bluuebunny/crossref_metadata_2025 huggingface dataset:
The virtual core - modelling and optimization of core manufacturing and application
Authors: Thorborg J , Kumar S , Wagner I , Sturm J C
Published: June 2020

Development and manufacturing of high quality cast parts with tight dimensional requirements depend to a large extent on the stability and application of the sand cores. The core-sand is based on a complex granular multi-material system, where curing of an organic or inorganic system bond the grains into a porous core. The chosen combination of sand and binder determines the thermo-mechanical properties of the core. The paper provides an overview of current modelling capabilities along the life cycle of sand cores. A detailed analysis of the production steps is presented as well as the resulting properties linked to the application in the casting process. Several questions and some answers are given to the understanding of core related defects and how simulation can bridge the gap between core production and application of cores in the casting process. Today, process simulation of sand core production is an accepted tool for core box design and prediction of robust production conditions. The first modelling step is core shooting where expanding air is the driving force for sand flow from a core shooting machine into the core box. Coupled two phase flow modelling of air and granular material is required to represent the process sufficiently. The final process step in core manufacturing is core curing and moisture transport where porous media gas flow modelling is applied. Phase transformations as well as the relevant transport phenomena and the complete heat balance in case of thermally controlled processes need to be considered. During casting the deformation of the bonded sand material is generally governed by thermal expansion, phase transformation and the location of core prints. For long thin walled cores, buoyancy forces due to density differences between the cast material and the bonded sand material can play an important role due to creep effects in the organic binder systems. For inorganic systems moisture content and moisture transport during casting are affecting the mechanical behaviour, such as bending strength. The paper presents a detailed overview of a recent implemented soil plasticity model which is calibrated for different binder systems and sand types. The data are based on comprehensive mechanical tests to provide temperature, moisture and time dependent input data for the shown examples. This includes new steps and future challenges in modelling the anisotropy of printed sand cores and digitalization of the foundry in general.
Solidification microstructure selection maps for laser powder bed fusion of multicomponent alloys
Authors: Mohammadpour P , Phillion A B
Published: June 2020

Solidification Microstructure Selection (SMS) maps provide a simple yet effective approach to predict the non-equilibrium solidification microstructure and grain morphology during Additive Manufacturing. In this study, SMS maps have been created for the Inconel 625 (IN625) alloy processed by Laser Powder Bed Fusion (LPBF). Toward this end, theoretical solid growth models, a model of the Columnar to Equiaxed Transition (CET), interface response theory, thermal simulation results and computational thermodynamics are utilized. The predicted microstructures are compared both qualitatively and quantitatively to experimentally-obtained micrographs. The theoretical analysis was also compared to the earlier analytical calculation for Al-10Si-0.5Mg alloy to show how differences in thermophysical properties affect the microstructural predictions. The theoretical predictions are shown to be in good agreement with the experimental results in terms of the resulting microstructure and dendrite arm spacings. A discussion on the use of SMS maps, formed over a broad range of thermophysical conditions, to help guide industry in improving LPBF microstructure, is provided.
Resolving the effects of local convective heat transfer via adjustment of thermo-physical properties in pure heat conduction simulation of Laser Powder Bed Fusion (L-PBF)
Authors: Bayat M , Nadimpalli V K , Mohanty S , Hattel J H
Published: June 2020

Numerical models, especially when validated against experimental findings, are valuable tools that can be used as a cheap and reliable alternative to the expensive and time-consuming experimental investigations. In the current work, a multiphysics model of laser powder bed fusion (L-PBF) has been developed for stainless steel SS 316-L and validated against experimental findings. By configuring the model, the effects of the inverse Marangoni flow on the melt pool morphology and the heat and fluid flow conditions were analysed. It was shown that for high surface tension sensitivities, the total heat flux through the melt pool boundaries increases. The enhanced cooling will lead to a smaller melt pool size with larger depth to width ratio and causes a relatively uniform temperature field, which reduces the role of the conduction heat transfer. Furthermore, a Nusselt number was derived to quantify the role of the Marangoni effect on the convection heat transfer from the melt pool. This expression was used to calculate an effective thermal conductivity required for a modified pure conduction heat transfer calculation. It was shown that, via using a combination of the derived Nusselt number and the concept of the effective thermal conductivity, the average melt pool temperature determined from the modified pure conduction model gets very close to that of the more advanced CFD model.
Capturing Marangoni flow via synchrotron imaging of selective laser melting
Authors: Clark S J , Leung C L A , Chen Y , Sinclair L , Marussi S , Lee P D
Published: June 2020

Marangoni flow has a substantial influence on the quality of components fabricated via laser powder bed fusion (LPBF). However, Marangoni flow in melt pools is rarely quantified due to the opacity of liquid metals and the necessity for in situ evaluation. Here we report the findings of high-temporal-resolution synchrotron x-ray radiography experiments tracking the flow in the melt-pool. Dense, highly attenuating tungsten carbide particles are seeded within an elemental powder blend of aluminium and copper of varying composition. Due to the extremely high temporal resolution of greater than 50 kfps at the 31-ID-B beamline at the Advanced Photon Source, USA, we can track the position of tracer particles from frame to frame. This data provides valuable process guidance for optimising mixing and informs the development and validation of multiphysics models.
Melt pool morphology in directed energy deposition additive manufacturing process
Authors: Chen Y , Clark S , Leung A C L , Sinclair L , Marussi S , Atwood R , Connoley T , Jones M , Baxter G , Lee P D
Published: June 2020

