Question

A gas initially at 2.8 bar and 60ºC is compressed to a final
pressure of 14 bar in an isothermal internally reversible process.
Determine the work and heat transfer, each in kJ per kg of gas, if
the gas is (a) Refrigerant 134a, (b) air as an ideal gas. Sketch
the process on p–*v* and T–s coordinates

Answer #1

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)...

Show that the work done by an ideal gas during an isothermal
change of state (from initial state 1 to final state 2), in a
closed container is given by; 1W2=m.R.T(ln(v2/v1))
A piston-cylinder device contains 0.2 kg of air, initially at
27oC and 100 kPa. The air is then slowly compressed in an
isothermal process to a final pressure of 400 kPa.
Determine: (a) The work done during this process, and
(b) The heat transferred.

A closed system containing R-134a initially at 280 kPa and 30 °C
undergoes a reversible isothermal process, after which its quality
is 0.40. (a) What is the specific heat and work transfer, q and w,
experienced by the system? (b) Sketch the process on a T-s diagram,
labeling the states and the isobars.

A rigid copper tank, initially containing 1 m3 of air at 295 K,
4 bar, is connected by a valve to a large supply line carrying air
at 295 K, 15 bar. The valve is opened only as long as required to
fill the tank with air to a pressure of 15 bar. Finally, the air in
the tank is at 310 K. The copper tank, which has a mass of 20 kg,
is at the same temperature as the...

1 mole of a non-ideal gas is compressed isothermally at 100°C
from 1 bar to 50 bar. What are the heat and work needed for this
(reversible) compression if the gas conforms to the principle of
corresponding states?
The critical properties of the non-ideal gas are Tc = 406 K
and Pc = 11.3 MPa.

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.

A container of gas at 2.8 atm pressure and 120∘C is compressed
at constant temperature until the volume is halved. It is then
further compressed at constant pressure until the volume is halved
again.
1.) What is the final pressure of the gas?(in atm)
2.)What is the final temperature of the gas?(in celsius)

An insulated cylinder is filled with nitrogen gas at 25ºC and
1.00 bar. The nitrogen is then compressed adiabatically with a
constant pressure of 5.00 bar until equilibrium is reached. i. What
is the final temperature of the nitrogen if it is treated as an
ideal gas with molar heat capacity CP = 7/2 R ?
ii. Calculate ΔH (in kJ mol-1 ) and ΔS (in J mol-1 K-1 ) for the
compression. (Hint: Because the enthalpy is a state...

A heat engine composed of 1.6 moles of an ideal, monotonic gas
is initially at 350 K and 1x10^5 Pa. The first step is an
isothermal expansion to a pressure of 5x10^4 Pa. Second, the gas is
compressed at constant pressure back to the inital volume. Finally
the gas returns, at constant volume to the initial state. What is
the total work done by the gas during this cycle? What is the
efficiency of this cycle?

1a. An air-standard cycle consists of the following processes:
isentropic compression from 15 ?C, 1.01 bar through a compression
ratio of 5:1; heat addition at constant volume of 2600 kJ/kg;
isentropic expansion to the initial volume; heat rejection at
constant volume. Sketch the cycle on p-v and T-s diagrams, and
calculate its ideal efficiency, mean effective pressure and peak
pressure.
Answers(0.475, 18.9 bar, 73.0 bar)
b. The cycle is problem (a) is modified so that the heat is
added
(a)...

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