FLOW INSTABILITY AND AUGMENTED HEAT-TRANSFER OF FIN ARRAYS

A two-dimensional numerical computation was carried out for an in-line type of fin array for a periodically changing unsteady flow regime, o r for the second laminar flow regime characterized by the self-sustain ed flow oscillation. Mechanisms of heat transfer augmentation due to t he Bow instability are discussed based on the obtained Bow and thermal fields. First, it is observed that the flow instability occurring in the wake of a fin leads to the accelerated recovery of the wake and re sults in the mitigation of the wake effect and that it is effective to enhance the heat transfer of the downstream fin. Secondly, positive v alues of ($) over bar ($) over bar nu theta are also produced near the fin surface. This is another mechanism to produce the fin surface hea t transfer enhancement. It is also found that the dissimilarity betwee n the momentum transfer and heat transfer is produced near the fin sur face. Non-zero values of -($) over bar ($) over bar mu nu take a sign to suppress the momentum transfer in spite of the favorable sign of ($ ) over bar ($) over bar nu theta for heat transfer enhancement. It is also pointed out that flow is destabilized in the wake but is stabiliz ed in the fin boundary layer.