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Over the last decade, as a consequence of the global decarbonization process, the interest towards green hydrogen production has drastically increased. In particular a substantial research effort has focused on the efficient and affordable production of carbon-free hydrogen production processes. In this context, the development of more efficient electrolyzers with low-cost electrode/electrocatalyst materials can play a key role. This work, investigates the fabrication of electrodes of nickel-zinc alloys with nanowires morphology cathode for alkaline electrolyzers. Electrodes are obtained by the simple method of template electrosynthesis that is also inexpensive and easily scalable. Through the analysis of the morphological and chemical composition of nanowires, it was found that the nanowires composition is dependent on the concentration of two metals in the deposition solution. Electrocatalytic tests were performed in 30% w/w potassium hydroxide aqueous solution at room temperature. In order to study the electrodes stability, mid-term galvanostatic test was also carried out. All electrochemical tests show that nanowires with about 44.4% of zinc have the best performances. Particularly, at −50 mAcm−2, these electrodes have an overpotential 50 mV lower than pure Ni nanowire. NiZn nanowires show also a good stability over time without noticeable signs of performance decay.

The fabrication and characterization of nickel-alloy electrodes for alkaline electrolysers is reported. Three different alloys (Ni–Co, Ni–Zn and Ni–W) at different composition were studied in order to determine the optimum condition. Nanostructured electrodes were obtained by template electrodeposition into a nanoporous membrane, starting from aqueous solution containing the two elements of the alloy at different concentrations. Composition of alloys can be tuned by electrolyte composition and also depends on the difference of the redox potential of elements and on the presence of complexing agents in deposition bath. Electrochemical and electrocatalytic tests, aimed at establishing the best alloy composition, were carried out for hydrogen evolution reaction. Then, test conducted at a constant current density in potassium hydroxide (30% w/w) aqueous solution were also performed. For all investigated alloys, very encouraging results were obtained and in particular Ni–Co alloys richer in Co showed the best performance.

The water distribution network (WDN) is subject to water leakages due to pipes breaking, which induces a wastage of water and overconsumption of power for pumps. Leakages are directly related to pressure in the pipes. To reduce leakages, pressure reducing valves (PRV) are installed in water distribution networks to reduce pressure in the pipes. However, pressure reduction induces a loss of energy which is wasted within the PRV. To recover a part of this energy, pressure reducing valves can be replaced by using pumps as turbines (PATs). Since head and flow rates are variable in the WDN, it is necessary to regulate the PAT, which does not function properly under variable upstream conditions. In this paper, the hydraulic regulation (HR) and hydraulic-electric regulation (HER) methods are studied in economic and energy production terms. A comparison between HR and HER is based on results from two real sites. The study is carried out using an innovative decision-support algorithm, which is described in detail. The results show that adding electrical regulation improves energy production, but the increase in installation costs makes the sites less economically viable.

Better understanding the properties of organic aerosols (OA) is attracting increasing attention because of the important role they play in climate change. The viscosity of OA has been shown to rang...

This paper investigates how and under which conditions the lamella of an impacting droplet is punctured by the presence of a small occlusion. Better understanding the conditions which lead to the rupture of the lamella is critical to produce defect free coating layers in the context of spray coating, for example. An analytical model based on surface energy analysis is proposed to obtain the critical thickness below which the liquid layer above the occlusion is unstable and lamella rupture occurs. Furthermore, we have developed a three dimensional multiphase lattice Boltzmann code to confirm the surface energy analysis and study the influence of key parameters like size of the occlusion, impact velocity and wettability of substrate on hole formation. Results show that a hole is more likely to appear as the diameter of the occlusion, the impact velocity, and the hydrophobicity of the surface increase.

