Mesure de coefficients de convection par méthode impulsionnelle—influence de la perturbation de la couche limite

We present here some elements in order to improve the non-destructive procedures for the measurement of the local heat transfer coefficient between a plate uniformly heated and an air-flow. We use the pulsed photothermal method which consists of analysing the transient temperature on the front face of a wall, initially subjected to a convective flow, after a sudden deposit of luminous energy. For the examination of the experimental thermograms, two models are used: in the first one the heat coefficient is assumed to remain constant during the pulsed experiment, and we take into account its variation in time in the second one. The temporal variation law of the heat transfer coefficient used in the second model is obtained by extension of the differential method to the unsteady laminar boundary-layer due to a finite duration excitation. We compare the results of the two models in transient state with those given in steady state by multi-layered heat flux sensor.     

工业炉de余热回收

本文综述工业炉的余热回收，并介绍热管技术及其在工业炉余热回收方面的应用。     

太阳角de计算

无论是哪一种形式的太阳能收集器,都必然要涉及到太阳高度角、方位角、日照时间等计算问题。太阳光线和地平面法线之间的夹角Q_z称为太阳天顶角;太阳光线和它在地平面上投影线之间的夹角α_s称为     

远红外干燥技术de应用

远红外加热技术目前已在轻化工、印染、食品等行业得到了广泛的应用,但在中药生产上目前应用范围还较小.我厂引进并应用远红外干燥技术从80年代开始,经过几年的应用实践表明,远红外加热设备具有耗能少、加热效率高、产品质量稳定,环境卫生好等优点.     

de Winter综合征临床资料分析

【摘要】 目的 分析总结de Winter 综合征临床诊疗特点。方法 入选2017年7月至2018年6月上海长海医院收治的急性心肌梗死（AMI）患者58例，根据急诊时心电图表现，分为de Winter综合征组（n=8）和前壁ST段抬高型心肌梗死（STEMI）组（n=50）。回顾性对比两组患者临床症状、实验室检查、治疗方式、门诊至球囊扩张时间、急性并发症等情况，分析总结de Winter 综合征患者临床特点。结果 两组间心电图预测罪犯血管、恶性心律失常发生率、门诊至球囊扩张时间比较，差异均有统计学意义（P＜0.05）。其余项目比较差异均无统计学意义。结论 de Winter 综合征心电图改变在预测罪犯血管上不及STEMI心电图改变敏感。de Winter 综合征患者易并发恶性心律失常。de Winter 综合征不易早期识别，应加强宣教，提高诊断能力。
     

Version étendue du filtre de Kalman discret appliquée à un problème inverse de conduction de chaleur non linéaire

An extended version of the discrete Kalman filter applied to a nonlinear inverse heat conduction problem. A nonlinear inverse heat conduction problem is resolved by using a formulation of the Kalman filter based on a statistical approach and extended to nonlinear systems. The time evolution of a surface heat flux density is reconstructed from a numerical simulation which allowed us to analyse the influence of some parameters, that condition the running of the filter, on the estimation result. A suitable choice of these parameters, guided by the filter behaviour observations, leads to a solution that remains stable when using noisy data, but that is slightly time-lagged compared to the exact function. This time-lag depends on the location of the interior temperature measurement needed for the inversion and on the model error caused by the approximation of the heat flux with a piece-wise constant function. The application of the extended Kalman filter with real measurements recorded from an experimental set-up, shows that this technique fits the stochastic structure of experimental measurements. The provided results are validated by using the Raynaud's and Bransier's inverse method and are in good agreement with the heat flux density estimated with this method.     

Modèles de transferts thermiques lors de la fusion d'une solution binaire dispersée

Heat transfer models during the melting of a dispersed binary solution. In this paper, we present a model for heat transfers occurring during the melting of crystallized droplets of a binary solution dispersed within an oil. This model takes into account the heat conduction within the emulsion associated with a heat source (sink) due to the eutectic melting of droplets followed by the progressive melting. The model has been applied to the differential scanning calorimetry in the case of aqueous solutions of ammonium chloride dispersed in a motor oil. The investigated cell containing the emulsion is a cylinder a few mm ³ in volume. By simulation, we could replicate the shape of the experimental thermogramms. The validation of the model permits determining some parameters which are experimentally inaccessible due to the small size of the cell, like the space–time evolution of the temperature inside the DSC sample or the concentration of every droplet as well as the melted proportion.     

