Effects Of Relevant Parameters Research Articles

Radiative nonlinear 3D flow of ferrofluid with Joule heating, convective condition and Coriolis force

Characteristics of heat transport mechanism in three-dimensional ferrofluid flow past a deformed surface subjected to the Coriolis and Lorentz forces are analyzed. The impacts of Joule heating, nonlinear thermal radiation, viscous dissipation and convective condition are also accounted. The carrier fluid (water) is embedded by Fe3O4 nanoparticles. The boundary layer approximations are employed in problem statement. Stretching transformations are utilized to form nonlinear ODE system from governed PDE system. The subsequent system is treated numerically via Runge-Kutta-Fehlberg method. Effects of relevant parameters on different flow fields are discussed comprehensively with help of graphs. It is established that the heat transfer rate is enhanced due to Coriolis and Lorentz forces. Furthermore, Fe3O4 nanoparticles enhance the Nusselt number significantly in comparison with Al2O3 nanoparticles.

Effects of single and multi-walled carbon nano tubes on water and engine oil based rotating fluids with internal heating

Three dimensional (3D) flow of a rotating Water and Engine Oil Based fluid is analyzed. Effects of nanometer (nm) sized Single (SWCNT) and multiwalled carbon nanotubes (MWCNT) are examined on flow and heat transfer characteristics. Thermofluid performance within Water and Engine Oil base fluid are investigated using thermal conductivity and viscosity of both single and multiple wall carbon nanotubes (CNTs) of similar volume. The governing partial differential equations are converted into nonlinear, coupled, ordinary differential equations which are solved numerically using a combination of Quasi-linearization and Chebyshev pseudo-spectral methods. Effects of relevant parameters on physical quantities are examined. The obtained results revealed an enhancement in temperature as well as corresponding thermal boundary layer thickness with volume fraction of both types of carbon nanotubes. Due to higher density and thermal conductivity, SWCNTs offer higher skin friction and Nusselt number. Engine oil base fluid depicted higher heat transfer rate and local skin friction than water based fluid for both type of carbon nanotubes. Residual error are plotted to check the accuracy of obtained results. Comparison with previously published literature is made and an excellent agreement is observed which validate our applied numerical scheme.

Production decline type curves analysis of a finite conductivity fractured well in coalbed methane reservoirs

Abstract Production decline type curves analysis is one of the robust methods used to analyze transport flow behaviors and to evaluate reservoir properties, original gas in place, etc. Although advanced production decline analysis methods for several well types in conventional reservoirs are widely used, there are few models of production decline type curves for a fractured well in coalbed methane (CBM) reservoirs. In this work, a novel pseudo state diffusion and convection model is firstly developed to describe CBM transport in matrix systems. Subsequently, based on the Langmuir adsorption isotherm, pseudo state diffusion and convection in matrix systems and Darcy flow in cleat systems, the production model of a CBM well with a finite conductivity fracture is derived and solved by Laplace transform. Advanced production decline type curves of a fractured well in CBM reservoirs are plotted through the Stehfest numerical inversion algorithm and computer programming. Six flow regimes, including linear flow regime, early radial flow in cleat systems, interporosity flow regime, late pseudo radial flow regime, transient regime and boundary dominated flow regime, are recognized. Finally, the effect of relevant parameters, including the storage coefficient of gas in cleat systems, the transfer coefficient from a matrix system to the cleat system, the modified coefficient of permeability, dimensionless fracture conductivity and dimensionless reservoir drainage radius, are analyzed on type curves. This paper does not only enrich the production decline type curves model of CBM reservoirs, but also expands our understanding of fractured well transport behaviors in CBM reservoirs and guides to analyze the well's production performance.

