Description du sujet de thèse

Research Objectives
Develop a stochastic multiphysics model incorporating the semi-transparency properties of materials to simulate heat transfer (conduction, advection, radiation) in porous media subjected to extreme thermal conditions.

Integrate into the model the effects of reactive atmospheres (H₂, O₂, H₂O) on the aging of materials, their thermal and optical properties, and model how these properties evolve over time.

Contribute to the experimental validation of the developed models through laboratory-scale testing on ceramic heat exchangers and pilot-scale tests in industrial furnaces. This work will be conducted in collaboration with a postdoctoral researcher based at CEMHTI.

Optimize the design of porous heat exchangers using numerical optimization methods to improve their efficiency in industrial environments.

Methodology
Numerical Modeling and Simulation
A Monte Carlo approach will be used to model coupled heat transfer mechanisms (conduction, advection, radiation) across various spatial and temporal scales, taking into account the evolving optical and thermal properties of the material [1]. The objective is to accurately model the behavior of semi-transparent porous materials and simulate the performance of heat exchangers in complex geometries. This approach builds upon the methodology developed at LEMTA, which uses the path integral method for solving complex coupled problems in porous media [2][3].

Experimental Validation
Laboratory tests will be conducted on AZS ceramic heat exchangers to validate the simulation predictions. This will include measuring the thermal and optical properties of the materials before and after exposure to reactive atmospheres. Complementary experimental setups from CEMHTI and LEMTA will be used for these characterizations [4][5]. In addition, large-scale testing campaigns will be carried out on existing pilot furnaces at Saint-Gobain Recherche.

Design and Optimization
Optimization methods, coupled with the developed simulation code, will be used to design high-efficiency porous heat exchangers, aiming to minimize pressure drop and maximize energy recovery through the porous structure. Simulation of velocity fields within the exchanger and the integration of experimental data into the multiphysics model will help define optimal specifications for an industrial-scale exchanger.

Study of Material Aging Effects
The phenomena of corrosion and degradation of the optical and thermal properties of AZS materials due to exposure to reactive atmospheres (hydrogen and water vapor) will be characterized. Predictive models will be developed to describe the evolution of material properties based on the aging observed during operational cycles [6].

Partners
LEMTA (University of Lorraine): Modeling and thermal property characterization

CEMHTI (CNRS): Optical property characterization and aging studies

Saint-Gobain Recherche: Industrial-scale testing and integration of heat exchangers into pilot furnaces

Contexte de travail

This PhD thesis is part of the ANR ACACIA project and the joint laboratory Canopée, a collaboration between CEMHTI, LEMTA, and Saint-Gobain Recherche. The objective is to model and analyze coupled heat transfer in semi-transparent ceramic materials designed for waste heat recovery in very high-temperature industrial environments.

The ACACIA project aims to design innovative heat recovery solutions under extreme conditions, particularly in the presence of reactive gases such as hydrogen and water vapor. These atmospheres can alter the thermal and optical properties of ceramics, posing major challenges in terms of durability and performance.

In this context, porous AZS ceramics (Alumina-Zirconia-Silica) represent a promising alternative to conventional systems. Their three-dimensional structure with a high specific surface area enables optimal interaction between the hot gas flow and the material, promoting efficient heat transfer through conduction, convection, and radiation. Designed to minimize pressure drop while maximizing thermal absorption, these devices are particularly well-suited for the extreme conditions found in industrial furnaces, where temperatures often exceed 1000°C.

Supervision: Olivier Farges (LEMTA, supervisor), Olivier Rozenbaum (CEMHTI, co-supervisor), Johann Meulemans and Refet Yalcin (industrial partners, Saint-Gobain Recherche)

Le poste se situe dans un secteur relevant de la protection du potentiel scientifique et technique (PPST), et nécessite donc, conformément à la réglementation, que votre arrivée soit autorisée par l'autorité compétente du MESR.

Contraintes et risques

Location:

Main location: Nancy – LEMTA (University of Lorraine)

Occasional travel to:

Orléans – CEMHTI (CNRS)

Aubervilliers – Saint-Gobain Recherche

Expected Impact
This PhD will make a significant scientific contribution to the understanding of heat transfer in high-temperature semi-transparent porous media, while also providing practical solutions to improve the energy efficiency of industrial processes involving heat exchangers.
The results of this research could be applied in sectors such as glass manufacturing, metallurgy, and the cement industry, thereby contributing to the reduction of greenhouse gas emissions.