In an industrial facility a counter-flow double-pipe heat exchanger uses superheated steam at a temperature of 250°C to heat feed water at 30°C. The superheated steam experiences a temperature drop of 70°C as it exits the heat exchanger. The water to be heated flows through the heat exchanger tube of negligible thickness at a constant rate of 3.47 kg/s. The convective heat transfer coefficient on the superheated steam and water side is 850 W/m²·K and 1250 W/m²·K, respectively. To account for the fouling due to chemical impurities that might be present in the feed water, use an appropriate fouling factor for the water side. Determine

(a) The heat exchanger area required to maintain the exit temperature of the water to a minimum of 70°C,

(b) What would be the required heat exchanger area in case of parallel flow arrangement?

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Steam 250°C Water 30°C