Nabeel Al-Rawahi

A Multisensor Intelligent Device for Real-Time Multiphase Flow Metering in Oil Fields

In this paper, a new multiphase flow metering device for real-time measurement of oil, gas, and water flow rates is presented. It is composed of several electrical and acoustic sensors whose signals are digitalized and processed by a multilayer neural network. This latest uses the physical models of multiphase fluids to reduce the complexity of the parameter space while improving its accuracy. Furthermore, to overcome the uncertainties of the electrical sensors in the range of 40%-60% and above 90% water-cut (i.e., ranges where most of the multiphase flow meter fail), two rings of high- and low-frequency ultrasonic sensors are used for low and high gas fractions, respectively. The results of experiments that have been conducted in an in-house laboratory-scale multiphase flow loop show that real-time classification for up to 90% gas fraction can be achieved with less than 10% relative error.

Computations of Multiphase Flows

Abstract Computational studies of multiphase flows go back to the very beginning of Computational Fluid Dynamics. It is, however, only during the last decade that direct numerical simulations of multiphase flow have emerged as a major research tool. It is now possible, for example, to simulate the motion of several hundred bubbles and particles in simple flows and to obtain meaningful averaged-quantities that can be compared with experimental results. Much of this progress has been made possible by methods based on the ‘one-fluid’ formulation of the governing equations, in addition to rapidly increasing computational power. Here, we review computations of multiphase flows with particular emphasis on finite Reynolds number flows and methods using the ‘one-fluid’ approach. After an overview of the mathematical formulation and the various ‘one-fluid’ methods, the state-of-the-art is reviewed for three problems: Dispersed bubbly flows, microstructure formation during solidification, and boiling. For the first example numerical methods have reached the maturity where they can be used in scientific studies. For the second and third examples, major numerical development is still taking place. However, progress is rapidly being made and it is realistic to expect large-scale simulations of these problems to become routine within a few years.

Applications of Equations of State in the Oil and Gas Industry

Reservoir fluids contain a variety of substances of diverse chemical nature that include hydrocarbons and nonhydrocarbons. Hydrocarbons range from methane to substances that may contain 100 carbon atoms. The chemistry of hydrocarbon reservoir fluids is very complex. In spite of the complexity of hydrocarbon fluids found in underground reservoirs, equations of state have shown surprising performance in the phase-behavior calculations of these complex fluids. An equation of state (EOS) is an analytical expression relating pressure to the volume and temperature. The expression is used to describe the volumetric behavior, the vapor/liquid equilibria (VLE), and the thermal properties of pure substances and mixtures. Numerous EOS have been proposed since Van der Waals introduced his expression in 1873. Currently, a number of EOS are used in reservoir engineering which have shown more reliability in reservoir fluids calculations. In this chapter, a review over the most commonly used EOS in the oil and gas industry has been provided. We explore their strengths and weaknesses and to examine the predictive capability of these equations. A brief introduction to Soave-RedlichKwong (SRK), Peng-Robinson (PR), Patel-Teja (PT), Schmit-Wenzel (SW), and EsmaeilzadehRoshanfekr (ER) equations of state has been provided with intention to compare their efficiency in predicting different reservoir fluids properties. The Progress in developing EOS for the calculation of thermodynamic data and phase behavior is also reviewed. Effect of characterization on VLE predictions as well as advances in application of equations of state for heavy hydrocarbons has been considered in this work. Finally, as a case-study, phase behavior of a typical Omani crude oil as well as application of EOS with proper characterization method for this real oil sample has been examined.

