Porosity Of Medium Research Articles

Barometric pressure variation alters electrical resistivity during water infiltration in the vadose zone

To reveal the mechanism of the water–gas two-phase repulsion during water infiltration and its barometric pressure change and resistivity response in the vadose zone while it provides the basic theory for water resources evaluation and groundwater pollution, also provides technical support for the accurate interpretation of electrical resistivity tomography (ERT) application. Therefore, a research system based on laboratory experiments, numerical simulations, and ERT was established to determine the moisture transport pattern and the quantitative relationships between barometric pressure and resistivity. The results show that the intensity of the water infiltration process in the vadose zone meets the percolation theory. The barometric pressure will go through three stages when the infiltration intensity is higher than the critical value. The critical time of the barometric pressure variation shortens gradually with the infiltration intensity and medium permeability increase. In contrast, the maximum barometric pressure increases gradually with the rise in infiltration intensity and medium porosity. The layered-heterogeneous structure's effect depends on the underlying medium's properties. The trivial variation of resistivity responds to the barometric pressure variation. The quantitative relationship between the resistivity and the barometric pressure in the vadose zone is established by the difference between the measured value and the calculated value by improving Archie's formula. The resistivity reduction due to increasing barometric pressure can account for over 10.9% of the moisture effect. These insights provide technical support for ERT applications to eliminate barometric pressure's effect on resistivity and accurately identify the target medium.

Thermal instability of rotating Jeffrey nanofluids in porous media with variable gravity

It is investigated how changes in gravity affect the thermal instability rotating Jeffrey nanofluids in porous media. Along with the Galerkin method and normal mode approach, the Darcy model is used. The distinct variable gravity parameters taken in this paper are: h(z)=z2-2z, h(z)=-z2, h(z)=-z and h(z)=z and their effects on the Jeffrey parameter, Taylor number, moderated diffusivity ratio, porosity of porous media, Lewis number and nanoparticle Rayleigh number on stationary convection have been scrutinized and graphically shown. Our finding demonstrates that varying gravity parameter h(z)=z2-2z has more stabilising impact on stationary convection. We have also discovered the necessary condition for overstability in the instance of oscillatory convection for this problem.

Heat transfer through a higher grade Forchheimer porous CuO–H2O-nano-medium confined between non-isothermal moving plates

In this study, the aim is to analyze numerically heat transfer through a higher grade Forchheimer porous CuO–H2O-nano-medium in an unsteady magneto-hydrodynamic (MHD) porous flow. The nano-medium is confined between two non-isothermal moving infinite parallel plates. The flow governing equations are developed through variational calculus approach and are resulted in partial differential equations. The temperature of both the plates are taken to be variable. The governing flow PDEs along with the prescribed boundary conditions are solved using finite difference approach for time discretization and finite element approach for discretizing the spatial coordinate. The algorithm used is described here in detail for the numerical simulations and calculations of results. The proposed algorithm is implemented through MATLAB and simulations are performed for parameters of interest which includes: Nusselt number, skin friction coefficients, Forchheimer constant, volume fraction, Prandtl number, Grashhoff number, Hartmann number, and convection and porosity parameters. Effective implementation of the proposed algorithm is demonstrated through plots of time profiles of non-dimensionalized thermodynamic velocity and temperature against these parameters. It is observed that the larger the porosity of the nanomedium leads to the larger skin friction at both the plates. The plate's temperature gets increased with the increase in the Forchhiemer number. However, the hydrodynamic velocities get smaller as the porosity gets elevated. Forchheimer constant and skin friction coefficients are related with direct proportionality. Whereas the skin friction coefficient is observed behaving monotone in relation to the Hartman constant. The Nusselt number at both the plates get increase in its value as the nanoparticles concentration increases. By increasing the velocity ratio between the two moving plates shows opposite trend. However, the Nusselt number decreases if the porosity of the nano-fluidic medium is increased. It is pertinent to mention that the present modeling approach can be used to analyze the Forchheimer medium flows involving catalytic converters and gas turbine dynamics.

