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Unformatted text preview: ME 3322C FINAL EXAMINATION
May 5, 2005
3 Hours You may bring into the exam two 8—1/2 x 11 sheets of paper and a calculator. Show all
your work. Write clearly and box your answers. Start each problem on a new sheet of
paper. Put your name on every sheet you turn in. You are responsible for presenting
your work so that it is readily understood. Do not interpolate. Name (print) On my honor, I pledge that I have neither given nor received inappropriate aid in
this examination. Signature Problem 1 [68 pts] an condenser wP QM A steam power plant operates with a Rankine cycle. All the components are internally reversible except the turbine. The boiler pressure is p1 = 6 MPa and its exit temperature is
= 600°C. The boiler receives heat from a source with a boundary temperature of Tb = 700°C. The turbine exit quality is x; : 97% and the condenser temperature is T2 = 45°C. i.
ii.
iii. iv. vi. vii. viii. ix. xi. Draw the Ts diagram for this cycle [6 pts] Find the turbine work per unit mass, Wt / m. [6 pts]
Find the isentropic efficiency of the turbine, m. [6 pts] Find the pump work per unit mass, Wp / m. [6 pts]
Find the heat transfer to the ﬂuid per unit mass in the boiler, Qin/ m. [6 pts] Find the heat transfer out per unit mass in the condenser, Q / m. [6 pts] 0 m Find the thermal efﬁciency of the cycle, 11. [6 pts] Find the entropy generation per unit mass in the boiler, Oh 1’ m . [6 pts] I I Find the entropy generation per unit mass in the turbine, c5t / m. [6 pts] Write down an exergy balance equation for the turbine and do a complete
exergy accounting for the turbine. Assume the temperature and pressure of the exergy environment is To : 25°C, p0 = 1 bar. Treat e—ﬂ —Ef2 as the exerg input (per unit mass) to the control volume, and show that the exergy outputs
= the exergy input. [8 pts] Find the exergetic efﬁciency of the turbine, at. [6 pts] Problem 2 [32 pts] heat addition 2 3
T
corn ression expa sion
1 4 heat removal S A piston engine operates with an ideal airstandard Carnot cycle. The Carnot cycle is
similar to the Otto cycle, except the heat addition and removal processes occur at constant temperature instead of at constant volume (see pv and T—s diagrams, above). At the beginning of the compression stroke, p1 = 100 kPa and T1 = 280 K. The compression ratio is r = V1/V2 = 9. The heat addition per unit mass is Q23/m = 1200
kJ/kg. i. Find the pressure and temperature at the end of the compression stroke, 132 and
T2. [6 [3125] ii. Find the efﬁciency of the cycle, 11. [6 pts} iii. Find the net work per unit mass, chcle/m. [6 pts] iv. Find the work per unit mass during the heat addition process 23, W23/m.
[6 m] V. Find the entropy production per unit mass during process 2—3, 023/111. Assume heat is transferred across the cylinder wall from a source with a boundary
temperature Tb = 700 K, and the cylinder wall is part of the system. (Note: for
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