Directed Energy Deposition Additive Manufacturing (DED-AM) is one of the principal AM techniques being explored for both the repair of high value components in the aerospace industry as well as freeform fabrication of large metallic components. However, the lack of fundamental understanding of the underlying process-structure-property relationships hinders the utilisation of DED-AM for the production or repair of safety-critical components. This study uses in situ and operando synchrotron X-ray imaging to provide an improved fundamental understanding of laser-matter interactions and their influence on the melt pool geometry. Coupled with process modelling, these unique observations illustrate how process parameters can influence the DED-AM melt pool geometry. The calibrated simulation can be used for guidance in an industrial additive manufacturing process for microstructure and quality control.
Modelling viscoplastic behavior of solidifying shell under applied electromagnetic breaking during continuous casting
Authors: Vakhrushev A , Kharicha A , Wu M , Ludwig A , Nitzl G , Tang Y , Hackl G , Watzinger J , Rodrigues C M G
Published: June 2020

Since several decades the continuous casting (CC) process became one of the dominant technologies for the metal production. The quality optimization and the production rate growth are the primary targets. Nowadays the numerical modelling is a valuable tool to assist in these aims. Moreover, it efficiently competes with the physical experiment and the industrial trials. One of the key issues with the high casting speeds especially for the thin slab products are the strong turbulent flow of the fresh melt being feed from the submerged entry nozzle (SEN) and the non-uniformity of the solidifying shell thickness. Thereby the electromagnetic braking (EMBr) is typically applied to damp the hot jets and to evenly redistribute the superheat. In the previous work it was shown by the authors that the presence of the highly conductive solid shell plays crucial role for the melt flow under the applied magnetic field. Excluding this interaction does not allow predicting the EMBr effects on the melt flow correctly during the solidification. Recently a viscoplastic deformation model was implemented to model a withdrawal of the solidified shell in a funnel type CC mold for a full 3D engineering geometry. An extended model was used to predict the macro-segregation during twin-roll casting of an Al-alloy using 2D assumption due to the large width / thickness ratio of the casted sheet. In the current study an effort is done to combine the viscoplastic deformation model of the solidified shell and the magnetohydrodynamics effects of the EMBr. The flow field alternation as well as the thickness of the solidified shell during CC are presented and analyzed with and without the magnetic field been applied.
Modelling of localised shrinkage pressure in a directionally solidifying domain
Authors: Nenchev B , Gill S
Published: June 2020

A novel approach to modelling shrinkage during solidification has been proposed. It combines Phase-field (PF) simulation with fluid mechanics for a solidifying medium. A mass balance method, based on a viscous creeping flow in two phases (liquid, solid and interface) with an applied penalisation coefficient is proposed. The role of this coefficient is to continually separate the fluid from the solid domain in correspondence to any change due to a phase transformation process. The advantage of the method is that the medium is modelled with no explicit tracking of the interface which significantly improves computational cost and the ease of implementation. This is achieved via the application of a monolithic ‘single-field’ formulation to the system of equations. The method has the potential to locally calculate shrinkage pressure by taking into account multiple parameters, including thermal gradient, permeability, viscosity and morphology.
Modeling mixed columnar-equiaxed solidification of Sn-10wt%Pb alloy under forced convection driven by travelling magnetic stirring
Authors: Zhang Z , Wu M , Zhang H , Karimi-Sibaki E , Ludwig A , Kharicha A
Published: June 2020

A mixed columnar-equiaxed solidification model was used to investigate the solidification benchmark experiments, as performed at SIMAP Laboratory. The first experiment case of the benchmark made under natural convection condition was successfully simulated previously. The current work is to simulate the second experiment case, i.e. the casting under travelling magnetic stirring (TMS) which is applied in the direction of natural convection to enhance the natural convection. Crystal fragmentation of columnar dendrites is assumed as the sole origin of equiaxed crystals. Through the analysis of the simulation results, deep understanding to the experimentally reported phenomena was achieved. In comparison to the first experiment case of pure natural convection condition, the TMS-enhanced convection provides a favorable condition for columnar-to-equiaxed transition (CET) by homogenizing the temperature distribution in the bulk liquid region, enhancing the fragmentation of the columnar secondary arms and the transport of the fragments to bulk liquid region. Contradicting with the previous knowledge, the TMS-enhanced convection in this experiment case does not enhance the global macrosegregation significantly. However, it strengthens the channel segregates.
Comparison of two-phase and three-phase macroscopic models of equiaxed grain growth in solidification of binary alloy with electromagnetic stirring
Authors: Wang T , Semenov S , Wang E , Delannoy Y , Fautrelle Y , Budenkova O
Published: June 2020