Heat transfer in a conical gap using H2O–Cu nanofluid and porous media. Effects of the main physical parameters

Heat transfer around a conical antenna is quantified in this work. Cooling of this active electronic component is ensured by a medium of high porosity saturated by a H2O–Cu nanofluid with a volume fraction varying between 0% and 5%. The ratio between the thermal conductivity of the porous materials and that of the water (base fluid) ranges from 4 to 41.2, the null value corresponding to a heat transfer without porous media (only nanofluid). The conical enclosure's aspect ratio varies in the 0.2–0.6 range, being its base inclined between 0° (horizontal base with cone's top oriented upwards) and 180° range (horizontal base with cone's top oriented downwards). The associated Rayleigh number varies within the 3.32x105-6.74x107 range. Heat transfer by natural convection is quantified for any configuration combining these five parameters and presented via a correlation allowing determination of the average Nusselt number. This study shows that heat transfer increases when the cone is tilted. For a given aspect ratio, the maximum is reached when the cone is vertical with the top pointing down. This observation remains valid in the overall Rayleigh number range. The average Nusselt number enhancement varies between 20 and 70%, according on the considered cavity's aspect ratio. This study complements a recent one restricted to the case of a cone whose horizontal base is located at the bottom, being 0.2 the aspect ratio of the enclosure.

Thermal stratification effect on gravity driven transport of hybrid CNTs down a stretched surface through porous medium

The purpose of the current article is to explore the impact of thermal stratification and medium porosity on gravity-coerced transport of hybrid carbon nanotubes down an upright extending sheet inspired by a constant applied magnetic field along with heat transfer investigation in existence of thermal radiation, viscous dispersal, and joule heating effect. Rectangular coordinates are chosen for the mathematical interpretation of the governing flow problem. Homothetic analysis is employed for the sake of simplification process. The reduced system of coupled nonlinear differential equations is dealt numerically by dint of computational software MATLAB inbuilt routine function Bvp4c. The numerical investigation is carried out for the distinct scenarios namely, (i) Presence of favorable buoyancy force, (ii) Case of purely forced convection and (iii) Presence of opposing buoyancy force. Significant Findings: The key findings include that the presence of hybrid carbon nanotubes and medium porosity contributes significantly to upsurging surface shear stress magnitude whereas, external magnetic field and velocity slip effects in an altered manner. The present study may be a benchmark in study of fueling process in space vehicles and space technology.

Development characteristics and controlling factors of dolomite reservoirs of permian Qixi a Formation in central Sichuan Basin

In recent years, with the fine exploration of carbonate reservoirs in the Qixia Formation, central Sichuan Basin, researchers have made important oil and gas discoveries in the dolomite reservoirs. However, the characteristics, genesis and controlling factors of dolomite reservoirs in the Qixia Formation in this area are still unclear. In this paper, the petrology, pore structures, physical properties and geochemical characteristics of the dolomite reservoirs in the Permian Qixia Formation in the central Sichuan Basin have been systematically studied based on a large number of cores, thin sections, physical property and geochemical tests. Furthermore, the genesis and main controlling factors of dolomite reservoirs are clarified. The study shows that the dolomites have the characteristics of small single-layer thickness and multi-layer development, and they are usually interbeded with the limestones. The reservoir types are mainly fine crystal and fine medium crystal dolomite, and the reservoir spaces include intercrystalline pores and dissolution pores (or caves). Moreover, the reservoir physical properties are characterized by medium porosity and medium to high permeability. Quasi-syngenetic dolomitization is the main origin of dolomite in the target layer, and the dolomite was slightly modified by hydrothermal solution at the end of the Maokou Formation period. The development of dolomite reservoirs in the Qixia Formation in the study area is affected by palaeogeomorphology, sedimentation and diagenesis. The granular shoal facies developed in the high parts of the paleogeomorphology provides the material basis for the formation of dolomite reservoirs. The high frequency sequence interface controls the development of dolomite reservoirs in the highstand systems tract. In addition, the quasi-syngenetic dissolution promots the development of the early secondary pores and provids an effective channel for the migration of the diagenetic fluids in the later stage. In the direction of orthogonal horizontal deposition, the dolomites have the characteristics of thin monolayer thickness, multiple sequences and are interbedded with limestone. The dolomite shoals in the study area are distributed as clumps in the plane, which has great potential for hydrocarbon exploration.

