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This paper aims to discuss the dynamic adsorption processes of carbon dioxide in a porous fixed bed on the industrial scale, using a multiple-relaxation-time lattice Boltzmann (LB) model.

A multiple-relaxation-time LB model is developed to predict the dynamic adsorption processes of carbon dioxide in a porous fixed bed on the industrial scale. The breakthrough curves from the simulation results are compared with the experimental data to validate the reliability of this model, and the effects of flow velocity, porosity and linear driving force mass transfer coefficient on the adsorption behaviors of carbon dioxide are explored further.

The numerical results show that the improved fluid flux leads to the reduction in the time required for completion of adsorption processes nonlinearly, and the differential pressure significantly raises with the decreasing porosity of porous fixed bed for fixed values of Reynolds number and total adsorption capacity. The maximum adsorption ratio of carbon dioxide was found at Re = 12 in this work. In addition, the higher mass transfer resistance of adsorbent particles advances the appearance time of the breakthrough point and delays the completion time of the adsorption processes.

This work will provide a way to study the adsorption technology of carbon dioxide in the fixed-bed using the LB method.

The purpose of this paper is to investigate the allometric permeation performance in fractal branching channel net driven by capillary pressure and analyze how the geometrical parameters of the branching channel net affect the permeability of the fluid transportation.

An allometric permeation model is proposed based on the fractal theory by considering capillary pressure as the main driven force of fluid permeation.

It is found that the permeability efficiency is a function of fractal dimension, bifurcation number, and number of branching level. Different fluid permeation efficiencies of the channel net can be obtained by changing the three parameters.

The allometric permeation model established provides a better understanding of the permeation mechanism in fractal porous media which could further help with the design of bio-mimetic artificial materials.

This research study aims to develop regular cylindrical pore network models (RCPNMs) to calculate topology and geometry properties of explosively created fractures along with their resulting hydraulic permeability. The focus of the investigation is to define a method that generates a valid geometric and topologic representation from a computational modelling point of view for explosion-generated fractures in rocks. In particular, extraction of geometries from experimentally validated Eulerian smoothed particle hydrodynamics (ESPH) approach, to avoid restrictions for image-based computational methods.

Three-dimensional stabilized ESPH solution is required to model explosively created fracture networks, and the accuracy of developed ESPH is qualitatively and quantitatively examined against experimental observations for both peak detonation pressures and crack density estimations. SPH simulation domain is segmented to void and solid spaces using a graphical user interface, and the void space of blasted rocks is represented by a regular lattice of spherical pores connected by cylindrical throats. Results produced by the RCPNMs are compared to three pore network extraction algorithms. Thereby, once the accuracy of RCPNMs is confirmed, the absolute permeability of fracture networks is calculated.

The results obtained with RCPNMs method were compared with three pore network extraction algorithms and computational fluid dynamics method, achieving a more computational efficiency regarding to CPU cost and a better geometry and topology relationship identification, in all the cases studied. Furthermore, a reliable topology data that does not have image-based pore network limitations, and the effect of topological disorder on the computed absolute permeability is minor. However, further research is necessary to improve the interpretation of real pore systems for explosively created fracture networks.

Although only laboratory cylindrical rock specimens were tested in the computational examples, the developed approaches are applicable for field scale and complex pore network grids with arbitrary shapes.

It is often desirable to develop an integrated computational method for hydraulic conductivity of explosively created fracture networks which segmentation of fracture networks is not restricted to X-ray images, particularly when topologic and geometric modellings are the crucial parts. This research study provides insight to the reliable computational methods and pore network extraction algorithm selection processes, as well as defining a practical framework for generating reliable topological and geometrical data in a Eulerian SPH setting.

This paper aims to numerically investigate the impact of gas diffusion layer (GDL) anisotropic transport properties on the overall and local performance of polymer electrolyte fuel cells (PEFCs).

