Investigation of Resistance Characteristics of Throttling Elements in Steam Generators for Fourth-Generation Advanced Nuclear Energy Systems: Experimental and CFD Analysis

T In fourth-generation advanced reactors, flow instability and oscillations within heat exchange tubes of steam generators can arise due to uneven flow distribution and other complex factors, posing risks to safe operation. Such instabilities may lead to fluid mixing, oscillations, and significant fluctuations, thereby increasing system complexity and unpredictability. Installing a throttling element at the inlet of the steam generator’s heat exchange tubes can effectively enhance the inlet resistance coefficient, mitigate the occur-rence of flow instabilities. Due to the complexity of throttling structures, re-search on their design for steam generators is limited. Traditional empirical methods for calculating resistance coefficients often yield considerable inac-curacies. This study presents a novel T-shaped orifice throttling element de-signed for steam generators in fourth-generation advanced nuclear energy systems. Through a combination of numerical simulations and experimental validation, various structural parameters of the T -shaped orifice throttling el-ement were developed and manufactured, allowing for the assessment of the resistance characteristics across a wide range of flow conditions. The results reveal that the resistance coefficient of the innovative $\mathbf{T}$-shaped throttling device can fit for different operational requirements in steam generators for fourthgeneration advanced nuclear energy systems. The resistance coeffi-cient shows significant sensitivity to both the aperture size of the $\mathbf{T}$-shaped orifice and the structural characteristics of the baffle. Furthermore, the re-sistance coefficients of throttling devices with varying structural parameters maintain relative stability across a range of Reynolds numbers. A mathemat-ical relationship was established to correlate multiple structural parameters and the resistance coefficient. This study establishes a foundation for the further investigation and development of practical designs and optimizations of throttling elements for fourth-generation advanced nuclear energy sys-tems.