Bubble rise phenomena in various non-Newtonian fluids

"The bubble rise characteristic is very important for the design of heat and masss transfer operations in chemical, biochemical, environmental, and food processing industries. The rate of heat and mass transfer is affected by the bubble size, pressure inside the gas phase, interaction between bubbles, rise velocity and rising trajectory. Research on bubble rise phenomena in non-Newtonian fluids is very limited and there is an increased demand for further research in this area since most of the industrial fluids are non-Newtonian in nature. This study investigated the bubble rise phenomena in water (Newtonian fluid) and various non-Newtonian stagnant fluids"--Abstract

Thermofluid Modeling for Energy Efficiency Applications

Thermofluid Modeling for Sustainable Energy Applications provides a collection of the most recent, cutting-edge developments in the application of fluid mechanics modeling to energy systems and energy efficient technology. Each chapter introduces relevant theories alongside detailed, real-life case studies that demonstrate the value of thermofluid modeling and simulation as an integral part of the engineering process. Research problems and modeling solutions across a range of energy efficiency scenarios are presented by experts, helping users build a sustainable engineering knowledge base. The text offers novel examples of the use of computation fluid dynamics in relation to hot topics, including passive air cooling and thermal storage. It is a valuable resource for academics, engineers, and students undertaking research in thermal engineerin

An innovative delivery and assessment of thermofluid engineering : a PBL course in undergraduate engineering program

The intent of project based learning (PBL) in undergraduate engineering courses at Central Queensland University is to expose students to real life engineering problems. Thermofluid engineering a PBL course aims to facilitate students to develop and demonstrate mastery of technical skills required for analysis, formulation and design of the various systems in Thermofluid Engineering. In addition to the technical skills development, this course aims to provide students with opportunities to continue with practice and development of professional skills such as team work, creativity, critical thinking, oral presentation, written communications and lifelong learning skills. Students gain a wide range of exposure to thermofluid engineering with appropriate applications of theory. This paper presents an overview of the course curriculum and innovative techniques used for both delivery and assessment for achieving excellence in research informed teaching and learning processes in thermofluid engineering. It is believed that, from this study (course) students could achieve effective learning techniques and gain advanced knowledge through research informed learning which they could practice in their professional career. The paper focuses on how the outcome of this study will impact on the progressive educational trend in the learning process and will give a better outcome for engineering as a profession

CFD modelling and optimisation of a waste water treatment plant bioreactor: A case study

This study aims to determine the optimal configuration for wall mounted mixers based on the comparison of computational fluid dynamics (CFD) modelling results to physical data collected from the treatment plant. The study was developing a CFD model of an anoxic zone-1 and simulating the fluid flow using ANSYS code ‘Fluent’. A 2D model of an activated sludge process bioreactor anoxic zone was simulated to evaluate the hydrodynamic performance and influence of the inflow through the various inlets. Furthermore, the simulation also sought to evaluate the influence on the hydrodynamic performance from structure geometry. The 2D model was able to simulate the flow pattern within the zone and results from the CFD model varied between 3% and 10% at key locations. A 3D model was also developed of the anoxic zone to further evaluate the hydrodynamic performance. The 3D model produced consistent results to the physical data collected from the plant. The hydrodynamic performance of the anoxic zone was able to be evaluated from the CFD simulations and from the physical samples collected for velocity readings and suspended solids. In the key locations, the CFD simulation showed the consistent results with the physical data. The anoxic zone was subject to velocity lower than the desired 0.3 meters per second. However suspended solid samples suggest that the zone is still within the acceptable range for specific power dissipation. Therefore, an increase in operating parameter which increases the inflow into the zone can mitigate the need for submersible mixers

Technological innovation in aquaculture supply chain: An emerging field of musiness for northern Australia

Aquaculture has been experiencing rapid growth over the last decade both in Australia and overseas. Australia is not self-sufficient in sea food demand and imports about half of domestic consumption from overseas. Aquaculture development is highly dependent on advanced technologies and sophisticated management of the supply chain systems. This paper aims to analyze the different technological innovations required for aquaculture development in northern Australia through some examples from north and far north Queensland. This study found that most technologies are available for large scale aquaculture development but there is scope of further technological innovations for small and medium scale aquaculture farmers in north and far north Queensland

