Return-Path: Received: from [24.25.9.102] (HELO ms-smtp-03-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.1.5) with ESMTP id 2648654 for flyrotary@lancaironline.net; Thu, 23 Oct 2003 17:50:38 -0400 Received: from o7y6b5 (clt78-020.carolina.rr.com [24.93.78.20]) by ms-smtp-03-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id h9NLoYhg027920 for ; Thu, 23 Oct 2003 17:50:35 -0400 (EDT) Message-ID: <004401c399af$5ece22c0$1702a8c0@WorkGroup> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: New cooling Model example Date: Thu, 23 Oct 2003 17:48:18 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0041_01C3998D.D7795F40" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_0041_01C3998D.D7795F40 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable =20 Ed; I looked it over to maybe make some comments; but I don't know what = I'm looking at. Maybe I missed because I haven't read previous posts, = but general questions are; What sort of modeling is this, empirical or theoretical? I don't see = any formulas in the spreadsheet. What are the independant variables (input) and what are the dependant = variables (output)? Is this for a specific airplane? Fixed HE configuration? Only specific point is the 35% penalty for "thick" radiator, but the = thickness is fine as long as you have sufficient pressure recovery in = the inlet duct to overcome PD across the core and other losses. Anyway, I don't expect you to write a manual, but if you have nothing = else to do (yeah..right) educate me a little. Al Hi Al, Sorry about the pacuity of information on the model. The = Power/fuel flow and BTU generated are math models that take the BTU in = a gallon of gasoline, your rpm, air/fuel ratio, altitude, = temperature/air density and throttle setting to calculate the output = shown in the Results box. I feel 90-95% confident that those values are = within 5% of what a well set up rotary can do. However, what I sent out wasn't the active spreadsheet but simple a = cut and paste of the results of the three cases. I have provide a = couple of spreadsheets and was concerned about getting too many = partially completed versions out there. =20 The actual spreadsheet only permits you to input data in the white = color (uncolored cells). The rest are results. The cooling model (at this moment) is based on the heat transfer = equation Q =3D W*(Tout-Tin)*Cp for an air flow mass cooling system. = Basically it calculates the CFM of air flow through the specified = radiator (the two evaporator cores in this case and the RX=3D7 Stock oil = cooler) As noted I have "derated" the capacity of the thicker cores by 10% for = every inch thick they are over 1". Its true that they higher dynamic = pressure permits us to successfully use the thicker cores, but = everything I have read does indicate the air flow does meet increase = resistance. I have also found and added a delta T model which shows how much = temperature rise you would have in your air mass flow stream due to the = amount of mass flow AND the amount of BTU of heat you are rejecting into = that mass flow. I am trying to keep the model based on simple math relationships and = not use any slight of hand tricks. However, Since a radiator maker = provided the rule of thumb of 10% increased resistance per inch, I = decided to incorporate it instead of trying to calculate the pressure = recovery in the plenium and that effect on flow rate. The cooling model = seems to correlate fairly well with what us folks flying with the cores = are experiencing. There is another gent who is much better acquainted with such matters = than I working on the model to actually calculate how much heat moves = across the aluminum tube walls from the coolant into the air stream. = That way we can calculated the total surface area for any specified = radiator size and get some feel for the adequacy of a cooling system. If you would like a copy of the last spreadsheet I sent out to folks, = just let me know. Its cooling model is not quite to the point of the = one I based the Cases on, but you might enjoy playing with it. One last point, the model does not have any "loading" such as a prop = so you can get 10,000 rpm no problem. I have looked into providing such = "loading" but just so many variable inlcuding the prop and the airframe, = that I doubt it will ever show up in one of my models. I'll be at Shady Bend from tomorrow until late Sunday. Best Regards Ed Anderson ------=_NextPart_000_0041_01C3998D.D7795F40 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 

Ed;

 

I looked = it over=20 to maybe make some comments; but I don=92t know what I=92m looking at. =  Maybe=20 I missed because I haven=92t read previous posts, but general = questions=20 are;

 

What = sort of=20 modeling is this, empirical or theoretical?  I don=92t see any = formulas in=20 the spreadsheet.

What are = the=20 independant variables (input) and what are the dependant variables=20 (output)?

Is this = for a=20 specific airplane? Fixed HE configuration?

Only = specific=20 point is the 35% penalty for =93thick=94 radiator, but the thickness = is fine as=20 long as you have sufficient pressure recovery in the inlet duct to = overcome PD=20 across the core and other losses.

 

Anyway, = I don=92t=20 expect you to write a manual, but if you have nothing else to do = (yeah..right)=20 educate me a little.

 

Al

 

Hi=20 Al,

 

   =20 Sorry about the pacuity of information on the model.  The = Power/fuel flow=20 and BTU generated are math models that take the BTU in  a gallon = of=20 gasoline, your rpm, air/fuel ratio, altitude, temperature/air = density and=20 throttle setting to calculate the output shown in the Results = box.  I=20 feel 90-95% confident that those values are within 5% of what a well = set up=20 rotary can do.

 

However, = what I=20 sent out wasn't the active spreadsheet but simple a cut and paste of = the=20 results of the three cases.  I have provide a couple of = spreadsheets and=20 was concerned about getting too many partially completed versions out=20 there. 

 

The = actual=20 spreadsheet only permits you to input data in the white color = (uncolored=20 cells). The rest are results.

 

The = cooling model=20 (at this moment) is based on the heat transfer equation Q =3D = W*(Tout-Tin)*Cp=20 for an air flow mass cooling system.  Basically it calculates the = CFM of=20 air flow through the specified radiator (the two evaporator cores in = this case=20 and the RX=3D7 Stock oil cooler)

 

As noted = I have=20 "derated" the capacity of the thicker cores by 10% for every inch = thick they=20 are over 1".  Its true that they higher dynamic pressure permits = us to=20 successfully use the thicker cores, but everything I have read does = indicate=20 the air flow does meet increase resistance.

 

I have also found and added a delta T model which shows = how much=20 temperature rise you would have in your air mass flow stream due to = the amount=20 of mass flow AND the amount of BTU of heat you are rejecting into that = mass=20 flow.

 

I am trying to keep the = model based=20 on simple math relationships and not use any slight of hand = tricks. =20 However, Since a radiator maker provided the rule of thumb of 10% = increased=20 resistance per inch, I decided to incorporate it instead of trying to=20 calculate the pressure recovery in the plenium and that effect on flow = rate.  The cooling model seems to correlate fairly well with what = us=20 folks flying with the cores are experiencing.

 

There is another gent who = is much=20 better acquainted with such matters than I working on the model to = actually=20 calculate how much heat moves across the aluminum tube walls from the = coolant=20 into the air stream.  That way we can calculated the total = surface area=20 for any specified radiator size  and get some feel for the = adequacy of a=20 cooling system.

 

If you would like a copy = of the last=20 spreadsheet I sent out to folks, just let me know.  Its cooling = model is=20 not quite to the point of the one I based the Cases on, but you might = enjoy=20 playing with it.

 

One last point, the model = does not=20 have any "loading" such as a prop so you can get 10,000 rpm no = problem. =20 I have looked into providing such "loading" but just so many variable=20 inlcuding the prop and the airframe, that I doubt it will ever show up = in one=20 of my models.

 

I'll be at Shady Bend = from tomorrow=20 until late Sunday.

 

Best Regards

 

Ed=20 Anderson

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