CFD Simulation of Rheological Model Effect on Cuttings Transport

Foam, as a non-Newtonian fluid, plays an important role in the underbalanced drilling technique in oil field development. The rheological properties of drilling fluids, such as foam, have a direct effect on flow characteristics and hydraulic performance. Two rheological models—the Herschel–Bulkley model and power law—were fitted to two foam systems in this study. Computational fluid dynamics (CFD) was used to simulate the effect of the rheological models on solid–liquid (cuttings transport) hydraulics in concentric and eccentric annulus during the foam drilling operation. The simulation results are compared to the experimental data from previous studies. The results of CFD using the power law model are in good agreement with experimental results in horizontal annulus with respect to the Herschel–Bulkley model with relative error less than 8%. Thus, for CFD cuttings transport for simulations in inclined and horizontal annulus, it is best to use the power law's rheological model parameters.     

Turbulent Convective Heat Transfer and Pressure Drop of Graphene–Water Nanofluid Flowing Inside a Horizontal Circular Tube

Turbulent convective heat transfer of graphene–water nanofluids with various concentrations inside a uniformly heated circular tube is studied experimentally. For this purpose, experiments are conducted to measure thermal conductivity, viscosity, pressure drop, and heat transfer coefficient. Results show enhancement of thermal conductivity and moderate increment of viscosity with addition of low amounts of nanoparticles. Moreover, heat transfer coefficient shows relatively high augmentation, and pressure drop remains unchanged. The maximum enhancements are 10.30%, 4.95%, and 6.04% for thermal conductivity, viscosity, and heat transfer coefficient, respectively. UV–Vis spectroscopy results show that the nanofluids are highly stable.     

Experimental Study of Heat Transfer of a Car Radiator with CuO/Ethylene Glycol-Water as a Coolant

Conventional heat transfer fluids such as water and ethylene glycol (EG) can be used for cooling fluids in car radiators, and have relatively poor heat transfer performance. One method for increasing heat transfer in car radiators uses nanofluids. Nanofluids as a new technology are obtained by dispersing nanoparticles on the base fluids. In the present study, CuO (60 nm) nanoparticles were used in a mixture of water/EG as a base fluid. Then, the thermal performance of a car radiator was studied. The experiment was performed for different volumetric concentrations (0.05–0.8 vol%) of nanofluids of different flow rates (4–8 lit/min) and inlet temperatures (35, 44, 54°C). The results showed that nanofluids clearly enhanced heat transfer compared to the base fluid. In the best condition, the heat transfer coefficient enhancement of about 55% compared to the base fluid was recorded.     

Pressure Drop and Performance Characteristics of Water-Based Al2O3 and CuO Nanofluids in a Triangular Duct

An experimental study is performed to determine the pressure drop and performance characteristics of Al₂O₃/water and CuO/water nanofluids in a triangular duct under constant heat flux where the flow is laminar. The effects of adding nanoparticles to the base fluid on the pressure drop and friction factor are investigated at different Reynolds numbers. The results show that at a specified Reynolds number, using the nanofluids can lead to an increase in the pressure drop by 35%. It is also found that with increases in the Reynolds number, the rate of increase in the friction factor with the volume fraction of nanoparticles is reduced. Finally, the performance characteristics of the two nanofluids are investigated using the data of pressure drop and convective heat transfer coefficient. The results show that the use of Al₂O₃/water nanofluid with volume fractions of 1.5% and 2% is not helpful in the triangular duct. It is also concluded that at the same volume fraction of nanoparticles, using Al₂O₃ nanoparticles is more beneficial than CuO nanoparticles based on the performance index.     

Improvement in Heat Transfer of a Two-Phased Closed Thermosyphon Using Silver-Decorated MWCNT/Water

Hereby, a comparative study of thermal and thermodynamic properties of nanofluids based on multiwalled carbon nanotubes (MWCNTs) and water is described. The first nanofluid includes pristine MWCNT while the second nanofluid prepared by MWCNT decorated with silver. To achieve the covalent functionalization, morphology of MWCNT-Ag was studied by transmission electron microscopy. Subsequently, the value of the entropy generation and thermal performance of nanofluids (MWCNT/water and MWCNT-Ag/water) were inspected in a two-phased closed thermosyphon (TPCT). The results suggested as the concentration and input power increased, the thermal resistance decreased. Also in different concentrations, the thermal efficiency of nanofluids obeyed the sequence: MWCNT-Ag (1 wt%) > MWCNT-Ag (0.5 wt%) > MWCNT (1 wt%) > MWCNT (0.5 wt%) > water. A variation of the vacuum pressure was also studied in the synthesized nanofluids as compared with pure water. The results were shown a lower pressure drop of MWCNT-Ag/water than MWCNT/water and the water. Also it was found that the higher thermal performance is produced using higher extent of covalent functional groups (with higher thermal conductivity). MWCNT-Ag/water can be an appropriate substitution for the water in the thermal equipment due to the intensive thermal efficiency and/or low thermal resistance compared with pure water.      

Hybrid of Two Heuristic Optimizations with LSSVM to Predict Refractive Index as Asphaltene Stability Identifier

Asphaltene precipitation is a big challenge in the petroleum industry. This motivated us to develop a reliable model between refractive index and SARA fraction as a tool for the diagnosis of asphaltene stability. Least-square support vector machine (LSSVM), due to its several unique advantages, has been successfully verified as a predicting method in recent years. However, the success of LSSVMs depends on the adequate choice of the kernel and regularization parameters. We proposed the combination of two search algorithms to deal with the problem of support vector machine parameter selection. On this basis, we combined coupled simulated annealing (CSA) and the Nelder and Mead Simplex method to optimize the parameters. In this hybrid optimization, first, CSA finds suitable starting values and these are passed to the simplex method in order to tune the result. The LSSVM results are promising and accurate, and outperform both neural network and empirical models existing in literature.      

Experimental Study and Numerical Modeling of Rheological and Flow Behavior of Xanthan Gum Solutions Using Artificial Neural Network

This study investigated effect of temperature, concentration, and shear rate on rheological properties of xanthan gum aqueous solutions using a Couette viscometer at temperatures between 25°C and 55°C and concentrations of 0.25 wt% to 1.0 wt%. The Herschel–Bulkley model described very well the non-Newtonian behavior of xanthan gum solutions. Shear rate, temperature, and concentration affected apparent viscosity and an equation was proposed for the temperature and concentration effect valid for each shear rate. This article also presents an artificial neural network (ANN) model to predict apparent viscosity. Based on statistical analysis, the ANN method estimated viscosity with high accuracy and low error.     

Mechanisms of Non-Newtonian Polymer Flow Through Porous Media Using Navier–Stokes Approach

This study includes solving non-Newtonian Navier–Stokes equation in three-dimensions (real rock images) and two-dimensions (simplified pore geometries) using the finite-difference method. The purpose of this study is to improve understanding of local phenomena leading to the mobilization of residual oil. This involves local pressure variations for non-Newtonian polymers and compares it with Newtonian fluid behavior. When a higher degree of shear thickening is induced, more flow diversion to side channels perpendicular to the main flow path and larger drag on fluids inside side channels will occur. This is consistent with oil mobilization and lowering of residual oil saturation.