Heat transfer enhancement of finned oval tubes with staggered punched longitudinal vortex generators Chen, Y; Fiebig, M; Mitra, N K [Ruhr-Universitaet Bochum (Germany). Inst. fuer Thermo- und Fluiddynamik] 42 ENGINEERING; HEAT TRANSFER; FINS; TUBES; HEAT EXCHANGERS; LAMINAR FLOW; VORTICES; NAVIER-STOKES EQUATIONS Punched longitudinal vortex generators in form of winglets in staggered arrangements were employed to enhance heat transfers in high performance finned oval tube heat exchanger elements. Three-dimensional hydrodynamically and thermally developing laminar flow (Re = 300) and conjugate heat transfer in finned oval tubes were calculated by solving the Navier-Stokes and energy equations with a finite-volume method in curvilinear grids. Velocity field, pressure distribution, vortex formation, temperature fields, local heat transfer distributions and global results for finned oval tubes with two to four staggered winglets ({beta}= 30{sup o}, {lambda} = 2, h =H) were presented and compared. Winglets in staggered arrangement bring larger heat transfer enhancement than in in-line arrangement since the longitudinal vortices from the former arrangement influence a larger area and intensify the fluid motion normal to the flow direction. For Re = 300 and Fi = 500, the ratios of heat transfer enhancement to flow loss penalty (j/j{sub 0})/( f/f{sub 0}) were 1.151 and 1.097 for a finned oval tube with two and four staggered winglets, respectively. (author) United Kingdom 2000-02-01 English Journal Article Journal Name: International Journal of Heat and Mass Transfer; Journal Volume: 43; Journal Issue: 3; Other Information: PBD: Feb 2000 Medium: X; Size: page(s) 417-435 https://doi.org/10.1016/S0017-9310(99)00157-X [] 3 43 Journal ID: ISSN 0017-9310; IJHMAK; TRN: GB0121504 GB 2010-12-30 20225251