Porous Duct Research Articles

Heat transfer analysis of nanofluid flow with entropy generation in a corrugated heat exchanger channel partially filled with porous medium

AbstractHeat exchanger research is mainly exploited to develop and optimize new engineering systems with high thermal efficiency. Passive methods based on nanofluids, fins, wavy walls, and the porous medium are the most attractive ways to achieve this goal. This investigation focuses on heat transfer and entropy production in a nanofluid laminar flow inside a plate corrugated channel (PCC). The channel geometry comprises three sections, partially filled with a porous layer located at the intermediate corrugate channel section. The physical modeling is based on the laminar, two‐dimensional Darcy–Brinkman–Forchheimer formulation for nanofluid flow and the local thermal equilibrium model for the heat equation, including the viscous dissipation term. Numerical solutions were obtained using ANSYS Fluent software based on the finite volume technique and the appropriate meshed geometries. The numerical results are validated with theoretical, numerical, and experimental studies. The simulations are performed for CuO–water nanofluid and AISI 304 porous medium. The coupled effects of porous layer thickness (δ), Reynolds number (Re), and nanoparticle fraction (φ) on velocity, streamlines, isotherm contours, Nusselt number (Nu), and entropy generation (S) are analyzed and illustrated. The simulation results demonstrate that heat transfer enhancement in clear PCC can be achieved using a porous layer insert. For the porous thickness range of [0.1–0.6], the corresponding range of average Nusselt number increase is [35.7%–176.9%], and the average entropy generation is [105.4%–771.9%]. The effect of the Reynolds number is more important in a porous duct than in a clear one. For δ = 0.4 and φ = 5%, the increase of Re in the range of [200–500] induces an increase in average Nusselt number in the range of [80.9%–108.4%] and average entropy in [222.9%–309.1%] comparatively to clear PCC. The effect of φ is practically the same for porous and clear channels. For φ = 5%, the increase on average Nu is about 9%, and entropy generation is 5%. Accordingly, important improvements in heat transfer in PCC can be achieved through the combined effect of flow Reynolds number and porous layer thickness.

Hybrid nanofluid flow and heat transfer in symmetric porous ducts with CuO nanoparticles and multi-walled carbon nanotubes under peristaltic motion

This study focuses on the analysis of peristaltic transport of a hybrid nanofluid comprising deionized water as a base fluid and the multi-walled carbon nanotubes (MWCNTs) and copper oxide (CuO) as nanoparticles within a sinusoidal wavy porous duct, taking into consideration the influence of heat generation or absorption. The inaugural literature piece addresses the utilization of hybrid nanofluid in the context of peristaltic flow within ducts. To simplify the analysis, we have converted the non-dimensional equations into a two-dimensional (2D) coordinate system using the assumptions of a very long wavelength [Formula: see text] and low Reynolds number (Re). The non-dimensional equations governing the behavior of the hybrid nanofluid are then solved numerically using the finite volume method. Numerical solutions for temperature and the 2D peristaltic flow are obtained with the assistance of the Mathematics software MATLAB. These solutions are subsequently represented graphically using MATLAB software. The graphical results highlight several key findings for important parameters. First, it is observed that the pressure rise, temperature profile, and pressure gradient in the hybrid nanofluid (CuMWCNTs/H2O) flow increases as heat generation increases. Furthermore, an increase in the nanoparticle volume fraction of both nanoparticles leads to a decrease in the pressure rise and pressure gradient in the hybrid nanofluid flow. Additionally, the widening of the channel reduces the pressure gradient and pressure rise in the CuMWCNTs/H2O hybrid nanofluid. The analysis also includes the visualization of streamlines for peristaltic transport. These streamlines reveal that an increase in amplitude results in larger bolus sizes, while heightened heat generation has the opposite effect, decreasing bolus sizes. The results of this investigation can be found in various cooling devices as flows in the ducts are very frequently utilized for the cooling process of engines. A further topic is common in applications related to microfluidics, heat exchangers, and biomedical devices where peristaltic pumping is employed. Our results are in 100% agreement with the existing literature in special cases.

