A crossflow heat exchanger in which one fluid mixed (gas) and one fluid unmixed heats 2.52kg/s of water from 21.1 to 54.4°C by using hot water under pressure entering at 115.6 and leaving at 48.9°C. The outside surface area of the tubes in the exchanger is Ao = 9.30 m2.

a. Calculate the mean temperature difference ΔTm in the exchanger and the overall heat-transfer coefficient Uo.

b. For the same temperatures but using both fluids unmixed, what would be the ΔTm?