A transformer that is 1.5 m long, 0.062 m wide, and 0.05 m high is to be cooled by attaching a 1.5-m x 0.062-m-wide polished aluminum heat sink to its top surface. The heat sink has seven fins, which are 0.024 m high, 2 mm thick, and 1.5 m long. A fan blows air at 25°C parallel to the passages between the fins. The heat sink is to dissipate 30 W of heat and the base temperature of the heat sink is not to exceed 60°C. Assuming the heat sink to be black anodized and thus to have an effective emissivity of 0.90, determine the minimum free-stream velocity the fan needs to supply to avoid overheating. Assume the flow is laminar over the entire finned surface of the transformer. Note that in radiation calculations the base area (1.5-m x 0.062-m) is to be used, not the total surface area. The properties of air at 1 atm and the film temperature of (T+ Too)/2 = (60 + 25)/2 = 42.5°C are k = 0.02681 W/m.°C, v = 1.726 × 10-5 m2/s,

A transformer that is 1.5 m long, 0.062 m wide, and 0.05 m high is to be cooled by attaching a 1.5-m x 0.062-m-wide polished aluminum heat sink to its top surface. The heat sink has seven fins, which are 0.024 m high, 2 mm thick, and 1.5 m long. A fan blows air at 25°C parallel to the passages between the fins. The heat sink is to dissipate 30 W of heat and the base temperature of the heat sink is not to exceed 60°C. Assuming the heat sink to be black anodized and thus to have an effective emissivity of 0.90, determine the minimum free-stream velocity the fan needs to supply to avoid overheating. Assume the flow is laminar over the entire finned surface of the transformer. Note that in radiation calculations the base area (1.5-m x 0.062-m) is to be used, not the total surface area. The properties of air at 1 atm and the film temperature of (T+ Too)/2 = (60 + 25)/2 = 42.5°C are k = 0.02681 W/m.°C, v = 1.726 × 10-5 m2/s,

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 7.17P: Determine the rate of heat transfer per meter length to a light oil flowing through a 2.5-cm-ID,...

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