Measurement of properties of a dispersed phase in air-water multiphase flow using novel four-sensor probe and orthogonal high speed cameras

Measurement of the volumetric flow rate of each of the flowing components in multiphase flow is required to be monitored in production logging applications. Thus, an increasing level of interest has been shown by researchers worldwide in making flow rate measurements in multiphase flow accurate to a high level. A new generation of tomographic instruments, which enable the measurement of the instantaneous local velocity vector and the instantaneous local volume fraction of the dispersed phase, are now being introduced. However validation and calibration of such instruments is very important to enable quality assured measurements. This paper introduces a camera based calibration system for local 4-sensor probes which can be used to quantify the bubble-probe interaction and the accuracy with which the probe can measure velocity vector, for air bubbles in water and oil droplets in wate

Condition Based Monitoring of Vertical Axis Wind Turbines using Computational Fluid Dynamics

Scarcity of fossil fuels and a rapid escalation in the fuel prices around the world recently has lead the search for alternative energy sources. Out of the available energy sources, wind is being considered as the prime next generation energy source. The fundamental principle of wind turbines is to convert the wind energy into first mechanical and then into electrical form. The relatively simple operation of such turbines has stirred the researchers to come up with innovative designs for global acceptance and to make these turbines commercially viable. Furthermore, the maintenance of wind turbines has long been a topic of interest. On-line health monitoring of wind turbines is essential to maintain continuous operation of wind turbines. The present work focuses on the difference in the outputs of a vertical axis wind turbine (VAWT) under different operational conditions. A Computational Fluid Dynamics (CFD) technique has been used to monitor various blade conditions of a VAWT. The results indicate that there is significant degradation in the performance output of wind turbines as the number of blades broken or missing from the VAWT increases. The study predicts the faults in the blades of VAWTs by monitoring its output

Flow diagnosis in a domestic radiator

In UK, domestic heating contributes to about 40% of annual energy consumption. Effective and efficient heating systems are essential to drive the cost of heating down. Although there are several types of heating systems, radiators are the most popular heat emitters. Head loss in a radiator depends on various design parameters based on fluid flow path conditions and design of the radiator. In the present study, a computational fluid dynamics (CFD) code has been used to analyse flow distribution within a domestic radiator. For this study a radiator with dimensions of 300mm by 600mm with 18 columns has been considered. The study has been carried out on a radiator with BBOE and BTOE configuration at various flow rates. In this paper results are presented from a series of analysis in which flow structure within the radiator has been diagnosed

Effect of the shape of connecting pipes on the performance output of a closed-loop hot water solar Thermo-syphon

In order to conserve the environment from pollution, which is caused by the use of the fossil fuels, numerous research works have been carried out in renewable energy area to minimize the dependency on the fossil fuels. There are several energy sources naturally available, and solar energy is considered to be the best amongst them. Therefore it became a motivating area for the researchers in recent years. Thermo-syphon is one of many devices that use solar energy for power generation. Thermo-syphon converts solar energy into internal energy of the working fluid; mainly water. In this work, a computational fluid dynamics (CFD) code has been used to analyse the natural convection phenomenon in a thermo-syphon. The thermo-syphon model consist of steel pipes with an internal diameter of 25mm, along with a condenser having diameter equal to five times the pipe’s diameter, has been considered. The study has been carried out under no-loading conditions, for two thermo-syphon models comprising of straight and helical shaped pipes of 10, 20 and 30. A practical solar heat flux of 500W/m2 has been applied on the pipes. The numerical results depict that the working fluid within the condenser, in case of helical pipes, gains higher temperature as compared to the straight pipes. Furthermore, increase in the number of helical pipes has negligibly small effect on the temperature of the fluid within the condenser, and hence on the performance output of the thermo-syphon

Flow diagnostics

The measurement of flow properties within fluid handling systems is of utmost importance for efficient operation and control of such systems. For single phase flow systems, extensive research has been carried out world over to diagnose the flow properties both globally and locally. Considerable advancements are being made to perfect these technologies. For multiphase flows there is still a lot of scope for technological development that needs to take place to diagnose the flow conditions accurately efficiently and effectively. In this present paper two methods are described that can be used effectively for measurement of flow properties in solid-liquid flows and gas-liquid flows. One of the methods relies on isokinetic sampling used in conjunction with impact probe for the determination of solid distribution and solid velocity in solid-liquid flows through a pipeline. The other method relies on electrical resistance method to calculate local flow velocity corresponding to the dispersed phase as well as volume fraction and interfacial area concentration

