Visual experimental study of droplet impinging on liquid film and analysis of droplet evolution characteristics
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Experimental and Computational Multiphase Flow
Visual experimental study of droplet impinging on liquid film and analysis of droplet evolution characteristics Wenxuan Ju, Yikai Wu, Shixin Lin, Fulong Zhao (), Sichao Tan College of Nuclear Science and Technology, Harbin Engineering University, Harbin 150001, China
Abstract
Keywords
The evolution characteristics of the droplets colliding with the wet wall surfaces are essential to the performance of the steam-water separator in the nuclear power plant. When the droplets
droplet collision
impact the liquid film with different velocities, the diverse phenomena will occur. The collision characteristics of droplets with the wall surface during the movement are experimentally
liquid film
secondary droplet steam-water separator
studied. In the experiment the high-speed camera with a shooting speed of 2000 frames per second is used to obtain the spread process of droplets hitting the liquid film vertically at
Article History
different velocities. The phenomena of the crown with and without splashing are analyzed. The critical parameters of phenomena are recorded, and the qualitative conditions generated by the
Received: 20 March 2020
three phenomena are analyzed. The critical velocity to generate the secondary droplet is 0.021
Accepted: 19 July 2020
m/s and the critical velocity to generate the main droplet is 0.017 m/s when a droplet with a diameter of 3.62 mm hits the liquid film. If the kinetic energy of falling droplets can be reduced,
Research Article
the waste caused by the Worthington jet and splashing droplets can be effectively reduced. The present study can lay basis for the design of the steam-water separator and the space droplet radiator.
1
Introduction
The droplet collision with wet wall surfaces is a common phenomenon in the nuclear power plant, for example, the collision of small droplets with wet wall surfaces in the steam-water separator (Li et al., 2007; Zhao et al., 2018) and with the droplet collector wall surface in the space radiation heat exchanger (Totani et al., 2002, 2005, 2006). Actually, the droplet colliding with a liquid film is a complicated process. The droplet velocities can greatly influence the collision performance, such as the spreading width, the crown characteristics with and without splashing. When the droplet velocity reaches a specific value, the secondary droplets can be generated surrounding the coronal fracture edge and the collision center. The secondary droplets can lead to the decrease of the equipment separation or collection efficiency or the efficacy loss. Therefore, it is vitally important to study the droplet collision characteristics with the liquid films, which can improve the efficiency of the space radiation heat exchanger and steam-water separator. However, there are few studies on the droplet collision with the liquid films, especially the thick liquid film (the [email protected]
Revised: 7 June 2020
© Tsinghua University Press 2020
thick liquid film is defined as 1.5 < σf < 4, σf = hf
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