Single-phase Flow Model Research Articles

An extended two-parameter mixed-dimensional model of fractured porous media incorporating entrance flow and boundary-layer transition effects

We develop an enhanced reduced model for single-phase flow in fractured porous media capable of incorporating more realistic interface conditions at the fracture terminations. In addition to the traditional dimensional model reduction, where the elements of the discrete fracture network are treated as lower dimensional manifolds embedded in the porous matrix, we explore the microscale behavior of the boundary layer flow at the entrances of a fracture bounded by two parallel plates to construct a new set of interface conditions of Robin-type, giving rise to localized pressure jumps at the fracture edges. Within this enriched description, sharper reduced flow and tracer transport mixed-dimensional models are constructed in the asymptotic limit ruled by two small parameters related to the ratio between fracture aperture and entrance developing length and a macroscopic length scale. The discrete flow/transport mixed-dimensional model is discretized by a new discontinuous Galerkin(dG)-based formulation. An adequate version of the Galerkin-Newton method is developed for the numerical treatment of the non-linear Robin interface condition. Considering several fracture arrangements, numerical results illustrate the sharper description of the model proposed herein in predicting flow and tracer transport patterns in fractured media.

Implementation of a Drift Flux Model into SAM with Development of a Verification and Validation Test Suite for Modeling of Noncondensable Gas Mixtures

The advanced thermal-hydraulic system code, System Analysis Module (SAM), was originally developed for the modeling of single-phase flow in advanced reactors. It has since been expanded to include a four-equation drift flux model for the modeling of two-phase flows containing a noncondensable gas. The model was expanded to support the modeling of molten salt reactor (MSR) designs in which the fuel is directly dissolved in the circulating coolant. These designs have shown that circulating gas bubbles can play an important role in the management of fission products and the operational behavior of the reactor. A drift flux model was implemented to more accurately capture the localized behavior of the void in the core and its impact on the mass transfer of fission products. A thorough assessment of the new model was performed by developing a verification and validation test suite. Verification problems were designed to test all major terms in the new governing equations. The new model converged to the correct solution at the expected order of accuracy for all verification cases. The validation cases included a wide range of flow and void conditions in different pipe geometries. Although higher void experiments show a slight underprediction of void by the drift flux model, experiments that aim to reproduce Molten Salt Reactor Experiment (MSRE) experimental conditions show good agreement with the model. The gas transport model was activated for a SAM model of the MSRE to demonstrate that it can be used in a more complex model. This gas transport model will be used along with an interfacial area transport equation being implemented in SAM for the prediction of mass transport behavior in MSR conditions.

Precipitation and evaporation affecting landfill gas migration into passive methane oxidation biosystems: Models development and verification

Passive methane oxidation biosystems (PMOBs) are developed as an innovative and cost-effective solution to reduce methane (CH4) emissions from municipal solid waste landfills. A PMOB consists of a methane oxidation layer (MOL) and an underlying gas distribution layer (GDL). The length of unrestricted gas migration (LUGM) has been recently proposed as the design criterion for PMOBs where the LUGM is calculated as the horizontal length along the MOL-GDL interface with the volumetric gas content (θa) exceeding the threshold volumetric gas content (θa,occ). This paper examined water and gas migration within three PMOBs with different MOL-GDL interfaces subject to precipitation and evaporation using verified numerical models. The results show that the use of a single-phase flow model underestimates the LUGM values of the PMOB for heavy precipitation events, and a two-phase flow model should be used to calculate both the LUGM and the total gas mass flow rate into the MOL when designing PMOBs. Both zig-zag and trapezoidal MOL-GDL interfaces can redistribute the gas mass flow rate at the MOL-GDL interface, while the trapezoidal MOL-GDL interface slightly outperforms the zig-zag MOL-GDL interface for enhancing the total gas mass flow rate into the MOL when comparing with the planar MOL-GDL interface. The zig-zag and trapezoidal MOL-GDL interfaces allow gas migration in the upper part of each PMOB segment even when the lower part of each PMOB segment was filled with water, and thus have a potential to minimize hotspot formation.