Catalytic effects on peristaltic flow of Jeffrey fluid through a flexible porous duct under oblique magnetic field: Application in biomimetic pumps for hazardous materials

Homogenous and heterogeneous reactions play an essential role in polymer production, combustion, ceramic production, catalysis, distillation, and biochemical procedures. As a result of this advancement, a mathematical model is developed to examine the role of catalytic chemical reaction effects on the magneto-hydrodynamic peristaltic transport in a flexible divergent duct containing a non-deformable porous medium as a model for complex hazardous waste bio-inspired pumping mechanisms. The Jeffrey model is utilized to simulate strong non-Newtonian characteristics. Additional multi-physical features included in the model are heat generation, thermal radiation, Hall current, and complaint wall properties along with an inclined (oblique) magnetic field. The long wavelength and low Reynolds number approximations are deployed to transform the primitive conservation equations from a moving boundary problem to a fixed frame. Appropriate transformations are then utilized to render the model dimensionless. The exact solutions are obtained for stream function and velocity. Further, the R-K-Fehlberg integration scheme is applied to solve the energy and concentration equations. Velocity, temperature, concentration, skin friction, and Nusselt number profiles are visualized graphically. Streamline patterns are also included to capture bolus dynamics. Validation with previous simpler studies has been included. A detailed appraisal of key control parameters on transport characteristics is conducted. It is found that velocity is suppressed with elevation in the damping force parameter while it is enhanced with an increment in regime permeability i. e. Darcy number. Both homogeneous and heterogeneous reactions are observed to exert a significant impact on the species concentration. The volume of the trapped fluid bolus size is shown to be an increasing function of the peristaltic wave amplitude ratio. The present work generalizes existing studies to consider catalytic effects on dissipative peristaltic pumping of the Jeffrey fluid with heat generation and radiative flux, aspects which have been neglected in a single model previously. The simulations are relevant to better characterize the complex transport phenomena in nuclear reactor waste transport via biologically inspired pumping designs.

Effects of magnetization and heat transfer on electrically conducting magnetohydrodynamics flow with mixed convection flow over porous duct

The effects of magnetic field and heat transfer problem on incompressible magnetohydrodynamics (MHD) mixed unsteady convective flow of an electrically conducting viscous fluid in a duct filled with a porous medium are investigated. The fluid flow is subjected to an applied uniform magnetic field vertical to the duct and uniform free stream of constant velocity and temperature. The system of nonlinear differential equations governing flow and heat transfer phenomena are derived and reduced into a set of ordinary differential equations using the auxiliary variable method. The reduced equations are solved numerically using Runge-Kutta method associated with slip boundary conditions. The graphical results for velocity, temperature and heat transfer rate are obtained using MATLAB software. It is observed that the velocity profiles increase with an increase of similarity parameter (fI) while temperature gradient decreases rapidly with an increase of similarity parameter (θI) for different values of Grosh number, Magnetization and Prandtl number respectively.

Heat and mass transfer analysis of nonmiscible couple stress fluid in a porous saturated channel

