Évaporation en convection forcée d'un film liquide mince ostwaldien ruisselant en régime laminaire permanent sur une surface plane isotherme et inclinée

The authors study, in forced convection, the evaporation of an Ostwaldian film flowing over an isothermal inclined plane surface to determine the influence of the behaviour index of the liquid on the dynamic and thermal characteristics of liquid-air system. The liquid flow is considered partially two-dimensional whereas for the air it is two-dimensional. The coupled equations with the interfacial conditions are solved using a fully implicit finite differences method. From the study, it appears that the behaviour index influences considerably the transfers which are more important for pseudoplastic liquids than for dilatant ones.     

Ecoulements induits par la force gravifique dans une cavité cylindrique en rotation

A spectral Tau-Chebyshev method is used for the prediction of the motion of a rotating Boussinesq fluid driven by buoyancy from a horizontal temperature gradient. The analysis is made for the axisymmetric regime in annular cavities when the physical parameters vary as: 0≤ Re≤ 2500; Ra = 10², ± 10⁴, 10⁵; 0 ≤ Fr ≤ 25. The transition from the thermal convection regime to the rotation dominated regime results from the competition between the various buoyancy, centrifugal and Coriolis forces. The validity of the asymptotical solutions derived from Hunter (1966) when Fr ⪡ 1 andRe ⪢ 1, is discussed when Re varies.     

Modélisation en régime transitoire des mouvements convectifs dans une cellule d'habitation

This study aims thermal phenomena modelling inside a dwelling cell in order to determine temperature distribution there. A coupling of the zonal method and integral analysis in walls vicinity is carried out. The zonal method lies on breaking up the cell into isothermal zones. Mass and energy balances are established, in transient flow, for each zone. The various convective transfer types are listed and studied: transfer between air and walls, transfer between air layers, transfer between air and cold air jet, transfer between air and transmitter. Conductive transfer through walls and radiative transfer inside the cell are also taken into account. An experimental validation campaign is also achieved in a testing room, two heat transmitter types are tested: distributed and located. Validation results are satisfying and air diffusion importance is emphasised. The influence of air nodes number is also studied.     

胆总管空肠Roux en Y机械吻合术后吻合口出血的血管内栓塞治疗

【摘要】 目的 探讨血管内栓塞治疗胆总管空肠Roux en Y机械吻合术后吻合口出血的疗效和安全性。方法 16例经DSA检查证实胆总管空肠Roux en Y机械吻合术后吻合口出血患者,超选至病变责任供血动脉,采用血管内明胶海绵和（或）弹簧圈栓塞治疗,观察疗效,总结治疗经验。结果 术中造影发现16例患者出血部位均位于机械吻合口处,并可见对比剂明显外溢,对其责任供血动脉进行超选并栓塞,术后患者腹腔留置引流管出血停止,实验室检查提示血红蛋白及红细胞计数未再下降。术中、术后均未出现与血管内治疗相关的并发症。结论 血管内栓塞治疗是胆总管空肠Roux en Y机械吻合术后吻合口出血安全、有效的治疗手段。
     

Représentation non locale d'un milieu hétérogène en diffusion pure

For a one-dimensional diffusive transfer through a spatially periodic heterogeneous medium, the quadrupoles method allows to obtain the exact non-local (in time) equation describing the transfer. The case of reversible (that is to say when input and output can be permuted) and non-reversible media is examined separately. Some examples are treated for illustration: degenerated media (made of pure resistances or capacitances) or real media. The obtained equation cannot be reduced to the hyperbolic Cattaneo–Vernotte equation, which is unable to describe diffusive transfer through heterogeneous media.     

