bluuebunny/crossref_metadata_2025_split huggingface dataset:
LES investigations of turbulent heat transfer structures with exponential power escalation
Authors: Roumet Elie , Nop Raksmy , Dorville Nicolas , Duluc Marie-Christine 
Published: June 2024

Abstract
The BORAX-type accident is a key scenario in the safety design of pool-type experimental nuclear reactors. It considers a reactivity insertion large enough to initiate an exponential power escalation with a period as small as tens of milliseconds, necessitating effective heat removal by the coolant system. This study presents a computational analysis of single-phase transient heat transfer under thermal-hydraulic conditions relevant to such reactors, focusing on turbulent channel flow between planar fuel plates with highly subcooled water. Our investigation uses Large Eddy Simulation (LES) performed with TrioCFD, the open-source CFD code developed by the French Atomic Energy Commission (CEA). Several modeling options are tested: incompressible flow with temperature as a passive scalar, incompressible flow with varying viscosity, and quasicompressible flow with temperature-dependent viscosity and mass density. To evaluate the accuracy of our physical models, all simulations were performed under uniform conditions, using the same experimental parameters, mesh, and numerical strategies. The specific examined scenario involves a highly subcooled turbulent channel flow at moderate pressure, experiencing an exponential power increase. We ensure detailed turbulence resolution at the Batchelor scale in the wall normal direction close to the heating wall. This communication presents a comparative study of LES simulations of the single-phase flow under exponential power excursion at the wall. Subsequent analyses focused on the impact of different velocity-temperature couplings on the prediction of wall heat transfer, incorporating comparisons with experimental infrared thermometry measurements. Early in the transient phase, temperature peaks are confined within turbulent streaks, as reported in the existing literature. However, as the exponential power transient unfolds, the viscous layer and streak structures destabilize, leading to a more dispersed distribution of hot spots. Preliminary findings suggest a transition in heat transfer modes from turbulence-driven to conduction during the final stages of the single-phase transient.
The influence of cold plate height on thermal management of a liquid-cooled battery pack
Authors: Birinci S , Albayrak M , Saglam M , Sarper B , Aydin O 
Published: June 2024

Abstract
This study focuses on the numerical investigation of the cooling efficiency of a cold plate with different heights for a Li-ion battery pack. The battery pack is arranged in a 2×18 configuration and consists of cylindrical 18650 cells. A new cold plate design is presented for this purpose, and the thermal performance of the system is evaluated under various operating scenarios. Five-volume flow rates (0.1-1.0 l/min) and four distinct cold plate heights (30-40-50-60 mm) are investigated for the 2C discharge rate using ANSYS Fluent software. The study investigates several configurations to establish the maximum temperature difference within the BP, maximum temperature of the BP, pressure drop, and cooling efficiency. As a result of the simulations the ideal flow rate is founded within the range of 0.5-0.75 l/min and a cold plate height of 50 mm is selected as the most favorable design configuration.
Optimum geometry of some heat exchangers
Authors: Karvinen R 
Published: June 2024

Abstract
Heat exchangers are present in our daily living and industrial applications. The size scale of heat exchangers is very large ranging from very small chips in electronics to huge equipment in process and energy industry. In the paper optimization approaches of some industrial examples are given. The goal is to present how analytical results can and must be used in multi-objective optimization of applications. The details of equations are not given due to page limits but they are found in the literature. The main goal is to show how numerical, analytical and optimization methods can be and must be combined in optimization of exchanger design and performance. The performance depends on very many factors and contradictory requirements must take into account such as maximization of heat transfer and simultaneously minimize for example the weight and size. Modifications of four existing applications are component placement on a wiring board, optimization of heat sink in power electronics, quality control in a glass tempering and optimization of a very huge heat exchanger called economizer in a recovery boiler.
Thermal performance against gravity of an AlSi10 AM heat pipe with a diamond lattice structure
Authors: Vitali L , Menini S , Guilizzoni M , Niro A 
Published: June 2024

