1. A Diesel cycle operates with a compression ratio of 15, and a cutoff ratio of
ID: 1858887 • Letter: 1
Question
1. A Diesel cycle operates with a compression ratio of 15, and a cutoff ratio of 2.5. What is the rate of heat input required for this cycle to produce 223.8 kJ/s? (for air use: k=1.4)
a) 227 kJ/s
b) 386 kJ/s
c) 438 kJ/s
d) 556 kJ/s
2. A gas turbine utilizes two stages of compression, two stages of expansion, intercooling, reheating, and regeneration. What is the thermal efficiency of this gas turbine using the following data: T2 = 446 K and T7 = 808 K, T3 = T1 = 300 K, T10 = T4 = T2 = 446 K, T5 = T7 = T9 = 808 K, and T6 = T8 = 1200 K.
a) 0.22
b) 0.41
c) 0.63
d) 0.72
3. The enthalpies around an ideal Rankine cycle with an open-feedwater-heater are: h1 = 340.5 kJ/kg, h2 = 340.6 kJ/kg, h3 = 444.3 kJ/kg, h4 = 447.2 kJ/kg, h5 = 3115.3 kJ/kg, h6 = 2479.9 kJ/kg, and h7 = 2344.1 kJ/kg. What percentage of the mass flow rate passing through the boiler is bled from the turbine for open-feedwater-heater?
a) 4.85 %
b) 7.31 %
c) 10.6 %
d) 13.2 %
4. The enthalpies at various states in an ideal Rankine cycle with an open-feedwater-heater are: h1 = 340.5 kJ/kg, h2 = 340.6 kJ/kg, h3 = 444.3 kJ/kg, h4 = 447.2 kJ/kg, h5 = 3115.3 kJ/kg, h6 = 2479.9 kJ/kg, and h7 = 2344.1 kJ/kg. What is the thermal efficiency of this cycle?
a) 24.6 %
b) 28.6 %
c) 32.6 %
d) 36.6 %
5. The enthalpies at various states in a simple vapor-compression refrigerator cycle are:
h1 = 237.14 kJ/kg, h2 = 283.10 kJ/kg, and h3 = h4 = 115.76 kJ/kg. What is the coefficient of performance of this device
a) 2.64
b) 2.93
c) 3.26
d) 3.69
6. An ideal R-134a, dual compressor vapor-compression refrigerator system uses a flash chamber to separate the vapor in the evaporator feed line. The enthalpies of refrigerant at various states are: , h1 = 235.31 kJ/kg, h5 = h6 = 125.26 kJ/kg, h3 = 252.32 kJ/kg, and h7 = h8 = 62.00 kJ/kg. What fraction of the mass flow rate passing through the evaporator.
a) 0.8
b) 1.0
c) 1.2
d) 1.5
7. At one location in a nozzle, the air enthalpy is 401 kJ/kg and the air velocity is 400 m/s. What is the stagnation enthalpy (based on temperature dependent specific heats) of the air at this location?
a) 300 kJ/kg
b) 357 kJ/kg
c) 470 kJ/kg
d) 481 kJ/kg
8. At one location in a nozzle, the air temperature is 400 K and the air velocity is 450 m/s. What is the Mach number at this location? (for air: k=1.4 and R=287 J/kg K)
a) 0.97
b) 1.12
c) 1.37
d) 2.02
Explanation / Answer
1)b 5) a 7)d 8)b
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