MECE E3301 Thermodynamics: Homework 4
Problem 1: Ideal gas is confined to a volume of Vi within a piston-cylinder assembly
at a pressure of pi
. The piston-cylinder assembly is well-insulated. The gas is allowed to
expand to a volume Vf in two ways: (1) reversibly, and (2) suddenly and irreversiibly. The
pressure at the final state in both cases is larger than the pressure in the surroundings,
p0. Answer the following questions:
1. Find the work done in the reversible process
2. Find the work done in the irreversible/sudden process
3. Find the pressure at the final state in the two processes described here.
4. Show that the pressure at the end of the reversible process is always less than the
pressure at the end of the irreversible process.
Problem 2: Hot combustion gases, modeled as air behaving as an ideal gas, enter a
turbine at 10 bar, 1500 K and exit at 1.97 bar and 900 K. The mass flow rate is 0.1 kg/s.
If the power output of the turbine is 55.4 kW, determine the rate of heat transfer from the
turbine to its surroundings, in kW. You’ll have to use the first law of thermodynamics for
control volumes. Of course, you’ll have to define/choose an appropriate control volume.
This is problem 4.36 from M & S, 9th ed. The mass flow rate is not given in the problem
(an omission).
Problem 3 You’ll have to apply the conservation of mass for a control volume. As
in the previous problem, you’ll have to define/choose an appropriate control volume.
Problem 4 You’ll have to use the first law of thermodynamics for control volumes.
As in the previous problem, you’ll have to define/choose an appropriate control volume.