the tank? How fast will fuel cool in your tank if = you have no air - fuel heat exchanger. In my tank it could take hours. = If Tracy's pump is returning 40 gph to the tank (and, we must infer, = burning about another 15 gph) that's a total of 55 gph through the pump. = Assuming a 25 gal tank (in each wing), that means at the end of an hour = you've got 10 gal left and recirculated 40 through the tank. The = average fuel in the tank over that hour would be 17.5 gal, so you've run = it all through your heat exchanger about 2.3 times. How hot do you = reckon it's going to be at the end of that hour? =20 Do the math ... it IS "the mother of all vapor locks" ... Jim S. DaveLeonard wrote:=20 Bill & Jim, first and most important, we are all in agreement that this = is not worth doing. However, you made a couple of assumptions that are not quiet accurate. First, the pumps from Tracy will return 40 gal/hr to = the tank (not 15 - I know, I monitor it in flight). Second, there will be a much higher rise in the fuel temp. Because the fuel would be going so slowly through the heat exchanger I would EXPECT it to reach the = temperature of the incoming coolant, or about a 100 deg rise. This will not cause = "the mother of all vapor locks" becuase it will be headed back to the tank = where it will quickly be cooled. How quickly? Quickly enough that the temp = of the fuel on its way to the engine will be no warmer than ambient. It matters not the volume of fuel in the tank (other than contact area). = I expect it to be the temp of the fuel going TO the engine to be at = ambient - and adding no additional risk of vapor lock. But, the coolant will still only drop about 3 deg, which is not enough = to make it worth it. Dave Leonard <... For a 10 degree rise in gasoline temperature you would get a 630/12000 =3D 0.0525 deg F drop in coolant temperature ...> OTOH, you'd soon heat your fuel to very near the coolant temp and have the mother of all vapor locks. If that's what you're looking for ... Jim S. William wrote: Dave, If you burn 10 g/hr, and are returning 15 g/hr to the tanks, that is 15*6 =3D 90 #/hr of gasoline, with a specific heat of ~.7Btu/#, that means you can transfer 90* 0.7 =3D 63 Btu/hr/degF rise in gasoline temperature. Your coolant flow is probably about 25 gallons/minute, =3D 25*60 =3D 1500 gallons/hour =3D ~1500*8 =3D 12000 #/hour. For a 10 = degree rise in gasoline temperature you would get a 630/12000 =3D 0.0525 deg F drop in coolant temperature. Doesn't seem worth it. * note: I used rounded figures for densities and flow rates and heat capacities. The fact remains that the flow mismatch makes this not do much. Bill Schertz KIS Cruiser # 4045 ----- Original Message ----- *From:* DaveLeonard = *To:* Rotary motors in aircraft = *Sent:* Sunday, February 06, 2005 11:46 PM *Subject:* [FlyRotary] Heating the Fuel In anticipation of the new turbo, I am considering ways to improve coolant cooling. Besides the obvious more air, more ducting, more radiator; I have been again toying with the idea of a heat exchanger. This time coolant to fuel. The plan would be to use a typical oil/water exchanger but use fuel instead of oil. I would use the fuel on the way back to the tank, and the coolant after it has already been cooled by the radiator. The fuel would then go back to the nice metal tank of the RV. I am looking for input on the implications of heating the fuel. I expect it would reach max temps of about 190 (usually a little cooler) but quickly cool once in the tank. Can the fuel tolerate that temp without vaporizing? It will probably expand in the tank but I don't expect that will occur faster than it is used up. I have no guess as to what temp will become steady state for the fuel pumped out of the tank. My guess is that it will not be much warmer than normal, but a slight increase in temp may help with vaporization. The last question is how much will it cool the coolant. My hope is about 10 deg but I doubt it will be quite that much. I know others have considered using the fuel to cool (Tracy) and I would appreciate your thoughts. Dave Leonard Homepage: http://www.flyrotary.com/ Archive: = http://lancaironline.net/lists/flyrotary/List.html =20 Homepage: http://www.flyrotary.com/ Archive: = http://lancaironline.net/lists/flyrotary/List.html =20 ------=_NextPart_000_003A_01C50F90.8A124E90 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
ALL of this discussion was based on the use of a wet-wing aluminum = fuel=20 tank.   The tank is the cooler.
 
Lets assume that the fuel is indeed boiling.  This is = analogous to=20 piping steam into a cool metal tank.  The steam will condense on = the walls=20 of the tank (or the fuel in the tank) until the walls of the tank get = too=20 hot.  The question is how much heat will this tank with 175 MPH air = blowing=20 on it dissipate before getting too hot.   Bill says laminar = air will=20 limit this to a great degree.  I don't know.
 
Back to real world data.   I was able to cool my oil = about 2=20 degrees with return fuel cooling during cruise flight at 175 mph.  = I tried=20 to measure the temperature rise in the tank but the .1 degree = resolution of=20 the instrument was too coarse to measure it.  (40 minute test=20 duration)  In other words, it didn't change = significantly.   This=20 showed me that the fuel flow needed to be much higher in order to get = usable=20 level of cooling.  It also showed that the fuel tank was far from = it's=20 maximum heat dissipation capabilities. 
 