Abstract
Metal Additive Manufacturing has gained momentum as a viable production technique for specialized heat transfer devices, in particular for industrial sectors characterized by small production numbers associated with high-performance requirements. Within the space industry, ESA is leading and funding several applied research programs to explore the possibility to employ AM for building electronic boxes with embedded heat pipes, in order to reduce manufacturing post-processing steps and contact thermal resistances. In the context of tender 1-10238, the project “Heat Pipe Solutions for High Power Systems” (HPS2) has developed and tested lattice-based heat pipes, that are intended to be integrated in electronic modules. In this paper, the heat transfer performances as function of input power and tilt angle against gravity of a 150 mm long heat pipe with a 20 mm evaporator section and a 40 mm condenser section are presented and compared with the results of the models of performance limits, based on the measured properties of the lattice.
Experimental and numerical convective heat transfer performance analysis of a confined impinging round jet with triangular tabs under crossflow influence
Authors: Saglam M , Birinci S , Sarper B , Aydin O 
Published: June 2024

Abstract
In this study convective heat transfer performance of a confined impinging round jet with/without nozzle tabs under channel crossflow is investigated experimentally and numerically for a wall mounted heated module. Numerical investigations are carried out for different jet to crossflow velocity ratios (Vr) and compared to experimental data. Four different Vr values (5,6,8, and 10) are tested for single target plate distance to jet nozzle diameter ratio (H/D=8). ANSYS Fluent software is used for numerical simulations while infrared thermography is utilized for experimental investigations. Surface temperature values of the wall mounted module are obtained and presented along with complex flow structures obtained via numerical simulations. Results show that crossflow has decisive effect on temperature distribution on the component. By inserting triangular tabs to the nozzle exit, it is possible to further decrease the surface temperature of the module and minimize the crossflow caused jet deflection. The addition of triangular tabs resulted in a significant increase of up to 10% in the mean Nusselt number on the top surface of the module at Vr=10.
Design and numerical simulation of a 45 kWel multi-source high-flux solar simulator as a heating source of dielectric materials positioned in a microwave characterization cavity
Authors: Touoyem Talla J A , Henriot B , Duvaut T , Tantot O , Delhote N , Charles M , Randrianalisoa J 
Published: June 2024

Abstract
This study reports the design and modelling of a high-flux solar simulator (HFSS) combined to a resonant cavity for microwave dielectric properties characterization of ceramics at very high temperatures. The HFSS comprises seven xenon arc lamps with ellipsoidal reflectors, delivering a maximal electrical power of 6.5 kWel each. Positioned on a virtual sphere of around 1600 mm radius, the lamps provide concentrated irradiation heating on a sample positioned inside the resonant cavity. The propagation of the lamp’s irradiation to the sample and the cavity is simulated using Monte Carlo ray tracing method. An ANSYS Fluent finite volume method for solving the resulting multimode heat transfer and flow indicate a radiative flux reaching 1.84 MW m−2, and a sample temperature of approximately 1470°C with 10 % non-uniformity. These results suggest that the designed heating system and resonant cavity is suitable for conducting microwave dielectric properties characterization of refracting ceramic materials at high temperatures, addressing a gap in studies focusing on temperatures exceeding 1000°C.
Effect of using an ionic liquid as additive in water/LiBr mixture in a horizontal falling film absorber
Authors: Tariq Hussain Ahmed , Bourouis Mahmoud , Coronas Alberto 
Published: June 2024

