bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multi-scale boiling heat transfer investigation on micro-thin aluminum heaters
Authors: Bucci M , Zupančič M , Golobič I 
Published: June 2024

Abstract
Nucleate boiling is a highly efficient heat transfer mode distinguished by the liquid-vapor phase change, which occurs through the formation, growth, and detachment of vapor bubbles from a heated surface. Its crucial role in various industrial applications, such as nuclear power plant operation and effective heat management in small electronic devices, has driven significant research efforts. However, despite extensive research dedicated to boiling investigations, there are still substantial knowledge gaps that hinder our ability to accurately predict heat removal rates. These knowledge gaps arise from the complex nature of small-scale boiling phenomena, which are further complicated by their strong dependence on operating conditions and the interactions between walls and fluids. In an effort to address some of these gaps, we conducted multi-scale investigations during pool boiling of de-ionized water on micro-thin aluminum heaters. We captured bubble dynamics through multiple synchronized diagnostic sources, including high-speed backlit imaging to track bubble growth, synchronized high-speed infrared thermometry to capture the corresponding thermal footprint on the boiling surface, and in-house developed fast-response micro-thermocouples to measure temperature at multiple locations within the fluid. Our study reveals peculiar aspects of heat transfer mechanisms occurring at single bubble level (low heat fluxes) and in fully developed nucleate boiling regimes (high heat fluxes).
Influence of subcooling conditions on pool boiling in microgravity conditions: Single artificial case
Authors: Ronshin F , Kabov O , Rednikov A , Tadrist L 
Published: June 2024

Abstract
A series of boiling experiments on a single artificial nucleation site has been carried out on the International Space Station (ISS) in the framework of the Multiscale Boiling (RUBI) setup installed in space in 2019. The aim of these unique experiments is to understand the bubble nucleation-growth mechanisms involved in heat transfer during boiling under well-controlled operating conditions without being masked/impeded by gravity and natural convection. The bubbles can grow to large sizes that are inaccessible in the presence of gravity. They are observed by a side-view black-and-white camera and by an infrared camera through a transparent heated substrate. In this paper, we present the results of a single-bubble pool-boiling experiment with an emphasis upon the role of the surrounding liquid subcooling, several values of which are investigated. The experimental results are complemented by numerical simulations using a previously developed model. However, the model is slightly modified to account in a simplest way for possible non-condensable residuals, without which we would have a hard time to explain certain observed behaviors.
Drag effect of steam flow on droplet removal during dropwise condensation at different surface inclinations
Authors: Abbatecola A , Tancon M , Bortolin S , Del Col D 
Published: June 2024

Abstract
Dropwise condensation is a quasi-cyclic process characterized by the nucleation, growth, and removal of discrete liquid droplets on a subcooled surface. The removal of condensate is a critical aspect, usually achieved by exploiting the gravity force, the drag force of vapor or the surface wettability gradient. This paper presents an experimental study of the vapor drag action on condensate removal, with focus on droplet’s departing radius (rmax
). Specifically, for the experimental campaign, vapor velocity was varied from 3 to 14 m s−1 considering three different surface inclinations: vertical, 45° inclined, and horizontal. The results showed that, as the velocity increases, the difference in departing radii among the three different configurations decreases and, consequently, the difference in heat transfer coefficients decreases too. In fact, at the highest vapor velocity (~14 m s−1), rmax
was almost equal for all the inclinations leading to similar heat transfer coefficients (~120 kW m−2 K−1). Interestingly, on a horizontal surface considering vapor velocity equal to 3 m s−1, despite the lack of gravity’s contribution to droplet removal, no transition to filmwise condensation was observed.
Grooved hybrid copper surfaces for condensation heat transfer.
Authors: Goswami Amit , Pillai Suresh C. , McGranaghan Gerard 
Published: June 2024

Abstract
Condensation is commonly utilized in numerous thermal management applications and has two modes termed filmwise and dropwise, the latter providing superior heat transfer performance. However dropwise condensation is usually limited by its dependence on gravitational shedding of condensate. To combat this, hybrid surfaces consisting of regions of different wettability have emerged as a promising solution. Of such designs, hybrid grooved surfaces consisting of grooves with varying wettability in the groove valleys and ridge tops are of current interest. To date, most such surfaces have been silicon-based and over flat substrates. In this work, condensation experiments are performed on a copper tube with fabricated grooved hybrid surfaces. The aim is to take advantage of anisotropic wetting due to the presence of grooves and condensate drainage from higher wettability regions. The experimental results quantify the heat transfer with the degree of subcooling. At the same time, droplet dynamics were studied on the hydrophobic-hydrophilic surfaces, showing several droplet growth and departure mechanisms leading to effective heat transfer.
Cryogenic quenching process enhancement through coating and microstructure optimization
Authors: Graffiedi Marco , Dent Francis J. , Khodaparast Sepideh , Bucci Matteo 
Published: June 2024

