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International audience; Background: We previously reported a 35-gene expression classifier identifying four clear-cell renal cell carcinoma groups (ccrcc1 to ccrcc4) with different tumour microenvironments and sensitivities to sunitinib in metastatic clear-cell renal cell carcinoma. Efficacy profiles might differ with nivolumab and nivolumab-ipilimumab. We therefore aimed to evaluate treatment efficacy and tolerability of nivolumab, nivolumab-ipilimumab, and VEGFR-tyrosine kinase inhibitors (VEGFR-TKIs) in patients according to tumour molecular groups.Methods: This biomarker-driven, open-label, non-comparative, randomised, phase 2 trial included patients from 15 university hospitals or expert cancer centres in France. Eligible patients were aged 18 years or older, had an Eastern Cooperative Oncology Group performance status of 0-2, and had previously untreated metastatic clear-cell renal cell carcinoma. Patients were randomly assigned (1:1) using permuted blocks of varying sizes to receive either nivolumab or nivolumab-ipilimumab (ccrcc1 and ccrcc4 groups), or either a VEGFR-TKI or nivolumab-ipilimumab (ccrcc2 and ccrcc3 groups). Patients assigned to nivolumab-ipilimumab received intravenous nivolumab 3 mg/kg plus ipilimumab 1 mg/kg every 3 weeks for four doses followed by intravenous nivolumab 240 mg every 2 weeks. Patients assigned to nivolumab received intravenous nivolumab 240 mg every 2 weeks. Patients assigned to VEGFR-TKIs received oral sunitinib (50 mg/day for 4 weeks every 6 weeks) or oral pazopanib (800 mg daily continuously). The primary endpoint was the objective response rate by investigator assessment per Response Evaluation Criteria in Solid Tumors version 1.1. The primary endpoint and safety were assessed in the population who received at least one dose of study drug. This trial is registered with ClinicalTrials.gov, NCT02960906, and with the EU Clinical Trials Register, EudraCT 2016-003099-28, and is closed to enrolment.Findings: Between June 28, 2017, and July 18, 2019, 303 patients were screened for eligibility, 202 of whom were randomly assigned to treatment (61 to nivolumab, 101 to nivolumab-ipilimumab, 40 to a VEGFR-TKI). In the nivolumab group, two patients were excluded due to a serious adverse event before the first study dose and one patient was excluded from analyses due to incorrect diagnosis. Median follow-up was 18·0 months (IQR 17·6-18·4). In the ccrcc1 group, objective responses were seen in 12 (29%; 95% CI 16-45) of 42 patients with nivolumab and 16 (39%; 24-55) of 41 patients with nivolumab-ipilimumab (odds ratio [OR] 0·63 [95% CI 0·25-1·56]). In the ccrcc4 group, objective responses were seen in seven (44%; 95% CI 20-70) of 16 patients with nivolumab and nine (50% 26-74) of 18 patients with nivolumab-ipilimumab (OR 0·78 [95% CI 0·20-3·01]). In the ccrcc2 group, objective responses were seen in 18 (50%; 95% CI 33-67) of 36 patients with a VEGFR-TKI and 19 (51%; 34-68) of 37 patients with nivolumab-ipilimumab (OR 0·95 [95% CI 0·38-2·37]). In the ccrcc3 group, no objective responses were seen in the four patients who received a VEGFR-TKI, and in one (20%; 95% CI 1-72) of five patients who received nivolumab-ipilimumab. The most common treatment-related grade 3-4 adverse events were hepatic failure and lipase increase (two [3%] of 58 for both) with nivolumab, lipase increase and hepatobiliary disorders (six [6%] of 101 for both) with nivolumab-ipilimumab, and hypertension (six [15%] of 40) with a VEGFR-TKI. Serious treatment-related adverse events occurred in two (3%) patients in the nivolumab group, 38 (38%) in the nivolumab-ipilimumab group, and ten (25%) patients in the VEGFR-TKI group. Three deaths were treatment-related: one due to fulminant hepatitis with nivolumab-ipilimumab, one death from heart failure with sunitinib, and one due to thrombotic microangiopathy with sunitinib.Interpretation: We demonstrate the feasibility and positive effect of a prospective patient selection based on tumour molecular phenotype to choose the most efficacious treatment between nivolumab with or without ipilimumab and a VEGFR-TKI in the first-line treatment of metastatic clear-cell renal cell carcinoma.

International audience; Nivolumab and cabozantinib are approved agents in mRCC patients after sunitinib/pazopanib (TKI) failure. However, the optimal sequence, cabozantinib then nivolumab (CN) or nivolumab then cabozantinib (NC), is still unknown. The CABIR study aimed to identify the optimal sequence between CN and NC after frontline VEGFR-TKI. In this multicenter retrospective study, we collected data from mRCC pts receiving CN or NC, after frontline VEGFR-TKI. A propensity score (PrS) was calculated to manage bias selection, and sequence comparisons were carried out with a cox model on a matched sample 1:1. The primary endpoint was progression-free survival (PFS) from the start of second line to progression in third line (PFS2-3 ). Key secondary endpoints included overall survival from second line (OS2 ). Out of 139 included mRCC patients, 38 (27%) and 101 (73%) received CN and NC, respectively. Overlap in PrS allowed 1:1 matching for each CN pts, with characteristics well balanced. For both PFS2-3 and OS2 , NC sequence was superior to CN (PFS2-3 : HR = 0.58 [0.34-0.98], P = .043; OS2 : 0.66 [0.42-1.05], P = .080). Superior PFS2-3 was in patients treated between 6 and 18 months with prior VEGFR-TKI (P = .019) and was driven by a higher PFSL3 with cabozantinib when given after nivolumab (P

Resume Les indications des inhibiteurs de checkpoint (ICP) immunitaire sont maintenant tres etendues et ont fait emerger des complications endocriniennes specifiques avec lesquelles les oncologues ont du se familiariser. L’hypophysite en est un exemple typique, devenue une complication non rare des ICPs, touchant jusqu’a 10 % des patients traites par anti-CTLA4. Elle survient classiquement deux a trois mois apres l’initiation du traitement. Le tableau associe typiquement cephalees et alteration de l’etat general, associees a une hyponatremie. Les atteintes hormonales les plus frequentes touchent les secteurs thyreotropes, gonadotrope et corticotrope. L’atteinte corticotrope fait la gravite de cette pathologie, necessitant la mise en place urgente d’une supplementation, sans attendre la confirmation biologique dans les cas severes. L’IRM doit etre systematiquement realisee, essentiellement pour eliminer les diagnostics differentiels, dont les metastases hypophysaires. L’hypophysite induite par les ICPs de type anti-PD1/PDL1 est une entite a part, de survenue retardee, pauci-symptomatique, mais caracterisee par une insuffisance corticotrope systematique et definitive, le plus souvent isolee au vu des premieres donnees publiees. Le traitement repose sur la corticotherapie a forte dose uniquement en cas de cephalees resistantes ou d’insuffisance corticotrope decompensee, et sur la supplementation hormonale systematique des deficits antehypophysaires. Les patients necessiteront une supplementation hormonale a vie, et doivent etre pris en charge et eduques en endocrinologie. Une fois l’episode aigu resolu, l’immunotherapie peut etre poursuivie si le patient en a un benefice. Compte tenu du caractere peu symptomatique et de la gravite potentielle de ces hypophysites, une surveillance biologique systematique est necessaire pendant le traitement par ICPs.

A new method for fouling detection in a heat exchanger is proposed. This method is based on the sensitivity of its impulse response (time version of its transfer function) with fouling. The concept is validated here numerically for a shell and tube heat exchanger in steady state regime, perturbed thermally by a transient surface source. This method is presented here, on a theoretical ground. It can be implemented online, whatever the geometric and structural characteristics of the setup. It only requires the use of regular temperature sensors and actuators. The only condition concern the equations of the model of the heat exchanger which have to be linear with time invariant coefficients.

International audience

International audience; BACKGROUND: Age-related immune dysfunction might impair the efficacy of immune checkpoint inhibitors (ICIs) in older patients. We aimed to evaluate the impact of age on clinical outcomes and tolerance of ICIs in a real-life setting. METHODS: All patients receiving a single-agent ICI (cytotoxic T-lymphocyte-associated protein 4 [CTLA-4] or programmed death(ligand)1 [PD(L)-1] inhibitors) for the standard treatment of a locally advanced or metastatic cancer were included in this retrospective multicentric series. The primary end-point was overall survival (OS). Progression-free survival (PFS) and immune-related adverse events (irAEs) were secondary end-points. The impact of age was assessed using the threshold of 70 years. RESULTS: A total of 410 patients were included, for 435 lines of treatment, including 150 lines (34%) given to patients aged 70 years or older. The primary tumour types were lung cancer (n = 304, 74%), melanoma (n = 79, 19%) and urologic cancer (n = 27, 7%). Most of the administered treatments were PD(L)-1 inhibitors (n = 356, 82%). Median follow-up reached 46 months in the CTLA-4 cohort, and 20 months in the PD(L)-1 cohort. In both treatment cohorts, age did not impact OS (respectively, HR = 0.82, 95% CI 0.5-1.4; log-rank P = 0.49 and HR = 0.9, 95% CI 0.7-1.1; log-rank P = 0.27) or PFS (HR = 0.7, 95% CI 0.4-1.1; log-rank P = 0.13 and HR = 0.9, 95% CI 0.7-1.1; log-rank P = 0.19). Grade 3-4 irAEs rates were not statistically different between older and younger patients (11% vs 12%, P = 0.87). CONCLUSION: In a large real-world series of patients treated by ICI monotherapy, the long-term clinical outcomes were not statistically different between older or younger patients, with no increased immune-related toxicity.

