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Article
Publication date: 27 November 2018

Cunfu Yan, Shujuan Li, Leipeng Yang and Longfei He

The purpose of this paper is to investigate the effects of parameters on the liquid phase migration (LPM) during the freeze-form extrusion fabrication (FEF) process.

Abstract

Purpose

The purpose of this paper is to investigate the effects of parameters on the liquid phase migration (LPM) during the freeze-form extrusion fabrication (FEF) process.

Design/methodology/approach

To carry out this study, three factors were systematically investigated using orthogonal design of experiments. These three parameters are the extrusion velocity, the extrusion interval time and the extrusion head length. An orthogonal array with nine test units was selected for the experiments. Range analysis and analysis of variance were used to analyze the data obtained by the orthogonal experiments to identify the order of significant factors on LPM.

Findings

It was found that the LPM decreased with the increase of extrusion velocity and increased with the lengthening of extrusion interval time and the length of the extrusion nozzle. The order of significant factors for the LPM were found to be extrusion velocity > extrusion nozzle length > extrusion interval time.

Practical implications

Using an orthogonal design of experiments and a statistical analysis method, the liquid content of extrudate can be predicted and appropriate process parameter values can be selected. This leads to the minimization of LPM during the FEF process. Also, this analysis method could be used to study the LPM in other paste extrusion processes.

Originality/value

This paper suggests that the factors have significant impact on LPM during FEF process. The following analysis in this paper is useful for FEF users when prediction of LPM is needed. This methodology could be easily applied to different materials and initial conditions for optimization of other FEF-type processes. The research can also help to get better understanding of LPM during the FEF process.

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Book part
Publication date: 12 July 2021

Loke Kok Foong, Ramli Nazir, Radzuan Sa’ari, Mohd Zamri Ramli, Mohd Ridza Mohd Haniffah, Erwan Hafizi Kasiman and Noraliani Alias

The evolution in developed countries has taken a role in global warming and natural disasters such as flash flood, El-Nino, earthquake and groundwater contamination. The…

Abstract

The evolution in developed countries has taken a role in global warming and natural disasters such as flash flood, El-Nino, earthquake and groundwater contamination. The underground storage tank leakage problems and spillage of hydrocarbon liquid leading to the contamination of non-aqueous phase liquids (NAPLs) into the groundwater could reduce the quality of groundwater. This chapter is intended to investigate the behaviour and the pattern of NAPL migrations in double-porosity soil under vibration and intact conditions. The experimental model is developed by using kaolin soil type S300 and toluene as NAPLs. The kaolin soil was mixed with 25% of moisture content to produce kaolin granules in the soil column and vibrate under 0.98 Hz of frequency within 60 seconds. As a result, both specimen liquids completely migrated to the bottom of soil column: sample 1 has higher permeability compared to sample 2. This is due to the fracture in double-porosity soil under vibration effect and loosened the soil structure in sample 1 compared to good intact soil sample 2 with stronger and compact soil structure. In conclusion, this study proves that the dangerous hydrocarbon NAPL migration in fractured double-porosity soil has very harmful effect on the environment and groundwater resources.

Details

Water Management and Sustainability in Asia
Type: Book
ISBN: 978-1-80071-114-3

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Book part
Publication date: 12 July 2021

Mohd Fadhli Abd Rashid, Noraliani Alias, Kamarudin Ahmad, Radzuan Sa’ari, Frank Tsung-Chen Tsai, Mohd Zamri Ramli and Zulkiflee Ibrahim

The impact of climate change towards water surface resources is crucial, particularly in developing and non-developing countries. Groundwater as a main water resource is…

