non-Newtonian Cases Research Articles

Numerical pore-scale investigation of two-phase displacement with non-Newtonian defending fluid

In the petroleum engineering and chemical industries, fluids engaging in displacement often have non-Newtonian properties, even though many former studies assume constant viscosities in the defending fluid. In this study, the computational fluid dynamics approach was performed in a two-dimensional model with uniformly distributed disks. This arrangement helps reveal the phenomenon and mechanics of how non-Newtonian characteristics of defending fluid affect two-phase displacement in porous media. Both global (in the whole medium) and regional (in the pore throat) studies revealed that shear-thinning makes capillary force and the pressure in the invading fluid decisive and leads to a uniform pattern. Meanwhile, the shear-thickening causes fingering due to the pressure drop in the defending fluid that becomes decisive. Cases of increasing injection rates were investigated to verify their ability to improve efficiency. The results verified that increased injection rates are effective in shear-thinning cases but energy-intensive when it comes to costs in shear-thickening cases. Finally, the viscosity ratio and capillary number (M-Ca) diagram were extended by plotting non-Newtonian cases as lines to consider viscosity variation. An estimation method was presented, which calculates the characteristic viscosity and locates non-Newtonian cases on an M-Ca diagram. This work can serve as a reference for enhanced oil recovery method development and microfluidic manipulation.

Evaluation of the non-Newtonian lattice Boltzmann model coupled with off-grid bounce-back scheme: Wall shear stress distributions in Ostwald-de Waele fluids flow.

We present a comprehensive analysis of the non-Newtonian lattice Boltzmann method (LBM) when it is used to simulate the distribution of wall shear stress (WSS). We systematically identify sources of numerical errors associated with non-Newtonian rheological behavior of fluids in off-grid geometries. We implement the single relaxation time, Bhatnagar-Gross-Krook (BGK), and multiple relaxation time (MRT) collision operators and investigate flow in a two-dimensional channel aligned with lattice directions and off-grid Hagen-Poiseuille flow of Ostwald-de Waele (power-law) fluids. As for boundary conditions, we implement constant body force-driven and pressure-driven flows. These two boundary conditions have different numerical challenges, which include numerical stability, accuracy, mass conservation, and compressibility effects, which are inherent in the LBM method. Our results indicate that MRT, when the relaxation times are adequately tuned in the non-Newtonian case, significantly improves the WSS distribution accuracy and the numerical stability of the LBM. MRT also enhances the stability and accuracy for non-Newtonian fluids compared with the Newtonian case, meaning that it is questionable if a BGK collision operator is appropriate to use in a non-Newtonian case with off-grid boundaries. When analyzing the non-Newtonian LBM in the context of staircase walls and interpolated bounce-back (IBB) walls, a MRT collision operator with the appropriate choice of tunable relaxation times makes it possible to achieve numerically accurate results without a significant increase in grid resolution for matching to the analytical solution of WSS distributions. In analyzing the non-Newtonian flows, we show that the viscosity dependency of bounce-back walls in the BGK-LBM deviates from the results obtained under Newtonian assumptions. The power-law index further influences these discrepancies, and errors caused by the viscosity dependency of the bounce-back boundary conditions can be effectively mitigated by implementing the MRT procedure. Results show that non-Newtonian fluids, in contrast with the Newtonian assumption, encounter a greater mass imbalance when flowing through a periodic system with IBB walls. MRT can address this challenge, as it allows for independent adjustments of physical relaxation times and enhances mass conservation in the case of non-Newtonian fluids. In pressure-driven non-Newtonian flows, there is a significant impact of bulk viscosity. This aspect is often overlooked in Newtonian simulations but can significantly impact fluid adapting to rapid changes in local effective viscosity. One of our main conclusions is that the MRT collision operator with tuned relaxation times can effectively resolve numerical problems caused by non-Newtonian rheological properties and off-grid geometries. We also provide practical guidelines for selecting the most suitable simulation approach.

