Experimental and numerical investigations on heat transfer and flow behavior of flow blockage in narrow rectangular channel with protrusions

Abstract

The safety analysis of flow blockage accident is significant for plate-type fuel reactor, especially swelling of cladding, which is resulted from irradiation damage in high burnup condition and needs to be paid more attention. In this study, experimental and numerical researches have been conducted to study the convective heat transfer and flow structure within narrow rectangular channel, where exists different numbers and arrangements of spherical crown protrusions. Compared with the experimental data of single protrusion condition, the overall heat transfer capacity even deteriorates more than 20% when protrusions are aligned in streamwise direction. In contrast, the global Nu is nearly 10% higher when three protrusions are located in spanwise direction. Conclusions can be drawn that existence of protrusion can also significantly change convective flow condition in narrow channel, and the laminar flow is altered to transitional/quasi-turbulent even though Re is only nearly 1600. Besides, the local information, such as flow boundary layer separation, low-speed recirculation and vortex evolution etc., can also be acquired by the Computational Fluid Dynamics (CFD) method comprehensively. Combined with experimental data and numerical results, the distinct heat transfer behaviors and flow structures for different flow blockage conditions can be explained in detail. In summary, conclusions about the flow and thermal processes influenced by protrusions in narrow rectangular channel are fundamental to safety analysis and design criteria of plate-type fuel assembly for flow blockage condition. Besides, it also can be applied in other industry scene during convective laminar flow within narrow rectangular channel.