Law of compressed air:
One of the most significant gas laws - Marriott and Gay-Lussac law states :
P x V = a x T
P : absolute pressure (Pa)
V : volume (ft3 m3)
T: absolute temperature (K)
a : constant
This relation is used within the compressor : constant air volume is pumped from the compressor chamber, and the volume decreases. This decrease causes an increase in both the pressure and the temperature of the air.
Flow is equivalent to the quantity of compressed air conveyed in a given section per unit of time.
Q = A1 x V1 = A2 x V2
Q : flow (cfm)
A : flow section (ft²)
V : speed (ft/min)
The INTERNATIONAL SYSTEM of flow is cubic metres / second (m3/s) , but we generally use l/s, m3/h or cfm. This varies according to several factors, and, in particular, to the air pressure and the length/ID of the pipe, which conveys compressed air.
Pressure drop calculation:
When fluid flows in a straight pipe, the flow can depend on two factors : the laminar rate or the rate of turbulence, according to the value of the Reynolds Number " R ".
R=d X w/v
d: ID of the pipe (ft or m)
w: avarage speed (ft/min or m/s)
v: kinematic vicosity (ft2/min or m2/s)
Compressed air in the system is determined by the rate of turbulence
Turbulence caused by friction, reduces the volume of compressed air conveyed through the pipe. Moreover, the internal pipe walls may have an irregular surface.These factors, combined with flow, create pressure drop - resulting from friction caused by the dynamics of air flow within the pipe.Pressure drop values are shown as dP and are stated in PSI or bar.