Convective heat transfer efficacy of an experimentally observed non-Newtonian MWCNT-Fe[formula omitted]O[formula omitted]-EG hybrid nanofluid in a driven enclosure with a heated cylinder

This study provides an in-depth analysis of the heat transfer (HT) characteristics of a hybrid nanofluid (HNF) composed of Multi-walled carbon nanotubes (MWCNT), Iron oxide (Fe3O4), and Ethylene glycol (EG), which is loaded in an enclosure with a heated cylinder. As per the exploratory report, this HNF exhibits Newtonian and non-Newtonian behavior depending on the percentage of nano-constituents suspended in the base fluid EG. The governing equations describing the convective HNF flow associated with the boundary conditions are numerically solved using the finite volume method. The study explores the HT performance of a loaded HNF by varying the volume fractions (ϕ), the driving condition of the vertical sides, and the aspect ratio (W∗) of the enclosure. The study investigates the variation of the Richardson number (Ri=0.01∼100) concerning the interactions between shear and buoyancy forces executed on the HNF. The study finds that the combination of the lower aspect ratio W∗=2.1 filled with non-Newtonian HNF with ϕ=1.8% in the forced convection regime (Ri=0.01) and the condition of both aiding and opposing forces applied to the side walls shows superior HT performance. The non-Newtonian HNF with ϕ=1.8% shows HT enhancement of 9.27% for aiding forces and 39.63% for opposing forces when Ri=0.01, revealing ultimate enhancement in the average Nusselt number (Nuavg). The study also investigates entropy production (Savg) from a thermodynamics perspective to assess the system’s thermal performance. The value of Savg is about 11.54 for ϕ=1.8% and Ri=0.01, and that value is comparable for both aiding and opposing force conditions. Results conclude that HT consistently enhances with nanoparticle addition in the forced convection regime. However, HT enhancement is only observed for non-Newtonian cases of HNF in the natural convection regime, suggesting the limitation of the HNF usage in the HT study. Additionally, the study discusses and compares different simulation results to comprehensively evaluate the HT characteristics and the system’s thermal performance, guiding the best benefit of the studied hybrid nanofluids in a thermal engineering system.

Thermal radiation and propagation of tiny particles in magnetized Eyring–Powell binary reactive fluid with generalized Arrhenius kinetics

The interest in improving the industrial and engineering working fluid for optimal productivity inspired studies on various fluid materials. Cauchy stress tensor fluids with suitable non-Newtonian rheological properties will enhance industrial fluids. Thus, Eyring-Powell fluid with applicable properties serves as a platform to promote engineering base fluid materials. As such, this study examines tiny particle thermal radiation and propagation in binary reactive Eyring-Powell with generalized Arrhenius kinetics fluid. A theoretical partial derivative boundary value model is developed and transformed into an applicable invariant model via similarity quantities. A Chebyshev collocation method is adopted to solve the model, and the outcomes quantitatively and qualitatively agree with the existing ones. The impact of fluidic terms on the Newtonian and non-Newtonian fluid cases is investigated, and the tiny particle propagation in the Eyring-Powell binary reactive fluid is enhanced with rising thermal radiation.

The impact of multiple stenosis and aneurysms on arterial diseases: A cardiovascular study

