The collision dynamics between two droplets plays an important role in various disciplines of nature and practical interests. For example, during the process of fuel coolant interaction in nuclear reactor severe accident, the collision dynamics is responsible for the interfacial area evolution and then has significant effects on the heat transfer between the melt and coolant. Several distinct collision regimes have been identified in the configuration of liquid drops in the environment of gas at low and moderate Weber numbers, e.g. the bouncing, coalescence, separation after temporary coalescence, and spatter (also called ‘shattering’ and ‘splashing’). However, the collision of melt drops in coolant is in the configuration of liquid with liquid and the Weber number is sufficiently high, which may lead to different collision behavior. The purpose of this study is to investigate the collision behavior of melt drops during fuel-coolant interaction.

The collision of binary equal-sized droplets has been simulated in 3D by using the volume of fluid (VOF) and adaptive mesh refinement method. To validate the numerical methods, the simulations of tetradecane droplet collision were carried out in regimes of coalescence, reflexive separation, and stretching separation. The results showed good agreement with the experiments. Furthermore, the simulations of uranium dioxide (UO~2~) droplet collision in coolant were carried out. The results showed that the contact area between droplets and coolant increased with time first and then decreased. With the increment of Weber number, the maximum contact area in the droplet collision increased. As the increment of contact area between melt and coolant, the droplet kinetic energy transformed into surface free energy. When the thickness of lamella reached a certain critical value, rupture occurred and many little droplets generated. The number of little droplets increased with the increment of Weber number. In addition, the size distribution of little droplets was investigated.


Numerical Study of Collision Behavior of Melt Drops During Fuel-Coolant Interaction

Division / Sponsors: 
Power Division & Nuclear Engineering Division (NED)

Power Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/POWER/POWER2020/volume/83747

International Conference on Nuclear Engineering
Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE2020/volume/83761

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