Water flowing at 2 kg/s through a 40-mm-diameter tube is to be heated from 25 to 75°C by maintaining the tube surface temperature at 100°C.

(a) What is the required tube length for these conditions? Will In order to design a water heating system, we wish to consider using tube diameters in the range from 30 to 50 mm. What are the required tube lengths for water flow rates of I, 2, and 3 kg/s, represent this design information graphically.

(b) Plot the pressure gradient as a function of tube diameter for the three flow rates. Assume the tube wall is smooth.