Experimental study and similarity analysis of separation efficiency of swirl-vane separator

Abstract

Swirl-vane separator in nuclear steam generator is used as primary separator for separating more than 80% of the water from the steam-water mixture to feed the qualified steam to dryers and turbines. Laboratory tests are generally performed to seek alternatives for separator design and performance improvement. Though great efficiency is often obtainable in the reduced model, the performance of the full-sized prototype is not well predicted due to the lack of proven similarity analysis. In our previous study, a theoretical model for critical droplet diameter, grade efficiency and overall separation efficiency has been established to predict separator performance (Liu and Bai, 2016). Based on the model, the aim of this paper is to study the separation performance of downscaled separator and to identify important differences between small-scale and large-scale separators. Experiments are carried out on a small-sized swirl-vane separator using air and water as working fluids. Firstly, the characteristics of gas-liquid separation process are visually observed using high-speed camera to understand the operating principle of the separator. After that, the separation efficiency is measured over a wide range of flow conditions, and the gas and liquid velocities influencing the separator performance is analyzed in detail. The experimental data are then used with previous theoretical model to predict the performance of two larger separator prototypes. When model separator has a same shape but reduced size as that of prototypes, and their working pressure and gas-liquid superficial velocities are the same, the results indicate that the model separator has a significantly greater separation efficiency than the prototypes. Generally, the larger scale the prototypical separator is, the lower value the separation efficiency becomes.