Comparative performance analysis of microjet impingement cooling models with different spent-flow schemes

Nomenclature As = surface area of the substrate base, m 2 d = diameter of the nozzle, m H = height of the channel, m h = heat transfer coefficient,W · m−2 · K−1 k = thermal conductivity,W · m−1 · K−1 lx, ly, lz = length, width, and height of the silicon substrate, respectively, m N = number of observation for calculating mean value n = number of jets P = pumping power, W p, Δp = pressure and pressure drop, respectively, Pa Q = volume flow rate, m · s−1 q = heat flux, W · m−2 Rth = thermal resistance, K · W −1 T, ΔT = temperature and temperature rise, respectively, K ts = thickness of the substrate base, m V = velocity vector, m · s−1 x, y, z = orthogonal coordinate system ρ = density, kg · m−3 σ = standard deviation, K

Development of bioclimatic chart for passive building design

The selection of building passive thermal design strategies is based heavily on the local climatic conditions. Identifying the best strategy for a given location can be made using bioclimatic charts. Such charts depend on the atmospheric pressure and are commonly available at sea level. Moreover, manual usage of these charts is cumbersome and time-consuming. In this work, the development of a bioclimatic chart for Muscat, as a case study, is described using Givonis zones in rigorous detail based on typical meteorological year (TMY) data. A generic calculation tool that generates the psychrometric chart for any altitude has been developed using MATLABTM, the procedure described herein, can be imitated on most scripting languages for any location using its atmospheric pressure and TMY data.

Direct Numerical Simulations of Flows With Phase Change

During the last decade, direct numerical simulations of multiphase flow have emerged as a major research tool. It is now possible, for example, to simulate the motion of several hundred bubbles and particles in simple flows and to obtain meaningful average quantities that can be compared with experimental results. These systems are, however, still very simple compared to those systems routinely encountered in engineering applications. It is, in particular, frequently necessary to account for phase change, both between solid and liquid as well as liquid and vapor. Most materials used for manmade artifacts are processed as liquids at some stage, for example, and the way solidification takes place generally has major impact on the properties of the final product. The formation of microstructures, where some parts of the melt solidify faster than others, or solidify with different composition as in the case of binary alloys, is particularly important since the size and composition of the microstructure impact the hardness and ductility, for example, of the final product. Boiling is one of the most efficient ways of removing heat from a solid surface. It is therefore commonly used in energy generation and refrigeration. The large volume change and the high temperatures involved can make the consequences of design or operational errors catastrophic and accurate predictions are highly desirable. The change of phase from liquid to vapor and vice-versa usually takes place in a highly unsteady manner with a very convoluted phase boundary. Numerical simulations are therefore essential for theoretical investigations and while a few simulations of both problems have been published, the field is still very immature. In the talk the author gives a brief overview of the state of the art and discusses recent simulations of boiling and solidification in some detail. The progress made during the last few years in simulating the motion of multiphase flows without phase change has relied heavily on the so-called “one-fluid” formulation of the governing equations. In this approach one set of equations is written for all the phases involved. The formulation allows for different material properties in each phase and singular terms must be added at the phase boundaries to correctly incorporate the appropriate boundary conditions. The key challenge is to correctly advect the phase boundary and a number of methods have been proposed to do so. Those include the Volume-Of-Fluid (VOF), the level-set, the phase field methods, as well as front-tracking methods where the boundary is explicitly tracked by connected marker points [1]. The last approach, front tracking, has been particularly successful and is used for the examples shown here. In both boiling and solidification it is necessary to solve the energy equation, in addition to conservation equations for mass and momentum, and account for the release/absorption of latent heat at the phase boundary. The latent heat source also determines the motion of the phase boundary relative to the fluid. In boiling there is significant volume expansion as liquid is transformed into vapor and this expansion must be accounted for in the mass conservation equation. For solidification the volume expansion can often be neglected, but the transformation of the liquid into a stationary solid poses new computational challenges. An example of a bubble undergoing vapor explosion is shown in figure 1. The bubble is initially started as a small nearly spherical sphere in superheated liquid confined in a domain that is periodic in two directions, with a solid wall at the bottom and open on the top to allow outflow as the bubble expands. In this case the domain is resolved by a 643 grid. As the bubble grows, the interface becomes unstable, developing a corrugated shape (usually referred to experimentally as a “black bubble” since the corrugated surface is opaque). The increase in surface area greatly affects the growth rate of the bubble. Figure 2 shows one example of a simulation of the growth of a dendrite of pure material in uniform flow. The domain is a square resolved by a 2563 grid. A uniform inflow is specified on the left boundary, the top and bottom boundaries are periodic, and all gradients are set to zero at the outlet boundary. The temperature of the incoming flow is equal to the undercooled temperature and as latent heat is released at the phase boundary, the flow sweeps it from the front to the back. This results in a thinner thermal boundary layer at the tip of the upstream growing arm and a relatively uniform temperature in the wake. The growth rate of the upstream arm is therefore enhanced and the growth of the downstream arm is reduced.Copyright

