Solved example (2): Analysis of HE using ε-NTU (graph) method for crossflow HE

Hot exhaust gas enters a finned tube cross-flow HE at 300°C and leaves as 100°C. It is used to heat water at flow rate of 1 kg/s from 35 to 125°C. Assume Cp of water is 4.2 kJ/kgK and Cp of gas is 1 kJ/kgK and the overall heat transfer coefficient is 100 W/m2K. Determine the required heat transfer area.