Poached eggs are cooked in bath of boiling water at 100°C. Over time they reach thermal equilibrium with the bath. They are then
quickly removed from the boiling water and placed in ice water at 0°C to stop the cooking process. Assume the eggs are perfect spheres with a diameter of 4 cm, a thermal conductivity of 2 W/mK, and a thermal diffusivity of 1e^-6 m^2/s. It is very important that the temperature within the eggs remains spatially uniform during the cooling process.
a) Find the maximum heat transfer coefficient of the ice bath that is allowable.b) Assuming the heat transfer coefficient found in (a) is used. Find the eggs should remain in the ice bath to cool them to 75°C.
a) Find the maximum heat transfer coefficient of the ice bath that is allowable.b) Assuming the heat transfer coefficient found in (a) is used. Find the eggs should remain in the ice bath to cool them to 75°C.
1 answer:
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Answer:
Both Brass and 1040 Steel maintain the required ductility of 20%EL.
Explanation:
Solution:-
- This questions implies the use of empirical results for each metal alloy plotted as function of CW% and Yield Strength.
- So for each metal alloy use the attached figures as reference and determine the amount of CW% required for a metal alloy to maintain a Yield Strength Y = 345 MPa.
- Left Figure (first) at Y = 345 MPa ( y -axis ) and read on (x-axis):
1040 Steel --------> 0% CW
Brass ---------------> 22% CW
Copper ------------> 66% CW
The corresponding ductility (%EL) for cold Worked metal alloys can be determined from the right figure. Using the %CW for each metal alloy determined in first step and right figure to determine the resulting ductility.
- Right Figure (second) at respective %CW (x-axis) read on (y-axis)
1040 Steel (0% CW) --------> 25% EL
Brass (22% CW) -------------> 21% EL
Copper (66% CW) ----------> 4% EL
We see that both 1040 Steel and Brass maintain ductilities greater than 20% EL at their required CW% for Yield Strength = 345 MPa.