The comparative effect of serial stenosis and aneurysms arteries on blood flow is examined to identify atherosclerotic diseases. The finite element approach has been used to solve the continuity, momentum, and Oldroyd-B partial differential equations to analyze the blood flow. Newtonian and non-Newtonian both cases are taken for the viscoelastic response of blood. In this study, the impact of multiple stenotic and aneurysmal arteries on blood flow have been studied to determine the severity of atherosclerosis diseases through the analysis of blood behavior. The novel aspect of the study is its assessment of the severity of atherosclerotic disorders for the occurrence of serial stenosis and aneurysm simultaneously in the blood vessel wall in each of the four cases. The maximum abnormal arterial blood flow effect is found for the presence of serial stenoses compared to aneurysms which refers to the severity of atherosclerosis. At the hub of stenosis, the blood velocity magnitude and wall shear stress (WSS) are higher, whereas the arterial wall normal gradient values are lower. For all cases, the contrary results are observed at the hub of the aneurysmal model. The blood flow has been affected significantly by the increases in Reynolds number for both models. The influence of stenotic and aneurysmal arteries on blood flow is graphically illustrated in terms of the velocity profile, pressure distribution, and WSS. Medical experts may use this study's findings to assess the severity of cardiovascular diseases.

Nonlinear buoyancy driven MHD Reiner–Rivlin nanoliquid flow with quadratic radiation

The present study investigates the dynamics of Reiner–Rivlin nanofluid flow past an inclined flat plate considering quadratic radiation, external magnetic field and nonlinear buoyancy. Appropriate similarity transformations are employed to transform the mathematically modeled equations and are then resolved using the finite-difference based bvp5c scheme, which implements the four-stage Lobatto IIIa formula, in MATLAB. A comparative study between the transport phenomena of non-Newtonian and Newtonian case is also performed. It is observed that the Newtonian case exhibit higher solutal and thermal fields when compared to the non-Newtonian case. However, the results are reversed in the case of velocity profile. The Reiner–Rivlin nanofluid has improved heat transfer rate and drag coefficient characteristics than the Newtonian fluid. Augmentations in the inclination angle descend the velocity profile and ascend the thermal and solutal fields. The increment in the radiation parameter and Hartmann number causes an increment in the nanoliquid temperature. It is also observed that the velocity profile is directly proportional to the changes in the buoyancy ratio. Moreover, the present study has applications in the field of plasma studies, aerodynamics, and cooling systems.

A Computational Fluid Dynamics Enhanced Oil Recovery Formulation Based on the Volume Average Procedure on the Full Momentum Equation: Effects of Polymer Solution Injection in Real Reservoirs with Anisotropic Permeability

Summary In this work, we propose a new methodology to simulate the process of enhanced oil recovery (EOR) in a 3D domain, considering a non-Newtonian fluid phase. The mass balance for the two phases and the balance of momentum are based on the volume averaging theory, which upscales the information on the microscale to make viable the solution in a real case. The full balance of momentum is used in place of the usually adopted Darcy’s law, and the equations are written for each phase in terms of porosity and fluid saturation. The equations are introduced in a new numerical solver developed for the OpenFOAM toolbox, which is an open-source C++ library created to simulate problems of computational fluid dynamics (CFD). First, the methodology is verified by comparing the results obtained from the volume averaging theory equations with Darcy’s law. Then, Newtonian and non-Newtonian cases for Buckley-Leverett, 2D, and 3D meshes are presented. We also present cases with a 3D mesh in a domain extracted from a real reservoir and properties of real injector fluids. The present approach is able to accommodate anisotropic permeability, heterogeneity, and non-Newtonian effects. We compare fluid saturation over time for the different cases as well as the accumulated volume of oil over time and the flow output of the domain. The simulations performed were able to demonstrate the effectiveness of polymeric solutions, comparing polyacrylamide (PAA) and polymeric surfactant (PS) cases with different concentrations, for better use in the production of available resources in reservoirs. In the five-spot cases with polymeric solutions, lower flow rates are achieved when the concentration is increased and the oil production until breakthrough is up to 45% higher when compared with water injection.

