Consider the air cooling system and conditions
Consider conditions for which there is a uniform heat transfer rate per unit length, qi'= 1.25 X 105 W/m, from the exhaust gases to the pipe inner surface, while air flows through the annular passage at a rate of m· a = 2.1 kg/s. The thin-walled inner pipe is of diameter Di = 2 m, while the outer pipe, which is well insulated from the surroundings, is of diameter Do = 2.05 m. The air properties may be taken to be cp = 1030 J/kg · K, µ, = 270 X 10-7 N · s/m2, k = 0.041 W/m · K, and Pr = 0.68.
(a) If air enters at Ta,1 = 300 K and L = 7 m, what is the air outlet temperature Ta,2?
(b) If the airflow is fully developed throughout the annular region, what is the temperature of the inner pipe at the inlet (Ts,i,1) and outlet (Ts,i,2) sections of the device? What is the outer surface temperatureTs,o,1 at the inlet?