BENG1 INTRODUCTION to
THERMO-FLUIDS (THER 103)
TUTORIAL EXAMPLES in FLUID PROPERTIES
(SSL conditions are 101.325 kPa, and 15°C)
1.
A
system contains 1.45 kg of gas with a specific enthalpy of 1200 kJ/kg. What is
the total system enthalpy? [1740 kJ]
2.
If
the gas in Qu.1 occupies a volume of 0.87 m³, what is its specific volume?
What is its density? [v = 0.600 m³/kg; r=
1.667 kg/m³ ]
3.
Convert
the following temperatures to K: 112°C; 2400°C; 67°F.
[385K; 2673K; 292.4K]
4.
A
thermometer contains 1 gm of mercury. Calculate the height change in a 70
micron bore if its temperature rises from 20°C to 80°C. Assume the relative
density of mercury = 13.6, and 
. [20.64 cm]
5.
An
ordinary pressure gauge used to measure the pressure in a refrigeration
evaporator indicates 110 kPa. The temperature of evaporation of a refrigerant
depends on the pressure. Determine the evaporating temperature given the
evaporating temperature/pressure relationship below. [-11.05 °C]
|
Absolute
pressure (kPa) |
100.3 |
123.6 |
150.8 |
182.5 |
219.0 |
|
Evaporating
temp. (°C) |
-30 |
-25 |
-20 |
-15 |
-10 |
6.
In
an experimental investigation it was noted that 0.5 kg of a gas occupied 0.1033
m³ at a pressure of 3 bar absolute and 55°C. After isobaric heat transfer its
temperature increased to 80°C and its volume increased by 7.62%. A change in
its specific internal energy was known to be related to a change in temperature
by: Du = cv DT where cv
= 0.63 kJ/kgK. Determine the change in
specific enthalpy. [20.473 kJ/kg]
7.
An
oil of unknown viscosity is placed in the gap between two concentric cylinders.
The gap between the cylinders is 1mm and the torque required to rotate the
inner cylinder at 20 RPM was found to be 0.17 Nm. If the inner cylinder
diameter is 200mm and its depth is 100mm find the oil’s dynamic viscosity.
[0.1292 Ns/m², or 129.2 centipoise]
8.
Using
the SPECIFIC ENTHALPY OF WATER AND STEAM table given in your notes, find the
specify enthalpy of water/steam at a pressure of 6 MPa, and temperatures of
35°C and 425°C respectively. Use these figures to determine the rate at which
heat has to be supplied to generate 25 kg/s of steam at 425°C and 6 MPa from
water at 35°C and 6 MPa. [151.94 kJ/kg and 3243 kJ/kg; 77.28 MW]