Teaching product design in line with Bloom's taxonomy and ABET student outcomes

Design is one of the highest-level activities in the engineering profession. Compared to many other areas predominantly involving closed-form solutions, design is an open-ended activity, with many possible solutions for the same problem. This shift from the concrete to the abstract makes teaching of engineering design courses more challenging. The target set forth by good academic institutions is to have a system in place that can produce graduates who are well equipped and suitably qualified to practice professional engineering in a continually changing and increasingly complex global environment. Blooms taxonomy outlines the skill levels required for education at any level, and in any discipline. Accreditation agencies such as ABET also establish criteria that can be generally applied to any type of education, but are primarily focused on engineering education. The current paper describes a methodology for Product Design education, integrating both Blooms taxonomy and ABET student outcomes in an activity-based environment. Creative Design course taught at the Mechanical Engineering Department at Sultan Qaboos University, Muscat is presented as a case study. Example design activities are described for each of the six levels in Blooms taxonomy. A mapping table is also presented to relate these levels to student outcomes of ABET criterion.

Investigation on the effectiveness of an innovative airfoil-type degasser

ABSTRACT A framework to analyze the fluid mechanisms in baffle type degassers is presented and particularly applied to an innovative airfoil-type degasser. Major fluid events in conventional baffle type degassers such as bubbles rising inside the oil layer and the flow of the oil layer itself were taken into account. However, in the current airfoil-type degasser oil flows over an airfoil surface and at the same time is exposed to an air jet. This air jet attaches to the airfoil surface due to the so called Coanda effect as observed in some trial runs of the system. A curved strip model is suggested to estimate the pressure reduction due to the jet curvature. Then we have performed a convective mass transfer analysis in order to determine the jet effect in reducing the partial pressure of the gas on the oil surface and increasing the rate of bubble formation.

Investigating different diffuse solar radiation models to analyse solar radiation on inclined surfaces in Oman

In this paper, a detailed analysis of the solar radiation on horizontal and tilted surfaces for six locations in Oman is presented. The locations are (from North to South): Majis/Sohar, Sur, Fahud, Masira, Marmul, and Salalah. These locations spread over Oman and cover different types of landscape. The method is validated through the use of measured data. The effect of tilt angle and orientation on the incident solar radiation is presented along with optimum surface tilt angles and directions for maximum solar radiation collection in these six locations. The solar radiation models used in this paper show good agreement with measured data. The results presented in this paper are extremely useful for quick estimation of solar radiation for calculations of buildings’ cooling load and solar collector system performance. This can be easily extended for other locations with similar landscapes and geographical conditions.

Achieving the Zero-Liquid-Discharge Target Using the Integrated Membrane System for Seawater Desalination

Membrane desalination technology has emerged in recent years as the most viable solution to water shortage. However, despite the enormous improvement in membrane desalination technology, some critical developments are still necessary in order to accomplish possible improvements in the process efficiency (to increase recovery), operational stability (to reduce fouling and scaling problems), environmental impact (to reduce brine disposal), water quality (to remove harmful substances) and costs. In particular, cost- effective and environmentally-sensitive concentrate management is today recognized as a significant obstacle to extensive implementation of desalination technologies. As a result of the significant impact of desalination plants on the environment, the requirements for concentrate management are brine disposal minimization and zero liquid discharge (ZLD), both being the demanding targets for several applications. Conventional pressure-driven membranes such as MF, NF and RO were integrated with the innovative units of membrane contactors such as Membrane Distillation/Crystallization (MD/MC). The integration of different membrane units represents an interesting way for achieving the ZLD goal due to the possibility of overcoming the limits of the single units, thus improving the performance of the overall operation.