International audience; Ectodysplasin receptor EDAR is seen as a typical Tumor Necrosis Factor receptor (TNFR) family member known to interact with its ligand Eda-A1, and signaling mainly through the nuclear factor-kappaB (NF-κB) and c-jun N-terminal kinases pathways. Mutations in genes that encode proteins involved in EDAR transduction cascade cause anhidrotic ectodermal dysplasia. Here, we report an unexpected pro-apoptotic activity of EDAR when unbound to its ligand Eda-A1, which is independent of NF-κB pathway. Contrarily to other death receptors, EDAR does recruit caspase-8 to trigger apoptosis but solely upon ligand withdrawal, thereby behaving as the so-called dependence receptors. We propose that pro-apoptotic activity of unbound EDAR confers it a tumor suppressive activity. Along this line, we identified loss-of-pro-apoptotic function mutations in EDAR gene in human melanoma. Moreover, we show that the invalidation of EDAR in mice promotes melanoma progression in a B-Raf mutant background. Together, these data support the view that EDAR constrains melanoma progression by acting as a dependence receptor.

International audience; Transient conjugate heat transfer (advection and diffusion) inside a heterogeneous physical system composed of solids and flowing fluids is considered here. Starting from a steady state initial temperature field, a single separable thermal excitation (thermal power or temperature difference) is activated. The heat equation as well as its associated boundary and interface conditions are assumed to be linear with time independent coefficients : there is no time nor temperature dependence of the thermophysical properties and velocity fields of both solids and fluids present in the system. In this case, it is shown that the temperature rise or heat flux response at any point of the system (or their space integrated quantities) is a convolution product between the intensity of the relative thermal excitation and a specific transfer function. In this work, a semi-analytical expression of the transfer function that takes into account the lateral heat losses, conduction and advection in the fluid as well as conduction in the solid walls (conjugate heat transfer) of a flat channel with a volumic heat source (half heat exchanger) in transient state is derived. The analytical transfer function can be obtained for a simple geometry only. For complex geometries it can be identified experimentally. The analytical expression of the transfer function has been compared with that identified for a half-exchanger to verify the analytical expression of the transfer function and to show that this function can be identified experimen-*. Corresponding author.

International audience; Linear Time Invariant (LTI) systems can be modeled by transfer functions linking inputs to outputs through convolution products. This concept is experimentally validated in the case of an upstream heated channel with thick walls and steady liquid flowrate using two calibration experiments with different unsteady upstream heating powers. Proper identification of transfer functions (impedances and transmittances) requires the inversion of experimental temperature measurement through regularization techniques. Truncated Singular Value Decomposition (TSVD) and Zero-order Tikhonov regularization are tested and compared for this application.

[EN] Heat and mass transfers at the impact of a droplet onto a hot solid surface are investigated experimentally. Millimetersized water droplets impinges onto a perfectly flat sapphire surface heated at 600°C. The temperature of the liquid inside the droplet is measured using the two-color laser-induced fluorescence (2cLIF) technique. Water is seeded with a temperature-sensitive fluorescent dye, while a nanosecond pulsed laser is used for the excitation of the fluorescence. The ratio of fluorescence signal detected in two appropriate spectral bands allows to determine the liquid temperature. One advantage of this non-intrusive optical technique is that it eliminates adverse effects associated with signal variations caused by droplet shape during its impact. In parallel, the temperature of the solid surface is characterized using infrared thermography. The latter measurements are made possible by the deposition of a nanosize coating of titanium aluminium nitride (TiAlN) on the upper surface of the sapphire window. Thanks to the high frame rate of the IR camera, the time evolution of the heat flux distribution at the solid surface can be reconstructed. A comparison of IR and 2cLIF techniques enable to correlate the heating of the liquid with the cooling of the wall. This reveals that most of the heat removed from the solid surface is devoted to the heating of the liquid, the energy used for liquid vaporization being significantly lower., The authors acknowledge the financial support of the Lorraine region through the CPER ENERBATIN projet.

Introduction Malignant mesothelioma is a deadly disease that is strongly associated with asbestos exposure. Peritoneal mesotheliomas account for 10% of all the cases. BRCA1 associated protein 1 (BAP1) is a deubiquitinating hydrolase that plays a key role in various cellular processes. Germline and somatic inactivation of BRCA1 associated protein 1 gene ( BAP1 ) is frequent in pleural mesothelioma; however, little is known about its status in peritoneal mesothelioma. Methods Taking advantage of the extensive French National Network for the Diagnosis of Malignant Pleural Mesothelioma and Rare Peritoneal Tumors and the French National Network for the Treatment of Rare Peritoneal Surface Malignancies, we collected biological material and clinical and epidemiological data for 46 patients with peritoneal mesothelioma. The status of BAP1 was evaluated at the mutational and protein expression levels and combined with our previous data on copy number alterations assessed in the same samples. Results We detected mutations in 32% of the malignant peritoneal mesotheliomas analyzed. In addition, we have previously reported that copy number losses occurred in 42% of the samples included in this series. Overall, 73% of the malignant peritoneal mesotheliomas analyzed carried at least one inactivated BAP1 allele, but only 57% had a complete loss of its protein nuclear expression. Better overall survival was observed for patients with BAP1 mutations ( p = 0.04), protein expression loss ( p = 0.016), or at least one of these alterations ( p = 0.007) independently of tumor histological subtype, age, and sex. Conclusions As in pleural mesothelioma, inactivation of BAP1 is frequent in peritoneal mesotheliomas. We found that BAP1 protein nuclear expression is a good prognostic factor and a more reliable marker for the complete loss of BAP1 activity than mutation or copy number loss.

International audience; A theoretical study relying on the thermal modelling of a Curie wheel, used for the conversion of low-grade waste heat into electrical power, is presented in this paper. It allows understanding the thermal behaviour of a Curie wheel operating in steady state in order to optimise its design. To this end, a stationary one-dimensional analytical thermal model, based on a Lagrangian approach, was developed. It allows determining the local distribution over time of the temperature in the magnetocaloric material exposed to a periodic sinusoidal heat source. Thanks to this model, the effects of different parameters (nature of the magnetocaloric material, nature and temperature of the fluid) were highlighted and studied.

International audience; BACKGROUND: Randomised controlled trials (RCTs) represent a major source of information on treatment-related adverse events (AEs). In this study, we reviewed the use and the reporting methods of aggregated-AEs (A-AEs) outcomes in RCTs reports published in oncology and compared that to the expectations of European Organisation for Research and Treatment of Cancer (EORTC) membership. METHODS: RCTs reports published between 2007 and 2011 were reviewed regarding the reporting of A-AEs-outcomes. A-AEs were defined as summary outcome combining several related AEs, usually grouped by organ system e.g. cardiac-AEs, dermatologic-AEs. Trial characteristics associated with the use of A-AEs outcomes were investigated. The expectation of EORTC members concerning A-AEs utilisation was queried through a survey. RESULTS: Among 325 RCTs published between 2007 and 2011, 94 (29%) included one or more A-AE outcomes. A clear description of the nature of AEs included in such aggregations was provided in 19 articles (20%). No description of A-AEs was conversely provided in the other 75 articles (80%). The most commonly used A-AEs-outcomes were dermatologic-AEs (45%) and cardiac-AEs (33%). In multivariate analysis, the use of A-AEs outcomes was more frequent when trials were conducted in Europe (p = 0.038) and in trials performed on colon/rectal cancers (p = 0.016). Finally, there is no consensus of EORTC members regarding the utilisation of A-AEs but a majority of them (88%) felt that a clear description of A-AEs should systematically be reported. CONCLUSIONS: The use of A-AEs is infrequent in oncology RCT manuscripts although their use is accepted by most clinicians. However, a clear definition of A-AEs is strongly recommended if they are to be used in order to avoid a loss of important details about drug toxicities that is useful to clinicians

