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Fig
9.2 A Control Mass System or Closed System
Control Volume System (Open System)
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Its a system of fixed volume.
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This type of system is usually referred to as "open system” or a "control volume"
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Mass transfer can take place across a control volume.
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Energy transfer may also occur into or out of the system.
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A control volume can be seen as a fixed region across which mass and energy transfers are studied.
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Control Surface- Its the boundary of a control volume across which the transfer of both mass and energy takes place.
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The mass of a control volume (open system) may or may not be fixed.
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When the net influx of mass across the control surface equals zero
then the mass of the system is fixed and vice-versa.
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The identity of mass in a control volume always changes unlike the case for a control mass system (closed system).
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Most of the engineering devices, in general, represent an open system or control volume.
Example:-
- Heat exchanger - Fluid
enters and leaves the system continuously with the transfer
of heat across the system boundary.
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Pump - A continuous flow of fluid takes
place through the system with a transfer of mechanical
energy from the surroundings to the system.
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Fig
9.3 A Control Volume System or Open System
Isolated System
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Its a system
of fixed mass
with same identity and fixed energy.
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No interaction of mass or energy takes place between the system and the surroundings.
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In more informal words an isolated system is like a closed shop amidst a busy market.
Fig 9.4 An Isolated System
