Abstract:The outside serrated integral-fin tubes fabricated by rolling−plowing−extrusion processing were surface-treated through different processes of annealing in hydrogen atmosphere, electrochemical corrosion or sandblasting. The purpose was to eliminate residual stress, clear secondary micro-fins and enhance heat transfer performance. By comparing the surface characteristics, it is found that the finned tubes treated by electrochemical corrosion have the most glabrous surfaces where the fins are almost perfectly reserved. Clear layer cracks can be observed on the top of the fins. These structures are effective in enhancing heat transfer performance when being applied to flow heat exchange. Therefore, the finned tubes treated by electrochemical corrosion are proper for the tubular exchanger with water coolant. The finned tubes treated by sandblasting have rougher surfaces with layer cracks and micro gaps removed. As these structures are useful to clearing adhesive feculence, the tubes are more suitable for the tubular heat exchanger with oil coolant.

Key words: finned tube; surface treating; heat transfer; multi-dimensional surface