International audience; BACKGROUND: Determination of drug safety and tolerability is usually based on the frequency of certain key adverse events (AEs) rather than the frequency of all-grade toxicities. We assessed the reporting of key AEs in oncology randomized, controlled trials (RCTs) and compared that with the expectations of the European Organization for Research and Treatment of Cancer (EORTC) membership. MATERIALS AND METHODS: RCTs reports published between 2007 and 2011 were reviewed regarding the reporting of key AEs, namely: grade 3/4 AEs, grade 5 AEs, and AEs resulting in study withdrawal or in dose reduction. Study characteristics associated with better reporting of key AEs were investigated. Finally, a survey was conducted among the EORTC membership to determine their expectations on key AEs reporting. RESULTS: Although the frequency of grade 3/4 was reported in most reports (96%), only 17% of them described the reporting threshold above which grade 3/4 AEs were included for reporting, raising the possibility that important but less frequent grade 3/4 AEs might be underreported. Frequency and nature of grade 5 AEs were adequately reported in 161 (50%) of manuscripts; AEs leading to study withdrawal in 61 manuscripts (19%); and AEs leading to dose reduction in 43 manuscripts (13%). In contrast, most EORTC members expected a comprehensive reporting of grade 5 AEs (96% of EORTC member's responses), AEs leading to study withdrawal (86%) and AEs leading to dose reduction (70%). In multivariate analysis, frequencies of grade 5 AEs were less frequently reported in European trials (P = 0.004). Frequencies of AEs leading to withdrawals were more frequently reported in trials funded by industry (P = 0.005) and in trials including patients with breast or urological cancers (P = 0.006). CONCLUSIONS: These findings suggest that current practice of key AEs reporting remains highly variable and sometimes inadequate in oncology RCTs reports. Current standards for safety reporting in RCTs should be revised to emphasize the importance of key AEs reporting

International audience; Under certain conditions (steady flows, no temperature dependence of thermophysical properties), the temperature rise at any point (solid or fluid) of a heat exchanger, whatever its type, is a convolution product between the thermalsource and the corresponding transfer function.Here a counter-flow heat exchanger is considered, where the hot fluid inlet temperature varies with time while the cold fluid inlet temperature is kept equal to the initial uniform temperature in the whole system. The transfer functions are estimated using synthetic temperature responses. This shows that temperature sensors located on the external surface of the exchanger can be used to detect fouling or to give informations about the outlet bulk temperatures of the fluids (steady state or transient thermal regimes).

National audience; Quelle que soit la forme de l'échangeur dont les débits et les propriétés thermo-physiques de chaque fluide restent inchangées dans le temps, l’échauffement en tout point du système (fluide ou parois) est un produit de convolution entre la source et la fonction de transfert correspondante. Dans le cadre de cette étude, on s’intéresse à un échangeur contre-courant plan où la température d’entrée du fluide chaud varie tandis que celle du fluide froid reste égale à la température initiale. Le travail présent correspond à un problème inverse d’identification, où les fonctions de transferts du système sont estimées à partir des observations des évolutions transitoires des températures correspondantes. Des résultats d’identifications (avec régularisation) des fonctions de transfert sur signaux synthétiques sont présentés. Ceci montre que l’on peut concevoir un capteur placé en surface externe non seulement capable de détecter l’encrassement mais aussi de donner des informations sur les températures moyennes de mélange à la sortie de deux fluides à la fois en régime thermique transitoire et permanent.

International audience; Abstract The techniques for solving the Inverse Heat Conduction Problem represent useful tools for designing heat transfer apparatuses. One of their most challenging applications derives from the necessity of catching what happens inside a heat transfer apparatus by monitoring the temperature distribution on the external wall of the device, possibly by means of contactless experimental methodologies. The research presented here deals with the application of a solution strategy of the Inverse Heat Conduction Problem (IHCP) aimed at estimating the local heat transfer coefficient on the internal wall surface of a pipe, under a forced convection problem. The solution strategy, formulated for a 2D model, is based on the Quadrupole Method (QM) coupled to the Truncated Singular Value Decomposition approach, used to cope with the ill-conditioning of the problem. \QM\ presents some advantages over the more classical domain or boundary discretization methods as for instance the fact that, being meshless, brings to a reduction of the computational cost. The analytical model, built under the QM, is validated by means of numerical simulations and the numerical outputs are then used as synthetic data inputs to solve the IHCP. The estimation methodology is also applied to experimental data regarding a forced convection problem in coiled pipes. Moreover, the adopted solution technique is compared to other two well-known and consolidated approaches: Finite Element Method coupled to the Tikhonov Regularization Method and Gaussian Filtering Technique. The comparison highlights that, for the problem here investigated, the Quadrupole Method coupled to the Truncated Singular Value Decomposition and Finite Element Method coupled to the Tikhonov Regularization Method perform better than the Gaussian Filtering Technique when the noise level is low, while, for higher noise level values, their efficiency is almost comparable, as it happens in the considered experimental study case.

International audience; This paper deals with reconstruction of the temperature and normal heat flux transient profiles inside a flat minichannel from external temperature measurement over its external heated face. It uses an analytical model which is written using Laplace and Fourier integral transforms whose output is verified through comparison with a finite elements code. Estimation of the Fourier harmonics of the external experimental temperature profile at different times is regularized through Truncated Singular Value Decomposition. A similar technique is used in time for a regularized deconvolution of each harmonics of this temperature. This inverse technique has been implemented on an experimental minifluidic bench with electrical heating and temperature measurement by thermocouples and infrared thermography, for a low Péclet number of the flow. The presented results show that the heat source can be recovered, as well as the internal normal heat flux and temperature distributions, including the bulk temperature of the liquid flow at any time. Possible applications concern the transient characterization and heat management of thermal systems, such as flat plate solar collectors or heat exchangers with low to medium temperature level, for fatal heat recovery.

International audience; Techniques for solving inverse problems as well as their applications are currently rapidly developing in all the different domains of physical sciences and particularly in Heat Transfer. These techniques are usually developped by applied mathematicians, statisticians and signal processing specialists. Experimentalists desiring to go beyond traditional data processing techniques for estimating the parameters of a model with the maximum accuracy feel often ill-prepared in front of inverse techniques. This paper is devoted to the presentation of the common methodology that can be used by a heat transfer specialist in order to solve either a parameter estimation problem (thermal characterization of a material for example) or a function estimation problem (estimation of a transient heat flux at the front face of a wall for example), starting from transient temperature measurements inside or on the external boundaries of the physical system. Once this common methodology shared by specialists of measurement inversion techniques, modeling techniques and experimental techniques, a very wide variety of tools (analysis of the sensitivity matrix, variance-covariance matrix of estimates, regularization and Bayesian techniques) are now available in order to avoid biases at different levels of this kind of involved task.

International audience; This paper is devoted to a theoretical and numerical study of different ways of calculating the Fourier transform of a noisy signal where the boundary conditions at the lateral boundaries of the measurement interval are not precisely known. This happens in different characterization problems where infrared camera is used for temperature measurements. In order to overcome this difficulty, the interval where the Fourier transform (its support) is supposed to be larger than the measurement domain is defined. Thus, this virtual interval larger than the measurement interval is used. We show that regularization by truncated singular value decomposition is able to yield good estimates to this very ill-posed inverse problem.

28 pages, 13 figures, 2 test cases; The Gauss Newton method of least squares minimization for non-linear parameter estimation is revisited for parameters with different physical units. A normalization of each parameter with respect to its nominal value, that is at iteration number k-1, is implemented, which leads to a linear tangent model. This model uses the sensitivity matrix composed of the scaled sensitivity coefficients. It is decomposed under a singular values form and the covariance matrix of iterate number k is calculated. When the scaled standard deviation of one parameter estimates takes a too large value, inversion of the tangent model becomes ill-posed. Regularization is made by giving the smallest singular values infinite levels, which allows keeping the total number of parameters to be estimated unchanged : this regularization leads to a better conditioned problem in the following iterations until convergence of the residuals is reached. The corrresponding algorithm is tested in the case of two very ill posed-examples. This type of estimation performs very well when compared to the Lebenverg Marquardt algorithm.

Combustion, spray and flow dynamics for aerospace propulsionCombustion, spray and flow dynamics for aerospace propulsion; International audience; In aero-engines, droplet/wall interaction phenomena have a considerable influence on the mixture formation process and on wall heat fluxes. Impinging droplets may rebound, splash into secondary droplets or form a liquid film onto the solid surface. Droplet rebound and splashing is also a mechanism for the back penetration of the fuel vapor in the central region of the combustion chamber where the gas temperature is high enough for ignition. This work is an experimental study aiming at characterizing the heat transfers induced by the impingement of water droplets (diameter 80ֱ80 ֭) on a thin nickel plate heated by electromagnetic induction. The temperature of the rear face of the nickel sample is measured by means of an infrared camera and the heat removed from the wall due to the presence of the droplets is estimated using a semi-analytical inverse heat conduction model. In parallel, the temperature of the droplets is measured using the two-color Laser-Induced Fluorescence Thermometry which has been extended to imagery for the purpose of these experiments. The measurements of the variation in the droplet temperature occurring during an impact allow determining the liquid sensible heat. Measurements are performed at surface conditions well above the Leidenfrost temperature. A wide range of Weber numbers corresponding to the bouncing and splashing regimes are tested. Comparison between the heat flux removed from the wall and the sensible heat gained by the liquid allows estimating the heat flux related to liquid evaporation. Results reveal that the respective level of the droplet sensible heat and the heat lost due to liquid vaporization can vary significantly with the droplet sizes and the Weber number.

