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Three-dimensional numerical analysis of the impact of the orientation of partially inclined baffles on the combined mass and heat transfer by a turbulent convective airflow

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INTERNATIONAL JOURNAL OF ENERGY AND ENVIRONMENTAL ENGINEERING 2023年第1期14卷 79-94页

作者： Salhi, Jamal-Eddine Zarrouk, Tarik Hmidi, Nassreddine Salhi, Merzouki Salhi, Najim Chennaif, Mohammed Fac Sci Equipe Sci Mat Lab LPTPME Dept Phys Energies Nouvelles & Applicat Mohammed 1er Oujda 60000 Morocco First Mohammed Univ Fac Sci Oujda 60000 Morocco Univ Mohammed 1st Lab Elect Engn & Maintenance LEEM High Sch Technol Oujda Morocco

This paper performed a three-dimensional numerical analysis of the flow structure and heat transfer enhancement of turbulent airflow through a rectangular channel (without baffles, with baffles). Two partially inclined baffles with different orientations are mounted on the bottom and top walls of the channel. The location of the baffles in the direction of flow through the channel of a heat exchanger is of great importance. It depends mainly on the geometrical parameters and the orientation of the baffles. Hence, our study focused on analyzing the effects of the baffles on the thermal-hydraulic behavior in the exchanger by choosing a flat baffle and four configurations of different orientations. Numerical results are presented in terms of axial velocity U, isotherms (T), turbulent kinetic energy (k), amount of heat dissipated by the channel surfaces (Q), average Nusselt number (Nu), friction factor (f), and thermal performance factor (n). The results show that the insertion of the partially inclined baffles into the channel causes the generation of vortices in the upstream and downstream areas of the baffle location point. Thus the mixing phenomenon occurs, which induces an increase in the heat transfer rate and generates a pressure drop simultaneously. Furthermore, the analysis of the results shows that compared to the smooth case (without baffles), the thermal performance factor (eta) is significantly higher in the four configurations with baffles. Thus, for the different cases studied: (2);(3);(4);(5) and (6), the factor (eta) is equal to 2.18;2.16;2.19;2.27;and 2.25, respectively, for a Reynolds number equal to 87,300. The results also indicate that the transmitted relative heat quantities are equal to 116.08, 113.93, 118.2, 121.71, and 109.39%, respectively, for the same cases considered. Therefore, the configuration corresponding to case (5) performs better in heat transfer than the others. Finally, new correlations for predicting friction factor and Nusselt n

关键词： Heat transfer Numerical analysis Turbulent flow Heat exchangers simple algorithm Computational Fluid Dynamics

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Control volume method for the thermal convection problem in a rotating spherical shell: Test on the benchmark solution

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STUDIA GEOPHYSICA ET GEODAETICA 2004年第4期48卷 741-746页

作者： Hejda, P Reshetnyak, M Acad Sci Czech Republ Inst Geophys CR-14131 Prague Czech Republic Russian Acad Sci Inst Phys Earth Moscow 123995 Russia Moscow MV Lomonosov State Univ Ctr Res Comp Moscow 119899 Russia

The development of the control volume method for the thermal convection problem in a rotating spherical shell is presented. In contrast to the spectral methods, commonly used in geodynamo simulations, the control volume method belongs to the class of grid methods (the solution is approximated by a set of discrete values in physical space). In the present paper we concentrate on some problems of convergence and stability of the method. Case 0 of the numerical dynamo benchmark (Christensen et al., 2001, Phys. Earth Planet. Inter., 128, 25-34) was used to check the correctness of our computer code. The results demonstrate good convergence to the suggested standard solution.

