Study on Single-Phase Flow and Heat Transfer Characteristics of Vertical Narrow Rectangular Channel Under Rolling Motion with Nonuniform Heating

Abstract Plate type fuel elements have wide application potential in the integrated reactors due to their high power-to-volume ratio, low core temperature, high burnup and compact structure arrangement. The flow channels between adjacent fuel element plates are small, showing typical narrow rectangular structures with large aspect ratio. Due to the influence of fuel self-shielding effect, irradiation in the reactor and component arrangement, the plate fuel element has obvious uneven heat release in the transverse direction. As a result, the thermal hydraulic characteristics in the flow channel may be different from those in the uniform heating and conventional channels. In this paper, a typical vertical narrow rectangular channel is selected as the research object, and the channel section is 65mm × 2.23mm. Based on the computational fluid dynamics method, the mathematical and physical model of flow and heat transfer is established, and refined numerical calculations are carried out. The research parameters are that the inlet temperature is 38°C, the outlet gauge pressure is 0MPa, the heat flux is 15–240kW/m2, and the Reynolds number is 1000–14000. The research results show that the effect of transverse non-uniform heating on the heat transfer characteristics is greater than that on the flow characteristics. And with the decrease of Reynolds number and the increase of heat flux, the influence of non-uniform heating is more significant. Subsequently, the flow heat transfer analysis under the rolling and pitching conditions of the ocean is carried out to analyze the influence of non-uniform heating. It is found that Nusselt number and friction coefficient are macroscopic consistent with vertical state under forced circulation ocean conditions. However, under the same rolling period and Angle, the secondary flow intensity in the rolling state is greater than that in the pitching state. In the rolling state, different nonuniform heating forms have obvious influence on the secondary flow, in which the linear distribution form has the highest secondary flow intensity.