斜槽管降膜吸收的数学模型及数值计算

HEAT AND MASS TRANSFER MODEL AND NUMERICAL RESULT OF FALLING FILM ABSORPTION OUTSIDE AN INCLINED LOW RIB TUBE

提出一种新的计算低肋斜槽管管外单管降膜吸收时的数学模型,即把肋片形状为等边三角形、肋片高度<0 5mm的斜槽管管外液膜看成是由两部分———内层和外层组成的。通过理论分析,得出了内层液膜内的速度、温度和浓度分布的解析解,外层用数值计算的方法求解,内层和外层之间采用二阶藕合法,使内、外层之间能光滑过渡。应用上述数学模型,研究了这种传热管管外液膜中的速度、温度和浓度分布,讨论了肋片高度和肋片倾角对传热传质性能的影响。通过计算值与实验值的比较发现二者吻合较好。

A mathematical model to evaluate falling film absorption effect outside an inclined low rib tube wasproposed. The liquid film outside the tube whose ribs' height is less than 0.5 mm is assumed to consist of two parts, i.e. internal and external layers. Using the theoretical analysis deduced the analytical solutions of the distribution of the velocity, temperature and concentration in the internal layer. The solutions of the external layer were obtained by using numerical method. A second-order coupling method was adopted to couple the results of the two layers. The overall velocity, temperature and concentration distribution of the film were investigated. The effects of the height and the angle of the ribs on the performances of the heat and mass transfer of the tube were discussed.