Simulations of equiaxed solidification using two-phase and three-phase models are performed for the experimental benchmark AFRODITE with electromagnetic stirring. A three-phase model presented by authors elsewhere accounts for solid phase, inter- and extradendritic liquid phases. With respect to that model, the two-phase approach can be considered as reduced or simplified, yet, this implies also less number of assumptions regarding closure relations. In simulations, as expected, final segregation obtained with two–phase model is stronger, yet, it is qualitatively similar to the segregation pattern obtained with three-phase model.
Predicting the interfacial heat transfer coefficient of cast Mg-Al alloys using Beck’s inverse analysis
Authors: Bilal M U , Hort N
Published: June 2020

Apart from many governing parameters, the interfacial heat transfer coefficient (IHTC) has prime importance for the numerical simulation of casting as it quantifies the heat flux between casting and mold (or chill). Most Mg alloys are based on the Mg-Al system and casting is the commonly used production process. The experimental configuration makes it challenging to measure flux and surface temperatures required to evaluate the IHTC. In this study, the IHTC was predicted for a variety of Mg-Al compositions which were cast using a permanent cylindrical mold. Unidirectional heat flow was ensured in order to replicate the experimental conditions for solving the one-dimensional transient heat equation. The numerically determined mold and surface temperatures, using Beck’s inverse methodology, were in good agreement with the experiments and analytical solution, respectively. Moreover, the heat transfer behavior across the interface depicted in the form of IHTC was analyzed, also various empirical and numerical aspects of the method are discussed.
Permeability tensor for various columnar dendrite structures
Authors: Mitsuyama Y , Takaki T , Sakane S , Shibuta Y , Ohno M
Published: June 2020

Permeability is a very important parameter determining fluid dynamics in macroscale casting simulations. For a columnar solidification structure, the permeability has anisotropy and becomes a tensor quantity. In our previous study, we proposed a permeability tensor and confirmed its validity. In this study, the applicability of the permeability tensor is shown through a series of permeability computations that are conducted for some columnar dendritic structures with different morphologies.
Modelling of an industrial die casting process for the production of aluminum automotive parts
Authors: Ou J , Wei C , Maijer D , Cockcroft S , A L , Zhang Y , Chen Z , Zhu Z
Published: June 2020

Die (permanent) casting is one of the major manufacturing processes for aluminum automotive parts thanks to its ability to provide a good balance between mechanical performance and production efficiency. In the die casting industry, computational modelling has been widely adopted to analyze, troubleshoot and optimize die design and process parameters. In this work, a computational modelling methodology including key process boundary conditions and material properties has been developed to simulate an industrial die casting process of an aluminum automotive part. It has been demonstrated that the model is accurate and robust with respect to temperature and defect prediction by comparison with a large amount of high-quality plant-trial data. The data was acquired from an in-house designed data acquisition system (DAQ) connected to an instrumented die and industrial production equipment in a production facility.
Modelling and simulation of ingot solidification with the open-source software Code_Saturne
Authors: Demay C , Ferrand M , Belouah S , Robin V
Published: June 2020

In order to address the issue of macro-segregations in large industrial ingots, a solidification model has been recently developed in Code_Saturne, the general purpose open-source Computational Fluid tablDynamics (CFD) software developed and released by EDF R&D. This model is a liquid-solid mixture model inspired from the pioneer work of Bennon and Incropera, including mass, momentum, energy and species conservation equations. In particular, the energy conservation equation is formulated with the temperature variable, the thermosolutal convection is accounted for through the Boussinesq approximation and the interdendritic flow in the mushy zone is governed by the Darcy’s law. Furthermore, a rigid solid phase is assumed and classical microsegregation models are used featuring lever-rule or Gulliver-Scheil assumptions. At the discrete level, a first-order upwind scheme is implemented with a SIMPLEC approach to solve the velocity-pressure coupling. The other couplings involving temperature and concentration fields are efficiently solved performing sub-loops with a PISO-like approach. The overall scheme is mainly implicit with additional treatments to ensure the equilibrium between the hydrostatic pressure gradient and the buoyant forces, and to deal properly with solid zones. The segregation predictions offered by the model are validated against both academic test case and industrial ingot configurations. A convergence study is also led focusing on time step and mesh size sensitivities.
Numerical investigation of an in-situ observed flow regimes during solidification of an NH4Cl – 70 wt%H2O solution
Authors: Wu M , Stefan-Kharicha M , Kharicha A , Ludwig A
Published: June 2020

A volume-average mixed columnar-equiaxed solidification model, where the dendritic morphology of crystals is described with the dendrite envelope, was developed by the current authors. As an evaluation effort, this model is used to simulate a solidification experiment of ammonium chloride water (NH4Cl – 70 wt%H2O) solution. The solution was cooled in a water cooled copper mould (10×8×1 cm3), and the solidification process and the flow dynamics during solidification were in-situ observed/recorded with a Particle Imagine Velocimetry technique. The striking features of solidification in this experiment are that the crystal morphology is dominant in columnar structure, and typical 4 flow regimes in the bulk solution during solidification appear: pure thermal convection (TH), unstable (turbulent) flow caused by double diffusive convection (TU), turbulent-stratified flow (TU-ST), meandering flow (MF). These flow regimes correspond to different cooling/solidification stages, and reflect their interactions with the developing mushy zone. The calculated solidification sequence and the flow dynamics (4 flow regimes) agree with the experimental ones. The experimentally observed phenomena were successfully explained by the simulation.
Influence of crystal fragmentation on the formation of microstructure and macrosegregation during directional solidification under forced convection condition
Authors: Zhang H , Wu M , Zhang Z , Ludwig A , Kharicha A
Published: June 2020

