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PV=nrT
I'm going to exclude Temp and entropy just to make things easy, but it is important here, since it helps calculate the efficiency of the compressor and we always get a temp increase from the entropy.... So, assume nrT=constant
P1= ATM
P2-Starting pressure
P3=Ending pressure
Vt=Volume Tank
V2=compressed air volume P2
V3=compressed air volume P3
Atmospheric Volume in the tank at P2
V2=Vt*P2/p1
V3=vt*p3/p1
dV=V3-V2
Compressor CFM average for fill tank from P2 to P3
=(V3-V3)/t
=((Vt*P3/p1)-(vt*p2/p1))/t=Vt*(p3/p1-p2/p1)/t
=Vt*(p3/p1-p2/p1)/t
=4*(((100+15)/15)-((70+15)/15))/1.67
=4*(115/15-85/15)/1.67
=4*(7.67-5.67)/1.67=4.8 CFM
__________________
James
The pessimist complains about the wind; the optimist expects it to change; the engineer adjusts the sails.- William Arthur Ward (1921-1994)
Red-beard for President, 2020
Last edited by red-beard; 12-22-2008 at 07:06 AM..
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