Part 1: Statics
LEARNING OUTCOMES:
On successful completion of this paper students will be able to:
1. Understand the principles of basic engineering mechanics.
2. Use principles of equilibrium to solve problems involving static force systems
3. Apply principles of statics to solve problems involving pin-jointed structures, frames, machines and friction
4. Calculate properties of plane cross sections including centroids and area moments of inertia.
Key to Graduate Capabilities Profile
1. Knowledge of Engineering Sciences
2. Analysis and Problem solving
3. Design and Synthesis
4. Investigation and research.
5. Risk Management
6. Team Work
7. Communication
8. The Engineer and Society
9. Management and Financial
10. Practical Knowledge
CONTENT
- Basic static concepts
- Scalars and vectors, dot and cross products
- Two and three dimensional force systems, force moment and couple.
- Resultants and free body diagrams
- Equilibrium in two and three dimensions
- Trusses, frames and machines
- Centroids and area moments of area
- Friction
Part 2: Thermofluids 1
LEARNING OUTCOMES:
On successful completion of this paper students will be able to:
5. Understand and calculate parameters pertaining to free thermal expansion of solids and liquids. (1,2)
6. Solve problems in ideal gas systems using the ideal gas equation of state. (1,2)
7. Understand and solve problems using the 1st law of thermodynamics for both closed and open thermodynamic systems (1,2)
8. Explain the implications of the second law to engineering systems and their environment (1,8)
9. Consider the implications of the first and second laws on sustainability with respect to energy and fuel used to drive thermofluid machinery (8)
1. Key to Graduate
2. Knowledge of Engineering Sciences
3. Analysis and Problem solving
4. Design and Synthesis
5. Investigation and research.
6. Risk Management
7. Team Work Capabilities Profile
8. Communication
9. The Engineer and Society
10. Management and Financial
11. Practical Knowledge
CONTENT
- Thermal expansion
- Heat (solids, liquids and phase changes)
- Ideal gas equation of state and applications
- First law of thermodynamics (closed and open systems) and applications
- Continuity equation
- Second law of thermodynamics on sustainability
SECTION A
A1.
a) A steel tape measure is calibrated to measure correctly at 20oC. It is used to measure the distance between two walls when the temperature is -5oC, and the value read from the tape is 28.450 m. Determine the true distance between the walls.
b) A test is made to determine the specific heat of an unidentified liquid by immersing an electric resistance heater in it. The heater is operated for exactly 2 minutes producing a constant rate of heat of 65 W. The mass of the liquid is 780 grams and the temperature changes (during heating time) from 18.55oC to 22.54oC.
(i) Assuming there is no heat loss from the system, determine the specific heat of the liquid.
(ii) In the real test, there would be heat loss. Comment on whether your answer in (i) above or below the true value of the specific heat.
A2.
a) Briefly explain the difference between "temperature" and "heat".
b) An insulated vessel contains 80 kg of water initially at 16oC. The outlet from a pipe leading from a boiler is inserted into the water. From this boiler, steam produced at atmospheric pressure is allowed to flow into the water. Assuming all the steam entering the water condenses, determine the mass of steam required to raise the temperature of the water to 55oC.
c) It is required to fill a compressed-air cylinder, which is essentially a rigid steel tank of volume 20 litres. Before filling, the pressure and temperature of the air in the tank is 110 kPa and 24oC respectively. It is required that 5 kg of air are to be added to the tank. Assuming that the temperature of the air is unchanged by the filling, determine the final pressure in the tank.
A3.
a) A piston-cylinder device contains helium with volume of 20 cm3, pressure of 1.2 MPa and temperature of 20oC. The piston moves and the volume expands so that the pressure drops to 200 kPa. You may assume that the expansion is adiabatic.
(i) Sketch a pressure- volume (p-V) diagram of this process.
(ii) Determine the final temperature and volume at the end of the compression.
(iii) Determine the work done during this process.
b) A steel tank with a volume 3.1 litres will burst if the absolute pressure of the gas exceeds 10 MPa. The tank is filled and sealed with 11 moles of gas at 23ºC. Ignoring the thermal expansion of the steel tank, determine the maximum gas temperature that can be tolerated without rupture.
A4.
(a) A system is taken from state "a" to state "b" along three paths shown in the p-V diagram in figure B3b. The internal energy at "b" is greater than at "a".
(i) State which path (1,2 or 3) would produce the greatest amount of work done by the system and briefly explain your answer.
(ii) State which path (1,2 or 3) would produce the greatest amount of heat transferred and briefly explain your answer.
(iii) State whether the heat transferred in section (ii) is into or out of the system.
(a) Air flows steadily through an adiabatic jet nozzle, entering at 1 MPa, 500oC. The inlet area of the nozzle is 80 cm2. The condition of the air at the exit of the nozzle is 150 kPa and 150oC.
(i) Determine the mass flow rate of air.
(ii) Determine the outlet velocity.
SECTION B
B1.
a) Briefly explain the term "Heat of Vaporisation"
b) Briefly explain the term of "Internal Energy".
c) In the equation pV = nRT it is required that the temperature (T) is in measured in Kelvin (K) and not Celsius (oC). Briefly explain why this is so.
B2.
a) A hollow box made from copper has an internal volume of 25 litres at 20°C. Determine the temperature change that would cause the inside volume of the box to increase by 0.3%
b) A steel ring with an inside diameter of 6.40 cm easily fits over an aluminium rod of diameter 6.42 cm at 20°C. The temperature of the rod and the ring are raised in an oven. Determine the temperature above which the ring will no longer fit over the rod.
B3.
a) A furnace is being designed to produce molten (liquid) aluminium. The furnace will initially be filled with 600 kg of solid aluminium at 20oC. Heat is to be supplied to the furnace so that all of the aluminium is molten (liquid) at its melting temperature. You may assume that the furnace is well insulated and therefore the heat loss from the system may be neglected.
(i) Determine the energy supplied to the furnace to achieve this outcome.
(ii) If it is required that the whole process (from 20oC to molten state) should take 5 hours, determine the power input to the furnace.
B4
a) A piston-cylinder device is filled with helium at 200 kPa, 22oC and a volume of 2.5 litres. The piston then moves so that the volume is reduced to 1.3 litres and the temperature is increased to 129oC. Determine the mass of helium in the system and pressure at the end of the piston movement.
b) Air undergoes an expansion process in a piston-cylinder device. The cylinder initially has a volume of 25 cm3, pressure of 1.2 MPa and temperature of 20oC.
The piston moves so that the volume is doubled and the temperature is constant.
(i) Sketch a pressure- volume (p-V) diagram of this process.
(ii) Determine the pressure at the end of the expansion.
(iii) Determine the work done and heat transferred during this process.
B5
Air flows steadily through an adiabatic turbine, entering at 1.2 MPa, 320oC and 38 m/s. The condition of the air at the exit of the turbine is 150 kPa and 54oC and 25 m/s. The inlet area of the turbine is 60 cm2.
(i) Determine the mass flow rate of air.
(ii) Determine the power output of the turbine.
READINGS
Prescribed Texts Mechanics for Engineers Statics Dynamics R.C. Hibbeler and Kai beng Yap, 7th Ed AUT version
Custom publication compiled by Nates, R.J. "Engineering Principles: Thermofluids", extracted from Young, H., Freedman, R, Bhathal, R and Ford, L. "University Physics and Modern Physics (1st AUS SI Ed), Pearson Education, 2011.
The subject i am working on is thermofluids. I need to know what is the work done to get the answers.
Please use the laws at the end of the exams. Please give me answers which i can understand, also the questions must be thorough and have good logical steps