Papers by Farah Souayfane
HAL (Le Centre pour la Communication Scientifique Directe), Mar 4, 2018
In this article, a simplified model for melting of a phase change material (PCM) in presence of n... more In this article, a simplified model for melting of a phase change material (PCM) in presence of natural convection and radiation is presented. A modified enthalpy method is adopted to solve the phase change problem, the natural convection occurring in the liquid PCM is accounted for using the enhanced thermal conductivity approach coupled with the scaling theory, and the absorbed shortwave radiation flux is added into the energy equation as a source term using a simplified solution algorithm. Two dimensional implicit finite volume method is used to solve the energy equation. First, the simplified model for melting with natural convection is validated using a CFD model, in addition to experimental and numerical benchmark solutions for a test case. Then, the simplified model for melting with combined natural convection and radiation is applied to the melting of a fatty acid eutectic filled in glass bricks, which will be used later to model the annual thermal behavior of a special translucent façade. This complete model is validated against the lattice Boltzmanndiscrete ordinate method LBM-DOM. It was shown that (1) the proposed simplified model is
A weather-clustering and energy-thermal comfort optimization methodology for indoor cooling in subtropical desert climates
Journal of Building Engineering, 2022
Cette these vise a etudier l'exploitation du rayonnement solaire grâce a un nouveau concept d... more Cette these vise a etudier l'exploitation du rayonnement solaire grâce a un nouveau concept de mur capteur passif. Dans ce contexte, le comportement thermique d’un mur solaire semi-transparent a ete etudie. Le mur fournit un eclairage naturel et est compose d’une couche d’aerogel de silice assurant une isolation thermique et acoustique, et d’un MCP. Ce dernier est contenu dans des briques de verre assurant l’absorption, le stockage et la restitution de chaleur. Ce mur a ete caracterise experimentalement au centre PERSEE a Sophia. Il a ete remarque que la performance thermique du mur est elevee en hiver, tandis qu’une surchauffe estivale a ete rencontree. Un modele numerique simplifie a ete developpe pour modeliser la convection naturelle et le rayonnement pendant la fusion du MCP. Ce modele est valide a l’aide d’un modele CFD, et des resultats de Benchmark. Pour optimiser la performance du mur en ete, un modele numerique du transfert de chaleur a travers le mur a ete developpe s...
On the behavior of renewable energy systems in buildings of three Saudi cities: Winter variabilities and extremes are critical
Journal of Building Engineering
Un modele simplifie base sur l'approche de la conductivite efficace ainsi que sur la theorie ... more Un modele simplifie base sur l'approche de la conductivite efficace ainsi que sur la theorie d'echelle est presente dans ce travail pour modeliser la convection naturelle pendant le processus de fusion d'un materiau a changement de phase. Le modele mathematique est code sous MATLAB en utilisant la methode des volumes finis en deux dimensions. Les resultats du modele simplifie sont ensuite compares a ceux d'un modele CFD complet cree dans COMSOL, et aux resultats numeriques des benchmarks trouves dans la litterature. En particulier, une correlation du nombre de Nusselt correspondant a notre cas d'etude est trouvee, sur la base du modele CFD, et est ensuite implementee dans le modele simplifie. Les resultats montrent que, pour un temps de calcul largement plus court que celui de la CFD, les valeurs de fraction liquide moyenne et de la position du front de fusion sont acceptables. De plus, Les resultats du modele de conductivite efficace propose ont montre un tres b...
Outline : Introduction – Objectives - Physical phenomena - Case study - Numerical procedure – Res... more Outline : Introduction – Objectives - Physical phenomena - Case study - Numerical procedure – Results - Conclusion and perspective
A simplified model for combined natural convection and radiation during melting process of a phas... more A simplified model for combined natural convection and radiation during melting process of a phase change material (PCM) is presented. First, the simplified model for natural convection during melting is validated using a CFD model, in addition to experimental and numerical benchmark solutions for a test case. Then, the simplified model for both natural convection and radiation is applied to the melting of a fatty acid eutectic filled in glass bricks and validated against lattice Boltzmann-discrete ordinate method (LBM-DOM). Finally, the complete model is applied to study the thermal behavior of a translucent wall; then validated experimentally using a full-scale building located in southern France.
Application of PCMs for Enhancing Energy Efficiency and Indoor Comfort in Buildings
Latent Heat-Based Thermal Energy Storage Systems, 2020
International audienc
Melting of a Phase Change Material with Natural Convection and Radiation: A Simplified Model for Engineering Applications
Proceeding of 3rd Thermal and Fluids Engineering Conference (TFEC), 2018
Energy, 2018
The application of an innovative translucent superinsulated latent heat storage wall, combining t... more The application of an innovative translucent superinsulated latent heat storage wall, combining transparent insulation material and phase change materials (TIM-PCM wall), on the envelope of a typical office under different climates is evaluated. Energy and economic analysis related to this application are presented. The simulation process is carried out using an experimentally validated numerical model. The results show that the incorporation of the TIM-PCM wall, on the south orientation, is more efficient than the use of a double-glazed in all considered climates. The optimum TIM-PCM wall area is evaluated economically through life-cycle cost and payback period analysis. The purpose is to ensure an effective performance of the wall in each climate and at the same time to ensure an economic viability. The results show that, in polar and subarctic climates, the application of the TIM-PCM wall has a high economic value and the investment appears to be attractive, the payback period being 10.5 years and 7.8 years respectively. In Dras (continental climate), the use of the wall is found economically unfeasible due to low energy prices and high discount rates. At current prices, the TIM-PCM wall investment in Sacramento (Mediterranean climate) and Toronto (Humid continental) does not offer economic benefits.