Free Electrothermo-Convective Instability in a Dielectric Oldroydian Nanofluid Layer in a Porous Medium

For the last few years, thermal instability of non-Newtonian nanofluids becomes a prominent field of research because it has various applications in automotive industries, energy-saving, nuclear reactors, transportation, electronics etc. and suspensions of nanoparticles are being developed in medical applications including cancer therapy. In this paper, a free electrothermo-convective instability in a dielectric nanofluid layer in a porous medium is studied. An Oldroyd’s constitutive equation is used to describe the behaviour of nanofluid and for porous medium, the Darcy model is employed. The equation of conservation of momentum of fluid is stimulated due to the presence of an AC electric field, stress-relaxation parameter and strain-retardation parameter. The stability of the system is discussed in stationary and oscillatory convections for free–free boundaries. For the case stationary convection, it is found that the Oldroydian Nanofluid behaves like an ordinary nanofluid as the stationary Rayleigh number is independent of the stress-relaxation parameter, the strain-retardation parameter and Vadasz number. The effect of stress-relaxation-time parameter, strain-retardation-time parameter, Vadasz number, nanoparticles Rayleigh number, modified diffusivity ratio, medium porosity, Lewis number and electric Rayleigh number examined numerically and graphs have been plotted to analyse the stability of the system. It is observed that the electrical Rayleigh number has destabilizing influence whereas nanoparticles Rayleigh number, porosity and modified diffusivity ratio have stabilizing effect on the system. The oscillatory convection is possible for the values of the stress-relaxation parameter less than the strain-retardation parameter for both top-heavy/bottom-heavy distributions of nanoparticles.

Influence mechanism of brine-gas two-phase flow on sealing property of anisotropic caprock for hydrogen and carbon energy underground storage

As the simplest saturated hydrocarbon, methane is an important hydrogen and carbon energy. The stability and sealing of caprock are keys to ensure the safe storage of energy in the process of hydrogen and carbon energy underground storage. A fully coupled two-phase flow model is established to analyze the migration mechanism of methane in caprock. This model considers the characteristics of dual porosity medium composed of caprock fractures and matrix, including the seepage of methane and brine. In the model, the replacement process of methane and brine exists in the fracture network, and the dynamic adsorption desorption process of methane exists in the matrix. Under the action of tectonic stress, obvious differences are observed in the fracture and permeability in different directions. All these characteristics are considered in the fully coupled two-phase flow model. The restraining and strengthening effects of caprock in the process of methane leakage are analyzed. The results show that the gas induces the adsorption expansion of the caprock matrix and reduces the fracture opening and permeability of the caprock. With the gradual invasion of gas into the caprock, the sealing characteristics of caprock show the evolution of self-inhibition first and then self-enhancement. With the increase in dip angle, gas tends to invade vertically rather than horizontally. Realizing gas–brine replacement is easier with the existence of large fractures. This study provides an effective numerical analysis method, which can be used to evaluate the sealing efficiency in the caprock in underground methane storage.

The Rayleigh mode at the plane boundary between a liquid and a double porosity medium.

The Rayleigh mode (also called generalized Rayleigh wave) at the flat interface between a liquid and a double porosity medium saturated by the same liquid, is investigated. The double porosity medium obeys the phenomenological model of Berryman and Wang (2000). It allows the simultaneous propagation of three longitudinal waves and a transverse wave. Assuming open pore conditions at the interface, formulas are found for the coefficients of reflection in the liquid and of transmission in the double porosity medium. Considering only the angular variable in the study, numerical simulations based on data for Berea sandstone show the influence of frequency and the two types of porosity on the reflection coefficient and on the velocity of the generalized Rayleigh wave.