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.     

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.     

Conductivité thermique de matériaux poreux humides: évaluation théorique et possibilité de mesure

We develop here a mathematical model of simultaneous heat and mass transfer in unsaturated porous media. We put forward the influence of the total pressure gradient in the gaseous phase on the mass transfer contrary to the classical models where only two driving forces are taken into account: a temperature and a moisture gradient. We use this model on the one hand to investigate the theoretical notion of the apparent thermal conductivity of a wet porous medium and on the other hand to simulate a hot plate measurement and an unsteady state one (“flash” method). We show the great importance of both the total pressure gradient and the boundary conditions, that is to say of the measurement technique on the results.     

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.     

La réanalyse du transfert instationnaire de la chaleur

This paper presents a new method to solve the thermal diffusion with, in a first step, the formulation of the general solution of the linear equations, and in a second step the particular solution of the study by introducing the boundary conditions which specialize the system of equations. This method enables to reanalyse easily the problem for various modified boundary conditions and applied thermal loads.     

Modélisation d'un panache d'émetteur de chaleur pour le logiciel de simulation énergétique des bâtiments SPARK

Plume's convector modeling for object-oriented thermal building simulation software SPARK. In this paper, a zonal model used to predict air movement and temperature distribution in a room is presented. This model is based on a rough partitioning of the room: it is an intermediate approach between one-node models (that consider a homogeneous temperature in each room) and CFD models. Flow rates are calculated in respect to the pressure distribution in low velocity domains and specific laws describe plumes and jets. The airflow model is coupled with a building envelope model. They are implemented in an object-oriented environment called SPARK. The modularity of SPARK allows the creation of very flexible tools, and its strict syntax permits having the simulations automatically generated.     

The behaviour of the coup de fouet of valve-regulated lead–acid batteries

This paper presents the results of an investigation into the initial stage of the discharge voltage response of valve-regulated lead–acid (VRLA) batteries. This region is dominated by the phenomenon known as the coup de fouet which manifests itself as a voltage dip followed by a recovery. The research focuses on two parameters found within the coup de fouet region, namely, the trough and the plateau voltage. It is found that these parameters are influenced by the operating conditions and the sate-state-of health (SoH) of the battery. The operating conditions considered are discharge rate, ambient temperature, depth of previous discharge, charge duration, and float voltage. The coup de fouet parameters corresponding to high rate discharges, as well as discharges conducted at low temperatures, have reduced magnitudes compared with those conducted at lower rates or higher temperatures. This behaviour mirrors the availability of capacity when the battery is discharged under the same operating conditions. The float voltage is found to have a direct relationship with the trough and plateau voltages, whereas an indirect relationship between charge duration and the trough and plateau voltages is observed. The influence of variations in discharge depth on the coup de fouet is more complex. For consecutive discharge depths below approximately 10% of rated capacity, the coup de fouet becomes distorted and exhibits a second voltage dip. For consecutive discharges of greater depth, this does not occur. The influence of the degradation in battery SoH due to accelerated thermal ageing, water replenishment post-accelerated thermal ageing, and field ageing is investigated. The coup de fouet parameters associated with the discharge of batteries with low SoH have a reduced magnitude compared with those associated with the discharge of batteries with a high SoH.     

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.     

Séchage superficiel d'un matériau poreux humide par convection forcée d'air chaud: couplage entre les équations de transfert dans le matériau et celles de la couche limite

The authors considered drying of a thick slab of humid porous material immersed in a laminar steady flow of hot air parallel to its surface. They wrote the boundary layer equations in air (continuity, momentum, energy and mass), those describing humidity and heat transfer in the porous medium deduced from Luikov's theory. Then, they coupled them at the air-product interface by expressing the continuity of the thermal and mass fluxes taking into account the evaporation. They solved numerically the resulting system of differential equations using an implicit finite-difference method. They determined the instantaneous evaluation of the spatial distributions of heat and humidity, the local values of the Nusselt and Sherwood numbers. They also studied the influences of principal parameters of the system.     

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.