Characterization method of dielectric properties of free falling drops in a microwave processing cavity and its application in microwave internal gelation

[EN] Microwave internal gelation (MIG) is a chemical process proposed for the production of nuclear particle fuel. The internal gelation reaction is triggered by a temperature increase of aqueous droplets falling by gravity by means of non-contact microwave heating. Due to the short residence time of a solution droplet in a microwave heating cavity, a detailed knowledge of the interaction between microwaves and chemical solution (shaped in small drops) is required. This paper describes a procedure that enables the measurement of the dielectric properties of aqueous droplets that freely fall through a microwave cavity. These measurements provide the information to determine the optimal values of the parameters (such as frequency and power) that dictate the heating of such a material under microwaves.This work is a part of the PINE (Platform for Innovative Nuclear FuEls) project which targets the development of an advanced production method for Sphere-Pac fuel and is financed by the Swiss Competence Center for Energy and Mobility. The work has been also financed by the European Commission through contract no 295664 regarding the FP7 PELGRIMM Project, as well as contract no 295825 regarding the FP7-ASGARD Project. MC-S would like to thank the ITACA research team (UPV Valencia, Spain) and the EMPA Thun (Switzerland) for their support in the measurements and Carl Beard (PSI, Switzerland) for the help provided in respect with CST simulations. The work of FLP-F was supported by the Conselleria d'Educacio of the Generalitat Valenciana for economic support (BEST/2012/010).Cabanes Sempere, M.; Catalá Civera, JM.; Penaranda-Foix, FL.; Cozzo, C.; Vaucher, S.; Pouchon, MA. (2013). Characterization method of dielectric properties of free falling drops in a microwave processing cavity and its application in microwave internal gelation. Measurement Science and Technology. 24(9). https://doi.org/10.1088/0957-0233/24/9/095009S24

Conservação e restauro de uma urna em vidro do século I d.C., encontrada em Mértola (Portugal)

International audienceThe evolution of capillary forces during evap-oration and the corresponding changes in the geometrical characteristics of liquid (water) bridges between two glass spheres with constant separation are examined experimen-tally. For comparison, the liquid bridges were also tested for mechanical extension (at constant volume). The obtained results reveal substantial differences between the evolution of capillary force due to evaporation and the evolution due to extension of the liquid bridges. During both evaporation and extension, the change of interparticle capillary forces consists in a force decrease to zero either gradually or via rupture of the bridge. At small separations between the grains (short & wide bridges) during evaporation and at large volumes during extension, there is a slight initial increase of force. During evaporation, the capillary force decreases slowly at the begin-ning of the process and quickly at the end of the process; during extension, the capillary force decreases quickly at the beginning and slowly at the end of the process. Rup-ture during evaporation of the bridges occurs most abruptly for bridges with wider separations (tall and thin), sometimes occurring after only 25 % of the water volume was evapo-rated. The evolution (pinning/depinning) of two geometri-cal characteristics of the bridge, the diameter of the three-phase contact line and the "apparent" contact angle at the solid/liquid/gas interface, seem to control the capillary force evolution. The findings are of relevance to the mechanics of unsaturated granular media in the final phase of drying

Emulsion processing - From single-drop deformation to design of complex processes and products

The processing of complex emulsion systems is described in four main chapters which relate to the basic mechanisms of (i) single-drop deformation and breakup in laminar and turbulent flow fields; (ii) the impact of drop interactions in concentrated multi-drop systems on deformation, breakup and networking; (iii) the design of drop dispersing apparatus; and (iv) the relationship of disperse emulsion structure and product quality characteristics. For these chapter topics milestones archived during the past decades since the 1930s are highlighted. Among the most recent developments, experimental, modeling and numerical simulation tools are demonstrated to allow for complementary approaches with high potential for deriving optimized process and product design criteria. © 2005 Elsevier Ltd. All rights reserved