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Thermodynamics: Steady Flow Engineering Devices

Steady Flow Process

After a device has gone through its start up process it could enter a steady flow process. There are few definitions that can be used to describe a steady flow process. First, a steady flow process has the fluid flowing through the CV steadily. Since the fluid is flowing steadily, the mass flow value through the device would be constant. Next a steady flow process has no intensive or extensive properties that would change with time. This would mean that the specific volume, internal energy, etc would remain constant, and for these values to remain constant that would mean that the energy going into the device must equal the energy coming out of the device, refer to equation 1.

energy balance equation for steady flow devices (1)

enthalpy, potential energy, and kinetic energy effects on energy balance (2)

Finally, for a device to have a steady flow process the boundary work has to be zero. This doesn't mean that there can be other aspects that could require work, or produce work. For example a certain amount of work is required to turn the blades of a turbine, which is known as shaft work.

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