Effects of baffles on flow distribution in an electrostatic precipitator (ESP) of a coal based power plant

Electrostatic Precipitators (ESP) are the most reliable and industrially used control devices to capture fine particles for reducing exhaust emission. Its efficiency is 99% or more. However, capturing submicron particles which are hazardous is still a problem as it involves complex flow phenomena and ESP design limitations. In this study, the effect of baffles on flow distribution inside the ESP is investigated computationally. Baffles are expected to increase the residence time of flue gas which helps to collect more particles into the collector plates, and hence increase the collection efficiency of an ESP. Besides, the placement of a baffle is likely to cause swirling of flue gas and hence sub-micron particles move towards the collector plate due to eccentric and electrostatic force. Therefore, the effects of position, shape and thickness of the baffles on collection efficiency which are also important for ESP design are reported in this study. The fluid flow distribution has been modelled using computational fluid dynamics (CFD) software Fluent and the result and outcome are presented and discussed. The result shows that baffles have significant influence on fluid flow pattern and the efficiency of ESP.

Energy saving in electric heater of carbon fiber stabilization oven

Carbon fiber is an advanced material with high tensile strength and modulus, ideally suited for light weight applications. Carbon fiber properties are directly dependent on all aspects of production, especially the process step of thermal stabilization. Stabilization is considered to be one of the most critical process steps. Moreover, the stabilization process is the most energy consuming, time consuming and costly step. As oxidation is an exothermic process, constant airflow to uniformly remove heat from all tows across the towband is indispensable. Our approach is to develop an intelligent computational system that can construct an optimal Computational Fluid Dynamics (CFD) solution. In this study, an electrical heater has been designed by CFD modeling and intelligently controlled. The model results show that the uniform airflow and minimum turbulence kinetic energy can be achieved by combining intelligent system technology with CFD analysis strategy.

Effect of materials on the urban thermal environment a CFD simulation approach

Use of high albedo materials reduces the amount of solar radiation absorbed through building envelops and urban structures and thus keeping their surfaces cooler. The cooling energy savings by using high albedo materials have been well documented. Higher surface temperatures add to increasing the ambient temperature as convection intensity is higher. Such temperature increase has significant impacts on the air conditioning energy utilization in hot climates. This study makes use of a parametric approach by varying the temperature of building facades to represent commonly used materials and hence analyzing its effect on the air temperature through a series of CFD (Computational Fluid Dynamics) simulations. A part of the existing CBD (Central Business District) area of Singapore was selected for the study. Series of CFD simulations have been carried out using the software CFX-5.6. Wind tunnel experiments were also conducted for validation. It was found that at low wind speeds, the effect of materials on the air temperature was significant and the temperature at the middle of a narrow canyon increased up to 2.52°C with the façade material having lowest albedo.

Tow testing of Savonius wind turbine above a bluff body complemented by CFD simulation

A simple way to improve its power coefficient (cp) of a Savonius turbine is by its installation above a cuboidal building as the building will redirect the wind and increase its speed significantly. To determinethe gain, a turbine was constructed and installed above a bluff body and tow tested. Detailed measurements of vehicle speed and turbine power were made. Tow test speeds were 8, 10 and 12 m/s, while TSR range was 0.6-1.1. Most importantly, wind speed at the position beside and slightly above the turbine was measured during test runs. The cp calculated using this measured wind speed was used to validate CFD simulation results. Simulation results were also used to obtain the relationships between the wind speed of the free stream and at the anemometer position. Typically, wind speed at the anemometer position is about 9% higher than those of the free stream. These relationships were used to derive the free stream wind speed of each experimental run. The cp calculated using these derived free stream wind speeds showed an increase of 25% at 12 m/s wind speed, compared to the cp reported by previous researchers for a similar turbine operating in unmodified air flow.

Mixing characterisation for a serpentine microchannel equipped with embedded barriers

This paper describes the design, simulation, fabrication and experimental analysis of a passive micromixer for the mixing of biological solvents. The mixer consists of a T-junction, followed by a serpentine microchannel. the serpentine has three arcs, each equipped with circular barriers that are patterned as two opposing triangles. >The barriers are engineered to induce periodic perturbations in the flow field and enhance the mixing. CFD (Computational Fluid Dynamics) method is applied to optimise the geometric variables of the mixer before fabrication. The mixer is made from PDMS (Polydimethylsiloxane) using photo- and soft-lithography techniques. Experimental measurements are performed using yellow and blue food dyes as the mixing fluids. The mixing is measured by analysing the composition of the flow's colour across the outlet channel. The performance of the mixer is examined in a wide range of flow rates from 0.5 to 10 µl/min. Mixing efficiencies of higher than 99.4% are obtained in the experiments confirming the results of numerical simulations. The proposed mixer can be employed as a part of lab-on-a-chip for biomedical applications.

Fluid mixing in droplet-based microfluidics with a serpentine microchannel

The hydrodynamics and mixing process within droplets travelling along a three dimensional serpentine microchannel are studied using a computational fluid dynamics simulation based on the volume-of-fluid approach. The fluid mixing within the droplet follows symmetric circulations in the straight section, which generates axial mixing. In the winding section, the asymmetric circulations lead to the reorientation of the fluids within the droplet, thus enhancing the mixing efficiency. The mixing performance is controlled by the spatial distribution of the mixing components and the circulation period within the droplet. The best mixing occurs when the droplet size is comparable with the channel width. When the droplet size is less than two times the channel width, the asymmetric circulations make it easy for the fluid to distribute in the axial direction, which leads to a fast mixing process. For larger droplets, the long circulation period becomes more significant, which causes lower mixing efficiency.

