Longitudinal Heat Transfer in Oscillatory Flows in Pipe Bundles of Various Cross Sections

The effect of the sectional shape of pipes on the enhancement of longitudinal heat transfer by fluid pulsation in pipe bundles has been investigated. Bundles of circular, triangular, square and hexagonal pipes are considered. Heat transfer characteristics of each pipe and the gross performance as a pipe bundle including the heat conduction in pipe walls, are discussed. The local distribution of longitudinal heat transfer in pipe section reveals the existence of a region where heat is transferred toward the higher temperature end when the pulsation frequency is sufficiently high. As a pipe bundle, only a circular one has narrow gaps among each three pipes, which deteriorate the gross performance of heat transfer. But in the case of the present investigation which assumes acrylic pipes of the same wall thickness, the circular pipe bundle is advantageous to other ones as for the global performance of longitudinal heat transfer including the wall thermal conduction, because the area ratio of pipe walls, whose low thermal conductivity lowers the performance, is least when the pipes are circular.