Assume that the kerosene of Prob. 12.4 is replaced with water at 110F and flowing at a

Assume that the kerosene of Prob. 12.4 is replaced with water at 110ºF and flowing at a velocity of 8 ft/s. What percentage increase in overall coefficient may be expected if the tube surfaces remain clean?

Prob. 12.4

Kerosene is heated by hot water in a shell-and-tube heater. The kerosene is inside the tubes, and the water is outside. The flow is countercurrent. The average temperature of the kerosene is 110°F, and the average linear velocity is 8 ft/s. The properties of the kerosene at 110°F are: specific gravity, 0.805; viscosity, 1.5 cP; specific heat.0.583 Btu/lb · °F; and thermal conductivity, 0.0875 Btu/ft·h · °F. The tubes are low-carbon steel ³/₄-in. OD by BWG 16. The heat-transfer coefficient on the shell side is 300 Btu/ft² · h · °F. Calculate the overall coefficient based on the outside area of the tube.