Data mining analysis of an urban tunnel pressure drop based on CFD data

An accurate estimation of pressure drop due to vehicles inside an urban tunnel plays a pivotal role in tunnel ventilation issue. The main aim of the present study is to utilize computational intelligence technique for predicting pressure drop due to cars in traffic congestion in urban tunnels. A supervised feed forward back propagation neural network is utilized to estimate this pressure drop. The performance of the proposed network structure is examined on the dataset achieved from Computational Fluid Dynamic (CFD) simulation. The input data includes 2 variables, tunnel velocity and tunnel length, which are to be imported to the corresponding algorithm in order to predict presure drop. 10-fold Cross validation technique is utilized for three data mining methods, namely: multi-layer perceptron algorithm, support vector machine regression, and linear regression. A comparison is to be made to show the most accurate results. Simulation results illustrate that the Multi-layer perceptron algorithm is able to accurately estimate the pressure drop.

Parallel I/O scheduling in the presence of data duplication on multiprogrammed cluster computing systems

The widespread adoption of cluster computing as a high performance computing platform has seen the growth of data intensive scientific, engineering and commercial applications such as digital libraries, climate modeling, computational chemistry, computational fluid dynamics and image repositories. However, I/O subsystem performance has not been keeping pace with processor and memory performance, and is fast becoming the dominant factor in overall system performance.  Thus, parallel I/O has become a necessity in the face of performance improvements in other areas of computing systems. This paper addresses the problem of parallel I/O scheduling on cluster computing systems in the presence of data replication.  We propose two new I/O scheduling algorithms and evaluate the relative performance of the proposed policies against two existing approaches.  Simulation results show that the proposed policies perform substantially better than the baseline policies.

Integrated optimization system for high pressure die casting processes

High pressure die casting (HPDC) is a versatile process for producing engineered metal parts by forcing molten metal under high pressure into reusable steel dies. However there are a large number of attributes involved which contribute to the complexity of the process. A novel integrated approach is developed to optimize the high pressure die casting processes. The die temperature profiles will be studied with infrared thermograph technology and the internal cooling system will be optimized to provide even cooling to the components and the die. The heat stored in the die and the components is studied with image processing. Based on the geometrical profile of the components, cooling channels can be redesigned to improve the cooling efficiency while the cooling time is reduced. This will not only significantly improve the quality of the castings but also improve the productivity of the process.

Transient fluid–structure coupling for simulation of a trileaflet heart valve using weak coupling

In this article, a three-dimensional transient numerical approach coupled with fluid–structure interaction for the modeling of an aortic trileaflet heart valve at the initial opening stage is presented. An arbitrary Lagrangian–Eulerian kinematical description together with an appropriate fluid grid was used for the coupling strategy with the structural domain. The fluid dynamics and the structure aspects of the problem were analyzed for various Reynolds numbers and times. The fluid flow predictions indicated that at the initial leaflet opening stage a circulation zone was formed immediately downstream of the leaflet tip and propagated outward as time increased. Moreover, the maximum wall shear stress in the vertical direction of the leaflet was found to be located near the bottom of the leaflet, and its value decreased sharply toward the tip. In the horizontal cross section of the leaflet, the maximum wall shear stresses were found to be located near the sides of the leaflet.

Dielectrophoretic manipulation and separation of microparticles using curved microelectrodes

This paper presents the development and experimental analysis of a dielectrophoresis (DEP) system, which is used for the manipulation and separation of microparticles in liquid flow. The system is composed of arrays of microelectrodes integrated to a microchannel. Novel curved microelectrodes are symmetrically placed with respect to the centre of the microchannel with a minimum gap of 40 mm. Computational fluid dynamics method is utilised to characterise the DEP field and predict the dynamics of particles. The performance of the system is assessed with microspheres of 1, 5 and 12 mm diameters. When a high-frequency potential is applied to microelectrodes a spatially varying electric field is induced in the microchannel, which creates the DEP force. Negative-DEP behaviour is observed with particles being repelled from the microelectrodes. The particles of different dimensions experience different DEP forces and thus settle to separate equilibrium zones across the microchannel. Experiments demonstrate the capability of the system as a field flow fraction tool for sorting microparticles according to their dimensions and dielectric properties.

Coupled modelling of hydrodynamics and mass transfer in membrane filtration

This research produced a novel predictive computational model for the water treatment processes of nanofiltration and reverse osmosis. This model combined commercial computational fluid dynamics codes with numerical mass transfer models developed by the candidate to provide a rigorous description of these processes’ hydrodynamic and pollutant removal behaviour.

3D locomotion biomimetic robot fish with haptic feedback

This thesis developed a biomimetic robot fish and built a novel haptic robot fish system based on the kinematic modelling and three-dimentional computational fluid dynamic (CFD) hydrodynamic analysis. The most important contribution is the successful CFD simulation of the robot fish, supporting users in understanding the hydrodynamic properties around it.