Consider a simplified model of a heat exchanger with heat transfer areas equal on the hot and cold sides and having no fins. Assume that this heat exchanger has to be used alternately as (1) a...

Consider a simplified model of a heat exchanger with heat transfer areas equal on the hot and cold sides and having no fins. Assume that this heat exchanger has to be used alternately as (1) a gas-to-gas heat exchanger (fouling on the compressed air side), (2) steam-to-heavy fuel oil heat exchanger (fouling on the heavy fuel oil side), and (3) liquid-to-liquid heat exchanger (fouling on the ethylene glycol solution side). Determine what would be the required increase in heat transfer area for the various working fluids, comparing the fouled to the clean heat exchanger operation. Assume that only the thermal resistance of the foulant would change the overall heat transfer coefficient (the other conditions remaining unchanged). Assess the typical values of the overall heat transfer coefficients and fouling resistances for described physical situations. The heat transfer rate and mean temperature difference remain the same.