Volumetric Flow Rate


The flow of oil through a pipeline can use the volumetric flow rate to satisfy the conservation of energy because the density of the oil is constant.

By Maher A. A. Abdussalam (Own work) [Public domain], via Wikimedia Commons

The conservation of mass equation can be simplified if the fluid is incompressible and the control volume size is fixed.

First, if the density of the fluid is constant (doesn’t change with time or position) the density term can be brought outside of the integrals and the Conservation of Mass equation can be written as


Cancelling the density results in the equation



Second, if in addition to the density being constant, the control volume size is constant, then the Conservation of Mass Equation becomes



This equation states that the net volumetric flow rate is equal to zero.


Learning Objectives:

Definition of volumetric flow rate, assumptions associated with volumetric flow rate, how to apply the conservation of mass and volumetric flow rate.