Conference Publications
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PublicationFlow fluctuation during flow boiling of binary mixtures in high aspect ratio microchannel(IOP Publishing, 2023)Flow boiling performance is affected by several factors, such as channel characteristics and working fluid types. It is found that there is still limited study that discusses the use of binary mixtures combined with high aspect ratio microchannels. The aim of this study is to investigate the flow fluctuation during flow boiling of binary mixtures in rectangular microchannels. Here, a 6 mm width and 0.3 mm depth rectangular channel was utilised, and it represents a hydraulic diameter of 571 μm and an aspect ratio of 20. In the present works, a mass flux of 10 kg m−2 s−1 was used, and the heat flux ranged from 15.2 and 21.0 kW m−2. The image processing technique was applied to track the bubble tail movement. In addition, the thermal camera was utilised to gather the wall temperature distribution of the channel. The preliminary results show that the use of binary mixtures influences the vapour fraction in the channel and the flow fluctuation characteristics. Some differences are observed in terms of wall temperature characteristics. However, the rapid increase of wall temperature is found in the outlet region for high flux cases under all liquid types which suggests the dominance of dry out event.
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PublicationFinite element modelling of serrated chip formation during turning AZ31 magnesium alloy(IOP Publishing, 2023)Machining metal alloys such as AZ31 magnesium alloy involve thermomechanical behavior between workmaterial and cutting tools. The interaction between workmaterial and cutting tools has affected the chip formation in metal cutting and cutting performance. This paper developed a finite element model (FEM) by using Abaqus software to simulate the chip formation in cutting AZ31 magnesium alloy under dry condition. The study revealed that serrated chips were formed in dry condition. Chip segmentation increased proportionally with cutting speed as generated heat concentrated in a narrow zone, promoting the formation of an adiabatic shear band.
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PublicationDevelopment of variable-line balancing chart by risk assessment using Monte Carlo simulation(IOP Publishing, 2023)Line Balancing Chart is one of the most used lean tools for determining cycle time (CT) and lead time (LT) in the production line processes flow, from raw material input until finished product output. However, for traditional Line Balancing Chart, only the average (mean) CT and LT are considered which causing inconsistent performance of the actual production line throughput rate (productivity). In this study, Variable-Line Balancing Chart (V-LBC) is introduced by considering the dynamic CT and LT in a form of (Minimum, Most Likely (mean), Maximum) for each process involved in the production line. The risk assessment for Value-added (VAA) and non-value added (NVAA) events in the flow are also considered for this V-LBC. A Monte Carlo simulation by using @Risk software is utilized to simulate each process CT distribution capability. As a result, each process in the V-LBC could be represented in horizontal and vertical time variables that involve a variable CT (VAA and NVAA) and risk assessment using Risk Assessment-Failure Mode and Effect Analysis (RA-FMEA) approach. The actual root cause led to the process variation also could be identified more accurately from the V-LBC. Hence the correct action could be taken in order to reduce the variation which indirectly increase the production line productivity.
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PublicationExperimental investigation of coherent and turbulent fluid flow interactions with a circular cylinder(American Institute of Aeronautics and Astronautics, 2023)This paper presents an experimental investigation of the surface pressure induced on a cylinder in laminar and turbulent flows. For the analysis of dynamic surface pressure and coherence, a highly instrumented cylinder with dynamic pressure transducers at various spanwise and peripheral locations was used. Surface pressure results for both laminar and turbulent incident flows show the emergence of the fundamental and its harmonics at most peripheral angles, while the first harmonic dominates the surface pressure spectra at the cylinder base. An increase in turbulence intensity also results in an increase in the energy level of unsteady pressure acting on the cylinder. The velocity-pressure coherence results also revealed the emergence of a strong coherence for both laminar and turbulent incident flows at the vortex shedding frequency, which was contributed by the vortex shedding energy field. Turbulence flow has also reduced, and to some extent eliminated, higher frequency coherence
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PublicationEffect of soaking time towards graphitization of empty fruit bunch (EFB) waste(AIP Publishing, 2023)Empty fruit bunch (EFB) are the second-highest waste produced in the oil palm industry which is 18 022 tonnes in a year. However, the presence of oil palm waste especially from empty fruit bunch (EFB) give a major problem to the disposal. Herein, EFB waste has been identified as a potential carbon source for synthetic graphite production. This is due to implement the lower heating temperature of synthetic graphite produced in controlled heating conditions. Several parameters have been manipulated to study the effect of various parameters on the graphitization process. Hence, in this study, the effect of soaking time towards graphitization of empty fruit bunch (EFB) waste has been investigated. EFB waste was heat treated with various soaking times which is 2 hours, 2.5 hours and 3 hours in controlled heating conditions with constant heating temperature at 500°C and heating rate at 10°/minute After heating treatment, the samples were characterized using X-ray Diffraction (XRD) and analyzed by X'Pert Highscore Plus software. The functional group of synthetic graphite was determined by using Fourier Transform Infrared spectroscopy (FTIR). The morphological study was carried out by using Scanning Electron Microscope (SEM). From the analysis, the best synthetic graphite produced is at the 2.5 hours soaking time with a constant heating temperature at 500°C and a constant heating rate at 10°/min.