الفهرس 
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Abstract
Heat transfer is the most common phenomenon in many practical applications in energy conversion, transmission, and utilization.
Many studies indicated that the effects of tubes shapes and their arrangements
have a great influence on heat transfer process. Most of them have been carried out on circular and elliptical tubes. But the available data on forced convection for wing-shaped tubes are too scarce. Therefore, in the present study the flow characteristics and thermal performance criteria of staggered wing-shaped tubes bundle in cross-flow are, numerically and experimentally, investigated for different angles of attack. In the experimental part, the experiments are conducted in an open- suction-wind tunnel with a 305 mm x 305 mm x 780 mm test section. The studied
bundle consists, mainly, of 22 copper wing-shaped tubes distributed through three successive rows in staggered arrangement. The wing-shaped tubes are formed from circular ones with tube equivalent diameters (Deq) of 22.5 mm. The longitudinal (Sd and transverse (ST) tube-pitches of 37 mm are kept constant. Hot air is forced
to flow over the external surface of the tubes and exchange heat with the cold water flowing inside tubes. The air flow Rea is varied from 1.8x103 to 9.7xl03 while the
cold water Re; is kept at 5 x 102. The possibility of air water vapor condensation on the outer tubes surfaces are avoided by keeping their temperature higher than that of
the flowing air D.P.T. Various flow angles of attack, in addition to a.k.a cone angle ( ~=90 0) are considered.
In the numerical part, the commercial CFD software FLUENT 6.3.26 is utilized
to predict the flow and thermal field around the wing-shaped tubes bundle. The flow is considered to be two dimensional, steady, viscous, and turbulent. The turbulence is modeled using the RNG k-s model. The enhanced wall treatment approach in the
near-wall region is used with the turbulence model. Comparison between the
experimental and numerical results of the present study and those, previously, obtained for similar available studies showed good agreements.