The inlet air to a gas turbine engine is preheated with the engine's exhaust gases. The preheater is insulated so that all heat transfer is internal. The engine's exhaust gas enters the preheater at 800.°F and 1.30 atm pressure and exits at 500.°F and 1.00 atm. The inlet air enters the preheater at 70.0°F and 1.40 atm and exits at 1.30 atm.
The mass flow rates of the inlet air and the exiting exhaust are approximately the same at 2.10 lbm/s. Both gases can be treated as constant specific heat ideal gases.
The specific heat and gas constant of the exhaust gas are (cp)exh. = 0.238 Btu/(lbm·R) and Rexh. = 0.0640 Btu/ (lbm·R). Neglecting all kinetic and potential energies, and taking the local environment (ground state) as p0 = 1.00 atm, and T0 = 70.0°F, determine:
a. The exit temperature of the inlet air.
b. The second law availability efficiency of the preheater.