BENG1 INTRODUCTION to
THERMO-FLUIDS (THER 103)
TUTORIAL EXAMPLES in FIRST LAW CLOSED SYSTEMS (1)
(SSL conditions are 101.325 kPa, and 15°C)
1.
The specific
internal energy of a system containing 2 kg of gas is increased from 120 kJ/kg
to 180 kJ/kg during a constant volume process.
Determine the required heat transfer. [+120 kJ ]
2.
An adiabatic
expansion of 0.5 kg of gas produced a work transfer of 43.5 kJ to the
surroundings. Determine the change in
specific internal energy of the fluid during the process. [ -87 kJ/kg]
3.
A gas contained
in a cylinder undergoes an adiabatic process in which 40 kJ of energy are
transferred to the surroundings as work, followed by a constant volume process
in which 53 kJ of energy are transferred to the surroundings as heat. If the mass of gas in the cylinder as 2 kg,
calculate the change in specific internal energy during each process, and also
the overall change in internal energy of the system.
[ -20kJ/kg;
-26.5kJ/kg : -93 kJ]
4.
0.01 kg of air at
27°C and 100 kPa is heated at isobarically until the temperature is 327°C.
Find:
a)
the volume of the
air at the beginning of the process [0.00861 m3]
b)
the specific
volume of the air at the beginning [0.861 m3/kg]
c)
the density of
the air at the beginning [1.16 kg/m3]
d)
the volume of air
at the end of the process [0.0172 m3]
e)
the change in
internal energy [2154 J]
f)
the work done [-861 J]
g)
the heat supplied
[3015 J]
for air: use R = 287 J/kgK; cv = 718 J/kgK.