HEAT-TRANSFER ENHANCEMENT OF A FINNED OVAL TUBE WITH PUNCHED LONGITUDINAL VORTEX GENERATORS IN-LINE

To explore the interaction of the vortical flow generated by punched d elta-winglet pairs (DWPs) with in-line arrange ment and to explore the ir influence on the heat transfer enhancement (HTE) and onflow loss pe nalty (FLP) in a high performance finned oval tube (FOT) heat exchange r element, three-dimensional flow and conjugate heat transfer in an FO T were calculated for a thermally and hydrodynamically developing lami nar flow (Re = 300) by solving the Navier-Stokes and energy equations with a Finite-Volume Method in body-fitted grids. The conjugate heat t ransfer was realized by iterations of the energy equation in the flow field and the conduction equation in the fin; FOT with one to three in line DWPs (beta = 30 degrees, Lambda = 2, h = H) were investigated. Ve locity and temperature fields, vortex formation, local heat transfer d istributions and global results were presented. The LVs of the incomin g flow intensified the LVs downstream of the second and the third wing let. For Re = 300 and Fi = 500, the ratios of HTE to FLP (j/j(0))/(f/f (0)) were 1.04, 1.01 and 0.97 for an FOT with one, two and three DWPs in-line respectively. (C) 1998 Elsevier Science Ltd. All rights reserv ed.