S. Al-Hiddabi

Modeling and performance analysis of a solar desalination unit with double-glass cover cooling☆

Abstract In this study, modeling and performance analysis of a single-basin solar still with the entering brine flowing between a double glass glazing is investigated. The base area of the solar still is 1 m2. The function of this arrangement is two-fold; lowering the glass temperature and preheating the entering brine. This resulted in improved performance represented by a faster rate of evaporation from the basin. The efficiency of the double-glass desalination unit increased by over 25% compared with the conventional single-basin single-glass solar still. The hourly and daily productions of the unit and the temperatures of the water and the glass cover were also predicted under the meteorological conditions of Muscat, Oman.

Quadrotor control using feedback linearization with dynamic extension

The contribution of this paper is the development of a nonlinear position controller for a quadrotor VTOL aircraft using feedback linearization with dynamic extension. The developed controller completely decouples and linearizes the nonlinear dynamical model of the aircraft. The use of dynamic extension has resulted into a fourteenth dimensional controller for the the twelve dimensional state system. Simulation results are provided to demonstrate the effectiveness of the nonlinear controller in tracking time-parameterized trajectories in inertial frame with internal stability.

Mechanical Testing and Characterization of a Swelling Elastomer

Elastomers are being increasingly used for sealing and other applications in the oil and gas industry. Specifically developed elastomers possess durable properties and have the ability to withstand detrimental effects of heat, chemicals, and harsh environments. For successful modeling and simulation of various downhole processes, it is very important to determine the behavior of elastomer materials under realistic well conditions. Of special interest is the class known as swelling elastomers. This article reports some results from experiments conducted on mechanical testing and characterization of an inert (nonswelling) and a water-swelling elastomer (both belonging to the EPDM family) used for sealing purposes by a local petroleum development firm. Experiments were designed and conducted in accordance with standard ASTM test methods. Apart from regularly available testing equipment, some simple test rigs and fixtures were designed and fabricated. Elastomer behavior was tested for hardness, compression set (at different temperatures and for different periods of time), tensile set (for different periods of time), tensile properties (fracture strength and percent elongation), and swelling. In the swelling test, different sample geometries (unconfined samples and samples mounted on steel plate) were tested for a total duration of 1000 h (roughly 45 days) in salt solutions of different concentrations and at different temperatures. Results show that compression set increases with increasing temperature and testing time, while room temperature tensile set also increases with longer testing time. Compared to the inert elastomer (exhibiting nonlinear elastic behavior like normal rubbers), swelling elastomer surprisingly showed linear stress—strain response. As expected, the inert elastomer did not exhibit any change in volume, while the swelling elastomer showed significant volume/thickness increase with increasing test temperature and decreasing salt concentration.

Structural behavior of a solid tubular under large radial plastic expansion

The theory of metal forming has been used to study the mechanical response of a solid tubular under radial plastic expansion. A mathematical model of an expanded thin walled tube under compression has been developed in this paper. The study showed that as the friction coefficient and mandrel angle increase the drawing force and induced stresses increase. However, the final tube thickness and length were found to decrease with an increase in both parameters.

Tubular expansion in irregularly shaped boreholes - Computer simulation and field measurement

Abstract Abstract Recently, field engineers have tried to use a new technique using expandable tubular with elastomers to seal the annulus. Ultrasonic down-hole measurements carried out for evaluation of zonal isolation revealed that the tubular expanded to an oval x-section instead of the desired circular x-section at certain locations. This is a phenomenon previously unknown. It is believed to occur due to expansion in irregularly shaped boreholes. The ovalization of expanded tubular was studied to avoid such problems in future. The finite element method was used to predict tubular ovality and compare it to measured values. Results were then used to develop ready-to-use design curves in making decisions for running a completion tool in expanded tubular.

Dynamic effects of mandrel/tubular interaction on downhole solid tubular expansion in well engineering

The expansion process subjects a solid tubular to large plastic deformations leading to variations in tubular thickness and length, which may result in premature and unexpected failures. It was noticed that the expansion process induces wall thickness imperfections due to excessive local plastic deformation as a result of mandrel sticking and slipping relative to the expanded tubular; such irregularities increase the probability of failure. Mandrel sticking may be the result of lack of enough lubrication, tubular surface irregularities, and the presence of welded and/or threaded connections, which require higher drawing force to push the mandrel forward. When the drawing force required to overcoming the maximum static friction and the mandrel forward motion is assured, the mandrel slips relative to the expanded tubular. This “stick-slip” phenomenon results in mandrel oscillations that affect the tubular response in terms of further reduction in thickness and may jeopardize the tubular capacity under normal operating field conditions. Therefore, the present work studies the mandrel dynamics and their effect on the tubular structural response. A mathematical model, which is an extension of the quasistatic tubular expansion analysis, has been developed to describe the dynamic friction effects of the stick-slip phenomenon. A special case of tubular expansion consisting of 25% expansion ratio of a 4/12 in. liner hanger was considered. It was found that the level of mandrel oscillations is in the order of 1–2 mm around its equilibrium position resulting in tubular thickness reduction of approximately 9% on top of its variation caused by the steady state expansion process. This increase in thickness reduction may affect the postexpansion collapse strength of the tubular. DOI: 10.1115/1.3066412

Stress/Fluid Pressure Waves in Radially Expanded Solid Tube

Solid Expandable Tubular (SET) Technology is receiving a widespread use in the oil industry nowadays. This technology is essentially a down-hole cold working process consisting of expanding a solid tube by drawing a mandrel through it either mechanically or hydraulically. The hydraulic expansion requires a high back pressure to move the mandrel forward, which leads to a sudden release (pop-out) of the mandrel towards the end of the process due to the stored elastic energy within the tube-fluid system. This sudden release results in axial and radial vibrations accompanied with stress and pressure waves propagating through the three mediums (inner and outer fluids and expanded tube). In the present paper, a mathematical model describing the dynamics of the three mediums has been developed. A specific case of a 127 mm tube in a 340 mm borehole with fluids of different properties inside and outside the tube was considered. The coupling effect describing the fluid-structure interaction resulted in modifications of the waves speeds and frequencies as compared to uncoupled solutions. The study also focused on the effects of stress and fluid pressure waves on the structural integrity of the expanded tube. It was noticed that the maximum vibration occurs at the free end of the tube. In addition, the model identified potential locations along the tube, which may experience collapse.Copyright