A nonparametric model for sensors used in a dynamic context

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L'effet piston en milieu poreux

Ce travail vise à étudier les mécanismes de transfert de masse et de chaleur au sein d'un fluide pur, au voisinage de son point critique, lorsque celui-ci sature une matrice poreuse. Hors milieu poreux. L'étude hydrodynamique et thermique des fluides supercritiques en absence de gravité et maintenus à volume constant, a mis en évidence une « accélération critique » du transport de chaleur par effet piston. Cet effet a pour conséquence une thermalisation très rapide et homogène du volume de fluide. L'impact d'un milieu poreux homogène et indéformable sur le devenir de l'effet piston est l'objet de ce travail. Une partie simulation numérique porte sur la vérification d'un modèle théorique proposé pour décrire les régimes de propagation de la chaleur. Une partie expérimentale présente, quant à elle, la réalisation d'une cellule instrumentée correspondant à la situation d'étude et des mesures tests réalisées au sein de celle-ci

Towards improved humidity measurements at high temperatures and transient conditions

Humidity is a key parameter in controlling drying processes and ambient conditions in many industrial manufacturing, storage and test applications. Air humidity is routinely measured at temperatures above 100 °C and at conditions that are often challenging due to temporal and local variations. Calibrations of humidity sensors do not provide appropriate representativeness of measurement conditions because they are limited to temperatures below 100 °C and static conditions. A European metrology research project HIT (“Metrology for Humidity at High Temperatures and Transient conditions”) is developing improved humidity measurement and calibration techniques to temperatures up to 180 °C and non-static conditions. This paper summaries developments of the project: calibration and test facilities for industrial hygrometers, studies on humidity control in specific microbial transient processes and a new measurement approach for water activity measurements

Response time measurement of hygrometers at LNE-CETIAT

LNE-CETIAT has been involved in European project JRP HIT – EMPIR (www.empir-hit.e

« De l’achat de la collection Campana à Courbet, quelques opposants au Second Empire dans le monde artistique »

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Etude de l'effet piston au sein d'un fluide supercritique en milieux poreux

Ce travail de thèse vise à étudier les mécanismes de transfert de masse et de chaleur au sein d'un fluide pur, au voisinage de son point critique, lorsque celui-ci sature une matrice poreuse. Hors milieu poreux, l'étude hydrodynamique et thermique des fluides supercritiques en absence de gravité et maintenu à volume constant, a mis en évidence une "accélération critique" du transport de chaleur par effet piston. Cet effet a pour conséquence une thermalisation très rapide et homogène du volume de fluide. L'impact d'un milieu poreux homogène et indéformable sur le devenir de l'effet piston est l'objet de ce travail. Une partie simulation numérique porte sur la vérificationd'un modèle théorique proposé pour décrire les régimes de propagation de la chaleur. Une patrie expérimentale présente, quant à elle, la réalisation d'une cellule instrumentée correspondant à la situation d'étude et des mesures tests réalisées au sein de celle-ci.BORDEAUX1-BU Sciences-Talence (335222101) / SudocSudocFranceF

Silicone tube humidity generator

<p>We describe the model and construction of a two-flow (or divided-flow) humidity generator, developed at LNE-Cnam, that uses mass flow controllers to mix a stream of dry gas with a stream of humid gas saturated at 28 ◦C. It can generate a wide range of humidity, with mole fractions in the range of 0.7×10−6 < x < 9000×10−6 , without using low temperature or high pressure. This range is suitable for calibrating balloon-borne instruments that measure humidity in the stratosphere, where x ∼ 5 × 10−6 . The generator's novel feature is a saturator that comprises 5 m of silicone tubing immersed in water. Water enters the humid gas stream by diffusing through the wall of the tubing until the gas stream flowing through the tubing is saturated. This design provides a simple, low-cost humidity generator with an accuracy that is acceptable for many applications. The key requirement is that the tubing be long enough to ensure saturation so that the saturator's output is independent of the dimensions and permeability of the tube. A length of only a few meters was sufficient because the tube was made of silicone; other common polymers have permeabilities that are 1000 times smaller. We verified the model of the transition from unsaturated flow to saturated flow by measuring the humidity while using three tube lengths, two of which were too short for saturation. As a more complete test, we used the generator as a primary device after correcting the calibrations of the mass flow controllers that determined the mixing ratio. At mole fractions of 50×10−6 < x < 5000×10−6 , the generator's output mole fraction xgen agreed to within 1 % with the value xcm measured by a calibrated chilled-mirror hygrometer; in other words, their ratio fell in the range xgen/xcm = 1.00±0.01. At smaller mole fractions, their differences fell in the range of xgen − xcm = ±1 × 10−6 .</p><p>Financial support. This research has been supported by the EURAMET (grant no. ENV07 METEOMET, grant no. ENV58 METEOMET2, and grant no. 20IND06 PROMETH2O)</p&gt

New calibration facility developped at LNE-CETIAT

LNE-CETIAT has developed its own primary realization of the unit in humidity. Willing to have a more versatile generator, the laboratory has developed a new humid air generator based on dilution principle. These facilities are presented in this work as well as the results of two comparisons

Best Practice for Characterisation of Calibration Furnaces

The CETIAT thermometry calibration laboratory has a wide range of temperature generators. Overflow baths, dry furnaces, furnaces as well as thermostatic chambers make it possible to achieve a temperature range from −90 °C to 1050 °C. Experience gained over more than ten years enables the teams to identify possible measurement difficulties. The thermal characterisation of portable furnaces is identified as risks in measurement errors. The diversity of CETIAT’s calibration tools makes it possible to highlight these risks and to find solutions for them. Only a few documents deal with the characterisation of portable furnaces. The EURAMET guide “cg-13 form 3.0 (02/2015)” provides some elements. This lack of information on implementation in temperature calibration furnaces can lead to significant calibration errors. A calibration performed in a thermostated bath or dry furnace will give different results in both the correction and the associated uncertainty. The difference in the results obtained is such that the corrections do not overlap, even when taking into account the associated uncertainties. There is also the effect of the environment on the results. This study allows users of portable furnaces to reduce measurement errors due to poor implementation