Multi-objective study using entropy generation for Ellis fluid with slip conditions in a flexible channel

A mathematical model is developed to investigate the entropy generation on peristaltic transport of the Ellis fluid through a uniform two-dimensional symmetric channel with elastic nature of the walls. An analysis of heat and mass transfer is also made to examine the effects of viscous dissipation. To simplify the governing equations, nondimensional analysis with low Reynolds number and large wavelength is done. Solutions of the problems are presented via a NDSolve Mathematica numerical technique. The effects of various parameters on flow characteristics, thermal characteristics and species characteristics have been computed and physically interpreted. The numerically acquired solutions are studied graphically for the effective analysis of the flow. The velocity and temperature profiles are parabolic in nature. Higher values of elastic parameters and chemical reaction parameters rapidly increase concentration profile for Newtonian case as compared to non-Newtonian case. The outcomes of this model can be applicable in various fields of biomedical engineering where smart peristaltic pumps can be engineered to transport the biological fluids without any contamination, i.e., electromagnetic peristaltic micro pumps.

Application of immersed boundary methods to non-Newtonian yield-pseudoplastic flows

The interaction force between fluid and particles in particulate flows is highly dependent on the rheology of fluid. In some engineering applications, like mineral processing, the rheological behaviour of the carrier fluid is characterized by a yield-pseudoplastic non-Newtonian model. The immersed boundary method (IBM) is a numerical strategy to simulate the interaction between phases in the particulate systems using a Cartesian fixed grid. It imposes the solid boundary condition in the computational domain through a modification (e.g. a forcing term) in the governing equations. However, there is still little study in the literature discussing the applicability of different IBMs to yield-pseudoplastic flows. In this paper, the numerical methodology in several versions of immersed boundary methods, including the Volume Penalization IBM (VP-IBM), Indirect Imposition of Discrete Forcing IBM (ID-IBM), and Direct Imposition of Discrete Forcing (DD-IBM), is described. The numerical implementation of the methods is first validated using Newtonian benchmark cases. Then the solvers are utilized for the simulation of yield-pseudoplastic cases with stationary or moving particles. The investigation shows that in the explicit forcing methods, like VP-IBM and ID-IBM, the forcing procedure is conducted using an intermediate solution over the entire computational domain. The dependence of viscosity to strain rate in non-Newtonian cases leads to an inevitable sharp change in viscosity near the solid surface, giving rise to stiffness of the intermediate solution in the interface region. This makes the explicit forcing approaches based on intermediate solution incompatible with the flows with non-Newtonian yield-pseudoplastic rheology. On the other hand, the implicit forcing used in DD-IBM directly implements the boundary conditions on the boundary cells, making this method free from the perturbations related to the highly viscous solid region. In this regard, the simulation with the Direct Imposition IBMs like ghost-cell shows a good agreement between the predicted results and the experimental measurements for the stationary/moving cases. Therefore, it is shown that the DD-IBM is a reliable approach to modelling non-Newtonian flows.

Machine learning-augmented fluid dynamics simulations for micromixer educational module.

Micromixers play an imperative role in chemical and biomedical systems. Designing compact micromixers for laminar flows owning a low Reynolds number is more challenging than flows with higher turbulence. Machine learning models can enable the optimization of the designs and capabilities of microfluidic systems by receiving input from a training library and producing algorithms that can predict the outcomes prior to the fabrication process to minimize development cost and time. Here, an educational interactive microfluidic module is developed to enable the design of compact and efficient micromixers at low Reynolds regimes for Newtonian and non-Newtonian fluids. The optimization of Newtonian fluids designs was based on a machine learning model, which was trained by simulating and calculating the mixing index of 1890 different micromixer designs. This approach utilized a combination of six design parameters and the results as an input data set to a two-layer deep neural network with 100 nodes in each hidden layer. A trained model was achieved with R2 = 0.9543 that can be used to predict the mixing index and find the optimal parameters needed to design micromixers. Non-Newtonian fluid cases were also optimized using 56700 simulated designs with eight varying input parameters, reduced to 1890 designs, and then trained using the same deep neural network used for Newtonian fluids to obtain R2 = 0.9063. The framework was subsequently used as an interactive educational module, demonstrating a well-structured integration of technology-based modules such as using artificial intelligence in the engineering curriculum, which can highly contribute to engineering education.