The present flow problem analyzes the impact of radiative heat and mass transfer with inclined magnetic field on thermal exchange and entropy production of two immiscible nature of electrically conducting couple stress fluid in a static porous saturated conduit. In this model, the lower and upper porous regions of the rectangular channel are occupied by two different types of couple stress fluids. The static horizontal parallel plates of the porous duct are completely isothermal and the flow of immiscible fluid through the porous duct develops because of a constant pressure gradient at the entry zone of the duct. The Brinkman model is utilized in the modeling of fluid flow through porous saturated domain and Rosseland’s approximation is utilized to compute the radiative thermal exchange effect on nonmiscible couple stress fluid. In this work, authors have analyzed the effect of various thermo-physical parameters such as the Hartmann number (Ha), permeability parameter (Da), Schmidt number (Sc), Soret number (Sr) and couple stress parameter ([Formula: see text]) on the entropy generation characteristics, Bejan number distribution, thermal behavior, concentration distribution and flow characteristics of immiscible couple stress fluid which passes through the porous channel. The parameters Ha, Da, [Formula: see text], Sc, Sr correspond to magnetic field effect, permeability of porous media, couple stress, mass diffusion and thermal diffusion, respectively. The most significant findings of this research work are as follows: • In a porous saturated channel, the immiscible couple stress fluid velocity, entropy production number and thermal profile get enhanced on increasing the couple stress parameter. • On increasing the Hartmann number and decreasing the permeability of porous region, the thermal properties and entropy production number both decrease. • The couple stress fluid’s concentration field and Bejan number distribution get decreased on enhancing Soret number Sr and Schmidt number Sc. • The entropy generation near the wall of the channel rapidly increases on increasing the Schmidt number and Soret number. The emerging finding of this research work exhibits excellent agreement with previously published work. This research work can be utilized in food processing, petroleum products and chemical process.

Hydro-thermal performance of fabric air duct (FAD): Experimental and CFD simulation assessments

Nowadays, fabric air duct (FAD) systems are the most cost-effective, and aesthetically appealing way to evenly distribute heated or cooled air to large open interior spaces. There is a need to develop a proper procedure to calculate the friction factor and Nusselt number of the air flow inside these types of fabric air ducts because of their great impact on the design of central air conditioning systems. Therefore, the main objective of this research is to carry out laboratory and numerical experiments to establish a certain technique of calculation of the friction factor and Nusselt number inside fabric air ducts and to develop validated CFD air distribution model capable of predicting the air flow pattern and heat transfer parameters inside different configurations of fabric air ducts. By controlling these parameters, FAD systems can be balanced and designed. For this purpose, three fabric air ducts made of porous and non-porous polyester with different outlet ports distribution and have a diameter of 60 cm and a length of 3 m have been experimentally assessed under variation of inlet Reynold numbers ranging from 9.9x103 to 1.47x105. The results showed that the maximum error between laboratory and numerical values for the mean friction factor and mean Nusselt number was 4.9% and 4.8% respectively, which was within an acceptable range according to previous studies. Based on the results analysis empirical correlations were obtained for their importance in achieving a well-balanced FAD system. One of the most significant equations that were obtained in this research was the relationship between the Nusselt number and Reynold number. For porous duct was Nu=127.69Re0.148, non-porous duct 4,8 o'clock air slots was Nu=4.51Re0.49 and non-porous duct 3,9 o'clock air slots was Nu=40.82Re0.139. The relationship between friction factor with Reynold number for porous duct was f=0.251e−0.0000067Re, non-porous duct 4,8 o'clock air slots was f=0.397e−0.000017Re and non-porous duct 3,9 o'clock air slots was f=0.529e−0.000025Re. All correlations are valid only within the range of conditions considered in current experimental study.

Extending the Validity of Basic Equations for One-dimensional Flow in Tubes with Distributed Mass Sources and Varying Cross Sections

Flow problems are solved using so-called fundamental equations and the corresponding initial and boundary conditions. The fundamental equations are the motion equation, the continuity equation, the energy conservation equation, and the state equations. In our paper, we extend the validity of the equation of motion used to describe one-dimensional, steady-state tubular flow to a case in which the mass flow of the medium changes along the tubular axis during the flow. Such flows occur in perforated and/or porous pipes and air ducts. The research in this direction was motivated by the fact that the extension and formulation of the equation of motion in this direction has not been carried out with completely general validity. In the equation of motion used to solve the problems, the isochoric and isotherm nature were assumed. In our paper, we present fundamental equations that formulate differential equations to describe polytrophic and expanding flows.

