According to the existing theory, turbulent flow fields are divided into four layers, including (a) the viscous sublayer, (b) the buffer layer, (c) the logarithmic layer, and (d) the core layer. ...However, in this work, a two-layer description for some benchmark turbulent flows is proposed. To arrive at this description, firstly, the logarithmic layer is extended to include the buffer layer, which removes the need to consider the buffer layer with its complex formula. Thereafter, the attention is focused on some benchmark problems in fluid mechanics (i.e., the Couette flow, the 2D channel flow, the circular pipe flow, and the flow over a flat plate) and new descriptions are proposed for their core layers, incorporating the extended logarithmic layer. Hence, the accomplished two-layer description divides the considered turbulent flows into only (a) the viscous sublayer and (b) the extended core layer, each with a corresponding velocity profile. This description substantially simplifies the analysis and can be helpful for future studies. The proposed description is applicable to smooth as well as rough walls and is accurate for low, intermediate, and high Reynolds numbers. It is found that in spite of the simplicity of the proposed two-layer description, its outcomes in terms of the time-averaged velocity profile are in excellent agreement with those of previous studies, for all of the considered benchmark problems.
Binary nanofluids are prepared using a binary liquid (e.g., salt water) instead of a pure liquid as their host fluid. Double-diffusive convection in this type of nanofluids is a kind of ...triple-diffusive process, which simultaneously includes diffusions of heat, nanoparticles, and solute. This paper is devoted to double-diffusive mixed convection of binary nanofluids flowing through a vertical porous annulus in the presence of an externally applied radial magnetic field. To simulate the problem, a new mathematical model following the Buongiorno’s two-phase model is proposed. The equations are solved numerically by means of the finite-volume method. Thereafter, effects of the involved dimensionless variables on the distributions of stream function, temperature, solute concentration, and nanoparticles fraction as well as the mean values of the Nusselt number and the solute Sherwood number are presented and discussed. Inspection of the results demonstrates the significant contributions of the Peclet number (Pe), the usual Lewis number (Le), and the Soret-solute Lewis number (Ld) on the simulation results. In spite of that, the effects of the Hartmann number (Ha) and the thermophoresis parameter (Nt) on the simulation results are weak, while the consequences of the nanofluid Lewis number (Ln), the double-diffusive ratio (Nc), the buoyancy ratio (Nr), and the Dufour parameter (Nd) on the Nusselt and Sherwood numbers are insignificant.
This article integrates core and well log data to determine reservoir electrofacies of the Oligo-Miocene Asmari Formation in the western Dezfol Embayment, SW Iran. At the start, an unsupervised ...neural network was employed based on the selforganizing map (SOM) technique to identify and extract electrofacies groups of Asmari Formation in the Marun oilfield, which is a mixed siliciclastic and carbonate reservoir. Using inexpensive and accessible petrophysical wireline logs, such as gamma ray, sonic, density and neutron, along with calculated reservoir data (water saturation and effective porosity) from 12 reference wells and their correlation with reservoir core data, led to recognition of seven electrofacies including first four class as limestone rocks (EF1–EF4) and others three classes as sandstone rocks (EF5–EF7). Based on the porosity and permeability maps and water saturation at different depth levels, EF4 and EF7 with low porosity and permeability, high water saturation are considered as non-reservoir relating mostly to sedimentary textures of mudstone and argillaceous sandstones, respectively. By contrast, EF1 and EF5 with high values of porosity, permeability and low percent of water saturations characterize the best reservoir quality rocks, and EF2, EF3 and EF6 have medium reservoir quality. EF1 consists of dolomitic skeletal grainstone, in which biomoldic, vuggy and intercrystalline porosity is the dominant pore type, while the intergranular porosity is the major pore type in EF4 as an unconsolidated sand electrofacies. In general, the results obtained in this study indicate a satisfactory agreement between core data and log facies. This correlation allows rockfacies to be classified in the cored wells and predict those facies in the uncored wells. Using the methodology outlined here, it is possible to track reservoir electrofacies from conventional well log data.
Permeability calculation is one of the most complex subjects in characterizing a hydrocarbon reservoir. Because among the well logs, only nuclear magnetic resonance (NMR) log is possible to do in an ...accurate continuous measurement way. In the present research paper, the permeability values obtained from the NMR log in the Asmari reservoir by Schlumberger or
T
2
(SDR) and free fluid (Coates) methods were used to perform estimation by intelligent methods. Then, using an artificial neural network (ANN) and combining it with the imperial competitive optimal algorithm (ANN-ICA), the permeability values were predicted. Finally, predicted permeability values are compared with real values, and the prediction accuracy was regarded in view of mean squared error (MSE) and correlation coefficient (
R
2
). The results of this study indicated that the efficiency of ANN in permeability prediction was high when this method was optimized with the imperialist competitive algorithm. This method can be used as a powerful tool in the prediction of other reservoir parameters.
