Question

In: Mechanical Engineering

A 50 cm *50 cm copper slab 6.25 mm thick has uniform temperature of 300°C. Its...

A 50 cm *50 cm copper slab 6.25 mm thick has uniform temperature of 300°C. Its temperature is suddenly lowered to 36°C. (quenched in water) Take The conductivity k-370 W/mK, the density rho-9100 kg/m³, the specific heat c-0.38 K/kg°C, the convection coefficient h=90 W/m2C.

1- Calculate the surface area, As

a - 0.125 m2
b- 0.5125 m2
c- 0.25 m2
d- 0.5 m2

2. Calculate the volume,

a- 0.0015625 m3
b- 0.003205 m3
c- 0.00078125 m3
d- 0.03587 m3

3. Calculate the characteristic length, Lc

a- 0.0625 m
b- 0.3125 mm
c- 0.00625 m
d- 0.003125 m

4. Calculate the Biot number, Bi

a- 0.00125
b- 0.00074
c- 0.00152
d- 0.000760

5. Calculate the thermal diffusivity, a (alpha)

a- 0.000107 m2/s
b- 0.0000107 m2/s
c- 0.0107 m2/s
d- 0.00107 m2/s

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

a- 1200.7 s
b- 0.125 s
c- 240.14 s
d- 120.07 s

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

a- 1560s
b- 312 s
c- 156 s
d- 0.156s

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

a- 586.275 s
b- 5862.75 s
c- 1172.55 s
d- 0.586 s

9. Calculate the temperature at the surface at time 100s , Ts 2

a- 279 ْ C
b- 210 ْ C
c- 36 ْ C
d- 150.8 ْ C

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

a- 806.204 kJ
b- 485.841 kJ
c- 1139.874 kJ
d- 1.426 kJ

Expert Solution

samet mamat answered 3 months ago

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