Mass Flow Rate

The mass flow rate is defined as the mass of a liquid substance passing per unit of time. SI units are kilogram per second. The mass flow directly depends on the density, velocity of the liquid, and the area of the cross-section. It is also defined as the movement of mass per unit of time.

Formula for Mass Flow Rate

The formula can be written as,

\(m = \rho VA\)

\(\rho\) – Density of fluid
\(V\) – Velocity of liquid
\(A\) – Area of cross section

Solved Examples

Question 1. Given the density of a fluid as 1000 kg/m3, velocity as 50 m/s and area of cross-section as 10 cm2, determine the movement of mass per unit of time.

Solution. Given,
⍴= 1000 kg/m3
V = 50 m/s
A = 10 cm2 = 0.1 m2

m = ⍴VA
m = 1000 x 50 x 0.1

∴ m = 5000 kg/s

Question 2. A fluid moves at 20 m/s through a tube. The tube has an area of 0.5 m2. The density of the fluid is 1.5 g/m3. Determine the movement of mass per unit of time.

Solution. Given,
⍴= 1.5 g/m3
V = 20 m/s
A = 0.5 m2

m = ⍴VA
m = 20 x 1.5 x 0.5

∴ m = 15 g/s


How do you calculate mass flow rate?

It can be calculated by formula:
m = ⍴VA
⍴ – Density of fluid
V -> Velocity of liquid
A -> Area of cross section

What are mass flow rate and volumetric flow rate?

Mass flow rate is the mass of a liquid passing through an area of cross-section per unit of time. Volumetric flow rate is the volume of the liquid passing through per unit of time.

NOTE : Want to know more in Fluid Mechanics? Click here.

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