An exclusion distance controls the efflorescence pattern distribution on porous media during salt solution evaporation

Understanding salt crystallization due to evaporation of a salt solution from a porous medium is critical in applications ranging from saltwater distillation to preservation of historical monuments. Efflorescence is the crystallization of salt on the exposed surface of the porous medium. In this work, efflorescence patterns are visually observed and characterized on sintered copper particle wicks with spatially unimodal and bimodal compositions of different particle sizes. Efflorescence is found to form earlier and spread readily over a wick made from smaller particles, owing to their lower porosity, while it is limited to certain areas of the surface for wicks composed of the larger particles. A scaling analysis explains the observed efflorescence patterns in the bimodal wicks caused by particle size-induced nonuniform porosity and permeability. The non-uniformity reduces the advective flux in a high-permeability region by diverting flow towards a low-permeability region resulting from different pressure drops along the regions. This reduction in advective flux manifests as an exclusion distance surrounding a crystallization site where efflorescence is not expected to occur. The dependence of this exclusion distance on the porosity and permeability of the porous medium and the operating conditions is investigated. A large exclusion distance associated with the regions with bigger particles in the bimodal wicks explains preferential efflorescence over the regions with smaller particles. Our novel scaling analysis coupled with the introduction of the exclusion distance provides guidelines for designing heterogeneous porous media that can localize efflorescence.

Elastic response of porous rock to accumulated slip on strike slip fault networks in geo-reservoirs

Subsurface reservoirs are generally highly fractured, whereby fractures constitute a natural fluid flow path and define the preferential flow direction. Slip accumulated during the faulting process alters also the petrophysical properties of the host rock. Although the mechanical alteration of the host rock, and related porosity and permeability changes, due to fault slip has been previously described, a predictive physics-based model has not been scaled with fault length in reservoirs to provide an initial porosity permeability alteration model yet. In this study, we develop a predictive model to quantify how accumulated fault slip changes porosity and permeability in a porous medium, by combining deformation modeling based on triangular dislocations and linearized poro-elasticity equations. We applied our model the Ghawar field fault map and rock-types. We conducted a Monte-Carlo simulation, varying fault roughness and accumulated slip, to quantify the corresponding variation in porosity and permeability using a 5 km long strike-slip fault and three different rock-types. Our Monte-Carlo simulation shows that long-term accumulated slip on rough strike-slip fault surfaces change porosity by ±1%, leading to an absolute permeability change of up to 22.5%. We further used these results as a benchmark for the elastic response of porous rocks to accumulated slip scaled to certain fault length. Using these benchmark results for Ghawar field reservoir rocks, we determined the slip-related porous medium permeability changes for every fault on the Ghawar fault map, accounting for their length, location, and orientation. In doing so, we found that fault roughness, slip amount, and shear sense all affect the medium’s permeability, creating substantial permeability anisotropies. Locally, these anisotropies are further enhanced by superposition of permeability changes of individual faults that constitute the fault system. We suggest the resulting permeability distribution model should be used as the initial permeability model for porous media in fractured reservoirs.

Experimental study on burning characteristic of liquid fuel immersed in porous media bed: Effect of particle gradation

