Improvement of thermal homogenization using multiple swirling jets

The aim of this study is to examine different blowing configurations of multiple swirling jets for use it in terminal units of ventilation applications. The influence of several parameters such as the inclined vanes of diffuser and the sense of rotation of the single or multiple swirling jets, their number and their arrangement on the flow resulting dynamically and thermally is experimentally investigated. Flow rate was adjusted at Reynolds numbers, Re0, ranging from 104 to 30.103. The current study is carried out under uniform heat flux condition for each diffuser at Reynolds number of 30.103, the air being the working fluid. Experiences concerning the fusion of several jets show that the resulting jet is clearly more homogenized under swirling influence. The findings of this study show that the gap between the jets and their sense of rotation relative to the central jet, affects the quality of the homogenization of ambiance. Among the studied different configuration, the one which consists of a swirling central jet controlling the behavior of six swirling jets in counter-rotation is shown to be the most effective in terms of thermal destratification

Caractérisation thermique et dynamique d'un multi jet tourbillonnaire à orifices déséquilibrés en positions

Le but de cette étude est d'examiner l'influence du déséquilibre en position du jet central par rapport aux jets adjacents, dans une configuration de 6 jets hélicoïdaux entourant un jet hélicoïdal central. Afin d'identifier la configuration la plus efficace en termes d'amélioration du mélange en sortie de jet Le jet central joue le rôle de guide dans cette configuration de déséquilibre en position. Il pilote les jets adjacents. Cette configuration pourrait intéresser les industriels vue sa contribution pour l'amélioration du confort thermiqu

Simulation numérique à trois dimensions d'une flamme de diffusion en utilisant un schéma réactionnel quasi-global et détaillé

Dans le présent travail, on s'intéresse à la simulation numérique en trois dimensions (3D) des flammes de diffusion d'un écoulement turbulent et réactif dans une chambre de combustion d'une turbine à gaz. Un des objectifs est d'étudier l'influence des modèles de combustion et les mécanismes réactionnels sur la prédiction de l'écoulement du champ de température et la modélisation des émissions polluantes NOx. Les résultats numériques obtenus sont comparés aux résultats antérieur

Thermal characterization of a plate heated by a multi-jet system

This study is an experimental and numerical analysis of the influence from changes in the conditions of inputs temperature and velocity on the behavior thermal and dynamic of a multi-jet swirling system impacting a flat plate. The experimental device comprising three diffusers arranged in line, of diameter D aloof 2D between the axes of their centers, impinging the plate perpendicularly at an impact height H = 6D. The swirl is obtained by a generator (swirl) of composed 12 fins arranged at 60° relative to the vertical placed just at the exit of the diffuser. By imposing the temperature and velocity for three input conditions with three studied configurations. The paper deals with find the configuration that optimizes the best thermal homogenization. The results show that the configuration having an equilibrated inlet temperature (T, T, T) is derived from a good temperature distribution on the baffle wall and a better thermal transfer from the plate. The system was numerically simulated by the fluent code by using the turbulence model (k–ε). This last has yielded results accorded to those experimental results

Aerodynamic control of a diffusion flame to optimize materials' transition in a rotary cement kiln

International audienceThe aim of this work is to deepen the understanding of the aerodynamics of a diffusion flame in a rotary cement kiln. The kiln is a rotary with a cylindrical shaped, long and equipped with a burner, and it is the seat of a diffusion flame with an axisymmetric turbulent jet. The kiln has a capacity of 8,000 Nm 3 to 13,000 Nm 3 of natural gas and primary air at T = 25 °C which interacts with a secondary hot air volume at T = 800 °C. The aerodynamic modelling of the furnace is achieved using the turbulence model RNG k – ε , which is able to handle the turbulence and capture the vortex shedding process. The Ansys/Fluent code, based on the finite volume approach to solve the Reynolds averaged Navier-Stokes (RANS), was used in this study. The interactions between turbulence and diffusion flame were handled by the PDF (Probability Density Function) approach. The numerical simulations have been validated by experiments from the kiln considered. Based on the findings obtained, it is concluded that the recirculation zone seems of paramount importance when combustion is taken into account because the reverse flow improves the flame stability and affects the combustion efficiency. In addition, limiting the secondary air flow through the furnace is major to improve combustion and avoid disturbing the advancement of the material along the kiln

Numerical study of a three swirling jets system impacting a plane plate

This investigation deals with a numerical simulation of a multiple swirling jets system impacting a plane plate. The studied configuration composed of three diffusers arranged in line, with diameter D and the gap between the axes of their centers are fixed to 2D. The height of impact is fixed to 4D, impacting the plate perpendicularly. The swirling jet is generated by swirler system composed of 12 vanes inclined by the angle of 60° relative to the vertical position just outside of the diffuser. The velocity and the temperature of the air flow are fixed in the inlet of diffusers. The objective of this work is to identify the factors that may influence the efficiency of the ventilation performance, such as the jet configuration and the impact height. The studied configuration was numerically simulated by the finite volume method. The equations systems have been closed with the turbulence model (k-ε). In general, the prediction of the flow field is in better agreement with the experimental data. The results obtained show that the studied parameters have significant effects on the flow characteristics and behavior of multi-jet impinging. The configuration of three jets with a 4D impinging height has given a good development of the jet and an almost uniform temperature along the plate with the input temperature conditions in the diffusers (T, T, T)

Caractérisation thermique d’un multijet tourbillonnaire en mode confiné avec et sans obstacle

La compréhension des effets du confinement d’un multi jet tourbillonnaire, sur le taux d’entraînement de l’air et sur la stratification de la température est très importante pour l’efficacité du processus de conditionnement d’air. Les jets impactant sont un moyen efficace d’optimisation des transferts thermiques entre un fluide et une structure solide. Ils sont, à ce titre, utilisés dans diverses applications industrielles telles que les processus de rafraichissement, de réchauffement ou de séchage. Une série d’études expérimentales a été menée pour déterminer l’influence de différents facteurs sur les caractéristiques et la structure du jet tourbillonnaire multiple permettant d’obtenir le mélange permettant l’homogénéisation de l’ambiance dans les locaux et de même dans les chambres de combustion

Numerical investigation of thermal characteristics of confined rotating multi-jet

For using the swirling jet for air conditioning and heating in the premises, knowledge of the thermal characteristics is more than necessary. It is for this objective that the experimental and numerical study was realized. To conduct this study, we designed and built an experimental facility to ensure proper conditions of confinement in which we placed five air blowing devices with adjustable vanes, providing multiple swirling turbulent jet with a swirl number S = 0.4. The jets were issued in the same direction and the same spacing defined between them. This study concerned the numerical simulation of the thermal mixing of confined swirling multi-jets, and examined the influence of important parameters of a swirl diffuser system on the performance characteristics. The experimental measurements are also realized for a confined domain, aiming to determine the axial and radial temperature field. The CFD investigations are carried out by an unstructured mesh to discretize the computational domain. In this work, the simulations have been performed using the finite volume method and FLUENT solver, in which the standard k-ε, K-ε realizable, k-ε RNG and the RSM turbulence model were used for turbulence computations. The validation shows that the K-ε RNG model can be used to simulate this case successfully

Comparative Investigation on Heated Swirling Jets Using Experimental and Numerical Computations

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