Question

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 25^{o}C. During the
compression process heat transfer takes place with the ambient
maintained at 25^{o}C. Assume air as an ideal gas (R =0.287
kJ/kg) and has constant specific heats of C_{p} = 1.004
kJ/kgK and C_{v} = 0.717 kJ/kgK. If the mass of air in the
cylinder is 0.1286 kg, determine

a) the polytropic exponent *n,*

b) the final volume of the air,

c) the work done by the air,

d) the heat transfer and

e) the total entropy generation for the process.

Answer #1

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...

Air expands in a polytropic process (n = 1.35) from 2 MPa and
1200 K to 150 kPa in a piston/cylinder. Determine per
unit mass of air the work produced and the heat transferred during
the expansion process in kJ/kg.

Steam, initially at 700 lbf/in.2, 550°F undergoes a
polytropic process in a piston–cylinder assembly to a final
pressure of 2200 lbf/in.2 Kinetic and potential energy
effects are negligible.
Determine the heat transfer, in Btu per lb of steam, for a
polytropic exponent of 1.4,
(a) using data from the steam tables.
(b) assuming ideal gas behavior.

A mass of one kg of water within a piston–cylinder assembly
undergoes a constant-pressure process from saturated vapor at 500
kPa to a temperature of 260°C. Kinetic and potential energy effects
are negligible. For the water:
a) Evaluate the work, in kJ,
b) If the work is 30 kJ, evaluate the heat transfer, in kJ,
c) If the heat transfer is negligible, evaluate the entropy
production in kJ/K
d) Determine if the process is reversible, irreversible, or
impossible.

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.

Your new engine design consists of a piston cylinder
arrangement. The engine operates with mostly air and a small amount
of fuel. The system undergoes a cycle. The initial Pressure and
temperature are p1= 1bar and T1= 27°C. The system undergoes a power
cycle consisting of the following process:
Process
1-2
constant volume to a pressure, P2 of 4 bars
Process
2-3
expansion of pv=constant
Process 3-1
constant-pressure compression
Draw the system and pv diagrams
If P2 is 4...

1 kg of water in a piston cylinder arrangement is initially in a
saturated liquid state at 1 bar. It undergoes expansion at constant
pressure due to external heat supply to it, to a final state of
saturated vapor.
(i) What is the initial temperature of water in C? (a) 93.50 (b)
96.71 (c) 99.63 (d) 111.4 (e) 12.2
(ii) What is the change in enthalpy of water (kJ/kg-K)? (a)
417.46 (b) 2258.0 (c) 2675.5 (d) 2506.1
(iii) What is...

0.5 kilograms of air are compressed from 100 kPa and 300 K in a
polytropic process, n = 1.3, to a state where V2 = 0.5
V1. The air is further compressed at constant pressure
until the final volume is 0.2 V1 . Draw a sketch of the
processes on a p-V diagram. Determine the work for each
process.

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...

Carbon dioxide (CO2) is compressed in a
piston–cylinder assembly from p1 = 0.7 bar,
T1 = 280 K to p2 = 14 bar.
The initial volume is 0.2 m3. The process is described
by pV1.25 = constant.
Assuming ideal gas behavior and neglecting kinetic and potential
energy effects, determine the work and heat transfer for the
process, each in kJ, using constant specific heats evaluated at 300
K, and data from Table A-23.

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