the flow velocity with different pressure in close pipe

[kk7926]

A close pipe for gas circulation used fan,and i have measured the flow velocity in pipe under 1 atm. How to caculate the flow velocity under 0.1 atm.

[admin]

If pressure that you say is gauge, that means that absolute pressure is 2.013 is the one that you know velocity and 1.113 is the pressure that you need to calculate velocity. If the mass flow rate is the same that means due to pressure drop volume flow rate will be higher as well as velocity. If the temperatere is not changing volume flow rate ratio between two pressure levels are: q2 = q1 * p1 / p2 = q1 * 2.013 / 1.113 = q1 * 1.987. The same ratio is for velocity: v2 = 1.987 * v1.