| Summary: | 博士 === 國立高雄海洋科技大學 === 輪機工程研究所 === 98 === Heat transfer measurements for an impinging jet-array onto two enhanced surfaces using concave and convex dimples with effusions are performed to acquire the detailed Nusselt number (Nu) distributions. The study focuses on the effects of effusions on local and area-averaged heat transfer performances with jet Reynolds number (Re) and separation distance (S/Dj) varying in the ranges of 5000≦Re≦15000 and 0.5≦S/Dj≦10. For each Re and S/Dj tested, three sets of heat transfer data are acquired from each effused impinging surface at three eccentricities (E) between jet-centre and dimple-centre of 0, 1/4 and 1/2 dimple-pitch (H). Effects of effusions on heat transfer performances are revealed by comparing the Nu measurements obtained from each dimpled surface with and without effusion. A set of selected experimental data illustrates the influences of effusions on the interdependent impacts of surface topology, Re, S/Dj and E/H on the detailed Nu distributions and the area averaged Nu over the central jet region ( ). Relative enhancements in heat transfer power convected by each dimpled surface with and without effusion from the references detected from the smooth-walled impinging surface without effusion are examined for each Re, S/Dj and E/H tested. To assist the engineering applications, six correlations for two effused surfaces with concave and convex dimples at E/H=0, 1/4 and 1/2 are individually obtained using Re and S/Dj as the controlling parameters.
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