International audience; Modelling fluid flow and heat transfer inside a mini- or micro-channel constitutes a challenge because it requires taking into account many effects that do not occur in traditional macrostructured systems. A semi-analytical heat transfer model that takes into account conduction and advection in the fluid as well as conduction in the solid walls (conjugate heat transfer) of a flat mini-channel is first derived and verified. It is based on Fourier transforms of the temperature and normal flux in the direction of the Poiseuille flow. It allows to relate its bulk temperature Tb(x) to external surface sources by two transfer functions without the use of any internal heat transfer coefficient distribution, whatever the location of these sources. The second part of the paper is devoted to the use of this model in an inverse way, that is to retrieve the Tb(x) distribution starting from the additional observation of the noised synthetic temperature profiles over the external faces of both walls of the channel. Estimations of the average velocity and of the external heat transfer coefficient are first implemented. The temperature and flux distributions over the internal faces of the walls are estimated by an inverse method then, before a reconstruction of the internal bulk temperature profile.

International audience; When droplets impinge onto a hot wall, different regimes can be observed depending on the wall temperature and Weber number. In the case of interest, the temperature of the wall is more than the Leidenfrost temperature and the Weber number based on normal velocity of the droplet is less than the threshold value leading to the splashing regime (We < 80). We particularly focused on the perfect bouncing regime (We < 30) for which an impinging droplet levitates on a thin layer of its own vapour. This vapour is instantaneously created between the base of the deforming droplet and the heated surface so that direct contact with the hot solid is avoided. For these low Weber numbers, the droplet surface energy is high enough compared to its kinetic energy to permit the rebound, so that the droplet recovers its initial shape without breaking up after the bounce. Although the generated vapour insulates the droplet, some heat is exchanged with the wall during the interaction (i.e. during the resident time). In this paper, we report on experimental measurements of heat transfer due to droplet impact in the Leidenfrost regime. The energy released by the wall and measured using an inverse conduction method leads to an estimation of the heat transfer coefficient during impact in the Leidenfrost regime. For that, the time evolution of the droplet base surface is estimated using a simple modelling validated on experimental data. Finally, the energy measured is compared to existing models.

International audience; In this paper, we consider a two-dimensional inverse heat conduction problem (IHCP) in a jet cooling experiment. A nickel disk is heated by an induction device up to 600 °C before being cooled by a water jet impinging on its front side and, at the same time, the temperature on the rear side is measured by a high resolution infrared thermography. The transient heat flux at the cooled face is determined from the IR measurements. To achieve this goal, an inverse heat conduction problem (IHCP) is formulated using an analytical solution of the direct problem expressed in the Hankel space. Then, results of simulated experiments are given in order to illustrate the performance of this method but also its limitations. Finally, an example of heat flux estimation from real temperature measurements is made.

BACKGROUND The Consolidated Standards of Reporting Trials (CONSORT) guidelines were developed in the mid-1990s for the explicit purpose of improving clinical trial reporting. However, there is little information regarding the adherence to CONSORT guidelines of recent publications of randomized controlled trials (RCTs) in oncology. METHODS All phase III RCTs published between 2005 and 2009 were reviewed using an 18-point overall quality score for reporting based on the 2001 CONSORT statement. Multivariable linear regression was used to identify features associated with improved reporting quality. To provide baseline data for future evaluations of reporting quality, RCTs were also assessed according to the 2010 revised CONSORT statement. All statistical tests were two-sided. RESULTS A total of 357 RCTs were reviewed. The mean 2001 overall quality score was 13.4 on a scale of 0-18, whereas the mean 2010 overall quality score was 19.3 on a scale of 0-27. The overall RCT reporting quality score improved by 0.21 points per year from 2005 to 2009. Poorly reported items included method used to generate the random allocation (adequately reported in 29% of trials), whether and how blinding was applied (41%), method of allocation concealment (51%), and participant flow (59%). High impact factor (IF, P = .003), recent publication date (P = .008), and geographic origin of RCTs (P = .003) were independent factors statistically significantly associated with higher reporting quality in a multivariable regression model. Sample size, tumor type, and positivity of trial results were not associated with higher reporting quality, whereas funding source and treatment type had a borderline statistically significant impact. CONCLUSION The results show that numerous items remained unreported for many trials. Thus, given the potential impact of poorly reported trials, oncology journals should require even stricter adherence to the CONSORT guidelines.

International audience; In hot rolling, the mechanical properties of steel alloys are conditioned by the rolling process but a great part is ensured by the cooling of the hot strip mill. Well controlling this cooling rate and its homogeneity is thus of primary importance for obtaining steels with desired mechanical properties. As the water used in the cooling stage of the rolling process can be polluted by oil (in hot mill strip, some oil is used to lubricate the rolls and a part of it can pollute the water), it is important to know how much varies the cooling rates when water is polluted. In this study, transient cooling has been investigated during quenching of a hot metal disk with various subcooled oil-in-water emulsion jets. The aim of this work is to compare the cooling efficiency of oil-in-water emulsion jet with a pure water jet. Experimental investigations of axi-symmetric jet impingements on a preheated hot metal disk (500–600 °C) have been performed with various oil-in-water emulsions. The transient cooling heat fluxes on the quenched side are estimated by coupling the measurement of the temperature field of the other side (rear face) with a semi-analytical inverse heat conduction model.

International audience

This numerical study deals with the estimation of both unknown position and intensity of a heat source in diffusive problems, from the knowledge of local temperature data. The source is assumed to be fixed but its intensity varies with time. The originality of this paper lies in the use of reduced models to solve the inverse problem. The source position being unknown, a specific approach is proposed, involving the Modal Identification Method (MIM) allowing us to obtain a RM relative to a set of output temperatures. The source is modelled as f(r,rs)u(t), where f covers the whole domain and mimics a source centred in rs. Starting with initial guess for rs, RMs relative to outputs and their first derivatives with respect to rs, are identified. A Quasi-Newton algorithm is used for searching rs, and according to a Taylor expansion, new RMs are built for current rs to estimate u(f) and compute sensitivities. When rs cannot be modified anymore by the iterative algorithm, the Detailed Model is called to update the RMs series. The approach is first described in detail for a ID case, then expressions for 2D and 3D cases are given. An academic 3D heat diffusion problem illustrates the method.

International audience; Thermal conductivity of gas diffusion layers (GDL) used in fuel cells is a key parameter for the analysis of heat transfer in membrane electrodes assembly (MEA). In this paper, we focus on non-woven carbon felts. Although correlations are available, the felts thermal conductivity is difficult to estimate due to the nature of heat transfer in porous and fibrous materials: the effective conductivity of the solid phase is roughly known and the correlations giving effective conductivity of porous media (solid and fluid phases) have restricted range of application. Consequently, we chose to associate an analytical and an experimental approach. Their results converge and clearly show that the majority of values encountered in the literature are, most probably, highly overestimated.

Dans le precedent dossier [AF 4 515], le contexte de la mise en œuvre des techniques inverses a ete presente, en termes d'objectifs de l'utilisateur et de methodologies correspondantes. Le probleme de l'estimation de parametres, ou de l'estimation d'une fonction prealablement parametrisee, d'un modele dynamique lineraire a ete etudie. L'accent a ete mis sur les notions de coefficients de sensibilite et de propagation du bruit de mesure considere comme la realisation d'une variable aleatoire. Enfin, nous avons traite le meme type de probleme d'inversion de mesures dans le cas d'un modele non lineaire, mais toujours en dimensions finies. Differentes methodes performantes de minimisation d'un critere d'ecart, basees sur les coefficients de sensibilite, ont ete presentees. Dans ce dossier, nous revenons tout d'abord sur les notions de probleme inverse bien ou mal pose, en degageant des approches et des outils destines a mieux caracteriser cet aspect de l'inversion. Cela passe par une necessaire quantification du degre de gravite de ce caractere (« mauvaise pose ») a l'aide de l'adoption d'un ou plusieurs criteres. Nous mettons ensuite en evidence six causes possibles d'erreur d'estimation. Ces causes depassent le seul aspect mathematique du probleme considere. Des outils de diagnostic de la qualite de l'inversion sont alors proposes. La notion de regularisation d'un probleme inverse mal pose, avec le necessaire compromis entre dispersion et biais de l'estimateur, est ensuite introduite. Quelques methodes populaires de regularisation sont alors presentees. Elles sont appliquees et comparees sur un meme exemple. Nous introduisons egalement l'approche bayesienne, permettant l'apport d'informations additionnelles externes plus ou moins precises a l'inversion de mesures. Enfin une methode particuliere de reduction de modele par identification est ensuite presentee. Elle s'appuie sur des donnees d'entrees et de sorties obtenues soit par des mesures, soit par des simulations issues d'un modele detaille de reference. Le premier cas correspond a la construction experimentale de modele, procedure qui peut s'apparenter a la calibration d'un systeme. Le second cas correspond a la mise en œuvre d'une technique de reduction de modele qui s'appuie sur un principe de parcimonie permettant de relier de facon synthetique uniquement les entrees et les sorties utiles. Dans les deux cas, le modele reduit construit peut etre ensuite utilise pour estimer des entrees a partir de sorties.