International audience; Chemical enhanced oil recovery (EOR) is a successful method for increasing crude oil recovery. However, chemicals commonly used for enhanced oil recovery operations possess adverse biological impacts. To meet the legislative requirement and environmental protection demands, the performance of a highly biodegradable nonionic surfactant derived from tannic acid, a possible alternative, was evaluated using a microfluidic technology for the replacement of chemically synthesis surfactant by green chemistry products. Aqueous microdroplets containing the surfactant in crude oils were used for measurements of interfacial tension (IFT) reduction. The degree of interfacial tension reduction by sodium dodecyl sulfate (SDS), one of the most popular conventional surfactants, was also quantified for performance comparison. The potential of the biosurfactant for IFT reduction of light crude oil was superior to that of SDS. To evaluate the feasibility of the biosurfactant in improvement of recovery efficiency, surfactant-assisted flooding was tested under a random microfluidic network at the optimal concentrations, and the results were in good agreement with IFT reduction tests. The utilization of the polymer in a biosurfactant synthesis process effectively enhanced high sweep efficiency by decreasing a viscous fingering effect. The biosurfactant proved to be adequate and can sufficiently alleviate environmental concerns adopted by chemical flooding EOR.

In this work, nickel-iron alloy nanostructured electrodes obtained by template electrosynthesis method are investigated for both hydrogen and oxygen evolution reactions. Electrodes consist of nanowire arrays with high surface area that are able to ensures a high electrolytic activity. To obtain different alloy compositions, the concentration of the elements in the deposition baths is appropriately tuned. Results show that the composition of nanowires does not change linearly with the composition of deposition bath but are richer in Fe. Nanostructured electrodes are tested as both cathodes and anodes in 30 wt% KOH aqueous solution, at room temperature to determine the best alloy composition. In all electrochemical tests, the electrodes that performed best are those with iron content of 78.95 at%. Particularly, the results are very promising for the oxygen evolution reaction, with a Tafel's slope of 40 mV and a potential of 1.532 V vs. RHE after 6 h at constant current of 50 mA cm−2. Besides, preliminary tests in 0.5 M NaCl alkaline aqueous solution are also reported showing very promising results.

International audience; Granular activated carbon (GAC) was synthesized from Silver berry (Elaeagnus Angustifolia L.) seeds using zinc chloride as the activation agent. To optimize the operating parameters, the effects of the time and temperature of carbonization, impregnation ratio, and heating rate on the iodine number and yield of activated carbon were studied. Optimized parameters were impregnation ratio of 1:1, carbonization temperature of 500 degrees C, carbonization time of 1 hour, and heating rate of 5 degrees C/min. The GAC synthesized under optimized conditions was characterized by Nitrogen adsorption-desorption isotherms, SEM, EDX, XRD, FT-IR, Boehm titration, TG-TGA, and TG-IR. It was found that the synthesized GAC has a microporous structure with a BET surface area of 1109 m(2)/g, a micropores volume of 0.317 cm(3)/g, and an average pore diameter of 2.1 nm. The methylene blue (MB) dye was employed as a molecule model to evaluate the porosity and the adsorption capacity of the synthesized GAC. The results showed that the maximum adsorption capacity of MB and the percent portion of the surface area (S-MB/S-BET) were 120.48 mg/g and 30.62%, respectively. The experimental results reveal that the synthesized GAC can be used as a low-cost adsorbent for the removal of small and large environmental pollutants.

International audience; For the first time, an effort has been made to evaluate the charge transport properties of semiconducting natural rubber. Four different ratios of iodine-rubber composites are synthesised and tested for charge transport by current density-voltage characteristics (J-V) and impedance spectroscopy. The optimal doping ratio for best mobility value is identified, and the effect of injection barrier height on mobility is discussed. An attempt has also been made to correlate the density of states (DOS) with mobility and doping ratio. The transport properties of semiconducting natural rubber are compared with one of the most popular p-type material, Poly(3-hexylthio-phene-2,5-diyl) (P3HT) under the same ambience and experimental conditions to demonstrate its potential as a cost-effective and green alternative organic semiconductor.

