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Paraffin wax deposition is the most frequent flow assurance problem in oil production fields. It disrupts stable oil production, and a considerable amount of time and money are spent ameliorating on-site problems. To prevent and mitigate paraffin wax deposition, it is necessary to proactively identify the conditions under which paraffin wax is deposited. Furthermore, monitoring and detection techniques are required to determine the efficacy of the technical measures applied. This study proposes a method based on acoustic velocities obtained by ultrasonic monitoring and detection to estimate the following three temperature elements: (1) wax appearance temperature of oil containing paraffin wax, (2) temperature at which the growth of paraffin wax deposits is activated, and (3) temperature at which the paraffin wax deposits begin to age. An experimental system comprising an ultrasonic transducer and a temperature sensor were set up, and the temperature gradient of the analyzed fluid sample was controlled by continuously circulating an isothermal fluid. Based on real-time monitoring, data measurements were made, and variations in the acoustic velocity of fluid samples were measured. A paraffin wax deposition experiment was conducted using synthetic waxy oil samples with paraffin solid contents of 5 wt.% and 15 wt.%, respectively. Q-factors were calculated based on the spectral ratio method, and wavelet characteristics were analyzed according to temperature changes, to estimate wax appearance temperature. Results show that the method proposed in this study estimates wax appearance temperature in a similar measurement range as conventional methods and enables the life cycle of paraffin wax deposition to be determined through monitoring and detection.

Offshore plant designs can be broadly categorized into hull-type designs and topside module-type designs. Compared to the hull-type design, it is much more difficult to design the topside moduletype design due to the complexity of its structure, making the design technology of professional engineering companies critical. A heave compensation system is a system that compensates the vertical shock imposed on a drilling ship by waves, and is installed at the top of the topside module. Most researchers have used a mathematical model to investigate the analysis of the heave compensation system. This study will conduct a structural analysis using finite element software called Ansys to design a heave compensator that reduces the weight and secures the structural stability, and will derive the ideal design through an optimization process that utilizes the response-surface method and the Kriging model.

As petroleum technology has developed, both slim-hold and directional drillings have developed as well. Although these techniques are currently being utilized in industry, the literature on them is still insufficient. In the present study, the friction coefficient, pressure loss, and particle transport ratio pertaining to these methods are measured. It is determined that these quantities are influenced by the particle size and concentration within the flow, the pipe rotation, the flow volume, and the inclination of the annulus. The study is performed on a concentric annulus with a variable inclination; the ratio of the inner to outer pipe radius is 0.7, homogeneous, 2-mm sand is used, and both experimental and numerical results are presented for fully developed solid-liquid two-phase flows of non-Newtonian fluid with different CMC solutions. It is determined that the transport ratio and pressure loss are both directly related to the drilling efficiency in directional drilling.

Cell damage, one of critical issues in the bioreactor design for animal cell culture, is caused mainly from the bubble bursting at the free surface subjected to strong extensional flows. In this work, extensive computational studies are performed to investigate bubble bursting process in great details. Extensive numerical simulations are performed for a wide range of bubble diameters (from 0.5 to 6 mm) and the surface tension values (from 0.03 to 0.072 N/m), with which effects of the bubble size and surfactant (PF68) concentration on the hydrodynamic stress are investigated. For all the cases, the maximum extensional stress appears at the instance when receding films impact each other at the bottom of the bubble. A model equation based on numerical simulations is presented to predict the maximum extensional stress as a function of the bubble diameter and the surface tension. The bubble diameter has turned out to contribute significantly the maximum hydrodynamic extensional stress. In addition, the bubble collapsed time and the affected volume around a bubble subjected to the critical extensional stress are investigated. The extensional stress estimation is reported as a function of the bubble size and the surface tension. The influence of the bubble size on the maximum stress dominates and extensional stress reaches up to the order of 104 Pa for bubble size of 0.5 mm.