International audience; The aim of this study is the understanding of the main phenomena governing fuel cell performances. We present a fuel cell model that takes into account gas diffusion in the porous electrodes, water diffusion and electro-osmotic transport through the polymeric membrane, and heat transfer in both the Membrane Electrodes Assembly (MEA) and bipolar plates. This model is constructed by combining independent descriptions of heat and mass transfers in the cell with a third description of coupled charge and mass transfers in the electrodes, considered porous. The results show that thermal gradients in the MEA could lead to thermal stresses at high current densities. The feeding gas temperature influence on the cell temperature is also important.

International audience; This article discusses the comparison between two methods developed for estimating a local heat transfer coefficient in two-dimensional cooled cylinders. The estimation procedure in based on the solution of an inverse heat conduction problem using temperature measurements taken inside the cylinder. The first method uses in analytical solution (integral transform) of the inverse problem under investigation. The second method uses the conjugate gradient method with the adjoint state equation approach to solve the same problem. The two methods were compared by considering several numerical examples involving test cases without and with measured errors. Finally, the two methods are compared using experimental data obtained in our laboratory. The presented results shows that the two methods give approximately the same results. However the implementation seems easier for the analytical method.

Les deux methodes des temps partiels et des moments temporels partiels, qui sont basees sur un modele analytique, permettent de traiter le thermogramme issu d'une experience flash qui est destinee a mesurer la diffusivite thermique d'un materiau. Par une approche stochastique, on montre comment l'on peut passer des caracteristiques du bruit de mesure numerise du detecteur de temperature aux ecart-types des estimateurs de la diffusivite et du nombre de Biot relatif aux pertes. La repetition d'experiences flash sur un meme echantillon permet, par une etude statistique, de valider l'analyse theorique precedente et de conclure a la superiorite de la deuxieme methode.

Vacuum holding induction furnaces are used for the manufacturing of turbine blades by loss wax foundry process. Heat transfer control in a holding furnace is crucial to ensure the quality of manufacturing. This work has 3 major parts, which are the detailed modelling, reduced modelling and experiments. An axyisymmetric furnace and its load have been numerically modelled using FlexPDE and COMSOL Multiphysics, finite element codes. Modelling takes as inputs the electric power consumed by inductors and gives the temperature field in the heating module. The studied reduced models are phyisical convolutive models (enthalpic (0D), 1 dimension analytical (1D)) and parametric like AutoRegressive with eXogeneous inputs (ARX). ARX models have been compared to convolutive models (identification, validation). The goal is to get temperatures in the heating module without local presence of physical sensors (virtual sensor). Detailed and reduced models have been compared to experiments on the furnace. This last part is not described in this document, Les fours de maintien à induction sous vide sont utilisés pour la fabrication d'aubes de turbine à l'aide du procédé de fonderie à cire perdue. La maîtrise de la thermique de ce dernier est primordiale afin d'assurer la qualité de la production. Ce travail est composé de 3 grandes parties : la modélisation détaillée du four, la modélisation réduite et l'expérience. Un four axisymétrique et sa charge ont été modélisés numériquement à l'aide des logiciels FlexPDE et COMSOL Multiphysics. Ces modèles utilisent en entrée la puissance consommée par les inducteurs et fournissent en sortie la température en tout point du module de chauffe et de la charge. Les modèles réduits étudiés sont des modèles physiques dit convolutifs (enthalpique (0D), analytique de dimension 1 (1D)) et paramétrique de type AutoRégressifs avec variables eXogènes (ARX). Les modèles ARX ont été comparés aux modèles convolutifs (procédures d'identification, puis de validation, de modèles). L'objectif est d'accéder à des températures en certains points du four sans présence d'un capteur physique local (capteur virtuel). Les modélisations détaillées et réduites ont été comparées à des expériences réalisées sur four de production. Cette dernière partie n'est pas décrite dans ce mémoire

To convert the industrial waste heat into mechanical, or electrical energy, is a way to decrease the greenhouse gases emission and the energy consumption. The present PhD thesis is co-financed by the french Environment and Energy Management Agency (ADEME), in this context. The other co-financer, the company Hevatech, exploits the patent of a new heat converter into electricity named Turbosol®. Turbosol® is a good candidate for the industrial waste heat recovery. The concept is currently developed by the study of a prototype and the installation of the prototype on industrial site. The Turbosol® cycle originality is the quasi-isothermal expansion of the water vapor. Consequently, the Turbosol® cycle is close to the Carnot cycle. In the manuscript first part, the possibility of the feasibility of an engine operating according to the Carnot cycle is studied. A Carnot engine with a changing phase working fluid is modeled and optimized by maximization of the net power output. The variables are the optimal vaporization and condensation temperatures, and the optimal allocation of a total thermal transfer area between the condenser and the evaporator. Then, in the second part, the model of the Carnot engine is adapted to the Turbosol® prototype. In the sensitivity analysis, the vaporization temperature and the mass flow rate of the working fluid are identified as optimization variables. So, the Turbosol® converter is optimized by maximization of the net power output and the first law efficiency for a given waste heat fluid to valorize, La valorisation des rejets thermiques industriels par leur conversion en énergie mécanique, et éventuellement en électricité, est un moyen de réduire les émissions de gaz à effet de serre et de réduire la consommation énergétique des industries. La présente bourse de thèse est cofinancée par l’Agence De l’Environnement et de la Maitrise de l’Energie (ADEME) dans ce contexte. Le co-financeur de la thèse, Hevatech, est une entreprise qui exploite le brevet d’un nouveau convertisseur de chaleur en électricité appelé Turbosol®. Turbosol® est un bon candidat pour la valorisation de la chaleur fatale industrielle. Le concept en est au stade du développement du prototype et de l’installation de pilotes sur site. L’originalité du cycle de Turbosol® est la détente quasi-isotherme de la vapeur d’eau. Ainsi, le cycle de Turbosol® est proche du cycle de Carnot. La première partie de la thèse porte sur le cycle de Carnot et la faisabilité d’une machine fonctionnant selon le cycle de Carnot. Une machine fonctionnant selon le cycle de Carnot avec de l’eau changeant de phase pendant le chauffage est modélisée, puis optimisée par maximisation de la puissance nette produite. Les variables de l’optimisation sont les températures de vaporisation et de condensation du fluide cyclé, ainsi que la répartition de la surface d’échange entre l’évaporateur et le condenseur. Puis, dans la seconde partie, le modèle de la machine de Carnot est adapté au cas particulier de Turbosol®. Cela permet de simuler le fonctionnement du prototype de Turbosol. L’étude de sensibilité aux variables de commande du modèle a permis d’identifier la température de vaporisation et le débit massique du fluide de travail comme des variables d’optimisation. Ainsi, le convertisseur est optimisé par maximisation de la puissance nette produite et par maximisation du rendement pour un rejet thermique à valoriser donné

A semi-analytical model allowing to simulate the transient conjugate heat transfer in mini/macro plane channel subject to a heat source(s) localized on the external face(s), was presented and verified. The developed model takes into account advection-diffusion in the fluid and conduction in the solid. As the hydraulic diameter of the channel becomes small, the internal experimental characterization (measurement of temperature and heat flux) using internal sensors become tricky because internal sensors located may compromise the structural integrity of the whole system. A non-intrusive method for estimating the internal conditions from infrared temperature measurements on the external faces using the semi-analytical model was performed. Since the classic convective heat transfer coefficient loses its meaning in transient state, an alternative approach based on a transfer function, valid for Linear Time-Invariant (LTI) systems, was highlighted. This function can be calculated analytically only for a simple geometry. For complex geometries it can be estimated experimentally. Thanks to intrinsic character of this function, two characterization methods were designed. The first to estimate the temperature at a point from a measurement at another point in the system (virtual temperature sensor). The second method concerns the detection of fouling layers that may appear in the heat exchanger from temperature measurements on the external faces, Un modèle semi-analytique permettant de simuler le transfert thermique conjugué dans un mini/macro canal plan soumis à des sources de chaleur surfaciques localisées sur les faces externes et variantes en fonction du temps, a été présenté et vérifié. Plus le diamètre hydraulique du canal est petit, plus la caractérisation expérimentale interne (mesure des températures et des flux) en régime thermique permanent ou transitoire à l'aide des capteurs internes est délicate. Une méthode non-intrusive permettant d'estimer les conditions internes à partir des mesures de température par thermographie infrarouge sur les faces externes et d'un modèle semi-analytique, a été effectuée. Comme le coefficient de transfert convectif forcé classique perd son sens en régime instationnaire, une approche alternative basée sur une fonction de transfert, valable pour un système linaire et invariant dans le temps a été mise en œuvre. Cette fonction peut être calculée analytiquement (uniquement pour une géométrie simple) ou estimée expérimentalement (géométrie complexe). Grâce au caractère intrinsèque de cette fonction de transfert, deux capteurs virtuels ont été conçus : capteur virtuel de température et détecteur d'encrassement permettent respectivement d'estimer les températures internes et de détecter l'encrassement qui peut avoir lieu dans l'échangeur à partir des mesures de températures sur les faces externes

