基于冯-卡门类比建立螺纹管内颗粒污垢模型

 研究了5根内径为15.54 mm的铜质内置螺纹管的污垢数据,并给出了在雷诺数为16 000,污垢质量浓度为1 300 g/m3下的加速颗粒结垢实验数据.螺纹的几何参数采用目前应用于冷凝器的商用强化管中较为典型的一组几何参数：螺纹数为10～45、螺纹角为25°～45°、螺纹高为0.33～0.55 mm；实验用的氧化铝颗粒平均直径为3 μm.通过冯 卡门类比计算质量传递系数,壁面剪切应力则由压降数据来获得.据此,建立了一个半理论化的模型,讨论并得到了污垢热阻比与螺纹管几何参数、效率指数的一系列关系式,这些关系式以及对污垢的理论分析方法可应用于预测冷却水系统中螺纹管的污垢形成.

Modeling particulate fouling in internal helical-rib tubes by Von-Karman analogy

The accelerated particulate fouling data were provided in five 15.54 mm I.D. copper, helically ribbed tubes taken at the condition of Re=16 000 and 1 300 g/m3 concentration. The geometries of the helical rib tubes provide a class of internal enhancement that is typical of commercially enhanced tubes presently used in water chillers, and the ranges of geometric parameters are number of rib starts (10 to 45), helix angle (25° to 45°), and helix height (0.33 to 0.55 mm). Aluminum oxide particles with 3.0 μm average particle diameter were used as foulant in the experiment. The mass transfer coefficient was obtained by using the Von Karman analogy and the wall shear stress was obtained from pressure drop data. Based on the above two approaches, a semi theoretical model was developed to investigate the effects of geometric parameters and efficient indexes on the fouling characteristics in the enhanced heat transfer tubes. The correlations and the analyses can be used directly to assess the fouling potential of helically rib in cooling water systems.