2. Water at a temperature of 80 °C and velocity of 1.2 m/s is flowing parallel to one side of a smooth flat plate. The plate is maintained at a constant temperature of 24 °C and is 0.8 m long and 0.5 m wide. Determine the following:

1. The heat flux at a distance x = 0.6m from the front edge of the plate, q” = ____________
2. The location of the maximum heat flux on the plate, x = _________
3. The total convective heat transfer from the water to the top surface of the plate,

                                                                                                                   q = __________

4. The convective heat transfer between the water and the plate from x = 0.6 m to x = 0.8m

                                                                                                                   q₂ = __________

for water: ρ = 987 kg/m³, µ = 528 x 10^-6 N·s/m², k = 645 x 10^-3 W/m·K, Pr = 3.42

An uninsulated steam pipe with a wall temperature of 140 °C passes through a room of quiescent air of 14 °C. The pipe is horizontal and has an outer diameter of 20 cm. Find the following (include units if needed):

a) The temperature to evaluate properties = __________

b) The Rayleigh number, _____________

c) The heat transfer coefficient, h = ____________

d) q’ along the pipe = ________________

e) The pipe diameter is decreased by 50%. If all other parameters remain the same, will the heat transfer coefficient increase, decrease or stay the same? ___________. Justify your answer mathematically. For air: ν = 20.92 x 10-6 m2/s, α = 29.9 x 10-6 m2/s, 30 x 10-3 W/m·K, Pr = 0.7

1. Rank in order of total heat input (Note: don’t confuse with heat input RATE) and overall size of heat affected zone: GTAW, SMAW, Oxyfuel, laser beam welding

2. What are the advantages of reducing total heat input in a weld?

In a marine gas turbine unit a high-pressure turbine drives the compressor, and a low-pressure turbine drives the propeller through suitable gearing. The overall pressure ratio is 4/1, and the maximum temperature is 650⁰C. The isentropic efficiencies of the compressor, High Pressure turbine, and Low Pressure turbine are 0.8, 0.83 and 0.85 respectively, and the mechanical efficiency of both shafts is 98%.

Calculate the pressure entering the Low Pressure turbine when the air intake conditions are 1.01 bar and 25⁰C. Calculate also the thermal efficiency and the shaft power when the mass air flow is 60 kg/s. Neglect kinetic energy changes, and the pressure loss in combustion.

For all compression processes take c_p = 1.005 kJ/kg K and ɣ=1.4; for the combustion and expansion processes take c_p = 1.15 kJ/kg K and ɣ=1.333. Neglect the mass of fuel.

A 750-g collar can slide along the horizontal rod shown. It is attached to an elastic cord with an undeformed length of 300 mm and a spring constant of 250 N/m. Knowing that the collar is released from rest at A and neglecting friction, determine the speed of the collar at B and at E. (Round the final answer to two decimal places.)

LESSON: Heat transfer

Explain what the characteristic dimension of x,L,D is for different geometries in calculation of dimensionless numbers (Nu,Re,Gr) in forced and natural Transport.

A gas turbine unit has a pressure ratio of 5/1 and a maximum cycle temperature of 550⁰C. The turbine drives the compressor and an electric generator., the mechanical efficiency of the drive being 97%. The ambient temperature is 20⁰C and the isentropic efficiencies of the compressor and turbine are 0.8 and 0.83 respectively.

Calculate the power output in kilowatts for an airflow of 15kg/s. Calculate also the thermal efficiency and the work ratio. Neglect changes in kinetic energy, and the loss of pressure in the combustion chamber.

Take c_p = 1.005 kJ/kg K and ɣ=1.4 for the compression process, and take c_p = 1.15 kJ/kg K and ɣ=1.333 for all combustion and expansion processes.

air behaves as an ideal gas with R = 0.287 k J k g K.

1. A compressor operates at steady state and takes in air from ambient 0 kPa, gage and 300 K. The outlet pressure is 60 kPa, gage and 300 K. Determine:
   1. the mass flow rate if the inlet area is 10 cm² and the inlet pressure is -3 kPa, gage.
   2. the minimum outlet temperature that is possible for this compressor.
   3. the isentropic efficiency of the compressor, assuming no heat loss.
   4. if there is a heat loss of 20 kJ/kg, the work required to run the compressor, and the new isentropic efficiency.

1. Make a search to introduce the design view point for the subject of brakes and friction clutches.

Determine the quality (if saturated) or temperature (if superheated) of the following: (show details of your answer, not just write the final answer)

a) Water at p=50 kPa, v=1 m3/kg

b) Water at p=1.6 MPa, v=0.15 m3/kg

c) Water at p=7 MPa, h=3160 kJ/kg

d) Refrigerant R-134a at p=200 kPa, v=0.009 m3/kg

e) Refrigerant R-134a at p=0.2 MPa, v=0.12 m3/kg

A Turbojet-engined aircraft flies at 350m/s at an altitude of 9000 m. The pressure at this height is 30 kPa and the temperature is-32⁰ C. The pressure ratio of the compressor is 12, the turbine input temperature is 1400 K. Air enters the compressor with a flow of 60 kg/s and the heat value of the fuel is 42 700 kJ/kg. Admitting that adiabatic efficiency of compressor, turbine and Lule is 100% and specific temperatures are constant at room temperature,
a) The speed at which the combustion end gases exit the engine,
b) Reaction force,
c) Calculate the amount of fuel consumed in Unit time. (k=1.4 Cp=1.005 kj/kgK )

In a gas turbine with two-stage compression and expansion, the total pressure ratio is 12. Air enters the compressor at a temperature of 320 K and the turbine at a temperature of 1320 K. The isanthropic efficiency of the compressors is 75%, the efficiency of the turbines is 87% and the regenerator is 78%. Considering the change of specific temperatures with temperature;
a) back work rate,
b) calculate the thermal efficiency of the cycle.

Project Communication Management is of utmost importance in the modern age with an array of technology tools available for use in projects. You may have had several experiences of projects suffering due to poor communication and documentation. Evaluate the importance of a good document management system for a project and explain 5 key strategies you would have as a project engineer to better control project documentation and communication.

You are using a silver spoon to stir water that just started boiling so that you can achieve a more even heat distribution in your water. The spoon is partially immersed in boiling water and a thermometer in your kitchen reads 27 °C. The handle of the spoon has a cross section of 2mm × 1cm and extends 15 cm in the air from the free surface of the water. The heat transfer coefficient at the exposed surfaces of the spoon handle is 3 W/m2×K.

A) Determine the temperature difference across the exposed surface of the spoon handle.

B) Can the lumped sum analysis be applied to the water as it cools? Provide justification to support your answer.

******Note:

Your answer must provide the following:

1. Assumptions: state all assumptions necessary to solve the problem, explain their relevance and

   validate them where necessary.

2. Schematic: draw a schematic showing the flow of energy in your system

3. What are the modes of heat transfer that the spoon is exposed to?

4. Is this a time dependent or steady state problem? Why or why not?

5. Is this a 1-D, 2-D or 3-D problem? Why or why not?

6. What is the thermal conductivity of the material? Can you assume it constant and if so, for what

   ranges?

7. The heat transfer coefficient is a function of many variables. Discuss the variables and whether the

   heat transfer coefficient can be assumed to be constant

8. What boundary condition are you applying and why?

9. Concluding remarks: explain the meaning of the answers obtained