Suzairin Seri

Pressure Drop Analysis of Square and Hexagonal Cells and its Effects on the Performance of Catalytic Converters

Stringent emission regulations around the world necessitate the use of high-efficiency catalytic converters in vehicle exhaust systems. Therefore, determining the optimum geometry of the honeycomb monolith structure is necessary. This structure requires a high surface area for treating gases while maintaining a low pressure drop in the engine. In the present paper, an adapted sub-grid scale modeling is used to predict the pressure loss of square- and hexagonal-cell-shaped honeycomb monoliths. This sub-grid scale modeling represents the actual variations in the pressure drop between the inlet and outlet for various combinations of wall thickness and cell density. A comparison is made between the experimental and numerical results established in literature. The present approach is found to provide better and more comprehensive results than the single channel technique.

Fluidization of Geldart Type-D Particles in a Swirling Fluidized Bed

Geldart Type-D particles are often associated with poor fluidization characteristics due to their large sizes and higher densities. This paper reports the hydrodynamics of various Geldart Type-D particles when fluidized in a swirling fluidized bed (SFB). Four different sizes of particles ranging from 3.85 mm to 9.84 mm with respective densities ranging from 840 kg/m3 to 1200 kg/m3 were used as bed material to study the effect of various bed weights (500 gram to 2000 gram) and centre bodies (cone and cylinder) for superficial velocities up to 6 m/s. The performance of the SFB was assessed in terms of pressure drop values, minimum fluidization velocity, Umf and fluidization quality by physical observation on regimes of operation. The swirling fluidized bed showed excellent capability in fluidizing Geldart Type-D particles in contrast to the conventional fluidized beds. The bed pressure drop of increased with superficial velocity after minimum fluidization as a result of increasing centrifugal bed weight. It was also found that the particle size and centre body strongly influence the bed hydrodynamics.

Secondary flow vortices and flow separation of 2-D turning diffuser via particle image velocimetry

It is often necessary in fluid flow systems to simultaneously decelerate and turn the flow. This can be achieved by employing turning diffusers in the fluid flow systems. The flow through a turning diffuser is complex, apparently due to the expansion and inflexion introduced along the direction of flow. In the present work, the flow characteristics of 2-D turning diffuser by means of varying inflow Reynolds number are investigated. The flow characteristics within the outlet cross-section and longitudinal section were examined respectively by the 3-D stereoscopic PIV and 2-D PIV. The flow uniformity is affected with the increase of inflow Reynolds number due to the dispersion of the core flow throughout the outlet cross-section. It becomes even worse with the presences of secondary flow of 22% to 28%. The secondary flow vortices occur almost the same scale at both left and right sides of the outlet. The flow separation takes place within the inner wall region early on half of the inner wall length and is gradually resolved with the increase of inflow Reynolds number.

Assessment of Turbulence Model Performance Adopted Near Wall Treatment for a Sharp 90° 3-D Turning Diffuser

The primary aim of this paper is to assess the performance of k-e turbulence models by means of adopting various near wall treatments to simulate the flow within a sharp 90° 3-D turning diffuser. The Computational Fluid Dynamics (CFD) results were validated quantitatively and qualitatively with the experimental results (using Particle Image Velocimetry (PIV)). The standard k-e adopted curvature correction and enhanced wall treatment of y+ ≈ 1.2–1.7 appears as the best validated model, producing minimal deviation with comparable flow structures to the experimental cases.

Flow behaviour in normal and Meniere's disease of endolymphatic fluid inside the inner ear

Menieres disease is a rare disorder that affects the inner ear which might be more severe if not treated. This is due to fluctuating pressure of the fluid in the endolymphatic sac and dysfunction of cochlea which causing the stretching of vestibular membrane. However, the pattern of the flow recirculation in endolymphatic region is still not fully understood. Thus, this study aims to investigate the correlation between the increasing volume of endolymphatic fluid and flow characteristics such as velocity, pressure and wall shear stress. Three dimensional model of simplified endolymphatic region is modeled using computer aided design (CAD) software and simulated using computational fluid dynamic (CFD) software. There are three different models are investigated; normal (N) model, Menieres disease model with less severity (M1) and Menieres disease model with high severity (M2). From the observed, the pressure drop between inlet and outlet of inner ear becomes decreases as the outlet pressure along with endolymphatic volume increases. However, constant flow rate imposed at the inlet of endolymphatic showing the lowest velocity. Flow recirculation near to endolymphatic region is occurred as the volume in endolympathic increases. Overall, high velocity is monitored near to cochlear duct, ductus reuniens and endolymphatic duct. Hence, these areas show high distributions of wall shear stress (WSS) that indicating a high probability of endolymphatic wall membrane dilation. Thus, more severe conditions of Menieres disease, more complex of flow characteristic is occurred. This phenomenon presenting high probability of rupture is predicted at the certain area in the anatomy of vestibular system.

Numerical study of canister filters with alternatives filter cap configurations

Air filtration system and filter play an important role in getting a good quality air into turbo machinery such as gas turbine. The filtration system and filter has improved the quality of air and protect the gas turbine part from contaminants which could bring damage. During separation of contaminants from the air, pressure drop cannot be avoided but it can be minimized thus helps to reduce the intake losses of the engine [1]. This study is focused on the configuration of the filter in order to obtain the minimal pressure drop along the filter. The configuration used is the basic filter geometry provided by Salutary Avenue Manufacturing Sdn Bhd. and two modified canister filter cap which is designed based on the basic filter model. The geometries of the filter are generated by using SOLIDWORKS software and Computational Fluid Dynamics (CFD) software is used to analyse and simulates the flow through the filter. In this study, the parameters of the inlet velocity are 0.032 m/s, 0.063 m/s, 0.094 m/s and 0.126 m/s. The total pressure drop produce by basic, modified filter 1 and 2 is 292.3 Pa, 251.11 Pa and 274.7 Pa. The pressure drop reduction for the modified filter 1 is 41.19 Pa and 14.1% lower compared to basic filter and the pressure drop reduction for modified filter 2 is 17.6 Pa and 6.02% lower compared to the basic filter. The pressure drops for the basic filter are slightly different with the Salutary Avenue filter due to limited data and experiment details. CFD software are very reliable in running a simulation rather than produces the prototypes and conduct the experiment thus reducing overall time and cost in this study.

Tube Bank with Integral Wake Splitter Performance at Reynolds Number 5000 to 50000

Present study involves experimental and numerical work to investigate the effect of integral wake splitter towards the overall performance of cross-flow, circular tube, heat exchanger system. The experimental work was conducted to obtain local distribution of pressure coefficient around plain tube bank of staggered arrangement which was subjected to a cross-flow of air with Reynolds number of 15950. The numerical work consisted of 2-dimensional unsteady numerical simulation which was validated against the experimental data. The validated numerical approach was utilized to simulate cross-flow around similar tube bank but with integral wake splitter of length-to-diameter ratio of 0.5, 1, 1.5 and 2, at Reynolds number between 5000 to 50000. It is concluded that integral wake splitter is able to reduce pressure loss, which in turn reduces power requirement of a blower, which is intended in effort to increase the system efficiency. Splitter which acts as fin may improve the overall performance of the system by enhancing total heat removal via extended surface provided that certain value of fin efficiency is achieved.