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Numerical investigations of the impact of a novel turbulator configuration on the performances enhancement of heat exchangers

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JOURNAL OF ENERGY STORAGE 2022年 46卷

作者： Salhi, Jamal-Eddine Zarrouk, Tarik Merrouni, Ahmed Alami Salhi, Merzouki Salhi, Najim First Mohammed Univ Fac Sci Lab Mech & Energy Oujda 60000 Morocco Mohammed 1er Univ Fac Sci Dept Phys Equipe Sci Mat Energies Nouvelles & ApplicatLab Oujda 60000 Morocco

This paper presents an numerical simulation of the thermo-fluid characteristics for a heat exchanger with smooth concentric double tube equipped by Turbulators operating in the turbulent regime with Reynolds numbers from 3000 to 17,000. This heat exchanger is designed to provide a tubular heat energy exchange from a primary fluid (hot air) to a secondary fluid (cold water) in order to ensure efficient heat transfer with less heat loss. The main focus of this work is the development of a novel configuration for the exchangers with the insertion of a small baffle turbulators on it. These tabulators act as a turbulence promoters for enhancing the thermal performance of the heat exchanger system. Besides, the optimization of these turbulators is assessed by evaluating different baffles configuration and the influence of the pitch distance between them on the thermos-hydrodynamic behavior of the coolant flow. To evaluate the performance of the proposed configuration we evaluated a bench of thermal parameters, mainly Nusselt number, the friction factor, the thermal performance factor, the turbulent viscosity, the temperature field and the velocity field among others. After that, correlations between the Reynolds and Nusselt numbers and Reynolds and the friction factor were conducted for the whole configurations. Results show that the structure of the flow is strongly influenced by the shape and dimensions of inserted baffles. The Nusselt number and the friction factor increase when the inter-Turbulator distance is reduced. Also, the separating of the tube by the insert of the turbulators induces a vortex flow which leads to the improvement of the forced convection. The improvements in heat transfer (eta TPF) is also evaluated using turbulators with different pitches (260;108.57;67.27 and 48 mm). These configurations leads to an increase of eta TPF with 2.36;2.42;2.53 and 2.71 in respect to the pitches mentioned above. Besides, the outlet temperatures are respectively equa

关键词： Turbulator Heat exchangers Turbulence regime Forced convection simple algorithm Computational fluid dynamics

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Numerical simulation of buckling and asymmetric behavior of flexible filament using temporal second-order immersed boundary method

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INTERNATIONAL JOURNAL OF NUMERICAL METHODS FOR HEAT & FLUID FLOW 2020年第3期30卷 1047-1095页

作者： Kanchan, Mithun Maniyeri, Ranjith Natl Inst Technol Dept Mech Engn Surathkal India

Purpose The purpose of this paper is to perform two-dimensional numerical simulation involving fluid-structure interaction of flexible filament. The filament is tethered to the bottom of a rectangular channel with oscillating fluid flow inlet conditions at low Reynolds number. The simulations are performed using a temporal second-order finite volume-based immersed boundary method (IBM). Further, to understand the relation between different aspect ratios i.e. ratio of filament length to channel height (Len/H) and fixed channel geometry ratio, i.e. ratio of channel height to channel length (H/Lc) on mixing and pumping capabilities. Design/methodology/approach The discretization of governing continuity and Navier-Stokes equation is done by finite-volume method on a staggered Cartesian grid. simple algorithm is used to solve fluid velocity and pressure terms. Two cases of oscillatory flow conditions are used with the flexible filament tethered at the center of bottom channel wall. The first case is sinusoidal oscillatory flow with phase shift (SOFPS) and second case is sinusoidal oscillatory flow without phase shift (SOF). The simulation results are validated with filament dynamics studies of previous researchers. Further, parametric analysis is carried to study the effect of filament length (aspect ratio), filament bending rigidity and Reynolds number on the complex deformation and behavior of flexible filament interacting with nearby oscillating fluid motion. Findings It is found that selection of right filament length and bending rigidity is crucial for fluid mixing scenarios. The phase shift in fluid motion is also found to critically effect filament displacement dynamics, especially for rigid filaments. Aspect ratio, suitable for mixing applications is dependent on channel geometry ratio. Symmetric deformation is observed for filaments subjected to SOFPS condition irrespective of bending rigidity, whereas medium and low rigidity filaments placed in SOF condition sh

关键词： Finite volume method Immersed boundary method Flexible filament Low Reynolds number simple algorithm

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Numerical simulation of pollutant dispersion in the residential areas with continuous grass barriers