Directional solidification experiment under forced convection condition was conducted. The AlSi7 alloy was solidified in an alumina cylindrical crucible (ø8 mm) in a Bridgeman furnace; and forced convection was induced by applying rotating magnetic field (RMF). The RMF induced flow in the sample during solidification leads to the formation of equiaxed crystals by the mechanism of crystal fragmentation (assumption). The current study is to use a mixed columnar-equiaxed solidification model to simulate this experiment by considering the crystal fragmentation as sole origin of equiaxed crystals. An inward flow (Ekman effect) forms in the front of the (columnar) mushy zone under the RMF. Solute-driven remelting, as enhanced by the interdendritic flow, leads to fragmentation near the columnar tip front. Some fragments are transported by the forced convection to the sample centre and remelted there, while many of them are captured by the columnar structure near the sample centre. The modelling result on the mixed columnar-equiaxed structure agrees with the post-mortem analysis of as-solidified sample. As conclusion following impacts of the crystal fragmentation on solidification are suggested: (1) it widens the central segregation channel and promotes the formation of side-arms; (2) it leads to the formation of relatively high volume fraction of equiaxed crystals near the sample centre.
Comparison of solidification kinetics of compacted and lamellar cast irons
Authors: Lacaze J , de la Torre U , Sertucha J , Regordosa A
Published: June 2020

Thermal analysis is largely used in cast-iron foundry shops as a means to check melt preparation before casting. It has been suggested that the shape of the cooling curves could be related to graphite form, either spheroidal, lamellar or else compacted. The present work is part of a larger study intended to improve melt control for compacted graphite castings by using controlled additions of sulfur and magnesium. Experiments showing lamellar graphite and their counterpart with compacted graphite have been selected for analysis and simulation of the thermal analysis records. Simulation makes use of the fact that compacted graphite differs from lamellar graphite by the limitation of graphite branching in the former. Solidification of both types of irons may thus be simulated using the same basic growth law for irregular eutectics, though changing the parameters describing the branching capability of the faceted graphite phase. The increase of the undercooling of the eutectic plateau during solidification of compacted cast iron when compared to that of lamellar cast iron could be verified and reproduced by simulation. The limitations of the present approach which assumes the temperature in thermal cups is homogeneous at any time are also pointed out.
In situ observation of austenite coarsening induced by massive-like transformation during solidification in Fe–C alloys
Authors: Yasuda H , Suga T , Ichida K , Narumi T , Morishita K
Published: June 2020

A massive-like transformation, in which δ-ferrite massively transforms to γ-austenite in the solid state, was examined by time-resolved X-ray imaging and X-ray diffractometry on a four-dimensional–computed tomography setup. In the unidirectional solidification of a hyperperitectic steel (0.3 mass% C) at 50 μm/s, δ dendrites, fine γ grains that are produced through the massive-like transformation, and coarse γ grains grow together in the steady state. The massive-like transformation occurred commonly in Fe-based alloys with a peritectic reaction in equilibrium. Time-resolved X-ray diffraction measurements for a peritectic steel (0.18 mass% C) showed that the massive-like transformation induced strains in the γ grains. The fine γ grains coarsened and/or vanished and new γ grains formed. The induced strains were released during coarsening. The results obtained by the observations contribute to building of a physical model for γ grain coarsening.
Modelling of intermetallic layers formation during solid-liquid joining of dissimilar metallic materials
Authors: Glück Nardi V , Greß T , Tonn B , Volk W
Published: June 2020

Joining of dissimilar metallic materials gives rise to the production of components with improved properties. At the joint interface, the formation of brittle intermetallic layers might deteriorate the component application. Therefore, its formation and growth must be well understood and carefully controlled. Numerical simulations assist in the determination of processes parameters to obtain the desired bond characteristics. In solid-liquid joining processes, the melt movement plays an important role und must be accounted in the simulations. In this paper, a mathematical model at the continuum scale is used for the description of the interface formation during solid-liquid joining. The description of convection and advection of the molten alloy and the dissolution of the solid substrate are of interest. The substrate dissolution into the melt alters the local composition of the molten alloy, leading to precipitation of intermetallic compounds on the substrate surface during the solidification process. To account for these phenomena, convection heat transfer with phase transformation and diffusion and reaction at the solid-liquid interface are considered in the mathematical model that is based on conservation equations of mass, momentum, energy and species. The different scale problem is solved by applying a dynamic mesh refinement at the interface to accurately solve the intermetallic layer growth. The model was implemented in OpenFoam® and simulation results for the intermetallic layer thickness as a function of solid substrate temperature (Ts) for compound casting between initially liquid Al and a solid Cu substrate are presented. In general, for Ts initial value ranging from 400 to 700 °C while keeping the initial Al melt temperate at 750 °C, the intermetallic layers thickness increases as Ts increases.
Phase field modelling of dendritic solidification by using an adaptive meshless solution procedure
Authors: Dobravec T , Mavrič B , Šarler B
Published: June 2020

