Question

4-23 After heat treatment, the 2-cm thick metal plates (k = 180 W/m·K, ρ = 2800 kg/m3, and cp

= 880 J/kg·K) are conveyed through a cooling chamber with a length of 10 m. The plates enter the cooling

chamber at an initial temperature of 500°C. The cooling chamber maintains a temperature of 10°C, and

the convection heat transfer coefficient is given as a function of the air velocity blowing over the plates h

= 33V0.8, where h is in W/m2·K and V is in m/s. To prevent any incident of thermal burn, it is necessary

for the plates to exit the cooling chamber at a temperature below 50°C. In designing the cooling process to

meet this safety criteria, use excel to investigate the effect of the air velocity on the

temperature of the plates at the exit of the cooling chamber. Let the air velocity vary from 0 to 40 m/s, and

plot the temperatures of the plates exiting the cooling chamber as a function of air velocity at the moving

plate speed of 2, 5, and 8 cm/s.

Answer 1