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INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCE AND TECHNOLOGY 2020年第1期17卷 525-540页

作者： Issakhov, A. Omarova, P. Al Farabi Kazakh Natl Univ Alma Ata Kazakhstan Kazakh British Tech Univ Alma Ata Kazakhstan

In this paper, numerical modeling of the movement and dispersion of pollutant emissions between houses as well as the effect of a continuous barrier on the spread of pollutants was considered. To solve this problem, a system of Reynolds-averaged Navier-Stokes equations was used, and various turbulent models were applied to close this equation system. To test the mathematical model, the numerical algorithm and the choice of the optimal turbulent model, the test problem was solved numerically. The obtained numerical results were compared with experimental data and the results of modeling by other authors. After checking the mathematical model, the numerical algorithm and the choice of the optimal turbulent model, the main problem describing the process of pollutant emissions between houses using continuous grass barriers was solved. In this problem, the distribution of pollutants was considered when using herbal barriers and the optimal height for these barriers was chosen. For the simulation, the RNG k-epsilon turbulence model was applied, which was chosen from the obtained results of the test problem. The numerical simulation results were compared with the obtained calculated data using different heights of solid grass barriers. And it was found that when using a solid grass barrier with a height of 0.1 m, the concentration value drops by more than 1.5 times compared with that without using a barrier, and further increasing the height of the barrier does not give the desired result.

关键词： Residential areas Pollutant dispersion simple algorithm Large eddy simulation (LES) Reynolds-averaged Navier-Stokes (RANS)

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The Earth to Air Heat Exchanger for Reducing Energy Consumption in South Algeria

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INTERNATIONAL JOURNAL OF HEAT AND TECHNOLOGY 2022年第1期40卷 304-310页

作者： Sehli, Abdelkrim Tamali, Mohamed Belkadi, Mostapha Merabti, Ahmed Benabdelrrahmane, Farhat Tahri Mohamed Univ Lab Energy Arid Area ENERGARID BP 417 Bechar 08000 Algeria Mohamed Boudiaf Univ Sci & Technol Dept Mech Engn Oran 31000 Algeria

In Algeria, the construction sector accounts for 30% of the country's final energy consumption. The integration of passive or semi-passive cooling/heating systems in construction is now essential for the reduction of energy consumption while improving thermal comfort. Amongst the systems used is the air-to-ground exchanger. It consists of tubes buried at a depth of 2 to 4 m in which the ambient air is pushed in order to be cooled/heated in contact with the ground whose temperature is almost constant throughout the year. This temperature, which is highly dependent on weather conditions, is about 24 degrees C in Bechar, a region located in south-west of Algeria. The cooled/heated air was blown into the building. The objective of the present study is to highlight the possibility of installing and using this system in arid regions. The mathematical model established to calculate the temperature at the outlet of the exchanger, based on the k-epsilon turbulence equations and the energy equation, discretized by the finite volume method. For the temperature distribution in the soil, a simple analytical solution is developed. The parameters of (1) the length diameter ratio (alpha), (2) the Reynolds number, and (3) the depth of burial was studied. The results obtained are validated with the experimental device installed at the University of Biskra, a region in the south-east of Algeria. Sand, as a soil type, gives a constant annual temperature of 21 degrees C at a depth of 3m. For Reynolds equals 7500 and the ratio, alpha=250 gives a temperature at the outlet of the ground air exchanger equal to 24 degrees C. An optimal solution was chosen for the installation of the ground air exchanger in south-western Algeria.

关键词： ground air heat exchanger turbulent k-epsilon model finite volume method simple algorithm soil temperature

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Starting Flow by Pitch Acceleration of Flat-Plate Foil

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AIAA JOURNAL 2020年第10期58卷 4287-4303页

作者： Yu, Huai-Te Natl Def Univ Dept Mech & Aerosp Engn Chung Cheng Inst Technol Taoyuan 33551 Taiwan

This paper presents the investigation of the starting flow in association with pitch acceleration using transient laminar-flow computation and an unsteady inviscid-flow theory. A thin flat-plate foil pitched at the leading edge is modeled in a two-dimensional incompressible fluid at chord Reynolds numbers of the order of 10(3). Several acceleration amplitudes (1.1 <= alpha(m)'' t(c)(2) <= 17.0) and acceleration durations (0.0693 <= beta = Delta alpha/alpha(m) = Delta t/t(p) <= 0.5) are maneuvered using a modified canonical kinematic equation at reduced pitch rates from 0.196 to 0.763. Comparisons between computational and theoretical data reveal that the formation of the starting vortex is determined by the acceleration amplitude scaled by the square of the convective time. The corresponding starting force coefficient that scales with the dimensionless acceleration amplitude is proportional to the acceleration angle Delta alpha, which decreases with increasing reduced pitch rate. The starting vortex, once formed at the trailing edge, is shed at the end of the acceleration period. The quasi-steady theory that includes only pitch motion as the strength of the dipolar sheet for apparent-mass flow can also yield an acceptable approximation to capture the apparent-mass force coefficient spike in acceleration.

