A counter-flowing heat exchanger conserves energy by heating cold outside fresh air at 10°C with the outgoing combustion gas (air) at 100°C. Assume both flows are 1 kg/* and the temperature difference between the flows at any point is 50°C. What is the incoming fresh air temperature after the heat exchanger? What is the equivalent (single) convective heat transfer coefficient between the flows if the interface area is 2 m2?
The outside fresh air is heated up to T4 = 50°C (100 – 50), the heat transfer needed is
This heat transfer takes place with a temperature difference of 50°C throughout