Étude numérique de l'ébullition en convection mixte dans une couche poreuse verticale

By using an enthalpic method (two-phase mixture model), we have studied numerically boiling with mixed convection in a vertical porous layer with a discrete heating. Liquid is injected at the top face. Finite volume method is used for numerical resolution of equations of volumetric enthalpy and pressure. Results giving time–space evolution of temperature, pressure, velocities of the fluids and evaporated volume are presented and analyzed. Parametric studies to assess the effects of inlet velocity, imposed heat flux and permeability, were performed. Results show that boiling is important if the effects of both, natural and forced convections are similar. The evaporated volume will decrease at high values of intrinsic permeability of porous medium or at high values of inlet velocity.     

Contact périodique en regime etabliresistances thermiques apparentes limites pour des durees de contact nulles et unfinies

The knowledge of heat transfer between periodically contacting metallic surfaces is necessary in numerous engineering applications.The analytical solution for quasi-steady state heat transfer in periodically contacting finite regions was first given by NIKHAILOV[1], and then by VICK and OZISIK [2]. These solutions are revisited. The limit cases at infinite or nul contact duration are studied. It is shown that the apparent limit resistances of the system are: These expressions are convenient physical tools easier to implement than the exact analytical solution.     

Transferts couples de chaleur et de masse dans des matériaux consolides utilises en génie civil

The method of measuring the humidity in the materials based on the determination of the thermal conductivity is presented and the principal characteristics are analysed. The water diffusion coefficients due to the water content and temperature gradients are measured and utilized in the numerical calculation of a drying process. These results are compared to an experiment and discussed. We note the difficulty of describing the superficial mass transfer with a single coefficient function of the heat transfer coefficient. We present some enthalpic balance which proves of interest in taking into account the presence of humidity in walls of buildings.     

Utilisation de modèles d'identification non entiers pour la résolution de problèmes inverses en conduction

Heat flux estimation through inverted non-integer identification models. A model of non-integer order that reproduced the transient thermal behaviour of a system is identified. This model is expressed as a linear relationship between the fractionnal derivates of the temperature at a point of the medium and those of the solicitation applied on the system. Using recursive form of the derivates lead to identify the unknows of the model applying the linear least square method from experimental data. The application concerned a semi-infinite medium submited to a single heat flux on its surface. Among the applications of this approach, the identified model is used in an inverse technique to estimate the heat flux applied on the medium.     

Un modèle simple de la pénétration couplée de chaleur et de matière dans l'absorption gaz-liquide en film ruisselant laminaire

In this paper we present a simple model based on the coupled penetration of heat and mass fronts for the study of the absorption kinetics of vapor in a concentrated salt solution falling in laminar flow down an adiabatic wall. Though this model is very simple, it permits a concrete and intuitive comprehension of the numerical integration of differential equations. The forecasts of this model, in the case of the absorption of water vapor in the lithium bromide solution, are presented and compared to the results of the numerical solution.     

Étude expérimentale d'une interaction de jets obliques avec un écoulement transversal compressible. I. Effets de la compressibilité en régime subsonique sur les champs aérothermiques

Experimental study of inclined jets cross flow interaction in compressible regime. I. Effect of compressibility in subsonic regime on velocity and temperature fields. The results of the investigation of the interaction of a row of jets with a compressible cross flow are compared with their counterpart obtained in incompressible regime. The comparison reported here focuses on the flow field resulting from the interaction above and at the wall. The velocity and temperature fields are measured respectively by laser Doppler velocimetry and thermocouple probes. The wall temperature distributions are measured using an infrared camera. The experiments are performed for cross flow Mach numbers of 0.72 and 0.1 for respectively the compressible and incompressible regimes with almost the same injection rate (R=0.50 and 0.6). Significant differences are noticed between the two flow fields in particular on the vertical development of the jets in the cross flow and on the turbulent diffusion. The jet penetration is found to be higher in the compressible regime with less interaction between the jets. The comparison also shows that the wall heat transfer modifications induced by the jets are less pronounced in the compressible case as a result of the higher penetration of the jets. These results show that neither the mass flux ratio nor the momentum ratio are good candidates for extrapolation of the cooling efficiency from the incompressible case to the real compressible case as encountered in the practical applications.