Experimental study of small scale siphon breaker to verify Siphon Breaker Simulation Program (SBSP)

This study was conducted with the design of a small scale siphon breaker using the Siphon Breaker Simulation Program (SBSP). The feasibility of SBSP was researched in a small scale experimental facility. C factor, Chisholm B coefficient, and simulation results of the Undershooting Height (UH) were obtained by the SBSP. The major parts of the experimental facility are an upper tank, a lower tank, a downcomer, and a Siphon Breaker Line (SBL). The experiment variables are LOCA sizes of 30 and 38 mm and SBL sizes of 2/8, 3/8, and 4/8 in. The overall analysis of the air sweep-out mode was conducted by observing the differential pressure, flow patterns in the downcomer, and the UH. In addition, the reasons for the deviation of the UH prediction were analyzed in terms of the C factor-Chisholm B coefficient relation. We observed partial and zero sweep-out modes from the experimental results with SBL 3/8 and 4/8 in. In these experiments, the UH prediction results by the SBSP showed an average error of approximately 16 mm, which deviates by 2.5% compared with the height of the upper tank. Therefore, the SBSP predicts the experimental results well. Contrarily, full, partial and zero sweep-out modes were observed for the SBL 2/8 in. experiment. The UH for this experiment was predicted with a maximum error of approximately 48%. Consequently, the experimental results fairly agree with the SBSP model predictions for C factor range of 100,000-420,000. However, the disagreement becomes larger as the C factor increases and since the UH is too big in a high C factor range, in which full sweep-out mode occurs, the high C factor range (over 420,000) should be avoided during the siphon breaker designing stage. Finally, the SBSP could be considered as a reasonable simulation software for designing various scale siphon breakers.