Abstract
Absorption Heat Pumps (AHPs) are attractive technology for space cooling from low grade energy resources. This technology is of special interest when water/LiBr is used as a working mixture, as water is a natural, non-toxic and cost-effective refrigerant without any contribution to global warming. Nonetheless, water/LiBr AHPs do come with certain inbuilt issues as LiBr tends to crystallize at higher concentrations, that hinder the technology from functioning as an air-cooled system and in a reversible mode for space heating. Addition of Ionic Liquids (ILs) as additive is therefore important which improves the solubility of LiBr in water/LiBr solution. The addition of IL as additive is 1,3-Dimethyl-1H-imidazolium chloride [DMIM][Cl] which is 6% of absorbent (LiBr+IL) by mass. This paper aims to compare the heat and mass transfer involved in water absorption process of water/LiBr and water/(LiBr+[DMIM][Cl]) mixtures in a horizontal tubes falling film absorber.
Particle dispersion produced by a turbulent free convection flow in a room-sized cubical cavity
Authors: Pallares Jordi , Lavrinenko Akim , Marchioli Cristian , Cito Salvatore , Fabregat Alexandre 
Published: June 2024

Abstract
This paper introduces the framework for the ongoing “2024 International CFD Challenge on the Long-Range Indoor Dispersion of Pathogen-Laden Aerosols.” The Challenge is designed as a blind test to assess the accuracy of computationally efficient turbulence modeling techniques, including URANS and LES, in replicating both the hydrodynamics and aerosol dispersion in an idealized indoor environment. To evaluate the simulations, DNS data of turbulent natural flow at a high Rayleigh number within a room-sized enclosure will serve as a reference benchmark. Participants have the flexibility to conduct simulations of the same flow configuration using their preferred CFD software, employing URANS, LES, and/or hybrid methods. The Challenge was officially launched on October 16, 2023, and has garnered participation from 31 teams representing 18 different countries, with the expected submission of results in May 2024. The outcomes of the comparison between the different modelling approaches and the reference DNS will be presented and discussed during the conference.
Numerical simulations of bubbly turbulent convection in cubical geometries
Authors: Marichal J , Ruyer P , Bartosiewicz Y 
Published: June 2024

Abstract
In this work we present numerical results of pool boiling flow in a turbulent Rayleigh-Bénard convection configuration, using our in-house code in a cubical geometry. The problem in hand is encountered in various natural phenomena as well as in industrial applications. An Eulerian-Lagrangian approach is developed for the mixture of liquid water and vapor bubbles. The liquid mean temperature is close to the saturation temperature and is governed by the quasi-incompressible Navier-Stokes equations that are solved using DNS standards. The motion and growth/shrinkage of each individual vapor bubble is modeled and the backward effect of the bubbles on the fluid is accounted via momentum and energy exchanges between the two phases (two-way coupling), as well as variations in fluid phases volumetric fractions (volumetric coupling). In such pool configuration the non-dimensional parameters governing the flow are both those relative to Rayleigh-Bénard convection, namely Rayleigh number, Prandtl number and aspect ratio, and those to boiling, namely the overall vapor volumetric fraction, the bubble size based Reynolds number, the degree of superheat of the liquid scaled by the overall temperature difference, and the Jakob number (sensible heat to latent heat ratio).
At first, we describe the model used and its corresponding validation, involving natural convection, isolated bubble dynamics and coupling between bubbly and bulk flows. In the second part, we consider the study of the relationship between heat transfer through the pool (Nusselt number) and the flow topology for different settings of the bubbly configurations.
Approximate analytical solution for solidification of PCM in cylindrical geometry with temperature‑dependent thermal conductivity-perturbation method
Authors: Jamal-Abad Milad Tajik , Cortés Cristóbal , Ranz Javier Pallarés , Gil Antonia 
Published: June 2024

Abstract
The Solidification process of Phase change materials inside cylindrical enclosures is analyzed and analytical solutions are derived to determine the positions of the interfaces at different time intervals. In this current investigation, we address the scenario involving temperature-dependent thermal conductivity. For the first time, we employ perturbation techniques to analytically derive the dimensional temperature for both phases. Our study specifically incorporates a linear model to account for the variation in thermal conductivity with temperature. The results show that the duration of complete solidification relies on the Stefan number. As these parameter is augmented, the total solidification time of the cylinder diminishes and escalates, respectively. Furthermore, it has been observed that an augmentation in the thermal conductivity of the phase change material (PCM) leads to a swifter solidification process.
Numerical simulations of temperature loads on multilayer Laue lenses
Authors: Rek Z , Chapman H N , Bajt S , Šarler B 
Published: June 2024

