The fluidic diode (FD) is simple, passive device designed to provide small flow resistance in forward flow direction and large flow resistance in reverse flow direction. It plays a key role for importing passive core cooling system in advanced reactors such as hybrid loop-pool type Sodium Fast Reactors (SFRs) and Fluoride-salt-cooled High-temperature Reactors (FHRs). In nuclear industry, the vortex-type fluidic diode, one of fluidic diode consist of a circular chamber and two cylindrical port are preferred among fluidic diode because of its simplicity, easy maintenance feature. The performance of vortex-type fluidic diode is expressed as diodicity (Di), and many studies have been conducted to enhance its diodicity after its first invention. In this study, the modified design for vortex-type fluidic diode is proposed using topology optimization technique to enhance the diodicity.
The topology optimization is one of optimization technique that finds out optimum material distribution in given domain. In this study, topology optimization is conducted for tangential port and chamber in 2-D domain and low-Reynolds laminar flow condition. Results with clear boundary and enhanced performance are selected as topology optimized design. Preliminary performance evaluation in 2-D geometry for this topology optimized design is conducted and 3-D part is designed based on 2-D geometry.
Experiment study is conducted to evaluate performance of 3-D topology optimized design. Pressure drop measurement and flow visualization experiment are conducted to topology optimized design and reference design. Stereolithography (SLA) 3-D printing technique is used to produce test sections and MIR-PIV technique is used to visualize flow inside the vortex-type fluidic diode. Velocity fields and pressure drop across vortex-type fluidic diode of each design are compared and it is found that reference design has better performance.
Flow characteristic study using 3-D CFD analysis is conducted to evaluate effect of design modification on pressure drop. CFD analysis is conducted by simulating experimental condition with laminar and turbulent flow model. Comparison between laminar flow model and turbulence model is made to select model which predicts experimental result more accurately. Variables obtained in CFD analysis such as flow field and total pressure are analyzed in detail. Based on this analysis result, contribution of each sub-part of vortex-type fluidic diode is evaluated.