An electronic circuit board is the shape of a flat plate 0.3 m x 0.3 m in plan-form and dissipates 15 W. It may be placed in operation on an insulated surface in a horizontal position or at an angle of 45 degrees to horizontal, both in still air at 25°C. If the circuit would fail above 60°C, determine if the two proposed installations are safe.

GIVEN

• A flat plate with insulated back, horizontal or at an angle of 45 degrees in still air
• Plate size (s x s) = 0.3m x 0.3 m
• Heat generation rate (q_G) = 15W
• Air temperature (T_∞) = 25°C
• Maximum plate temperature (T_s) = 60°C

ASSUMPTIONS

• Radiative heat transfer is negligible

Still Air T = 25C Ts = 60C 45 0.3 m- Case 1 Case 2