Al, I went back to some of my spreadsheets and I have for constant pressure (Cp) as 0.25 BTU/Lbm/F

Here is web site which gives it as 0.241 BTU/LBM/F at 32F Sea Level

http://www.uigi.com/physical_prop_e.html

So looks like you have the decimal off a bit.

Sorry, it took me so long, been out at the aircraft all day putting on the new right gear leg, and brakes, etc.

Ed A




  ----- Original Message -----   From: Al Gietzen   To: Rotary motors in aircraft   Sent: Friday, October 21, 2005 2:59 PM
  Subject: [FlyRotary] specific heat of air


  Ed, or Bill, or somebody; help me out here.  I was reviewing my calcs for air flow requirements, and find I used 0.02 Btu/cu. ft -F for the specific heat of air.  I don't know where that came from, and can only find it in joules/Kg - K.  By the time I do all the conversions to British units and mass to volume I now get quite a different number.



  What is a good number for air at about 1 atmosphere and, say 90F; in Btu per cu ft per degree F?



  Thanks,



  Al