A CFD analysis of the flow dynamics of a directly-operated safety relief valve

• Published in: Nuclear engineering and design Vol. 328; pp. 321 - 332
• Main Authors: Scuro, N.L., Angelo, E., Angelo, G., Andrade, D.A.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.03.2018; Elsevier BV
• Subjects: Air flow; CAD; Computational fluid dynamics; Computer aided design; Computer simulation; Diffusers; Discharge coefficient; Flow control; Fluid dynamics; Lifts; Mass flow; Mathematical models; Nuclear accidents & safety; Numerical analysis; Relief valves; Safety; Simulation; Steam; Valves
• ISSN: 0029-5493; 1872-759X
• DOI: 10.1016/j.nucengdes.2018.01.024

•Simulated disc forces are smaller than predicted by standard methods.•Complex flow dynamics at throat region.•Possible bowl-shaped shockwave. A three-dimensional numerical study on steady state was designed for a safety relief valve using several openings and inlet pressures. The ANSYS-CFX® commercial code was used as a CFD tool to obtain several properties using dry saturated steam revised by IAPWS-IF97. Mass flow and discharge coefficient calculated from simulations are compared to the ASME 2011a Section 1 standard. The model presented constant behavior for opening lifts smaller than 12 mm and is very reasonable when compared to the standard (ASME). In addition, the conventional procedure to design normal disc force assumes that all the fluid mechanical energy was converted into work; however, the CFD simulations showed that average normal disc force is about 19% lower than theoretical ASME force, which could prevent the valve oversizing. A numerical validation was conducted for a transonic air flow through a converging–diverging diffuser geometry to verify the solver's ability to capture the position and intensity of a shockwave: the results showed good agreement with the benchmark experiments.