BENG1 INTRODUCTION to
THERMO-FLUIDS (THER 103)
TUTORIAL EXAMPLES in PERFECT GASES
(SSL conditions are 101.325 kPa, and 15°C)
1. A compressed air tank has a volume of
0.5 m3. An ordinary pressure
gauge fitted to the tank reads 19.6 bar. The temperature of the air in the tank is 50°C. Determine:
(i) the absolute
pressure of the air in the tank in kPa;
(ii) the volume the air would occupy at SSL
conditions;
(iii) the mass of air in the tank. [2061.325
kPa; 9.070 m3; 11.12 kg]
2. A cylindrical gas reservoir 6.7 m long
contains 545 kg of gas at a pressure of 1.138 MPa (gauge) and temperature 24°C. Calculate the volume and diameter of the
reservoir, given that 0.02332 m3 of the gas at SSL conditions has a
mass of 0.0366 kg. Determine also, the
volume of the gas at atmospheric pressure and 24°C
required to fill the reservoir to the pressure of 1.138 MPa.
[29.28 m3; 2.359 m; 358.13 m3 ]
3. An empty steel cylinder has a volume of
0.04 m3. A certain gas is
pumped in until the pressure and temperature in the cylinder are 12 MPa and 45°C. The mass of the cylinder is found to have
increased by 5 kg. Determine the value
of the specific gas constant, R. [0.302 kJ/kg K].
4. A cylinder of internal diameter 200 mm
is fitted with a freely sliding piston and contains 1 kg of air at 1 MPa and 20°C. How much heat must be transferred to the air
in order to raise its temperature to 40°C:
(a) If
the piston is fixed so that the process takes place at constant volume;
(b) If
the process takes place at constant pressure?
(c) Calculate the work done by the gas in
‘(b)’. [14.4 kJ;
20.2 kJ; -5.74 kJ]
5. Find the mass of 1.2 kmol of following gases: O2, CO2, and N2.
[38.4; 52.8;
33.6 kg]
6. Find the number of kmol
in 28 kg of the following gases: He, SO2, and CH4.
[7.0;
0.4375; 1.75 kmol]
7. Because all gases have the same
Universal Gas Constant, provided we measure their quantities in kmol we can find the properties of any mixture of perfect
gases. Find the specific gas constant (R) of a mixture of gases consisting of 1
kg O2, 2 kg Argon (A), and 0.5 kg Carbon Monoxide (CO). [0.235 kJ/kgK]