Air flows on both sides of a counterflow heat exchanger operating at steady state, with a mass flow rate of 1 lb/s on each side. On one side air enters at 850oR, 60 psia and exits at 1000oR and 50 psia. On the other side air enters at 1300oR, 16 psia and exits at 1155oR and 14.7 psia. Neglecting heat transfer between the heat exchanger and its surroundings as well as the effects of motion and gravity, determine:
(a) The rate of exergy destruction, and
(b) the exergetic efficiency of the heat exchanger.