This study presents the development of measurement of porosity and velocity of flow made by MRI in packed beds with glass and polymer beads of various size saturated in water. The advantage of polymer beads is that they do not contain elements ferro or paramagnetics, contrary to the glass beads which disrupt the magnetic field creating artifacts on the MRI images. The calibration of the MRI velocity measurements was achieved from Poiseuille flow in a tube at different flow rates. Two situations were examined: first, the observation of interstitial flows between the beads minimizes partial volume effects and facilitates the correction of the phenomenon of phase aliasing. On the other hand, the measurement of average interstitial velocity (Darcy) requires using simultaneous velocity image and porosity image. In this case, it is preferable to adjust the strength of magnetic field gradient in the velocimetry sequence in a way to avoid any phase aliasing. The geometry of the flow cell was chosen to enable comparison by the MRI method between volume flow rates of water in the porous media and in the outer annulus.; Cette étude présente la mise au point de mesures de porosité et de vitesse d'écoulement faites par IRM dans des colonnes de billes de verre et de polymère de différentes granulométries saturées en eau. L'avantage des billes en polymère est qu'elles ne contiennent pas d'éléments ferro ou paramagnétiques, contrairement aux billes de verre qui perturbent le champ magnétique créant des artéfacts sur les images IRM. La séquence d'IRM utilisée pour l'étude des écoulements en milieu poreux a été préalablement paramétrée à l'aide d'une étude sur un écoulement de Poiseuille. Deux situations ont été examinées : d'une part, l'observation des écoulements interstitiels entre les billes permet de minimiser les effets de volume partiel et de faciliter la correction du phénomène de repliement de phase. D'autre part, la mesure de vitesses moyennes (Darcy) nécessite d'utiliser simultanément les images de vitesse et les images de porosité. Dans ce cas, il est préférable d'ajuster la puissance des gradients d'encodage de vitesse de façon à éviter tout phénomène de repliement de phase. La géométrie du dispositif utilisé a permis une comparaison rigoureuse des mesures de débit de façon intrinsèque uniquement par IRM (débit en milieu poreux et dans l'espace annulaire) et aussi à partir de la mesure directe du débit (pesée).

This study presents the development of measurement of porosity and velocity of flow made by MRI in packed beds with glass and polymer beads of various size saturated in water. The advantage of polymer beads is that they do not contain elements ferro or paramagnetics, contrary to the glass beads which disrupt the magnetic field creating artifacts on the MRI images. The calibration of the MRI velocity measurements was achieved from Poiseuille flow in a tube at different flow rates. Two situations were examined: first, the observation of interstitial flows between the beads minimizes partial volume effects and facilitates the correction of the phenomenon of phase aliasing. On the other hand, the measurement of average interstitial velocity (Darcy) requires using simultaneous velocity image and porosity image. In this case, it is preferable to adjust the strength of magnetic field gradient in the velocimetry sequence in a way to avoid any phase aliasing. The geometry of the flow cell was chosen to enable comparison by the MRI method between volume flow rates of water in the porous media and in the outer annulus., Cette étude présente la mise au point de mesures de porosité et de vitesse d'écoulement faites par IRM dans des colonnes de billes de verre et de polymère de différentes granulométries saturées en eau. L'avantage des billes en polymère est qu'elles ne contiennent pas d'éléments ferro ou paramagnétiques, contrairement aux billes de verre qui perturbent le champ magnétique créant des artéfacts sur les images IRM. La séquence d'IRM utilisée pour l'étude des écoulements en milieu poreux a été préalablement paramétrée à l'aide d'une étude sur un écoulement de Poiseuille. Deux situations ont été examinées : d'une part, l'observation des écoulements interstitiels entre les billes permet de minimiser les effets de volume partiel et de faciliter la correction du phénomène de repliement de phase. D'autre part, la mesure de vitesses moyennes (Darcy) nécessite d'utiliser simultanément les images de vitesse et les images de porosité. Dans ce cas, il est préférable d'ajuster la puissance des gradients d'encodage de vitesse de façon à éviter tout phénomène de repliement de phase. La géométrie du dispositif utilisé a permis une comparaison rigoureuse des mesures de débit de façon intrinsèque uniquement par IRM (débit en milieu poreux et dans l'espace annulaire) et aussi à partir de la mesure directe du débit (pesée).

This numerical study deals with the inverse problem of estimating the intensity and the positionof a pollutant source. The estimation of time-varying emission rates of pollutant sources of H2S in asewer chamber is first implemented through inversion of concentration measurements using the modal identification method. A specific method based on transmittance functions between sensors output isused to estimate the source position. Regularization tools are applied to estimate each transmittance,whose convolution product with the concentration of a reference sensor models the response of any sensor.Transmittances estimated from simulated concentration signals in a tunnel flow with a point source arethen compared to the output of 1D analytical model for the transport equation. A nonlinear minimizationalgorithm is used to estimate the velocity and the diffusion coefficient first and the source position next,under some assumption; Cette étude est consacrée au problème inverse d'estimation de l'intensité et de la position d'une source de polluant. Nous inversons tout d'abord des mesures de concentration à l'intérieur d'une chambre à sable(extension des égouts souterrain) en utilisant la méthode d'identification modale pour estimer l'intensité d'émission du gaz H2S. Une approche originale est ensuite proposée pour estimer la position d'une source en utilisant la notion de transmittance entre deux capteurs. Des outils de régularisation sont utilisés afin d'estimer chaque transmittance, dont le produit de convolution avec la concentration d'un capteur choisi comme référence correspond à la réponse d'un capteur quelconque. Les transmittances estimées à partir des signaux de concentration simulés dans une configuration d'un écoulement tunnel avec source ponctuelle sont ensuite comparées à la sortie d'un modèle analytique 1D de l'équation de transport.L'utilisation d'un algorithme de minimisation non linéaire a permis d'estimer d'abord la vitesse et le coefficient de diffusion de l'écoulement et ensuite la position de la source, sous certaines hypothèses

In a pressurized water reactor (PWR), during a Loss Of Coolant Accident (LOCA), liquid water evaporates and the fuel assemblies are not cooled anymore; as a consequence, the temperature rises to such an extent that some parts of the fuel assemblies can be deformed resulting in "ballooned regions". When reflooding occurs, the cooling of these partially blocked parts of the fuel assemblies will depend on the coolant flow that is a mixture of overheated vapour and undersaturated droplets. The aim of this thesis is to study the heat transfer between droplets and hot walls of the fuel rods. In this purpose, an experimental device has been designed in accordance with droplets and wall features (droplet velocity and diameter, wall temperature) representative of LOCA conditions. The cooling of a hot Nickel disk, previously heated by induction, is cooled down by a stream of monodispersed droplet. The rear face temperature profiles are measured by infrared thermography. Then, the estimation of wall heat flux is performed by an inverse conduction technique from these infrared images. The effect of droplet dynamical properties (diameter, velocity...) on the heat flux is studied. These experimental datas allow us to validate an analytical model of heat exchange between droplet and hot slab. This model is based on combined dynamical and thermal considerations. On the one hand, the droplet dynamics is considered through a spring analogy in order to evaluate the evolution of droplet features such as the spreading diameter when the droplet is squeezed over the hot surface. On the other hand, thermal parameters, such as the thickness of the vapour cushion beneath the droplet, are determined from an energy balance. In the short term, this model will be integrated in a CFD code (named NEPTUNE_CFD) to simulate the cooling of a reactor core during a LOCA, taking into account the droplet/wall heat exchange., Au cours d'un transitoire d'Accident de Perte de Réfrigérant Primaire (APRP), la vaporisation de l'eau dans la cuve d'un réacteur nucléaire conduit à l'assèchement et à l'augmentation de la température des crayons de combustible, à leur gonflement thermomécanique et à la rupture des gaines de ces crayons remplies de matériaux combustibles fragmentés. Ce gonflement peut être à l'origine d'un bouchage significatif d'une partie du coeur et compromettre ainsi son refroidissement lors de la phase de renoyage où l'eau injectée via les systèmes de sécurité pénètre dans le bas du coeur. Lors de cette phase de renoyage, la vaporisation importante de l'eau produit un fort débit de vapeur qui arrache et entraîne des gouttelettes dans les zones bouchées. L'enjeu de cette thèse est d'évaluer les capacités de refroidissement des crayons ballonnés par l'impact des gouttes d'eau. Pour ce faire, une étude expérimentale est réalisée au LEMTA de Nancy, afin de mesurer le flux de refroidissement d'un train de gouttes impactant une paroi chaude. L'influence des caractéristiques dynamiques des gouttes sur le flux échangé entre la goutte et la paroi est expérimentalement étudiée. Ces essais ont permis la réalisation d'une base de donnée permettant de valider un modèle de flux goutte/paroi Ce modèle d'échange goutte/paroi est réalisé à partir d'une modélisation des paramètres clefs gouvernant l'échange, à savoir, le diamètre d'étalement de la goutte sur la paroi, l'épaisseur de la couche de vapeur créée sous la goutte et le temps de séjour de la goutte sur la paroi. Ce modèle, validé expérimentalement, est intégré dans le code NEPTUNE_CFD dans le but de réaliser des simulations de refroidissement d'un assemblage de crayon, en phase de renoyage, en prenant en compte l'effet des gouttes impactantes.

