Abstract:Marine integrated small reactors can experience swaying，undulating，and tilting conditions under ocean conditions. Analyzing the heat transfer characteristics of narrow rectangular core channels in marine conditions is of great significance for the safe operation of reactors. Three-dimensional CFD software is used to model a typical rectangular fuel assembly structure for ships. UDF is used to introduce rolling conditions and modify the heat transfer model. Compared with the original model，the modified model is better suited for ocean rolling conditions. Based on the analysis of parameters such as wall temperature，Nu number，void fraction，and synergy angle under given power distribution conditions，it is believed that due to the existence of narrow edges in the rectangular channel，corner temperature peaks form near the narrow edges on both sides of the rectangular channel wall under static conditions，and the corner peak on the same direction as the swing acceleration increases under swing conditions. In addition，increasing the swing angle or reducing the swing period can optimize the heat transfer inside the pipeline.