A one-dimensional thermal-hydraulic analysis code was developed for the conceptual design and sizing of once-through steam generators (OTSGs) with application to small modular nuclear reactors. The OTSG in the model is represented by one characteristic double-tube heat exchanger with countercurrent flow. The secondary side of the OTSG is divided into subcooled liquid region, saturated two-phase mixture region, and superheated vapor region. Heat transfer and pressure drop correlations for each flow region were selected and implemented. To benchmark predictability of the developed computer code, the B&W OTSG whose design data is available in open literature was simulated. The results were compared both to the design data of the OTSG and to the analysis results obtained using a best-estimate thermal-hydraulic analysis code. The overall characteristics of the heat transfer area, pressure, and temperature distributions calculated with the developed code were in good agreement with the design data as well as the results from the best-estimate code. Lastly, a new concept of OTSG that incorporates feedwater circulation to reduce its volume for SMR application was simulated using the developed code. This demonstrates that the code can be used for design innovation and performance analysis of OTSGs.

为直流蒸汽发生器 (OTSG) 的概念设计和尺寸设计开发了一维热工水力分析代码，适用于小型模块化核反应堆。模型中的 OTSG 由一种具有逆流流动的特征双管换热器表示。OTSG 二次侧分为过冷液体区、饱和两相混合区和过热蒸汽区。为每个流动区域选择并实施传热和压降相关性。为了对开发的计算机代码的可预测性进行基准测试，模拟了 B&W OTSG，其设计数据在公开文献中可用。将结果与 OTSG 的设计数据和使用最佳估计热工水力分析代码获得的分析结果进行了比较。用开发的代码计算的传热面积、压力和温度分布的整体特性与设计数据以及最佳估计代码的结果非常吻合。最后，使用开发的代码模拟了 OTSG 的新概念，该概念包含给水循环以减少 SMR 应用的体积。这表明该代码可用于 OTSG 的设计创新和性能分析。