关键词： Trailing Edges Vortex Shedding Phenomena Freestream Conditions Incompressible Flow Mass Flow Lift Coefficient Pressure Coefficient simple algorithm Thin Airfoil Theory Particle Image Velocimetry

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Numerical investigation and characteristic analysis of the swirl meter with different swirlers

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MEASUREMENT & CONTROL 2020年第7-8期53卷 1122-1130页

作者： Chen, Desheng Lin, Zhe Liu, Qi Wang, Yanping Wu, Fei Wu, Dongyang Zhejiang Sci Tech Univ Key Lab Fluid Transmiss Technol Zhejiang Prov Second Ave 928 Hangzhou 310018 Zhejiang Peoples R China Zhejiang Testing & Inspect Inst Mech & Elect Prod Hangzhou Peoples R China Hangzhou Oxygen Plant Grp Co Ltd Hangzhou Peoples R China

The swirl meter is one of the gas flow meters used in the industry. Its advantages are as follows: a strong signal level, easy maintenance, and stable performance. Hence, it has become widely accepted for natural gas metering. In this study, the numerical computation of the three-dimensional unsteady flow in a swirl meter was conducted using the renormalization group k-epsilon turbulence model and simple algorithm. The internal flow fields were analyzed in detail, wherein the velocity and pressure distributions were discussed under six flow rates (6, 15, 25, 40, 70, and 100 m(3)/h) and three swirl cone angles (11 degrees, 20 degrees, and 30 degrees). The obtained results are reported and discussed as follows: the stable performance of the swirl meter was due to its capacity to maintain its internal characteristics over a large flow range. Also, it was detected that though the pressure decrease was gradual on the wall, an opposite tendency was shown at the center. On the other hand, the swirler structure was crucial to the metering capacity of the swirl meter, and the swirler cone angle influenced the pressure and velocity.

关键词： Swirl meter numerical simulation simple algorithm swirler cone angle pressure distribution

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Numerical study of thermal influence to pollutant dispersion in the idealized urban street road

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AIR QUALITY ATMOSPHERE AND HEALTH 2020年第9期13卷 1045-1056页

作者： Issakhov, Alibek Omarova, Perizat Issakhov, Assylbek Al Farabi Kazakh Natl Univ Alma Ata Kazakhstan Kazakh British Tech Univ Alma Ata Kazakhstan

In this paper, a computational study of air pollution in idealization urban canyons road for various temperature regimes was investigated. To solve this problem, the Reynolds-averaged Navier-Stokes (RANS) equations were used. Moreover, different turbulent models were used to close this system of equations. To test the numerical algorithm and the mathematical model, the test case was performed. The received computational data for different turbulent models were compared with measurement and computational values. After validating the computational and mathematical model, the main problem was characterized: the pollutant emissions process between houses using different grass barrier types (continuous and discontinuous) for different temperature regimes. The computational data were compared with the obtained computational values using various grass barriers types. In the various studies, it was revealed that the presence of barriers along the roads reduces the harmful concentrations in the air. So when using a herbal barrier height of 10 cm, the concentration value drops to a cross-section ofx= 5 cm more than 1.5 times compared with no barriers, however, taking into account the temperature effect (T-H= 305 K), the concentration value additionally decreases almost 2 times. Increasing the temperature for the roadside with barrier reduces dispersion and deposition of pollutants.