A series of burning test was conducted to investigate the effect mechanism of particle gradation on burning characteristic of liquid fuel immersed in porous media. High-purity quartz equipped with two-component discontinuous gradation and ethanol liquid were employed as porous bed and liquid fuel. The characteristic parameters, e.g., burning rate, temperature distribution, flame feature and burning duration, etc., were recorded and identified. Results show that the burning characteristic of liquid fuel immersed in porous media with gradation configuration is conjunctively influenced by capillary effect and thermal conductivity of porous media. For the porous media bed with fine particles, capillary effect plays a dominant role in the variation trend of burning rate. While for the porous media bed with good gradation, under the effect of better contact condition and more coordination numbers, thermal conduction enhanced by particle gradation dominates the burning characteristic. Meanwhile, the burning rate of porous bed immersed by liquid fuel demonstrates stage-variation feature: a rapid growth stage dominated by direct flame thermal feedback and an attenuation-stable stage dominated by thermal conduction. Due to the “back effect”, the burning rate has a quasi-stable phase in middle-and-late stage, which is positively correlated with the one-half power of media porosity. Moreover, due to the enhancement of thermal conductivity, the downward heat transfer rate of porous media with good gradation is relatively faster. In addition, there is still a positive tendency between flame height and burning rate. This work is expected to provide some references for understanding the burning characteristics of liquid fuel immersed in porous media and burning-decontamination operation.

Influence of compost amendment rate and level of compaction on the hydraulic functioning of soils

AbstractThere has been widespread interest in using compost to improve the hydrologic functions of degraded soils at construction sites for reducing runoff and increasing infiltration. The objective of this study was to determine the effects of compost amendment rate on saturated hydraulic conductivity (Ks) and water retention in order to identify target compost rates for enhancing soil hydrologic functions. Samples were prepared with three soil textures (sandy loam, silt loam, and sandy clay loam), amended with compost at 0%, 10%, 20%, 30%, 40%, and 50%. All soils were tested at a porosity of 0.5 m3/m3, and the sandy loam was further tested at high (0.55 m3/m3) and low (0.4 m3/m3) porosities. The Ks and water retention data were then used to model infiltration with HYDRUS‐1D. With increasing compost amendment rate, Ks and water retention of the mixtures generally increased at the medium porosity level, with more compost needed in heavier soils. As porosity decreased in the sandy loam soil, the amount of compost needed to improve Ks rose from 20% to 50%. Water distribution in pore fractions (gravitational, plant‐available, and unavailable water) depended on texture, with only the highest compost rates increasing plant‐available water in one soil. Results suggest soil texture should be taken into consideration when choosing a compost rate in order to achieve soil improvement goals. Hydrologic benefits may be limited even at a high rate of compost amendment if soil is compacted.

A new numerical well test method of multi-scale discrete fractured tight sandstone gas reservoirs and its application in the Kelasu Gas Field of the Tarim Basin

The cretaceous gas reservoir in Kelasu Gas Field of the Tarim Basin is a rare ultra-deep and ultra-high pressure fractured tight sandstone gas reservoir where multi-scale discrete fractures of matrix, fracture and fault are developed, so its development cannot be conducted just based on static and dynamic reservoir description. In order to solve this problem, this paper establishes a numerical well test model of vertical wells based on matrix, fractures and faults (large fractures and small faults) by combining the random generation of natural fracture networks with the unstructured discrete fracture modeling method to break through the traditional continuous medium well test model. In addition, the model is solved by using the finite element method with mixed element, and the typical well test type curves under different random fracture networks are obtained. And the following research results are obtained. First, based on the observed data, the fracture network distribution modes of fractured tight sandstone gas reservoirs are classified into three categories. The influence of random generation of fracture networks on typical well test type curves is discussed. The results of discrete fracture well test model are compared with those of the traditional continuous medium well test model, and the applicable conditions of the traditional continuous medium well test model is determined. Second, there are great differences between the results of discrete fracture model and those of dual porosity medium model. 1 The dual porosity medium model is a special case of the discrete fracture model, in which the fractures are evenly distributed within infinitely small spacing. Third, the characteristics of well test type curves under three fracture network distribution modes are discussed. The well test type curves that cannot be interpreted by the conventional dual/triple porosity continuous medium model are successfully interpreted by using the established well test interpretation model of random discrete fracture. The curve matching effect is ideal and the interpreted parameters are reasonable. In conclusion, the new model and the new method reveal the development mechanism of step-by-step production and coordinated gas supply between media of different scales, explain the development characteristics of large inter-well productivity difference and abnormal rapid inter-well pressure response, and provide a reference for the development of similar gas reservoirs.

