A 25-mm-OD copper tube is to be used to boil water at atmospheric pressure. 

(a) Estimate the maximum heat flux obtainable as the temperature of the copper surface is increased. 

(b) If the temperature of the copper surface is 210°C, calculate the boiling film coefficient and the heat flux. The interfacial tension of water at temperatures above 80°C is given by σ = 78.38(1-0.0025T) where σ = interfacial tension, dyn/cm T= temperature, °C