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Modern Engineering Thermodynamics

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458 CHAPTER 13: Vapor and Gas Power Cycles<br />

Process 1−2 is the nonadiabatic<br />

cylinder power stroke<br />

Process 1−2s is the reversible and<br />

adiabatic cylinder power stroke<br />

1<br />

Saturation<br />

dome<br />

1<br />

Saturation<br />

dome<br />

T<br />

4<br />

2,3,4s<br />

s<br />

(a) The Newcomen cycle<br />

Condensation inside<br />

the piston−cylinder<br />

producing piston<br />

movement and work<br />

T<br />

4<br />

Work-producing<br />

piston stroke<br />

3,4s 2s<br />

Condensation in an<br />

external condenser<br />

s<br />

(b) The reversible Rankine cycle<br />

T<br />

Carnot<br />

cycle<br />

4<br />

1<br />

Line of constant<br />

boiler pressure<br />

Saturation<br />

dome<br />

Rankine cycle<br />

3,4s<br />

2s<br />

s<br />

(c) Comparison of the reversible<br />

rankine and Carnot cycles<br />

FIGURE 13.8<br />

The Newcomen, Rankine, and Carnot cycles.<br />

Q B<br />

4<br />

Boiler<br />

1<br />

W P<br />

Pump<br />

Adiabatic<br />

engine<br />

W E<br />

Condenser<br />

3<br />

Q C<br />

2<br />

T<br />

4<br />

p = Constant<br />

isobar<br />

s<br />

1<br />

3,4s 2s 2<br />

h<br />

Critical<br />

point<br />

4s 4 1<br />

3<br />

s<br />

2s<br />

2<br />

p<br />

4,4s 1<br />

T = Constant<br />

isotherm<br />

3 2,2s<br />

v<br />

FIGURE 13.9<br />

Reciprocating heat engines operating on Newcomen and Rankine cycles.<br />

Consider the Rankine cycle shown in Figure 13.9. An energy rate balance on the steady state boiler, the condensate<br />

pump, and the piston-cylinder prime mover (neglecting any changes in flow stream kinetic or potential<br />

energy) gives<br />

Heat transport rate into the boiler = _Q B = _mðh 1 − h 4 Þ<br />

The magnitude of the power into the condensate pump = j _W pump j = _m ðh 4 − h 3 Þ<br />

Power out of the piston-cylinder prime mover = _W pm = _m ðh 1 − h 2 Þ+ _Q pm

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