Electrohydro dynamics convection in dielectric rotating Oldroydian nanofluid in porous medium

An electrically conducting nanofluid saturated with a uniform porous media has been tested to determine how rotation affects thermal convection. Utilizing the Oldroydian model, which incorporates the specific effects of the electric field, Brownian motion, thermophoresis, and rheological factors for the distribution of nanoparticles that are top- and bottom-heavy, one may use linear stability theory to ensure stability. Analysis and graphical representation of the effects of the AC electric field Rayleigh number, Taylor number, Lewis number, modified diffusivity ratio, concentration Rayleigh number, and medium porosity are provided for both bottom-heavy and top-heavy distribution.

Effect of skull porosity on ultrasound transmission and wave mode conversion at large incidence angles.

Transcranial ultrasound imaging and therapy depend on the efficient transmission of acoustic energy through the skull. Multiple previous studies have concluded that a large incidence angle should be avoided during transcranial-focused ultrasound therapy to ensure transmission through the skull. Alternatively, some other studies have shown that longitudinal-to-shear wave mode conversion might improve transmission through the skull when the incidence angle is increased above the critical angle (i.e., 25° to 30°). The effect of skull porosity on the transmission of ultrasound through the skull at varying incidence angles was investigated for the first time to elucidate why transmission through the skull at large angles of incidence is decreased in some cases but improved in other cases. Transcranial ultrasound transmission at varying incidence angles (0°-50°) was investigated in phantoms and ex vivo skull samples with varying bone porosity (0% to 28.54%±3.36%) using both numerical and experimental methods. First, the elastic acoustic wave transmission through the skull was simulated using micro-computed tomography data of ex vivo skull samples. The trans-skull pressure was compared between skull segments having three levels of porosity, that is, low porosity (2.65%±0.03%), medium porosity (13.41%±0.12%), and high porosity (26.9%). Next, transmission through two 3D-printed resin skull phantoms (compact vs. porous phantoms) was experimentally measured to test the effect of porous microstructure alone on ultrasound transmission through flat plates. Finally, the effect of skull porosity on ultrasound transmission was investigated experimentally by comparing transmission through two ex vivo human skull segments having similar thicknesses but different porosities (13.78%±2.05% vs. 28.54%±3.36%). Numerical simulations indicated that an increase in transmission pressure occurs at large incidence angles for skull segments having low porosities but not for those with high porosity. In experimental studies, a similar phenomenon was observed. Specifically, for the low porosity skull sample (13.78%±2.05%), the normalized pressure was 0.25 when the incidence angle increased to 35°. However, for the high porosity sample (28.54%±3.36%), the pressure was no more than 0.1 at large incidence angles. These results indicate that the skull porosity has an evident effect on the transmission of ultrasound at large incidence angles. The wave mode conversion at large, oblique incidence angles could enhance the transmission of ultrasound through parts of the skull having lower porosity in the trabecular layer. However, for transcranial ultrasound therapy in the presence of highly porous trabecular bone, transmission at a normal incidence angle is preferable relative to oblique incidence angles due to the higher transmission efficiency.

Performance of Heat Transfer in Micropolar Fluid with Isothermal and Isoflux Boundary Conditions Using Supervised Neural Networks