Entropy generation analysis of radiative heat transfer effects on channel flow of two immiscible couple stress fluids

An analysis is presented to investigate the effects of radiative heat transfer on entropy generation in flow of two immiscible non-Newtonian fluids between two horizontal parallel plates. Both the plates are maintained at constant temperatures higher than that of the fluid. The Stokes’ couple stress flow model is employed. The flow region consists of two zones with the flow of the heavier fluid taking place in the lower zone. The classical “no-slip” condition is prescribed at the plates and continuity of velocity, vorticity, shear stress, couple stress, temperature and heat flux are imposed at the interface. The original partial differential Navier–Stokes equations are converted to ordinary differential equations by assuming velocity and temperature are functions of vertical distance and solved mathematically by usual classical methods. The derived velocity and temperature profiles are used to compute the expressions for the entropy generation number and Bejan number. The effects of relevant parameters on velocity, temperature, entropy generation number and Bejan number are investigated. The computations show that the entropy production decreases with thermal radiation, whereas it increases with viscous dissipation. The effect of viscous dissipation is justified since it significantly affects heat transfer and entropy generation characteristics and therefore should not be ignored.

A joint optimal policy of block preventive replacement and spare part inventory

Maintenance and spare part should be considered jointly as they are related activities and maintenance generates the demand of spare parts. In this study, a joint optimization policy of block replacement and spare parts inventory for multi-components system is proposed by simulation optimization approach using Monte Carlo simulation. Through analyzing the process of maintenance replacement and spare inventory within replacement interval T, the total expected cost can be derived. The expected cost per unit time is the objective function to optimize the block replacement interval T and maximum inventory level S. Monte Carlo method is used to simulate the operate process and simulation algorithm is presented to derive the approximate optimal solution. Finally, a numerical example is presented to illustrate the effectiveness of the proposed model. Sensitivity analysis and the effect of relevant parameters on the optimal decisions are discussed.

CFD Simulations to Study Parameters Affecting Gas Explosion Venting in Compressor Compartments

In this work, a series of vented explosions in a typical compressor compartment are simulated using FLACS code to analyze the explosion venting characteristics. The effects of relevant parameters on the pressure peaks (i.e., overpressure and negative pressure) are also numerically investigated, including vent area ratio of the compressor compartment, vent activation pressure, mass per unit area of vent panels, and volume blockage ratio of obstacles. In addition, the orthogonal experiment design and improved grey relational analysis are implemented to evaluate the impact degree of these relevant parameters. The results show that the pressure peaks decrease with the increase of vent area ratio. There is an approximately linearly increasing relationship between the pressure peaks and the vent activation pressure. The pressure peaks increase with the mass per unit area of vent panels. The pressure peaks increase with the volume blockage ratio of obstacles. Based on the grey relational grade values, the effects of these relevant parameters on the overpressure peak are ranked as follows: volume blockage ratio of obstacles > vent activation pressure > vent area ratio > mass per unit area of vent panels. These achievements provide effective guidance for the venting safety design of gas compressor compartments.

Analysis of magnetohydrodynamic flow and heat transfer of Cu–water nanofluid between parallel plates for different shapes of nanoparticles

The present study analyzes the heat transfer in the flow of copper---water nanofluids between parallel plates. For effective thermal conductivity of nanofluids, Hamilton and Crosser's model has been utilized to examine the flow by considering different shape factors. By employing the suitable similarity transformations, the equations governing the flow are transformed into a set of nonlinear ordinary differential equations. The resulting set of equations is solved numerically with the help of Runge---Kutta---Fehlberg numerical scheme. The graphical simulation presents the analysis of variations, in velocity and temperature profiles, for emerging parameters. A comprehensive discussion also accompanies the graphical results. Moreover, the effects of relevant parameters, on skin friction coefficient and Nusselt number, are highlighted graphically. It is noticed that the velocity field is an increasing function of all the parameters involved. Furthermore, the temperature of the fluid is maximum for the platelet-shaped particles followed by the cylinder- and brick-shaped particles.

