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WorksheetsThermo FE Review
Total questions: 16
Worksheet time: 8mins
A closed rigid vessel contains 40% liquid water and 60% water vapor by volume. The liquid-vapor mixture is in equilibrium at 150 deg C. What is the quality of the mixture?
4.5 x 10^-3
0.40
0.60
0.996
A cylinder fitted with a frictionless piston contains an ideal gas at temperature T and pressure p. The gas expands isothermally and reversibly until the pressure is p/3. Which statement is true regarding the work done by the gas during expansion?
It is equal to the change in enthalpy of the gas.
It is equal to the change in internal energy of the gas.
It is equal to the heat absorbed by the gas.
It is greater than the heat absorbed by the gas.
An ideal heat engine is constructed by cycling 1 kg of oxygen gas (O2), initially at 1 atm and 25 deg C, through a sequence of four processes. The sequence consists of isothermal expansion to 2.35 m^3, followed by adiabatic expansion to 8.21 m^3, followed by isothermal compression to 2.67 m^3, and finally, adiabatic compression back to the initial state. All steps are reversible. For oxygen, the specific heat at constant pressure (cp) is 0.918 kJ/kg*K, and the specific heat at constant volume (cv) is 0.658 kJ/kg*K. What is the thermal efficiency of this heat engine?
20%
40%
53%
61%
Moist atmospheric air with a dry-bulb temperature of 30 deg C and a relative humidity of 40% is cooled under constant pressure until condensation of the water vapor is observed. What is the final temperature of the air?
10 deg C
16 deg C
20 deg C
30 deg C
How much energy per unit mass of dry air is released during the cooling process described in the previous problem?
0 kJ/kg
16 kJ/kg
63 kJ/kg
100 kJ/kg
A small gas turbine burns liquid octane (C8 H18) with 300% excess air. How many moles of nitrogen gas (N2) in the combustion products are produced per mole of fuel consumed?
47 N2
94 N2
141 N2
188 N2
What is the specific enthalpy of HFC-134a at 0.4 MPa and 85% quality?
241 kJ/kg
261 kJ/kg
333 kJ/kg
375 kJ/kg
An ideal gas at a gage pressure of 0.3 MPa and 25 deg C is heated in a closed container to 75 deg C. What is the final pressure?
0.35 MPa
0.47 MPa
0.90 MPa
1.20 MPa
All real gases deviate to some extent from the ideal behavior described by the equation pV = mRT. For which of the following conditions are the deviations smallest?
high temperatures and low volumes
high temperatures and low pressures
high pressures and low volumes
high pressures and low temperatures
Which thermodynamic property is the best measure of the molecular activity of a substance?
enthalpy
internal energy
entropy
external energy
What is the maximum thermal efficiency possible for a power cycle operating between 600 deg C and 110 deg C?
47%
56%
63%
74%
An ideal Rankine cycle consists of which of the following?
two constant volume and two isentropic processes
two constant pressure and two isentropic processes
two constant volume and two constant temperature processes
two constant pressure and two constant temperature processes
An inventor claims that an engine produces 130 kW with a fuel consumption of 20 kg/h. The fuel has a chemical energy of 40,000 kJ/kg. The energy is received at a mean temperature of 500 deg C and is rejected at a mean temperature of 50 deg C. Which laws of thermodynamics, if any, are violated?
first law only
second law only
both first and second laws
neither first nor second laws
Which cycle do most steam turbine power generating plants operate on?
Brayton
Otto
Rankine
Ericsson
Atmospheric air at 21 deg C has a relative humidity of 50%. What is the dew point temperature?
7 deg C
10 deg C
17 deg C
24 deg C
2 m^3 of an ideal gas are compressed from 100 kPa to 200 kPa. As a result of the process, the internal energy of the gas increases by 10 kJ, and 140 kJ of heat is transferred to the surroundings. How much work was done by the gas during the process?
-150 kJ
-130 kJ
-85 kJ
-45 kJ
