1. A counter-flow heat exchanger was designed to cool 13,000 lb/h of 100% acetic acid from 250°F to 150°F by heating 19,000 lb/h of butyl alcohol from 100°F to 157°F. An overall heat-transfer coefficient of 85 Btu/h ft².°F was used for the design. When first placed in service, the acetic acid outlet temperature was found to be 117°F. It gradually rose to 135°F over a period of several months and then remained essentially constant, indicating that the exchanger was over-sized. (a) Use the design data to calculate the amount of heat-transfer surface area in the heat exchanger. (b) Use the initial operating data to calculate the value of the clean overall heat-transfer coefficient. (c) Use the final operating data to calculate the value of the overall heat-transfer coefficient after fouling has occurred. (d) Use the values of Uc and Up found in parts (b) and (c) to obtain the correct (experimental) value of the total fouling factor, RD=RDi (Do/Di) + RDo, for the system.