, 160 6.2.3 Evaporation du film liquide en micro-canal

, Développement d'un modèle d'évaporation de film liquide 173

. .. Description,

. .. , Premiers résultats : que peut-on attendre de ce modèle ?, p.183

;. .. Retour-sur-le-modèle, 186 7.3.1 Vitesse de déplacement du front liquide/vapeur, discussion autour des hypothèses

.. .. Schéma-de-principe-du-modèle,

.. .. ,

, Profils de températures le long de la paroià différents instants t, p.183

, Evolution de l'épaisseur du film et du coefficient d'échange correspondant le long de la paroià l'instant t = 1,5

, Bilan de masse sur un volume de contrôle comprenant l'interface liquide vapeur

, Erreur relative dans l'approximation de la vitesse du front liquide/vapeur, p.188

, pour (a) v liq = 0,1 m.s -1 (b) v liq = 1 m.s -1, Comparaison des profils temporels de températures en utilisant v liq ou v int

, Représentation 3D des courbures orthogonales axiale K x et radiale K r de l'interface

, Ecoulement de liquide dans le film et conditions aux limites, p.192

, Pertes de charges ?P l en fonction de la vitesse d'écoulement U ? 0 pour différentes longueurs de film liquide

, Schématisation de l'écoulement vapeur avec pertes de charge ?P v, p.194

, Structure de l'interface liquide/vapeur (a) sans courbure du ménisque, (b) avec courbure du ménisque

, Evolution temporelle de l'épaisseur de film et du coefficient d'échange en un point donné (x/L e = 0,5) (a) pour un temps de calcul de 3 s, (b) zoom sur la zone de ménisque

, Profils de températures longitudinalesà la paroi avec et sans ménisque,à t = 1,5

, On préciseégalement que la géométrie de ce ménisque est fixée et reste constante dans le temps

, 15 compare l'évolution temporelle de l'épaisseur de film et du coefficient d'échange en un point donné du système (x/L e = 0,5), sur un temps de calcul de 3 s

, ) (a) pour un temps de calcul de 3 s, (b) zoom sur la zone de ménisque Le passage du bouchon liquideà la zone de film liquide s'accompagne d'une brusque augmentation du coefficient d'échange, de sa valeur h l pour le bouchon liquideà h f ilm . Ce coefficient augmente alors graduellementà mesure que l'épaisseur de film diminue, jusqu'à un pic, déjà visible précédemment, symbolisant l'extrémité du film liquide et donc le passage dans la zone asséchée. Le passage progressif de la zone liquide au film, caractérisé par la zone de ménisque, est plus visible sur la figure 7.15 (b), de nouvelles dispositions ou géométries, pourraientégalementêtre testés. Pourtant, les carences actuelles en terme de connaissances théoriques limitent

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B. Annexe, Le solveur effectue alors plusieurs itérations, jusqu'à obtenir la valeur de la paire (G cond ; G pertes ) permettant de minimiser l'écart (P imposée ? P mesurée ) 2 . L'application de cette procédure aux données du tableau a permis de déduire les valeurs suivantes, Evaluation des pertes thermiques thermiques avec le milieu ambiant) sont estimés en minimisant l'écart quadratique entre le résultat de cette fonction et la puissance imposée