A novel numerical procedure is developed for modelling two-dimensional dendritic solidification in dilute binary alloys. The evolution of the phases and the solute concentration is described by the partial differential equations, obtained from the phase field model. The meshless radial basis function-generated finite difference (RBF-FD) method is used for the spatial discretisation of the partial differential equations. The forward Euler scheme is used for the time-stepping. In order to reduce the computational cost, an adaptive procedure is developed, based on the quad-tree strategy, ensuring the highest density of the computational nodes at the solid-liquid interface. In the procedure, the computational domain is divided into overlapping sub-domains which can be dynamically refined or coarsened. The regular or scattered node distribution with constant node density is used for discretisation of each sub-domain. The h-adaptive procedure is ensured by the constant product between the area of a sub-domain and the computational node density. The accuracy and speedup in comparison to the solution on a uniform node distribution are assessed by solving the benchmark problem for dendritic solidification in dilute binary alloys. The main originality of the model represents the first use of RBF-FD method for the spatial discretisation of the PF equations in combination with adaptive solution procedure. The RBF-FD method can be used on unstructured node distributions, which is especially advantageous in the solution of PF model for dendritic growth, since the solution is very sensitive to the regularity of the node distribution. The developed spatial-temporal-adaptive numerical model represents an accurate and computationally efficient tool for the prediction of the dendrite morphology and micro-segregation during the solidification in binary alloys.
Toward the development of a thermal-stress model of an industrial counter pressure casting process
Authors: Wei C , Ou J , Fan P , Mehr F , Maijer D , Cockcroft S , Zhang Y , Chen Z , A L , Zhu Z
Published: June 2020

It is argued that the Counter Pressure Casting (CPC) process is superior over low-pressure die casting (LPDC) in terms of reducing defects and improving cast product performance. To date, there has been relatively little research conducted on the CPC process to provide reliable data to confirm this argument. In this work, a plant trial has been done on an industrial CPC process using a custom-designed ‘H-shaped’ die to acquire an extensive amount of quantitative process data. The data acquired includes temperatures obtained from within the die, the casting, the surrounding environment, and within specific die cooling channels. The data has been processed and analysed to support the development of a comprehensive thermal-stress model of the casting process in order to better understand and quantify the essential macro transport processes. This paper presents a methodology of a coupled thermal-stress model development on the CPC process, and the preliminary results obtained from the models. The results to-date clearly show the need for a fully coupled thermal-stress analysis for the particular casting geometry and process conditions examined. Some of the challenges associated with the current modelling approach are also identified and potential solutions presented.
Application of multi-phase-field lattice Boltzmann method to semi-solid deformation
Authors: Yamanaka N , Sakane S , Takaki T
Published: June 2020

Mechanisms of semi-solid deformation are crucial for reducing solidification defects. In this study, a multi-phase-field lattice Boltzmann (MPF-LB) model, which can simulate growth of multiple dendrites with liquid flow, solid motion and collision, is applied to semi-solid deformation. An elastic contact is introduced to the MPF-LB model to consider collision of two grains. The semi-solid deformation with globular morphology is simulated in the two-dimension by the MPF-LB method. Through the simulations, high potential of the MPF-LB model as the evaluation method of semi-solid deformation is confirmed.
Progress in the development of a contactless ultrasonic processing route for alloy grain refinement
Authors: Pericleous K A , Beckwith C , Bojarevics V , Djambazov G , Dybalska A , Griffiths W D , Tonry C
Published: June 2020

A high frequency tuned electromagnetic (EM) induction coil can be used to induce ultrasonic pressure waves leading to gas cavitation in alloy melts. This is a useful ‘contactless’ approach compared to the usual immersed sonotrode technique. One then expects the same benefits obtained in the traditional ultrasonic treatment (UST) of melts, such as degassing, microstructure refinement and dispersion of particles. However, such an approach avoids melt contamination due to probe erosion prevalent in immersed sonotrodes and it has the potential to be used on higher temperature and reactive alloys. Induction stirring due to the Lorentz force produced by the coil is an added benefit, allowing for the treatment of large melt volumes, a current limitation of UST systems. At ultrasonic frequencies (> 20 kHz), due to the ‘skin effect’ electromagnetic forces vibrate just a thin volume by the surface of the metal facing the induction source. These vibrations are transmitted as acoustic pressure waves into the bulk and to achieve sufficient fluctuation amplitudes for cavitation, acoustic resonance is sought by carefully adjusting the generator frequency. This is akin to the tuning of a musical instrument, where the geometry and sound properties of the metal, crucible and surrounding structure play an important part. In terms of modelling, this is a multi-physics system, since fluid flow with heat transfer and phase change are coupled to electromagnetic and acoustic fields. The various models used and their coupling are explained in this paper, together with the various complications arising by the physics of cavitation. Experimental validation is obtained on a prototype rig featuring a conical induction coil inserted into the melting crucible containing the various alloys being examined. When resonance is reached, measurements demonstrate strong stirring, evidence of cavitation and finally grain refinement.
Study on the effect of ultrasonic wave amplitude on de-emulsification of crude oil to enhance production process
Authors: Lim C H , Sulaiman S A , Japper-Jaafar A , Bhaskoro P T
Published: June 2020