关键词： liquid core dynamo benchmark finite volume method simple algorithm

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A novel pressure-velocity formulation and solution method for fluid-structure interaction problems

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JOURNAL OF COMPUTATIONAL PHYSICS 2008年第6期227卷 3383-3404页

作者： Papadakis, George Kings Coll London Dept Mech Engn London WC2R 2LS England

In the standard approach for simulating fluid-structure interaction problems the solution of the set of equations for solids provides the three displacement components while the solution of equations for fluids provides the three velocity components and pressure. In the present paper a novel reformulation of the elastodynamic equations for Hookean solids is proposed so that they contain the same unknowns as the Navier-Stokes equations, namely velocities and pressure. A separate equation for pressure correction is derived from the constitutive equation of the solid material. The system of equations for both media is discretised using the same method (finite volume on collocated grids) and the same iterative technique (simple algorithm) is employed for the pressure-velocity coupling. With this approach, the continuity of the velocity field at the interface is automatically satisfied. A special pressure correction procedure that enforces the compatibility of stresses at the interface is also developed. The new method is employed for the prediction of pressure wave propagation in an elastic tube. Computations were carried out with different meshes and time steps and compared with available analytic solutions as well as with numerical results obtained using the Flugge equations that describe the deformation of thin shells. For all cases examined the method showed very good performance. (C) 2007 Elsevier Inc. All rights reserved.

关键词： fluid-structure interaction finite volume method simple algorithm elastodynamic equations flexible tube pressure wave propagation

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Analysis of the thermohydrodynamic behavior of a cooling system equipped with adjustable fins crossed by the turbulent flow of air in forced convection

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INTERNATIONAL JOURNAL OF ENERGY AND ENVIRONMENTAL ENGINEERING 2022年第3期13卷 1039-1051页

作者： Salhi, Jamal-Eddine Salhi, Merzouki Amghar, Kamal Zarrouk, Tarik Salhi, Najim First Mohammed Univ Fac Sci Lab Mech & Energy LME Oujda 60000 Morocco Abdelmalek Essaadi Univ Natl Sch Appl Sci BP 03 Ajdir Al Hoceima Morocco

The present study focused on researching a technique that can make a cooling system more efficient in terms of heat transfer. To achieve this, it is possible to modify the thermal conductivity of its cooling fluid or the structure of its flow. In this study, we have opted for the second technique. To do this, we sought to create singularities in the flow by inserting vertical and rotating baffles around the vertical. The study field is a channel of rectangular section, placed horizontally, and crossed by the incompressible and turbulent flow of a fluid (air) in forced convection. Geometrically, the physical problem describes mathematically. A system of hyperbolic equations governs it;Navier-Stokes equations derive from the laws of conservation of mass and momentum and the state's law that derives from the principle of conservation of energy. A finite volume scheme ensures the discretization of the governing equations and the numerical analysis's boundary conditions. The turbulence is modeled using the standard k-e model, while the pressure-velocity coupling problem solves by applying the simple algorithm. The proposed numerical computational model validates by comparing the computed results with those of literature correlations. The model was then applied to practical cases where a Reynolds number in the range (12,000, 16,000) has chosen. The orientation angle (theta) of the baffles is chosen equal to (0 degrees, 5 degrees, 7 degrees, 13 degrees, 15 degrees) with a different orientation direction. The calculated results are presented in map form for the different physical fields (of axial velocity, temperature) or in graphical form for the different factors and coefficients (friction factor, amount of heat removal, average Nusselt numbers, and thermal performance factor). The results obtained show that the system is made more efficient with a thermohydrodynamic behavior that varies significantly with the baffles' orientation. The heat transfer rate increased, and th

关键词： Heat transfer Fins Turbulent flow Nusselt numbers simple algorithm Friction factor

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Temperature-explicit formulation of energy equation for thermal-hydraulic analyses

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INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER 2010年第3期37卷 256-260页

作者： Kim, Jongtae Ha, Kwang Soon Kim, Sang-Baik Korea Atom Energy Res Inst Dept Thermal Hydraul Safety Res Taejon 305353 South Korea