Simulation for discharging of phase change material within a porous duct utilizing multi layers

Effect of nanoparticles on solidification within a duct with multi air layer was scrutinized in current research. Impose of wavy canal and nanoparticles can augment the solidification rate and these factor were checked in current unsteady modeling. Exergy drop and solid fraction distributions were analyzed. As mass of liquid reduces, exergy drop declines and impose of sinusoidal wall can augment the exergy drop. Cold air make the liquid PCM convert to solid and its temperature augments. With use of sinusoidal wall, better exchange of heat occurs and solidification occurs in lower time. Air temperature reduces as mass of liquid decreases and same behavior was reported for temperature of NEPCM. At t = 1.4hr, Tair of two cases were the same and after this time, temperature of flat plate is greater than another case. After full solidification, temperatures of air for two cases become equal. Solidification time reduces about 26.6% with utilizing wavy surface.

Impact of using single heated obstacle on natural convection inside porous cavity under non-Darcy flow and thermal non-equilibrium model: A comparison between horizontal and vertical heated obstacle arrangements

The current study implements a numerical investigation on natural convection inside non-Darican porous duct to analyse the actions of using a single heated obstacle attached horizontally/vertically at the heated surface under Local thermal non-equilibrium (LTNE). Importance has been given on how the heated obstacle length and its position manipulate the enhancement of natural convection. Solutions confirm that Nu is extremely depends on ratio of thermal conductivity (Kr), obstacle length (Z), obstacle position (X), modified Rayleigh number (Ra*) and inertia coefficient (Fs/Pr*) as compared to heat transfer coefficient (H). Results display that the rising in Z leads to recede free convection activity as compared to the smallest one, where Z and X have extremely impact on Nu. Results displayed that Nus, Nuf and NuT obtained for the horizontal case are higher than vertical case, which reveals a better thermal performance. Optimum enhancement in Nu has been observed when using small Z and it horizontally attached at higher place inside the duct. The density of LTNE regime is extremely reduced with rising in H, Kr and Ra* and reducing in Z and Fs/Pr*. Finally, the horizontal heated obstacle can be advised to be used in heat exchanger for techniques implementing porous media.

Effects of anisotropy on the transition to absolute instability in a porous medium heated from below

The emerging instability of a forced throughflow in a fluid saturated horizontal porous duct of rectangular cross section is investigated. The duct is heated from below by assuming the horizontal boundaries to be at different temperatures. Both the horizontal and the vertical boundaries are impermeable and the basic flow is parallel to such boundaries. The porous medium is anisotropic with different permeabilities in the vertical and horizontal directions. The effect of anisotropy on the onset of buoyancy-driven modal instability and absolute instability is analyzed. The parametric conditions leading to the instability of the basic flow are determined by employing an analytical dispersion relation. The different permeabilities in the vertical and horizontal directions turn out to play opposite roles in the onset of modal instability and in the transition to absolute instability. It is shown that an increasing vertical permeability has a destabilizing effect, while an increasing horizontal permeability has a stabilizing effect.

Comprehensive studies on suitable reaction mechanisms to predict the behavior of high speed reacting flows

In this work, the two dimensional transition of H2-O2 deflagration-to-detonation was examined in some porous closed-ducts by an in-house high speed reacting flow solver in OpenFoam package—a pressure-based/density-based hybrid solver coupled with Godunov-type schemes, including advection Upstream Splitting Method, Roe, Roe and Pike, and Harten-Lax-van-Leer-contact. Initially, the results of different reaction mechanisms were compared with experimental data. Then, some porous zones and wall roughness of porous duct as well as porous obstacles and their blockage ratio are applied to evaluate the DDT process in different working conditions. The results revealed that the addition of a porous zone could decrease the flame tip velocity and increase the maximum temperature of the process by up to 20.74%. Furthermore, the ratio of the wall roughness height to the channel width of 0.03 was found to be the optimal value to control the time and length of deflagration-to-detonation transition. Also, changes in the interval between the porous obstacles and their blockage ratio led to significant variations in the detonation flow structure. Finally, using a porous zone and porous obstacles have proved to be an advanced method to control the deflagration-to-detonation transition process.