A two-phase flow model simulating water penetration into pharmaceutical tablets

The purpose of the study is introduce a two-phase flow model to simulate water penetration into pharmaceutical tablets. This model was built by integrating Darcy’s law with the continuity principle, on the premise that water penetration was driven by capillary actions. Notably, this model concerned both the ingress of water (wetting phase) and simultaneous displacement of air (non-wetting phase). Due to the interference of the two fluids, the relative permeability and capillary pressure vary during water penetration. Evolution of these parameters was incorporated in the model. Calibration of the model by water penetration experiments of the microcrystalline cellulose (MCC) tablet yielded an average pore radius of 42 nm. This derived result was corroborated by FIB-SEM analysis revealing the presence of extensive microporosity within MCC particles with an average radius of ∼30 nm. Further validation was achieved through close resemblance between the simulated and experimental water penetration profiles of MCC tablets possessing different porosities. Overall, this study underscored the advantage of the two-phase flow model over single-phase flow models, by capturing the dependence of permeability and capillary pressure on water saturation. Therefore it holds promise for an enhanced description of water penetration into tablets.

Optimizing thermal performance of nanofluid impinging upon a nonlinearly stretching sheet using Taguchi technique

The main purpose of this article is to optimize the thermal performance of system involving stagnation point flow of A l 2 O 3 + water based nanofluid over a nonlinearly stretching surface. The mathematical model for the problem under consideration utilizes the Tiwari and Das’s single phase flow model for the nanofluid. The aim is to find a similar solution of the problem using some suitable similarity variables. The partial differential equations dictating the flow situation are converted into dimensionless ordinary differential equations. Numerical solution of the system of dimensionless ordinary differential equations has been obtained with the help of MATLAB’s inbuilt bvp4c package. Further, Taguchi analysis along with ANOVA and regression analysis have been performed against the variable like Pr , γ , n and ϕ corresponding to response variable to predict the optimal heat transfer of the system. Outcomes of ANOVA indicate that Pr has maximum and ϕ has minimum influence over the Nusselt number.

Entropy analysis of a non-Darcian mixed convective flow of Cu-Al2O3-based hybrid nanofluid with thermal dispersioneffect

Entropy measures the disorderness or randomness of the systems. It may affect the effectiveness and performance of the thermal systems. That is why entropy analysis is one of the trending research topic in modern era of society. The motive of this article is to present a comprehensive analysis of entropy generation and thermal dispersion effect on mixed convective flow of (Cu-Al2O3)/(H2O) based hybrid nanofluid along a plate submerged in a non-Darcy porous medium. The mathematical model describing the flow problem encompasses a system of partial differential equation, resulting from the single-phase flow model of the nanofluid combined with the Darcy-Forchheimer expression for porous medium flow. The dimensional system of partial differential equation is transformed into a non-dimensional nonlinear ordinary differential system through a similarity transformations and subsequently, the system is solved using the BVP4C module in MATLAB. The study analyzes the flow variables and entropy generation with respect to the parameters inherent in the problem. The findings suggests that, the increasing thermal dispersion effects enhances the Heat transfer rate of the hybrid nanofluid. Further, it is reported that the entropy generation in hybrid nanofluid is lower than the mono nanofluid which makes the hybrid nanofluid a better choice for entropy management in the thermal systems. The outcome of the research has practical implications in various real-life applications, such as crude oil production, oil flow filtration, electronic cooling equipment, etc.

Learning a general model of single phase flow in complex 3D porous media

Modeling effective transport properties of 3D porous media, such as permeability, at multiple scales is challenging as a result of the combined complexity of the pore structures and fluid physics—in particular, confinement effects which vary across the nanoscale to the microscale. While numerical simulation is possible, the computational cost is prohibitive for realistic domains, which are large and complex. Although machine learning (ML) models have been proposed to circumvent simulation, none so far has simultaneously accounted for heterogeneous 3D structures, fluid confinement effects, and multiple simulation resolutions. By utilizing numerous computer science techniques to improve the scalability of training, we have for the first time developed a general flow model that accounts for the pore-structure and corresponding physical phenomena at scales from Angstrom to the micrometer. Using synthetic computational domains for training, our ML model exhibits strong performance (R 2 = 0.9) when tested on extremely diverse real domains at multiple scales.

