Chapter 3 | 161it flows in the pipe so that the temperature of CO 2 drops to
450 K at the exit of the pipe, determine (b) the volume flow
rate at the exit of the pipe.
3–111 A piston–cylinder device initially contains 0.2 kg of
steam at 200 kPa and 300°C. Now, the steam is cooled at
constant pressure until it is at 150°C. Determine the volume
change of the cylinder during this process using the com-
pressibility factor and compare the result to the actual value.
(b) On the T-vdiagram sketch the constant specific vol-
ume process through the state T120°C,v0.7163 m^3 /kg
from P 1 100 kPa to P 2 300 kPa. For this data set place
the temperature values at states 1 and 2 on its axis. Place the
value of the specific volume on its axis.
3–114 The gage pressure of an automobile tire is measured
to be 200 kPa before a trip and 220 kPa after the trip at a
location where the atmospheric pressure is 90 kPa. Assuming
the volume of the tire remains constant at 0.035 m^3 , deter-
mine the percent increase in the absolute temperature of the
air in the tire.
3–115 Although balloons have been around since 1783 when
the first balloon took to the skies in France, a real breakthrough
in ballooning occurred in 1960 with the design of the modern
hot-air balloon fueled by inexpensive propane and constructed
of lightweight nylon fabric. Over the years, ballooning has
become a sport and a hobby for many people around the world.
Unlike balloons filled with the light helium gas, hot-air balloons
are open to the atmosphere. Therefore, the pressure in the bal-
loon is always the same as the local atmospheric pressure, and
the balloon is never in danger of exploding.
Hot-air balloons range from about 15 to 25 m in diameter.
The air in the balloon cavity is heated by a propane burner
located at the top of the passenger cage. The flames from the
burner that shoot into the balloon heat the air in the balloon
cavity, raising the air temperature at the top of the balloon
from 65°C to over 120°C. The air temperature is maintained
at the desired levels by periodically firing the propane burner.3–112 Combustion in a diesel engine may be modeled as a
constant-pressure heat addition process with air in the cylinder
before and after combustion. Consider a diesel engine with
cylinder conditions of 950 K and 75 cm^3 before combustion,
and 150 cm^3 after it. The engine operates with an air–fuel ratio
of 22 kg air/kg fuel (the mass of the air divided by the mass of
the fuel). Determine the temperature after the combustion
process.
Steam
0.2 kg
200 kPa
300 °CQFIGURE P3–111Combustion
chamber
950 K
75 cm^3FIGURE P3–112FIGURE P3–115
© Vol. 1/PhotoDiscChapter 3 | 1613–113 On the property diagrams indicated below, sketch
(not to scale) with respect to the saturated liquid and satu-
rated vapor lines and label the following processes and states
for steam. Use arrows to indicate the direction of the process,
and label the initial and final states:
(a) On the P-vdiagram sketch the constant temperature
process through the state P300 kPa,v0.525 m^3 /kg as
pressure changes from P 1 200 kPa to P 2 400 kPa.
Place the value of the temperature on the process curve on the
P-vdiagram.