Influence of Varying Temperature and Concentration on Magnetohydrodynamics Peristaltic Transport for Jeffrey Fluid with a Nanoparticles Phenomenon through a Rectangular Porous Duct

A mathematical model constructed to study the combined effects of the concentration and the thermodiffusion on the nanoparticles of a Jeffrey fluid with a magnetic field effect the process of containing waves in a three-dimensional rectangular porous medium canal. Using the HPM to solve the nonlinear and coupled partial differential equations. Numerical results were obtained for temperature distribution, nanoparticles concentration, velocity, pressure rise, pressure gradient, friction force and stream function. Through the graphs, it was found that the velocity of fluid rises with the increase of a mean rate of volume flow and a magnetic parameter, while the velocity goes down with the increasing a Darcy number and lateral walls. Also, the velocity behaves strangely under the influence of the Brownian motion parameter and local nanoparticle Grashof number effect.

Flow through Renal Tubules: An Application through Porous Walled Ducts

Flow through Renal Tubules: An Application through Porous Walled Ducts

Darcy-Brinkman flow of a viscous fluid through a porous duct: Application in blood filtration process

This article explores the problem arising in the filtration process of blood through a membrane of hemodialyzer. The blood is assumed to behave like a viscous Newtonian fluid moving through a 2D channel with permeable boundaries containing a Darcian porous medium. The well known Brinkman model is adopted in the balance of momentum transfer during the blood filtration process. Construction of exact solutions is furnished due to the vanishing of Reynolds number in slow flow situation. The distributions of velocities, pressure, flow rate and the leakage flux are derived and analyzed. The applicability of the theoretical results during the filtration process of blood in flat plate dialyzer is also investigated categorically. The computed values of the filtration coefficient and the dialyzer mean pressure drop from the present model are found to be in excellent agreement with the existing experimental values during the filtration process. Therefore, it is hoped that the present model provides promising measurements during blood purification processes in artificial kidneys.

Experimental Analysis of Acoustic Performance of Porous Ducts using a Small- scale Shock tube

A Shock tube is a device often used to recreate the shock phenomena by several methods. The present work is a preliminary study to analyse the efficiency of baffles in suppressing the noise generated from the shock associated jet ejected from the duct exit. The experiment was performed at a shock Mach number of 1.27 using a diaphragm based, small scale, open ended shock tube. Parametric study conducted by varying the baffle dimensions such as outer diameter, hole diameter and porosity reveals that the baffles with hole diameter less than half of the baffle diameter and with a greater porosity is a cost effective and efficient noise suppressor for shock associated jets.

Effect of Inner and Outer Horizontal wall Heating on Porous Duct

Heat Transfer analysis in a square porous annulus is conducted with respect to heating of 4 inner walls along with outer horizontal walls and cooling of outer vertical walls cooling. Darcy law along with Boussinesq approximation is applicable. Two phases of porous medium such as solid and fluid phase are in thermal equilibrium. The governing equations are approximated using Galerkin method and converted into algebraic equation using finite element method. The fluid is found to flow in vertical cells along left and right half of duct. The top section of duct is found to have minimum thermal energy as compared to other parts of duct.

