Question

**Calculate the entropy production** for the
piston-cylinder power producing cycle you analyzed in,
**problem 1**.

**Problem 1:** A piston cylinder device has a
volume of 0.04 m^{3} and initially contains air at 293 K
and 1 bar. This device is used to perform a cycle in which the gas
is heated at a constant volume until the temperature reaches 1000
K. The air is allowed to expand following an isothermal process
until the volume is 3.5 times the original volume. It is then
cooled at a constant volume process. The completion of the cycle is
a PV^{1.36} = constant process back to the original state.
For the air, the specific heat is c_{v} =0.79 kJ/(Kg K) =
constant and its gas constant is R_{G}=0.287 kJ/(Kg
K).

The calculations should include the heat transfer systems to the source and sink temperatures. Consider that all heat flows into the system come from a constant temperature source of 1800K and that all heat flows out of the system are to a constant temperature of 250 K. Will this cycle operate? Which process or heat sink temperature should be altered in order to improve the efficiency of the system or to make it work? In doing these calculations one should begin with the differential form of the entropy balance and determine how entropy production varies throughout the process.

**According to my calculations, Q12=26.56kJ,
Q34=-30.203kJ, Q23=17.102kJ, Q41=-4.033kJ.**

Please solve the **entropy production** for this
problem and answer the questions given above. Thank you!

Answer #1

5 kg of air in a piston cylinder assembly undergoes a Carnot
power cycle. Heat is received at temperature?1=727°C and rejected
at ?3=27°C.During the heat input process, the pressure changes from
?1=1200kPa to ?2=900kPa, respectively. Assume the air behaves as an
ideal gas with constant specific heats.
Determine:
a.pressures [kPa] at beginning and end of the isothermal heat
rejection process (?3,?4)
b.heat transfer from high temperature source [kJ]
c.thermal efficiency
d.net work output for cycle [kJ]

1) An ideal gas is contained in a
piston-cylinder device and undergoes a power cycle as follows:
1-2 isentropic compression from an initial
temperatureT1= 20 degree celsius with a compression ratio
r = 5
2-3 constant pressure heat addition 3-1 constant volume heat
rejection
The gas has constant specific heats with cv = 0.7
kJ/kg·K and R= 0.3 kJ/kg·K.
(a) Sketch the
P-v and T-s diagrams for the cycle.
(b) Determine the heat
and work interactions for each pro-cess, in...

A piston cylinder device contains air with a volume of 0.05 m3
at 25oC and 100 kPa pressure. The gas is now compressed to a final
temperature of 95oC at 250 kPa. This compression is polytropic and
follows PVn=constant.
a. Determine how much boundary work was added to the gas [in
kJ]
b. How much heat was added or removed from this system during
this process? [in kJ]

A 0.2 m3 piston-cylinder initially contains 400 K air. A heavy
frictionless piston maintains a pressure of 500 kPa abs. Then, a
weakness in the cylinder wall blows out and creates a hole. Air
escapes through the hole until the piston drops far enough to cover
the hole. At that point, the volume is half the initial volume.
During this process, 75 kJ of heat is transferred to the 100 kPa,
300 K surroundings. Using Cp = 1.005 kJ/kg-K and...

In a cylinder/piston arrangement, air is compressed in a
reversible polytropic process to a final state of 800 kPa, 500 K.
Initially air is at 110 kPa and 25oC. During the
compression process heat transfer takes place with the ambient
maintained at 25oC. Assume air as an ideal gas (R =0.287
kJ/kg) and has constant specific heats of Cp = 1.004
kJ/kgK and Cv = 0.717 kJ/kgK. If the mass of air in the
cylinder is 0.1286 kg, determine
a)...

A piston cylinder device contains a mixture of 0.2 kg of H2 and
1.6 kg of N2 at 100 kPa and 300K. Heat is now transferred to the
mixture at constant pressure unitl the volume is doubled. Assuming
constant specific heats at the average temperature (the constant
pressure specific heats of H2 and N2 are 14.501 kJ/kg°K and 1.049
kJ/kg°K, respectively), determine: a) the heat transfer. b) the
entropy change of the mixture.

A 0.2 m3 piston/cylinder contains air at 400 K and
400 kPa and receives heat from a constant temperature heat source
at 1300 K. The piston expands at constant pressure to a
volume of 0.6 m3. Determine the change of availability
of the system.

Air in a piston-cylinder device undergoes an isobaric expansion
process from 280 K and 245 kPa to 880 K. This is achieved by adding
heat to the system under quasi-equilibrium conditions. What is the
work done by the air during this process? (Use the appropriate sign
convention.) What is the amount of heat transferred for this
process? (Use the appropriate sign convention.) Considering the
actual variation in the specific heat of air during the process,
what is the change in...

1- A certain amount of O2, as an ideal gas, is contained in a cylinder-piston system and develops a process from T1 = 300 K, P1 = 200 kPa to T2 = 1500 K and P2 = 150 kPa. Determine the specific entropy change in kJ / (kg K).
2- A certain amount of H2O in a closed rigid cylinder is cooled from T1 = 800 ° F and P1 = 100 lbf / in2 to P2 = 20 lbf...

A piston-cylinder assembly containing 3 kg of an ideal gas
undergoes a constant pressure process from an initial volume of 48
m3 to a final volume of 30 m3 . During the
process, the piston supplies 1.2 MJ of work to the gas. The gas has
a constant specific heat at constant volume of 1.80 kJ/(kg∙K) and a
specific gas constant of 1.48 kJ/(kg∙K). Neglect potential and
kinetic energy changes.
a. Determine the initial specific volume of the gas in...

ADVERTISEMENT

Get Answers For Free

Most questions answered within 1 hours.

ADVERTISEMENT

asked 1 hour ago

asked 1 hour ago

asked 1 hour ago

asked 2 hours ago

asked 2 hours ago

asked 2 hours ago

asked 2 hours ago

asked 3 hours ago

asked 3 hours ago

asked 3 hours ago

asked 3 hours ago

asked 3 hours ago