University of Babylon /College Of Engineering
Electrochemical Engineering Dept.
Second Stage /Thermodynamics
Applications of Thermodynamics to Flow Processes
The thermodynamics of flow is based on mass, energy, and entropy balances,
TURBINES (EXPANDERS)
The expansion of a gas in a nozzle to produce a high-velocity stream is a process
that converts internal energy into kinetic energy. This kinetic energy is in turn
converted into shaft work when the stream impinges on blades attached to a
rotating shaft
Steady-state flow through a turbine or expander
The shaft work I W,(isentropic)I is the maximum that can be obtained from
an adiabatic turbine with given inlet conditions and given discharge pressure.
Actual turbines produce less work, because the actual expansion process is
irreversible. We therefore define a turbine efficiency as:
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University of Babylon /College Of Engineering
Electrochemical Engineering Dept.
Second Stage /Thermodynamics
Adiabatic expansion process in a turbine or expander
Compressors
The compression of gases may be accomplished in equipment with rotating blades
(like a turbine operating in reverse) or in cylinders with reciprocating pistons.
Rotary equipment is used for high-volume flow where the discharge pressure is not
too high. For high pressures, reciprocating compressors are required. The energy
equations are independent of the type of equipment; indeed, they are the same as
for turbines or expanders, because here too potential- and kinetic-energy changes
are presumed negligible.
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University of Babylon /College Of Engineering
Electrochemical Engineering Dept.
Second Stage /Thermodynamics
Steady-state compression process
Compressor efficiencies are usually in the range of 0.7 to 0.8
.
Adiabatic compression process
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