Characteristics of turbulent square duct flows over porous media

Particle image velocimetry measurements have been carried out to assess the fully developed turbulence in square-sectioned porous duct flows. To the bottom duct wall, this study applies two types of porous media whose porosities are approximately 0.8 and ratios of wall-normal to streamwise permeabilities are 0.8 and 7.8. Both over- and under-surface turbulence of the porous layers are discussed at inlet flow Reynolds numbers of and 7500. Cross-sectional secondary flows are detected with an enhanced magnitude of approximately 6 % of the inlet bulk velocity. The secondary flow pattern consisting of four large vortices is observed to be insensitive to the porous structures. Over the porous wall, although turbulence is enhanced by the permeability, it is confirmed that turbulence over and under the porous surfaces is rather insensitive to the wall-normal permeability compared with the streamwise permeability as seen in porous-wall channel flows. In the present range of streamwise permeability Reynolds numbers of , the wall-normal fluctuations become dominant once underneath the porous surface while the streamwise ones become dominant again deep inside the porous layer. Applying streamwise–spanwise plane averaging, which covers a 52 % area in the middle of the duct, to the flow quantities, it is confirmed that the correlations between the pore-scale Reynolds number and the log-law parameters are similar to those seen in a wide range of porous-wall channels. The above characteristics are generally the same as those of porous-wall channels in the same range of porosities and permeability Reynolds numbers even with the enhanced secondary flows. However, from the spectral analysis of flows at the porous walls, it is found that, near the symmetry planes, the wavelengths of the Kelvin–Helmholtz waves become a little shorter than those in turbulent porous-wall channels possibly because of the sidewall boundary layers, particularly at low Reynolds numbers.

Viscous flow due to non-uniform cylinder with non-uniform stretching (shrinking) and porous velocities

A theoretical investigation is accomplished by considering a viscous flow over a porous and stretching (shrinking) cylinder of non-uniform radius. The stretching (shrinking) and injection (suction) velocities are dependent upon the axial coordinate (z). Moreover, the circular porous duct has a non-uniform shape whose surface geometry is such that . The current model is the generalization of all such models, which describe the fluid flow over a stretching (shrinking), porous (uniform/variable, both injection and suction can take place) and non-uniform (uniform) cylinder. More precisely, the classical simulations can be retrieved easily from the modeled problem. If we adjust and manipulate the parameters of the modeled problem accordingly, then we may convert the current model into all previous cases of flow problems on the above title. By means of generalized and unusual similarity transformations for the velocity components and similarity variables, the governing equations along with boundary conditions are converted into a set of differential equations (DEs). The last DEs have variable coefficients of arbitrary and multiple degrees and their significant contribution is replicated in the solutions of the modeled equations. The final problem involves a set of parameters and their properties are directly associated with the different physical mechanisms taken into account. The closed form solutions (exponential and rational functions) of the problem are found for fixed and special values of the parameters. On the other hand, curvature effects are examined on flow properties. The modeled equations are solved numerically and new results are found.

Numerical investigation of a low speed reacting flow behavior in a porous duct

In this study, the thermal performance of an unsteady, one-dimensional model, and irreversible of a CH4-air reacting process is investigated. Due to the fundamental differences between the free flame and porous structures such as flame thickness and the length of the preheated zone, it is necessary to employ a chemical kinetic which in accordance with the structure of a porous duct made of cellular ceramic, even if it is very simple. To achieve this aim, CH4 oxidation with the five-step reaction mechanism is considered to simulate the combustion phenomenon in the porous burner. In order to solve the governing equations, a finite volume method is used to discretize the governing conservation equations of the problem. Transient, displacement and diffusion terms were respectively solved using completely implicit schemes, Upwind, and discretized central difference and the resulting algebraic equations by the TDMA repeated procedure. In this research, the segregated method was used to solve the set of equations, in which the suitable convergence condition for the governing variables of the problem was used. After validation of the obtained results with available experimental data, the effects of the solid matrix porosity density, porosity, length, extinction coefficient as well as the effects of fire rate, equilibrium ratio, and inlet temperature are investigated. The results show any changes in solid matrix properties and inlet conditions lead to significant changes in combustion structure.

Numerical mesoscopic method for transportation of H2O-based nanofluid through a porous channel considering Lorentz forces

Recently, various ways are investigated to augment heat transfer in different applications such as porous ceramic domain. Adding nanoparticles to fluid is the best operational way to increase the conduction of fluids. In this paper, migration of nanofluid inside a porous duct under the impact of magnetic force is scrutinized. LBM is applied to present comprehensive parametric analysis for various concentrations of nanofluid, Hartmann, Reynolds, and Darcy numbers. Outputs illustrate that Nu augments with improve of Lorentz forces. Augmenting Da significantly enhances the convective flow in our model.