Computational Fluid Dynamics Modeling of Impinging Gas-Jet Systems: II. Application to an Industrial Cooling System Device

2005 ◽  
Vol 127 (4) ◽  
pp. 704-713 ◽  
Author(s):  
M. Coussirat ◽  
J. van Beeck ◽  
M. Mestres ◽  
E. Egusquiza ◽  
J.-M. Buchlin ◽  
...  
Keyword(s):  
Nusselt Number ◽  
Eddy Viscosity ◽  
Cooling System ◽  
Flow Behavior ◽  
Impinging Jets ◽  
Dynamics Modeling ◽  
Cooling Systems ◽  
Computational Fluid Dynamics Modeling ◽  
Numerical Predictions ◽  
Viscosity Models

A numerical analysis of the flow behavior in industrial cooling systems based on arrays of impinging jets has been performed, using several eddy viscosity models to determine their modeling capabilities. For the cooling system studied, and in terms of mean Nusselt number values, the best agreement between experimental results and numerical predictions was obtained with the realizable k-ε model. On the other hand, numerical predictions of the local Nusselt number and its spatial variations along the wall are better adjusted to the experiments when using either the standard k-ε or the standard k-ω models. The results obtained also show that the predicted thermal field depends strongly on the combination of near-wall treatment and selected turbulence model.

Computational Fluid Dynamics Modeling of Impinging Gas-Jet Systems: I. Assessment of Eddy Viscosity Models

2005 ◽  
Vol 127 (4) ◽  
pp. 691-703 ◽  
Author(s):  
M. Coussirat ◽  
J. van Beeck ◽  
M. Mestres ◽  
E. Egusguiza ◽  
J.-M. Buchlin ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Nusselt Number ◽  
Eddy Viscosity ◽  
Gas Jet ◽  
Dynamics Modeling ◽  
Computational Fluid Dynamics Modeling ◽  
Mean Values ◽  
Viscosity Models ◽  
Good Agreement

Computational fluid dynamics plays an important role in engineering design. To gain insight into solving problems involving complex industrial flows, such as impinging gas-jet systems (IJS), an evaluation of several eddy viscosity models, applied to these IJS has been made. Good agreement with experimental mean values for the field velocities and Nusselt number was obtained, but velocity fluctuations and local values of Nusselt number along the wall disagree with the experiments in some cases. Experiments show a clear relation between the nozzle-to-plate distance and the Nusselt number at the stagnation point. Those trends were only reproduced by some of the numerical experiments. The conclusions of this study are useful in the field of heat transfer predictions in industrial IJS devices, and therefore for its design.

On Application of Nonlinear k-ε Models for Internal Combustion Engine Flows

2002 ◽  
Vol 124 (3) ◽  
pp. 668-677 ◽  
Author(s):  
G. M. Bianchi ◽  
G. Cantore ◽  
P. Parmeggiani ◽  
V. Michelassi
Keyword(s):  
Internal Combustion Engine ◽  
Eddy Viscosity ◽  
Combustion Engine ◽  
Turbulence Models ◽  
Internal Combustion ◽  
Moment Closure ◽  
Reynolds Stresses ◽  
Mean Velocity ◽  
Numerical Predictions ◽  
Viscosity Models

The linear k-ε model, in its different formulations, still remains the most widely used turbulence model for the solutions of internal combustion engine (ICE) flows thanks to the use of only two scale-determining transport variables and the simple constitutive relation. This paper discusses the application of nonlinear k-ε turbulence models for internal combustion engine flows. Motivations to nonlinear eddy viscosity models use arise from the consideration that such models combine the simplicity of linear eddy-viscosity models with the predictive properties of second moment closure. In this research the nonlinear k-ε models developed by Speziale in quadratic expansion, and Craft et al. in cubic expansion, have been applied to a practical tumble flow. Comparisons between calculated and measured mean velocity components and turbulence intensity were performed for simple flow structure case. The effects of quadratic and cubic formulations on numerical predictions were investigated too, with particular emphasis on anisotropy and influence of streamline curvature on Reynolds stresses.