One of the most challenging issue faced by the oil and gas industry is the formation of crude oil emulsion. The emulsion formation will lead to inconsistency in the production performance, which directly affects the economic growth of the industry. Current, conventional de-emulsification methods such as thermal, demulsifiers, and electrical methods are found ineffective in solving crude oil emulsion problem relativity to expected settling time. Therefore, this research aims to propose ultrasonic wave application method for better separation rate to solve crude oil emulsion problem. The effects of ultrasonic waves are investigated by designed experiment under different operating temperature. The optimum operating conditions are investigated and identified through optimization methods in Design Expert Software. The goals of this research are to achieve maximum water and oil separation and minimize the rag layer thickness. Based on the experiments and results, the best operating condition is at operating temperature of 60 °C at 40 μm of ultrasonic frequency of 20 kHz. These parameters were able to provide 73.3% of water separation rate and 20% volume fraction of oil layer after eight hours of bottle test.
Fluidized bed drying of stingless bee pot-pollen: Performance of swirling distributor
Authors: Halim L A , Basrawi M F , Yudin A S M , Faizal S N
Published: June 2020

Pot-pollen is pollen collected by stingless bee, mixed with honey and bee secretion, and then stored in cerumen pots. Raw pot-pollen contains high moisture content which can lead to excessive fermentation and spoilage. Drying of pot-pollen is needed to preserve them. Typically, elevated temperature can increase the drying performance. However as pot-pollen is heat sensitive, heating above 40 °C is not preferable. Hence, the objective of this study is to explore drying performance of fluidized bed dryer with swirling distributor. The experiment was conducted using three different distributors, a perforated distributor, 45° and 67° swirling distributor, at 1.0 m/s and 1.5 m/s superficial air velocities. The weight of pot-pollen used in this experiment is 50 grams. The drying experiment was conducted at ambient conditions, with no heating being applied to the pot-pollen samples. It was found that 67° swirling distributor at 1.5 m/s superficial air velocity has the highest improvement in terms of drying performance, able to reduce the moisture content from 30.5 % to 18 % for 30 minutes drying time. Hence, using swirling distributor is a suitable enhancement to fluidized bed drying especially for heat sensitive food materials.
Gasification of raw and torrefied empty fruit bunch using bubbling fluidized bed
Authors: Abdul Halim N H , Saleh S , Abdul Samad N A F
Published: June 2020

An experimental study of bubbling fluidized bed gasification process using empty fruit bunch (EFB) as a feedstock has been performed in order to study the effect of gasification temperature on gasification performance. Two types of EFB have been used, which are raw EFB and torrefied EFB at 300 °C. The composition of the synthesis gas, gas yield, low heating value (LHV), cold gas efficiency (CGE), and carbon conversion (CC) was determined and analyzed. In terms of synthesis gas, the composition of hydrogen and carbon monoxide gases were increased while methane and carbon monoxide gases were decreased for raw and torrefied EFB when the temperature is increased from 650 to 900 °C. Meanwhile, the synthesis gas yield was significantly enhanced and reached the maximum value of 1.21 and 1.45 MJ/Nm3 for raw and torrefied EFB respectively, which indicates that the torrefaction process improves the synthesis gas yield. Besides, the LHV for the torrefied EFB at highest gasification temperature is 11.08 MJ/Nm3 which is higher than raw EFB (10.81 MJ/Nm3). However, the value of CGE and CC of torrefied EFB are lower than raw EFB with the different about 3% and 5% respectively.
Integrated reservoir study using well-test deconvolution analysis and well-logging data in a gas condensate carbonate reservoir
Authors: Geravand R , Foroozesh J , Nakhaee A , Abbasi M
Published: June 2020

This paper presents an integrated approach to characterize a gas-condensate carbonate reservoir using the combination of well-test deconvolution analysis, and well logging interpretation. Each set of data from the subject well, namely, petrophysical logs, production logs, surface well tests and drill-stem tests was analysed. Well test analyses was implemented using both pressure-derivative and variable-rate deconvolution techniques. An integrated analysis and interpretation of the results from different sources was performed. This approach was especially beneficial in reducing some uncertainties such as the layered nature of the reservoir, the heterogeneous behaviour, and boundary-dominated flow regimes. The application of deconvolved derivative increased the radius of investigation and duration of original constant-rate pressure from 24 hours to 140 hours, enabling us to detect the possible fault effect at late-times. This method was also used for performance evaluation of an acid treatment job in the wellbore. It was found that after acidizing, the total skin factor was severely reduced from 33 to 1.2, indicating a successful performance of the acidizing job.
Investigation of gap losses in a modified compound parabolic concentrating collector with evacuated tube receiver
Authors: Akhter J , Gilani S I , Al-Kayiem H H , Al-Hassan I
Published: June 2020

