The effect of rolling motion on flow resistance and heat transfer in narrow rectangular channel under natural circulation

Abstract

With the increase demand for energy for ocean development, small reactors with natural circulation as the normal operating conditions are increasingly becoming an important energy supply option. The complex marine environment, such as fluctuations in the flow rate of coolant in nuclear reactor due to wind and waves, affects the flow resistance and heat transfer characteristic of the coolant, threatening the safety of the reactor. The current study performs one-dimensional and three-dimensional code coupling method to analyze the effect on flow resistance and heat transfer in a narrow rectangular channel under rolling condition. In addition to the influence of flow pulsation which has been considered universally by past studies, it was found that transverse mixed convection caused by external force fields, and boundary layer acceleration caused by the ununiform distribution of cross-section pressure, also have an impact on flow resistance and heat transfer. Unlike the flow pulsation, which has no effect on the time-average flow resistance and heat transfer, the transverse mixed convection increases the time-average flow resistance while also enhances the time-averaged heat transfer. Boundary layer acceleration occurs at lower Reynold number (Re≈800), and results in a steep increase in flow resistance, while the effect on heat transfer is not so significant. The relative strength of the three effects is impacted by the rolling parameters maximum rolling angle θ0 and period t0. The flow pulsation effect increases with increasing θ0 and decreasing period, while the mixed convection effect increases with increasing θ0.