This numerical study deals with the inverse problem of estimating the intensity and the positionof a pollutant source. The estimation of time-varying emission rates of pollutant sources of H2S in asewer chamber is first implemented through inversion of concentration measurements using the modal identification method. A specific method based on transmittance functions between sensors output isused to estimate the source position. Regularization tools are applied to estimate each transmittance,whose convolution product with the concentration of a reference sensor models the response of any sensor.Transmittances estimated from simulated concentration signals in a tunnel flow with a point source arethen compared to the output of 1D analytical model for the transport equation. A nonlinear minimizationalgorithm is used to estimate the velocity and the diffusion coefficient first and the source position next,under some assumption, Cette étude est consacrée au problème inverse d'estimation de l'intensité et de la position d'une source de polluant. Nous inversons tout d'abord des mesures de concentration à l'intérieur d'une chambre à sable(extension des égouts souterrain) en utilisant la méthode d'identification modale pour estimer l'intensité d'émission du gaz H2S. Une approche originale est ensuite proposée pour estimer la position d'une source en utilisant la notion de transmittance entre deux capteurs. Des outils de régularisation sont utilisés afin d'estimer chaque transmittance, dont le produit de convolution avec la concentration d'un capteur choisi comme référence correspond à la réponse d'un capteur quelconque. Les transmittances estimées à partir des signaux de concentration simulés dans une configuration d'un écoulement tunnel avec source ponctuelle sont ensuite comparées à la sortie d'un modèle analytique 1D de l'équation de transport.L'utilisation d'un algorithme de minimisation non linéaire a permis d'estimer d'abord la vitesse et le coefficient de diffusion de l'écoulement et ensuite la position de la source, sous certaines hypothèses

Thermal control for chemical reactions conducted in fixed-bed reactors requires a fine knowledge about heat transfer in the near-wall region of the bed. In order to optimize the process design, to minimize the mass of catalyst that is needed, one must attempt to maintain the operational path of the reactor the closest of the isotherm functioning. A pertinent and reliable heat transfer model is then required. Two thesis were realized in the Laboratoire d'Energétique et de Mécanique Théorique et Appliquée in order to construct a corresponding dispersive model. This model can be used at the core of the reactor, where the porous medium can be homogenized. This thesis shows a wall effect that cannot be neglected. This wall effect is directly caused by the important variation of the porosity distribution near the wall of the bed. This work proposes a junction between a core layer, where the previous model is still valid, and the wall through an homogenized near-wall layer. This approach is validated by the mean of an experimental characterization of the model parameters, using an original inversion technique based on a Bayesian approach. A validation of this characterization in another geometry is also done. This geometry is closer to an industrial reactor; Le contrôle thermique des réactions dans les réacteurs à lits fixes nécessite la maîtrise du transfert thermique en proche paroi. Afin d'optimiser leur conception et en particulier de maintenir un chemin réactionnel le plus proche possible de l'isothermicité, un modèle de transfert thermique pertinent dans un tel milieu est indispensable. Deux premières thèses au Laboratoire d'Energétique et de Mécanique Théorique et Appliquée ont permis de mettre au point un modèle dispersif utilisable à coeur de réacteur. La présente thèse met en évidence un effet de paroi non négligeable causé par la variation de porosité du lit à l'approche de la paroi. Ce travail propose un raccordement du coeur, où le modèle thermique précédent est légitime, à la paroi, par une couche homogénéisée. Cette approche est validée par une caractérisation expérimentale des paramètres du modèle sur un dispositif de laboratoire en utilisant une méthode d'inversion originale reposant sur une approche Bayesienne. Une validation de cette caractérisation dans une géométrie plus proche d'un réacteur industriel est également effectuée

Thermal control for chemical reactions conducted in fixed-bed reactors requires a fine knowledge about heat transfer in the near-wall region of the bed. In order to optimize the process design, to minimize the mass of catalyst that is needed, one must attempt to maintain the operational path of the reactor the closest of the isotherm functioning. A pertinent and reliable heat transfer model is then required. Two thesis were realized in the Laboratoire d'Energétique et de Mécanique Théorique et Appliquée in order to construct a corresponding dispersive model. This model can be used at the core of the reactor, where the porous medium can be homogenized. This thesis shows a wall effect that cannot be neglected. This wall effect is directly caused by the important variation of the porosity distribution near the wall of the bed. This work proposes a junction between a core layer, where the previous model is still valid, and the wall through an homogenized near-wall layer. This approach is validated by the mean of an experimental characterization of the model parameters, using an original inversion technique based on a Bayesian approach. A validation of this characterization in another geometry is also done. This geometry is closer to an industrial reactor, Le contrôle thermique des réactions dans les réacteurs à lits fixes nécessite la maîtrise du transfert thermique en proche paroi. Afin d'optimiser leur conception et en particulier de maintenir un chemin réactionnel le plus proche possible de l'isothermicité, un modèle de transfert thermique pertinent dans un tel milieu est indispensable. Deux premières thèses au Laboratoire d'Energétique et de Mécanique Théorique et Appliquée ont permis de mettre au point un modèle dispersif utilisable à coeur de réacteur. La présente thèse met en évidence un effet de paroi non négligeable causé par la variation de porosité du lit à l'approche de la paroi. Ce travail propose un raccordement du coeur, où le modèle thermique précédent est légitime, à la paroi, par une couche homogénéisée. Cette approche est validée par une caractérisation expérimentale des paramètres du modèle sur un dispositif de laboratoire en utilisant une méthode d'inversion originale reposant sur une approche Bayesienne. Une validation de cette caractérisation dans une géométrie plus proche d'un réacteur industriel est également effectuée

Understanding and modelling of coupled mass, charges and heat transfers phenomena are fundamental to analyse the electrical behaviour of the system. The aim of the present model is to describe electrical performances of a PEFMC according to the fluidic and thermal operating conditions. The water content of the membrane and the water distribution in the single cell are estimated according to the coupled simulations of mass transport in the thickness of the single cell and in the feeding channels of the bipolar plates. A microscopic model of a Gas Diffusion Electrode is built up to describe charges transfer phenomena occurring at the electrodes. Completed by a study of heat transfer in the Membrane Electrode Assembly, conditions and preferential sites of water vapour condensation can be highlighted. A set of measurements of the effective thermal conductivity of carbon felts used in fuel cells as porous backing layers have also been performed. Although the value of this parameter is essential for the study of heat transfer, it is still under investigation because of the strong thermal anisotropy of the medium, La compréhension et la description des phénomènes couplés de transport de masse, de charge et de chaleur dans le c?ur de pile sont primordiales pour l'analyse du comportement électrique du système. Le modèle présenté ici a pour objectif de décrire les performances électriques d'une pile PEMFC en fonction des conditions fluidiques et thermiques de fonctionnement. L'hydratation de la membrane et la répartition de l'eau dans la cellule sont estimées à l'aide de simulations couplées du transport de matière dans l'épaisseur de la cellule et dans les canaux d'alimentation internes aux plaques bipolaires. Un modèle microscopique de type Gas Diffusion Electrode a été mis en place pour décrire les phénomènes de transfert de charges aux électrodes. Complétée par l'étude du transfert de chaleur dans le c?ur de pile, cette modélisation permet notamment de distinguer les conditions et les sites préférentiels de condensation de la vapeur d'eau. Une campagne de mesures de la conductivité thermique effective des feutres de carbone utilisés en pile en tant que diffuseur poreux a également été réalisée. La valeur de ce paramètre, bien qu'essentielle pour l'étude des transferts thermiques, est encore source de discussions du fait de la forte anisotropie thermique du milieu

Non disponible / Not available; Le contrôle thermique est un point clef de la conception des équipements électroniques. En effet les caractéristiques de fonctionnement des composants et la fiabilité des systèmes dépendent fortement de la température. Nous avons développé un outil de modélisation des transferts de chaleur dans les composants électroniques de puissance qui permet d'optimiser leur structure d'un point de vue thermique. Ses performances en terme de temps de calcul permettent cette optimisation sans avoir recours à des modèles réduits. La méthode ne nécessite pas de maillage de la structure et son caractère analytique en fait une méthode adaptée à la caractérisation expérimentale des composants. Le premier chapitre est consacré à la mise en place des outils de modélisation thermique de structures à géométrie multibloc, c'est-à-dire de structures composées d'empilements pyramidaux de blocs parallélépipédiques, géométries caractéristiques des composants électroniques de puissance. Le deuxième chapitre est centré sur la validation et l'estimation des performances de la méthode. La simulation thermique d'un module IGBT (lnsulated Gate Bipolar Transistor) est réalisée. Une procédure de conception optimale d'un diffuseur est proposée. La faisabilité de la prise en compte par la méthode des quadripôles thermiques du couplage entre un canal fluide et ses parois solides, ou de la modélisation d'un radiateur à ailettes, est également démontrée. Le troisième et dernier chapitre est consacré à la mise au point d'outils de caractérisation d'empilements, de métrologie de température sur les IGBTs et de fluxmètrie par conduction inverse. Une procédure de mesure de température sur la surface d'un composant est également mise au point. La mesure est réalisée par thermographie infrarouge, phosphorescence induite U.V. et par l'intermédiaire d'un paramètre thermosensible afin de procéder à la cartographie des émissivités. La perspective d'utiliser un composant électronique comme fluxmètre est également envisagée.