Thermal and Fluid-Dynamic Behaviour of Confined Slot Impinging Jets With Nanofluids

2011 ◽  
Author(s):  
O. Manca ◽  
P. Mesolella ◽  
S. Nardini ◽  
D. Ricci
Keyword(s):  
Reynolds Number ◽  
Nusselt Number ◽  
Particle Concentration ◽  
Dynamic Behaviour ◽  
Fluid Dynamic ◽  
Reynolds Numbers ◽  
Impinging Jets ◽  
Cooling Systems ◽  
Al2o3 Nanofluid ◽  
Model Approach

Heat transfer enhancement technology has the aim to develop more efficient systems as demanded in many applications in the fields of automotive, aerospace, electronic and process industry. A possible solution to obtain efficient cooling systems is represented by the use of confined or unconfined impinging jets. Moreover, the introduction of nanoparticles in the working fluids can be considered in order to improve the thermal performances of the base fluids. In this paper a numerical investigation on confined impinging slot jets working with water or water/Al2O3 nanofluid is described. The flow is turbulent and a constant temperature is applied on the impinging surface. A single-phase model approach has been adopted. Different geometric ratios and nanoparticle volume concentrations have been considered at Reynolds numbers ranging from 5000 to 20000. The aim consists into study the thermal and fluid-dynamic behaviour of the system. The stream function contours showed that the intensity and size of the vortex structures depend on the confining effects, Reynolds number and particle concentrations. The local Nusselt number profiles show the highest values at the stagnation point and the average Nusselt number increases for increasing particle concentrations and Reynolds numbers and the highest values are observed for H/W = 10 The required pumping power increases as particle concentration as well as Reynolds number grow and it is at most 4 times greater than the values calculated in the case of base fluid.

Heat Transfer Prediction of a Jet Impinging a Cylindrical Deadlock Area

2014 ◽  
Vol 136 (11) ◽  
Author(s):  
Yacine Halouane ◽  
Amina Mataoui ◽  
Farida Iachachene
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Flow Behavior ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Potential Core ◽  
Numerical Predictions

The turbulent heat transfer by a confined jet flowing inside a hot cylindrical cavity is investigated numerically in this paper. This configuration is found in several engineering applications such as air conditioning and the ventilation of mines, deadlock, or corridors. The parameters investigated in this work are the Reynolds number (Re, 20,000 ≤ Re ≤ 50,000) and the normalized distance Lf between jet exit and the cavity bottom (Lf, 2 ≤ Lf  ≤ 12). The numerical predictions are performed by finite volume method using the second order one-point closure turbulence model (RSM). The Nusselt number increases and attains maximum values at stagnation points, after it decreases. For an experimental test case available in the literature Lf = 8, the numerical predictions are in good agreement. Processes of heat transfer are analyzed from the flow behavior and the underlying mechanisms. The maximum local heat transfer between the cavity walls and the flow occurs at Lf = 6 corresponding to the length of the potential core. Nusselt number at the stagnation point is correlated versus Reynolds number Re and impinging distance Lf; [Nu0=f(Re,Lf)].

Numerical Analysis of a Multiple Jet Impingement System

2009 ◽  
Author(s):  
G. Arvind Rao ◽  
Myra Kitron-Belinkov ◽  
Yeshayahou Levy
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Flow Behavior ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Jet Impingement ◽  
Impinging Jets ◽  
Turbulent Regime ◽  
Transfer Coefficients ◽  
Complex Flow

Jet impingement is known to provide higher heat transfer coefficients as compared to other conventional modes of single phase heat transfer. Jet impingement has been a subject of research for a long time. Single jets have been studied extensively for their heat transfer and flow characteristics. However, for practical usage, multiple jets (in the form of arrays) have to be used for increasing the total heat transfer over a given area. Most of the research on multiple impinging jets have focused on evaluating heat transfer correlations for such arrays in the turbulent regime (Re >2500). The focus of the present paper is on experimental investigation of a large array of impinging jets in the low Reynolds number regime (<1000) and subsequently numerically modeling the same array by using existing Computational Fluid Dynamics tools in order to study the physical phenomena within such a complex system. Different turbulence models were used for modeling the fluid flow within these impinging jets and it was found that the SST k-ω model is the most suitable. Results obtained from CFD analysis are in reasonable agreement with experimental values. It was observed that CFD simulations over predicted the Nusselt number and pressure drop when compared to the experimentally obtained values. It was also observed that the decrease in Nusselt number along the streamwise direction of the array was not monotonic. This could be due to the complex flow field resulting from interaction between the crossflow and the impinging jets in the wall jet region. It is anticipated that results obtained from the present work will provide greater insight into the flow behavior and the heat transfer mechanism occurring in multiple impinging jets.