A three-dimensional numerical model of a polymer electrolyte fuel cell with a single straight channel has been developed to investigate the sensitivity of the fuel cell performance to the GDL anisotropic transport properties – gas permeability, diffusivity, thermal conductivity and electrical conductivity. Realistic experimentally estimated GDL transport properties were incorporated into the developed PEFC model, and a parametric study was performed to show the effect of these properties on fuel cell performance and the distribution of the key variables of current density and oxygen concentration within the cathode GDL.

The results showed that the anisotropy of the GDL must be captured to avoid overestimation/underestimation of the performance of the modelled fuel cell. The results also showed that the fuel cell performance and the distributions of current density and oxygen mass fraction within the cathode GDL are highly sensitive to the through-plane electrical conductivity of the GDL and, to a lesser extent, the through-plane diffusivity, and the thermal conductivity of the GDL. The fuel cell performance is almost insensitive to the gas permeability of the GDL.

This study improves the understanding of the importance of the GDL anisotropy in the modelling of fuel cells and provides useful insights on improving the efficiency of the fuel cells.

Realistic experimentally estimated GDL transport properties have been incorporated into the PEFC model for the first time, allowing for more accurate prediction of the PEFC performance.

As a powerful mathematical analysis tool, the local fractional calculus has attracted wide attention in the field of fractal circuits. The purpose of this paper is to derive a new ℑ-order non-differentiable (ND) R-C zero state-response circuit (ZSRC) by using the local fractional derivative on the Cantor set for the first time.

A new ℑ-order ND R-C ZSRC within the local fractional derivative on the Cantor set is derived for the first time in this work. By defining the ND lumped elements via the local fractional derivative, the ℑ-order Kirchhoff voltage laws equation is established, and the corresponding solutions in the form of the Mittag-Leffler decay defined on the Cantor sets are derived by applying the local fractional Laplace transform and inverse local fractional Laplace transform.

The characteristics of the ℑ-order R-C ZSRC on the Cantor sets are analyzed and presented through the 2-D curves. It is found that the ℑ-order R-C ZSRC becomes the classic one when ℑ = 1. The comparative results between the ℑ-order R-C ZSRC and the classic one show that the proposed method is correct and effective and is expected to shed light on the theory study of the fractal electrical systems.

To the best of the authors’ knowledge, this paper, for the first time ever, proposes the ℑ-order ND R-C ZSRC within the local fractional derivative on the Cantor sets. The results of this paper are expected to give some new enlightenment to the development of the fractal circuits.

The purpose of the study is to propose a novel implementation of twisted tape in sinusoidal wavy-walled tubes to enhance the rate of heat transfer without compromising thermal efficiency. The study numerically investigates the fluid flow characteristics and analyzes the effect of different geometrical configurations, including wall wave amplitude, tape twist angles and nanoparticle volume fractions, on heat transfer improvement and performance factor.

This problem is numerically investigated using computational fluid dynamics, and the method is the finite volume method. A two-phase mixture model is used for nanofluid modeling.

The study investigated the effect of wall waviness, twisted tape, and nanoparticles on forced convective heat transfer and friction factor behavior in laminar pipe flow in three different Reynolds number regimes. The results showed that implementing twisted tape in wavy tubes significantly increased the rate of heat transfer and the performance factor, with the best twist ratio between 90 and 180°. Adding nanoparticles also enhanced heat transfer and performance factor, but to a lesser extent than wavy wall-twisted tape combinations. The study suggests selecting a proper combination of wavy wall and twisted tape at each Reynolds number to achieve an optimum solution.

To the best of the authors’ knowledge, the implementation of the selected passive methods in sinusoidal wavy tubes has not been studied before, and no previous studies have taken into account such a mix of heat transfer improvement techniques.

The fractal and fractional calculus have obtained considerable attention in the electrical and electronic engineering since they can model many complex phenomena that the traditional integer-order calculus cannot. The purpose of this paper is to develop a new fractional pulse narrowing nonlinear transmission lines model within the local fractional calculus for the first time and derive a novel method, namely, the direct mapping method, to seek for the nondifferentiable (ND) exact solutions.

