Question

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 (*T*2).

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?

Answer #1

A piston-cylinder contains 25 g of saturated water vapor and
kept at 300 kPa. We add to the saturated water vapor an amount of
electrical work of 7.2 kJ (via a resistance heater).
Simultaneously, we lose 3.7 kJ from the water.
1.Show the path on a PV diagram.
2.Determine the change in internal energy, the PV work, and the
enthalpy of the system.
3.Determine the final temperature of the system

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

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...

1-kg water in a frictionless piston-cylinder device is initially
at 250°C and 300 kPa (state
1). A total of 700 kJ of work is done ON the water
in order to isothermally reduce its volume to
1/20 of its initial volume (state 2). Determine the magnitude and
direction of the heat transfer
involved in this process.
Answer: -1147 kJ.

A piston cylinder device containing 0.5 kg of water has initial
volume of 0.5L. The device starts and goes through a Carnot cycle
and generates 500.3 kJ work. If the maximum temperature that water
will reach is 1.5 times the minimum temperature of water and during
heat rejection process, water goes from saturated vapor to
saturated liquid phase Find: 1. QH & QL for this cycle 2. TH
& TL for this cycle . 3. Maximum and minimum pressures that...

H3.3 A frictionless piston-cylinder device contains 2 kg of H2O
initially at T1 = 300◦C and p1 = 5 bar. The device is cooled at
constant pressure until the volume is ∀2 = 0.5 m3 . Assume a
quasiequillibrium process which occurs slowly with no acceleration
as the piston moves. Kinetic and potential energy effects are
negligible. Determine: a. work [kJ] during process (indicate
magnitude and direction) b. heat transfer [kJ] during process
(indicate magnitude and direction)

Ammonia contained in a piston–cylinder assembly, initially
saturated vapor at T1 = 4°F, undergoes an isothermal process to a
final specific volume v2 = 5.2 ft3/lb. Determine the final
pressure, in lbf/in2, and the final quality, x2.

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).

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...

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.

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