The temperature of air flowing through a 25-cm-diameter duct whose inner walls are at 320°C is to be-measured using a thermocouple soldered in a cylindrical steel well of 1.2-cm OD with an oxidized exterior, as shown in the accompanying sketch. The air flows normal to the cylinder at a mass velocity of 17,600 kg/h m2. If the temperature indicated by the thermocouple is 200°C, estimate the actual temperature of the air.
