Example 2B.2: A 15-cm by 15-cm circuit board is being cooled by air. It is dissipating 890 W/m² of heat to the air from its top surface. The air approaches the circuit board at 25 °C with a velocity of 6 m/s. Determine the surface temperature of the circuit board at the end of the board. Assume the flow to be turbulent at the leading edge of the board since the electronic components are expected to act as turbulators. For air properties evaluations assume a film temperature of 35 °C. Given: Circuit board geometry – length, L = 0.15 m, width, W = 0.15 m Convective heat flux to air, q'" = 890 W/m² Free-stream temp., T = 25 °C. Free-stream velocity, U» = 6 m/s %3D Assumption: Steady state. Only mode of heat transfer from the board is convection. Film temperature is T; = 35°C. Properties are considered constant and uniform. Flow is turbulent. Air is an ideal gas. Properties: Air properties at 35°C: k = 0.0265 W/m°C; v = 16.5×10-6 m²/s; Pr = 0.7 %3D

Example 2B.2: A 15-cm by 15-cm circuit board is being cooled by air. It is dissipating 890 W/m² of heat to the air from its top surface. The air approaches the circuit board at 25 °C with a velocity of 6 m/s. Determine the surface temperature of the circuit board at the end of the board. Assume the flow to be turbulent at the leading edge of the board since the electronic components are expected to act as turbulators. For air properties evaluations assume a film temperature of 35 °C. Given: Circuit board geometry – length, L = 0.15 m, width, W = 0.15 m Convective heat flux to air, q'" = 890 W/m² Free-stream temp., T = 25 °C. Free-stream velocity, U» = 6 m/s %3D Assumption: Steady state. Only mode of heat transfer from the board is convection. Film temperature is T; = 35°C. Properties are considered constant and uniform. Flow is turbulent. Air is an ideal gas. Properties: Air properties at 35°C: k = 0.0265 W/m°C; v = 16.5×10-6 m²/s; Pr = 0.7 %3D

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter6: Forced Convection Over Exterior Surfaces

Section: Chapter Questions

Problem 6.8P

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