**Cengel & Boles -- Chapter 3
questions**

Use CyclePad to explain/justify your answers. Please save all your files with your 3 letter initials followed by the problem number (e.g. JLB389).

**3-89C Is the energy required to heat
air from 295 to 305 K the same as the energy required to heat it
from 345 to 355K? Assume the pressure remains constant in both
cases. **

Create a system in CP to justify your answer.

**3-91C A fixed mass of an ideal gas is
heated from 50 to 80 C at a constant pressure of (a) 1 atm and
(b) 3 atm. **

For which case do you think the energy required will be greater?

Why?

Create a system in CP to justify your answer.

**3-93C A fixed mass of an ideal gas is
hated from 50 to 80 C (a) at a constant volume and (b) at a
constant pressure. **

For which case do you think the energy required will be greater?

Why?

Create a system in CP to justify your answer.

**3-97C Is it possible to compress an
ideal gas isothermally in an adiabatic piston-cylinder device? **

Explain.

Create a system in CP to justify your answer.

**3-35 A mass of 5kg of saturated water
vapor at 200 kPa is heated at constant pressure until the
temperature reaches 300 C. **

Calculate the work done by the steam during this process.

**3-37 A frictionless piston-cylinder
device contains 8 kg of superheated water vapor at 500 kPa and
300 C. Steam is now cooled at constant pressure until 70 percent
of it, by mass, condenses. **

Determine the work done during this process.

**3-38 A mass of 1.2kg of air at 150 kPa
and 12 C is contained in a gas-tight, frictionless
piston-cylinder device. The air is now compressed to a final
pressure of 600 kPa. During the process heat is transferred from
the air such that the temperature inside the cylinder remains
constant. **

Calculate the work done during this process.

**3-48 A piston-cylinder device with a
set of stops contains 10 kg of refrigerant-12. Initially, 8 kg of
refrigerant is in the liquid form, and the temperature is -10 C.
Now heat is transferred slowly to the refrigerant until the
piston hits the stops, at which point the volume is 400 L. **

Determine (a) the temperature when the piston first hits the stops and (b) the work done during this process. Also show the process on a P-V diagram.

**3-73 The radiator of a steam heating
system has a volume of 20 L and is filled with superheated vapor
at 300 kPa and 250 C. At this moment both the inlet and exit
valves to the radiator are closed. **

Determine the amount of heat that will be transferred to the room when the steam pressure drops to 100 kPa. Also show the process on a P-v diagram with respect to saturation lines.

**3-78 A piston-cylinder device contains
5kg of refrigerant-12 at 800 kPa and 60 C. The refrigerant is now
cooled at constant pressure until it exists as a liquid at 20 C.**

Determine the amount of heat transfer, and show the process on a T-v diagram with respect to saturation lines.