关键词： Thermal effects Residential areas simple algorithm Pollutant dispersion Reynolds averaged Navier-Stokes (RANS)

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Numerical study of the thermo-energy of a tubular heat exchanger with longitudinal baffles

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Materials Today: Proceedings 2021年 45卷 7306-7313页

作者： Jamal-Eddine Salhi Tarik Zarrouk Najim Salhi Laboratory of Mechanics and Energy Faculty of Sciences First Mohammed University Oujda 60000 Morocco

The work undertaken in this paper presents a computational study of the flow and heat transfer characteristics in a tubular heat exchanger with longitudinal baffles attached to its inner wall, which is maintained at a constant temperature T w  = 343 k. This study is carried out for a Reynolds number, Re ranging from 2 × 10 4 to 3 × 10 4 , and was devoted first to the case of a smooth tube (without baffles), then to the case of a tube provided with longitudinal baffles of rectangular cross-section, and finally to the case of a tube provided with longitudinal baffles of triangular cross-section. The system of equations governing the thermohydraulic phenomenon consists of the continuity equation (for mass conservation), the Navier-Stokes equations (for momentum conservation), and the first principle equation (for energy conservation). The system of equations thus formulated is a hyperbolic system, which has been solved numerically over the entire domain, using the finite volume approach for its discretization, and the two-equation model (K-ε) for the modeling of turbulence terms. The simple algorithm is thus used to overcome the problem of velocity–pressure coupling. To meet the needs of aerothermal users. The two fields, thermal and aerodynamic, were analyzed, the friction factor, the Nusselt number, and the thermal efficiency. Finally, the study undertaken was finalized by comparative analysis to identify the relevant parameters in the aerothermal phenomenon and deduce the optimal form to be proposed to aerothermal energy users. The results obtained show that the longitudinal inclusion of the rectangular section baffles improves the thermal performance by 32.37% for the triangular section, and by 44.37% for the case of rectangular section baffles.

关键词： simple algorithm Baffle Nusselt number Heat transfer Cfd Friction factor

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Numerical Simulations of Heat Transfer Phenomena through a Baffled Rectangular Channel

INTERNATIONAL JOURNAL OF MATHEMATICAL ENGINEERING AND MANAGE...

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INTERNATIONAL JOURNAL OF MATHEMATICAL ENGINEERING AND MANAGEMENT SCIENCES 2021年第5期6卷 1230-1241页

作者： Saha, Sandip Biswas, Pankaj Das, Apurba Narayan Natl Inst Technol Silchar Dept Math Silchar 788010 Assam India Alipurduar Univ Dept Math Alipurduar 736121 W Bengal India

In presence of baffle, the turbulent airflow phenomena as well as forced convective heat exchange characteristics in twodimensional rectangular channel have been analyzed in this work. For variations in Reynolds number (Re), we have studied the variations in characteristics of thermal behavior due to the change in the shape of baffle. Computations have been done using finite volume method (FVM) and FLUENT software and the simple algorithm has been employed for solving the governing equations. Finally, the flow and thermal exchange characteristics viz., streamline flow, turbulence intensity (TE), axial velocity, turbulence kinetic energy (TKE), normalized friction factor (F), normalized average Nusselt number (Nuavg) and thermal enhancement factor (TEF) have been studied in details from numerical standpoint. It has been found that the triangular shaped baffle provides highest value of F at Re = 30,000 and at Re = 46, 000, the maximum value of the TEF is found for the same baffle implying that triangular shaped baffle is more suitable for overall purposes.

关键词： Turbulent airflow Fluent FVM simple algorithm Thermal exchange characteristic

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Dynamics of Flexible Filament in Viscous Oscillating Flow 1

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7th Asian Joint Workshop on Thermophysics and Fluid Science (AJWTF)

作者： Kanchan, Mithun Maniyeri, Ranjith Natl Inst Technol Dept Mech Engn Biophys Lab Mangalore 575025 Karnataka India

ISBN: (数字)9789811518928

ISBN: (纸本)9789811518928;9789811518911

The dynamics of flexible filament in a viscous fluid is a complex fluid-structure interaction problem that has wide scientific and engineering applications in emerging fields such as biomimetics and biotechnology. Coupling the structural equations with fluid flow poses a number of challenges for numerical simulation. In this regard, techniques like immersed boundary method (IBM) have been quite successful. In the present study, a two-dimensional numerical simulation of flexible filament in a rectangular channel with an oscillating fluid flow at low Reynolds number is carried out using IBM. The discretization of governing continuity and Navier-Stokes equation is done by finite volume method on a staggered Cartesian grid. simple algorithm is used to solve fluid velocity and pressure terms. The filament mechanical properties like stiffness and bending rigidity are incorporated into the governing equation via Eulerian forcing term. An oscillating pressure gradient drives the fluid while the flexible filament is fixed to the bottom channel wall. The simulation results are validated with filament dynamic studies of previous researchers. The interaction of the filament with nearby oscillating fluid motion is well captured by the developed numerical model.

关键词： Fluid-structure interaction Immersed boundary method Low Reynolds number simple algorithm Oscillating fluid

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