| Summary: | 碩士 === 國立中興大學 === 機械工程學系所 === 106 === This work involves an investigation in heat transfer enhancement of repeated transverse studs in circular tubes. First, nine tubes with different stud pitches (33.3, 53.2 and 106.4 mm), and stud diameters (3, 4 and 5 mm) are tested. The surface of the studs is threaded. Air is the working fluid. The pressure drop and heat transfer data are measured and the empirical equations for the Darcy friction factor and Nusselt (Nu) are established. The f and Nu values are individually expressed as a function of the Reynolds number (Re), stud diameter-to-tube diameter ratio (d/Di) and stud pitch-to-tube diameter ratio (p/Di). The result shows that, either for an increase in the d/Di value or for a decrease in the p/Di value, the Nu enhancement index (r1) increases. The Nu/f performance index (r2) tends to slightly decrease with an increase in the Re value, whereas the dependent of the heat transfer per consumed mechanical energy performance index (r3) on the Re value is not apparent. Second, three additional heat transfer enhancing tubes are also tested. One is with smooth studs and the other two differ from the nine tubes indicated above in stud arrangement. Through a comparison of the experimental data, it is shown that both the effects of stud surface roughness and stud arrangement on the heat transfer are insignificant. However, an intensive variation of the orientation of the studs and a rough stud surface would result in an increase in the f value.
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