posted 11 months ago

(a) Assuming a convection coefficient of h=8 W/m^2*K in a standard oven, is it appropriate to use a lumped capacitance approach? Calculate the time required to heat the potato to a temperature of 140°C.

(b) Assuming h=15 W/m^2*K in a convection oven, is the same approach still appropriate? Calculate the time required to heat to the same temperature.

posted 11 months ago

(a) What type of transient analysis is appropriate for this problem? You must justify your answer.

(b) What is the surface temperature after 60 seconds? Ans: 235°C What is the glass centerline temperature at that time? Does it support your argument in part (a)? Ans: 780°C

(c) How long must the glass be quenched until the glass center line temperature drops below 50°C?

posted 11 months ago

(a) If the bar is constructed of a material with constant thermal conductivity k=115 W/m-K, calculate the magnitude of the heat transfer rate per unit depth (in W/m). Plot the temperature through the bar in the ex-direction from x=0 to L.

(b) Assume that another bar is constructed of a functionally graded material that starts at 20 W/m-K atx=0, and increases linearly to 400 W/m-K at x=L; that is, k(x)=[20+380*(x/L)] W/m-K, where x is in meters.Using the steady finite difference method with five nodes, determine the temperatures at each node and plot on the same figure as in part (a). Some important notes: i) assume each finite-difference control volume has a constant conductivity within it that corresponds to the x-location of that node; ii) when calculating the heat flux from the west face, use the k value from the west control volume, and when calculating east face heat flux, use the k value from the east control volume (this is not precisely correct but is reasonable). How does your plot differ from part (a)?

(c) Estimate the heat transfer rate per unit length through the bar at x=0 using temperatures at nodes 1and 2 and the information above. How does this compare to part (a)? Ans: -1694 W/m (or 1694 W/m in the negative x-direction)

posted 11 months ago

A)- Assuming the loss of material in the form of scale removesand others isnegligible, determine:

1)- We lose about 0.5% of the steel in the whole rolling process

2)- What is the speed of the strip when it exits machines 1,2,..,7

B)- Answer question 1 above if the following loses must be considered.

3)- If the inside diameter (hallow space) is 20", determine the final dimensions And weight of the coil.

1)- what is the final length of the sheet product produced in the process

2)- there is a trimming machine before the coiling process which trims each side of the strip by an average of 0.025"

posted 11 months ago

1)- is the input material satisfy the requirement of the impression forging (i.e., size of the input material)

2)-Can we use a flash-less Forging Process? . Explain your answer.

3)-In case one: a)- Is the output of this process readily useful or need further processing.Explain why

b)- what is the yield of the system

4)- for a production rate of 500 units/day, determine material loss per month. Use the following assumption Day =8 hours, week =40 hours and a month = 4.2 weeks

posted 1 years ago

D. 100 Ångström

E. 1000 Ångström

В. 109 сm

C. 10.9 mm

A. 10° m

posted 1 years ago

Е. 1 pm

P. 1Å

С. 1 nm

В. 1 um

А. 1 mm

posted 1 years ago

E. None of the above

A. Gyroscopes in smartphones

D. All the above

C. Accelerometer for car airbags

B. Microprocessors in Personal Computers

posted 1 years ago

A. Employs negative pressure against outside world to prevent dust flows in

B. Normal paper and wipes

C. Operators wear protective clothing to prevent human dust entering the room

D. All of the above

E. None of the above

posted 1 years ago

b) What is CNC? What are their pros and cons compared to conventional machine tools?(5 marks)

c) Below is an exemplified G code. Please describe each command and the functionof the whole code.(15 marks)