The components of an electronic system dissipating 180 W are located in a 1.4-m-long horizontal duct whose cross section is 20 cm × 20 cm. The components in the duct are cooled by forced air that enters the duct at 30°C and 1 atm at a rate of 0.6 m3/min and leaves at 40°C. Determine the rate of heat transfer from the outer surfaces of the duct to the ambient.

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Natural convection 40 C 180 W 1.4 m 0.6 m min FIGURE P5-95