Marangoni凝结形态的影响因素  

Affecting factors of Marangoni condensation mode

作　　者：胡申华[1,2] 严俊杰[2] 王进仕[2] 

机构地区：[1]新疆大学电气工程学院热能动力系,新疆乌鲁木齐830047 [2]西安交通大学动力工程与多相流国家重点实验室,陕西西安710049

出　　处：《化工学报》2011年第11期3053-3059,共7页CIESC Journal

基　　金：国家自然科学基金项目(50966003);新疆大学博士启动基金项目(BS090147)~~

摘　　要：用实验方法研究了宏观温度场对一定浓度范围内的水-酒精蒸气混合物的Marangoni凝结的影响。根据拍摄记录的图片,观察到了膜状、珠状、珠状带块状、波动条纹状、溪状和珠状带溪状6种凝结形态。发现并非所有的凝结形态都出现在每个工况中,而且有些凝结状态之间并没有严格的界限。凝结形态随过冷度、浓度、流速、压力和表面温差的不同会发生变化,尤其是过冷度和浓度对凝结形态的影响最大。凝结形态与其对应的凝结表面传热系数有紧密的联系:在相同的实验条件下,当凝结表面传热系数出现峰值时,其对应的凝结形态均为珠状凝结。当凝结表面传热系数较低时,其对应的凝结形态为膜状凝结或较大液块凝结。最后对平块和斜块的Marangoni凝结形态进行了对比分析:可以看出斜块凝结面上液珠比较混乱,凝结形态不能简单地归结为珠状、条状、环状、平膜状和带起伏的膜状中的一种,一般是各种凝结形态都有一部分,或者说居于各凝结形态的中间过渡态。The effect of macroscopic temperature gradient on Marangoni condensation of ethanol-water vapor mixture was investigated experimentally in a wide range of concentration （0--50%） at different velocities （2, 4, and 6 m . s- 1） and pressures （31.2, 47.4, and 84.5 kPa） with shot condensation modes. An oblique copper block was employed to create surface temperature gradient. Six condensation modes were observed in the experiments, which are smooth film, bulk-drop, drop-streak, drop, wavy- drop and streak. Not every condensation mode appeared in each process and some condensation behavior was not distinct. For low condensation （0.5% and 1%） and high condensation （50%） smooth film was observed under the condition of large vapor-to-surface temperature difference. Drop mode occurred easily at high concentration （〉20%） while bulk-drop was a regular condensation mode at the concentration of 0.5%, 1% and 2%. Drop-streak and streak could occur almost at all concentrations with low vapor-to- surface temperature difference （〈3 K）. In the wide range of vapor-to-surface temperature difference, bulk-drop was a principal condensation mode. Condensation modes could vary with some factors, such as vapor-to-surface temperature difference, ethanol mass fraction, vapor velocity, and vapor pressure, especially the former two. The heat transfer coefficients depended on the condensation behavior. In general, for low ethanol concentration （0.5% and 1%）, the heat transfer coefficients could keep a large value over a relative wide range of vapor-to-surface temperature difference. The maximal heat transfer coefficients corresponded to the dropwise condensation mode and small heat transfer coefficients to the filmwise or rivulet modes. In addition, the condensate drops became smaller and denser with the increase of vapor pressure or velocity. The effect of vapor pressure on condensation behavior was less than that of vapor velocity. Meanwhile, the movement of drop or streak biasing from left to right could be

关 键 词：水-酒精混合蒸气 MARANGONI凝结 凝结形态 传热系数 

分 类 号：TK121[动力工程及工程热物理—工程热物理]