Cooling of electronic components is one of the most important concerns of manufacturers. Using heatsinks with different models is one of the recommended methods for cooling. To compare 12 types of ...heatsinks, including 3 types of fin-pin heatsinks with rectangular pins, 3 types of fin-pin heatsinks with circular pins, 3 types of fin-pin heatsinks with conical pins, and 3 types of simple fin heatsinks in 5, 7, and 9 fin types regarding forced displacement heat transfer, an experiment was conducted. A special setup designed and built for these types of heatsinks was used to conduct the test. The setup had dimensions of 100 cm × 12 cm x 3 cm with an opening of 120 cm × 120 cm for placing a fan to create airflow with variable speeds and a place for placing the heatsink at the end of the wind tunnel under variable temperatures. The test results showed that the maximum error in the two experimental tests was 6 %. Also, the results showed that in all 4 types of heatsinks, 7-fin pin types had 4 to 20% lower thermal resistance and 20 to 100% higher convection heat transfer coefficient compared to the 5- and 9-fin pin types respectively. When comparing the heatsinks with the same number of fins, it was observed that the 7 and 9-fin types of heatsinks with conical fins have lower thermal resistance and higher convection heat transfer coefficient than other types of heatsinks with the same number of fins, The conical fins having more than 81 % convection heat transfer coefficient compared to the plate fin heatsink. It was also observed that in the 5-pin fin heatsink design, the plate-fin heat sink had the lowest amount of heat resistance due to its higher surface area with the flowing air current.
Thermal performance of natural convection heat transfer of nanofluid containing oxytactic microorganisms saturated a square porous cavity under constant and sinusoidal temperature boundary conditions ...is numerically investigated. Scrutinizing the literature review reveals that microorganisms' impact on the rate of heat transfer may be contributory or destructive, depending on the problem under consideration. Accordingly, the objective of the current study is set to remove the detrimental effect of microorganisms on the average Nusselt number seen in some previous studies by applying a periodic temperature distribution on the sidewalls to introduce microorganisms as being an always heat transfer intensifier method. For this aim, the Buongiorno model is adopted to simulate the nanofluid flow and the Darcy model is employed to analyze the fluid flow inside porous media. By the definition of a series of appropriate dimensionless numbers, the governing equations are initially converted to a non-dimensional form of governing equations, and then, they are solved numerically using the FEM approach. The accuracy of the numerical method has successfully been validated by comparing it with the available study in the literature. Simulations are undertaken for different parameters including Rayleigh number, bioconvection Rayleigh number, bioconvection Peclet number, and bioconvection Lewis number. Obtained results are provided in the form of tabular and graphical contours related to streamlines, isothermal lines, isoconcentration of nanoparticles, oxygen, and microorganisms. Based on the outcomes, it is concluded that opposed to the constant wall temperature in which microorganisms’ presence leads to the Nusselt number attenuation for the majority of the considered cases, in sinusoidal temperature distribution, microorganisms lead to improvement of the heat transfer in all considered cases. These new findings will likely lead to revolutionary changes in the use of microorganisms in the heat transfer industry. Several applications exist for the concepts developed in this study, including cooling towers, microbial fuel cells, and nanotechnology-based bioconvection.
The heating and cooling process is a major industrial challenge. The efforts to improve the design of heat transfer improvement mainly center around expanding the heat transfer area (through the ...geometry of the heat exchanger) and inducing turbulence to eliminate the boundary layer. A solution to increase the thermal efficiency of the heat exchanger and reduce costs is the use of materials such as nanofluids with ideal thermal and thermophysical properties. Here, to enhance the effectiveness of nanofluids and prevent sedimentation, atomic stabilization was the main focus by combining surfactants with nanofluids at specific weight concentrations and applying ultrasonic vibrations to increase stability. In this paper, the influence of using Graphene oxide (GO)/water and AL2O3/waternanofluids and the GO–AL2O3 /water hybrid nanofluid was investigated at 0.01 %, 0.02 %, 0.03 % wt concentrations. The effect on heat transfer and thermal efficiency of a plate heat exchanger relative to the base fluid (water) was examined. The nanofluids were stabilized in several stages to optimize the thermodynamic properties of the base fluid. The thermal efficiency of the nanofluids (η) reaches to its maximum at the highest weight concentration (0.03 %) with GO nanoparticles at 37 %, AL2O3 at 21 %, and the GO–AL2O3 hybrid at 26 %. GO nanoparticles had the most significant impact on the heat exchanger performance, with an optimized heat exchanger performance of 15.94 %, followed by the hybrid at 11.86 %, and AL2O3 at 7.4 %.
