A helical cooling coil of 150 m in length and 12 cm in diameter inside a fermenter was used to maintain the temperature of a fermentation broth at 37 degrees C. When the coil was totally clean, only 15 kg/s cooling water at 12 degrees C were required to be circulated through the coil for controlling the fermentation temperature. The exit water temperature was 36 degrees C.
a) How much heat was removed to maintain the temperature of fermentation broth at 37 degrees C?
b) After a given period of time of operation, a fouling layer was formed on the wall of the coil on the fermentation broth side and 20 kg/s cooling water at the same temperature of 12 degrees C must be circulated through the coil to maintain the fermentation temperature. What was the outlet water temperature?
c) What were the overall heat-transfer coefficients before and after fouling?