2. A refrigeration machine has been designed based on R134a. The design capacity is 15 tons.   The evaporator coil design temperature is 8 oC. The refrigerant enters the compressor as a slightly superheated vapor at 15 oC. The condenser coil design pressure is 14 bar. Refrigerant enters the expansion valve as a compressed (subcooled) liquid at 44 C. Note that the temperature of the air passing over the tubing in the evaporator coil will be higher than 8 oC and the temperature of the air passing over the condenser coil will be lower than the coil temperature. Use 80% for the compressor isentropic efficiency.
a. Calculate the power required to run the compressor under these design conditions and the required mass flow rate of R134a. (30 pts)

b. Find the rate of heat transfer for the condenser (high pressure side) of the system. (15 pts)

c. Find the quality of the refrigerant as it enters the evaporator. (10 pts)



3. A small gas turbine engine is used to produce power for auxiliary systems. This is a simple gas turbine open to the atmosphere. Air enters the compressor at 1 bar, 300 K. The compressor pressure ratio is 3.5:1. After passing through the combustion chamber, the air enters the turbine at a temperature of 1300 K. Determine the mass flow rate of air needed for the turbine to produce 60 kW of power. Also determine the heat that must be generated in the combustors. (30 pts) Solar collector …

g. Crazing and peeling are defects associated with glazing process; explain how they are different, and how they can be prevented?
h. Identify at least THREE processes that are line of sight processes.
i. List at least one limitation of PVD process.
j. Identify at least one failure mechanism associated with CVD coatings.
k. Gas turbine blades are to be refurbished; identify the process(es) and major steps involved in this process.
l. Identify at least TWO limitations of flame spraying.
m. What is a comparative advantage of using plasma arc thermal spraying process?

Theory of Bernoulli ,why is p_2<p_1and v_2>v_1?

what is temperature?

what is heat?

why do we use water tower?

1. You are to do a preliminary design study for a small demonstration steam turbine power plant.
- Steam will be provided by a small steam generator fired by natural gas.   - Your system will take in steam at 30 bar and 400 oC.
- The steam passes through a two stage turbine. At a pressure of 10 bars, the steam leaves the first stage of the turbine and will pass through a reheat loop in the steam generator which will boost the temperature back up to 400 oC at this pressure. The steam will then enter the second stage of the turbine.
- When the steam leaves the turbine, the quality should be at least 95% at the turbine exit / condenser inlet.
- The design condenser pressure is 0.70 bar.   
- Heat is removed from the condenser and rejected to the environment through a cooling tower.
a) Assuming isentropic expansion, what are the temperature, enthalpy, and entropy of the steam when it leaves the first stage of the turbine? (5 pts)

b) What are the enthalpy and the entropy of the steam as it leaves the reheater and enters the second stage of the turbine? How much heat (kJ/kg) goes into the steam in the reheat process? (10 pts)

c) Based on an isentropic expansion, what will the quality be at the exit? Will it meet this design limit? (10 pts)
For the following parts use the design turbine power output of 2.5 kW.
d) What mass flow rate is required? (10 pts)

e) At what rate must heat be produced by natural gas burners in the steam generator to produce the steam at the turbine inlet, and how much heat must be produced to reheat the steam between the stages? For a heating rate range of 950-1150 BTU/scf and a cost of $8 per 100 cubic feet, what is the fuel cost per hour to run this unit? (10 pts)

f) What is the feed water pump power demand, and what is the BWR? (10 pts)

8. A closed feedwater heater may be used for deaeration. a. True b. False
9. In a reciprocating power system,   i. Material flows at a constant rate through the device and passes through a turbine to produce shaft power output, ii. Material does not flow at a constant rate through every section of the device.   iii. Power is produced at all times. iv. Power is produced only during part of the cycle in each section of the device and is not produced uniformly at every instant.   v. The power unit consists of one or more piston and cylinder sections with intake and exhaust valves and where fresh fuel and air are taken in during one part of the process, exhaust gases are ejected during another part of the process, and at other times the cylinder is closed off from the intake and exhaust sections (manifolds).   vi. The power unit consists of a compressor, a burner section, and a turbine.   a. Items i), iii), and vi) are correct. b. Items ii) and iii) are correct. c. Items ii), iv) and v) are correct. d. Items ii), iv), and vi) are correct. e. None of these combinations are correct.

