Pattern recognition algorithm for analysis of chugging direct contact condensation

Abstract

Direct contact condensation of steam bubbles in a boiling water reactor suppression pool has long been studied utilizing video recording of experiments. The use of video recording enables observation of the behaviour of the bubble surface area and can assist in validation of computational fluid dynamics models.

A direct contact condensation experiment of the suppression pool test facility PPOOLEX was recorded using high-speed cameras. The recorded video material was used for development of a pattern recognition and data analysis algorithm. 300 fps video of 48 s duration was cut into frames with a resolution of 768 px x 768 px. The side profile of the bubbles was identified and the volumes and surface areas of the bubbles were evaluated using a voxel-based method.

The purpose of the algorithm was to determine the shape and size of steam bubbles during their formation, expansion, collapse and re-formation. The most probabilistic chugging frequencies were estimated. The bubble geometry data were also used to determine the velocity and acceleration of the phase interface, as condensation induced Rayleigh-Taylor instability develops on the bubble surface during the bubble collapse, as the heavy phase accelerates towards the light phase. Knowledge of the critical wave length is necessary for mesh spacing in CFD calculations.

The algorithm appears to be promising. Some limitations exist and approximations need to be made due to the challenging video shooting conditions. The algorithm works well for cylindrical bubbles and provides important data on the dynamics of the phase interface necessary for numerical modelling of direct contact condensation.