Effect of Jet Shape of Square Array of Multi-Impinging Jets on Heat Transfer

2013 ◽  
Author(s):  
Yoshisaburo Yamane ◽  
Makoto Yamamoto ◽  
Masahiro Motosuke ◽  
Shinji Honami
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Flow Direction ◽  
Flow Behavior ◽  
Impinging Jets ◽  
Intermittent Flow ◽  
Inlet Temperature ◽  
Thermochromic Liquid Crystal ◽  
Local Flow ◽  
Flow Intermittency

It is necessary to increase turbine inlet temperature to improve the performance of the aircraft gas turbine engine. Therefore, effective cooling techniques are still required. The purpose of the present study is to clarify the heat transfer characteristics for the high cooling performance of multiple impinging jets. A focus is placed on the effect of the jet ejection shape, since the shape of jet is expected to enhance flow mixing in accordance with a change in vortex structures at the shear layer of the jet. Experiment was made on the wall jet interaction between adjacent impinging jets by changing the jet ejection shape. Both heat transfer and aerodynamic characteristics in 3×3 square arrays of three types of jet hole shapes, which are circle, cross-shape and oblique cross-shape, are investigated at jet diameter Reynolds number of 4,680. Injection distance is ranged from 2D to 6D, and jet-to-jet spacing is 6D where D is a jet hole diameter. Steady state thermochromic liquid crystal technique is employed to measure local and area averaged Nusselt number. A micro flow sensor, which can detect both flow direction and flow intermittency near the wall, is used to clarify the characteristics of the unsteady flow behavior. It is found that higher local Nusselt number area is spread outward in the concave direction of the cross-shaped jet on the target surface. Characteristic flow behavior due to the flow intermittency and the local flow fluctuation induced by the effect of jet shape are observed in the region surrounded by the adjacent impinging jets in the cases of cross-shaped jet and oblique cross-shaped jet. This intermittent flow phenomenon is considered to contribute to the enhancement of the heat transfer in the intermediate region enclosed by surrounded impinging jets.

scholarly journals The thermal-flow behavior of the working chamber in an oil-free scroll compressor

2013 ◽  
Vol 34 (3) ◽  
pp. 161-172 ◽  
Author(s):  
Józef Rak
Keyword(s):  
Mesh Generation ◽  
Good Accuracy ◽  
Flow Behavior ◽  
Dynamics Modeling ◽  
Governing Equations ◽  
Compression Process ◽  
Scroll Compressor ◽  
Computational Fluid Dynamics Modeling ◽  
Thermodynamics Modeling ◽  
Volume Method

Abstract The paper presents the full transient, two-dimensional finite volume method numerical calculations of the classical involute scroll compressor geometry. The purpose of the study was to develop and evaluate an adaptable implementation of numerical fluid mechanics and thermodynamics modeling procedure with a mesh deformation. The methodology consisting in the compression chamber geometry preparation, mesh generation and governing equations solving was described. The evaluation was carried by simulating an adiabatic compression process and the results were compared with the theoretical zero-dimensional model and the existing research concerning the scroll chamber computational fluid dynamics modeling. It has been shown that the proposed modeling routine results in good accuracy for the scroll compressors study applications.

Assessment of thermal behavior of a cooling system to reduce thermal fatigue cracks in aluminum injection molds

2020 ◽  
pp. 75-86
Author(s):  
Sergio Antonio Camargo ◽  
Lauro Correa Romeiro ◽  
Carlos Alberto Mendes Moraes
Keyword(s):  
Thermal Fatigue ◽  
Cooling System ◽  
Fatigue Cracks ◽  
Cooling Water ◽  
Thermal Conditions ◽  
Thermal Gradients ◽  
Ansys Software ◽  
Cooling Systems ◽  
Thermal Fatigue Cracks ◽  
Number Of Cycles

The present article aimed to test changes in cooling water temperatures of males, present in aluminum injection molds, to reduce failures due to thermal fatigue. In order to carry out this work, cooling systems were studied, including their geometries, thermal gradients and the expected theoretical durability in relation to fatigue failure. The cooling system tests were developed with the aid of simulations in the ANSYS software and with fatigue calculations, using the method of Goodman. The study of the cooling system included its geometries, flow and temperature of this fluid. The results pointed to a significant increase in fatigue life of the mold component for the thermal conditions that were proposed, with a significant increase in the number of cycles, to happen failures due to thermal fatigue.

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