Question

Steel balls 12 mm in diameter are annealed by heating to1150 K and then slowly cooling to 400 K in
an air environment for which T∞ = 325 K and h = 20 W/m2 K. Assuming the properties of the steel to be
k = 40 W/m K, ρ = 7800 kg/m3
, and c = 600 J/kg K, estimate the time required for the cooling process.
Now the air temperature increases with time as T∞ (t) = 325 K + at, where a = 0.1875 K/s. Find an
expression for the ball temperature as a function of time T(t).

Answer 1

Answer:

sorry don't know dear...........