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Ben-Abdallah P.,CNRS Nantes Thermocinetique Lab | Joulain K.,CNRS Pprime Institute | Pryamikov A.,CNRS Pprime Institute
Applied Physics Letters | Year: 2010

We theoretically investigate the nonradiative heat transfer between two photonic crystals separated by a small gap in nonequilibrium thermal situation. We predict that the surface Bloch states coupling supported by these media can make heat exchanges larger than those measured at the same separation distance between two massive homogeneous materials made with the elementary components of photonic crystals. These results could find broad applications in near-field technologies. © 2010 American Institute of Physics.

Abdulhay B.,CNRS Nantes Thermocinetique Lab | Abdulhay B.,ArcelorMittal | Bourouga B.,CNRS Nantes Thermocinetique Lab | Dessain C.,ArcelorMittal
Applied Thermal Engineering | Year: 2011

The objective of the present article is the thermal conductance estimation to improve the Usibor 1500P® blank cooling during the hot stamping process. An experimental device was designed and developed to estimate the thermal contact resistance at the part/tool interface. The designed stamping tool is composed of a die and a punch made in Z160CDV12 steel and presenting an omega shape. Samples and tools are thermally instrumented with thermocouples type K sheathed with silky glass, forming heat-flux meters in the most interesting locations in the tools. Reproducibility tests showed a good repeatability of recorded and estimated parameters with a mean dispersion less than 5%; it was noticed that a re-heating of the cooled part due to its microstructure transformation occurring systematically at 400 °C. At the surface boundary of the part, thermal conductances are calculated using convective/radiation modeling of both phases: approach and forming. At the contact interfaces, thermal contact resistances RC are estimated experimentally through a non-linear 1D inverse technique founded on sequential method of Beck. Results have been established as correlation of type: R C = f(P) to be used for numerical simulation. © 2010 Published by Elsevier Ltd. All rights reserved.

Josset C.,CNRS Nantes Thermocinetique Lab | Babarit A.,CNRS Laboratory for Hydrodynamics, Energetics & Atmospheric Environment | Clement A.H.,CNRS Laboratory for Hydrodynamics, Energetics & Atmospheric Environment
Proceedings of the Institution of Mechanical Engineers Part M: Journal of Engineering for the Maritime Environment | Year: 2015

This paper describes a numerical wave-to-wire model of the second-generation wave energy converter called SEAREV. Governing equations are given in the time domain for the motion of the masses involved in the device and for the hydraulic power take-off (PTO) used to convert the motion into electricity. The hydrodynamic forces are derived using the standard linear potential theory. The memory term in the radiation force is replaced by additional states using the Prony method in order to change the equation of motion into the ordinary differential equation form. The PTO is composed of hydraulic rams, an accumulator, and a hydraulic generator, which delivers electricity when there is enough energy stored in the accumulator.Using the MATLAB Simulink tool, the equation of motion is solved to simulate the full device (including the power take-off) from the incident wave to the electricity delivered to the grid. Simulation results are presented in the paper and comparisons are made with a simpler PTO: a linear damper. They show that the torque applied to the hydraulic PTO must exceed a threshold to start absorbing energy, unlike the linear damping model. They also show that the power production can be very discontinuous, depending on the level of the incident wave power. This is due to the fact that the generator considered can transform the energy stored in the accumulator faster than the energy transmitted by the rams into the accumulator. It could therefore be interesting to use several generators to adapt the electrical energy production to the level of incident wave power, or a generator that could work efficiently at part load in order to achieve continuous energy production. © 2007 Institution of Mechanical Engineers.

Joulain K.,University of Poitiers | Ezzahri Y.,University of Poitiers | Drevillon J.,University of Poitiers | Rousseau B.,CNRS Nantes Thermocinetique Lab | De Sousa Meneses D.,French National Center for Scientific Research
Optics Express | Year: 2015

By means of fluctuational electrodynamics, we calculate radiative heat flux between two planar materials respectively made of SiC and SiO2. More specifically, we focus on a first (direct) situation where one of the two materials (for example SiC) is at ambient temperature whereas the second material is at a higher one, then we study a second (reverse) situation where the material temperatures are inverted. When the two fluxes corresponding to the two situations are different, the materials are said to exhibit thermal rectification, a property with potential applications in thermal regulation. Rectification variations with temperature and separation distance are reported here. Calculations are performed using material optical data experimentally determined by Fourier transform emission spectrometry of heated materials between ambient temperature (around 300 K) and 1480 K. It is shown that rectification is much more important in the near-field domain, i.e. at separation distances smaller than the thermal wavelength. In addition, we see that the larger is the temperature difference, the larger is rectification. Large rectification is finally interpreted due to a weakening of the SiC surface polariton when temperature increases, a weakening which affects much less SiO2 resonances. © 2015 Optical Society of America.

Some S.C.,LUNAM University IFSTTAR | Gaudefroy V.,LUNAM University IFSTTAR | Delaunay D.,CNRS Nantes Thermocinetique Lab
International Journal of Heat and Mass Transfer | Year: 2012

Asphalt pavements are obtained after mixing aggregates and bitumen both preheated in a temperature range between 100 °C and 160 °C. The manufacturing temperatures are important to ensure good bitumen and aggregates bonding. However, the accurate evaluation of the bonding quality remains a challenge. A setup has been used to quantify the bonding quality between hot bitumen and granular substrate.The method is based on the determination of the thermal contact resistance (TCR) when hot bitumen is putted into contact with granular substrate. This TCR is assessed from solving inverse heat conduction problem and is interpreted as a bonding quality indicator. Results prove that the increase of component temperatures induces better bonding between bitumen and the substrate. © 2012 Elsevier Ltd. All rights reserved.

