Investigation on flow and breakdown characteristics of water film on vertical corrugated plate wall

Steam and water separation effect in the corrugated plate dryer plays a decisive role in the economic indicators of nuclear power plants. Investigation on flow characteristics of water film on vertical corrugated plate wall is beneficial to the research of steam-water separation mechanism and also plays an important role in the analysis of the water film flow characteristics and instability. In this paper, the water film thickness is measured by Planar Laser Induced Fluorescence (PLIF) technique. The relationship between the free falling water film thickness and time and the relationship between the average water film thickness and the water film Reynolds number are obtained, respectively. With probability density function (PDF), power spectral density (PSD) and wavelet analysis methods, the flow fluctuation instability of water film on the corrugated plate wall is analyzed. Characteristic frequency and vibration amplitude of water film flow fluctuation are obtained and the relationship between the water film thickness and the Reynolds number is fitted. Results reveal that the water film thickness has a certain regularity with the change of the Reynolds number and the two have a positive correlation. As the Reynolds number increases, the generation of solitary waves increases the water film volatility. The water film thickness is multi-frequency and has no obvious periodicity. When the water film Reynolds number in the experiment is less than 4055 and the flow is in a certain range of flow resistance, the water film breakdown will not happen owing to its own gravity. It indicates that the gravity have little influence on phenomenon of breakdown of a water film with a stable flow in a vertical corrugated plate. Therefore, the force which the water film is subjected to at the corrugated plate corner is analyzed. The model is established and the theoretical equation of the critical airflow velocity of water film breakdown and the water film thickness is derived as well. (C) 2018 Elsevier Ltd. All rights reserved.