Non disponible / Not available, Le contrôle thermique est un point clef de la conception des équipements électroniques. En effet les caractéristiques de fonctionnement des composants et la fiabilité des systèmes dépendent fortement de la température. Nous avons développé un outil de modélisation des transferts de chaleur dans les composants électroniques de puissance qui permet d'optimiser leur structure d'un point de vue thermique. Ses performances en terme de temps de calcul permettent cette optimisation sans avoir recours à des modèles réduits. La méthode ne nécessite pas de maillage de la structure et son caractère analytique en fait une méthode adaptée à la caractérisation expérimentale des composants. Le premier chapitre est consacré à la mise en place des outils de modélisation thermique de structures à géométrie multibloc, c'est-à-dire de structures composées d'empilements pyramidaux de blocs parallélépipédiques, géométries caractéristiques des composants électroniques de puissance. Le deuxième chapitre est centré sur la validation et l'estimation des performances de la méthode. La simulation thermique d'un module IGBT (lnsulated Gate Bipolar Transistor) est réalisée. Une procédure de conception optimale d'un diffuseur est proposée. La faisabilité de la prise en compte par la méthode des quadripôles thermiques du couplage entre un canal fluide et ses parois solides, ou de la modélisation d'un radiateur à ailettes, est également démontrée. Le troisième et dernier chapitre est consacré à la mise au point d'outils de caractérisation d'empilements, de métrologie de température sur les IGBTs et de fluxmètrie par conduction inverse. Une procédure de mesure de température sur la surface d'un composant est également mise au point. La mesure est réalisée par thermographie infrarouge, phosphorescence induite U.V. et par l'intermédiaire d'un paramètre thermosensible afin de procéder à la cartographie des émissivités. La perspective d'utiliser un composant électronique comme fluxmètre est également envisagée.

Heat transfer in a granular media through which a fluid is flowing is called thermal dispersion. It results from a combination of diffusive and convective heat transfer. The control of thermal dispersion is a critical point each time strongly endo- or exothermic chemical reaction in heterogeneous catalysis occurs. In this type of situation the control of the chemical conversion and/or of the lifespan of the catalyst is of prime importance. This work relates to the experimental characterization of thermal dispersion in granular media first in the core region and then in the near-wall region. In the first part of this work, a bed made up of granular medium (glass spheres or catalyst support) has been constructed. An air flow produced by a downstream fan goes through this bed. The bed is heated by Joule effect (time step) thanks to a metal wire perpendicular to the flow. The transient temperature responses are measured by several thermocouples. A specific inversion technique makes the estimation of the two thermal dispersion coefficients possible. Experimental correlations explaining the variation of the lateral and longitudinal dispersion coefficients with fluid velocity have been constructed on dimensional analysis considerations. They derive from the measurements on the glass beads/air and support of catalyst/nitrogen systems (use of dry nitrogen allows to get rid of the hygrophilic character of the micro-porous grains). The last part of this work relates to study of the thermal effects in the near wall region (effects caused by the hydrodynamic channelling phenomena). A new experimental set-up, with heating by a plane foil resistance on the wall and thermocouples inserted in the granular medium, has been built. Temperature measurements highlights the wall-effects. A new analytical model, that will make simulations of a two layers porous medium (core and near-wall regions) has been developed, Le transfert de chaleur dans un milieu granulaire traversé par un fluide est appelé dispersion thermique. Celle-ci résulte d'une combinaison des transferts diffusif et convectif de la chaleur. La maîtrise de la dispersion thermique est essentielle lorsqu'on effectue des réaction chimiques en catalyse hétérogène fortement endo ou exothermique. Dans ce type de situation il est en effet primordial de contrôler la conversion chimique et/ou la durée de vie d'un catalyseur. Ce travail concerne la caractérisation expérimentale de la dispersion thermique dans les milieux granulaires, d'abord à c?ur puis en proche paroi. Dans la première partie du travail, un banc constitué d'une enceinte parallélépipédique remplie d'un milieu granulaire (bille de verre ou grains de support de catalyseur) a été construit. Il est traversé par un écoulement d'air assuré par un ventilateur situé en aval du banc. Le lit est chauffé par effet Joule (échelon temporel) grâce à un fil métallique perpendiculaire à l'écoulement. La réponse transitoire en température est mesurée par plusieurs thermocouples. Une technique d'inversion spécifique permet d'estimer les deux coefficients de dispersion thermique. Des corrélations expérimentales, basées sur une analyse dimensionnelle, ont été établies pour expliquer les variations avec la vitesse des coefficients de dispersion longitudinal et transverse. Celles-ci découlent de nos mesures sur les systèmes billes de verre/air et support de catalyseur azote (l'azote sec permet de s'affranchir des problèmes d'hygrophilie des grains qui sont eux-mêmes dotés d'une microporosité interne). Le dernier volet de ce mémoire concerne l'étude des effets thermiques en proche paroi (effets liés aux survitesses). Un nouveau banc expérimental, avec chauffage par une résistance pelliculaire plane implantée sur la paroi et thermocouples insérés dans le milieu granulaire, a été mis en place et une campagne de mesure a permis de mettre en évidence les effets de paroi. Un nouveau modèle analytique, qui doit permettre des simulation de dispersion sur un lit composé de deux couches (à c?ur et en proche paroi), a également été développé

Non disponible / Not available, La dispersion thermique, c'est-à-dire le transfert de chaleur dans un milieu poreux qui est traversé par un fluide, est un phénomène complexe. Pour que celui-ci puisse être pris en compte dans des applications industrielles, il faut disposer d'un modèle simple avec des paramètres qui sont physiquement raisonnables et expérimentalement accessibles. Ce travail présente une technique expérimentale pour estimer les paramètres du modèle dit "à une température", notamment les coefficients du tenseur de dispersion thermique qui dépendent de la vitesse de Darcy. Le dispositif expérimental correspond à un lit fixe de billes de verre avec de l'eau comme fluide. Une source de chaleur linéique, perpendiculaire à la direction de l'écoulement, est utilisée (échelon temporel) ; le signal de température, mesuré par des thermocouples en aval de la source, est utilisé pour l'estimation des paramètres. Dans cette situation, la qualité d'estimation par la méthode des moindres carrés ordinaires est limitée par les incertitudes sur la vitesse et les positions des thermocouples. L'optimisation de la géométrie expérimentale et la méthode de Gauss-Markov permettent d'estimer également ces paramètres. Des simulations d'inversion de type Monte-Carlo montrent que cette approche fournit une estimation du coefficient longitudinal de dispersion thermique avec une bonne précision; d'autres géométries de chauffe et les travaux de la littérature confirment ces résultats. L'estimation du coefficient de dispersion transverse est moins précise; cependant, les résultats obtenus pour sa dépendance de la vitesse mettent en cause le modèle établi de la littérature. Les excellents résidus en température qui ont été obtenus suggèrent que le modèle à une température est raisonnable, même dans le cas du non-équilibre thermique entre les deux phases.

Non disponible / Not available, L'objet de cette étude est de déterminer la diffusivité phonique de milieux semi-transparents. La première partie concerne la mise en place de modèles semi-analytiques permettant de prédire le transfert de chaleur transitoire couplé conduction-rayonnement dans un milieu semi-transparent absorbant, émettant et éventuellement diffusant de façon anisotrope le rayonnement. Un large éventail de fonctions de phase (linéaire anisotrope; de Rayleigh, du second ordre, pics intenses), de conditions aux limites (Dirac de flux, échelons de température) et de parois (noires ou en or) est considéré. La seconde partie teste la pertinence des modèles couplés pour l'inversion dans le cas de la méthode flash afin de déterminer quels paramètres thermophysiques et radiatifs peuvent être identifiés. Une étude stochastique basée sur des cartographies des maxima de sensibilité, des coefficients de corrélation et des écarts-types relatifs aux différents paramètres est complétée par des considérations expérimentales .. Les biais causés par une erreur sur l'émissivité des parois, le caractère non gris et une éventuelle anisotropie de la diffusion ont été considérés les résultats sont confrontés à ceux obtenus avec la méthode "classique" des parois en or. La troisième partie présente des résultats expérimentaux obtenus dans le cadre de la méthode flash pour différents échantillons semi-transparents l verre flotté, pastilles de silice et de séléniure de zinc. Les mesures ont été effectuées par voie optique (détecteur infrarouge Hg Cd Te) pour une large plage de température variant de l'ambiante à 700K, pour différents types de parois (noires et en or) et pour différentes épaisseurs. Cette étude constitue une avancée dans l'estimation de la diffusivité phonique de matériaux semitransparents. Elle fournit une méthodologie complète et rigoureuse de la mesure de diffusivité et remplace avantageusement la méthode des parois en or (moins coûteuse, plus rapide, plus précise).