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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.

This study explores the cooling performance associated with spray cooling with minimum quantity lubrication (MQL) in milling of Ti 6Al 4V using tungsten carbide (WC) cutting tool. Vegetable oil is used as a cutting fluid, and it impacts the cutting zone. A numerical model using sliding mesh and discrete phase model (DPM) is developed to calculate the flow field and the temperature distributions in both WC and Ti 6Al 4V subjected to conjugated heat transfer. The effect of spray angle relative to the feed direction on cooling performance is examined by analyzing the flow field and droplet behavior when nozzle is oriented to the tool or tool flute. The result shows that the temperature of both WC and Ti 6Al 4V for 0 and 90° of spray angle is lower than that for 45° of spray angle. However, 90° of spray angle is not suitable for lubrication purpose in milling process since MQL droplets hardly penetrate into the cutting zone.

Subsea separation is an attractive and economic solution to develop deep offshore fields producing fluid without hydrate or wax. The subsea separation system should be reliable to ensure successful operation in a wide range of multiphase flow regime, without need for developments. A subsea separator can avoid or simplifying costly surface platforms of floating vessels, as well as being an efficient tool to enhance hydrocarbon production. One solution of interest is the separation and re-injection of water at the seabed to avoid bringing the water up to the surface facility. In this study, multiphase flow characteristics inside in-line type subsea separation system are investigated for the design of subsea separation system. The separation efficiency of the subsea separator is determined through experiments that are the liquid-gas phased separation. Also internal swirl element (ISE) modelling of the separator was optimized. The analysis results were utilized to improve the reliability and efficiency of the subsea separation system.

The role of additives in the performance of CsPbI3 perovskite solar cells (PSCs) was investigated. Different kinds of cations and anions were used as additives in a N,N-dimethylformamide (DMF) solution containing CsI and PbI2 (1:1 molar ratio). These include HI, HBr, HCl, NH4I, NH4Br, and NH4Cl. Additive cations (H+ and NH4+) as well as halide ions (I–, Br–, and Cl–) are important for the properties of PSCs. Especially, the addition of iodine ion showed good characteristics compared to Br– and Cl–. Among the CsPbI3 layers prepared with different kinds of additives and annealed at different temperatures, the X-ray diffraction peaks of CsPbI3 were clearly found at 14° and 28° for the sample annealed at 150 °C with 50 μL of HI, suggesting the formation of a cubic structure at the low temperature of 150 °C. The field emission scanning electron microscopy images indicate that the surface of the perovskite layer with hydrogen halide additive (“H+”-based additive) is more uniform than that with ammonium additive...

Although many full waveform inversion methods have been developed to construct velocity models of subsurface, various approaches have been presented to obtain an inversion result with long-wavelength features even though seismic data lacking low-frequency components were used. In this study, a new full waveform inversion algorithm was proposed to recover a long-wavelength velocity model that reflects the inherent characteristics of each frequency component of seismic data using a single-frequency component decomposed from the spectrogram. We utilized the wavelet transform method to obtain the spectrogram, and the decomposed signal from the spectrogram was used as transformed data. The Gauss–Newton method with the diagonal elements of an approximate Hessian matrix was used to update the model parameters at each iteration. Based on the results of time–frequency analysis in the spectrogram, numerical tests with some decomposed frequency components were performed using a modified SEG/EAGE salt dome (A–A′) line to demonstrate the feasibility of the proposed inversion algorithm. This demonstrated that a reasonable inverted velocity model with long-wavelength structures can be obtained using a single frequency component. It was also confirmed that when strong noise occurs in part of the frequency band, it is feasible to obtain a long-wavelength velocity model from the noise data with a frequency component that is less affected by the noise. Finally, it was confirmed that the results obtained from the spectrogram inversion can be used as an initial velocity model in conventional inversion methods.

