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Unformatted text preview: MAEZSI Test 2 Spring 2011
Closed book — time: 55 min — grading: 10+10 1. Air (ideal gas, cp = 1 kJ/kg.K and R = .287 kJ/kg.K) enters a 2stage compressor
with intercooling. At the entrance of the lower stage (point 1), the air is at 20°C
and 100 kPa. Both stages have an isentropic efﬁciency of 80%. At the exit from
the ﬁrst stage (point 2), the air at 300 kPa is cooled back to 20°C at point 3. The
second stage brings the air to 1000 kPa at point 4. Show and label the processes
on a T—s diagram. Per unit mass ﬂow rate, calculate the heat exchange, the
compression power, and the entropy production rate in the compressor. 2. An ideal steam turbine is equipped \
with a bypass valve, as shown on the
diagram. The incoming steam is at “W
pressure p1 and temperature T]; the l
mixing of 2 and 3 is at constant /
pressure p4, and T4 is also given; /T
neglect kinetic and potential \\
energies, and stray heat transfers.
Select the best thermodynamic diagram for this situation (explain 5 \ ML 1 brieﬂy) and label it to show the various processes. For a unit mass ﬂow rate at point I, calculate the V Lf
turbine power and the mass ﬂow rate through the valve. Conversion factors:
1 bar = 100 kPa 1 Btu = 778 lbfft 1 psi = 1 lbf/inz gc = 32.2 lbmft/lbfsz K=°C+273 OR =°F+460 £9 4 300tpa —“9 “'"5 L000 bPa ——§
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This note was uploaded on 04/02/2012 for the course ECS 222 taught by Professor Staff during the Fall '08 term at Syracuse.
 Fall '08
 Staff

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