Abstract
We present numerical simulations of the heat loads on novel diffractive X-ray optics, known as multilayer Laue lenses, exposed to high-intensity X-ray beams produced by an X-ray free electron laser (XFEL). These lenses can be used to focus XFEL beams to nanometer spots. The temperature distribution within the lens and temperature evolution as a function of incident pulse frequencies were calculated for two different lens geometries and several material pairs and material ratios of the MLLs. Simulations considered the special pulse structure of European XFEL with X-rays being delivered in pulse trains. After defining the geometric model, computational grid, material properties, and boundary conditions, a grid sensitivity study was carried out. We solved the transient heat energy transport equation in solids for mixed boundary conditions. The results of these simulations will help select materials and lens geometry for future XFEL experiments.
Estimation of thermophysical properties of a pouch-type Li-ion battery using an inverse methodology
Authors: J Jithu , Vasista Kasavajhula Naga , Kumar Suraj , Srinivasan Balaji , Balaji C. 
Published: June 2024

Abstract
The growing popularity of electric vehicles highlights the crucial role of batteries. Effective battery thermal management is crucial for improving performance, reliability, and safety, especially in tropical areas where overheating is a key challenge. This necessitates a comprehensive understanding of the thermophysical properties of batteries. The present study concerns the estimation of the temperature-dependent orthotropic thermophysical properties (kx
, ky
, kz
, cp
) of the active material in a pouch-type Li-ion battery using an inverse methodology. An experimental study is conducted on a commercial AMP20M1HD-A Li-ion battery to measure the surface temperature at various locations using thermocouples. The forward model consists of the three-dimensional unsteady conduction problem and is solved in COMSOL using experimental boundary conditions. The data generated is used to train an Artificial Neural Network, which acts as a replacement for the forward model. The Metropolis Hasting-Markov Chain Monte Carlo algorithm along with the Bayesian inference inverse model is used for analyzing the posterior distribution and the average estimates for thermophysical properties are obtained. The temperature dependence study shows a significant correlation between temperature and battery thermophysical properties. The accuracy of the employed inverse model is validated by obtaining the surface temperature using the estimated thermophysical properties and comparing it with the measured surface temperature.
Calibration and verification of CFD-VOF models for the analysis of pressurization scenarios in LH2 tanks
Authors: Schillaci Eugenio , Amani Ahmad , Oliet Carles , Rigola Joaquim , Castro Jesus 
Published: June 2024

Abstract
Due to its high power density, the aviation sector is pushing towards its electrification by designing new propulsion systems based on cryogenic liquid hydrogen (LH2). From an engineering point of view, the efficient design of tanks constitutes one of the main challenges. They must guarantee efficient isolation of the hydrogen to avoid its evaporation and, at the same time, ensure reasonable weight and dimensions. Using numerical simulations is fundamental for studying heat transfer between the external environment and the liquid fuel. This work focuses on the simulation of multiphase liquid-gas flow to analyze the tank pressurization as a function of different external heat fluxes. A commercial CFD software is used to perform simulations. VOF simulations with the Lee mass transfer model are employed, and some critical numerical parameters are analyzed to provide information on the optimal values.
Enhancing thermal management in cylindrical Li-ion battery through PCM integration with variable contact area
Authors: Shrinet Ekta Singh , Kumar Lalit 
Published: June 2024

