A counter flow heat exchanger is used to heat air entering at 400°C with a flow rate 07
of 6 kg/s by exhaust gas entering at 800°C with a flow rate of 4 kg/s. The overall
heat transfer coefficient is 100 W/mʻK and outlet temperature of the air is 551.5°C.
The specific heat at constant pressure for both air and exhaust gas can be taken as
1100 J/kgK. Calculate:
(i) Heat transfer area needed,
(ii) Number of transfer units.​