Purpose The purpose of this study is structural stability evaluation of umbilical winch. In accordance with the recent trend for developing natural resources, high-technology equipment on exploration ships is becoming more technologically advanced. One such piece of high-technology equipment is the umbilical winch. In this study, the umbilical winch is divided into two parts (drum and winch), where each is respectively designed with three dimensional models using CATIA, and dynamic simulation and structural analysis are performed using ANSYS. Design/methodology/approach In this paper, the winch is divided into two parts for finite element analysis, the drum and whole winch model, and the parts are designed as three-dimensional models except for some small parts, such as bolt holes. Dynamic simulation and structural analysis are then performed using ANSYS. The analysis results ensure the reliability of the design methods and will be used in the domestic localization of remote operated vehicle (ROV) launch and recovery systems (LARS). Findings The strain is identified from the results, but it is very small. Some stress is concentrated at the lower corner of the drum, but the maximum stress value is lower than the allowable stress; therefore, the structure has no impact on the strain and stress. Thus, it is determined that the designed structure is safe. The results ensure the reliability of the design methods and will be used in the domestic localization of ROV LARS. Originality/value Previous studies focus on the static and mechanic problems of the winch by considering winch and drum breakage in the umbilical winch system. However, ships have a nonlinear motion characteristic with six degrees of freedom according to the constant influence of the external environment. In addition, from a design perspective, the dynamic characteristics (e.g. the ship’s motions) are more important than the static characteristics. Thus, the authors focus on winch stability securement with variable loads, such as ships moving, wave disturbance and other such important environment conditions.

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.

Metal–organic frameworks (MOFs) have emerged as a class of crystalline porous material for energy-related applications. Many MOF-based materials are efficient catalysts for hydrogen evolution reactions (HERs). Herein, we illustrate a strategy to modify Co-based MOFs into amorphous molybdenum sulfide (MoSx) via a facial solvothermal method. The modification gives rise to CoMoS phases that reduce hydrogen adsorption energy of catalysts. As a result, MoSx substantially improves the catalytic activity of Co-based MOF for HERs. An optimal sample with 40% MoSx delivered the best HER performance with a low onset potential of −147 mV and a Tafel slope of ∼68 mV decade−1. Furthermore, the composite catalyst was stable for up to 1000 cycles without any changes in performance. These results suggest that the MoSx/Co–MOF–74 composite is a viable candidate for replacing noble metals as a high-performance catalyst for HER in the future.

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.

This paper presents a facile method to fabricate the hole injection layer (HIL) for organic photovoltaic cells (OPVs) and organic light-emitting diodes (OLEDs) using a thermally annealed (NH 4 ) 2 WS 4 precursor under air ambient. The thermal gravimetric analysis curve shows that WS 3 , WS 2 , and WO x are formed by the thermal decomposition of (NH 4 ) 2 WS 4 above 160 °C. The disappearance of the S 2p peak in the photoemission spectra and of the W–S peak in the Raman spectra as well as the decrease in the water contact angle after annealing at 250 °C suggest that (NH 4 ) 2 WS 4 decomposed into WO x . The power conversion efficiency (PCE) of the OPV improved from 1.51% to 3.14% after the insertion of 250 °C-annealed (NH 4 ) 2 WS 4 as the HIL, which is comparable to the PCE of the OPV based on poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) HIL (3.23%). Furthermore, the luminance efficiency of the OLED with 250 °C-annealed (NH 4 ) 2 WS 4 (15.76 cd/A) was higher than that of the device based on PEDOT:PSS (12.34 cd/A). The results of the in situ deposition experiments revealed that the improved device performance originates from the energy level alignment and electron–hole balance. These data demonstrate that 250 °C-annealed (NH 4 ) 2 WS 4 is a promising candidate for fabrication of the HIL in optoelectronic devices using a facile solution process under air ambient.

Subsea separation is an attractive and economic solution to develop deep offshore oil and gas fields producing fluid without hydrate or wax. The subsea separation system should be reliable to ensure successful operation in a wide range of multiphase flow regime. A subsea separator can avoid or simplifying costly surface platforms of floating vessels, as well as being an efficient tool to enhance hydrocarbon production. One solution of interest is the separation and re-injection of water at the seabed to avoid bringing the water up to the surface facility. In this study, liquid-liquid flow characteristics inside in-line type subsea separation system are investigated for the design of subsea separation system. The separation efficiency of the subsea separator is determined through experiments that are the liquid-liquid phased separation. Also internal swirl element (ISE) modeling of the separator was optimized. The analysis results were utilized to improve the reliability and efficiency of the subsea separation system.