Pressure transient analysis of multistage fracturing horizontal wells with finite fracture conductivity in shale gas reservoirs

A new analytical solution of pressure transient analysis is proposed for multistage fracturing horizontal well (MFHW) with finite-conductivity transverse hydraulic fractures in shale gas reservoirs. The effects of absorption, diffusion, viscous flowing, stress sensitivity, flow convergence, skin damage and wellbore storage are simultaneously considered as well in this paper. Laplace transformation, source sink function, perturbation method and superposition principle are, respectively, employed to solve related mathematical models of reservoir system and hydraulic fracture system. And then boundary element method (BEM) is applied to couple reservoir system and hydraulic fracture system. The transient pressure is inverted from Laplace space into real time space with Stehfest numerical inversion algorithm. Based on this new solution, the distribution of transient pseudo-pressure for MFHW with multiple finite-conductivity transverse hydraulic fractures is obtained. Different flowing regimes are identified, and the effects of relevant parameters are analyzed as well. The essence of this paper is considering the effects of transient gas flowing occurrence in finite-conductivity hydraulic fractures with BEM. Compared with some existing models and numerical simulation model of shale gas reservoirs, this proposed new model can provide a relative more accurate analysis of the relevant parameters, especially for the fracture conductivity. In conclusion, this new model provides the relative accurate and comprehensive evaluation results for multistage fracturing horizontal technology.

Effects of relevant parameters on the bandgaps of acoustic metamaterials with multi-resonators

Locally resonant acoustic metamaterials with multi-resonators are generally regarded as a fine trend for managing the bandgaps, the different effects of relevant structural parameters on the bandgaps, which will be numerically investigated in this paper. A two-step homogenization method is extended to achieve the effective mass of multi-resonators metamaterial in the lattice system. As comparison, the dispersive wave propagation in lattice system and continuum model is studied. Then, the different effects of relevant parameters on the center frequencies and bandwidth of bandgaps are perfectly revealed, and the steady-state responses in the continuum models with purposed relevant parameters are additionally clarified. The related results can well confirm that the bandgaps exist around the undamped natural frequencies of internal resonators, and also their bandwidth can be efficiently controlled with the ensured center frequencies. Moreover, the design of purposed multi-resonators acoustic metamaterial in vibration control is presented and discussed by an example.

Catalytic oxidative desulfurization of BT and DBT from n -octane using cyclohexanone peroxide and catalyst of molybdenum supported on 4A molecular sieve

Abstract In this paper, the performance of catalytic oxidative desulfurization (ODS) was studied using catalyst MoO 3 /4A which was prepared by depositing molybdenum on 4A molecular sieve, a microporous material. Dibenzothiophene (DBT) and benzothiophene (BT) were selected as the target compounds, and oil-soluble cyclohexanone peroxide (CYHPO) as an oxidant. The effects of relevant parameters on ODS including molybdenum loading, reaction temperature, reaction time, the molar ratio of CYHPO/DBT and the weight of catalyst MoO 3 /4A were investigated, and the oxidation mechanisms as well as the kinetics were also examined individually. The catalytic oxidative removal of DBT and the residual sulfur content reached 99.0% and 5 ppmw, respectively, at an optimal catalytic condition of Mo loading of 6 wt.%, molar ratio of CYHPO/DBT of 2.5 and volume mass ratio of model gasoline to catalyst MoO 3 /4A of 100 at 373 K over 30 min. The optimal design of experiments using Box–Behnken method was employed to evaluate the effects of individual process variables such as, reaction temperature, reaction time and molar ratio of CYHPO/DBT and their optimum values were found to be 340 K, 38 min and 3.8, respectively, to achieve a conversion of 100%. The catalyst could be reused for 4 times before the total DBT content of treated model gasoline was higher than 10 ppmw, and the activity of the desulfurization system was above 95% after regenerating for 9 times. The catalytic oxidation of DBT and BT fitted the pseudo-first order kinetic model pretty well. The catalyst MoO 3 /4A was characterized by the scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray photoelectron spectrum (XPS), and the data showed that a thin layer of active components was covered on the catalyst surface which helped to explain the satisfactory catalytic performance.