Water has been considered one of the most important human needs since the beginning of human existence. This experimental study investigates the impact of utilizing hybrid nanomaterials ...(Fe3O4 + Graphene oxide) in phase change material (NPCM) under consideration of magnetic field on the production of a uniquely designed stepped solar still. The major aim of this research is to compare three different geometric hybrid NPCM chambers’ performance on the daily production of the stepped solar still. So 4 cases of experiments have been set and performed, namely, stepped solar still 1. Without NPCM, 2. With rectangular hybrid NPCM chambers, 3. With triangular hybrid NPCM chambers, and 4. With semi-circular hybrid NPCM chambers. To add the hours of the distillation process after sunset, the hybrid NPCM was applied. Cases 2 to 4 were experimented with under the permanent magnetic field, too. The daily productivity of Case 1, Case 2, Case 3, and Case 4 without magnetic field were 900 ml/day, 1580 ml/day, 1663 ml/day, and 1730 ml/day, respectively. The outputs indicated that Case 4 had the best accomplishment among all experiment cases. Case 4 of the experiment under the magnetic field yielded the highest daily efficiency of 15.6 %, whereas Case 1 only achieved 7 %. The daily productivity of the stepped solar still with semi-circular NPCM chamber, triangular NPCM chamber, and rectangular NPCM chamber has been enhanced by 92 %, 85 %, and 75 % without magnetic field and 131 %, 113 %, and 100 % under permanent magnetic field, respectively.
•A newly stepped solar still with an evaporative part was designed, constructed, and developed.•Improving the thermal conductivity of PCM by utilizing hybrid nanomaterial.•Application of hybrid NPCM chambers enhances the daily productivity of stepped solar still.•A permanent magnetic field amended the thermal conductivity hybrid NPCM.•Improved the distillate yield of stepped solar still using semicircular hybrid NPCM chambers under a constant magnetic field.
In this work, hydrodynamics and heat transfer of alumina–water nanofluid in a microchannel heat sink (MCHS) are simulated and discussed. Attention in focused to analyze how the use of nanofluids as ...well as vertical/horizontal porous substrates on the channel walls may alter performance of the system, compared to other design variables. To this aim, a three–dimensional solid–fluid conjugate model in conjunction with the two–phase mixture model for the nanofluid and the Dacry–Brinkman–Forchheimer model for the porous medium is utilized. Sensitivity analysis of design variables is performed using the Taguchi method and analysis of variance (ANOVA). The mean temperature of the CPU surface, the overall thermal resistance, the required pumping power, and the figure of merit are considered as the performance parameters. An L27 orthogonal array is utilized as the experimental plan for the current design variables including thickness of the vertical/horizontal porous substrates, material of the MCHS and the porous substrates, the inlet velocity, and the nanoparticles fraction. It is found that the highest contribution on the mean temperature of the CPU surface, the overall thermal resistance, and the figure of merit belongs to the material of the MCHS and the porous substrates.
By the expansion of production from source-related unconventional petroleum resources, accurate approximation of Total Organic Carbon (TOC) through well logs has become progressively important. ...Accordingly, recent studies have mainly focused on increasing the precision of TOC estimation by using different types of AI techniques and/or optimizing algorithms. Along with utilizing these approaches, this study emphasized on removing an unaddressed source of error inherited from lithological heterogeneity with the same goal. Like organic matter quantity, lithological variations within a source interval also induce well log responses, which may interfere with the training process of Artificial Intelligence (AI) techniques. In the present research, the effect of lithological variations on the performance of TOC estimators was evaluated by employing Adaptive Neuro Fuzzy Inference System (ANFIS) and Multilayer Perceptron network (MLP). Firstly, ANFIS and MLP models were constructed and trained using a database containing different lithologies (original models). Then, a new methodology was developed based on modeling the relationship between log data and TOC values for each type of lithology (litho-based method). The result showed that the litho-based method estimates more reliable and accurate TOC values, proving the adverse effect of lithological variations on the original models. Furthermore, the litho-based ANFIS models provide the most promising results. Since metaheuristic algorithms are usually employed to optimize AI techniques, Genetic Algorithm (GA) and Particle Swarm Optimization (PSO) were also implemented into the original models (hybrid models). Accuracy of TOC values estimated by the hybrid models is slightly higher than those derived from the original models. However, these hybrid approaches are not as efficient as the litho-based method. Applicability of the proposed approach was guaranteed by performing it over Pabdeh source rocks in a well of SW Iran. Based on its high efficiency, the newly developed litho-based method can be used as a powerful tool to reliably evaluate unconventional hydrocarbon resources, as well as the potential of the conventional petroleum sources. Moreover, it can be utilized, instead of/along with traditional optimization approaches, to approximate other geochemical factors as well as petrophysical parameters from log data.
•Affectability of TOC estimators from lithological variations were evaluated.•A method was developed to eliminate the adverse effect of lithological variations.•The newly developed litho-based method estimated the most promising TOC values.•Applicability of the proposed method was approved by applying it over a case study.•This method can be used to reliably evaluate unconventional hydrocarbon resources.
