The vent of a dryer is a 60 cm long horizontal stainless steel duct. The inner diameter of the duct is 60 cm, and its wall thickness is 1 cm. Outside the duct, there is quiescent atmospheric air at...

The vent of a dryer is a 60 cm long horizontal stainless steel duct. The inner diameter of the duct is 60 cm, and its wall thickness is 1 cm. Outside the duct, there is quiescent atmospheric air at 300 K temperature. Warm air at a temperature of 448 K and a velocity of 1.5 m/s flows into the dryer vent at its inlet.

Calculate the average heat transfer coefficients inside and outside the vent. Also, calculate the mean air temperature at the exit of the duct.

Hint: For stainless steel, you can assume that k_w
= 15.2 W/m·K. Also, the thermal resistance of the wall should be included in your analysis. The steady-state heat transfer rate, per unit length, for a pipe can be found from