Question: A 125 MW power plant operates on a modified Rankine cycle with water a

Question

Question:

A 125 MW power plant operates on a modified Rankine cycle with water as the working fluid. Superheated steam enters the turbine (State 3) at a pressure of 15 MPa and a temperature of 650 degree C. Subcooled water leaves the condenser (State 1) at a pressure of 30 kPa and a temperature of 60 degree C. The turbine is adiabatic but not reversible and has an isentropic efficiency of 88 %, The pump is adiabatic and internally reversible, The heat transfer in both the condenser and the boiler take place at constant pressure. Complete the table below. Sketch the cycle on a T-s diagram. Use a dashed line to show isentropic processes and a solid line to show actual processes. Label all points and processes. Find: The net work output of the cycle, in kJ/kg. The percent error in the net work if the work of the pump is neglected, The mass flow rate of the water, in kg/hr and The thermal efficiency of the cycle.

Explanation / Answer

state1

v1=0.001022m^3/kg

h1=289.3kj/kg

s1=.944kj/kg-k

state2

v2=0.001658

h2=1610.9

s2=3.689

state3

v3=0.026735

h=3707.6

s=6.815

state4

v4=5.2293

h4=2625.4

s4=7.769

STEP;

a)net work output=(h3-h4)-(h2-h1)

b)%error=(h3-h4)/((h3-h4(-(h2-h1))*100

c)mass flow rate=125000/(net work output)

effeciency=net work output/(h3-h2)

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