A homogenized two-phase computational framework for meso- and macroscale blood flow simulations

Background and ObjectiveOwing to the complexity of physics linked with blood flow and its associated phenomena, appropriate modeling of the multi-constituent rheology of blood is of primary importance. To this effect, various kinds of computational fluid dynamic models have been developed, each with merits and limitations. However, when additional physics like thrombosis and embolization is included within the framework of these models, computationally efficient scalable translation becomes very difficult. Therefore, this paper presents a homogenized two-phase blood flow framework with similar characteristics to a single fluid model but retains the flow resolution of a classical two-fluid model. The presented framework is validated against four different sets of experiments. MethodsThe two-phase model of blood presented here is based on the classical diffusion-flux framework. Diffusion flux models are known to be less computationally expensive than two-fluid multiphase models since the numerical implementation resembles single-phase flow models. Diffusion flux models typically use empirical slip velocity correlations to resolve the motion between phases. However, such correlations do not exist for blood. Therefore, a modified slip velocity equation is proposed, derived rigorously from the two-fluid governing equations. An additional drag law for red blood cells (RBCs) as a function of volume fraction is evaluated using a previously published cell-resolved solver. A new hematocrit-dependent expression for lift force on RBCs is proposed. The final governing equations are discretized and solved using the open-source software OpenFOAM. ResultsThe framework is validated against four sets of experiments: (i) flow through a rectangular microchannel to validate RBC velocity profiles against experimental measurements and compare computed hematocrit distributions against previously reported simulation results (ii) flow through a sudden expansion microchannel for comparing experimentally obtained contours of hematocrit distributions and normalized cell-free region length obtained at different flowrates and inlet hematocrits, (iii) flow through two hyperbolic channels to evaluate model predictions of cell-free layer thickness, and (iv) flow through a microchannel that mimics crevices of a left ventricular assist device to predict hematocrit distributions observed experimentally. The simulation results exhibit good agreement with the results of all four experiments. ConclusionThe computational framework presented in this paper has the advantage of resolving the multiscale physics of blood flow while still leveraging numerical techniques used for solving single-phase flows. Therefore, it becomes an excellent candidate for addressing more complicated problems related to blood flow, such as modeling mechanical entrapment of RBCs within blood clots, predicting thrombus composition, and visualizing clot embolization.

Electromagnetohydrodynamic (EMHD) flow through porous media—Multiscale approach

Electromagnetohydrodynamic (EMHD) flow in porous media is recently gaining substantial attention from researchers. EMHD involves analyzing the combined effects of electric and magnetic fields on the behavior of fluid flow through a medium. The effective permeability of porous materials is of great interest for many environmental and industrial applications. The present study focuses on the modeling of single-phase fluid flow in porous media under combined effects of electric and magnetic fields at the pore scale by employing a two-scale computational homogenization technique. The primary objective of this study is to establish a definition of “electromagnetopermeability” that accurately characterizes the effective permeability of a porous medium under the EMHD effects. Additionally, the study investigates the impact of wall zeta potential, Debye length, and the intensity of external magnetic and electric fields, represented by the Hartmann number and the non-dimensional parameter S, respectively, on the electromagnetopermeability tensor within an idealized three-dimensional periodic porous domain. It is observed that the EM-permeability is significantly affected by the existence of the flow-assisting and flow-opposing components of the Lorentz force term in the momentum equation. The implications of this research extend to several industries, including geology, medicine, chemistry, and energy conversion.

Thermal radiation effect on the Maxwell graphene based nanofluid passing through a squeezing channel

This article presents a comparative analysis of flow and heat transfer characteristics of magnetohydrodynamic flow of non-Newtonian base fluid (ethylene glycol) and nanofluid (ethylene glycol + graphene) between two parallel plates moving toward/apart to each other. The study also includes the effects of Joule dissipation, thermal radiation, and heat absorption. The mathematical model that governs the flow of the above-described problem is a single-phase flow model for nanofluids that is augmented with the non-Newtonian Maxwell fluid model. Similarity transformation was used to change controlling partial differential equations into coupled nondimensional ordinary differential equations. The numerical solution is obtained by employing the shooting technique along with fourth order Runge–Kutta Fehlberg method. The impact of several physical characteristics on fluid velocity, temperature, the coefficient of skin friction, and the heat transfer rate is also explored. As a result, this research has the potential to be used in biomedical engineering as well as powder technology.

