Four kilograms of steam in a piston/cylinder device at 400 kPa and
175 °C undergoes isothermal and mechanically reversible process to
a final pressure such that the steam is completely condensed (i.e.,
became a saturated liquid). Determine Q and W for this process:
(b) Using generalized correlations and Equations (6.70 –
6.74). Comment on the accuracy of your answer.
[Answer: Q = -9,461 kJ, W = 1494.9 kJ]
Five kilograms of water is contained in a rigid, 3 m3 vessel at
P = 1 bar.
A. What is the temperature and physical state (liquid, vapor, or
both liquid and vapor) of the water?
B. What is the specific internal energy of the water in the
vessel?
A piston-cylinder device initially has a volume of 1.5 m3
containing steam at 300 kPa absolute and 150 oC. It is then heated
so it expands at constant pressure until it reaches a temperature
of 400 oC.
Draw a diagram of the device showing system boundary and flows
of energy. What boundary work is done by the cylinder, in kJ,
during the expansion? State your assumptions.
1. What is the mass of steam in the piston-cylinder?
2. How much heat...
10 kg of air occupying a cylinder volume of 0.28 m3 is allowed
to expand isentropically
behind a piston to a pressure of 30 bar. The air is then heated at
a constant volume. Finally, the
air is cooled at a constant pressure back to its initial
conditions. The initial pressure is 60 bar.
Calculate the change in entropy, the net work done and the net heat
flow. Sketch the cycle on
the p‐v and T‐s diagrams.
1 kg of saturated steam at 1000 kPa is in a piston-cylinder and
the massless cylinder is held in place by pins. The pins are
removed and the system suddenly and adiabatically expands to 5x its
original volume before the piston hits a pair of upper pins. The
expansion takes place against an atmosphere is 60 kPa. What is the
final specific internal energy of the system? The answer will be in
kJ/kg.
1 kg / s of steam is compressed in an adiabatic compressor from
200 kPa and 200 ° C to 3000 kPa and 400 ° C. How powerful is the
compressor? is this transformation possible (briefly argue)?
A steam boiler of volume 2.3 m3 initially contained 1.7 m3
liquid water in equilibrium with
0.6 m3 of vapour at 100 kPa. The boiler is heated keeping the inlet
and discharge valves closed.
The relief valve is set to lift when the pressure in the boiler
reaches
5500 kPa. Determine the amount of heat supplied to the contents in
the boiler before the relief
valve lifts.
A piston–cylinder device initially contains 2 kg water in 1 m3
at 500 kPa. The system then cools down and the volume drops to half
and pressure of 300 kPa. At this state, the piston is resting on a
set of stops, and the mass of the piston is such that a pressure of
500 kPa is required to move it. (a) Show the process on a P-v, T-v
and P-T diagrams with respect to saturation lines and determine,
(b)...
Two kilograms of CO2 gas is contained in a
piston-cylinder assembly at a pressure of 6.5 bar and a temperature
of 300 K. The piston has a mass of 5000 kg and surface area of
1m2. The friction of the piston on the walls is
significant and cannot be ignored. The atmospheric pressure is
1.01325 bar. The latch holding the piston in position is suddenly
removed and the gas is allowed to expand. The expansion is arrested
when the volume...
An adiabatic tank, 0.5 m3, is initially evacuated and charged
with steam at 500 kPa and 300 C. The final tank pressure is 500
kPa. Determine the final temperature and the entropy
production.