Oliveux G.,CNRS Nantes Thermocinetique Lab | Bailleul J.-L.,CNRS Nantes Thermocinetique Lab | Salle E.L.G.L.,Institute Catholique Des Arts Et Metiers Of Nantes Icam
Composites Part A: Applied Science and Manufacturing | Year: 2012

A hydrolysis process is applied to degrade an unsaturated polyester resin based on DCPD (dicyclopentadiene) and crosslinked with styrene, as the matrix of a composite material reinforced with long glass fibres. Subcritical conditions of water (200 °C < temperature < 374 °C and pressure < 221bars) were chosen regarding the involved chemistry for the case of simple esters. Several experiments were realised to measure the effects of the process parameters on the efficiency of hydrolysis, on the quality of the recovered fibres and finally on the nature of the recovered organic products. A washing of the fibres is necessary and appears to be an important step of the process realised in batch conditions. The identification of the recovered organic products indicates that monomers of the resin are obtained but also that secondary reactions occur during the hydrolysis process. © 2012 Elsevier Ltd. All rights reserved.

Burghelea T.I.,CNRS Nantes Thermocinetique Lab | Stary Z.,Friedrich - Alexander - University, Erlangen - Nuremberg | Munstedt H.,Friedrich - Alexander - University, Erlangen - Nuremberg
Journal of Non-Newtonian Fluid Mechanics | Year: 2011

An experimental investigation of the viscosity overshoot phenomenon observed during uniaxial extension of a low density polyethylene is presented. For this purpose, traditional integral viscosity measurements on a Münstedt-type extensional rheometer are combined with local measurements based on the in-situ visualization of the sample under extension. For elongational experiments at constant strain rates within a wide range of Weissenberg numbers (Wi), three distinct deformation regimes are identified. Corresponding to low values of Wi (regime I), the tensile stress displays a broad maximum, but such maximum is observed with various polymeric materials deformed at low rates and it should not be confused with the " viscosity overshoot" phenomenon. Corresponding to intermediate values of Wi (regime II), a local maximum of the integral extensional viscosity is systematically observed. Moreover, within this regime, a strong discrepancy between integral measurements and the space average of the local elongational viscosity is observed which indicates large deviations from an ideal uniaxial deformation process. Images of samples within this regime reinforce this finding by showing that, corresponding to the maximum of the integral viscosity, secondary necks develop along the sample. The emergence of a maximum of the integral elongational viscosity is, thus, related to the distinct inhomogeneity of deformation states and most probably not to the rheological properties of the material. In the fast stretching limit (high Wi, regime III), the overall geometric uniformity of the sample is well preserved, no secondary necks are observed and both the integral and the space averaged transient elongational viscosity show no maximum. A detailed but yet incomplete comparison of the experimental findings with results from the literature is presented and several open questions are stated. © 2011 Elsevier B.V.

Ho T.D.,Rennes Institute of Physics | Valance A.,Rennes Institute of Physics | Dupont P.,INSA Rennes | Ould El Moctar A.,CNRS Nantes Thermocinetique Lab
Physical Review Letters | Year: 2011

We report on wind tunnel measurements on saltating particles in a turbulent boundary layer and provide evidence that over an erodible bed the particle velocity in the saltation layer and the saltation length are almost invariant with the wind strength, whereas over a nonerodible bed these quantities vary significantly with the air friction speed. It results that the particle transport rate over an erodible bed does not exhibit a cubic dependence with the air friction speed, as predicted by Bagnold, but a quadratic one. This contrasts with saltation over a nonerodible bed where the cubic Bagnold scaling holds. Our findings emphasize the crucial role of the boundary conditions at the bed and may have important practical consequences for aeolian sand transport in a natural environment. © 2011 American Physical Society.

Garnier B.,CNRS Nantes Thermocinetique Lab
17th International Congress of Metrology, CIM 2015 | Year: 2015

Temperature measurements on surfaces or inside mediums are often performed using resistance temperature detectors (RTD) or thermocouple wires. The wire thermocouples are preferred for transient measurement because they are relatively less intrusive than other types of sensors and have low response times until a few tens of milliseconds. The smallest diameters of thermocouple wires are of the order of 12 μm, however with such a size they are very difficult to implement. In addition, there are many situations in which theirs dimensions are still too large as in microsystems such as OLED, organic solar cell, hybrid thermoelectric devices and also microsensors. Thus, it is very advantageous to use temperature sensors as thin films where the thickness is typically of the order of 100nm and also thick film (on the order of a few micrometers). In this communication, we present successively: i) the advantages and characteristics of thermal metrology using thin or thick films, ii) their design and manufacturing, iii) the specificities of thin film thermocouples and resistance thermometers and finally various examples of achievement. © 2015 Owned by the authors, published by EDP Sciences.

Wang L.,CAS Institute of Process Engineering | Fan Y.,CNRS Nantes Thermocinetique Lab | Luo L.,CNRS Nantes Thermocinetique Lab
Computers and Fluids | Year: 2014

The shape optimization of a flat-type arborescent fluid distributor is studied for the purpose of process intensification, in which a shape optimization algorithm based on the lattice Boltzmann method (LBM) (Wang et al., 2010) is adopted with the objective of decreasing the flow resistance subject to the constraint of a constant fluid volume. Prototypes of the initial distributor as well as the optimized one are designed. Fluid distribution and hydraulic characteristics of these distributors are investigated numerically. Results show that the pressure drop of the optimized distributor is between 15.9% and 25.1% lower than that of the initial reference while keeping a uniform flow distribution, demonstrating the process intensification in fluid distributor, and suggesting the significance of the proposed optimization algorithm in engineering optimal design. © 2014 Elsevier Ltd.

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