A counterflow heat exchanger is to heat air entering at 500 degrees Celsius with a flow rate of 6 Kg/s by the exhaust gas entering at 900 degrees Celsius with a flow rate of 4kg/s. The overall heat transfer coefficient is 100 W/m^2K and outlet temperature of air is 551.5 degrees Celsius. Specific heat of air, CP for both air and exhaust gas can be taken as 1100 J/Kg K.
I posted this question before but the expert did not answer part 2 of the question. Also when determining the heat transfer area needed in the first part of the question he got that the the outlet temperature of the exhaust gas he got that temperature to be higher than the inlet, shouldn't it be lower since it is heating up another fluid and therefore giving away energy?
Please answer this question in a step by step manner I am trying to learn how to solve the problem.