Experimental and Numerical Research on Droplet Drag Coefficient and Deformation Coefficient in Nuclear Power Plants

There are many multiphase flow phenomena in steam generators (SG) of nuclear power plants (NPPs) and the movement of droplets affects the separation efficiency of dryers in SG. And the most important factor affecting droplet movement is drag force on droplet. Drag force coefficient (DRC) and deformation coefficient (DEC) as characterization coefficient of drag force have important research significance. In this paper, water and silicone oil are used as continuous phase and dispersed phase, respectively. Study on variation of the DRC when Re is in the range of 30–1200 is carried out. Firstly, the motion of droplets (MDs) of different sizes is visually studied by using the high-speed camera and images of MD is acquired. The droplet contour is recognized based on principle of boundary differentiation and the centroid coordinates of the droplet are determined, thus DRC and DEC are obtained. Besides, the relationship between DRC and DEC are researched. Additionally, Lattice Boltzmann Method (LBM) is used to simulate the droplet motion. The simulation results are compared with the experimental results, thus verifying the feasibility of LBM method to simulate the MD. The results show that when velocity of droplet (VD) is low, DRC is inversely proportional to VD. While VD is high, DRC is constant. When the droplet diameter (DD) is small, the final VD is proportional to DD, and when DD is large, the final VD is proportional to the square of DD. The DEC is linearly related to We. The larger the We, the smaller the DEC. Shan-Chen model of LBM is feasible for droplets with low Reynolds number (Re), while the simulation of droplets with high Re is the future prospect.