Numerical simulation and structural optimization of electrolyzer based on the coupled model of electrochemical and multiphase flow

Due to the uneven distribution of electrolytes in the electrolyzer, gas retention zones are generated, which will reduce hydrogen production efficiency and shorten the lifespan of electrodes. Therefore, it is of great significance for developing water electrolysis to optimize channels' structure and improve electrolyte distribution uniformity. This article constructs a coupled model of electrochemical and multiphase flow. It calculates the overall process from the electrolyte flowing into the electrolyzer, to the electrochemical reaction inside the porous electrode, and then to the discharge of the electrolyte together with the product. The comparative analysis shows that due to the interaction between gas-liquid phases, there is a significant difference between the actual flow and the ideal single-phase flow. The average velocity of the electrolyte in the channel calculated by the coupling model is more than 20% different from that calculated by the single-phase flow model. Moreover, the velocity distribution is not directly related to the phase distribution. Based on the flow pattern of electrolytes in the flow channel, the structural parameters of the mastoid were optimized. The elliptical mastoid can evenly decrease the specific energy consumption by 45.87% compared to the circular mastoid. By reducing the ratio of mastoid distance to mastoid diameter from 7.14 to 5.71, the specific energy consumption can be evenly decreased by 30.28%.

A Diffusion-Inertia Model for the simulation of particulate pollutants dynamics inside a car cabin

Simulations of particle pollutants dynamics inside a car cabin were performed using the Diffusion-Inertia Model (DIM) coupled to the RANS (Reynolds-averaged Navier–Stokes equations) k−ω SST turbulence model for single-phase flow. The DIM model has been implemented in a commercial CFD solver and then validated on some reference flow configurations. The validation included particle dispersion in ventilated chambers of one and two compartments, particle deposition in circular 90°bends, and particle-laden jet flow. The DIM model has shown interesting capabilities in taking into account various transport mechanisms such as the transport by the mean flow, gravitational settling, centrifugal effect due to flow streamline curvatures, molecular and turbulent diffusion, and also turbophoresis transport mechanism due to turbulent energy gradients. Moreover, the application of the DIM model to the simulation of solid particles, characterizing particulate pollutants, has revealed characteristic dynamics that is mainly determined by the airflow topology, particularly for ultrafine and fine particles (0.1, 1 and 2.5μm). Inertial effects were found to become significant only for coarse particles (5 and 10μm), as the impact of gravitational and centrifugal effects gradually becomes more noticeable. Furthermore, the risk of exposure to high levels of particulate pollutants has been clearly established when considering the presence of occupants inside the vehicle cabin. These concentration levels are linked in particular to the complex interaction between occupants’ heads and the internal flow, as well as to the tendency of particles to accumulate in the upper part of the cabin and to the rapid homogenization observed throughout the whole interior volume.

Multiphase flow gas transport in a deep geological repository

Gas transport in porous media is of interest in many industrial applications, such as the oil and gas industry, geological storage, and deep geological repositories for radioactive waste. In a deep geological repository, gas will be generated due to the corrosion of metallic components and the degradation of organic materials. This leads to a build-up of gas pressure, which may activate gas transport through the host rock as well as the excavation-damaged zone around backfilled galleries.
 In order to understand different transport mechanisms involved, numerical simulations were performed, and the results were compared with laboratory data. In the framework of the EURAD/GAS project, a gas pressure-dependent permeability model was implemented into the finite element code OpenGeoSys-6 (OGS-6) [1]. The permeability alteration in this model is a function of gas pressure. The laboratory experiments showed that the rate of permeability change are different at low and high gas pressures. Therefore, the permeability model employed a threshold pressure ( to categorize this behaviour.
 and are empirical parameters. Moreover, two other permeability models were employed to study the hydro-mechanical behaviour of the host rock and permeability changes. In the strain-dependent permeability model, the permeability change was related to the elasto-plastic behaviour of the host rock, and in the embedded fracture model, it was related to the opening and closure of fractures [3] [4]. Thus, volumetric elastic strain and equivalent plastic strain are employed to be the controlling variables.
 The initial permeability of the intact rock samples were determined by applying a constant pressure at the upstream and downstream of the samples (i.e. constant pressure gradient). The imperical parameters were determined by matching experimental and numerical results.
 Two types of gas injection tests carried out by the Institute for Rock Mechanics (IFG GmbH, See Figure 1) were used to investigate the gas transport through Opalinus Clay and to examine the permeability models [2]. The first experiment demonstrates an advective-diffusiion gas transport through the sample and an elastic deformation. The second experiment highlights the formation of a tensile fracture (plastic deformation and preferred flow path). In both experiments the advective transport is the dominant transport mechanism. The strain-dependent permeability model was successfully applied to reproduce the hydro-mechanical behaviour of the host rock in both elastic deformation test and tensile fracture test (see Figures 2 and 3). The hydro-mechanical response of a saturated single phase flow model was compared with the behaviour of a saturated two-phase flow model. Both single phase and two-phase flow models were able to describe the hydraulic as well as mechanical behaviour of the experiments performed. Therefore, one can conclude that in these experiments the water phase (wet-phase) was immobile.
 A gas injection test under triaxial conditions was performed by École Polytechnique Fédérale de Lausanne (EPFL) in saturated Opalinus Clay (Fig. 4). The numerical simulations reproduced the hydro-mechanical behaviour of the sample during the gas injection test. A two-phase flow model was applied to simulate the experiment. The relative permeabilities and capillary pressure functions followed Mualem approach and van Genuchten formulation, respectively. The outflow volume and mechanical response of the sample were measured. The experimental results were in good agreement with the numerical ones. The results of the modelling illustrated the penetration of gas into the sample and hence, the displacement of water (see Figures 5 and 6).