Abstract

The impact of climate change towards water surface resources is crucial, particularly in developing and non-developing countries. Groundwater as a main water resource is thus an essential. However, contamination due to hydrocarbon spills affects the groundwater as a water resource, especially as a main source of drinking water. This chapter investigates the light non-aqueous phase liquid (LNAPL) penetrations in double-porosity soil with different moisture contents and with or without vibration impact. It also explains the LNAPL penetration phenomena by employing image analysis. The physical laboratory experiments were implemented using an acrylic cylinder, a mirror, toluene and a Nikon D90 DSLR digital camera. Prepared soil was poured in an acrylic cylinder and compressed with compressor until it became 10 cm in height. LNAPL was then poured instantaneously onto the acrylic cylinder that was filled with soil sample. The LNAPL penetration patterns were recorded and monitored using a Nikon D90 DSLR digital camera. The processing technique was conducted at predetermined time intervals using Surfer software and Matlab routine to plot the LNAPL pattern. The results showed that a higher penetration rate of LNAPL occurred with higher moisture content and without vibration impact. The penetration time for LNAPL to reach the bottom of the soil sample was found to be longer for the soil that had low moisture content and with vibration impact.

Details

Water Management and Sustainability in Asia
Type: Book
ISBN: 978-1-80071-114-3

Keywords

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Book part
Publication date: 12 July 2021

Abstract

Details

Water Management and Sustainability in Asia
Type: Book
ISBN: 978-1-80071-114-3

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Article
Publication date: 27 March 2009

Tieshu Huang, Michael S. Mason, Xiyue Zhao, Gregory E. Hilmas and Ming C. Leu

The purpose of this paper is to develop an inexpensive and environmentally friendly solid freeform fabrication technique, called the freeze‐form extrusion fabrication…

Abstract

Purpose

The purpose of this paper is to develop an inexpensive and environmentally friendly solid freeform fabrication technique, called the freeze‐form extrusion fabrication (FEF), and use this technique in advanced ceramic fabrication.

Design/methodology/approach

FEF uses a highly loaded aqueous ceramic paste (≥50 vol.% solids loading) with a small quantity (2 vol.%) of organic binder to fabricate a ceramic green part layer by layer with a computer‐controlled 3D gantry machine at a temperature below the freezing point of the paste. Further, a freeze‐drying technique is used for preventing deformation and the formation of cracks during the green part drying process. Following the freeze‐drying, the ceramic green part undergoes binder removal and is sintered to near full density.

Findings

Extrudable, alumina pastes of high solids loading and process parameters for FEF processing of these pastes have been developed. Paste rheological properties and stability, extrusion rate, 3D gantry motion speed and other process parameters strongly affect the quality of the final ceramic parts. The minimum deposition angle, which reflects the maximum amount of extrusion offset to produce components with overhanging features without using support materials, is strongly related to the fabrication (environment) temperature. The lower the fabrication temperature, the lower the minimum deposition angle that could be achieved. Four point bending flexure strengths of the FEF processed Al2O3 test samples were 219 and 198 MPa for longitudinally deposited and transversely deposited samples, respectively. Major defects, which limited the strength of the materials, were due to under‐filling during the extrusion.

Originality/value

Successful development of the FEF technique will introduce a new approach to manufacturing ceramic materials into useful, complex shapes and components. The significant advantages of this technique include the use of environmentally friendly processing medium (water), inexpensive method of medium removal (freeze‐drying), and a much smaller quantity of organic binder to remove by pyrolysis techniques. The products can be sintered to near full density.

Details

Rapid Prototyping Journal, vol. 15 no. 2
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 16 January 2009

Xuesong Lu, Yoonjae Lee, Shoufeng Yang, Yang Hao, Julian Evans and Clive Parini

The aim of this paper is to provide an easy method of extrusion freeforming to fabricate microwave electromagnetic bandgap (EBG) crystals. EBG crystals are periodic…

Abstract

Purpose

The aim of this paper is to provide an easy method of extrusion freeforming to fabricate microwave electromagnetic bandgap (EBG) crystals. EBG crystals are periodic dielectric structures that can block wave propagation and generate a bandgap. These crystals can be used in high capability antennae, electromagnetic wave semiconductors, microresonators, high‐reflectivity mirrors and polarizing beam splitters.

Design/methodology/approach

The effects of extrusion process parameters and paste characteristics were investigated. Finally, one‐period and two‐period woodpile EBG crystals with bandgaps in the frequency region of 90‐110 GHz were fabricated and the bandgap was measured.