The current study delivers a numerical investigation on the performance of heat transfer and flow of micropolar fluid in porous Darcy structures with isothermal and isoflux walls (boundary conditions) of a stretching sheet. The dynamics and mechanism of such fluid flows are modelled by nonlinear partial differential equations that are reduced to a system of nonlinear ordinary differential equations by utilizing the porosity of medium and similarity functions. Generally, the explicit or analytical solutions for such nonlinear problems are hard to calculate. Therefore, we have designed a computer or artificial intelligence-based numerical technique. The reliability of neural networks using the machine learning (ML) approach is used with a local optimization technique to investigate the behaviours of different material parameters such as the Prandtl number, micropolar parameters, Reynolds number, heat index parameter, injection/suction parameter on the temperature profile, fluid speed, and spin/rotational behaviour of the microstructures. The approximate solutions determined by the efficient machine learning approach are compared with the classical Runge–Kutta fourth-order method and generalized finite difference approximation on a quasi-uniform mesh. The accuracy of the errors lies around 10−8 to 10−10 between the traditional analytical solutions and machine learning strategy. ML-based techniques solve different problems without discretization or computational work, and are not subject to the continuity or differentiability of the governing model. Moreover, the results are illustrated briefly to help implement microfluids in drug administering, elegans immobilization, and pH controlling processes.

Numerical analysis of local thermal non-equilibrium free convection in a porous enclosure with a wavy cold side wall

In this piece of communication, numerical heat transfer and fluid flow in a Darcy porous enclosure are investigated. The right wavy wall is maintained at a constant low temperature, with the top and bottom preserved thermally insulated, while the left vertical wall is uniformly heated. The governing equations for non-dimensional systems are solved using the Galerkin finite element method; a local thermal non-equilibrium appears between the base fluid and porous matrix. The effects of interface heat transfer parameter [Formula: see text] along with porosity of porous media [Formula: see text], Rayleigh-Darcy number [Formula: see text], and parameters involving waviness of cavities, such as the number of undulations in a unit length [Formula: see text] and amplitude of the wave [Formula: see text] are investigated. The results show that increment waviness augments heat transfer enhancement for fluid and solid phases. The local thermal equilibrium cases for various parameters are pointed out at a 5% significance level of the average temperature difference between the two phases.

Polymeric Microfluidic Fuel Cells with Controlled Printed Patterns.

Since its first appearance almost a couple of decades ago, microfluidic fuel cells (MFFCs) have gained considerable research momentum due to their potential applications in portable devices. The main focus has been on the effective fabrication of microfluidic channels with different materials, where the manufacturing limitations proved to be the main stumbling blocks. Paper-based MFFCs have been reported with some success, where the porosity of the flow channel medium drives the reactants, greatly reducing the need for elaborate external devices and complex manufacturing obstacles, although the longevity of these cells remains questionable. The current article addresses this issue by replacing the paper-based flow channels with 3D-printed substrates of different structural forms to serve as pathways for controlled flow and mixing responses of the reactant liquids without the use of other devices, such as micro pumps and valves. The line-by-line material consolidation mechanics of fused filament fabrication and the porous mesostructural responses of a commercial polymer filament are combined to build the microfluidic fuel channels of varying configurations. Numerical and experimental characterizations proved the cells to perform better than the current paper-based counterparts, apart from better longevity and possible new opportunities for future improvements based on more complex micro-, meso-, and macrostructural advances.

Multi-objective hydrothermal optimization of nanoparticles shape in nanofluid flow through an annular pipe having metal foam fins

The objective of this contribution is twofold. First, a multi-objective hydrothermal optimization is performed to determine the optimum nanoparticles (NPs) shape in nanofluid flow through an annular pipe having metal foam fins, in the forced convection regime. Second, the suitability of the performance evaluation criterion (PEC), as a common method to analyze the hydrothermal performance of thermal systems, is examined by comparing the outcomes of the multi-objective optimization method with those obtained by maximizing PEC. It is found that, depending on the value of the Reynolds number, the cylindrical-shaped NPs or the blade-shaped NPs exhibit the highest heat transfer performance. The lowest value of the required pumping power belongs to the spherical-shaped NPs. The results indicate that PEC attains its maximum value in the spherical-shaped NPs, the NPs fraction of 0.01, the nondimensional fin length of 0.4, the Darcy number of 0.01, and the medium porosity of 0.75. However, the multi-objective algorithm provides several optimum circumstances, each for a certain criterion indicating the suitability of this strategy for hydrothermal performance optimization of the system.