Heat transfer from an electronic circuit board is to be determined by placing a model for the board in a wind tunnel. The model is a 15 cm square plate with embedded electrical heaters. The wind from the tunnel air is delivered at 20°C. Determine the average temperature of the model as a function of power dissipation for an air velocity of 2.5 and 10 m/s. The model is pitched 30°C and yawed 10° with respect to the flow direction. The surface of the model acts as a blackbody.

GIVEN

A Model square electronic circuit board pitched 30° and yawed 10° in a wind tunnel

Length of a side (L) = 15 cm = 0.15 m

Air temperature (T∞) = 20°C = 293 K

Air velocity (U∞) = 2.5m/s or 10 m/s

ASSUMPTIONS

Steady state

The surface of the model acts as a black body (ε = 1.0)

The wind tunnel acts as a black body enclosure at the air temperature

Alr .- 20 U=2.5 or 10 m/s- FL= 15 cm- e- 30 - 10