Solar thermal energy performance on mono/trihybrid nanofluid flow through the evacuated thermal collector tube

Solar thermal energy is a versatile and sustainable form of energy. It has vast applications and can be used to reduce fossil fuel consumption. The sun's heat harnesses this renewable energy; therefore, the energy transmission rate plays a significant role here. This article gives the idea of a new geometric design of solar thermal collector tubes for multiple uses and materials to be used on the tube's outer layer to maximize heat absorption. For this purpose, we investigated velocity, temperature, and heat transfer rates due to different nanoparticle (Cu/Al2O3/GO) combinations. We assumed the flow of Newtonian/non-Newtonian nanofluids flowing through the coaxial region of the cylindrical shape solar tubes. Here, water and seawater are considered for the Newtonian case, and sodium alginate is regarded for the non-Newtonian case. The governing equations of the flow are converted into ODEs with the help of similarity variables and solved numerically using the Keller box method. The MATLAB code for the Keller box method has been developed to plot graphical results. The primary outcomes are exhibited through graphs and tables. It is perceived that the temperature and heat transfer rates in Newtonian and non-Newtonian fluids are enhanced due to the trihybrid (Cu + Al2O3+GO) combination. This work can be utilized in an evacuated solar thermal system and gives the idea to develop a sustainable solar thermal system for multipurpose usage.

Non-Newtonian Electrically Conducting Nano Fluid Heat and Mass Transfer Analysis Over a Vertical Cone with Convective Boundary Condition

Electrically conducting, thermally radiative non-Newtonian Nano fluid heat and mass transfer features over a vertical permeable cone with chemical reaction and convective boundary condition is numerically scrutinized in this article. The system of transformed mathematical equations are numerically solved by utilizing the most efficient Finite element method. Brownian motion, Magnetic field, Lewis number, Biot number, Chemical reaction, Buoyancy ratio, Suction/Injection, Prandtl number, Thermal radiation parameters influence on Nanoparticle volume fraction, temperature and velocity scatterings is evaluated and the outcomes are plotted through graphs. Furthermore, the non-dimensional rates of concentration and heat transfer values are also premeditated. The temperature of the Nano fluid amplifies with rising values of Brownian motion parameter and this augmentation is more in non-Newtonian case than the Newtonian case. Addition of Convective boundary condition into the liquid flow intensifies the rates of heat transfer of non-Newtonian nanoliquid.

Falkner–Skan slip flow of non-Newtonian fluid over a moving and nonlinearly radiated wedge with variable heat source/sink and viscous dissipation

Analyzed in this paper is an investigation of the impacts of the varying source of heat or thermal sink and viscous dissipation on Casson fluid flow from a moving wedge by considering thermal and momentum slips in a mathematical model. Regarding the regulation of concentration fields, we incorporated the Soret and Dufour phenomena. The outcomes are analyzed numerically by using the shooting technique. The governing parametric effects of the flow characteristics are revealed graphically. We also presented the local Sherwood and Nusselt number values for non-Newtonian fluid (Casson fluid) and Newtonian. It is discovered that the thermal and concentration boundary layer is more extensive in Casson fluid while equated with the Newtonian fluid. The thermal and mass transmission in Newtonian fluid is significantly larger than in non-Newtonian fluid. The heat source/sink, Eckert number and Dufour number boost the rate of thermal transport and depreciate the rate of mass transport for both the Newtonian and non-Newtonian fluid cases.

