Classify the system you are anlyzing and select a branch.
Closed
System
Daemons
If there is no mass transfer across the boundary, the system is closed.
Problems involving a closed system - a block of solid, steam in a closed
container, a gas trapped in a piston-cylinder device, a heat engine, or
a refrigerator may involve a transfer of heat and work, but no mass,
between the system and its surroundings.
You inspect only the boundary of the control volume to detect the presence
or absence of mass transfer. There may be mass flow among different components
of a refrigerator, but this internal mass transfer in no way affects the
conclusion that the refrigerator, in its entirety, is a closed system with
only heat and work transfer with the surroundings.
Open
System
Daemons
A system with mass transfer, in addition to possible work and heat
transfers, across its boundary is an open
system. Pumps, compressors, diffusers, turbines, pipes, and nozzles are
examples of open systems.
A General System and Its Governing Balance Equations
