A probe, used to measure the velocity of air in a lowspeed wind tunnel, is fabricated of an L = 100 mm long, D = 8-mm outside diameter horizontal aluminum tube. Power resistors are inserted into the stationary tube and dissipate P = 1.5 W. The surface temperature of the tube is determined experimentally by measuring the emitted radiation from the exterior of the tube. To maximize surface emission, the exterior of the tube is painted with flat black paint having an emissivity of ε = 0.95.
(a) For air at a temperature and cross flow velocity of T∞ = 25°C, V = 0.1 m/s, respectively, determine the surface temperature of the tube. The surroundings temperature is Tsur = 25°C.
(b) For the conditions of part (a), plot the tube surface temperature versus the cross flow velocity over the range 0.05 m/s ≤ V ≤ 1 m/s.