An experimental investigation on pool entrainment under small air flowrate

The liquid entrainment is a ubiquitous phenomenon in nuclear engineering. In the scenario of SBLOCA, liquid entrainment plays an important role exacerbating liquid loss in the reactor vessel. Numerous research has been conducted on the mechanism of pool entrainment. Part of experiment data could be predicted well by Kataoka-Ishii entrainment correlation which has been widely used. However, most research focused on the pool entrainment is conducted under intermediate or high gas flowrate. The Kataoka-Ishii correlation cannot predict well when air flowrate is small. Therefore, an experimental investigation under small air flowrate is important to conduct. This paper demonstrates an experimental study of air-water pool entrainment with similar gas flux conditions of nuclear heating reactor developed by Tsinghua University. The test section is 2000 mm long and 300 mm in diameter, with transparent material for visualization. The range of air flow superficial velocity is 0.082-0.31 m/s. The two phase mixture level is measured by visualization and compared with drift flux model. The water entrainment rate is recorded by weightometer after entrainment liquid separation. An entrainment correlation is given based on this experiment. Small fountain flow and large bubble burst is the main contributor to entrainment rate under low air flowrate. Strong fountain flow and inclination of swelling level contribute more when air flowrate is comparably large. (author)