MCEG 2301 – Thermodynamics I
Assignment 2
MCEG 2301 – Thermodynamics I
Assignment 2
Dr. Nishant Bhatta
Problems
Problem 1. A closed, rigid container of volume 0.5 m3 is placed on a hot plate. Initially, the container
holds a two-phase mixture of saturated liquid water and saturated water vapor at T1 =
100◦ C with a quality of x1 = 0.2. After heating, the temperature in the container is
T2 = 150◦ C.
Indicate the initial and final states on P –v and T –v diagrams, and determine:
(a) the pressure at each state,
(b) the mass of vapor present at each state, in kg,
(c) if heating is continued, the temperature at which the container holds only saturated
vapor.
Problem 2. A piston–cylinder device with a linear spring initially contains water at a pressure of
4 MPa and temperature of 500◦ C with an initial volume of 0.1 m3 , as shown in Fig. 1. If
the piston is at the bottom, the system pressure is 300 kPa. The system now cools until
the pressure reaches 1000 kPa.
Sketch the process on a P –v diagram and determine:
(a) the mass of water,
(b) the final temperature and volume,
(c) the total work transfer.
Figure 1
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MCEG 2301 – Thermodynamics I
Assignment 2
Problem 3. A piston–cylinder device shown in Fig. 2 contains 2 kg of water initially at a pressure of
500 kPa with a quality of 20%. The water is heated until it becomes saturated vapor. The
volume of the system when the piston is at the upper stops is 0.4 m3 .
Sketch the process on P –v and T –v diagrams and determine:
(a) the final pressure,
(b) the total work transfer.
Figure 2
Problem 4. Water of mass 2 kg is contained within a piston–cylinder arrangement as shown in Fig. 3.
The initial temperature is 105◦ C, and there are equal masses of liquid and vapor initially.
The system is heated to a position where the piston is locked, and then the system is
cooled to the saturated vapor state at T = 50◦ C.
Draw the process on a P –v diagram and evaluate the work done during the process.
Figure 3
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