Contamination in a cleanroom may appear even more complicated by the effect of complicated manufacturing processes and indoor equipment. For this reason, detailed information about the concentration of pollutant particles in the cleanroom is needed to control the level of contamination financially and efficiently without any problem in manufacturing process. Allocation method has been developed as one of main ideas to fulfill a function of controlling contamination under the situation. By using this method, weighting factor can be predicted based on cleanliness on sampling spots and the values based on numerical analysis. In this point, the weighting factor indicates how each of contaminant sources influences the concentration of pollutant in the cleanroom. In this paper, when applied allocation method, we propose zoning method to accelerate the calculation time. And it was applied to cleanliness the actual improvement of the turbulent type clean room. As a result, we could estimate quantitatively the amount of contamination generated from the pollution sources. And was proved by experiments that it is possible to improve the level of cleanliness of the cleanrooms by using these results.

During drilling, the precipitation velocity of cuttings within an annulus depends on the density, configuration, and size of the cuttings, and on the density, viscosity, and rheological characteristics of the drilling fluid. In this study, in order to identify transfer features of cuttings, an experiment was performed under wide-ranging conditions by constructing a slim hole annulus (44 mm × 30 mm) device. In this experiment, the pressure loss and the particle transport ratio were measured in upward flow of Newtonian and non-Newtonian fluids. These quantities were influenced by particle concentration within the flow, pipe rotation, flow rate, and inclination of the annulus. For both water and CMC (carboxymethylcellulose) solutions, the higher the concentration of the solid particles is, the larger the pressure gradients become. The experimental uncertainty of this study varies from a minimum of 3% to a maximum of 9% depending on the experimental conditions.

During drilling, the precipitation velocity of cuttings within an annulus depends on the density, configuration, and size of the cuttings, and on the density, viscosity, and rheological characteristics of the drilling fluid. In directional drilling in particular, it is difficult to adjust and control the cuttings. In contrast to vertical drilling, it is very important to evaluate the flow characteristics of a drilling flow field. However, research on the transfer features of cuttings is inadequate. In this study, in order to identify transfer features of cuttings, an experiment was performed under wide-ranging conditions by constructing a slim hole annulus (44 mm×30 mm) device. In this experiment, the friction coefficient, pressure loss, particle transport ratio, and particle volume fraction were measured. These quantities were influenced by particle concentration within the flow, pipe rotation, flow volume, and inclination of the annulus. In addition, a mathematical formula for volumetric concentration was deduced and compared to the test results and behavior of cuttings under the other drilling condition was made to be predicted. Therefore, this study can provide meaningful data for vertical and horizontal drilling, and for directional drilling.

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.

During drilling, the precipitation velocity of cuttings within an annulus depends on the density and configuration of the cuttings, and on the density, viscosity, and rheological characteristics of the drilling fluid. In directional drilling in particular, it is difficult to adjust and control the cuttings. In contrast to vertical drilling, it is very important to evaluate the flow characteristics of a drilling flow field. However, research on the transfer features of cuttings is inadequate. In this study, in order to identify transfer features of cuttings, an experiment was performed under wide-ranging conditions by constructing a slim hole annulus (44 mm×30 mm) device. In this experiment, the particle volume fraction were influenced by particle size, particle concentration within the flow, pipe rotation, flow volume, and inclination of the annulus. In addition, a mathematical formula for volumetric concentration was deduced and compared to the test results and behavior of cuttings under the other drilling condition was made to be predicted. Therefore, this study can provide meaningful data for vertical and horizont al drilling, and for directional drilling.

