Numerical investigation of helium bubble rising behavior in cross-type channel

In a certain nuclear reactor, the coolant channel is a cross-type channel, there is little research about bubble rising behavior in this kind of channel, but the neutron detection would be affected by the bubbles. Through comparing with previous experiment, proper numerical model has been determined, then studied the cross-type channel under different helium flow rates with CFD software Fluent. Research shows that the bubble distribution exists some similarities under different helium flow rates, the bubbles tend to rise near the tube wall; In the axial direction of the flow channel, the bubble coalescence can be observed, which leads the section void fraction in the axial direction to increase first and then tends to be stable, and the section void fraction increases with increasing helium flow rates.