Falling liquid film periodical fluctuation over a superhydrophilic horizontal tube at low spray density. (February 2020)

• Record Type: Journal Article
• Authors: Zheng, Yi; Chen, Guoxin; Zhao, Xiangdi; Sun, Wanfu; Ma, Xuehu
• Is Part Of: International journal of heat and mass transfer. Volume 147(2020)
• Publication Date: 2020-02
• Subjects: Falling liquid film -- Spreading evolution -- Wave fluctuation -- Superhydrophilic tube -- Low spray density; Heat -- Transmission -- Periodicals; Mass transfer -- Periodicals; Chaleur -- Transmission -- Périodiques; Transfert de masse -- Périodiques; Electronic journals; 621.4022
• DOI: 10.1016/j.ijheatmasstransfer.2019.118938
• Languages: English
• ISSNs: 0017-9310

Abstract

Highlights: The liquid film spreading width for the superhydrophilic tube is two times higher than that of plain surface and little relevance to spray density. The increment of flow rate leads to the increase in frequency of the impacting droplet instead of droplet volume. The periodic behavior of liquid film fluctuation in droplet mode was observed. Abstract: Falling film on horizontal tube banks is widely used in heat transfer exchangers and absorbers due to its high heat and mass transfer performance. The superhydrophilic surface can effectively ameliorate the wettability of the tube wall and maintain thin film even at a very low spray density. Both of them play the dominating role in heat and mass transfer process. In this paper, a thermal tracing method was employed to investigate the liquid spreading feature and film fluctuation characteristics over a horizontal superhydrophilic tube. The results showed that the liquid film spreading width for the superhydrophilic tube was two times higher than that of the plain surface. Interestingly, as the liquid film extended continuously along the tube surface, the spreading width exhibited little relevance to the spray density under the current experimental condition for the superhydrophilic tube. Furthermore, in the case of droplet mode, the increment of flow rate leaded to an increase in the frequency of the impacting droplet instead of the droplet volume. Finally, the periodic behavior of liquid film fluctuation in droplet mode was observed as well, which demonstrated higher fluctuation intensity than that of other flow modes. The superhydrophilic-aided drop mode is of value in exploring the efficient, precise, and feasible technique for falling liquid film on a horizontal tube especially for ultralow spray density.