Evaluation of casing integrity defects considering wear and corrosion – Application to casing design

Casing integrity is an important category of well integrity in drilling and well operations. Casing integrity defect due to wear and corrosion can cause casing strength degradation, casing deformation and even well abandonment. In this paper, a theoretical model for casing strength degradation due to wear is established in bipolar coordinate system. Another model is established to calculate stress concentration factor of casing with corrosion pit at inner wall. The effects of relevant parameters on residual strength of defective casing are analyzed according to parametric study. According to the stress distribution of casing after wear and corrosion under tri-axial stress, strength check is carried out based on Von Mises yield criterion and Lame thick-walled solution for the pipe. Then, in order to evaluate casing integrity of a real well, casing wear and corrosion experiments are conducted to study mechanisms and obtain relevant parameters for calculation. Finally, according to the established models and experimental results, a modified casing design of this well is proposed considering the effects of wear and corrosion on casing strength degradation. The work presented in this paper can provide a theoretical foundation and technological basis for casing integrity evaluation and casing design of highly-deviated wells or extended-reach wells in sour environment.

Entropy Generation Analysis of the MHD Flow of Couple Stress Fluid between Two Concentric Rotating Cylinders with Porous Lining

An attempt has been made to study the entropy generation analysis of couple stress fluid flow in an annulus between two concentric rotating vertical cylinders. There is a porous lining attached to the inside of an outer cylinder. The flow is under the influence of a radial magnetic field. The flow in the annular gap is caused by rotation of the cylinders. The Stokes couple stress flow model is employed. The flow in the porous sleeve is governed by Darcy's law. The velocity, temperature, entropy generation number, Bejan number, wall shear stress and heat transfer rate at the inner and outer cylinders are obtained numerically by employing a finite difference scheme with vanishing of couple stresses on the boundary. The effect of relevant parameters on the flow and entropy generation rate are discussed and depicted through graphs.

Pressure and rate transient analysis of composite shale gas reservoirs considering multiple mechanisms

Based on multiple mechanisms, including adsorption/desorption, viscous flow, diffusive flow in shale matrix and stress sensitivity of natural fractures, a new semi-analytical composite model is presented for multi-stage fractured horizontal well (MFHW) in shale gas reservoirs. The simplified composite model of an actual gas reservoir is composed of an inner and an outer region. Inner region represents stimulated reservoir volume (SRV) and contains natural fractures and matrix. Matrix-natural fracture transfer flow is assumed to be pseudo-steady state (PSS) or transient state (TS) which are described by the Warren & Root and the De Swan models respectively. Outer region is un-stimulated reservoir volume (USRV), which is described by single porosity medium model. First, transient flow model for continuous line source in composite shale gas reservoir is established. Perturbation method is applied to linearize the model. Then the line source solution is solved by Laplace transformation. Pressure responses of multi-stage fractured horizontal well is obtained using principle of superposition. The model is verified with the available field data from the Barnett Shale. In addition, transient pressure and production rate of MFHW in shale gas reservoirs with consideration of multiple mechanisms and SRV are analyzed and five typical regimes are identified: radial flow in SRV, interporosity flow, region pseudo-steady flow, diffusive flow and late pseudo-radial flow. In PSS transfer model, type curve has two cavities: the early one is caused by pseudo-steady interporosity flow between natural fractures and matrix and the late one is caused by diffusive flow in the matrix. But in TS transfer model, there is no obvious cavity in interporosity flow period due to subtle pressure fluctuation. The effects of relevant parameters on transient pressure and production rate are analyzed, including SRV radius, stress sensitivity coefficient, adsorption index, storability ratio, interporosity coefficient and diffusivity coefficient. The results demonstrate that larger SRV can reduce formation energy depletion and improve production rate. Stress sensitivity causes more pressure depletion, while desorption and diffusion can compensate for the pressure loss in the formation. The production rate increases as adsorption index σ rises. Storability ratio of natural fractures ωf and interporosity coefficient λ1 mainly affect interporosity flow period while storability ratio of matrix ωm and diffusivity coefficient λ2 mainly have effects on diffusive flow period. The larger the value of these four parameters, the larger the production rate in corresponding periods.

