CONJUGATE HEAT-TRANSFER OF A FINNED TUBE .A. HEAT-TRANSFER BEHAVIOR AND OCCURRENCE OF HEAT-TRANSFER REVERSAL

The conjugate heat transfer in a high-performance finned-tube heat exc hanger element was calculated for three-dimensional thermally and hydr odynamically developing laminar flows. The influence of Reynolds numbe r Re and a fin efficiency parameter Fi (ratio of fin to fluid conducti vity times fin thickness to fin pitch) on the heat transfer behavior h as been studied. Flow patterns, pressure distribution, Nusselt number distribution, heat flux distribution, and fin efficiency are presented . The part of the fin upstream of the tube is much more efficient than the downstream part. A unique heat transfer phenomenon, a directional reversal of the heat transfer, occurred locally on the fin in the tub e wake for small Fi and large Re. This can be interpreted as three-dim ensional interaction of convection and the fin conduction in the tube wake, when the flow is dominated by a strong horseshoe vortex and a de ad water zone with recirculation.