Etude du transfert de chaleur en canaux millimétriques de type zigzag pour le développement et l'extrapolation de réacteurs-échangeurs compacts

Cette thèse porte sur la caractérisation thermique de réacteurs échangeurs de chaleur compacts. Le but est de mesurer des coefficients de transfert thermique dans ces appareils et de comprendre l'effet d'intensification du transfert thermique lié à leur géométrie. Des prototypes de réacteurs échangeurs sont utilisés, composés de trois plaques : deux plaques dites "procédé" et "utilité" où sont gravés des canaux millimétriques droits ou en zigzag de section carrée, séparées par une plaque en aluminium. Le coefficient de transfert de chaleur est déterminé expérimentalement et numériquement. L'influence de la géométrie du canal, des propriétés des fluides et des débits sur le transfert de chaleur est discutée. Une méthode expérimentale de mesure de la température locale est mise en œuvre, basée sur de la fluorescence induite par laser. Enfin, l'effet d'un changement d'échelle de ces appareils pour la mise en œuvre de réactions compétitives exothermiques est étudié.This thesis is about the thermal characterization of compact heat-exchanger (HEX) reactors. The objective is to measure heat transfer coefficients in these devices and understand the effect of intensification of heat transfer related to their geometry. The compact HEX reactor prototypes used are composed of three plates: two plates called process plate and utility plate where millimetric square straight or zigzag channels are engraved, separated by an aluminum plate. The heat transfer coefficient is measured experimentally and numerically. The influence of channel geometry, fluid properties and flow rates on heat transfer is discussed. An experimental method for measuring the local temperature is implemented, based on laser-induced fluorescence. Finally, the effect of scale-up of these devices for the implementation of competitive exothermic reactions is studied

Numerical study of heat transfer in square millimetric zigzag channels in the laminar flow regime

The present work deals with the simulation of heat transfer in zigzag millimetric channels with square crosssection of 2mm width in the laminar flow regime. They consist of periodic zigzag units composed of straight sections and 90° bends with a curvature radius of 1.5 mm. The influences of fluid velocity and straight section length on the thermo-hydraulic performances are investigated. The results showed that by increasing the flow velocity or decreasing the straight section length between two bends, a transition from periodic flow to nonperiodic flow can be observed. A thermo-hydraulic performance factor based on heat transfer enhancement and pressure drop penalty compared with a straight channel is then discussed. It is observed that the ratio of the Nusselt number in the zigzag channels to that in the straight channel is always higher than one. This ratio increases with increasing Reynolds number and values up to 6.4 are reached in the cases studied (Pr=6.13). When the pressure drop penalty is considered in the performance factor, an enhancement is still observed with a factor up to 2.5. It is shown that non-periodic flow is not particularly interesting in terms of thermo-hydraulic performance compared with periodic flow

Magnetic-coupled electronic landscape in bilayer-distorted titanium-based kagome metals

Quantum materials whose atoms are arranged on a lattice of corner-sharing triangles, $\textit{i.e.}$, the kagome lattice, have recently emerged as a captivating platform for investigating exotic correlated and topological electronic phenomena. Here, we combine ultra-low temperature angle-resolved photoemission spectroscopy (ARPES) with scanning tunneling microscopy and density functional theory calculations to reveal the fascinating electronic structure of the bilayer-distorted kagome material $\textit{Ln}$Ti${_3}$Bi${_4}$, where $\textit{Ln}$ stands for Nd and Yb. Distinct from other kagome materials, $\textit{Ln}$Ti${_3}$Bi${_4}$ exhibits two-fold, rather than six-fold, symmetries, stemming from the distorted kagome lattice, which leads to a unique electronic structure. Combining experiment and theory we map out the electronic structure and discover double flat bands as well as multiple van Hove singularities (VHSs), with one VHS exhibiting higher-order characteristics near the Fermi level. Notably, in the magnetic version NdTi${_3}$Bi${_4}$, the ultra-low base temperature ARPES measurements unveil an unconventional band splitting in the band dispersions which is induced by the ferromagnetic ordering. These findings reveal the potential of bilayer-distorted kagome metals $\textit{Ln}$Ti${_3}$Bi${_4}$ as a promising platform for exploring novel emergent phases of matter at the intersection of strong correlation and magnetism

Etude du transfert de chaleur en canaux millimétriques de type zigzag pour le développement et l'extrapolation de réacteurs-échangeurs compacts

