Liquid water at 80°C flows with 0.2 kg/s inside a square duct, side 2 cm insulated with a 1 cm thick layer of foam k = 0.1 W/m K. If the outside foam surface is at 25°C how much has the water temperature dropped for 10 m length of duct? Neglect the duct material and any corner effects (A = 4sL).