Modeling of subcooled flow boiling for hypervapotron in divertor of fusion reactor based on RPI model

The divertor is the key in-vessel component to remove the high heat flux and impurities in magnetic confinement fusion reactor. Hypervapotron (HV) has been developed as one of the candidates for cooling structure of divertor, owing to its excellent heat transfer performance in subcooled flow boiling. To address the design and development requirements of divertor, a suitable model for single-phase and two-phase flow of HV are developed. Four combination models of boiling properties expressed by different empirical correlations are evaluated. The results indicate that the LC-UN (Lemmert-Chawla, Unal) model shows a good agreement with the experimental results of Lim et al. (2022), with average deviation of 8.15%. Moreover, for the first time, the model successfully predicts the onset of fully developed nucleate boiling (OFDB) point of HV. Based on the LC-UN model, the detailed heat transfer and flow characteristics of HV are revealed. It shows that the boiling process is independent between each slot due to the fin barrier, and the bubbles are condensed by the subcooled main stream after leaving the wall. The “double vortex” in HV intensifies the interaction between vapor and liquid phase, preventing the aggregation of bubbles, allowing it has excellent heat transfer performances.

Simulation of wellbore temperature and heat loss in production well in geothermal site

ABSTRACT Knowledge of fluid flow temperature along the wellbore can be useful for a realistic calculation of the total heat production in geothermal wells. Therefore, wellbore modeling is an important part of the characterization of geothermal wells and predicting their future behavior. This study describes the dynamic transport of transient heat and fluid dynamic transport inside a geothermal well and also heat loss in the surrounding rocks. The objective of this investigation is to accurately predict temperature and pressure variations within the producing well GPK2 of the geothermal site Soultz-sous-Forêts. The temperature effect of possible leakage zones in the reservoir section of the production casing was also considered. A single-phase flow modeling was carried out using Comsol software. Our study highlights that the properties of the flow (well flow rates for steady and unsteady flow), of the fluid (density, viscosity, chemical composition), and the well (diameter, length, thermal properties of environments) are parameters, which directly influence the pressure and temperature profiles of the well. A sensitivity study has been carried out to demonstrate the role that these parameters play in the heat transport occurring in this well. According to our simulated results, during the flow of hot water in GPK2 well the production temperature of water decreases by dozen degrees of its downhole temperature. It is also shown that the leakage zone affects the temperature, decreasing it at least by 1–2°C.

Development and validation of multiphysics PWR core simulator KANT

KANT (KAIST Advanced Nuclear Tachygraphy) is a PWR core simulator recently developed at Korea Advance Institute of Science and Technology, which solves three-dimensional steady-state and transient multigroup neutron diffusion equations under Cartesian geometries alongside the incorporation of thermal-hydraulics feedback effect for multi-physics calculation. It utilizes the standard Nodal Expansion Method (NEM) accelerated with various Coarse Mesh Finite Difference (CMFD) methods for neutronics calculation. For thermal-hydraulics (TH) calculation, a single-phase flow model and a one-dimensional cylindrical fuel rod heat conduction model are employed. The time-dependent neutronics and TH calculations are numerically solved through an implicit Euler scheme, where a detailed coupling strategy is presented in this paper alongside a description of nodal equivalence, macroscopic depletion, and pin power reconstruction. For validation of the steady, transient, and depletion calculation with pin power reconstruction capacity of KANT, solutions for various benchmark problems are presented. The IAEA 3-D PWR and 4-group KOEBERG problems were considered for the steady-state reactor benchmark problem. For transient calculations, LMW (Lagenbuch, Maurer and Werner) LWR and NEACRP 3-D PWR benchmarks were solved, where the latter problem includes thermal-hydraulics feedback. For macroscopic depletion with pin power reconstruction, a small PWR problem modified with KAIST benchmark model was solved. For validation of the multi-physics analysis capability of KANT concerning large-sized PWRs, the BEAVRS Cycle1 benchmark has been considered. It was found that KANT solutions are accurate and consistent compared to other published works.

