1. A counter-flow heat exchanger was designed to cool 13,000lb/h of 100% acetic acid from 250F to 150F by heating 19,000lb/h of butyl alcohol from 100F to 157F. An overall heat-transfer coefficient of 85Btu/hft2F was used for the design. When first placed in service, the acetic acid outlet temperature was found to be 117F. It gradually rose to 135F 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 UD 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