Abstract
Cylindrical Li-ion batteries are widely embraced in various sectors, notably electric vehicles and renewable energy storage systems. An effective thermal management system is vital for their safe and dependable operation, enhancing both the performance and reliability of the system. This study employs a distinctive hybrid cooling strategy consisting of a phase change material (PCM) at the centre of the battery and liquid cooling at the surface of the cylindrical batteries. The contact area between the coolant and the battery’s surfaces varies to make sure same heat transfers from each battery. This approach is instrumental in maintaining thermal uniformity and regulating the maximum temperature. In the numerical analysis, we employed ANSYS Fluent 2022 R1 to create the computational model encompassing the Li-ion battery, PCM, and liquid cooling system. This arrangement utilized eight 18650Li-ion batteries, with each battery housing a 2 mm radius PCM rod at the centre of the batteries. A heat-conducting element (HCE) was introduced to facilitate contact between the battery and the coolant channel. Water was selected as the coolant, and the coolant channel cross-sectional area is 65 × 2 mm2. The relationship governing the variable contact area is determined by fixing the velocity and the first battery contact area. The variable contact geometry maintains thermal uniformity throughout the battery module, resulting in a 74% enhancement in thermal uniformity. Nevertheless, the integration of PCM inside the battery effectively prevents individual batteries from surpassing specified temperature limits. It yields a remarkable 36.64% enhancement in thermal uniformity compared to situations in which PCM is not present, albeit with a 3.75% capacity loss. Furthermore, the study investigates the effects of coolant flow rates and performs an extensive analysis of temperature variation and melting fraction.
Thermal performance of a chaotic heat exchanger: an experimental study
Authors: Hani Nouhaila El , Lacassagne Tom , Hamidouche Souria , Bihan Loic Le , Bontemps André , Amir Bahrani S. 
Published: June 2024

Abstract
Improving the efficiency of heat exchangers requires innovative approaches that reconcile performance and sustainability. This study examines the potential of a curved geometry employing chaotic advection as a passive technique for improving internal heat transfer. The Chaotic Heat Exchanger (CHE) studied was constructed using 18 bends at 90 degree angles, and by simply turning each bend at a 90-degree angle to the previous one. The aim is to investigate the chaotic heat exchanger by focusing on heat transfer efficiency. A comparative analysis is carried out between the chaotic heat exchanger and a conventional Helical Heat Exchanger (HHE), using an experimental approach with water as the internal hot fluid. The Reynolds number examined ranges from 250 to 3500. It is found that the CHE outperforms the HHE both in terms of heating capacity and of inner Nusselt number, particularly in the intermediate Reynolds number range.
Numerical insights into turbulent penetrative convection over localized heat sources
Authors: Kenjereš S , Žilić A , Hanjalić K 
Published: June 2024

Abstract
The turbulent penetrative convection into a stable convective boundary layer represents an important phenomenon in environmental engineering and atmospheric science. In the present study, we present a series of numerical simulations performed by two modeling approaches: the high-fidelity Large-Eddy Simulations (LES), and the less computationally demanding transient Reynolds-Averaged Approach (TRANS), but with an advanced sub-scale turbulent heat flux model. By simulating different localized heat sources over the ground, and by performing a direct comparative assessment of results obtained by LES and TRANS, we confirmed an overall good agreement in predicting the time evolution of the horizontally averaged temperature profiles. Similarly, the morphology of instantaneous thermal plumes and large convective structures predicted by TRANS were in reasonable agreement with the referent LES predictions.
Unstructured Conservative Level-Set (UCLS) method for reactive mass transfer in bubble swarms at high density ratio
Authors: Balcázar-Arciniega N , Rigola J , Oliva A 
Published: June 2024

Abstract
This research presents a parallel Unstructured Conservative Level-Set (UCLS) method for reactive mass transfer in bubbles with a high-density ratio. This method uses the multiple-marker UCLS approach to circumvent the numerical coalescence of bubbles, combined with the finite-volume method to discretize transport equations on 3D collocated unstructured meshes. The fractional-step projection method solves the pressure-velocity coupling. The central difference scheme discretizes the diffusive term, whereas convective term within the momentum transport equation, level-set advection equations, and mass transfer equation are discretized by unstructured flux-limiters schemes. Such a combination of numerical techniques preserves the numerical stability in bubbly flows with a high Reynolds number and high-density ratio. Numerical and physical findings on the effect of physical properties ratios on the reactive mass transfer are reported, including their effect on the Reynolds number, interfacial area and Sherwood number.