Experimental and Computational Study of Enhanced Forced Convection Heat Transfer in Novel Slotted Wavy-Plate-Fin Channels

Abstract

Forced convective enhanced heat transfer performance of airflows (50 ≤ Re ≤ 4000, Pr ∼ 0.71) in novel slotted sinusoidal wavy-plate-fins is investigated both experimentally and computationally. The slotted wavy fin core evaluated in the experiments was produced by direct metal laser sintering (DMLS). Compared with the equivalent or nonslotted wavy fin core, also produced by DMLS, while the heat transfer was found to be similar, the pressure drop was reduced by as much as 31%. This very attractively significant enhancement was further explored in a three-dimensional computational analysis. Besides validating experimental results, it is seen that a significant part of pressure loss in plain wavy-fin channels is due to form drag induced by flow recirculation in the trough region. This is shown to be reduced substantially if the fins are slotted at large form drag locations. Their position and size, characterized, respectively, by phase angle (β) and dimensionless slot size (δ), are varied in the simulations to explore their role in the enhanced thermal-hydrodynamic performance. One such modified design exhibits a characteristically unusual performance at low Re, where improvement in heat transfer (+17%) is accompanied by a reduction in pressure loss (–16.8%). Additionally, at high Re, though a slight decline in heat transfer (–7.6%) is evidenced, the pressure drop is nearly cut in half (–46.6%). Moreover, the overall thermal-hydrodynamic performance based on the metric of fixed heat transfer rate and pressure drop constraint shows that ∼15% reduction in the required heat transfer surface area can be achieved with slotted wavy fins.