Bubble rise phenomena in non-newtonian crystal suspensions

This chapter presents an experimental study of trajectory and shape of air bubbles and their effect on water, polymeric and massecuite equivalent non-Newtonian crystal suspensions when the bubbles rise. Massecuite is a fluid made from sugar crystals and sugar syrup (molasses) and is an important phase in raw sugar processing where vacuum pan (large cylindrical vessels with steam bubble rising through vertical heating surfaces) is used for sugar crystallisation. To study the bubble rise characteristics and their effect on flow in vacuum pan, various-suspensions were made by using different concentration of xanthan gum solutions with polystyrene crystal particles. The rheological properties for the solutions were measured using an Advanced Rheometric Expansion System (ARES) and the bubble size and bubble trajectory were measured using a combination of non-intrusive-high speed photographic method and digital image processing. A combination of different concentration of xanthan gum solutions with different concentrations of polystyrene crystal mixed with water were tested and characterized for the selection of the massecuite equivalent non-Newtonian fluid. The rheological results indicated that xanthan gum crystal suspensions exhibited shear thinning Power-Law flow behaviour and the solution with a concentration of 0.05% xanthan gum and 1% crystal showed the closest similarities to the rheological properties of massecuite at low shear rate. The viscous effects of the xanthan gum solutions were more pronounced than elastic effects and this phenomenon was observed for a high grade massecuite solution. The loss modulus (G’’) and storage modulus (G’) of crystal suspensions were investigated. The effects of the crystal suspensions on the bubble rise flow characteristics are discussed. In particular, how the bubble trajectory and the bubble shape are affected is reported. Bubble trajectory inside the stagnant liquids in water, polymeric solutions and crystal suspension are investigated corresponding to a 1.0 m height of liquid in the tube. The chapter also delineates the shapes observed in different liquids at three heights of liquid column when bubbles rise.The influences of the dimensionless numbers on the bubble trajectory and shape are reported and verified with the published literature. Particularly, the effect of Reynolds number, Weber Number, and Morton Number, on bubble trajectory are presented and the effect of, Eötvös number, and aspect ratio, E on bubbles’ shapes are described. The conditions for the bubbles’ path and shape oscillations are also identified and discussed

Modeling of bubble flow distribution in crystal suspended non-Newtonian fluids

This paper investigates a computational study of air bubbles rising in massecuite equivalent non-Newtonian crystal suspensions. Bubble rise motion inside the stagnant liquid of 0.05% xanthan gum crystal suspension was investigated and modelled using computational fluid dynamics (CFD) model to gain an insight into the bubble flow distribution. CFD code FLUENT was used for numerical simulation and bubble rise characteristics were computed through a Volume of Fluid (VOF) model. The influences of the Reynolds number (Re) along with other dimensionless groups such the Weber number (We ), and the Eötvös number (Eo) on bubble velocity and bubble trajectory are discussed. The effects of the vortices on bubble velocity distribution are analyzed. The simulated results of the bubble flow contours were validated by the experimental results. The model developed is capable of predicting the entire flow characteristics of different sizes of bubble inside the liquid column

Air bubble trajectories in polymeric solution and crystal suspension

The experimental results of bubble trajectory in xanthan gum solution, xanthan gum crystal suspension and water are presented in this paper. The suspension was made of 0.05% concentration of xanthan gum solution with 1% (by weight) of 0.23 mm polystyrene crystal particle. The characteristic of the air bubble trajectory in these three different liquids is analysed. The influences of the Reynolds number andthe Weber number on bubble trajectory are discussed. The results show that the smaller bubbles (0.1 mL) experienced more horizontal movement in water than in other liquids. On the other hand, larger bubbles (>5mL) produced less spiral motion in water than in other liquids. Conversely, the smaller bubbles (0.1 mL)followed least horizontal motion and larger bubbles (>5mL) produced more spiral motion for crystal suspension. Path instability occurred at the bubbles of 2mL and 5mL and they induced both zigzag and spiral trajectory for all liquids. At low Re and We, smaller bubble produced a zigzag trajectory while larger bubbles (> 5mL) showed a spiral trajectory at high Re and We

Application of thermo-fluid processes in energy systems: Key issues and recent developments for a sustainable future

This book provides essential information on and case studies in the fields of energy technology, clean energy, energy efficiency, sustainability and the environment relevant to academics, researchers, practicing engineers, technologists and students. The individual chapters present cutting-edge research on key issues and recent developments in thermo-fluid processes, including but not limited to: energy technologies in process industries, applications of thermo-fluid processes in mining industries, applications of electrostatic precipitators in thermal power plants, biofuels, energy efficiency in building systems, etc. Helping readers develop an intuitive understanding of the relevant concepts in and solutions for achieving sustainability in medium and large-scale industries, the book offers a valuable resource for undergraduate, honors and postgraduate research students in the field of thermo-fluid engineering

Thermal efficiency modeling in a subtropical data center

This chapter presents a study on examining and improving thermal efficiency of a data center. It reports the development of a computational fluid dynamics (CFD) model for the performance analysis of computer room air conditioners, detailed rack-by-rack inlet and exit temperatures and 3D thermal mapping of the data center and racks. In particular, the model identified the potential high-temperature zone within the computer rack and provided a detailed 3D analysis of how cold air moved through the data center. The study determined the impact on cooling resources such as equipment layout, air flow rate, floor tiles, heat load distribution, and other supplementary cooling strategies. It also proposed temperature estimates for given rack loadings. The developed CFD model can be used to develop cooling strategies for achieving better thermal performance in data centers