! Required information A 15-cm x 20-cm printed circuit board whose components are not allowed to come into direct contact with air for reliability reasons is to be cooled by passing cool air through a 20-cm-long channel of rectangular cross section 0.2 cm x 14 cm drilled into the board. The heat generated by the electronic components is conducted across the thin layer of the board to the channel, where it is removed by air that enters the channel at 15°C. The heat flux at the top surface of the channel can be considered to be uniform, and heat transfer through other surfaces is negligible. The velocity of the air at the inlet of the channel does not exceed 4.2 m/s and the surface temperature of the channel remains under 50°C. Assume that the flow is fully developed in the channel. Air 15°C Air channel Electronic 0.2 cm x 14 cm components Given: Nu = 8.24 The properties of air at a bulk mean temperature of 25°C: p=1.184 kg/m³ k = 0.02551 W/m°C v=1.562×105 m²/s Cp = 1007 J/kg.°C Pr = 0.7296 The heat transfer coefficient for the circuit board is W/m².°C.

! Required information A 15-cm x 20-cm printed circuit board whose components are not allowed to come into direct contact with air for reliability reasons is to be cooled by passing cool air through a 20-cm-long channel of rectangular cross section 0.2 cm x 14 cm drilled into the board. The heat generated by the electronic components is conducted across the thin layer of the board to the channel, where it is removed by air that enters the channel at 15°C. The heat flux at the top surface of the channel can be considered to be uniform, and heat transfer through other surfaces is negligible. The velocity of the air at the inlet of the channel does not exceed 4.2 m/s and the surface temperature of the channel remains under 50°C. Assume that the flow is fully developed in the channel. Air 15°C Air channel Electronic 0.2 cm x 14 cm components Given: Nu = 8.24 The properties of air at a bulk mean temperature of 25°C: p=1.184 kg/m³ k = 0.02551 W/m°C v=1.562×105 m²/s Cp = 1007 J/kg.°C Pr = 0.7296 The heat transfer coefficient for the circuit board is W/m².°C.

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.

Chapter7: Forced Convection Inside Tubes And Ducts

Section: Chapter Questions

Problem 7.43P: 7.43 Liquid sodium is to be heated from 500 K to 600 K by passing it at a flow rate of 5.0 kg/s...

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