Study on Gas–Solid Two–Phase Flow Characteristics of One–Furnace with Two–Tower Semi–Dry Desulfurization in Circulating Fluidized Bed Boiler

A single–phase flow model was used to analyze the uniformity of the flow field in the desulfurization tower under different baffle combinations, and a multiphase flow model was used to explain the gas and solid two–phase flow characteristics and chemical reaction characteristics in the tower. The stability of the flow behavior of gas and solids in one furnace and two towers was discussed. The results show that the installation of shielding plates at appropriate positions in the tower for sulfur removal is beneficial to enhance the uniform distribution of flow in space, reduce the pulsation interference of bed pressure in the tower, keep the state of gas and solid flow unchanged, and maintain the efficiency of desulfurization at a high level. Reducing the instability of gas–solid two–phase flow is the basis of ensuring the stable switching between single and double towers.

Assessment of the influence of scaling on turbulent mixing in downcomer and core-inlet flow distribution

In the present article, Computational Fluid Dynamics (CFD) simulations are used to assess the effects of classical scaling approaches on turbulent mixing in the downcomer and core-inlet regions of typical Reactor Pressure Vessels (RPVs), applying validated CFD models in two sets of numerical tests. In the first set, simulations of ROCOM Tests 1.1. and 2.2 performed under two different geometric scales showed that the modeling of single-phase flow with mixed convection on a scaled-down geometry is able to provide a very good approximation of the core inlet mixing dynamics in the reference reactor. For the second set, the effects of the selection of global non-dimensional parameters to compare RPVs of varying designs under steady-state operating conditions are studied via the injection of a passive component, and a radial grouping of the mixing scalar is proposed for comparisons involving different core configurations.

Numerical study on carbon dioxide removal from the hydrogen-rich stream by supersonic Laval nozzle

A hydrogen purification system with a supersonic nozzle pretreatment process is proposed to improve the performance of traditional CO2 removal processes from hydrogen-rich streams. A mathematical model of the H2–CO2 double-component condensation was established to investigate the feasibility of CO2 capture in a hydrogen-rich stream using a supersonic nozzle. Compared to the single-phase model, this model is more similar to the objective flow facts and can effectively correct the deviation of the single-phase flow model by 21.4%. Furthermore, the parameters in the H2–CO2 double-components spontaneous condensation process in the nozzle were analyzed, and the microscopic mechanism of CO2 spontaneous condensation was clarified. Finally, the effects of the inlet parameters on the carbon capture efficiency were analyzed. The results indicated that the nozzle is more suitable for purifying hydrogen-rich streams with low temperatures and high carbon content, confirming the possibility of using a supersonic nozzle as a carbon capture method.

A computationally efficient and high-fidelity 1D steady-state performance model for PEM fuel cells

The performance of a proton exchange membrane (PEM) fuel cell is determined by many factors, including operating conditions, component specifications, and system design, making it challenging to predict its performance over a wide range of operating conditions. Existing fuel cell models can be complex and computationally demanding or may be over-simplified by neglecting many transport phenomena. Therefore, a high-fidelity and computationally efficient model is urgently needed for the model-based control of fuel cells. In this study, semi-implicit multi-physics numerical models have been established, taking the mass, momentum, reactants, liquid water, membrane water, electrons, ions, and energy in all fuel cell components into account. The developed 1D model is of high fidelity by incorporating the two-phase flow, non-isothermal effect, and convection, and is still computationally efficient. These models are validated against data from an auto manufacturer with good agreements, and the computing efficiency is evaluated on a modest laptop computer. The modeling results suggest that the two-phase flow model exhibits better prediction accuracy than the single-phase flow model when reactants are fully humidified, while under low humidity conditions, the two models present equivalent performance as liquid water does not exist in the fuel cell components. The results also suggest that the maximum convective/diffusive ratio of H2, O2, and vapor mass fluxes can be 12%, 5.3%, and 35%, respectively, which are ignored in most diffusion-dominant models. The developed models are computationally efficient, requiring only 0.56 s and 0.26 s to simulate a steady-state operation of fuel cells for the two- and single-phase flow models, respectively. This implies that the developed models are suitable for the control of PEM fuel cells.