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Numerical Simulations on Heat Transfer Enhancement and Flow Resistance Characteristics of Oblique-cut Semi-elliptic Cylinder Shell

Author: GaoMeng
Tutor: ZhouGuoBing
School: North China Electric Power University (Beijing)
Course: Heating,Gas Supply, Ventilation and Air Conditioning Engineering
Keywords: Heat transfer enhancement Flow resistance Numerical Simulation Air Cooler Vortex generators Truncated semi - elliptic cylinder
CLC: TK124
Type: Master's thesis
Year: 2011
Downloads: 65
Quote: 0
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Abstract


Vortex generators is a passive heat transfer enhancement components, can be used for gas - or gas - steam heat exchanger air-side convection heat transfer enhancement, also can be effective in improving the air-side flow structure. On the basis of the existing experimental studies, numerical simulation analysis of the enhanced heat transfer and flow resistance characteristics of novel truncated semi-elliptic cylinder vortex generators, provide a useful reference for engineering applications. Single row one diagonal cut semi-elliptic cylinder, respectively arranged semi-elliptic cylinder of beveling beveling semicircular cylinders, rectangular winglets, trapezoidal winglet, triangular winglets vortex generators rectangular channel The numerical simulation of the air flow and convective heat transfer characteristics comparative. Beveling elliptic cylinder beveled angle α and further analysis, heat transfer and flow resistance characteristics of the parameters of its angle of attack β trailing edge height h, the front edge spacing s, from the entrance spacing S arrangement in a rectangular channel enhancement the impact. The numerical model as a reference to the experimental and numerical methods and the results of experiments and grid independent verification, to ensure the reliability of the simulation method and results. Heat transfer enhancement effect the vortex generators gap is less than 10% of the laminar flow state beveling better semi-elliptical cylinder and rectangular winglets, small rectangular wing in a turbulent state, two states beveled The semi-circular cylinder worst, beveling semi-elliptic cylinder heat transfer enhancement effect is slightly better than the oblique-cut semi-circular cylinder. Flow resistance characteristics, slope-intercept semi-elliptical cylinder in the higher Re number laminar flow and turbulent flow conditions flow loss was significantly lower than the other five kinds of vortex generators, the most turbulent conditions flow loss than rectangular winglets reduced by 22.45%. Integrated characteristic (j / jo) / (f / fo), the truncated semi-elliptic cylinder rather, in the laminar flow state with a small triangular wing slightly higher than the other vortex generator; while in the turbulent flow state is the best up comparable rectangular winglets increased by 21.88%. To sum up, the truncated semi-elliptic cylinder and flow resistance characteristics having a significant advantage. Laminar flow conditions beveled semi-elliptic cylinder parameters no significant impact on its consolidated properties; turbulent conditions a = 20 °, β = 15 °, h = 5 mm, S = 100 mm, s = 30 mm, the divergent arrangement (the leading edge of the low edge, concave relative) diagonal cut semi-elliptic cylinder features. Slope-intercept simulated air cooler in the air-conditioned semi-elliptic cylinder strengthen the heat transfer and flow resistance characteristics, taking into account the air conditioning air cooler air side conditions usually laminar flow simulation conditions set to laminar flow, with triangular winglets for comparison. The results show that the two kinds of vortex generator heat transfer enhancement effect is almost the same; oblique-cut semi-elliptic cylinder flow resistance below the triangular winglets, higher Re number, the two kinds of vortex generators on Staggered tube air cooler has less blocking effect, beveling semi-elliptical cylinder can drag reduction up to 6.40%, triangular winglets maximum drag reduction of 4.39%; addition to a small number of low-Re number Shun emptying cooler conditions, oblique-cut semi-elliptic cylinder characteristics are excellent triangle winglets; higher Re number two kinds of vortex generators may significantly improve air cooler features, it is recommended that the air cooler arrangement of vortex generators run at higher Re number.

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CLC: > Industrial Technology > Energy and Power Engineering > Thermal engineering, heat > Thermal Engineering Theory > Heat Transfer
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