In a quench hardening process, steel rods (ρ = 7830 kg/m3, cp = 444 J/kg.K and k = 70 W/m.K) are heated in a furnace to 900oC and then cooled in a water bath to an average temperature of 90oC. The water bath has a uniform temperature of 35oC and convection heat transfer coefficient of 400 W/m2.K. If the steel rods have a diameter of 60 mm and a length of 2.5 m, determine
a) The time required to cool a steel rod from 900oC to 90oC in the water bath
b) The total amount of heat transferred to water during the quenching of a single rod