Thermodynamics

1. ASSIGNMENT 1
1. A cylindrical storage tank of diameter 2.8 m and height of 10 m is completely
filled with a certain fluid. If the mass of the fluid in the tank is 54000 kg and the
density of water is 1000 kg/m3
, determine the volume, density and specific gravity
of the fluid in the storage tank.
(61.58 m3
, 876.9 kg/m3
, 0.8769)
2. A weather research instrument is suspended below a helium-filled balloon which
is a sphere of 1.725 m in diameter. If the specific volume of helium is 5.62 m3
/kg,
determine the volume and mass of the helium in the balloon.
(Given: 3
r
3
4
Vsphere  )
(2.688 m3
, 0.4783 kg)
3. An empty bottle has a mass of 1.2 kg. The bottle has a mass of 1.7 kg when it is
filled with water. When it is filled with another fluid, the mass of the bottle
becomes 1.5 kg. Assuming the density of the water is 1000 kg/m3
. Determine:
(a) The volume of the bottle, Vbottle;
(b) The density of the fluid, fluid;
(c) The specific gravity of the fluid, s.gfluid.
(0.0005 m3
, 600 kg/m3
, 0.6)
4. In the working stroke of an air motor, the compressed air has an internal energy
of 425 kJ at the beginning of the expansion and an internal energy of 210 kJ after
expansion. If the work done by the air during the expansion is 98 kJ, calculate the
heat energy transferred during the process and state whether it is a cooling or
heating process.
(-117 kJ, it is a cooling process)
5. During the working stroke of an internal combustion engine, 625 kJ of heat
energy is rejected from the system to its surroundings and the internal energy of
the working fluid in the system has reduced by 1350 kJ. Determine the work
energy transferred during the process and state whether it is an expansion or a
compression process.
(725 kJ, an expansion process)
6. In a close system, during a non-flow process, 280 kJ of heat energy is supplied
to the system from its surroundings.
(a) If no work energy is transferred during the process, determine
the change in internal energy during the process and state
whether it is an increase or a decrease.
(b) If 325 kJ of work energy is produced by the system during the
process, determine the change in internal energy during the
process and state whether it is an increase or a decrease.

2. (280 kJ, an increase in internal energy, - 45 kJ, a decrease in internal
energy)
7. An open system, operating under steady flow conditions, receives fluid at the
following state: pressure 15 bar; specific volume 0.2029 m3
/kg; specific internal
energy 2952 kJ/kg; velocity 30 m/s. The fluid leaves the system at the following
state: pressure 1.5 bar; specific volume 1.286 m3
/kg; specific internal energy
2580 kJ/kg; velocity 100 m/s. The mass flow rate of the fluid is 0.5 kg/s and the
inlet pipe is 20 m above the outlet pipe. If heat energy is lost to the surroundings
at the rate of 28 kJ/s, determine the power developed by the system.
(211.6 kJ/s)
8. In a steady flow process, 0.65 kg/s of fluid enters the system with a velocity of
150 m/s. The fluid leaves the system with a velocity of 60 m/s. If the specific
enthalpy of the fluid leaving is 345 kJ/kg smaller than that of the entering and the
heat lost to its surroundings is 60 kJ/s, determine the power developed by the
system. Assume the change in potential energy is negligible.
(170.39 kJ/s)
9. In a steady flow process, 1.8 kg/s of fluid enters the system with a velocity of 120
m/s and specific enthalpy of 3250 kJ/kg and leaves the system with a velocity of
30 m/s and specific enthalpy of 1630 kJ/kg. If the heat energy lost to its
surrounding is 200 kJ/s, and the change in potential energy is negligible,
determine
(b) the power developed by the system,
(c) the cross section area of the inlet pipe, if the specific volume of the
fluid at the inlet is 0.14 m3
/kg.
(Ans. 2728 kJ/s, 0.0021m2
)