A hot liquid is filled in a spherical tank with an inner diameter of 3 m and a wall thickness of 3 cm. The tank wall is made of a material with a thermal conductivity of 0.15 W/m∙K. The hot liquid in the tank causes the inner surface temperature to be 100°C, while the tank outer surface is exposed to air at 20°C and has an emissivity of 0.35. Determine the outer surface temperature of the tank. Assume that the properties of air can be evaluated at 40°C and 1 atm pressure. Is this a good assumption?

1. What functions are performed by the flutes on a standard twist drill?
2. Basically, what determines what helix angle a drill should have?
3. When a large-diameter hole is to be drilled, why is a smaller diameter hole often drilled first?
4. What is the function of the margins on a twist drill?
5. What are the primary purposes of reaming?
6. What are the purposes of:
a. Spot facing
b. Counterboring
c. Countersinking
7. Suppose you want to drill a 2-in. thick plate of cast steel (0.4%C), 4-in. diameter hole. An indexable HSS insert drill has been selected. Consider the table below, select the appropriate cutting speed, feed rate. Calculate the spindle speed (rpm), the feed rate (in/min), the MRR, and cutting time. Assume the cutting process will be performed in 3 steps using 3 drills sizes in sequence 1”, then 2”, then 4”. Calculate the cutting total cutting time, considering a proper allowance each time.
8. How much time will be required for milling machine to face mill an AISI 1020 steel surface BHN 150, that is 12 in. long and 5 in. wide, using a 6 in. diameter, eight-tooth tungsten carbide inserted-tooth face mill cutter? Select values of feed per tooth and cutting speed from the provided table, Table 24-1.
9. Draw in two sketches the up milling (conventional milling) and down milling (climb cut) machining set up and show the shape of machined material.
10. Why does down milling dull the cutter more rapidly than up milling when machining sand casting iron?

HEAT TRANSFER QUESTION

A shell-and-tube heat exchanger with one shell pass and four tube passes, that contains 190 pipes (thin walled, 4m long, 2.6 cm diameter), will be used to heat the air. Water enters the pipes at 350 K with 8kg/s mass flow rate while the air enters the shell at 15 C with 18kg/s mass flow rate. In time there will be a fouling factor of 0.0026m²K/W on the inside of pipes. Inside heat transfer coefficient is 450 W/m²K, outside heat transfer coefficient is 200 W/m²K. Using the specific heat values for water and air at 25 C.

Find

a)Effectiveness of HX

b) Heat transfer rate (kW)

c) Exit temperatures of air and water, and show one T-L diagram

Consider four identical circular Euler columns under a compressive axial load with a) one end fixed and the other pinned (or hinged or simply-supported), b) both ends fixed, c) both ends pinned (or hinged or simply-supported), d) one end fixed and the other free. What are the buckling loads Pcr for each one and which one is the strongest against buckling? Given are: the length L of the column and bending rigidity EI, ?

What is your understanding on developed, developing and under develop country? Give
an example of each type of the country.

Two equal-length springs are “nested” together in order to form a shock absorber. If it is designed to arrest the motion of a 2-kg mass that is dropped above the top of the springs from an at-rest position, and the maximum compression of the springs is to be 0.2 m, determine the required stiffness of the inner spring, K B if the outer spring has a stiffness k A = 400 N/m

(s) is unknown, please will you show all the working out. Thank you

Sketch a diagram of an air-water system that uses fan coils around the perimeter and an overhead air distribution system from a central air handler. Show the chiller, and water distribution pumps. Explain the operation of the system in summer season.?

A wet cooling tower is to cool 25 kg/sec of cooling water from 40oC to 25oC at a location where the atmospheric pressure remains constant at 97 kPa. Atmospheric air enters the tower at 25oC and 65% relative humidity and leaves saturated at 35oC. Neglecting the power input to the fan, determine the mass flow rate of the required makeup water.

Air flows in a pipe under fully developed conditions with an average velocity of 1.25 m/s and a temperature of 16°C. The pipe’s inner diameter is 4 cm, and its length is 4 m. The first half of the pipe is kept at a constant wall temperature of 100°C. The second half of the pipe is subjected to a constant heat flux of 200 W. The properties of air at 80°C are ρ = 0.9994 kg/m³, k = 0.02953 W/m·K, v = 2.097 × 10^–5 m²/s, c_p = 1008 J/kg·K, and Pr = 0.7154.

Determine the wall temperature at the exit of the tube.

A hot-rolled steel bar is subjected to a repeated axial tensile load as shown. The material has ultimate tensile stress S_ut=1300MPa. The bar has a diameter of 30mm. The notch sensitivity factor, theoretical stress concentration factor, and factor of safety are q=0.52,K_t=2.42 and n=1 respectively. Find the maximum force F that the bar can carry for 10^4 cycles at 90% reliability

Figures                                                                10 Points

Endurance limit                                                   10 Point

Endurance strength                                             10 Points

Fatigue stress concentration factor                      5points

Determination of force                                        15points

Describe the intake process of a naturally aspirated diesel engine by means of: a. Show the intake (suction) process by drawing the valve timing diagram with respect to TDC and BDC. b. What is the importance of intake valve opening crank angle bTDC c. What is the importance of intake valve closing crank angle aBDC

25. A turbojet engine gets most of its thrust from an airflow that bypasses the combustor and turbine sections.   a. True b. False


26. A turboprop engine gets most of its thrust from an airflow that bypasses the combustor and turbine sections. a. True b. False

27. In a gas turbine engine for aircraft applications, a diffuser is needed at the inlet to … a. Reduce the speed of the air entering the compressor section to near zero relative to the compressor air intake. b. Reduce the pressure of the air entering the compressor. c. Increase the temperature of the air entering the compressor.   d. Reduce heat transfer from the air to the surroundings, as this heat will be of value in the engine.

1. The dependent variable has a score in the case of logistic regression. TRUE or FALSE and why?

2, If the probability of an even A is 0.2 and that of an event B is 0.10 then the odds ratio is: a.1 b. 2.25 c. 2.0 d. 0.5

3. In the case of logistic regression, we estimate how much the natural logarithm of the odds for Y =1 changes for a unit change in X. TRUE or FALSE

4. In binomial logistic regression, the dependent variables consists of more than two categories. TRUE or FALSE and why?

5. Similar to linear regression, logistic regression has one or more independent variables. TRUE or FALSE and why?

A flat surface is made up of electrically heated strips of length 1m and width 0.05m. The strips, which are electrically insulated from one another, are laid with their long sides in contact and an airstream at 25°C flows over the surface in a direction normal to long sides of the strips at a velocity of 65 m/s. Electrical power is supplied individually to each of the strips such that they all have a surface temperature of 229°C. Determine which strip requires the most power. At 400 K, k = 0.0331 W/m·K, ν = 2.610-5 m2·s, ρ = 0.883 kg/m3, Cp = 1013 J/kg·K, Pr = 0.709.