Findings

The filament diameter is influenced by whether extrusion is carried out with or without a substrate and by the free fall‐distance from the nozzle. The quality of lattice structures is dependent on paste flow and properties. A ceramic paste with 60 vol. % (the fraction of ceramic powder based on solvent‐free polymer) was well suited to fabrication. The solvent content also influenced the fabrication. The experimental results show that under ∼12 per cent solvent mass fraction in the paste and relatively high extrusion ram velocity (more than 0.014 mm/s) at a pressure of 14 MPa, samples with high quality were fabricated.

Originality/value

This paper demonstrates that the rapid prototyping method of extrusion freeforming can be applied for the fabrication of EBG crystals from ceramic powders and the important factors which influence the product quality are identified.

Details

Rapid Prototyping Journal, vol. 15 no. 1
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 1 March 2005

Jingzhe Pan and H.N. Ch’ng

This paper presents a unified framework to model the sintering process of fine powders. The framework is based on classical virtual power principle and its corresponding…

Abstract

This paper presents a unified framework to model the sintering process of fine powders. The framework is based on classical virtual power principle and its corresponding variational principle. Firstly, the classical models of solid state, viscous and liquid phase sintering are reproduced assuming single matter re‐distribution mechanism and using the virtual power principle as the starting point. Then we demonstrate how to obtain the governing equations for microstructural evolution using the variational principle. These provide a common thread through the existing sintering models. Finally a numerical solution scheme is briefly outlined for computer simulation of microstructural evolution using the variational principle as the starting point. The computer simulation can follow the entire sintering process from powder compact to fully dense solid and deal with fully couple multi‐physics processes involving all the possible underlying matter re‐distribution mechanisms. Several examples are provided to demonstrate the deep insights that can be gained into the sintering process by using the numerical tool.

Details

Multidiscipline Modeling in Materials and Structures, vol. 1 no. 3
Type: Research Article
ISSN: 1573-6105

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Article
Publication date: 14 March 2019

Ali Daher, Amine Ammar and Abbas Hijazi

The purpose of this paper is to develop a numerical model for the simulation of the dynamics of nanoparticles (NPs) at liquidliquid interfaces. Two cases have been…

Abstract

Purpose

The purpose of this paper is to develop a numerical model for the simulation of the dynamics of nanoparticles (NPs) at liquidliquid interfaces. Two cases have been studied, NPs smaller than the interfacial thickness, and NPs greater than the interfacial thickness.

Design/methodology/approach

The model is based on the molecular dynamics (MD) simulation in addition to phase field (PF) method, through which the discrete model of particles motion is superimposed on the continuum model of fluids which is a new ide a in numerical modeling. The liquidliquid interface is modeled using the diffuse interface model.

Findings

For NPs smaller than the interfacial thickness, the results obtained show that the concentration gradient of one fluid in the other gives rise to a hydrodynamic drag force that drives the NPs to agglomerate at the interface. Whereas, for spherical NPs greater than the interfacial thickness, the results show that such NPs oscillate at the interface which agrees with some experimental studies.

Practical implications

The results are important in the field of numerical modeling, especially that the model is general and can be used to study different systems. This will be of great interest in the field of studying the behavior of NPs inside fluids and near interfaces, which enters in many industrial applications.

Originality/value

The idea of superimposing the molecular dynamic method on the PF method is a new idea in numerical modeling.

Details

Engineering Computations, vol. 36 no. 3
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 5 October 2018

Alessandro Quintino, Marta Cianfrini, Paweł Ocłoń, Elisa Ricci and M. Corcione

Laminar natural convection of nanofluids in a square cooled cavity enclosing a heated horizontal cylinder is studied numerically. This paper aims to investigate in what…

Abstract

Purpose

Laminar natural convection of nanofluids in a square cooled cavity enclosing a heated horizontal cylinder is studied numerically. This paper aims to investigate in what measure the nanoparticle size and average volume fraction, the cavity width, the cylinder diameter and position, the average temperature of the nanofluid and the temperature difference imposed between the cylinder and the cavity walls, affects the basic heat and fluid flow features, as well as the thermal performance of the nanofluid relative to that of the base liquid.

