Industrial Direct Chill Slab Caster of Tin Bronze (C903) Using a Porous Filter in the Hot-Top

2017 ◽  
Vol 10 (2) ◽  
Author(s):  
Mainul Hasan ◽  
Latifa Begum
Keyword(s):  
Contact Region ◽  
Convective Heat Transfer Coefficient ◽  
Direct Chill ◽  
Cfd Modeling ◽  
Mushy Region ◽  
Slab Caster ◽  
Entire Cross Section ◽  
Porous Filter ◽  
Hot Top ◽  
Tin Bronze

A 3D computational fluid dynamics (CFD) modeling study has been carried out for the tin bronze (C903) slab of industrial size in a vertical direct chill caster. The melt is delivered from the top across the entire cross section of the caster. An insulated hot-top is considered above the 80-mm mold to control the melt level in the mold. A porous filter is considered in the hot-top region of the mold to arrest the incoming inclusions and homogenize the flow into the mold. The melt flow through the porous filter is modeled on the basis of the Brinkmann–Forchheimer-extended non-Darcy model. Results are obtained for four casting speeds varying from 40 to 100 mm/min. The metal–mold contact region, as well as the convective heat transfer coefficient at the mold wall, is also varied. In addition to the above, the Darcy number for the porous media is also changed. All parametric studies are performed for a fixed inlet melt superheat of 62 °C. The results are presented pictorially in the form of temperature and velocity fields. The sump depth, mushy region thickness, solid shell thickness (ST) at the exit of the mold, and axial temperature profiles are also presented and correlated with the casting speed through regression analysis.

Numerical Study of a Direct Chill Slab Caster Fitted With a Porous Filter for Aluminum Alloy AA-2024

2014 ◽  
Author(s):  
Mainul Hasan
Keyword(s):  
Heat Transfer ◽  
Aluminum Alloy ◽  
Casting Process ◽  
Direct Chill ◽  
Mushy Region ◽  
Metal Mold ◽  
Melt Flow ◽  
Slab Caster ◽  
Porous Filter ◽  
Aa 2024

The present study is undertaken to model an industrial-sized vertical Direct Chill (DC) slab caster fitted with a porous filter near the melt entry region. The modeled alloy is a high strength aluminum alloy AA-2024 which is extensively used by the aerospace industry. The model has incorporated the 3-D turbulent aspect of the melt flow and heat transfer in the liquid sump and the mushy region solidification aspect of this long solidification range (136° C) alloy. The verified 3-D turbulent CFD in-house code is used to study the effects of various parameters of this casting process in order to gain some fundamental understanding of the melt flow and solidification behavior of the process. The studied caster consists of a popular ‘hot-top’ mold fitted with a porous filter above which molten aluminum alloy is delivered with a constant flow-rate across the entire hot-top. Because of two-fold symmetry, a quarter of the domain of the caster is modeled to save computational costs and time. A staggered control volume based finite-difference scheme is used to solve the non-dimensional modeled equations and the associated boundary conditions. The turbulent aspect of the flow in the porous filter is modeled using the latest suggested version of the Brinkman-Forcheimer extended form of Darcy equation for a porous media. The turbulent melt flow and solidification heat transfer in the clear fluid region are modeled using a low Reynolds number version of the k–ε eddy viscosity model. Computed results for the steady-state phase of the casting process are presented for four casting speeds, varying from 100 to 220 mm/min, for three metal-mold contact regions, varying from 20 to 50 mm and for three metal-mold convective heat transfer boundary conditions, varying from 1.0 to 4.0 kW/m2K and all for a fixed inlet melt superheat of 64° C. The permeability of the filter is also varied to ascertain its influence on the predicted results. Computed results of the velocity and temperature profiles, the sump depth and mushy region at the centre of the caster as well as the solidification shell thickness at the exit of the mold are provided and discussed. The present work can provide some useful guidelines in designing and optimizing a vertical DC slab caster for producing good quality casts for the common aluminum alloy AA-2024.

Effects of the Low Frequency Electromagnetic Field on the Centerline Macrosegregation of 7075 Aluminum Ingots

2011 ◽  
Vol 295-297 ◽  
pp. 1705-1708
Author(s):  
Dan Dan Chen ◽  
Hai Tao Zhang ◽  
Xiang Jie Wang ◽  
Jian Zhong Cui
Keyword(s):  
Electromagnetic Field ◽  
Steady State ◽  
Mushy Zone ◽  
Transition Region ◽  
Low Frequency ◽  
Casting Process ◽  
Direct Chill ◽  
Mushy Region ◽  
Chill Casting ◽  
Temperature Contour

The effects of the low frequency electromagnetic field on the macrosegregation of the 7075 aluminum ingots were investigated. The 7075 aluminum ingots with the diameter of 200 mm were prepared by the conventional direct chill casting and the low frequency electromagnetic field casting (LFEC) processes, respectively. The temperature during casting at steady state was measured, and the mushy region was observed from the temperature contour. The concentrations of the alloying elements were measured by the spectrograph. It was found that the transition region was broadened, but the mushy zone became narrower with presence of the low frequency electromagnetic field. The centerline macrosegregation of the ingots was alleviated by the low frequency electromagnetic casting process.

