Filtration resistance during pressure filtration tests of liquid aluminium alloys

Abstract Pouring of liquid aluminium is typically accompanied by disturbance of the free surface. During these disturbances, the free surface oxide films can be entrained in the bulk of liquid, also pockets of air can be accidentally trapped in this oxide films. The resultant scattering of porosity in castings seems nearly always to originate from the pockets of entrained air in oxide films. Latest version of ProCast software allows to identify the amount of oxides formed at the free surface and where they are most likely to end-up in casts. During a filling calculation, ProCast can calculate different indicators which allow to better quantify the filling pattern. The fluid front tracking indicator “Free surface time exposure” has the units [cm2*s]. At each point of the free surface, the free surface area is multiplied by the time. This value is cumulated with the value of the previous timestep. In addition, this value is transported with the free surface and with the fluid flow. Experiments to validate this new functions were executed.

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Experimental Study and Modeling of Fouling in Immersed Membrane Bioreactor Operating in Constant Pressure Filtration

Mathematical Problems in Engineering ◽

10.1155/2013/456143 ◽

2013 ◽

Vol 2013 ◽

pp. 1-7 ◽

Cited By ~ 2

Author(s):

Mostafa Hosseinzadeh ◽

Mohammad Reza Mehrnia ◽

Navid Mostoufi

Keyword(s):

Experimental Data ◽

Experimental Study ◽

Constant Pressure ◽

Initial Rate ◽

Membrane Surface ◽

Air Velocity ◽

Pressure Filtration ◽

Filtration Resistance ◽

Proposed Model ◽

Cake Formation

A new mathematical model is proposed based on filtration mechanisms for the prediction of fouling in airlift immersed membrane bioreactors (iMBRs). The cake formation on the membrane surface through constant pressure filtration process in the iMBR was explained by a proposed cake filtration mechanism which assumes that no particle enters the pores when forming the cake layer on the membrane surface. The cake porosity reduction due to diffusion of particles was described by an intermediate blocking mechanism. Experimental study of fouling was also performed in a lab-scale airlift flat-sheet iMBR operating at constant vacuum. The mixed liquor suspended solid (MLSS) concentration was changed within the range of 5000 to 15000 mg/L, while the superficial air velocity was varied between 32 and 128 m3/m2/h. The presented model includes two parameters, that is, ultimate filtration resistance and initial rate of cake formation. The effect of the MLSS concentration and superficial air velocity on the parameters of the proposed model was studied. The results obtained from the model demonstrated that the ultimate filtration resistance and the initial rate of cake formation are more sensitive to the aeration rate at lower superficial velocities. It was also shown that the ultimate filtration resistance has a linear relation with MLSS concentration. A good agreement exists between the results of the model and the experimental data. The proposed model also showed a better compatibility with the experimental data compared to other fouling models available in the literature.

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Model of Hydraulic Resistance When Forecasting Reverse Osmosis in Water Treatment

Membranes ◽

10.3390/membranes11050314 ◽

2021 ◽

Vol 11 (5) ◽

pp. 314

Author(s):

Janina Piekutin ◽

Urszula Kotowska

Keyword(s):

Mathematical Modeling ◽

Water Treatment ◽

Hydraulic Resistance ◽

Reverse Osmosis ◽

Hydraulic Model ◽

Treated Wastewater ◽

Ammonium Ion ◽

Pressure Filtration ◽

Filtration Resistance ◽

Membrane Change

The article presents research on the treatment of infiltration water with increased ammonium ion and nitrate(V) content through reverse osmosis. Then, research was conducted on the phenomena related to the decrease in the permeability of the membrane used for the research. The search for an appropriate interpretation of the phenomena was carried out using mathematical modeling. Based on the assumptions of the hydraulic model of the filtration resistance, calculations were made to forecast the efficiency of the osmotic membrane used in the discussed process. For this purpose, the following indicators were determined experimentally for the membrane: change in the volumetric flow of treated wastewater during low-pressure filtration, total hydraulic resistance, and component resistances, i.e., the resistance of the “new” membrane and resistances resulting from the reversible and irreversible fouling phenomena. It has been observed that irreversible resistance arises in the short and early stages of the process. The efficiency is determined by reversible resistance, which is confirmed by the literature.

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

Materials Science Forum ◽

10.4028/www.scientific.net/msf.519-521.1693 ◽

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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A simple model to estimate hydrogen solubility in liquid aluminium alloys

International Journal of Cast Metals Research ◽

10.1080/13640461.2020.1767838 ◽

2020 ◽

Vol 33 (2-3) ◽

pp. 120-122

Author(s):

Murat Tiryakioğlu

Keyword(s):

Simple Model ◽

Aluminium Alloys ◽

Hydrogen Solubility ◽

Liquid Aluminium

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Instantaneous Evaluation of Inclusion Quantity of Liquid Aluminium Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.217-222.135 ◽

1996 ◽

Vol 217-222 ◽

pp. 135-140 ◽

Cited By ~ 8

Author(s):

J.L. Roberge ◽

M. Richard

Keyword(s):

Aluminium Alloys ◽

Liquid Aluminium

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Characterization of Casting Defects in Aluminium Alloys

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.430-432.984 ◽

2012 ◽

Vol 430-432 ◽

pp. 984-987

Author(s):

Guo Wu ◽

Keyna O'Reilly ◽

Marina Galano

Keyword(s):

Aluminium Alloys ◽

Oxide Films ◽

Melting Process ◽

Major Type ◽

Induction Melting ◽

Liquid Aluminium ◽

Alumina Crucible ◽

Oxide Defects ◽

Scanning Electron

In this paper, typical defects in aluminium alloys cast by conventional pouring of liquid metal into a cylindrical alumina crucible and an induction melting process are characterized by using macroetching, optical microscopy and scanning electron microscopy. Oxide film defects are generated in both processing methods. Oxide films formed during casting are a major type of defect observed in the microstructures of aluminium alloys products. It has been found that pouring of molten metal into a mould and induction stirring lead to different forms of oxide defects. Under induction stirring, such low-density entrained defects are found to be carried to near the surface of the liquid aluminium alloys and submerged surface oxide films become entangled.

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