Longitudinal heat transfer in oscillatory flows in pipe bundles of variouscross sections

The effect of the sectional shape of pipes on the enhancement of longitudin al 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 t he existence of a region where heal is transferred toward the higher temper ature end when the pulsation frequency is sufficiently high. As a pipe bund le, only a circular one has narrow gaps among each three pipes, which deter iorate the gross performance of heat transfer. But in the case of the prese nt investigation which assumes acrylic pipes of the same wall thickness, th e circular pipe bundle is advantageous to other ones as for the global perf ormance of longitudinal heat transfer including the wall thermal conduction , because the area ratio of pipe walls, whose low thermal conductivity lowe rs the performance, is least when the pipes are circular.