Productivity Model for Shale Gas Reservoir with Comprehensive Consideration of Multi-mechanisms

Multi-stage fracturing horizontal well currently has been proved to be the most effective method to produce shale gas. This method can activate the natural fractures system defined as stimulated reservoir volume (SRV), the remaining region similarly is defined as un-stimulated reservoir volume (USRV). At present, no type curves have been developed for hydraulic fractured shale gas reservoirs in which the SRV zone has triple-porosity dual-depletion flow behavior and the USRV zone has double porosity flow behavior. In this paper, the SRV zone and USRV zone respectively are simplified as cubic triple-porosity and slab dual porosity media. We have established a new productivity model for multifractured horizontal well shale gas with Comprehensive consideration of desorption, diffusion, viscous flow, stress sensitivity and dual-depletion mechanism in matrix. The rate transient responses are inverted into real time space with stehfest numerical inversion algorithm. Type curves are plotted, and different flow regimes in shale gas reservoirs are identified. Effects of relevant parameters are analyzed as well. The whole flow period can be divided into 8 regimes: bilinear flow in SRV; pseudo elliptic flow; dual inter-porosity flow; transitional flow; linear flow in USRV; inter-porosity flow and boundary-dominated flow. The stress sensitivity basically has negative influence on the whole productivity period .The less the value of Langmuir volume and the lager the value of Langmuir pressure, the more lately the inter-porosity flow and boundary-dominated flow occurs. It in concluded that the USRV zone has positive influence on production and could not be ignored.

A new expression for determining the bending stiffness of circular micropile groups

Increased bending stiffness and decreased foundation rotation are two main factors which reduce the rocking motion of foundation. A micropile group in circular arrangement is an innovative technique for reducing the rocking motion of the foundation. In this paper, the effects of several parameters were numerically investigated on the rocking stiffness of circular micropile group foundations. The finite difference software FLAC3D was used to model the foundation, soil, and the structure. The micropiles used in this study varied in the diameter, but had similar length. A total of seven records were selected to cover a wide range of frequency content, duration and amplitude. The results from the numerical simulation were compared and verified against those obtained from an alternative numerical method as well as a set of experimental test results. The model was then used for parametric studies and the effects of relevant parameters were investigated. The results showed that slenderness, inclination angle and distance ratio of a micropile group are main factors which increase the soil stiffness and control the seismic motion of high-rise buildings. Based on the results, a new expression was proposed that can be used to determine the optimal moment of inertia of circular micropile groups. The proposed expression revealed that the primary factors which reduce the effective period of the buildings are the number, diameter, and injection pressure of micropiles in a circular micropile group. Using the proposed relationship, it was found that using circular micropile groups can reduce the destructive seismic effects (i.e. drift demand) in high-rise buildings by up to 60%.

Theoretical analysis of a row of piles as passive barriers and an equivalent in-filled trench model

A theoretical study on the ground vibration isolation efficiency by a row of piles as passive barrier in a three-dimensional context was presented. The analysis was accomplished with the aid of integral equations governing Rayleigh wave scattering, used to predict the complicated Rayleigh wave field generated by a number of irregular scatters embedded in an elastic half-space. Then, the passive isolation effectiveness of a row of piles for screening Rayleigh wave was studied in detail. The effects of relevant parameters on the screening effectiveness were investigated and analyzed from the perspective of equivalence with in-filled trench. The results show that using a row of rigid piles as wave barrier is more effective than that of flexible ones, and an optimum reduction of vibration can be achieved either by increasing the size of piles or by decreasing the net spacing between the piles. Finally, based on the derived integral equation for Rayleigh wave scattering, the principle of equivalent modeling of the barrier of piles by an in-filled trench is put forward, which simplifies the analysis of vibration isolation by a row of piles.

