Question

An insulated piston–cylinder device initially contains
20 L of air at 140 kPa and 27 °C. Air

is now heated for 10 min by a 100-W resistance heater placed inside
the cylinder. The pressure

of air is maintained constant during this process, and the
surroundings are at 27 °C and 100 kPa.

Determine the exergy destroyed during this process.

Answer #1

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0.75 kg of refrigerant-134a at 120 kPa and 20°C
initially fills a piston-cylinder device. Heat is now transferred
to the refrigerant from a source at 150°C, and the piston which is
resting on a set of stops, starts moving when the pressure inside
reaches 140 kPa. Heat transfer continues until the temperature
reaches 90°C. Assuming the surrounding to be at 25°C and 100 kPa,
determine (a) the work done, (b) the heat transfer, (c) the exergy
destroyed, and (d) the...

A piston-cylinder device initially contains 75 g of saturated
water vapor at 340 kPa . A resistance heater is operated within the
cylinder with a current of 0.6 A from a 300 V source until the
volume doubles. At the same time a heat loss of 7 kJ occurs.
Part A)Determine the final temperature (T2).
Part B)Determine the duration of the process.
Part C)
What-if scenario: What is the final
temperature if the piston-cylinder device initially contains
saturated liquid water?

Air in a closed piston cylinder device is initially at 800 K and
at 250 kPa.
The air undergoes a process until it is at 2200 K and at 750
kPa.
What is the change in the air's specific entropy during
this process (kJ/kgK)?

A
piston-cylinder device contains 3.2 kg of air at 400 kPa and 10°C.
Heat is transfered to air and the piston is allowed to expand at
constant pressure until its temperature reaches 50°C. The work done
during this expansion process is: Use kj units

A piston cylinder device contains 0.15 kg of air initially at 2
MPa and 350 C. First, the air expands isothermally to a pressure of
500 kPa. Then, it is compressed polytropically back to the initial
pressure (2 MPa) with a polytropic exponent of 1.2. Find the work
performed or introduced by or to the air for each process. Express
it both times in kJ.

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...

Frictionless piston-cylinder system.
Initially contains 167 L of saturated liquid
Refrigerant-134a.
The piston can move freely in such that it maintains pressure at
877 kPa, an Isobaric process.
The Refrigerant-134a is heated until its temperature rises to 70
℃
Determine:
The work was done during the process in (kJ) units?

An insulated cylinder fitted with a movable piston to maintain
constant pressure initially contains 100 g of ice at -10 C. Heat is
supplied to the contents at a constant rate by a 100 W heater. Make
a graph showing temperature of the cylinder contents as a function
of time starting at t = 0, when the temperature is -10 C and ending
when the temperature is 110 C. ( c = 2.0 kJ/ kg K for specific heat
of...

3.A piston-cylinder system contains 2.4kg of air at 120 oC and
250 kPa. The air is then heated at constant pressure until its
volume increases by 45%. Calculate the final temperature and the
change in volume.

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