Example 6.3 Steel tubes with a 3 mm wall thickness and a 25.4 mm outer diameter are used in heat exchangers. 2.3 m/s heating water flows through the tubes at an average bulk temperature of 40"C. Calculate the film heat transfer coefficient from the water to the inside surface of the tubes. Information Properties of water at 40"C Cp 4.18 kJ / kg K k 0.632 W / m K 992 kg / m 6.51 x 10 Ns / m2