Convective Conditions on 3D Magnetohydrodynamic (MHD) Non-Newtonian Nanofluid Flow with Nonlinear Thermal Radiation and Heat Absorption: A Numerical Analysis

Three-dimensional flow of non-Newtonian nanofluid with nonlinear thermal radiation and heat absorption is established numerical analysis. We are taken that, the nonlinear thermal radiation and heat absorption on porous stretching sheet. Moreover, we have to consider the Magnetohydrodynamic and convective conditions within the fluid motion on stretching surface. The similarity variables are implemented to translate the nonlinear PDE into a set of coupled system of ODE which are solved numerically via RKF (“Runge-Kutta-Fehlberg”) 4th order based on shooting procedure. We obtained the dimensionless parameters on velocity, temperature and concentration profiles and as well as skin friction coefficient, Nusselt number and Sherwood numbers are discussed through graphs. In this study, we found interesting results, that is the non-Newtonian fluids is most significant on velocity, temperature, and heat transfer rate is high significant in non-newtonian case when compared with nanofluid case with various statistical values of Pr (“Prandtl number”), θw (“Temperature ratio parameter”) and Nt (“Thermophoresis parameter”), respectively.

A NUMERICAL STUDY ON HEAT TRANSFER FOR MHD FLOW OF RADIATIVE CASSON NANOFLUID OVER A POROUS STRETCHING SHEET

The current study deals with the heat transfer of the steady two-dimensional MHD Casson nanofluid flow over a non-linearly stretched porous sheet associated with viscous dissipation, chemical radiate parameters and thermal radiation. Using the appropriate similarity transformation, the non-linear partial differential equations are transformed into a system of coupled non-linear ordinary differential equations which are further numerically solved using a MATLAB built-in solver bvp4c (Boundary value problem of fourth-order). The comparison reveals an excellent agreement which proves the validation of the numerical approach. The effect of various MHD parameters on the velocity, temperature and nanoparticle concentration are discussed graphically whereas its impact on heat and mass transfer rate are shown in tabular form as Nusselt number and Sherwood number respectively. Enhancement in temperature profile is observed as a result of the increased value of the radiation parameter and Brownian motion parameter. In this study, both Newtonian and non-Newtonian cases are studied separately for each parameter. Moreover, this study demonstrates, when a porous sheet is stretched non-linearly under chemical and thermal radiation, the Casson nanofluid controls the temperature and nanoparticle concentration better than the Newtonian nanofluid.

Comparative analysis to examine the heat transmission enactment of hyperbolic tangent cylindrical flow: An application to PTSC

The current work deals with heat diffusion in hyperbolic tangent cylindrical film movement in the occurrence of Darcy, buoyancy, magnetic field, radiative heat, and irregular temperature sink/source. A precise model was recognized to inspect the same and solved numerically through the bvp5c MATLAB scheme. The results are explored for Newtonian and non-Newtonian cases to understand the rheological advantage of hyperbolic tangent fluid. The consequences are pondered with the help of pictographic and mathematical assessments. The liquids with tangent hyperbolic rheological conduct oblige for active heat diffusion rate. Therefore, these fluids can be used in Parabolic Trough Solar Collector for further heat transmission rate and operative usage of solar energy.

Effects of non-Newtonian viscosity on arterial and venous flow and transport

It is well known that blood exhibits non-Newtonian viscosity, but it is generally modeled as a Newtonian fluid. However, in situations of low shear rate, the validity of the Newtonian assumption is questionable. In this study, we investigated differences between Newtonian and non-Newtonian hemodynamic metrics such as velocity, vorticity, and wall shear stress. In addition, we investigated cardiovascular transport using two different approaches, Eulerian mass transport and Lagrangian particle tracking. Non-Newtonian solutions revealed important differences in both hemodynamic and transport metrics relative to the Newtonian model. Most notably for the hemodynamic metrics, in-plane velocity and vorticity were consistently larger in the Newtonian approximation for both arterial and venous flows. Conversely, wall shear stresses were larger for the non-Newtonian case for both the arterial and venous models. Our results also indicate that for the Lagrangian metrics, the history of accumulated shear was consistently larger for both arterial and venous flows in the Newtonian approximation. Lastly, our results also suggest that the Newtonian model produces larger near wall and luminal mass transport values compared to the non-Newtonian model, likely due to the increased vorticity and recirculation. These findings demonstrate the importance of accounting for non-Newtonian behavior in cardiovascular flows exhibiting significant regions of low shear rate and recirculation.