Hydrogen storage is a promising technology for storage of renewable energy resources. Despite its high energy density potential, the development of hydrogen storage has been impeded, mainly due to its significant cost. Although its cost is governed mainly by electrical energy expense, especially for hydrogen produced with alkaline water electrolysis, it is also driven by the value of the cell tension. The most common means of electrolyzer improvement is the use of an electrocatalyst, which reduces the energy required for electrochemical reaction to take place. Another efficient means of electrolyzer improvement is to use the Computational Fluid Dynamics (CFD)-assisted design that allows the comprehension of the phenomena occurring in the electrolyzer and also the improvement in the electrolyzer’s efficiency. The designed two-phase hydrodynamics model of this study has been compared with the experimental results of velocity profiles measured using Laser Doppler Velocimetry (LDV) method. The simulated results were in good agreement with the experimental data in the literature. Under the good fit with experimental values, it is efficient to introduce a new physical bubble transfer phenomenon description called “bubble diffusion”.

Iodine doped natural rubber (NRI) is a novel and inexpensive organic semiconducting material. Its charge transport properties are comparable to those of widely used expensive organic semiconductor, poly(3-hexylthiophene-2,5-diyl). This report describes the efforts made to improve the charge transport properties of NRI material for the first time. For this, different concentrations of silver nanoparticles (Ag NPs) are synthesised and added to the semiconducting natural rubber. The charge transport mobility of NRI and NRI-Ag nanocomposites are investigated using impedance spectroscopy and discussed in the context of Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) levels of the material. It is investigated that NRI+25%Ag NPs shows the smallest electrochemical bandgap and enhanced mobility than all other composites. These results demonstrate the application potential of this inexpensive material in electronic industries.

Engaging black and minority-ethnic (BME) individuals in therapy and maintaining a positive therapeutic alliance can be a complex task, especially when challenging a family's core belief system. This study examines how therapists working within a specialist cultural service in London, UK were able to question a family's core cultural belief system whilst building and maintaining a strong therapeutic alliance. Video-assisted semi-structured interviews were carried out with two family members and their two therapists, and analysed using thematic analysis. The findings suggest that core beliefs can be effectively challenged within the context of a strong therapeutic alliance if topics are approached in a sensitive and respectful manner, by trusted therapists who have a degree of knowledge and awareness of their own cultural positioning, as well as an understanding of their clients’ culture. We propose that engaging with culture in this way can strengthen alliance and facilitate positive change.

Owing to the progressive abandoning of the fossil fuels and the increase of atmospheric CO2 concentration, the use of renewable energies is strongly encouraged. The hydrogen economy provides a very interesting scenario. In fact, hydrogen is a valuable energy carrier and can act as a storage medium as well to balance the discontinuity of the renewable sources. In order to exploit the potential of hydrogen it must be made available in adequate quantities and at an affordable price. Both goals can be potentially achieved through the electrochemical water splitting, which is an environmentally friendly process as well as the electrons and water are the only reagents. However, these devices still require a lot of research to reduce costs and increase efficiency. An approach to improve their performance is based on nanostructured electrodes characterized by high electrocatalytic activity. In this work, we show that by using template electrosynthesis it is possible to fabricate Ni nanowires featuring a very high surface area. In particular, we found that water-alkaline electrolyzers with Ni nanowires electrodes covered by different electrocatalyst have good and stable performance at room temperature as well. Besides, the results concern nickel-cobalt nanowires electrodes for both hydrogen and oxygen evolution reaction will be presented and discussed. Finally, preliminary tests concerning the use of Ni foam differently functionalized will be shown. For each electrode, electrochemical and electrocatalytic tests aimed to establishing the performance of the electrolyzers were carried out. Long term amperostatic test carried out in aqueous solution of KOH will be reported as well.

This article presents an exhaustive review of the transport properties necessary for the multiphysics modelling of alkaline water electrolyzer. This article provides experimental data and the correlations needed to calculate thermos-physical properties such as electrical conductivity, density, viscosity, heat capacity, heat and mass transfer diffusion coefficients as a function of temperature and electrolyte mass fraction for two classical alkaline electrolytes (KOH, NaOH). Thus, the different boundary layers growing on the electrodes can be calculated with precision. Different interpolation models from various authors are compared to raw experimental data. The goal of this article is to give to the modeler the correlations needed for the simulation of alkaline water electrolysis.