Applied Energy, 2018
• TIM-PCM wall provides heat storage/release, heat/sound insulation, and daylighting. • In-situ e... more • TIM-PCM wall provides heat storage/release, heat/sound insulation, and daylighting. • In-situ experimentations carried out in Sophia Antipolis, France. • Numerical model of the heat transfer through the wall is developed. • The model of the wall linked to TRNSYS is validated experimentally. • Thermal comfort with TIM-PCM wall ensured using shading devices or nocturnal ventilation.
International Journal of Thermal Sciences, 2018
This paper details a numerical study of solid-liquid phase change heat transfer in a rectangular ... more This paper details a numerical study of solid-liquid phase change heat transfer in a rectangular enclosure with the aim of optimizing the number, dimension, and positioning of fins in the enclosure. The enclosure is exposed on one side to a constant heat flux of 1000 W/m 2 for 3 h and both the total fin mass and the PCM mass are kept constant in all simulated cases. The heat diffusion equation in the PCM uses the equivalent heat capacity method while natural convection driven PCM motion in the enclosure is modeled through the buoyancy force, using a modified viscosity and an additional volume force term in the Navier-Stokes momentum conservation equation. Three efficiency assessment parameters are used: (i) the height-averaged temperature of the front hot plate which should remain as low as possible for the longer possible time, (ii) the energy stored inside the PCM as a function of time, and (iii) the heat transfer rate and heat flux between the front plate and the PCM. For each simulated case, complementary data such as the standard deviation of temperature along the heated plate and the ratio of sensible heat to latent accumulation are also calculated. Results show that increasing the number of fins diminishes both the stabilization temperature and the stabilization time of the front plate during phase change, and accelerates the sensible and latent storage of energy in the PCM. Using thinner but longer fins provides the same impact except that the stabilization time also increases as the fin length is increased. Besides, at constant fin mass, varying fin spacing have marginal impact on the latent heat storage performance and on the hot plate temperature stabilization. The study also shows that the surface area plays the largest role in the increase of the heat transfer rate between the front plate and the PCM, while configurations which can promote stronger natural convection lead to higher heat flux. Finally, it was observed that systems allowing easier heat transfer to the back plate during melting provide a higher ratio of sensible heat to latent accumulation, while the standard deviation of the front plate temperature decreases as the number of fins or the spacing between fins increases.
Novel Translucent Superinsulated Latent Heat Storage Wall
Science Trends, 2018
Different mathematical models of convection during phase change
2016 3rd International Conference on Renewable Energies for Developing Countries (REDEC), 2016
The aim of this paper is to comprehensively study the mathematical modeling applied for phase cha... more The aim of this paper is to comprehensively study the mathematical modeling applied for phase change taking into consideration the convection in liquid state during melting. Different methods used to model the phase change with convective motion of liquid phase are discussed. First, models based on CFD (computational fluid dynamics) are presented; the solution of Navier-Stokes equations determines the effect of convection in a Newtonian fluid. Secondly, simplified methods are presented, where the convection in the liquid phase change material (PCM) is modeled without the need of the full solution of Navier-Stokes equations. It is clear that the methods based on CFD models are more accurate and express the realistic behavior of the convection effect; however their computational time is very long compared to simplified one.
Phase change materials (PCM) for cooling applications in buildings: A review
Energy and Buildings, 2016
Cooling demand in the building sector is growing rapidly; thermal energy storage systems using ph... more Cooling demand in the building sector is growing rapidly; thermal energy storage systems using phase change materials (PCM) can be a very useful way to improve the building thermal performance. The right use of PCM in the envelope can minimize peak cooling loads, allow the use of smaller HVAC technical equipment for cooling, and has the capability to keep the indoor temperature within the comfort range due to smaller indoor temperature fluctuations. This article presents an overview of different PCM applications in buildings for reducing cooling loads under different climate conditions, and the factors affecting the successful and the effective use of the PCM. Many drawbacks have been found in PCM applications, mainly the intense impact of summer weather conditions over the PCM performance, which prohibits its complete solidification during night, and thus, limiting its effectiveness during the day. Proposed solutions are reviewed in this article. Finally, a topology diagram is presented to summarize the steps leading to an effective use of PCM in building applications.
Applied Thermal Engineering, 2018
In this article, a simplified model for melting of a phase change material (PCM) in presence of n... more In this article, a simplified model for melting of a phase change material (PCM) in presence of natural convection and radiation is presented. A modified enthalpy method is adopted to solve the phase change problem, the natural convection occurring in the liquid PCM is accounted for using the enhanced thermal conductivity approach coupled with the scaling theory, and the absorbed shortwave radiation flux is added into the energy equation as a source term using a simplified solution algorithm. Two dimensional implicit finite volume method is used to solve the energy equation. First, the simplified model for melting with natural convection is validated using a CFD model, in addition to experimental and numerical benchmark solutions for a test case. Then, the simplified model for melting with combined natural convection and radiation is applied to the melting of a fatty acid eutectic filled in glass bricks, which will be used later to model the annual thermal behavior of a special translucent façade. This complete model is validated against the lattice Boltzmanndiscrete ordinate method LBM-DOM. It was shown that (1) the proposed simplified model is
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Papers by Farah Souayfane