Flow Patterns and Hydraulic Losses in Quasi-coil Pipes : The effects of configuration of bend cross section, curvature ratio and bend angle

Abstract

Pipes with bend combinations are much used in the heat exchangers, since the curved path in the bends promotes the mixing in flow for active heat transfer. In the present paper, one of the pipes with bend combinations, namely, quasi-coiled pipes composed of many bend elements are investigated, and the relationships between the hydraulic loss and the secondary flow are studied experimentally. The configurations of the cross sections, the bent angles and the curvature ratios of the bend elements of the quasi-coiled pipes are changed in the experiment. The effects of these factors are investigated in detail. As the result, it is found that the secondary flow becomes the type of a one-directional swirling flow in the quasi-coiled pipes if the bend cross sections are changed from circular to rectangular. Moreover, many interesting results are described.