Design/methodology/approach

The four-equation system of the mass, momentum and energy transfer governing equations has been solved using a computational code incorporating three empirical correlations for the evaluation of the effective thermal conductivity, the effective dynamic viscosity and the coefficient of thermophoretic diffusion, all based on a high number of experimental data available in the literature. The SIMPLE-C algorithm has been used to handle the pressure-velocity coupling. Simulations have been performed using Al2O3 + H2O, for different values of the average volume fraction of the suspended solid phase in the range 0-0.04, the diameter of the nanoparticles in the range 25-75 nm, the temperature difference imposed between the cylinder and the cavity walls in the range 5-20 K, the average nanofluid temperature in the range 300-330 K, the ratio between the cylinder diameter and the cavity width in the range 0.1-0.5 m, the ratio between the distance of the cylinder axis from the bottom wall and the cavity width in the range 0.2-0.8 and the ratio between the distance of the cylinder axis from the left sidewall and the cavity width in the range 0.2-0.5.

Findings

The main results obtained may be summarized as follows: the overall solid phase migration from hot to cold results in a cooperating solutal buoyancy force which tends to compensate the friction increase consequent to the viscosity growth due to the dispersion of the nanoparticles into the base fluid; the effect of the increased thermal conductivity consequent to the nanoparticle dispersion into the base fluid plays the major role in determining the heat transfer enhancement of the nanofluid, at least in the upper range of the investigated average temperatures; at high temperatures, the nanofluid heat transfer performance relative to that of the pure base liquid increases with increasing the average volume fraction of the suspended solid phase, whereas at low temperatures, it has a peak at an optimal particle loading; the relative heat transfer performance of the nanofluid increases notably with increasing the average temperature, and just moderately as the imposed temperature difference, the width of the cavity and the distance of the cylinder from the bottom of the cavity, are increased; the relative heat transfer performance of the nanofluid increases as the nanoparticle size, the cylinder diameter and the distance of the cylinder from the sidewall, are decreased; as a consequence of the local competition between the thermal and the solutal buoyancy forces, a periodic flow arises when the cylinder is located in the vicinity of one of the cooled walls of the enclosure.

Originality/value

Framed in this general background, a comprehensive numerical study on buoyancy-driven convection of alumina-water nanofluids inside a cooled square cavity containing a heated circular cylinder is executed by the way of a two-phase model based on the double-diffusive approach accounting for the effects of the Brownian diffusion and thermophoresis.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 28 no. 11
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 12 September 2017

Stephanie Perkiss and Karen Handley

The purpose of this paper is to explore economic conditions of contemporary society to provide insight into the ways in which the consequences of disaster, including…

Abstract

Purpose

The purpose of this paper is to explore economic conditions of contemporary society to provide insight into the ways in which the consequences of disaster, including environmental migration, are accentuated.

Design/methodology/approach

This research draws on Zygmunt Bauman’s theory of liquid modernity and notions of development to analyse disaster. From the analysis, a new concept, liquid development, is proposed and critiqued as a contributing factor leading to severe contemporary disaster.

Findings

Liquid development provides a new way of making sense of the conditions and consequences of economic growth and a business as usual attitude. It further provides a framework to explore the potential disaster of environmental migration in the Pacific Islands arising from liquid development driven climate change-induced sea level rise.

Research limitations/implications

Analysing these conditions provides greater understanding of the resulting impact of disaster, creating awareness and informing the need for accountability and social policy. This study aims to contribute to further practical and research enquiry that will challenge liquid developers to reconsider their impact and to accept responsibility for vulnerable members of society as part of their business as usual structure.

Originality/value

This paper adds to Bauman’s understanding of the consequences of globalisation through the construct of liquid development. It also continues his debate by giving awareness to the global issue of environmental migration.

Details

International Journal of Sociology and Social Policy, vol. 37 no. 9/10
Type: Research Article
ISSN: 0144-333X

Keywords

1 – 10 of 556