Relative Performance of Some Novel Heat Transfer Augmentation Surfaces
Amit R. Amritkar and Danesh K. Taftia
Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
adtafti@vt.edu
ABSTRACT
A study of advanced heat transfer augmentation surfaces for compact heat exchangers using direct and large eddy simulations under a fully developed flow assumption is performed. Comparison based on performance evaluation criteria (PEC) is made between two dimensional (2D) and three dimensional (3D) geometries showing performance variation in the low Reynolds number (ReD_h) range of 100 to 2000, covering laminar and early turbulent flow regimes. The 3D geometries include Split Dimple and Teardrop Split Dimple fins which are novel heat transfer surfaces developed at the HPCFD lab in Virginia Tech. The split dimple geometries are interrupted surfaces with half dimple shaped 3D protrusions on them. The 2D geometries comprised of circular, modified louvers and offset strip fins. While the protruding split dimple geometries achieve earlier transition to turbulent flow regime over the louver type geometries giving higher augmentation, the pressure drop penalty is also higher. Two different PECs are used including a derived parameter based on pumping power. Simple interrupted surfaces based on off-set strip fins and louvered fins outperform most of the other surfaces in the low Reynolds number laminar regime (ReD_h < 500). On the other hand at higher Reynolds numbers in the transitional and fully turbulent regime (ReD_h > 1000), non-interrupted or continuous surfaces with 3D roughness elements show enhanced performance.
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