Determination of Aldehydes in Environmental Water by Solid-Phase Microextraction and Gas Chromatography - Ion Trap Mass Spectrometry

Microwave-assisted extraction coupled to headspace solid-phase microextraction with on-fiber derivatization with gas chromatography ion trap mass spectrometry analysis is reported for the determination of aldehydes in environmental water. Hexanal, (E)-2-hexenal, heptanal, octanal, nonanal, E-2-decanal, and E, E-2,4-decadienal were employed to develop and validate this method. The effects of relevant parameters on the quantitative extraction of these analytes in this one-step procedure were systematically investigated. The aldehydes were extracted from environmental water by a poly(dimethylsiloxane)/divinylbenzene fiber using o-(2, 3, 4, 5, 6-pentafluoro)-benzylhydroxylamine as the derivatization reagent. Under microwave-assisted heating, the aldehydes were transferred from water by headspace solid phase microextraction. Thus, efficient extraction and derivatization were simultaneously achieved. The recovery values ranged from 72.2–96.9%, and the relative standard deviation was between 4.1–14% for the aldehydes. The detection limits were from 0.001–0.005 µg L−1. The method was validated illustrating its potential for the analysis of environmental water while offering simplicity and rapid analysis.

Modeling transient flow behavior of a multiscale triple porosity model for shale gas reservoirs

Gas flow in shales is a complex process from nanoscale to macroscale which includes diffusion of dissolved gas molecules in kerogen bulk, desorption from the pore walls, Knudsen diffusion and slip flow in nanopores, and conventional flow in natural fracture network according to recent studies. However, little work has been done in literature to simultaneously incorporate all these complex storage and flow mechanisms in well testing models for shale gas reservoirs. This paper presents a new tri-porosity model for shale gas reservoirs to describe that gas flows from formation to wellbore with consideration of all the mechanisms mentioned above. Compared with current well testing models for shale gas reservoirs, this model will be more close to the actual reservoir situation by simulating the physics behind the actual process. Partial differential equations of this tri-porosity model are derived and Laplace transform is employed to solve these equations analytically. The analytical solution of the transient pressure is obtained in real space with Stehfest numerical inversion method, and standard bi-logarithmic type curves are plotted. The characteristics of transient pressure behavior are analyzed thoroughly and different flow regimes are observed in type curves for shale gas reservoirs. Effects of relevant parameters are analyzed as well, which has important significance to understand the transient flow behavior for shale gas reservoirs.

Heat transfer partitioning model of film boiling of particle cluster in a liquid pool: implementation in a CFD code

In the present work an effective heat transfer partitioning model of three phase (particles, liquid and vapour) flow and thermal interaction have been developed by a multi-fluid approach under film boiling condition. The in-house multiphase flow code is based on finite volume method of discretization and SIMPLE-based pressure correction algorithm. From consideration of mass, momentum and energy balance across the liquid–vapour interface, the vapour bubble generated from the vapour film have been modeled and incorporated in the code. Different interaction terms between each phase are incorporated depending upon the flow regime. The code is validated with in-house and available experimental results. Finally the effect of relevant parameters on void generation under film boiling condition of particles is estimated.

The Air Solar Collectors: Introduction of Chicanes to Favour the Heat Transfer and Temperature in the Air Stream Dynamics

The thermal performance of a single pass solar air heater with chicanes attached was investigated numerically using a 2D model of solar air stream dynamics collectors where the turbulence standard ����− ���� model has been implemented. The chicane is formed with two parts: the first is perpendicular to the air flow and the second part is titled (α), they are mounted in successive rows, oriented perpendicular to the air flow and soldered to the back plate. The predicted results are validated by comparing with the literatures semi-empirical and experimental data and shown a reasonable agreement. Effects of relevant parameters as the (Reynolds number, chicanes upper parts tilts angles and air mass flow rates) on the heat transfer coefficient and temperature development are discussed. It is apparent that the turbulence created by the chicanes resulting in greater increase in heat transfer inside the air stream dynamics.