Question

10 kg of H2O is reversibly compressed from 600 kPa and 600 oC to 1 MPa in an insulated piston- cylinder assembly. Calculate (a) entropy change (kJ/K) of the system and (b) the final temperature.

Answer #1

A vertical, insulated piston cylinder is filled with saturated
liquid H2O at 50 kPa. A stirrer moves rapidly inside the cylinder
until 22% of the H2O (by mass) evaporates. Determine the net work
done (in kJ/kg), the change in entropy during this process (in
kJ/kg-K) and the entropy generated during this process (in
kJ/kg-K).

2 kg of steam initially at 2.00 MPa and 225?C expands in a
piston-cylinder assembly until the final pressure is 0.10 MPa.
During the process, the temperature of steam is kept constant by
keeping it in a constant temperature atmosphere at 225?C. a. What
is the maximum amount of work that can be produced? What is the
entropy change of steam? What is the entropy change of the
universe? b. Suppose that the actual work done is 80% of the...

In one stroke of a reciprocating compressor, Nitrogen is
isothermally and reversibly compressed in a piston + cylinder from
298 K and 20 bar to 200 bar. Assume 2 moles of gas are processed
per stroke, and the molecular weight of the Nitrogen is 28 kg/kmol,
compute the heat removal (Q) and work (WEC) required in kJ/kg.

Entropy From Steam Tables
A piston-cylinder assembly contain 2 kg of water. The water is
initially at the pressure of 0.5 MPa and the temperature of 300°C.
The water is cooled down at constant pressure process until it is a
saturated vapor. Determine the change in the entropy of the
system.

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 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 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...

Determine the entropy of vaporization of steam at 120 oC from
the Clapeyon equation.
Hints:
1. For saturated water at 120 oC, volume of gas phase = 0.89133
m3/kg, volume of liquid phase = 0.001060 m3/kg;
2. Pressure of water in gas phase = 232.23 kPa at 125 oC
3. Pressure of water in gas phase = 169.18 kPa at 115 oC
A. 1103.4 kJ/kg K
B. 11.22 kJ/kg K
C. 5.61 kJ/kg K
D. 2.81 kJ/kg K
E. Cannot...

Atmospheric pressure is 100 kPa in a system of cylinders and pistons.The mass of the piston is 4 kg and the area of the piston is 4.0 cm2. The following process takes place by external heat transfer. (Gravity acceleration is 10 m / s2).
1. Calculate the pressure inside the cylinder in kPa.
2. The cylinder contains 0.1 kg of water vapor, and the
temperature of the water vapor is 150oC. Find the volume and
internal energy of water vapor...

A piston-cylinder device with a set of stops initially contains
0.35 kg of steam at 1.0 MPa and 900 degrees C. The location of the
stops corresponds to 44 percent of the initial volume. Now the
steam is cooled. Determine the magnitude of the compression work if
the final state is (A) 1.0 MPa and 600 degrees C and W=. kJ (B) 500
kPa. W=. kJ (C) Also determine the temperature at the final state
in part (B). T2=. C

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