By defining some special functions via the Mittag–Leffler function on the Cantor sets, a novel approach, namely, the direct mapping method is derived via constructing a group of the nonlinear local fractional ordinary differential equations. With the aid of the direct mapping method, four groups of the ND exact solutions are obtained in just one step. The dynamic behaviors of the ND exact solutions on the Cantor sets are also described through the 3D graphical illustration.

It is found that the proposed method is simple but effective and can construct four sets of the ND exact solutions in just one step. In addition, one of the ND exact solutions becomes the exact solution of the classic pulse narrowing nonlinear transmission lines model for the special case 9 = 1, which strongly proves the correctness and effectiveness of the method. The ideas in the paper can be used to study the other fractal partial differential equations (PDEs) within the local fractional derivative (LFD) arising in electrical and electronic engineering.

The fractional pulse narrowing nonlinear transmission lines model within the LFD is proposed for the first time in this paper. The proposed method in the work can be used to study the other fractal PDEs arising in electrical and electronic engineering. The findings in this work are expected to shed a light on the study of the fractal PDEs arising in electrical and electronic engineering.

The purpose of this paper is to derive a new fractal active low-pass filter (LPF) within the local fractional derivative (LFD) calculus on the Cantor set (CS).

To the best of the author’s knowledge, a new fractal active LPF within the LFD on the CS is proposed for the first time in this work. By defining the nondifferentiable (ND) lumped elements on the fractal set, the author successfully extracted its ND transfer function by applying the local fractional Laplace transform. The properties of the ND transfer function on the CS are elaborated in detail.

The comparative results between the fractal active LPF (for γ = ln2/ln3) and the classic one (for γ = 1) on the amplitude–frequency and phase–frequency characteristics show that the proposed method is correct and effective, and is expected to shed light on the theory study of the fractal electrical systems.

To the best of the author’s knowledge, the fractal active LPF within the LFD calculus on the CS is proposed for the first time in this study. The proposed method can be used to study the other problems in the fractal electrical systems, and is expected to shed a light on the theory study of the fractal electrical systems.

The purpose of the current paper is to develop a numerical methodology, based on the immersed boundary-lattice Boltzmann computational framework, for the Neumann and Dirichlet boundary conditions in problems involving natural and forced convection heat transfer.

The direct forcing immersed boundary method is extended to study the heat transfer by incompressible flow within the thermal lattice Boltzmann method (LBM) computational framework. The direct forcing and heating immersed boundary-LBM introduces a heat source term to the thermal LBM to account for the heat transfer occurring at the immersed boundary. New numerical treatments for the Neumann type of boundary condition and for the calculation of the local Nusselt number are developed. The developed methodologies have been applied to flows around immersed bodies with natural and forced convection, including steady as well as unsteady flows.

Numerical experiments involving immersed bodies in natural and forced convection have been performed in order to assess the validity of the direct heating IB-LBM. The flow cases studied also include steady and transient flow phenomena. Flow velocity field and isotherms have been used for qualitative comparisons with existing, published results. The surface averaged Nusselt number, Strouhal number, and lift coefficient (for the unsteady flow cases) have been used for quantitative comparison with published results. The results show that there are satisfactory agreements, qualitatively and quantitatively, between the results obtained by using the present method and those previously published.

Limited application of immersed boundary to thermal flows within the LBM has been studied by researchers; the few past studies were limited to Dirichlet boundary conditions and/or using of feedback forcing and heating approaches. In the current paper, the direct forcing and heating approach was used which helps to eliminate the arbitrary constants used in the feedback approaches. The developed new numerical treatments for the Neumann type of boundary condition and for the calculation of the local Nusselt number eliminate the need to determine surface normal and temperature gradient in the normal direction for heat transfer calculation, which is particularly beneficial in cases with deforming or changing boundaries.