We examine the characteristics of helical flow in a concentric annulus with radii ratios of 0.52 and 0.9, whose outer cylinder is stationary and inner cylinder is rotating. Pressure losses and skin friction coefficients are measured for fully developed flows of water and a 0.4% aqueous solution of sodium carboxymethyl cellulose (CMC), when the inner cylinder rotates at the speed of 0∼62.82 rad/s. The transitional flow has been examined by the measurement of pressure losses to reveal the relation between the Reynolds and Rossby numbers and the skin friction coefficients. The effect of rotation on the skin friction coefficient is largely changed in accordance with the axial fluid flow, from laminar to turbulent flow. In all flow regimes, the skin friction coefficient increases due to inner cylinder rotation. The change of skin friction coefficient corresponding to the variation of rotating speed is large for the laminar flow regime, becomes smaller as the Reynolds number increases for the transitional flow regime, and gradually approaches zero for the turbulent flow regime. The value of skin friction coefficient for a radii ratio of 0.52 is about two times larger than for a radii ratio of 0.9. For 0.4% CMC solution, the value of skin friction coefficient for a radii ratio of 0.52 is about four times larger than for a radii ratio of 0.9.

Nano-size CoAl 2 O 4 spinel powders were synthesized by the sol-gel process. Co(NO 3 ) 2 ·6H 2 O, Al(NO 3 ) 3 ·9H 2 O and C 6 H 8 O 7 ·H 2 O were used as precursor materials. The formation of CoAl 2 O 4 crystals occurred when the precursors were calcined at 400°C in air for 1 h. Homogeneous CoAl 2 O 4 spinel powders with a particle size of∼88.3 nm and with a specific surface area of ∼69.2 m 2 .g -1 were obtained. The gel formation, microstructure and optical properties of the CoAl 2 O 4 spinel powders were characterized by TG-DTA, FT-IR, XRD, SEM, BET and UV-Vis. techniques.

Thin film photocatalysts of TiO 2 coated glass tile were prepared to eliminate air pollutants, using the precipitation dropping method under various hydrolysis conditions. The surface structure of TiO 2 films was changed, when changing the pH, the addition rate of NH 4 HCO 3 and TiCl 4 concentration. About 10 nm anatase TiO 2 particles in sol solution were formed, when pH of the solution is 6, the addition rate of NH 4 HCO 3 1.0 ml/min and TiCl 4 concentration 0.03 mol/l. The morphology and the crystal structure of TiO 2 film affect most. The photocatalytic decomposition of acetic acid was affected by both the morphology and the crystallinity of precipitated TiO 2 particles.

Thin film photocatalysts of TiO2 coated on the glass were prepared to self-clean and eliminate air pollutants by spin coating process with Ti(OC3H7 i)4, including PEG. The surface structure of TiO2 films changed according to the molecular size of PEG. It was found that NOx was efficiently eliminated by the TiO2 film photocatalyst. The contact angle of water drop on the TiO2 films decreased to less than 10°. It revealed the hydrophilic property of TiO2 films. The morphology and the crystal structure of TiO2 films were affected most.

ZrO2-SiO2 coatings deposited on 316 L stainless steel were prepared to protect chemically the substrates by sol-gel process using Zr(OC3H7 n)4/Si(OC2H5)4 as precursors. The influence of the ZrO2-SiO2 coatings on the corrosion resistance of the 316 L stainless steel was evaluated with the potentiodynamic polarization curves in deareated 15% H2SO4 solutions at 25, 40 and 50 °C . Comparative test was performed on uncoated one. The values of the electrochemical parameters explain how. ZrO2-SiO2 films increase the resistance of stainless steel against corrosion.

Sol-gel coatings of TiO2 have been prepared from TiO2 sol and deposited by a dip-coating technique on 316L stainless steel sheets to study their electrochemical behavior in corrosive solutions. The influence of the coatings on the chemical corrosion of the substrate was evaluated by potentiodynamic polarization curves in different aqueous NaCl solution at 25°C. Comparative tests were performed on uncoated one. The thickness of the TiO2 coatings varied from 0.5~0.8 µm. The values of the electrochemical parameters allow for an explanation of the role of the TiO2 films in the increased resistance of stainless steel against corrosion in moderately aggressive environments.