This thesis is about the thermal characterization of compact heat-exchanger (HEX) reactors. The objective is to measure heat transfer coefficients in these devices and understand the effect of intensification of heat transfer related to their geometry. The compact HEX reactor prototypes used are composed of three plates: two plates called process plate and utility plate where millimetric square straight or zigzag channels are engraved, separated by an aluminum plate. The heat transfer coefficient is measured experimentally and numerically. The influence of channel geometry, fluid properties and flow rates on heat transfer is discussed. An experimental method for measuring the local temperature is implemented, based on laser-induced fluorescence. Finally, the effect of scale-up of these devices for the implementation of competitive exothermic reactions is studied.Cette thèse porte sur la caractérisation thermique de réacteurs échangeurs de chaleur compacts. Le but est de mesurer des coefficients de transfert thermique dans ces appareils et de comprendre l’effet d’intensification du transfert thermique lié à leur géométrie. Des prototypes de réacteurs échangeurs sont utilisés, composés de trois plaques : deux plaques dites « procédé » et « utilité » où sont gravés des canaux millimétriques droits ou en zigzag de section carrée, séparées par une plaque en aluminium. Le coefficient de transfert de chaleur est déterminé expérimentalement et numériquement. L’influence de la géométrie du canal, des propriétés des fluides et des débits sur le transfert de chaleur est discutée. Une méthode expérimentale de mesure de la température locale est mise en œuvre, basée sur de la fluorescence induite par laser. Enfin, l’effet d’un changement d’échelle de ces appareils pour la mise en œuvre de réactions compétitives exothermiques est étudié

Heat transfer study of millimetric zigzag channels for the development and scale-up of compact heat-exchangers reactors

Cette thèse porte sur la caractérisation thermique de réacteurs échangeurs de chaleur compacts. Le but est de mesurer des coefficients de transfert thermique dans ces appareils et de comprendre l’effet d’intensification du transfert thermique lié à leur géométrie. Des prototypes de réacteurs échangeurs sont utilisés, composés de trois plaques : deux plaques dites « procédé » et « utilité » où sont gravés des canaux millimétriques droits ou en zigzag de section carrée, séparées par une plaque en aluminium. Le coefficient de transfert de chaleur est déterminé expérimentalement et numériquement. L’influence de la géométrie du canal, des propriétés des fluides et des débits sur le transfert de chaleur est discutée. Une méthode expérimentale de mesure de la température locale est mise en œuvre, basée sur de la fluorescence induite par laser. Enfin, l’effet d’un changement d’échelle de ces appareils pour la mise en œuvre de réactions compétitives exothermiques est étudié.This thesis is about the thermal characterization of compact heat-exchanger (HEX) reactors. The objective is to measure heat transfer coefficients in these devices and understand the effect of intensification of heat transfer related to their geometry. The compact HEX reactor prototypes used are composed of three plates: two plates called process plate and utility plate where millimetric square straight or zigzag channels are engraved, separated by an aluminum plate. The heat transfer coefficient is measured experimentally and numerically. The influence of channel geometry, fluid properties and flow rates on heat transfer is discussed. An experimental method for measuring the local temperature is implemented, based on laser-induced fluorescence. Finally, the effect of scale-up of these devices for the implementation of competitive exothermic reactions is studied

An Improved Quantum-Behaved Particle Swarm Optimization Algorithm Combined with Reinforcement Learning for AUV Path Planning

In order to solve the problem of fast path planning and effective obstacle avoidance for autonomous underwater vehicles (AUVs) in two-dimensional underwater environment, a path planning algorithm based on deep Q-network and Quantum particle swarm optimization (DQN-QPSO) was proposed. Five actions are defined first: normal, exploration, particle explode, random mutation, and fine-tuning operation. After that, the five actions are selected by DQN decision thinking, and the position information of particles is dynamically updated in each iteration according to the selected actions. Finally, considering the complexity of underwater environment, the fitness function is designed, and the route length, deflection angle, and the influence of ocean current are considered comprehensively, so that the algorithm can find the solution path with the shortest energy consumption in underwater environment. Experimental results show that DQN-QPSO algorithm is an effective algorithm, and its performance is better than traditional methods

A computational analysis of ATP binding of SV40 large tumor antigen helicase motor.

Simian virus 40 large tumor antigen (LTag) is an efficient helicase motor that unwinds and translocates DNA. The DNA unwinding and translocation of LTag is powered by ATP binding and hydrolysis at the nucleotide pocket between two adjacent subunits of an LTag hexamer. Based on the set of high-resolution hexameric structures of LTag helicase in different nucleotide binding states, we simulated a conformational transition pathway of the ATP binding process using the targeted molecular dynamics method and calculated the corresponding energy profile using the linear response approximation (LRA) version of the semi-macroscopic Protein Dipoles Langevin Dipoles method (PDLD/S). The simulation results suggest a three-step process for the ATP binding from the initial interaction to the final tight binding at the nucleotide pocket, in which ATP is eventually "locked" by three pairs of charge-charge interactions across the pocket. Such a "cross-locking" ATP binding process is similar to the binding zipper model reported for the F1-ATPase hexameric motor. The simulation also shows a transition mechanism of Mg2+ coordination to form the Mg-ATP complex during ATP binding, which is accompanied by the large conformational changes of LTag. This simulation study of the ATP binding process to an LTag and the accompanying conformational changes in the context of a hexamer leads to a refined cooperative iris model that has been proposed previously

Improved Model-free H? Control for Batch Processes via off-policy 2D Game Q-Learning

International Journal of Control96102447-246