Modeling of PCM-based enhanced latent heat storage systems using a phase-field-porous media approach

Sweidan, Abdel Hassan; Heider, Yousef; Markert, Bernd

doi:10.1007/s00161-019-00764-4

Cited by 35 publications

(18 citation statements)

References 83 publications

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“…Regarding the system of nonlinear differential equations, a modified Newton-Raphson iteration procedure is utilized by FlexPDE to attain the numerical solution, where the Jacobian matrix of the current system equations is computed and Newton iterations are performed at each time step until the convergence is reached. Useful and detailed information to the solution of coupled problems can be found in [1,2,72,73,85,107] and the included references.…”

Section: Numerical Implementationmentioning

confidence: 99%

“…Away from the phase-change applications, the PFM can also be found in recent contributions within fracture mechanics and crack propagation as, e.g., [6, 39, 51-53, 84, 90, 91, 94]. The PFM is being recently applied to tackle phase-change problems on the macroscale [107,120,121], especially for studying the behavior of phase-change materials (PCMs). However, none of the above mentioned phase-change-PFM-based articles considered the challenging problem of porous structure deformation due to the volume changes of the fluid during solidification or melting.…”

Section: Introductionmentioning

confidence: 99%

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Experimental study and numerical modeling of the thermo-hydro-mechanical processes in soil freezing with different frost penetration directions

et al. 2021

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This research work presents an experimental and numerical study of the coupled thermo-hydro-mechanical (THM) processes that occur during soil freezing. With focusing on the artificial ground freezing (AGF) technology, a new testing device is built, which considers a variety of AGF-related boundary conditions and different freezing directions. In the conducted experiments, a distinction is made between two thermal states: (1) The thermal transient state, which is associated with ice penetration, small deformations, and insignificant water suction. (2) The thermal (quasi-) steady state, which has a much longer duration and is associated with significant ice lens formation due to water suction. In the numerical modeling, a special focus is laid on the processes that occur during the thermal transient state. Besides, a demonstration of the micro-cryo-suction mechanism and its realization in the continuum model through a phenomenological retention-curve-like formulation is presented. This allows modeling the ice lens formation and the stiffness degradation observed in the experiments. Assuming a fully saturated soil as a biphasic porous material, a phase-change THM approach is applied in the numerical modeling. The governing equations are based on the continuum mechanical theory of porous media (TPM) extended by the phase-field modeling (PFM) approach. The model proceeds from a small-strain assumption, whereas the pore fluid can be found in liquid water or solid ice state with a unified kinematics treatment of both states. Comparisons with the experimental data demonstrate the ability and usefulness of the considered model in describing the freezing of saturated soils.

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Section: Numerical Implementationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experimental study and numerical modeling of the thermo-hydro-mechanical processes in soil freezing with different frost penetration directions

et al. 2021

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“…In the last few decades, the phase-field method has emerged as a powerful tool that has been applied by the current authors, among other research groups, in fields like fracture mechanics [1][2][3][4] or for modeling of phase-change materials [5,6]. With focus in this contribution on unsaturated porous media fracture, the material under consideration ϕ is composed of immiscible three phases, i.e.…”

Section: Mathematical Modellingmentioning

confidence: 99%

Advancements in multi‐phase unsaturated porous media fracture

Heider

Sun

Markert

2021

Proc Appl Math and Mech

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The focus in this research is on introducing an accurate and stable numerical modeling framework and to compare the numerical results with experimental data from the literature for desiccation‐induced fracturing of unsaturated porous materials. The macroscopic modeling approach is based on combined continuum porous media mechanics and a diffusive phase‐field method (PFM). In the case of unsaturated porous media, one has to deal with more than one pore fluid (e.g. water and air). In this, the mechanical behavior can be expressed via using the Bishop's effective stress principle, which considers the total stress, the capillary pressure (air pressure minus water pressure), and saturation degree. The onset of desiccation‐induced fracturing is driven by the capillary pressure, which leads to degradation not only in the effective stresses but also in the capillary pressure itself. In this contribution, we discuss via a numerical example the effect of considering the air pressure variation on the cracking process and numerical stability. Besides, we briefly discuss the potential inclusion of machine‐learning material laws, such as for retention curves and anisotropic permeability, using, e.g., deep recurrent neural networks (RNN) to improve the model accuracy.

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“…Therefore, assigning temperaturedependent properties is a common practice when modeling such processes, see, e.g., [1,2]. The phase-field method (PFM) has emerged as a robust tool in modelling different engineering processes, such as the phase change of materials [3,4] or even fracture simulation [5]. In the current study, the PFM with φ as the phase-field variable is incorporated into the coupled thermomechanical problem to track the melting and solidification front during the welding process.…”

Section: Mathematical Modellingmentioning

confidence: 99%

A thermomechanical‐phase‐field approach for modeling of residual stresses in fusion welding

Ali

Heider

Markert

2021

Proc Appl Math and Mech

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The welding process of metallic components, such as using gas tungsten arc welding (GTAW), is often accompanied by detrimental deformations and residual stresses, which affect the strength and functionality of these welded components. In this work, a phase-field model, usually used to track the state of the phase-change materials, is embedded in a thermo-elastoplastic finite element model in order to simulate the welding process and the residual stresses. The phase-field method (PFM) enables us to track the melting front of the metal, due to the welding heat source, and to split the analysis domain into soft and solid regions. In this way, temperature and phase-field-dependent material properties can properly be assigned to different regions in the domain. The phase-field evolution is governed by Allen-Cahn equation and relies on specification of the free energy density function as the main driving force for the phase change. Having a coupled thermomechanical process during the welding heating-cooling cycle, the onset of residual stresses is associated with plastic deformations and can be observed after cooling to the ambient temperature. The plasticity model considers J2 plasticity with isotropic hardening. The coupled nonlinear system of equations is solved in the open-source FE package, FEniCS, with time discretization based on the finite difference method.

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Modeling of PCM-based enhanced latent heat storage systems using a phase-field-porous media approach

Cited by 35 publications

References 83 publications

Experimental study and numerical modeling of the thermo-hydro-mechanical processes in soil freezing with different frost penetration directions

Experimental study and numerical modeling of the thermo-hydro-mechanical processes in soil freezing with different frost penetration directions

Advancements in multi‐phase unsaturated porous media fracture

A thermomechanical‐phase‐field approach for modeling of residual stresses in fusion welding

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