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APPLIED ENGINEERING THERMODYNAMICS
MAE 115
1. Beef stew is being cooked in a pan that is (a) uncovered, (b) covered with a light lid, and (c) covered with a heavy lid. For which case will the cooking time be the shortest? Why?
2. Ice can be made by evacuating the air in a water tank. Explain why this happens and how this process can be made more efficient
3. CO2 enters a pipe at 3 MPa and 500 K at a rate of 2 kg/s. CO2 is cooled at a constant pressure as it flows in the pipe and the temperature of CO2 drops to 450K at the exit. Determine the volume flow rate and density of the CO2 using (a) ideal gas equation, and (b) the generalized compressibility chart. Also, determine (c) the error involved in the first case.
4. A fixed mass of an ideal gas is heated from 50 to 80oC at constant volume of (a) 1 m3 , and (b) 3 m3 . Which case will require more energy and why?
5. A piston-cylinder device contains argon gas at 200 kPa and 100oC. The gas is expanded isothermally to 50 kPa. During the process, 1500 kJ of heat is transferred to the system. Determine the mass of this system and the amount of work produced.
6. Air is contained in a piston-cylinder device at 600 kPa and 927oC, and occupies a volume of 0.8 m3 . The air undergoes an isothermal process until the pressure is reduced to 300 kPa. The piston is now fixed in place and not allowed to move while a heat transfer process takes place until the air reaches 27oC.
a. Sketch the system showing the energies crossing the boundary and the P- v diagram for the combined processes.
b. For the combined processes, determine the net amount of heat transfer, in kJ, and the direction.
7. An adiabatic gas turbine expands air at 1300 kPa and 500oC to 100 kPa and 127oC. Air enters the turbine through a 0.2 m2 opening with an average velocity of 40 m/s, and exhausts through a 1 m2 opening. Determine:
a. The mass flow rate of air through the turbine
b. The power produced by the turbine
8. Air is compressed in an isentropic compressor from 15 psia and 70oF to 200 psia. Determine the outlet temperature and work per unit mass of air.
9. A piston-cylinder device is containing 1 kg of steam at 500oC and 2 MPa. The piston device is surrounded by a water vapor mixture with a quality of X=0.6 at 100oC. If the piston is allowed to expand:
a. What is the maximum amount of heat that can be transferred between the piston-cylinder device and the surrounding?
b. What is the minimum amount of heat that can be transferred between the piston-cylinder device and the surrounding?