A temperature equation which is derived from an enthalpy transport equation by using an assumption of a constant specific heat is very attractive for analyses of heat and fluid flows. It can be used for an analysis of a solid-fluid conjugate heat transfer, and it does not need a numerical method to obtain temperature from a temperature-enthalpy relation. But its application is limited because of the assumption. A new method is derived in this study, which is a temperature-explicit formulation of the energy equation. The enthalpy form of the energy equation is used in the method. But the final discrete form of the equation is expressed with temperature. The discretized equation from the temperature-explicit formulation can be used for a heat transfer analysis in a solid-fluid coupled region without any special treatment at the solid-fluid interface. And it can be applied for multiphase flows with a real gas effect. It is found by numerical tests in this study that the proposed method is very efficient and as accurate as the standard enthalpy formulation. (C) 2009 Elsevier Ltd. All rights reserved.

关键词： Segregated method simple algorithm Energy equation Temperature form Enthalpy form Temperature-explicit formulation

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New Criterion for Local Thermal Equilibrium in Porous Media

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JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER 2008年第4期22卷 649-653页

作者： Zhang, Xuewei Liu, Wei Huazhong Univ Sci & Technol Wuhan 430074 Peoples R China

In this paper, a general criterion for local thermal equilibrium in forced convection flows through porous media under a constant heat flux boundary condition is presented in terms of parameters, including the boundary heat flux, the area of cross section, the effective thermal solid-to-fluid conductivity ratio, characteristic length for pore size, porosity, Nusselt number, fluid conductivity, and the heat source of solid phase. To check the validity of the proposed criterion for local thermal equilibrium, the forced convection phenomena in the porous medium between two parallel plates subjected to constant heat flux are studied by numerical method based on the Brinkman-Forchheimer extended Darcy model. The temperature difference between solid and fluid phases in a representative elementary volume are studied by comparing the effects of relevant parameters in this new criterion. In addition, the proposed criterion is consistent with the existing experimental and numerical results for convection heat transfer in a porous medium.

关键词： Heat Transfer Coefficients Thermal Conductivity Boundary Heat Flux Natural Convection Thermal Diffusivity Darcy Number Incompressible Flow Finite Volume Method simple algorithm Temperature Fields

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Shock-Tunnel investigation of hypervelocity free shear layers in a planar duct

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JOURNAL OF PROPULSION AND POWER 1996年第5期12卷 998-1001页

作者： Buttsworth, DR Morgan, RG UNIV QUEENSLAND DEPT MECH ENGNST LUCIAQLD 4072AUSTRALIA

Pitot pressure measurements obtained in four different developing hypervelocity free shear layers are reported. There exists a high degree of similarity across the present four mixing cases, including the case where the primary and secondary stream flow velocities were approximately matched. It is inferred that it is probable that the relatively large primary stream boundary layers had a strong influence on these developing shear layers. There was reasonable agreement between the experimental results and predictions made using a parabolized Navier-Stokes code with a k-epsilon turbulence model. (AIAA)

关键词： Boundary Layer Thickness Shock Tunnels Stagnation Pressure Contoured Nozzles Compressibility Turbulence Models Static Pressure Scramjet simple algorithm Combustion Process

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DIFFERENCING OF DENSITY IN COMPRESSIBLE FLOW FOR A PRESSURE-BASED APPROACH

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AIAA JOURNAL 1994年第3期32卷 659-661页

作者： GREYVENSTEIN, GP MEYER, JP Potchefstroom University for CHE Potchefstroom 2520 South Africa

Because of the difference in nature between compressible and incompressible flows, different computational schemes have been developed through the years to deal with these two types of flows. In the case of compressible flows, methods have been developed that use density as a primary variable, Such methods are known as density-based methods. Examples of density-based methods are the well-known emthods of MacCormack and Beam and Warming. Unlike density-based methods, pressure-based methods use pressure as a primary variable. Examples of pressure-based methods are the well-known simple and PISO method. The purpose of this paper is to investigae the differencing scheme of density used for the convection terms in the momentum transport equations. To provide a clear understanding, we will discuss these concepts in the framework of a one-dimensional scheme. Fortunately, all of these concepts as developed within this one-dimensional framework are readily extended to two or three dimensions.

