No abstract

Accurate knowledge of hydrodynamic parameters is of major importance for the performance study of liquid-liquid column extractors. The effects of operating parameters on dispersed phase holdup profiles. drop size distributions, and axial mixing in both phases were investigated in a 127 mm diameter multistage contactor of pilot plant scale for the toluene-water physically equilibrated system. Correlations for the mean holdup, the mean drop size, and the continuous phase backmixing were obtained. A stronger dependence of holdup and drop size on the operating conditions and especially on the agitation speed was observed as compared to previous investigations for the same type of contactor. The axial mixing for the single phase flow was found to follow adequately an existing correlation, while the continuousphase axial mixing in two-phase flows showed some deviations from other existing correlations. Also, flooding criteria. important for the control of the extraction process, were determined based on the shape of the holdup profiles. ~~. ~. ~~ II est trbs important de connaitre exactement les parametres hydrodynamiques pour I'etude de performance des extracteurs B colonne liquide-liquide. Les effets des parametres d'operation sur les profils de rktention de la phase dispersee, les distributions de taille des particules et le melange axial dans les deux phases, ont Cte etudies dans un contacteur pilote multietage de 127 mm de diametre pour le systkme equilibre physiquement toluene-eau. On a obtenu des correlations pour la retention moyenne, la taille moyenne des gouttes et le retromelange en phase continue. On a observe une forte dependance de la retention et de la taille des gouttes par rapport aux conditions d'operation et en particulier par rapport la vitesse d'agitation comparativement i des recherches anterieures pour le mCme type de contacteur. On a trouve que le melange axial pour I'Ccoulement de la phase simple suivait bien une correlation existante, tandis que le melange axial en phase continue dans les Ccoulements diphasiques montrent quelques @carts avec les autres correlations existantes. En outre, on a determine des critt-res d'engorgement, importants pour le contrble du processus d'extraction, en se basant sur la forme des profils de retention.

No abstract

No abstract

No abstract

The work considers the modeling of turbulent flow in radial diffuser with axial feeding. Due to its claimed capability to predict flow including features such as separation, curvature and adverse pressure gradient, the RNG k-epsilon model of Orzag et al. (1993) is applied in the present analysis. The governing equations are numerically solved using the finite volume methodology. Experiments were conducted to assess the turbulence model. Numerical results of pressure distribution on the front disk surface for different flow conditions when compared to the experimental data indicated that the RNG k-epsilon model is adequate to predict this class of flow

No abstract

Experiments and computations were performed to determine the local heat transfer in radial flows between parallel concentric disks. The flow is supplied axially by a feeding orifice placed in one of the disks and becomes radial after being deflected by the frontal disk. The frontal disk is kept isothermal and the other solid surfaces washed by the flow are kept adiabatic. Local heat transfer coefficients were determined using the naphthalene sublimation technique and the analogy between heat and mass transfer. Computations were performed using a finite volume methodology. The local Nusselt number distribution showed a valley at the stagnant region in front of the feeding orifice and a peak at the diffuser entrance where the flow impinges on the frontal disk prior to becoming radial. Depending on the Reynolds number and on the gap between the disks a secondary peak was observed in the diffuser region. The secondary peak is believed to be caused by nonparallelism or unsteadiness of the flow field and was not captured by the numerical model.