Mass Balance for Open Systems

Change in the Total
Mass of the System
=
Total Mass of the
System at Final State
-
Total Mass of the
System at Initial State
Differential Mass Balance :
Equation.
Equation.
Change in the Total
Mass of the System
Total Mass
Leaving the System
Total Mass
Entering the System
=
-
Integral Mass Balance :
mass flow rate into the system, m dot in.
Mass flow rate out of the system, m dot out.
Open
System
This diagram shows an open system with a system boundary and one inlet pipe for mass to enter the system and one outlet pipe for mass to leave the system.

Conservation of Mass Principle (or Mass Balance)


Mass cannot be created or destroyed. Therefore, as we did for energy, we must account for all mass flows that cross the system boundary.
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Ch 5, Lesson A, Page 2 - Mass Balance for Open Systems