Hydrogen is an excellent energy source for long-term storage and free of greenhouse gases. However, its high production cost remains an obstacle to its advancement. The two main parameters contributing to the high cost include the cost of electricity and the cost of initial financial investment. It is possible to reduce the latter by the optimization of system design and operation conditions, allowing the reduction of the cell voltage. Because the CAPEX (initial cost divided by total hydrogen production of the electrolyzer) decreases according to current density but the OPEX (operating cost depending on the cell voltage) increases depending on the current density, there exists an optimal current density. In this paper, a genetic algorithm has been developed to find the optimal evolution parameters and to determine an optimum electrolyzer design. The optimal current density has been increased by 10% and the hydrogen cost has been decreased by 1%.

The presented work is a multiphysics calculation using Ansys-Fluent® CFD modelling of a hydrodynamic alkaline water electrolyzer. This work will start with an exhaustive review of the transport properties necessary for the multiphysics modelling of alkaline water electrolyzer. A recently published article provides experimental data and the correlations needed to calculate thermo-physical properties such as electrical conductivity, density, viscosity, heat capacity, heat and mass transfer diffusion coefficients as a function of temperature and electrolyte mass fraction for two classical alkaline electrolytes (KOH, NaOH). Different interpolation models from various authors are compared to raw experimental data. The goal of this work was to give to the modeler the correlations needed for the simulation of alkaline water electrolysis. Thus, the two electrodes two-phase boundary layers can be calculated with precision. Calculations under discrete phase modelling (DPM) and Euler-Euler hypothesis have been performed and are presented. Figure 1

Recent advancements in microelectromechanical systems (MEMS) have required state-of-the-art techniques that provide accurate information of physical parameters such as fluid velocities and temperatures, at small scales, to fully characterize fluid flows in these devices. Especially it is difficult to measure temperature fields at microscale using conventional methods due to the limitation of spatial resolution in these techniques. In this paper, we present a comprehensive review of various advanced microscale thermometry techniques for measurements of bulk fluid or wall surface temperature fields. Differing from earlier publications, this review particularly focuses on categorizing the thermometry techniques based on how they measure temperature information at the microscale, i.e., either contact or noncontact methods. The paper presents details of measurement principles for each thermometry technique and includes a broad range of their applications. For the contact-based thermometry, the most recent fabrication and measurement results with micro-thermocouples are introduced, followed by discussions for scanning temperature probes and atomic force microscope (AFM) temperature probes. On the other hand, noncontact-based thermometry techniques are broadly summarized, including optical thermometry, liquid crystal thermometry, infrared thermometry, and Raman spectroscopy. Strengths and weaknesses of each technique compared to other approaches, with information of spatial, temporal, and temperature resolutions are introduced and discussed. This review will provide a general guideline for readers regarding the advantages and disadvantages of the most recent microscale thermometry techniques considering key requirements such as tool availability, system limitations, and temperature resolution. Display Omitted A comprehensive review for microscale thermometry techniques is provided.Contact-based thermometry is expensive and provides discrete measurements.Noncontact-based thermometry provides two dimensional temperature fields.Advantages and disadvantages of various thermometry methods are provided.

International audience; The effectiveness factor, E f, (fraction of the electrode surface that participates effectively in the investigated reaction) of fast (Fe3+/Fe2+), moderate (Cl2/Cl−) and slow (O2/H2O) redox couples has been estimated using IrO2-based electrodes with different loading. The method of choice was linear sweep voltammetry (measurement of the anodic peak current) for the Fe3+/Fe2+ redox couple and steady-state polarization (determination of the exchange current) for the O2 and Cl2 evolution reactions. The results have shown that the effectiveness factor depends strongly on the kinetics of the investigated redox reaction. For the Fe3+/Fe2+ redox couple, effectiveness factors close to zero (max 4%) have been obtained contrary to the O2 evolution reaction where effectiveness factors close to 100% can be achieved, all being independent of IrO2 loading. For the Cl2 evolution reaction, intermediate values of the effectiveness factor have been found and they decrease strongly, from 100% down to about 60%, with increasing loading.

