Unformatted text preview: 5—7 Air enters a nozzle steadily at 2.21 kg/m3 and 40 m/s
and leaves at 0.762 kg/m3 and 180 m/s. If the inlet area of the
nozzle is 90 cm2, determine (a) the mass flow rate through
the nozzle, and (b) the exit area of the nozzle. Answers: (a)
0.796 kg/s, (b) 58 cm2 5—34 Steam enters a nozzle at 400°C 'and 800 kPa W
velocity of 10 m/s, and leaves at 300°C and 200 kPa W II
losing heat at a rate of 25 kW. For an inlet area of 800
determine the velocity and the volume ﬂow rate of the st L"
at the nozzle exit. Answers: 606 m/s, 2.74 m3/s 400°C
800 kPa
10 m/s 300°C
200 kPa (2
FIGURE P5—34 5—48 Refrigerant134a enters a compressor at 180 kPa as
a saturated vapor with a ﬂow rate of 0.35 m3/min and
leaves at 700 kPa. The power supplied to the refrigerant
during compression process is 2.35 kW. What is the tem
perature of R134a at the exit of the compressor? Answer:
488°C 5—67 Saturated liquidvapor mixture of water, called wet
steam, in a steam line at 2000 kPa is throttled to 100 kPa and
120°C. What is the quality in the steam line? Answer: 0.957 Throttling valve  100 kPa
120°C FIGURE P567 5—76 A hotwater stream at 80°C enters a mixing chamber
with a mass ﬂow rate of 0.5 kg/s where it is mixed with a
stream of cold water at 20°C. If it is desired that the mixture
leave the chamber at 42°C, determine the mass ﬂow rate of
the coldwater stream. Assume all the streams are at a pres—
sure of 250 kPa. Answer: 0.865 kg/s FIGURE P5—76 5—84 A thinwalled doublepipe counterﬂow heat is used to cool oil (cp— — 2. 20 kJ/kg °C) from 150 to , .
rate of 2 kg/s by water (cp = 4.18 kJ/kg °C) that enters
at a rate of 1.5 kg/s. Determine the rate of heat tranSfe
heat exchanger and the exit temperature of water. Hot oil
2 kglsi150°C FIGURE P5—84 598 A llO—volt electrical heater 1s used to warm 0. 3:
of air at 100 kPa and 15°C to 100 kPa and 30°C. How
current in amperes must be supplied to this heater? An insulated 0.15m3 tank contains helium at 3 MPa
30°C. A valve is now opened, allowing some helium to
. The valve is closed when onehalf of the initial mass
'c’aped. Determine the ﬁnal temperature and pressure in tank Answers: 257 K, 956 kPa ...
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 Fall '08
 Errington

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