Air is flowing steadily through a duct whose inner walls are at 800°F. A thermocouple housed in a 1-in. OD steel well with rusty exterior indicates a temperature of 450 o F. The air mass velocity is...

Air is flowing steadily through a duct whose inner walls are at 800°F. A thermocouple housed in a 1-in. OD steel well with rusty exterior indicates a temperature of 450^oF. The air mass velocity is 3600 lbmassh ft². Estimate the true temperature of the air.

A thermocouple inserted in a long duct reads 200^oF. The duct runs through a furnace that maintains the duct walls at 300^oF. Inside the duct a nonabsorbing gas is flowing at such a velocity that the average convective heat transfer coefficient to the thermocouple is 10 Btu/(h ft^2
oF).

What is the gas temperature at the thermocouple in
^oF? (Assume that all surfaces are black and that no heat is conducted along the thermocouple leads.)