Influence of the presence of a “shelf” on the outer surface of the submerged nozzle and the electromagnetic effect within its length on the qualitative distribution of metal flows during continuous casting of steel

Continuous casting of steel has many ways to control the quality of the billets. The possibilities offered by electromagnetic stirring are far superior to physical eff ects, but combining these two quality control methods can be extremely effective. Research have shown the possibility of a qualitative effect on the flow of the liquid in the mold with implementation of electromagnetic stirring technology and the “skirt” is used in the form of a “shelf” on the nozzle, which is immersed in the mold. In addition, implementation of this shelf increase the possibilities of using direct-flow nozzles with the slope of the inner wall, where in each case it gives advantages, both with an expanding channel, and with a narrowing one. The design of the shelf also does not affect the implementation of electromagnetic stirring in the process of continuous casting, since it is below the level of the mold meniscus and above the level of the effect of the electromagnetic stirrer in the mold. The results of the research show that when using a “shelf” in the middle of the immersion nozzle depth, the casting process is accompanied by the control of most of the flows that are created when the jet enters into the mold and effect of EMS. It also affects the formation of vertex on the meniscus. And the implementation of a “shelf” at the outlet of the submersible nozzle completely changes the nature of the flow of the incoming jet.

NUMERICAL STUDY OF FLOW IN A PLANE SUDDENLY EXPANDING CHANNEL BASED ON TWO-LIQUID TURBULENCE MODEL AND WILCOKS MODEL

В статье представлены результаты численного исследования структуры течения в плоском канале в зоне его внезапного расширения. Расчеты выполнены на основе двухжидкостной модели турбулентности и модели турбулентности Уилкокса. Стационарное решение задачи получено методом установления, для чего использовались нестационарные уравнения гидродинамики. В работе исследованы поля скорости и турбулентные напряжения потока, а также коэффициент сопротивления в различных участках канала. Основные расчеты выполнены на равномерной сетке с числом узлов 300×90. Для разностной аппроксимации исходных уравнений применен метод контрольного объема второго порядка по пространству. Корректность результатов подтверждена для чисел Рейнольдса Re = 36000 путем сравнения с найденными в литературе экспериментальными данными.

Heat Transfer Improvement in a Double Backward-Facing Expanding Channel Using Different Working Fluids

This paper reports a numerical study on heat transfer improvement in a double backward-facing expanding channel using different convectional fluids. A finite volume method with the k-ε standard model is used to investigate the effects of step, Reynolds number and type of liquid on heat transfer enhancement. Three types of conventional fluids (water, ammonia liquid and ethylene glycol) with Reynolds numbers varying from 98.5 to 512 and three cases for different step heights at a constant heat flux (q = 2000 W/m2) are examined. The top wall of the passage and the bottom wall of the upstream section are adiabatic, while the walls of both the first and second steps downstream are heated. The results show that the local Nusselt number rises with the augmentation of the Reynolds number, and the critical effects are seen in the entrance area of the first and second steps. The maximum average Nusselt number, which represents the thermal performance, can be seen clearly in case 1 for EG in comparison to water and ammonia. Due to the expanding of the passage, separation flow is generated, which causes a rapid increment in the local skin friction coefficient, especially at the first and second steps of the downstream section for water, ammonia liquid and EG. The maximum skin friction coefficient is detected in case 1 for water with Re = 512. Trends of velocities for positions (X/H1 = 2.01, X/H2 = 2.51) at the first and second steps for all the studied cases with different types of convectional fluids are indicated in this paper. The presented findings also include the contour of velocity, which shows the recirculation zones at the first and second steps to demonstrate the improvement in the thermal performance.