CALCULATION OF DISCHARGE PIPE INNER DIAMETER FOR COMPRESSED AIR SYSTEM

 Determine the discharge pipe inner diameter size (in mm) for compressed air system, having following parameters.

 Compressed Air Flow at NTP (FAD) = 1000 Nm3/hr

 Discharge Air Pressure = 7 bar(g)

 Discharge Air Temperature = 35 o C

 Air Velocity = 7 m/s.

 Atmospheric Pressure = 1.013 bar

CALCULATION:

Actual Condition                         vs                  NTP Condition

 P2 x V2 / T2                                                  = P1 x V1 / T1

 (1.013 + 7) x V2 / (273 + 35)                       = 1.013 x 1000 / 273

 V1, actual flow rate = 142.6 m3/hr

   = 0.0396 m3/s 

 Flow rate (m3/s) = Area, in mtr2 x Velocity (m/s)

 Area, in mtr2 = Flow rate (m3/s) / Velocity (m/s)

= 0.0396 / 7 = 0.0057 m2

 A = π (di2/4) = 0.0057 m2

 Pipe, in mm = di = 0.085 m = 85 mm 

= say 90 mm