Thermodynamics HW Solutions 225

# Thermodynamics HW Solutions 225 - and thus it may cause the...

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Chapter 15 Steady Heat Conduction Heat Transfer From Finned Surfaces 3-93C Increasing the rate of heat transfer from a surface by increasing the heat transfer surface area. 3-94C The fin efficiency is defined as the ratio of actual heat transfer rate from the fin to the ideal heat transfer rate from the fin if the entire fin were at base temperature, and its value is between 0 and 1. Fin effectiveness is defined as the ratio of heat transfer rate from a finned surface to the heat transfer rate from the same surface if there were no fins, and its value is expected to be greater than 1. 3-95C Heat transfer rate will decrease since a fin effectiveness smaller than 1 indicates that the fin acts as insulation. 3-96C Fins enhance heat transfer from a surface by increasing heat transfer surface area for convection heat transfer. However, adding too many fins on a surface can suffocate the fluid and retard convection,
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Unformatted text preview: and thus it may cause the overall heat transfer coefficient and heat transfer to decrease. 3-97C Effectiveness of a single fin is the ratio of the heat transfer rate from the entire exposed surface of the fin to the heat transfer rate from the fin base area. The overall effectiveness of a finned surface is defined as the ratio of the total heat transfer from the finned surface to the heat transfer from the same surface if there were no fins. 3-98C Fins should be attached on the air side since the convection heat transfer coefficient is lower on the air side than it is on the water side. 3-99C Fins should be attached to the outside since the heat transfer coefficient inside the tube will be higher due to forced convection. Fins should be added to both sides of the tubes when the convection coefficients at the inner and outer surfaces are comparable in magnitude. 3-68...
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