Mass Balances: Systems with Multiple Inlets and Outlets

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 or Rate 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
Mass flow rate out of the system, m dot out.
Mass flow rate out of the system, m dot out.
Mass flow rate out of the system, m dot out.
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.
Often there are multiple inlets and outlets in an open system. A

mass balance

on a multi-inlet and/or multi-outlet process must account for all mass flows into and out of the system.
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Ch 5, Lesson A, Page 3 - Mass Balances: Systems with Multiple Inlets and Outlets