Heat Transfer of Polymer Particles in Gas-Phase Polymerization Reactors

2008 ◽  
Vol 6 (1) ◽  
Author(s):  
Yaghoub Behjat ◽  
Mohammad Ali Dehnavi ◽  
Shahrokh Shahhosseini ◽  
Seyed Hassan Hashemabadi
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Gas Phase ◽  
Transfer Rate ◽  
Fluid Dynamic ◽  
Convective Heat Transfer Coefficient ◽  
Particle Surface ◽  
Cfd Modeling ◽  
Polymerization Reactor ◽  
Gas Phase Polymerization

In this paper the effects of particles configuration and particles distance on the heat transfer rate in a gas phase olefin polymerization reactor have been studied using the computational fluid dynamic (CFD) modeling approach. The goal was to determine the causes of particle overheating in this reactor. It has been shown that classic correlations such as Ranz-Marshall are sufficiently adequate when far away particles with no interactions are to be modeled. However, when particles are sufficiently close to having interactions, these correlations fail to satisfactorily predict the convective heat transfer coefficient. The results indicate an increase in particle distance leads to an increase in the Nusselt number on the particle surface. Therefore, for particles with a large distance and triangular or rotated square configurations, the local Nusselt number is closer to the Nusselt number for a single particle.

A Comparison Between 3-D Thermal Model and 3-D CFD Model for Vertical DC Casting of Rolling Ingots of Aluminum Alloy 7050

2014 ◽  
Author(s):  
Mainul Hasan ◽  
Latifa Begum
Keyword(s):  
Heat Transfer ◽  
Aluminum Alloy ◽  
Thermal Model ◽  
Casting Process ◽  
Direct Chill ◽  
Turbulent Heat Transfer ◽  
Mushy Region ◽  
Turbulent Heat ◽  
Cfd Model ◽  
Dc Casting

In this study, first a 3-D thermal model is developed for an open top, vertical direct chill (DC) casting process of rolling slabs (ingots) by taking into account the casting speed in the form of slag flow in the thermal connective-diffusion equation. The mushy region solidification characteristics of the process are accounted for through the implementation of the enthalpy porosity technique. The thermal model is later extended to a 3-D CFD model to account for the coupled turbulent heat transfer and solidification aspect of the process. Both models simulate an industrial-sized, hot-top type vertical Direct Chill (DC) slab caster for high strength aluminum alloy AA-7050. A staggered control volume based finite-difference scheme is used to solve the modeled equations and the associated boundary conditions. In the CFD model, the turbulent aspects of flow and solidification heat transfer are modeled using a low Reynolds number version of the k–ε eddy viscosity approach. Computed results for the steady-state phase of the casting process are presented for four casting speeds varying from 60 to 180 mm/min for a fixed inlet melt superheat of 32°C. Simulation results of the velocity and temperature fields and heat fluxes along the caster surface are presented for the CFD model and the shell thickness and sump depth are compared between the CFD and thermal models.

scholarly journals A Novel Catalytic Micro-Combustor Inspired by the Nasal Geometry of Reindeer: CFD Modeling and Simulation

Catalysts ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 606
Author(s):  
Valeria Di Sarli ◽  
Marco Trofa ◽  
Almerinda Di Benedetto
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Residence Time ◽  
Convective Heat Transfer Coefficient ◽  
Three Dimensional ◽  
Cfd Modeling ◽  
Ansys Fluent ◽  
Commercial Code ◽  
Micro Combustor

A three-dimensional CFD model of a novel configuration of catalytic micro-combustor inspired by the nasal geometry of reindeer was developed using the commercial code ANSYS Fluent 19.0. The thermal behavior of this nature-inspired (NI) configuration was investigated through simulations of lean propane/air combustion performed at different values of residence time (i.e., inlet gas velocity) and (external convective) heat transfer coefficient. Simulations at the same conditions were also run for a standard parallel-channel (PC) configuration of equivalent dimensions. Numerical results show that the operating window of stable combustion is wider in the case of the NI configuration. In particular, the blow-out behavior is substantially the same for the two configurations. Conversely, the extinction behavior, which is dominated by competition between the heat losses towards the external environment and the heat produced by combustion, differs. The NI configuration exhibits a greater ability than the PC configuration to keep the heat generated by combustion trapped inside the micro-reactor. As a consequence, extinction occurs at higher values of residence time and heat transfer coefficient for this novel configuration.

Improved VDC Casting of Aluminium Alloys through an Understanding of the Surface Properties of the Molten Metal

2006 ◽  
Vol 519-521 ◽  
pp. 1693-1698
Author(s):  
John A. Taylor ◽  
Ian F. Bainbridge
Keyword(s):  
Surface Properties ◽  
Molten Metal ◽  
Aluminium Alloys ◽  
Defect Formation ◽  
Direct Chill ◽  
Gradual Change ◽  
Liquid Aluminium ◽  
Hot Top ◽  
Metal Head ◽  
Wide Range

Vertical direct chill (VDC) casting of aluminium alloys is a mature process that has evolved over many decades through gradual change to both equipment design and casting practice. Today, air-pressurised, continuous lubrication, hot top mould systems with advanced station automation are selected as the process of choice for producing extrusion billet. Specific sets of operating parameters are employed on these stations for each alloy and size combination to produce optimal billet quality. The designs and parameters are largely derived from past experience and accumulated know-how. Recent experimental work at the University of Queensland has concentrated on understanding the way in which the surface properties of liquid aluminium alloys, e.g., surface tension, wetting angle and oxide skin strength, influence the size and shape of the naturally-stable meniscus for a given alloy, temperature and atmosphere. The wide range of alloyand condition-dependent values measured has led to the consideration of how these properties impact the stability of the enforced molten metal meniscus within the hot top mould cavity. The actual shape and position of the enforced meniscus is controlled by parameters such as the upstream conduction distance (UCD) from sub-mould cooling and the molten metal head. The degree of deviation of this actual meniscus from the predicted stable meniscus is considered to be a key driver in surface defect formation. This paper reports on liquid alloy property results and proposes how this knowledge might be used to better design VDC mould systems and casting practices.

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