Control of pool boiling incipience in confined space: dynamic morphing of the wall effect

This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.A new active heat transfer enhancement and control technique is proposed in this work. One of the major aims of the technique is to decrease pool boiling incipience temperature by dynamic morphing imposed to confinement wall. Dynamic deformation generates variation of pressure which increases the fluid metastability level. An experimental device was built to evaluate boiling incipience temperature. Experimental results were compared with hydrodynamic and nucleation models.CNRS Energie CITAMPE PR09-3.1.3-2 and FNRAE SYRTIP

Pumping and heat transfer enhancement by wall's morphing

In a previous study, heat transfer enhancement using a deformable wall in a heat exchanger was demonstrated numerically using CFD calculations in liquid single-phase situation. This configuration allows the pumping function to be integrated within the heat exchanger itself. Based on these results, a prototype has been developed (but with different dimensions than in the numerical study) in which one of the walls constituting the channel is subjected to dynamic deformations in the form of a traveling wave. Electric heaters on the other wall heat the channel. Actuation is achieved by means of piezoelectric actuators. Experimentally, the pumping function is observed, for all frequencies of deformations and for two different fluids (water and HFE 7000). The heat transfer intensification is also shown, and this in two experimental configurations: - a pressure difference (which may be zero) between the inlet and outlet of the channel is imposed: in this configuration, the traveling wave imposes the flow-rate. The heat transfer enhancement is then due both to the increase of the flow-rate and the disruption of the thermal boundary layers generated by the wave; - a flow-rate is imposed with a mechanical pump: in this case actuation has no effect on the pumping, and the measured heat transfer enhancement is then due only to the effects of the imposed dynamic deformations. First experiments with the presence of boiling were also performed. It was found that boiling can occur even if the fluid does not reach the saturation temperature within the channel. A 100% increase in the mean heat transfer coefficient was found when actuating the channel wall.Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016

The culture history of Madagascar

Madagascar's culture is a unique fusion of elements drawn from the western, northern, and eastern shores of the Indian Ocean, and its past has fascinated many scholars, yet systematic archaeological research is relatively recent on the island. The oldest traces of visitors are from the first century AD. Coastal settlements, with clear evidence of ties to the western Indian Ocean trading network, were established in several places over the next millennium. Important environmental changes of both plant and animal communities are documented over this period, including the extinctions of almost all large animal species. Urban life in Madagascar began with the establishment of the entrepôt of Mahilaka on the northwest coast of the island in the twelfth century. At about the same time, communities with ties to the trade network were established around the island's coasts. From the fourteenth to the sixteenth century, social hierarchies developed in several regions of the island. During the succeeding two centuries, Madagascar saw the development of state polities.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45256/1/10963_2004_Article_BF00997802.pd

Chaine d'information au service des territoires

National audienceExemples de modèles organisationnels et économiques en matière de chaînes d'information au service des territoires

Étude d'une source d'ions de basse énergie et à forte densité de courant

An ion source of low energy (from 5 to 100 electron-volts) has been carried out. The extracted ion current density is higher than what has been obtained so far in this energy range. The extraction system is made of a thin mesh grid. The holes dimension is smaller than the sheath thickness in the ionization chamber.Une source d'ions de basse énergie (entre 5 et 100 électrons-volts) a été mise au point. La densité du courant d'ions extrait est supérieure à ce qui a été obtenu jusqu'ici dans cette gamme d'énergie. Le système d'extraction est constitué d'une grille à maille très fine. La dimension des trous est inférieure à l'épaisseur de gaine dans la chambre d'ionisation

CARACTÉRISATION DU PLASMA DANS UNE DÉCHARGE CONTRÔLÉE PAR FAISCEAU D'ÉLECTRONS

Les paramètres macroscopiques des plasmas de laser à CO2 sont calculés en fonction du champ électrique. Le coefficient de recombinaison est mesuré. Une approximation donnant le terme d'ionisation en fonction des caractéristiques du faisceau est proposée. L'ensemble du diagnostic donne des résultats cohérents.Macroscopic properties of CO2 laser plasmas are computed as functions of the electric field. The recombination coefficient is measured. An approximation relating the ionisation rate with the beam properties is given. The whole diagnostics yields self-consistent results

Etude dans la série des pyrrolidinones. IV. Formation de quelques dérivés de l'acide L méthylène bis N‐(oxo‐5 pyrrolidine carboxylique‐2)

En partant de l'acide oxo‐5 pyrrolidine carboxylique‐2 facilement accessible, le diacide L méthylène bis N‐(oxo‐5 pyrrolidine carboxylique‐2) est préparé, et transformé en diamine puis en deux diols isomères, qui se cyclisent en un seul ether à qui la configuration méso est attribuée. La réduction des deux diols et de l'éther est totale et conduit à la méthylène bis N‐pyrrolidine. Copyright © 1980 Journal of Heterocyclic Chemistr

Control of pool boiling incipience in confined space: Dynamic morphing of the wall effect

International audienceA new active heat transfer enhancement and control technique is proposed in this work. One of the major aims of the technique is to decrease pool boiling incipience temperature by dynamic morphing imposed to confinement wall. Dynamic deformation generates variation of pressure which increases the fluid metastability level. An experimental device was built to evaluate boiling incipience temperature. Experimental results were compared with hydrodynamic and nucleation models. (C) 2012 Elsevier Ltd. All rights reserved

Reprint of ``Control of pool boiling incipience in confined space: Dynamic morphing of the wall effect''

International audienceA new active heat transfer enhancement and control technique is proposed in this work. One of the major aims of the technique is to decrease pool boiling incipience temperature by dynamic morphing imposed to confinement wall. Dynamic deformation generates variation of pressure which increases the fluid metastability level. An experimental device was built to evaluate boiling incipience temperature. Experimental results were compared with hydrodynamic and nucleation models. (C) 2013 Elsevier Ltd. All rights reserved