1. No category

Thermodynamics // Homework #3
mass of the steam, (b) the final temperature, and (c) the amount
Closed System Energy Analysis
1.
3
A 0.5-m rigid tank contains refrigerant-134a initially at 160 kPa
and 40 percent quality. Heat is now transferred to the refrigerant
2.
refrigerant in the tank and (b) the amount of heat transferred.
touching the piston but exerts no force on it. Heat is now slowly
Also, show the process on a P-v diagram with respect to
transferred to the steam, causing the pressure and the volume to
saturation lines.{10.03 kg, 2707 kJ}
rise
3
to
500
kPa
and
0.6
m3,
A 20-ft rigid tank initially contains saturated refrigerant- 134a
respectively. Show the process on a
vapor at 160 psia. As a result of heat transfer from the
P-v diagram with respect to saturation
refrigerant, the pressure drops to 50 psia. Show the process on a
lines and determine (a) the final
P-v diagram with respect to saturation lines, and determine (a)
temperature, (b) the work done by the
the final temperature, (b) the amount of refrigerant that has
steam,
condensed, and (c) the heat transfer {40.23ºF, 47.75 lbm, 4169
transferred. {1132ºC, 35 kJ, 808 kJ}
9.
and
(c)
the
total
heat
A piston–cylinder device initially contains 0.8 m3 of saturated
A well-insulated rigid tank contains 5 kg of a saturated liquid–
water vapor at 250 kPa. At this state, the piston is resting on a
vapor mixture of water at l00 kPa. Initially, three-quarters of the
set of stops, and the mass of the piston is such that a pressure of
mass is in the liquid phase. An electric resistor placed in the tank
300 kPa is required to move it. Heat is now slowly transferred to
is connected to a 110-V source, and a current of 8 A flows
the steam until the volume doubles. Show the process on a P-v
through the resistor when the switch is turned on. Determine
diagram with respect to saturation lines and determine (a) the
how long it will take to vaporize all the
final temperature, (b) the work done during this process, and (c)
liquid in the tank. Also, show the process
the total heat transfer. {662ºC, 240 kJ, 1213 kJ}
10. Two tanks (Tank A and Tank B) are separated by a partition.
saturation lines. {153.1 min}
Initially Tank A contains 2-kg steam at 1 MPa and 300°C while
An insulated tank is divided into two
Tank B contains 3-kg saturated liquid–vapor mixture with a
parts by a partition. One part of the tank contains 2.5 kg of
vapor mass fraction of 50 percent. Now the partition is removed
compressed liquid water at 60°C and 600 kPa while the other
and the two sides are allowed to mix until the mechanical and
part is evacuated. The partition is now removed, and the water
thermal equilibrium are established. If the pressure at the final
expands to fill the entire tank. Determine the final temperature
state is 300 kPa, determine (a) the temperature and quality of the
of the water and the volume of the tank for a final pressure of 10
steam (if mixture) at the final state and (b) the amount of heat
3
kPa. {45.81ºC, 0.972 m }
5.
A piston–cylinder device initially contains steam at 200 kPa,
200°C, and 0.5 m3. At this state, a linear spring (F  x) is
on a T-v diagram with respect to
4.
8.
until the pressure reaches 700 kPa. Determine (a) the mass of the
Btu}
3.
of heat transfer. {7.565 kg, 179.9 ºC, 4495 kJ}
lost from the tanks. {133.5 ºC, 0.3641, 3959 kJ}
A piston–cylinder device contains 5 kg of refrigerant- 134a at
800 kPa and 70°C. The refrigerant is now cooled at constant
pressure until it exists as a liquid at 15°C. Determine the amount
of heat loss and show the process on a T-v diagram with respect
to saturation lines. {1173 kJ}
6.
A piston–cylinder device contains 0.5 lbm of water initially at
120 psia and 2 ft3. Now 200 Btu of heat is transferred to the
water while its pressure is held constant. Determine the final
temperature of the water. Also, show the process on a T-v
diagram with respect to saturation lines. {1161.4 ºF}
7.
A piston–cylinder device contains steam initially at 1 MPa,
450°C, and 2.5 m3. Steam is allowed to cool at constant
pressure until it first starts condensing. Show the process on a Tv diagram with respect to saturation lines and determine (a) the
Closed System Energy Analysis (Ideal Gas)
11. A rigid tank contains 20 lbm of air at 50 psia and 80°F. The air
is now heated until its pressure doubles. Determine (a) the
volume of the tank and (b) the amount of heat transfer. { 80 ft3,
1898 Btu}
12. A 3-m3 rigid tank contains hydrogen at 250 kPa and 550 K. The
gas is now cooled until its temperature drops to 350 K.
Determine (a) the final pressure in the tank and (b) the amount
of heat transfer. {159.1 kPa, 686.2 kJ}
13. A piston–cylinder device contains 25 ft3 of nitrogen at 40 psia
and 700°F. Nitrogen is now allowed to cool at constant pressure
until the temperature drops to 200°F. Using specific heats at the
average temperature, determine the amount of heat loss. {284.2
Btu}
14. A piston–cylinder device contains 0.8 kg of nitrogen initially at
100 kPa and 27°C. The nitrogen is now compressed slowly in a
polytropic process during which PV1.3=constant until the volume
is reduced by one-half. Determine the work done and the heat
transfer for this process. {54.8 kJ, 13.6 kJ}
15. A piston–cylinder device, whose piston is resting on a set of
stops, initially contains 3 kg of air at 200 kPa and 27°C. The
mass of the piston is such that a pressure of 400 kPa is required
to move it. Heat is now transferred to the air until its volume
doubles. Determine the work done by the air and the total heat
transferred to the air during this process. Also show the process
on a P-v diagram. {516 kJ, 2674 kJ}