Hydrodynamic characterization of bubbles in a water pool using the scrubbing nozzle and empirical model for prediction of bubble sizes

Abstract

A correlation model for the prediction of bubble size in a pool using a venturi scrubber is proposed. The proposed model was developed based on the experimental results on the behavior of bubbles generated according to the flow change of the gas injected into the pool with a venturi scrubber. This was used as basic information for estimating the decontamination factors(DFs) of pool scrubbing. The proposed model improved the prediction performance of DFs compared with the results of experiments under high Weber number and Reynolds number conditions. In the experiment, the bubble behavior with gas injection into the pool through a venturi scrubber was measured using a wire-mesh sensor. The bubble size data in the pool were compared with the predictions of previous bubble size models. It was confirmed that previous models overestimated the bubble sizes compared with the experimental data. Therefore, a bubble size prediction model was developed based on the experimental data when considering a nozzle with a large diameter. To validate the proposed model, comparative evaluations were performed with the scrubbing performance experiments of Korean CFVS. Because experimental data reflected both the decontamination effect of the venturi scrubber and pool, both venturi scrubbing and pool scrubbing were evaluated. For venturi scrubbing, DFs were calculated based on the droplet size prediction model in the venturi scrubber using Lee’s model. For pool scrubbing, the DFs were calculated by applying the bubble size prediction model in the BUSCA code. Finally, the comprehensive scrubbings were calculated by the product of the venturi scrubbings and the pool scrubbings DFs. In the pool scrubbing calculation, the model provided by the BUSCA code and EPRI model were compared with the bubble prediction model proposed in this study. Overall, the DFs reflected in the proposed model showed an average of 55% or more superior prediction performance compared to other models when compared with the experimental data. It considers the effect of venturi scrubbing in the prediction of pool scrubbing performance.