管断面形状が軸方向熱輸送特性に及ぼす影響 The Effect of the Shape of the Pipe Section on the Longitudinal Heat Transfer Characteristics
In search of the relation between shape and performance, the effect of the pipe section on the heat transfer has been investigated. Longitudinal heat transfer between two fluid reservoirs of different temperatures is highly enhanced by fluid pulsation in capillary pipes which connect the reservoirs. When the pulsation frequency is sufficiently large, a boundary layer is formed along the pipe walls. The lateral heat transfer between the core and the boundary layer enhances the longitudinal heat transfer. It is interesting to investigate the effect of the shape of the pipe section which affects the boundary layer on the heat transfer. Regular polygons of the same area are considered as the pipe sections; triangle, square, pentagon and hexagon. The enhancement of heat transfer was more prominent with polygons of fewer edges under the same condition concerning the rest parameters which affected the heat transfer characteristics. A polygon of fewer edges has a longer wetted perimeter which causes a wider boundary layer region resulting in a more enhanced heat transfer. On the other hand, a longer wetted perimeter requires more power to maintain the fluid pulsation. Therefore, when the power was taken into consideration, a polygon with more edges was more power efficient to enhance the heat transfer and a circle was most efficient.
図学研究 (72), 3-7, 1996-06-01