Solve the folloiwng problem:
Q: In a manufacturing process, long rods of different diameters are at a uniform temperature of 400°C in a curing oven, from which they are removed and cooled by forced convection in air at 25°C. One of the line operators has observed that it takes 280 seconds for a 40-mm. diameter rod to cool to an safe-to-hand/e temperature of 60°C. For an equivalent convection coefficient, how long will it take for an 80-mm-diameter rod to cool to the same temperature? The thermo physical properties of the rod are p = 2500 kg/m3 · c = 900 J/kg · K, and k = 15 W/m · K. Comment on your result. Did you anticipate this outcome?