Study on the effects of flow-driven rotational mixing vanes by flow pattern tracking

•Rotational mixing vane rotates with flow-driven force.•The mixing parameters represents the mixing effects.•Swirl generation and pressure drop decrease enhance the power uprate in reactor. In pressurized water reactor (PWR), spacer grid is installed to support the fuel rod bundles, located between the fuel rod bundles. The mixing vane is installed on top of the spacer grid to generate swirl and cross flow. The swirl and cross flow enhance the heat transfer and can promote a critical heat flux (CHF) in the PWR. The PWR safety margin can be estimated using the heat-transfer performance and the CHF. In this research, flow-driven rotational mixing vanes were installed. Fan, impeller, and wind-turbine mixing vanes were adopted, which could rotate without any artificial force. The fluid flow and rotational motion simultaneously influenced each other. The effects of the flow-driven rotational mixing vanes were presented as flow patterns. A flow-pattern tracking method demonstrated the effects of various mixing parameters. The rotational speed was validated using a high-speed camera experiment and a computational analysis using a general moving-object method. The lateral velocity reflected the cross-flow magnitude with respect to the axial velocity. The vorticity was considered as a performance measure for the rotational mixing vanes. The bubble behavior demonstrated the mixing effect of the fluid in the subchannel. The pressure drop was gauged to verify the flow blockage. Thus, using flow-pattern tracking, the mixing effect of the parameters can be used to quantify the power-uprate enhancement and the safety margin for a PWR.