3 Heating of Oil (10) A hydrocarbon oil enters at 175°F inside a pipe having an inside diameter of 0.0303 ft and a length of 15 ft. The inside pipe surface temperature is constant at 325°F. The oil is to be heated to 250°F in the pipe. How many lb/hr of oil can be heated? The properties of the oil are - 0.50 Btu/lb °F and k = 0.083 Btu/hr-ft-°F. The viscosity of the oil varies with temperature as follows: 150°F, 6.50 cp; 200°F, 5.05 cp; 250°F, 3.80 cp; 300°F, 2.82 cp; 350°F, 1.95 cp.