The effectiveness factor; E f , defined as the fraction of the surface that participates effectively in a given reaction, is an important parameter when operating three-dimensional (3D) electrodes. The rotating disk electrode (RDE) technique with the Fe3+/Fe2+ redox couple as a probe reaction has been used for the evaluation of the effectiveness factor of 3D Ti/IrO2 electrodes with different IrO2 loading. For this purpose, steady-state polarization measurements using Ti/IrO2 rotating disk electrodes in 0.5 M Fe3+/Fe2+ in 1 M HCl were carried out under well-defined hydrodynamic conditions. The low-field approximation relation has been used for the estimation of the exchange current densities j 0, of the Fe3+/Fe2+ redox couple. It was found for this redox couple that the effectiveness factor is very low (

This chapter aims to describe and reflect upon clinical work with Pakistani families in the context of court mandated parenting assessments in childcare proceedings. The Marlborough Family Service is a child and adolescent mental health service combined with an adult psychotherapy service, based in central London and part of the National Health Service (NHS). It consists of a multi-disciplinary team with a focus on systemic approaches to psychotherapy and a commitment to engaging with community groups within its catchment area. The chapter argues that accessing culture is an emotional process which requires a level of reflective practice, emotional engagement, and a reworking of cultural themes by both the clinicians and the family. Referrals are received in the form of a joint letter of instruction that provides a brief summary of the local authority's concerns and a list of questions which the parties have agreed need to be assessed.

During two-phase electrolysis for the production of oxygen and hydrogen, it is generally observed production of bubbles at one or two electrodes which indicates a change in electrical and hydrodynamic properties of the electrolyser. In the presence of gravity, the production of bubbles at the electrodes induces a macro-convection in the electrolyser. This leads to a variable distribution of the bubbles void fraction and of the current density j at the electrodes. The absence of gravity eliminates the natural convection and by the same frictional forces. The electrolysis is performed using a potentiostat. The formation of gas bubbles at the anode is observed by two cameras. The aim of this study is to predict the evolution laws of the electrochemical cell voltage and of the bubble diameter during a two-phase electrolysis depending on the three presently explored inputs: current density j, gravity G and concentration C.

Battery ageing and performance evolution prediction is one of the energy management key. The use of lead acid batteries is always strong despite its weight and the constant increasing, of new battery materials and technologies. The lead acid batteries are mainly used to start car engine or as primary energy source for forklift or pallet trucks. Another application is the storage of electrical energy produces by intermittent energy sources like photovoltaic, wind or tidal powers. Multiple factors influence lead acid batteries ageing depending of the type of batteries technology (vented or opened and VRLAB or sealed) and the kind of use. We focus our experimental study on four of them: the number of ageing cycles (1), the operating current (2), the temperature (3) and the use of electrolyte additives, containing EDTA (4). Factors are investigated on two levels (Table 1). Figure 1

International audience; During two-phase electrolysis processes, for example for hydrogen production, there are bubbles which are created at electrodes. This implies a great vertical motion source in the normal earth gravity field and then a quite important natural two-phase convection. All other fields are then affected. Heat, mass and electricity transfers are modified due to both bubbles screening (at surface and in volume) and to bubbles transport promotion. Many numerical modeling for two-phase processes such as kerosene pulverization in engines or coal combustion sciences have shown the difficulties of these multi-physics processes. Both particles and reactor scales must be considered according with a strong coupling modeling. In these processes the particles injection is "in the flow". In boiling or electrolysis processes, a new difficulty is added: particles birth or injection is strongly coupled to the local flow properties and leads to a complex boundary condition at surfaces. Electrical and electrochemical properties and processes are disturbed. This disturbance can lead to the modification of the local current density and to anode effects for example. There is few works concerning the local modelling of electrochemical processes during a two-phase electrolysis process. There are also few local experimental measurements in term of chemical composition, temperature or current density which will allow the numerical calculations validation. The present work shows the started numerical modeling strategy and the first results, both experimental and numerical obtained.