Compound parabolic concentrating (CPC) collectors paired with evacuated tube receivers have great potential to supply solar thermal energy for numerous applications operating in the medium temperature range. Optical losses resulting from the gap between inner absorber tube and cusp of reflectors badly affect the performance of such collectors. In this paper, a modified design and optical performance of a CPC collector with evacuated tube receiver is presented. Effect of reflectors truncation on the collector’s parameters including aperture width, concentration ratio and energy collection is also evaluated. Ray tracing simulation is performed to assess the instantaneous and daily energy collection. Optical performance of a cusp type CPC is compared with that of a modified CPC with w-shaped cavity at the bottom of reflectors to evaluate gap losses. Optical power density and daily average energy collection by cusp type CPC was 26% higher than CPC with w-shaped cavity due to relatively larger aperture size. CPC with w-shaped cavity was 11% more efficient than CPC with cusp type reflectors.
Investigation of stability, dispersion, and thermal conductivity of functionalized multi-walled carbon nanotube based nanofluid
Authors: Hussein O A , Habib K , Nasif M , Saidur R , Muhsan A S
Published: June 2020

In the attempt of preparing multi-walled carbon nanotube (MWCNTs), covalent functionalisation (CF-MWCNTs) were applied. The stable thermal conductivity was measured as a function of temperature. A number of techniques, such as FTIR, FESEM and UV-vis spectrophotometer were employed to characterise both dispersion stability and morphology of functionalised materials. By using ultrasonic test time, the highest stability of nanofluids was achieved at 60 minutes. As a result, the thermal conductivity displayed by CF-MWCNTs was higher than distilled water. In conclusion, improvement in thermal conductivity and stability displayed by CF-MWCNTs was higher, while the best thermal conductivity improvement was recorded at 31%.
Photo-catalytic response of zinc-doped nickel ferrite nanoparticles for removal of chromium from industrial wastewater
Authors: Shoaib-ur-Rehman M , Javaid Z , Asghar I , Azam M , Shukrullah S , Iqbal F , Maqsood A , Naz M Y
Published: June 2020

In this study, Ni-ZnFe2O4 nanoparticles were synthesized by co-precipitation technique and used to remove the chromium (Cr) metal from the industrial wastewater. The synthesized nanoparticles were characterized for their structural properties and morphology by using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The average particle size of synthesized nanoparticles was calculated by applying the Scherrer’s formula on the characteristic peaks of XRD patterns. The large surface area, controlled size and well-defined structure of the synthesized Ni-ZnFe2O4 nanoparticles showed remarkable results for wastewater treatment. The characterized nanoparticles were distributed into the industrial wastewater under constant stirring for 20 minutes. The nanoparticles’ suspension was subjected to UV–VIS spectrophotometry for the study of photo-catalytic behaviour of Ni-ZnFe2O4 nanoparticles. The effect of Ni-ZnFe2O4 was investigated under visible light irradiation. Zn doping in Ni-ZnFe2O4 showed remarkable effect on efficiency of Cr removal from the wastewater.
Activation energy of domestic wastewater sludge in combustion process by using thermogravimetric analysis
Authors: Zakaria M S , Hassan S , Faizairi M N
Published: June 2020

The increasing demand of energy and environmental problem due to the consumption of fossil fuel has led the exploration of biomass fuel as an alternative energy. One of the potential biomass feedstocks that is available in Malaysia is Domestic Wastewater Sludge (DWS). In this study, DWS fuel characterization and the effect of experimental condition such as gaseous atmosphere, heating rate and particle size to the thermal behaviour of DWS has been carried out. In addition, kinetic parameter such as activation energy was determined by using the iso-conversional model free kinetic method, Flynn Wall Ozawa (FWO) model. Furthermore, lower heating rate and smaller particle size of DWS produced more volatile gas (84.51%), resulted to low ignition temperature (209°C) and low burnout temperature (515°C). Higher volatile indicates that it can accelerate the ignition process. In addition, low ignition temperature and low burnout temperature reveal that DWS can be ignited easily and shorten the time for combustion process. Based on the finding, the average activation energy for combustion of DWS which is about 143.86 kJ/mol.
Characterization of manganese/cobalt oxide composites synthesized by chemical co-precipitation method
Authors: Altaf N-H , Anjam T , Sajid M M , Shad N A , Shukrullah S , Naz M Y , Javed Y
Published: June 2020