10. The Otto cycle model is used with … a. Reciprocating internal combustion engines where the fuel-air mixture is ignited by a spark. b. Reciprocating internal combustion engines where the fuel-air mixture is ignited by high pressures in the cylinders. c. Internal combustion engines with continuous flow of fuel and air (i.e., gas turbine engines). d. External combustion “hot air” engines. e. Vapor compression refrigeration.

11. In an air standard analysis, we pretend that the substance in an engine is pure air, and we analyze this as if energy is put into the air from the outside and, later, waste heat is removed from the air. a. True b. False




12. The Brayton cycle is used to model the operation of … a. Steam Power Plants b. Spark Ignition Internal Combustion Engines c. Compression Ignition Internal Combustion Engines d. Gas Turbine Engines e. Vapor Compression Refrigeration Machines f. None of these

13. For high thermal efficiency, the compression ratio in a spark ignition reciprocating engine is likely to be in the range of … a. 8:1 to 10:1. b. 15:1 to 20:1. c. 20:1 to 40:1. d. None of these are reasonable.

14. For high thermal efficiency, the compression ratio in a compression ignition reciprocating engine is likely to be in the range of … a. 8:1 to 10:1. b. 15:1 to 20:1. c. 20:1 to 40:1. d. None of these are reasonable.

15. The environmental aspects of refrigerants are important considerations in selection. a. True b. False

16. Ammonia may be used as a refrigerant. a. True b. False

17. Carbon Dioxide may be used as a refrigerant. a. True b. False  

Q7. The theory of viscoelasticity is used to describe the behaviour of materials in liquid phase.
a. For each of the models, identify a real life engineering problem where it is applies and describe this.
b. How can the knowledge be used in design applications for the problem you identified above.

c. What are the challenges in the use of the knowledge for solving practical problems.

A 50 cm *50 cm copper slab 6.25 mm thick has uniform temperature of 300℃. Its temperature is suddenly lowered to 36℃. (quenched in water)

Take

The conductivity k=370 W/mK, the density rho=9100 kg/m³, the specific heat c=0.38 kJ/kg℃, the convection coefficient h=90 W/m²℃.

1.      Calculate the surface area, As

2.      Calculate the volume, V.

3.   Calculate the characteristic length, Lc

4.      Calculate the Biot number, Bi

5.      Calculate the thermal diffusivity, α (alpha)

6.      Calculate the constant of time, τ (tau)

7.   Calculate the time required for the plate to reach the temperature of , t₁

8.   Calculate the time required for the plate to reach the temperature of , t2

9.      Calculate the temperature at the surface at time 100 s, Ts2

10.      Calculate the total energy transferred from this plate during the first 100 s, Q

A 15 kW and 1200 r.p.m. motor drives a compressor at 300 r.p.m. through a pair of spur gears having 20° stub teeth. The centre to centre distance between the shafts is 400 mm. The motor pinion is made of forged steel having an allowable static stress as 210 MPa, while the gear is made of cast steel having allowable static stress as 140 MPa. Assuming that the drive operates 8 to 10 hours per day under light shock conditions and face width as 10 times the module, find from the standpoint of strength, 1. Module; 2. Face width; 3. Number of teeth and pitch circle diameter of each gear; 4. Check the gears thus designed from the consideration of wear. The material combination factor for the wear as 1.4 and the flexural endurance limit may be taken as 490 MPa.

Write the simplified conservation of momentum equation for boundary layer on a flat plate and explain the physical meaning of each term in the equation.

Transformation from α-Sn to β-Sn and from β-Sn to α-Sn is exactly the same in terms of the kinetics of the phase transformations.

in heating ventilation and air conditioning (HVAC) explain what operation is carried out to achieve comfort during summer and in winter

Write a small assessment no more than 2 pages including mention above: Alternatives and improvements to refrigerators and freezers in Cape York Community.

Remote Indigenous communities rely on refrigeration and freezers to store large amounts of food over time, ensuring traditional hunting practices can be maintained and people can come and go from Country as needed. This project looks at mechanisms for freezing and storing food beyond the generic available appliances which are dependent on connection to a large, pre-existing solar power supply.

Include the following aspect in this report: write a professional and concise document which draws on appropriate background information. An assignment is well written, contains appropriate references and draws on suitable background information. consider the context of the engineering work including social, cultural, environmental and commercial factors. All required factors are considered with sufficient detail and analysis relevant to the proposed project. And there is evidence that standard engineering principles and practices have been applied to the development of the assignment. The document contains all required elements outlined in the task description including introduction, project objective and possible design criteria.