Annealing process is a very common practice in metal industry to produce hard materials for construction and load-bearing applications. In annealing, a piece of metal is slowly cooled from high temperature or maintained at a certain fixed temperature for a long time, allowing the individual atoms or molecules occupy state of lowest energy (equilibrium state) which becomes difficult to break or bend; resulting in hard, tough metallic parts. Consider an annealing process where a total of 3000 steel balls used in ball bearing, each of diameter 10 mm are annealed by heating them from 50⁰ C to 900⁰ C in a convection furnace (using hot air free convection in furnace with h=8.5 W/m 2 k ), followed by cooling to 100⁰ C in ambient air at 25⁰ C. The average convective heat transfer coefficient for ambient air is 75 W/m 2 k. Calculate the time required by complete annealing cycle (heating and cooling) by Lumped Capacitance Resistance method and Heisler Charts.