Aluminium is produced according with the Hall-Heroult process. At the cathode, AlxFy species are reduced and lead to liquid aluminium. At the consumable carbon anode, AlxOzFy species are oxidized to lead to carbon dioxide bubbles evolving and not O2 bubbles because of the carbon anode consumption. During this complex electrolyte two- phase electrolysis, it is difficult to model the current distribution and to optimize the process. The flow is the result of the magneto-hydrodynamic phenomena induced by the strong imposed currents and of the bubbles evolving. The reactivity and species concentration distribution are difficult to model: the molten salt chemistry is few developped compared with the aqueous chemistry. The mass, heat and charge transport are also stongly difficult to model, because of the created bubbles which imply transfer properties disturbance. Bubbles are motion sources for the electrolysis cell flow, hydrodynamic properties are strongly coupled with species transport and electrical performances. Bubbles presence modifies these global and local properties: the electrolysis cell and the current density distribution are modified. The goal of this proposition is to present the electrochemical engineering modelling of the Hall-Heroult two-phase electrolysis properties in the inter electrode interval. The numerical simulations are performed from both the chemistry and two-phase hydrodynamic point of views. Chemical calculations are first performed to describe dissolved gas species and bubble nucleation and growth. In a second step, a simple Euler-Lagrange two-phase model is presented to calculate hydrodynamic properties in

During two-phase electrolysis for hydrogen, aluminium or fluor production, there are bubbles which are created at electrodes which imply a great hydrodynamic acceleration in the normal earthgravity field and then a quite important electrical properties and electrochemical processes disturbance. This disturbance can lead to the modification of the local current density and to anode effects for example. There is few works concerning the local modelling of electrochemical processes during a two-phase electrolysis process. There are also few local experimental measurements in term of chemical composition, temperature or current density which will allow the numerical calculations validation. Nevertheless, effects like the anode effect, particularly expensive on the point of the process efficiency, should need a better understanding.

Electrochemical discharge phenomenon, as well known as plasma electrolysis, electrode effects or contact glow discharge electrolysis, was first described in literature more than 150 years ago. Today this effect is studied only in quite specialised applications. This was not always the case. During the 19th century and early 20th century, electrochemical discharges were intensively studied and a broad spectrum of applications, ranging from X-ray imaging to wireless telegraphy, was developed. This communication retraces this early history of electrochemical discharges by highlighting the interesting electrochemical effects and applications linked to them. The paper ends by shortly mentioning today's applications of electrochemical discharges which are in the field of micro-machining, surface engineering, nanotechnology and waste water treatment.

Chemical bath electro deposition process is used in many industrial applications to obtain a thin layer material on a target surface. Numerous metal, magnetic or semi-conductor materials, such as oxide, chalcogenure or alloys are obtained in electrochemical cells at laboratory scale. Some of these materials are interesting to be produced at industrial scale, for example for electronics, fuel cells or photovoltaic applications. In industrial electrochemical cells, dimension is larger and many parameters such as hydrodynamics or electro active specie transport are heterogeneous. There are many industrial electrochemical techniques in which the electrode moves with respect to the solution. These systems, like the rotating electrodes, are called hydrodynamic electrochemical processes. It is also interesting to notice that micronic structure, such as roughness, columnar structure or porosity of material deposit is local flow dependent. Then, it appears, that the material deposit composition and structural quality need integrated information from the micronic scale to the industrial scale, using, of course, the laboratory scale measurements. The aim of the present work is to model and to numerically simulate the hydrodynamics, electrochemical and chemical coupled phenomena, which are occurring during the chemical bath electro deposition process for laboratory and industrial configurations. Experimental measurements obtained at laboratory scale with zinc oxide thin layer deposit are used to identify transport or kinetic data input which are conserved during the scale-up. Flow and chemical species concentration field properties are calculated in the working electrode surface vicinity taking into account homogeneous and heterogeneous reactions. The numerical method used is the finite volume method. In addition, using a Monte Carlo method, micronic information is calculated such as the roughness and the porosity of the thin layer material obtained.

