How to calculate chilled water pipe size , i have got GPM and Velocity of the fluid. please help me?

Question

How to calculate chilled water pipe size , i have got GPM and Velocity of the fluid. please help me?

Answer 1

let's say you have m gpm and n ft/s

m  gal / min x (1 ft³ / 7.48 gal) x ( 1 s / n ft) x (1 min / 60s) = cross sectional area of pipe in ft²

and area = pi x d² / 4

or simple put....

m / 60n = pi x d² / 4

m / (15 pi n) = d²

d = √(m / (15 pi n))  with m in GPM and n in ft/s

example

say you want 100 gpm to flow with a  linear flow rate of 5 ft /s

d = √(100 / (15x 3.14 x 5) = 0.65 ft = 7.8 in

Answer 2

Get the GPM and the velocity into the same units. ie. m3/hr and m/h.

Then divide the m3/hr by the velocity and you will have required area in m2 (Call it A).

Then A = (PI x D^2)/4 so the internal diameter is of the pipe is (A x 4/PI)^0.5