关键词： One Dimensional Flow Continuity Equation Convection Heat and Mass Transfer simple algorithm Inlet Pressure Mass Flux Numerical Heat Transfer Explicit Methods Rockets

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Numerical simulation of the cold flow in an axisymmetric non-compressing engine-like geometry

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INTERNATIONAL JOURNAL OF ENERGY RESEARCH 1999年第10期23卷 899-908页

作者： Bilgin, A Karadeniz Tech Univ Dept Mech Engn TR-61080 Trabzon Turkey

Fluid motion within the cylinder of a piston engine has a major influence on the performance of the engine. The general motion within the cylinder and the associated turbulence affect the charge stratification, combustion and heat transfer processes. In order to predict the charge stratification, one must understand and be able to predict the turbulent mixing processes (Reynolds, 1980). There are numerous alternative turbulence modelling approaches of varying degrees of complexity, but two of them, k-epsilon turbulence models and Reynolds stress models, are commonly used in engine modelling activities. In the present study, k-epsilon turbulence model was used to predict the how in the cylinder of a non-compressing engine-like configuration. Wall function treatment was employed in order to bridge the wall layer to the inner region. Finite volume method incorporated with hybrid (central/upwind) spatial and implicit temporal schemes, and simple algorithm (Patankar, 1980) were used to obtain numerical solutions. Results were compared with the measurements of Morse et al. (1978) and predictions of Gosman et al. (1980). Although the degree of agreement between the predictions and the measurements varies throughout the cycle and the flow field, the overall agreement is found to be satisfactory. Copyright (C) 1999 John Wiley & Sons, Ltd.

关键词： reciprocating engine flow k-epsilon turbulence model finite volume wall-functions simple algorithm

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Steam-Assisted Cracking of n-Dodecane in a Packed-Bed Reactor for Hypersonic Thermal Management

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JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER 2021年第4期35卷 696-707页

作者： Smith, Bradley J. Ervin, Jamie S. Reitz, Thomas L. Univ Dayton Mech & Aerosp Engn Dayton OH 45469 USA US Air Force Res Lab Wright Patterson AFB OH 45433 USA

Heat removal capacity of catalytically cracked supercritical n-dodecane as a jet fuel analogue in a cylindrical packed-bed reactor is examined. Fuel cracking is endothermic, and can be used in designing a potential hypersonic vehicle thermal management system. In this work, n-dodecane endotherm and product distributions were examined using a platinum catalyst on a ceramic support matrix. Although many previous fuel studies have used catalyst coated tubes, this study made use of a solid catalyst structure in a packed bed to distribute the catalyst throughout the fuel flow in order to provide more surface catalyst sites. The packed-bed reactor was treated as an ideal plug flow reactor, which assumes catalytic reactions that are radially uniform across the reactor diameter. Additionally, water was added to study its mitigation effect on coke formation and deposition on the reactor catalyst. Many previous jet fuel studies have either used a catalyst to aid in endothermic thermal management or have focused on water addition to reduce coke formation. This study combines these approaches. A catalyst is used to initiate endothermic reactions at lower temperatures than would ordinarily be achieved by thermal cracking alone, in conjunction with steam addition to mitigate coking. The packed-bed catalyst configuration provides catalytic action even as temperatures increase and thermal cracking becomes dominant, thereby enhancing the chemical heat sink. Water addition also provided coking mitigation, although with an associated decrease in dodecane conversion, and, hence, heat sink capability.

关键词： Thermal Management Catalysis Heat Exchangers Vehicle Thermal Management Jet Fuel Endothermic Reactions Heat of Formation Surface Thermocouples Fuel Pyrolysis simple algorithm

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