Automotive exhaust systems often use two catalytic converters. The exhaust temperature is a key factor which determines if the converter functions properly. Analyze an exhaust pipe which connects two such converters to determine the inlet temperature to the second converter if the outlet temperature from the first converter is 600oC, the pipe ID is 5.0 [cm], the length is 0.3 [m] and the mass flow rate is 60 [g/sec]. Model the exhaust as air at atmospheric pressure and assume the wall temperature of the pipe is 100oC. Neglect entrance effects.
Consider the thermal circuit which models the transfer of the heat from the exhaust to the atmosphere, which is at 30oC. Assume the atmospheric air blows over the pipe in cross-flow with a velocity of 50 [m/s] and the pipe is made of 1.5[mm] thick stainless steel.
a) Calculate an estimate of the average heat transfer coefficient on the outside of the pipe.
b) Determine if the inner wall temperature of 100oC used in question 1 is reasonable. For this problem, assume the exhaust gasses in the pipe are uniform and at an average of 500oC.
c) Calculate the drag on the pipe caused by the cross-flow.