Composite materials have emerged as new class of materials which presented unique and enhanced applications in the nanotechnology field. In this study, Cobalt oxide-manganese oxide composites have been prepared by chemical co-precipitation method. Cobalt oxide particles were first prepared and used as seeds for making composites with manganese oxide. These composites have been characterized by XRD, SEM, UV-Vis spectroscopy and FTIR. Characterization tools confirmed the formation of Manganese/Cobalt oxide composites. XRD results presented the diffraction peaks for cobalt oxide, manganese oxide and MnCo2O4 compounds. FTIR spectrum also indicated the formation of bonds between Mn, Co and O especially at 461 cm−1 shows MnCO2O4 bonding. These composite materials absorb visible light of wavelength 682 nm and can be used in light activated photocatalytic activity for the degradation of toxic dyes.
A review of synthesis roots of iron nanoparticles
Authors: Anjam T , Altaf N U H , Ahmad W , Sajid M A , Munir M A , Aslam M
Published: June 2020

Nanoscience is a standout amongst the most significant innovative work action in the outskirt of current science. From most recent two decades the nanotechnology and nanoscience have increased more significance in the field of research because of the enormous scale applications. The present work audits crafted by various researchers for the planning of iron nanoparticles by various procedures. Iron is a standout amongst the richest and generally utilized components on earth. Iron nanoparticles have a tremendous potential for various applications including magnetic liquids, magnetic resonance imaging (MRI) differentiate operators, catalyst for carbon nanotube development, nickel-iron batteries, and impetuses and sorbents for natural remediation. The preparation of iron nanoparticles by different methods, pulsed plasma, chemical reduction, chemical vapour condensation, one-step reduction, Green synthesis and Biosynthesis, its advantage over other processes are described. In this review article attempt has been made to compare each process by categorizing them specifically.
Effect of superficial air velocity on the fluidized bed drying performance of stingless bee pot-pollen
Authors: Halim L A , Basrawi M F , Faizal S N , Yudin A S M , Yusof T M
Published: June 2020

Stingless bees or “kelulut” also produce pot-pollen apart from honey. The pot-pollen is mixed with honey and bee secretion before stored in cerumen pots. It has high nutritive value and medicinal benefits. Pot-pollens are often neglected by the beekeepers due to difficulty in storing and preserving them due to high moisture content. Hence, fluidized bed dryer is proposed as a suitable method to dry and enable convenient storage and preservation of the pot-pollen. Pot-pollen sample of initial moisture content 30.5% is dried at three superficial air velocities, 1.0 m/s, 1.5 m/s, and 2.0 m/s for 30 minutes. Fluidized bed drying has managed to decrease the moisture content down to 23%, 20.5%, and 18.5%, respectively. Higher superficial air velocity lead to higher drying rate in of pot-pollen. Hence, using a fluidized bed dryer to dry stingless bee pot-pollen is a promising method for preserving them. Subsequently, the dried pot-pollen can be easily commercialized in the future.
Drying process of black pepper in a swirling fluidized bed dryer using experimental method
Authors: Roslan N F M , Yudin A S M
Published: June 2020

Black pepper (piper nigrum) is one of the well-known spices extensively used worldwide. Drying is the most popular methods of preserving the black pepper. Unfortunately, this operation may negatively influence product quality. Moreover, due to the high heat capacity of water, drying is usually a long-lasting and energy-intensive process, thus new drying techniques are continuously being sought. Fluidized bed dryers have been applied to dry raw materials due to the advantages of good mixing efficiency and high heat and mass transfer rate. In order to control and optimize the drying process of fluidized bed dryers, it is necessary to develop reliable methods to measure the moisture content of solid particles in the bed. For this project we dried the black pepper using two methods which is drying under sun drying and swirling fluidized bed dryer using heater. The temperature for both drying will be the same. Then, the characteristic and the drying moisture ratio of the black pepper were compared between these two drying methods. The performance of the swirling fluidized bed dryer was evaluated based on the percentage of moisture content of loss reduction. The time taken for this drying is 10 hours, which considered as 1 day of drying process. The percentage of moisture content loss reduction is 57.9%. The moisture ratio after 10 hours of drying is 0.3420. In conclusion, drying using swirling fluidized bed dryer is the new technology that can be used in drying industry.
Performance of Al2O3-SiO2/PAG employed composite nanolubricant in automotive air conditioning (AAC) system
Authors: Zawawi N N M , Azmi W H
Published: June 2020

Automotive Air conditioning (AAC) system is the contributor of harmful gasses emission and global warming. In order to solve the issues, investigation on potential improvement in lubrication used in air conditioning system is done to improve the system performance and efficiency. The performance of AAC system namely cooling capacity, compressor work, coefficient of performance (COP) and power consumption was investigated by comparing pure lubricant and Al2O3-SiO2/PAG nanolubricants. Performance of AAC by using different ranges of refrigerant charges (95 to 155 g) and speeds (1200 and 1800 rpm) was investigated. The result shows that the cooling capacity and COP of pure lubricant were relatively lower than Al2O3-SiO2/PAG nanolubricants. The compressor work and power consumptions of Al2O3-SiO2/PAG nanolubricants were greatly reduced. Cooling capacity and COP are enhanced by 102.99% and 23% respectively. The compressor work and power consumption are reduced by 25.9% and 28.24% respectively. From the results, nanolubricants gives more advantages in AAC performance over pure lubricant. Therefore, Al2O3-SiO2/PAG composite nanolubricants is recommended to be used as the compressor lubrication to enhance AAC performances system.