We examine solid–liquid mixture upward hydraulic transport of solid particles in vertical and inclined annuli with a rotating inner cylinder. Lift forces acting on fluidized particles play a central role in many important applications such as the removal of drill cuttings in horizontal drill holes, sand transport in fractured reservoirs, and sediment transport. Annular fluid velocities in our study varied from 0.4 m/s to 1.2 m/s. The effect of annulus inclination and drill pipe rotation on the carrying capacity of drilling fluid, particle rising velocity, and pressure drop in a slim hole annulus were measured for fully developed flows of water, and for aqueous solutions of sodium carboxymethyl cellulose (CMC) and bentonite. For higher particle feed concentrations, the hydraulic pressure drop of the mixture flow increased due to friction between the wall and solids, or among solids. Comparing our numerical and experimental results allowed the assessment and further development of existing two-phase numerical models and grid constructions.

An experimental study was conducted to study solid-liquid mixture upward hydraulic transport of solid particles in vertical and inclined annuli with rotating inner cylinder. Lift forces acting on a fluidized particle play a central role in many important applications, such as the removal of drill cuttings in horizontal drill holes, sand transport in fractured reservoirs and sediment transport, etc. Annular fluid velocities varied from 0.4 m/s to 1.2 m/s. Effect of annulus inclination and drill pipe rotation on the carrying capacity of drilling fluid, particle rising velocity, and pressure drop in the slim hole annulus have been measured for fully developed flows of water and of aqueous solutions of sodium carboxymethyl cellulose (CMC) and bentonite, respectively. For higher particle feed concentration, the hydraulic pressure drop of mixture flow increases due to the friction between the wall and solids or among solids.

An investigation is conducted to understand hydraulic transport characteristics of a solid-liquid mixture flowing vertically upward. Namely, this is the instance that solid particles are carried by non-Newtonian fluids in a slim hole concentric annulus with rotating inner cylinder. In this study a clear acrylic pipe was used in order to observe the movement of solid particles. The bulk axial velocities varied from 0.4 m/s to 1.2 m/s. The mud systems which were utilized included aqueous solution of sodium carboxymethyl cellulose (0.2∼0.4%CMC) and 5% bentonite solutions. Solid volumetric concentration and pressure drops were measured for the various parameters such as inclined annulus, flow rate, and rotational speed of inner cylinder. For both CMC and bentonite solutions, the higher the concentration of the solid particles are, the larger the pressure drops become.

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.

The implementation of subsea separation and liquid boosting is becoming a common development scheme for the exploration of deep water fields. Subsea separation system should be reliable to ensure successful operation in a wide range of 3-phase flow regime, without need for developments. A subsea separator can avoid or simplying costly surface platforms of floating vessels, as well as being an efficient tool to enhance hydrocarbon production. One solution of interest is the separation and re-injection of water at the seabed to avoid bringing the water up to the surface facility. In this study, multiphase flow characteristics inside subsea separation system are investigated for the design of subsea separation system.Copyright © 2014 by ASME

The shape of the polymers in the mixed alkoxide solutions of Si(OC2H5)4 and Zr(n-OC3H7)4 with various water contents (1, 2, 4, and 8 in molar ratio to alkoxide, r) and catalysts was examined by rheological measurements, and its relation with fiber drawing behavior of the solutions was described. It was found that fibers could be drawn in the viscosity range 1–100 P from the acid-catalyzed solutions with lower water contents of the molar ratio H2O/alkoxide, r≤2. On the other hand, no fiber could be drawn from the acid-catalyzed solutions including a large amount of water (r≥4) and the base-catalyzed solutions.

Considerable interest has been shown in the problems of viscous flow between concentric annulus with one or both of the cylinders rotating. And the problem of instability of isothermal viscous flow between rotating concentric annulus is also important problem in a rotating electrical machine, especially in the drilling of oil well. This study concerns the phenomena and variables which control the rate of heat transfer in the gap of a rotating annulus. The objective of this study is to study the non-isothermal case, showing the effect of a radial temperature gradient in the annulus on the instability of this type flow. In this study the effect of axial flow rate, rotational speed of inner cylinder and temperature gradient between the cylinders on the heat transfer were investigated