Question

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 Cv = 0.718 kJ/kg-K, find (a) final temperature - K, (b) mass leaving the cylinder - kg, (c) work - kJ, (d) total entropy change - kJ/K. Assume the enthalpy of the exiting air is that of air at the average of the initial and final temperatures.

Answer #1

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 0.2 m3 piston/cylinder contains air at 400 K and
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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
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What is the change in the air's specific entropy during
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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
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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
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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
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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
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Consider a cold air-standard Diesel cycle. At the beginning of
compression, 102 kPa, and 300 K. The mass of air is 0.120 kg, the
compression ratio is 16, and the cut-off ratio is 2.0
For a cold air-standard analysis use the following values: cp =
1.005 kJ/kgK, cv = 0.718 kJ/kgK, k=1.40, M=28.97 kg/kmol.
Determine the following :
(a) pressure at end of compression stroke, in kPa
(b) temperature at end of compression stroke, in K
(c) maximum temperature in...

A piston cylinder contains 2 lbm of air and operates at a
constant pressure of 400 psia. The initial volume is 1 ft.3 and the
initial temperature is 100°F. The final volume is 4 ft.3 and the
final temperature is 1780°F. Determine the work and its direction
(in or out) and the heat transfer and its direction, in
Btu/lbm.

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 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 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...

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