1
Thermodynamics
Assume that the steam leaving the boiler is
at 3MPa and 400 deg C.
The condenser
operates at a pressure of 75kPa.
The
Turbine is required to provide an output to
operate a 300 MW electric generator set with
an efficiency of 95%.
The boiler burner has
an efficiency of 85% and burns natural gas
with a heating value of 100,000 btu/therm.
Assuming that the change in enthalpy across the pump is negligible and that the
expansion across the turbine is isentropic along with other ideal Rankine cycle
assumptions, estimate the consumption of gas to run this Rankine cycle in
therms per hour.
If cooling water is provided to the condenser at 85 deg F and
leaves at 95 deg F, estimate the cooling water flow rate required in gallons/
minute.
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Thermodynamics
The equations we need are as follows:
Q
in
= mass flow rate motive fluid * (h
3
– h
2
)
Q
in
(btu/h)/(0.85* 100,000 btu/therm) = therms of gas consumed per hour.
But to solve this we need the mass flow rate of motive fluid…we need some
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 Summer '08
 Sherif
 Fluid Dynamics, Thermodynamics, Mass flow rate, Rankine, Qout

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