Numerical study on flow and heat transfer of a finned-tube heat exchanger with trapezoid vortex generators in CO_2 lasers

摘要

The high pressure loss and low heat transfer efficiency have been plaguing the development of high power fast-axial-flow CO_2 laser. In order to solve this problem, a special longitudinal vortex generator (LVG), which contains two modified right-angled trapezoid wings and interrupt gap(TMRTW), was proposed. The performance of a single trapezoid winglet(STW) and TMRTW was discussed. Numerical study reveals that compared with STW, the TMRTW has better flow and heat transfer characteristics under the same initialization conditions. Further parametric study indicates that the TMRTW generates vortex. The intensity of this vortex is mainly present in central area. The downstream extension of this vortex is better than that of STW. Especially for the developing of boundary layers, this is beneficial. Hence, the performance of heat transfer for TMRTW is enhanced obviously with Re less than 1200. Compared with STW, the heat transfer for TMRTW is enhanced by 16% under the optimized structure size, with the pressure penalty almost the same.