A Mechanistic Model for the Two-Phase Slug Flow of the Purely Viscous Non-Newtonian Liquids through Pipes

Summary Mechanistic slug models generally depend on several empirical correlations. This work presents an extended model, which incorporates a recently theoretically developed family of friction equations for purely viscous non-Newtonian fluids to reduce this dependency. In contrast to other models where a fixed transition Reynolds number is used, a proper rheology-dependent laminar-to-turbulent transition criteria has been adopted. Finally, to fully specify the characteristics of the slug flow, a new model is introduced for the slug frequency, by balancing the pressure forces and the drag over the gas bubble. The resulting model requires just one empirical coefficient, drag coefficient of the bubble, which depends on the rheology of the fluids and diameter of the pipe. The developed models have been extensively verified with the experimental data, for the two-phase flows with Newtonian and non-Newtonian (power law and Bingham) liquid phase. Our mechanistic model predicts the pressure drop of the experimental data within ±20% error range, while it does not introduce any new empirical coefficient for the non-Newtonian case. This model, besides its simplicity and accuracy, successfully captures the physical trends in experimental data where other available models fail. The frequency model with calibrated drag coefficient reproduces the experiments with less than 30% error, while one can find a universal drag coefficient which can reproduce most of the experimental observations within the same error range. To summarize, the proposed models can fully characterize two-phase slug flows in presence of a non-Newtonian purely viscous fluid phase.

Understanding the dynamics of chemically reactive Casson liquid flow above a convectively heated curved expanse

This paper studied the simulation of partial differential equations that model Casson fluid dynamics on a curved surface when Lorentz force, viscous dissipation, first-order chemical reaction, convection, uneven heat sink/source, and mass transmission at the wall are significant. An appropriate similarity conversion transforms the governing equations into non-dimensional ODEs. The bvp5c Matlab package is utilized to acquire the velocity, temperature, and concentration outcomes. This work aims to attain simultaneous solutions for Newtonian and non-Newtonian flow cases and analyze the reasons for deviation in flow and thermic border thicknesses. Augmenting the parametric curvature values inflates the velocity profiles and declines the thermal transmission rate. Also, the heat transport rate in the brunt of uneven heat source and viscous dissipation is extensive for non-Newtonian liquid compared with the Newtonian fluid.

Numerical simulation of the heat transfer process of a coiled tube for viscous fluids

This study presents the results of a numerical simulation in a helical coiled tube for Newtonian and non-Newtonian fluids in laminar regime. As a practical contribution, the numerical simulations use non-Newtonian fluids, the rheological properties of which are experimentally measured. In both non-Newtonian fluids, at the helical section, the heat transfer rate was higher than that at the straight section. For the fruit juice, the heat transfer coefficient ( h w ) reached values of 1000 and 1350 W/m 2 K at the coil, which were 73% and 126% higher than in the straight section, for an Re g of 255 and 634, respectively. For the carboxyl methyl cellulose solution, these differences ranged between 76% ( Re g = 255) and 210% ( Re g = 634), reaching h w values at the coil of 1950 and 2700 W/m 2 K. In all non-Newtonian cases, fluid mixing was improved at the coil section. This influenced the viscosity variability along the coil, especially for the fruit juice, with a pronounced pseudoplastic behaviour (flow behaviour index of 0.5). This viscosity variation was more influenced by the strain rate than the viscosity change with temperature, as the fruit juice showed a moderate energy activation (8.2 kJ/mol). • High computational cost model used for helical coiled tube. • Numerical simulation of Newtonian fluids validated with experimental setup. • Good agreement obtained between numerical and experimental results. • Local Nusselt number increased at the coiled section up to 210%.