Another useful factoid:   The oil cooler will be = giving=20 about a 40 deg delta (oil temp) at normal 13B oil flows and cruise power = settings.  
 
Tracy 
 

<...it will be headed back to the =
tank where it will quickly be cooled ...>
How=20 quickly?  How exactly does does it cool it all that = quickly?  You=20 got a heat exchanger in the tank?  How about if you're down to = your last=20 5 gal of fuel in the tank?  How fast will fuel cool in your tank = if you=20 have no air - fuel heat exchanger.  In my tank it could take = hours. =20

If Tracy's pump is returning 40 gph to the tank (and, we must = infer,=20 burning about another 15 gph) that's a total of 55 gph through the = pump. =20 Assuming a 25 gal tank (in each wing), that means at the end of an = hour you've=20 got 10 gal left and recirculated 40 through the tank.  The = average fuel=20 in the tank over that hour would be 17.5 gal, so you've run it all=20 through your heat exchanger about 2.3 times.  How hot do you = reckon=20 it's going to be at the end of that hour? 

Do the math = .. it IS=20 "the mother of all vapor locks" ... Jim S.

DaveLeonard wrote:=20 
Bill & Jim, first and most important, we are all in =
agreement that this is
not worth doing.  However, you made a couple of assumptions that are not
quiet accurate.  First, the pumps from Tracy will return 40 gal/hr to =
the
tank (not 15 - I know, I monitor it in flight).  Second, there will be a
much higher rise in the fuel temp.  Because the fuel would be going so
slowly through the heat exchanger I would EXPECT it to reach the =
temperature
of the incoming coolant, or about a 100 deg rise.  This will not cause =
"the
mother of all vapor locks" becuase it will be headed back to the tank =
where
it will quickly be cooled.  How quickly?  Quickly enough that the temp =
of
the fuel on its way to the engine will be no warmer than ambient.  It
matters not the volume of fuel in the tank (other than contact area).    =
  I
expect it to be the temp of the fuel going TO the engine to be at =
ambient -
and adding no additional risk of vapor lock.

But, the coolant will still only drop about 3 deg, which is not enough =
to
make it worth it.

Dave Leonard


  
<... For a 10 degree =
rise in gasoline temperature you would get a
630/12000 =3D 0.0525 deg F drop in coolant temperature ...>

OTOH, you'd soon heat your fuel to very near the coolant temp and have
the mother of all vapor locks.
If that's what you're looking for ... Jim S.

William wrote:

    
Dave,
If you burn 10 g/hr, and are returning 15 g/hr to the tanks, that is
15*6 =3D 90 #/hr of gasoline, with a specific heat of ~.7Btu/#, that
means you can transfer 90* 0.7 =3D 63 Btu/hr/degF rise in gasoline
temperature. Your coolant flow is probably about 25 gallons/minute, =3D
25*60 =3D 1500 gallons/hour =3D ~1500*8 =3D 12000 #/hour. For a 10 =
degree
rise in gasoline temperature you would get a 630/12000 =3D 0.0525 deg F
drop in coolant temperature.  Doesn't seem worth it.

* note: I used rounded figures for densities and flow rates and heat
capacities. The fact remains that the flow mismatch makes this not do
much.
Bill Schertz
KIS Cruiser # 4045

    ----- Original Message -----
    *From:* DaveLeonard <mailto:daveleonard@cox.net>
    *To:* Rotary motors in aircraft <mailto:flyrotary@lancairo=
nline.net>
    *Sent:* Sunday, February 06, 2005 11:46 PM
    *Subject:* [FlyRotary] Heating the Fuel

    In anticipation of the new turbo, I am considering ways to improve
    coolant cooling.  Besides the obvious more air, more ducting, more
    radiator; I have been again toying with the idea of a heat
    exchanger.  This time coolant to fuel.  The plan would be to use a
    typical oil/water exchanger but use fuel instead of oil.  I would
    use the fuel on the way back to the tank, and the coolant after it
    has already been cooled by the radiator.  The fuel would then go
    back to the nice metal tank of the RV.

    I am looking for input on the implications of heating the fuel.  I
    expect it would reach max temps of about 190 (usually a
    little cooler) but quickly cool once in the tank.  Can the fuel
    tolerate that temp without vaporizing?  It will probably expand in
    the tank but I don't expect that will occur faster than it is used
    up.  I have no guess as to what temp will become steady state for
    the fuel pumped out of the tank.  My guess is that it will not be
    much warmer than normal, but a slight increase in temp may help
    with vaporization.

    The last question is how much will it cool the coolant.  My hope
    is about 10 deg but I doubt it will be quite that much.  I know
    others have considered using the fuel to cool (Tracy) and I would
    appreciate your thoughts.

    Dave Leonard

      
 Homepage:  http://www.flyrotary.com/
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