Question

A gas undergoes a process in a piston–cylinder assembly during
which the pressure-specific volume relation is
*pv*^{1.2} = *constant*. The mass of the gas
is 0.4 lb and the following data are known: *p*_{1}
= 160 lbf/in.^{2}, *V*_{1} = 1
ft^{3}, and *p*_{2} = 300
lbf/in.^{2} During the process, heat transfer *from*
the gas is 2.1 Btu. Kinetic and potential energy effects are
negligible. Determine the change in specific internal energy of the
gas, in Btu/lb.

Δu=

Answer #1

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.

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.

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.

Oxygen gas is contained in a piston cylinder assembly at an
initial pressure of 1000 kPa and expands from 0.2 m3 to 1.0 m3 by a
process where PV = constant. The gas has an internal energy change
of -200 kJ. Calculate the work (kJ) and the heat transfer (kJ) done
during the process.

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)

One gram-mole of ideal gas is contained in a piston-cylinder
assembly. Cp=(7/2)R, Cv=(5/2)R. The gas expands from 3 to 1 atm.
Heat of 1000J is transferred to the gas during the process.
External pressure maintains at 1 atm throughout. Initial
temperature of the gas is 300K. Find work and internal energy
change.

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...

A system of mass 10 kg undergoes a process during which there is
no work, the elevation decreases by 50 m, and the velocity
increases from 15 m/s to 50 m/s. The specific internal energy
decreases by 5 kJ/kg and the acceleration of gravity is constant at
9.8 m/s2. Determine the change in kinetic energy, in kJ,
and the amount of energy transfer by heat for the process, in
kJ.

When gas expands in a cylinder with radius r, the
pressure P at any given time is a function of the volume
V: P = P(V). The force exerted
by the gas on the piston (see the figure) is the product of the
pressure and the area: F =
πr2P. The work done by the
gas when the volume expands from volume V1 to
volume V2 is
W =
V2
P
dV
V1
.
In a steam engine the pressure...

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