Calculation of liquid flow

Calculation of Fluid Flow

When we transport liquids through a pipe, we deal with the concepts of flow velocity v and volumetric flow rate Φ, and the cross-sectional area A of the pipe.

The relationship between volumetric flow rate, flow velocity, and cross-sectional area is: Φv = v x A

For the cross-sectional area of the pipe, we can substitute ¼π2. The formula that shows the relationship between volumetric flow rate and flow velocity becomes: Φv = v x ¼πd2

Example calculation:
Water flows through a round pipe with an internal diameter of 5 cm at a velocity of 4 m/s. Calculate how much water flows through this pipe per second and per hour.

Solution:
Φv = v x ¼πd2
Φv = 4 m/s x ¼π x 0.052m2
Φv = 0.0079 m3/s
Multiplying this by 3600 s/hour gives the flow rate per hour:

Φv = 0.0079 m3/s x 3600 s/hour Φv = 28 m3/hour.

In the same way, we can also calculate the required diameter of a pipe when the required volumetric flow rate and flow velocity are known.