水平异型管降膜蒸发器管外液膜流动数值模拟

Numerical Simulation of Liquid Film Flow outside Tube of Horizontal Shaped Tube Falling Film Evaporator

通过Fluent 6.3软件,模拟计算了5种换热管管型(圆管、扁管、椭圆管、滴形管和蛋形管)的降膜蒸发器的12排换热管管束管外成膜排数及液膜厚度。找到5种换热管管型中成膜效果最好的为蛋形管,针对蛋形管管束模拟了在蛋形管的管间距d=6.4 mm条件下,制冷剂入口流速v在0.10~0.20 m/s范围内时,蛋形管管外成膜排数及液膜厚度,以及在制冷剂入口流速v=0.15 m/s条件下,蛋形管的管间距d在6.4~12.4 mm范围内时,蛋形管管外成膜排数及液膜厚度,得到以下结论:在扁管、椭圆管、滴形管和蛋形管4种异型管中,蛋形管成膜的管排数最多。随着制冷剂入口流速的增大,蛋形管换热管外成膜的排数增大,液膜厚度也增加。蛋形管管束的管间距越大,蛋形管管外成膜的排数越少,液膜越薄。

The film formation row number and liquid film thickness outside the 12-row heat exchange tube bundles of the falling film evaporator with five heat exchange tube types(round tube,flat tube,elliptical tube,drop-shaped tube and egg-shaped tube)are simulated and calculated by Fluent 6.3 software.It is found that the best film formation effect of the five heat exchange tube types is the egg-shaped tube.For the egg-shaped tube bundle,the film formation row number and liquid film thickness outside the egg-shaped tube are simulated when the spacing d of the egg-shaped tubes is 6.4 mm,and the inlet flow velocity v of the refrigerant is in the range of 0.10 to 0.20 m/s as well as when the inlet flow velocity v of the refrigerant is 0.15 m/s,and the spacing d of the egg-shaped tubes is in the range of 6.4 to 12.4 mm.The conclusion is as follows:Among the four shaped tubes of flat tube,elliptical tube,drop-shaped tube and egg-shaped tube,the film formation row number of egg-shaped tube is the largest.As the inlet flow velocity of the refrigerant increases,the film formation row number of the eggshaped tube increases,and the liquid film thickness also increases.The larger the spacing of the egg-shaped tubes,the fewer the film formation row number of the egg-shaped tube,and the thinner the liquid film.