Missions

Researcher in numerical fluid mecanics and heat transfer

Activités

The tasks planned for this work include:
1. A literature review and familiarization with the numerical tools.
2. Development of simulations for an isolated tube.
3. Comparison of Neptune_CFD results with the experimental database and with simulation results obtained using Fluent.
4. A parametric study of the heat exchanger geometry to optimize its performance.
5. Dissemination of the results of the study.

Compétences

We are looking for a PhD graduate in numerical fluid mechanics or energy engineering, with a strong interest in modelling. Experience with HPC computations and a programming language (C/C++/Python) is required.

Contexte de travail

Fluidized beds exhibit exceptional transport and mixing characteristics. They particularly benefit from efficient contact between the dispersed phase and the gas phase, from the thermal inertia of the particulate phase, and from their excellent heat-transfer capabilities to the walls. These properties make them widely used in the energy sector, especially for the development of innovative processes addressing the challenges of the energy transition.
Gas–solid fluidized beds are studied at the PROMES laboratory as an alternative to current heat-transfer fluids used to transport heat derived from solar radiation in concentrating solar power (CSP) plants. This research has notably been supported by the European projects CSP2, Next-CSP, and currently P2P [1–4].
In this process, solar radiation is concentrated onto vertical tubes through which a gas–particle mixture circulates (a system similar to a circulating fluidized bed, but with denser gas–particle suspensions). The fluidized bed functions here as a heat-transfer fluid, carrying heat to a thermal storage unit. The particles are then injected into a heat exchanger, where they release their energy to the working fluid of the thermodynamic cycle (air turbine or supercritical CO₂ turbine). This heat exchanger consists of several compartments at different temperatures. The working fluid flows counter-current to the particles inside tubes immersed in successive fluidized beds.
Understanding and controlling the flow regimes and the associated heat-transfer mechanisms in fluidized beds remain key scientific challenges for the development of this technology. The couplings between hydrodynamics, heat transfer, the two-phase nature of the flow, wall effects, and particle collisions make the physics particularly complex.
The goal of this postdoctoral position is to develop local-scale Euler-Euler simulations of heat exchange between the fluidized bed and the tubes in which the working fluid of the thermodynamic cycle circulates. These simulations will be performed using the Neptune_CFD software. A parametric study of the heat exchanger geometry (tube arrangement) will then be carried out to optimize its performance. Comparisons with experimental data from various European projects will allow assessment of the reliability of the wall heat-flux modelling. If necessary, new formulations may be proposed.

Reference :
[1] Next-CSP (2020) and Powder2Power : High Temperature Concentrated Solar Thermal Power Plant with Particle Receiver and Direct Thermal Storage. Available online: (accessed on October 2022)
[2] R. Gueguen, G. Sahuquet, S. Mer, A. Toutant, F. Bataille, G. Flamant. Fluidization regimes of dense suspensions of Geldart group A fluidized particles in a high aspect ratio column. Chemical Engineering Sience, 2023
[3] R. Gueguen, S. Mer, A. Toutant, F. Bataille, G. Flamant. Effect of temperature on the hydrodynamics of a fluidized bed circulating in a long tube for a solar energy harvesting application. Chemical Engineering Sience, 2023
[4] F.Sabatier, R. Ansart, Z. Huili, J. Baeyens, O. Simonin. Experiments support simulations by the NEPTUNE_CFD code in an Upflow Bubbling Fluidized Bed reactor. Chemical Engineering Journal, 2020

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