Investigation of suitability of the method of volume averaging for the study of heat transfer in superconducting accelerator magnet cooled by superfluid helium.

In the field of applied superconductivity, there is a growing need to better understand heat transfers in superconducting accelerator magnets. Depending on the engineering point of view looked at, either 0-D, 1-D, 2D or 3D modeling may be needed. Because of the size of these magnets, alone or coupled together, it is yet, impossible to study this numerically for computational reasons alone without simplification in the description of the geometry and the physics. The main idea of this study is to consider the interior of a superconducting accelerator magnet as a porous medium and to apply methods used in the field of por-ous media physics to obtain the equations that model heat transfers of a superconducting accelerator magnet in different configurations (steady-state, beam losses, quench, etc.) with minimal compromises to the physics and geometry. Since the interior of a superconducting magnet is made of coils, collars and yoke filled with liquid helium, creating channels that interconnect the helium inside the magnet, an upscaling method provides models that describe heat transfer at the magnet scale and are suitable for numerical studies. This paper presents concisely the method and an example of application for super-conducting accelerator magnet cooled by superfluid helium in the steady-state regime in considering the thermal point of view

Superfluid Helium Flow in Porous Media

Superfluid helium is primarily used in the field of applied superconductivity. Given the complexity of the magnet geometry and the scales involved, a real 3D simulation of heat transfer in such devices at the micro-channel scale is very difficult, even impossible. However, the repeatability or even periodicity of the structure suggests the possibility of a macro-scale description following a porous medium approach. Which macro-scale model may be used? This largely remains an open field while some answers have been proposed based on experimental or theoretical work

Redéfinir le problème climatique par l'écoute du local : éléments de propédeutique

International audienceThe disappointing outcomes of international negotiations on climate change are frequently associated with inaction and the consequences of a perceived disconnection between science and politics. However, our experiences and empirical findings based on research carried out in France in highly diverse situations and among very different operators invalidate this thesis. By analysing climate change from the standpoint of territories and local adaptation and mitigation strategies, our article contends that the problem stems instead from a still insufficient fit between local and global levels of expertise and action frameworks. Moreover, we also need to analyse climate change from a new angle and recognise its dual nature in material and objective terms as well as in its cultural, symbolic and subjective components.Assimilés à de l'inaction, les résultats décevants du processus international de négociation sur les changements climatiques sont régulièrement interprétés comme la conséquence d'un découplage caractérisé entre science et politique. Les observations concrètes et les analyses que nous avons effectuées en France, dans des situations diverses et auprès d'opérateurs extrêmement variés, invalident cette thèse. Envisageant le changement climatique depuis les territoires et les stratégies locales d'atténuation et d'adaptation, l'article suggère que le problème procède plutôt d'une articulation encore insuffisante entre niveau global et niveau local-territorial d'expertise et de cadrage de l'action. Aussi convient-il de considérer à nouveaux frais le problème climatique, d'en reconnaître et d'en approfondir la double nature ou le double visage, en l'appréhendant dans ses données matérielles et objectives comme dans ses composantes culturelles, symboliques et subjectives. Abstract – Reframing climate issue by listening to local actors: elements of propaedeutic. The disappointing outcomes of international negotiations on climate change are frequently associated with inaction and the consequences of a perceived disconnection between science and politics. However, our experiences and empirical findings based on research carried out in France in highly diverse situations and among very different operators invalidate this thesis. By analysing climate change from the standpoint of territories and local adaptation and mitigation strategies, our article contends that the problem stems instead from a still insufficient fit between local and global levels of expertise and action frameworks. Moreover, we also need to analyse climate change from a new angle and recognise its dual nature in material and objective terms as well as in its cultural, symbolic and subjective components