This paper will describe a piece of social work practice from a systemic perspective before exploring in more depth the contribution of psychoanalysis to the relationship between professionals and service users. It will focus on the object‐relation school and in particular Melanie Klein's concepts of projective identification and splitting, together with ideas from Bion about containment. It will consider how these concepts, which have been developed to make sense of the inner world of infants, can be applied to the wider professional system and to organisations. It will then consider attempts at integrating systemic and psychodynamic approaches, and explore whether these two very different models which have developed in opposition to each other can be integrated to provide additional layers of meaning to the family's position within the child protection system and the legal framework.

This paper discusses the use of systemic ideas in shaping and informing an approach to teaching social work students on a qualifying social work programme in a UK university setting. The context of contemporary social work training and the primacy it gives to practice experience and service user and carers' perspectives will be explained, in part to remind us that service users want their practitioners to be competent, even ‘expert’ at using relationship in their work. From here an argument will be developed for revisiting systemic ideas in social work, the suggestion being that systemic thinking can actively promote a relationship‐based approach suited to the modern context of practice that seeks to move beyond a potentially limiting, ‘procedure‐led’ or ‘surface’ approach. We will give an outline of and rationale for the curriculum followed by the module in question and will suggest that its focus on systemic approaches in dialogue with other theory perspectives is a creative one; one which enables an ex...

The rotating cylinder electrode configuration is one of the most used electrochemical configurations for electrochemical processes study. It is often used with turbulent flow regime for industrial application such as intensive corrosion or electro deposition processes. It can also be used for laminar regimes but in this case it can appear superposition between forced convection and natural free convection. This natural free convection is generally due to density gradient from electrode to bulk, due to electro deposition or to evolving bubbles. The hydrodynamic regime is then said mixed. There is few knowledge concerning the mixed hydrodynamic and the main goal of the present work is to show the qualitative and quantitative effects and differences between purely forced convective flow and purely free natural flow.

The hydrodynamics of a rotating cylinder electrode were modeled to predict tertiary current distributions during electrodeposition of copper from acidic sulfate media, and to evaluate the effects of the resulting density gradients close to the electrode. Assuming no such density variations, then predictions of transport-limited current densities were in good agreement with Mizushina's empirical law and with LévÊque's theoretical description, but not with measured values. Assuming a linear density variation with copper concentration, predictions of concentration profiles agreed to within 3 % of experimentally measured limiting current densities at the rotating cylinder electrode. For solution compositions relevant to copper electrowinning, a diffusion coefficient for cupric ions of 1.2x10-9 m2/s at 45 oC, was inferred by solving the continuity, Navier-Stokes and mass balance equations with Fluent® computational fluid dynamics software.

The main purpose of this work is to establish the macroscopic impact of solid oxide thin layer electrolytes, which are proposed to reduce SOFC (solid oxide fuel cell) operating temperature. This work deals with the planar technology configuration. Fuel and oxidant flow through numerous small tubes. The electrical performance analysis of such an elementary fuel cell consist in establishing the relation between tension and current and the influence of parameters such as tubes dimensions, thickness and electrical conductivity of thin layers and fuel used. This study uses fundamental laws of species and energy conservation, as well as electrochemical and electrical laws. Stack performance calculation is mainly a thermal and electrical calculation. This is done here by using Fluent® code calculations and C programming. Particular attention is given to the thermal properties, because of the importance of the dilatation problem in SOFC technology.

During two-phase water electrolysis production of bubbles at one or both electrodes is observed. This leads to a change in the electrolyser electrical and hydrodynamic properties. When gravity is present, the production of bubbles at the electrodes induces a macro-convection in the electrolyser. This leads to a local distribution of the bubbles determining the local gas void fraction and current density at the electrodes. The absence of gravity eliminates the natural convection and buoyancy forces and consequently the frictional forces. It is generally difficult to estimate the quantitative influence of each of these single phenomena due to strong coupling. In the present work, alkaline water electrolysis is performed. The formation of gas bubbles at the anode is observed using four cameras. The aim of this study is to establish the quantitative evolution laws for the electrochemical cell potential, the bubble diameter and population density during alkaline (NaOH) two-phase electrolysis in function of the two explored inputs current density and gravity.