Measurement of bubble velocity vectors in bubbly air water multiphase flow

Measurement of the volumetric flow rate of each of the flowing components in multiphase flow is often required and this is particularly true in Production Logging applications. Thus, an increasing level of interest has been shown in making flow rate measurements in multiphase flow. A new generation of tomographic instrument, which enables measurement of the instantaneous local velocity vector and the instantaneous local volume fraction of the dispersed phase, is now being introduced. However validation and calibration of such instruments is necessary. This thesis describes the development of a miniaturised local four-sensor conductivity probe capable of acquiring measurements of the local velocity vector, gas volume fraction and the local axial gas velocity in the bubbly gas-liquid flows. Experimental techniques in which the probe was used to obtain the local gas velocity vector and the local gas volume fraction in a bubbly gas-liquid flow are also described. High speed cameras are introduced for the measurement of the reference velocity of the bubbles. The camera images are also used to plot the trajectory of any bubble that hits all four-sensor of the probe. Extensive experimental results showing the distribution of the local gas volume fraction and the local axial, azimuthal and the radial bubble velocity components in vertical and swirling gas-liquid flows are presented.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Remote Teaching in Nepalese Higher Education During COVID-19: Teachers\u27 Perspectives

Objectives: The purpose of the study was to examine the factors that supported or inhibited teacher participation in remote teaching. Teaching and learning in Nepal was predominantly face-to-face prior to the pandemic, and the previous studies showed that the use of educational technology in higher education was limited. Method: This exploratory case study draws on data derived from focus group discussions with teachers in higher education. Thematic analysis was employed to explore the impacts of different factors in sudden transition to remote teaching. Findings: Findings show that personal factors such as teachers’ sense of duty and their attitude towards technology use facilitated their practice despite technological (internet connection), organizational (directives on exams or online classes) and environmental (inconsistent power supply) issues. Implication for Theory and/or Practice: Continued uptake of technology by teachers and colleges and universities should be practiced to move education towards a blended approach to teaching and learning. Educational authorities should provide more explicit guidelines on teaching and learning and administration of assessments across multiple situations, including pandemics and other emergencies requiring higher education to pivot. Conclusion: COVID-19 has sped up technology uptake and integration in higher education in Nepal. It increased awareness of technology and encouraged teachers to enhance their skills to integrate technology into learning

Numerical studies of the velocity distribution within the volute of a centrifugal pump

Centrifugal pumps play an essential role in engineering systems since they are widely used in the process and power industries. The performance of a centrifugal pump needs to be maximised due to its importance and this depends on the flow structure within the pump. The flow structure within a pump is very complex due to the presence of a rotating impeller and its interaction with the volute casing. In this paper, a numerical investigation using CFD analysis has been carried out to determine the effect of volute geometry on the flow field within a centrifugal pump. The results obtained from the numerical investigation have been validated with the experimental data. Further analyses have been carried out to investigate the effect of volute cross-sectional area on the velocity distribution. The overall results indicate that the head increases as the volute cross-sectional area increases

Does the Vacuum Gravitate on Microscopic Scales? Rydberg Atoms Indicate Probably Not

The cosmological constant presents one of the most fascinating and confounding problems in physics. A straightforward, seemingly robust prediction of quantum mechanics and general relativity is that the vacuum energy gravitates. Therefore, the cosmological constant should be enormous. It is minuscule. Since there is no understanding of why the cosmological constant is so small, it is important to test this idea in many different situations. In particular, given the span of distances in astronomy and particle physics, it is vital to test the gravitation of vacuum energy on as many distance scales as we can. Rydberg atoms open up a new set of distances for exploration. It is satisfying to measure the cosmological constant with an atom, but its main significance is extending measurements to microscopic distances. Here, too, there is no evidence of the gravitation of the vacuum. At scales of a micron and less, we place a limit of $7$ GeV on the scale of gravitating vacuum energy, well below the scale of $100$ GeV of the SM of particle physics.Comment: Accepted in PR

An Investigation on Ventilation Air Distribution within Rectangular and Circular Enclosures

One of the important parameters that dictate the effectiveness of ventilation system is air change rate. The air change rate provides overall effectiveness of ventilation in an enclosed space and it needs to be examined with age of air particles to decide about overall effectiveness. Age of air particles is the time air at a location spends inside the enclosure and hence provides useful information about presence of secondary flows. A range of tools have been used to predict local and global effectiveness of a typical ventilation system for a specific work environment. Computational fluid dynamics has proven to be an effective tool in this regard. The present work highlights various issues needed to keep in consideration while designing meeting rooms in busy manufacturing environments. Two meeting room configurations have been proposed and ventilation requirements for these enclosures have been estimated. Furthermore for two different fan configurations, interior enclosure conditions have been predicted