Mailing List flyrotary@lancaironline.net Message #2394
From: Marko Bewersdorff <marko@bewersdorff.com>
Subject: RE: [FlyRotary] Re: Cooling?
Date: Mon, 4 Aug 2003 14:26:01 -0700
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
I just plunked temperature into the equation, no pressure change.
 
As long as your plane doesn't read this email and you keep it in the dark about the theory it should just work fine. I think the only issue might be more drag then needed - theoretically.
 
re
 
Marko
-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]On Behalf Of Al Gietzen
Sent: Monday, August 04, 2003 10:29 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Cooling?

 

 

doesn't that formula depend on absolute temperature like kelvin or so? where zero degree is minus 459 degree F or minus 273 Celsius.
the ratio of expansion should be something like:
inlet air: 20 degree Celsius (68F) or 293 Kelvin
outlet air: 50 degree celsius (122F) or 323 Kelvin
then
323 over 293 for a change in temperature gives
then the Volume change of more like 1.2

there is some additional expansion due to the pressure difference.

Regards

Marko

Marko;

You got me there.  You’re right, it needs to be the ratio of absolute temp.  That gives a ratio of inlet to outlet for the 80 F in and 135 F out of about 1.1.  Also for the case you give; 323/293 is 1.1; not 1.2, or did you factor in some additional volume change for pressure. 

Gees .. you mean now I have to go back and rework my rad outlets?

Al

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