Constructal design of multiscale elliptic tubes in crossflow.

The optimal configuration of two‐scale elliptic tubes in crossflow is found on the basis of the constructal design. The larger tubes are installed inside a domain of fixed length and height. In the same domain, smaller tubes are inserted between the larger tubes in the entrance region at the mid leading edge to leading edge distance of the larger tubes. The spacing between the larger tubes, the semiminor axis of the larger tubes, the major axis of the smaller tubes, and the semiminor axis of the smaller tubes are varied inside the domain freely to find the optimal configuration. There are two optimal configurations: one without the smaller tubes and the other with the presence of the smaller tubes. Both the larger and the smaller tubes are heated at a constant surface temperature. The flow is induced by a fixed pressure difference. The equations for steady, laminar, two‐dimensional, and incompressible flow are solved by finite volume method. In the absence of the smaller tubes, the range of Bejan number (dimensionless pressure drop) is 103<Be<105, and in the presence of the smaller tubes, Bejan number is Be = 105. The range of the dimensionless larger tubes semiminor axis is 0.1 ≤ B ≤ 0.4. Air is used to cool the row of the tubes with Prandtl number equal to 0.7. The results show that for different semiminor axes of the larger tubes, the heat transfer rate is enhanced when the smaller tubes are placed between the larger tubes. [ABSTRACT FROM AUTHOR]