Abstract
In this work, we explore the impact of coatings and microstructures on heat transfer during a cryogenic quenching process. An easily reproducible quenching test is presented as a benchmark for testing different solutions. The study involves two different flat polymeric coatings as well as three porous microstructures. The results show that pairing a low-conductive coating with an appropriate porous surface microstructure on top of a stainless-steel plate can reduce the chill down time, accelerating the transition from room temperature to liquid nitrogen temperature, by a factor of five. High speed video recordings have been used to analyse the quenching process with different coatings and microstructures showing how the suppression of the film boiling regime is the key to enhancing the quenching process.
Spray cooling of micropillared steel plates: Two-stage quenching phenomenon
Authors: Kita Y , Matsunaga T , Ariyoshi T , Fukuda H , Takata Y , Kohno M 
Published: June 2024

Abstract
Spray cooling is a crucial process of steel manufacturing, nuclear power plants and electronics thermal management. However, its precise control is challenging due to the various boiling regimes involved at different temperature levels. Transition from film boiling to nucleate boiling, namely, the onset of quench is our particular interest as it remarks the thermal history of the hot object. Based on our previous findings that quench occurs at a specific temperature defined at the droplet-surface interface we demonstrate that micropillars on steel plates can increase the quench temperature Tq
. We performed water spray cooling tests with stainless-steel samples, on which various configurations of micropillars were fabricated using laser texturing. Interestingly, we observed two stages of quench for a specific sample: a drastic increase in the cooling rate at ca. 450 °C, followed by another increase at ca. 250 °C. The first cooling rate increase is attributed to the initiation of stable liquid-solid contact at the pillar tops. Eventually, water wets the entire pillars and the bottom surface, further increasing the cooling rate. Samples with higher pillars showed no film boiling regime in the experiment, implying higher quenching temperature (Tq
> 600 °C). We attribute the increased apparent Tq
to the narrow heat conduction path within the micropillar, resulting in a significant temperature drop at the tip which enhances liquid-solid contact.
Effect of hydrophobic coating on optimization of dropwise condensation of steam on hybrid surfaces
Authors: Suzzi Nicola , Croce Giulio 
Published: June 2024

Abstract
Dropwise condensation of pure vapor on hybrid surfaces, characterized by alternate hydrophobic-hydrophilic regions, is numerically investigated via phenomenological, Lagrangian modelization of dropwise condensation on hydrophobic regions. The drop size distribution over the hydrophobic domain, which knowledge is crucial for development of accurate simplified, statistically based models, is computed. Comparison with literature correlations shows that the theoretical correlation for size distribution of small droplets gives an inaccurate estimate, while the improved correlation, derived from the droplet population balance, better describes the numerical size distribution and, if incorporated in the statistically based model, allows to accurately predict the condensing flux.
Flow boiling heat transfer in a plate heat exchanger with mixed chevron angle plates
Authors: Yang Chien-Yuh , Hsieh Mu-Ting 
Published: June 2024

Abstract
This study designed a 120-plates PHE with combination of 60 plates with 65° chevron angle and 60 plates with 35° chevron angle. The plates with 65° chevron angle were assembled in the half part of the PHE which near the inlet port to provide higher flow resistance in comparing to the other 35° plates. The 35° chevron angle plates were put away from the inlet port to reduce the flow resistance caused by the longer flow path. It is aimed to reduce the flow maldistribution in the multiplate heat exchanger and improve its heat transfer performance. Refrigerant R-410A flow boiling heat transfer performance in the mixed angle PHE and another PHE with 65° chevron angle was tested for comparison. The test results show that heat transfer coefficient in the mixed chevron angle PHE is 20% to 70% higher than that in the 65° chevron angle PHE with 25% lower pressure drops. The mixed angle plates apparently reduced the liquid refrigerant flow deficient region and provided a better heat transfer performance.
Boiling of binary mixtures on superhydrophobic surfaces with artificial cavities
Authors: Zhang Ningxi , Orejon Daniel , Liu Jionghui , Sefiane Khellil 
Published: June 2024

Abstract
This study experimentally investigates bubble behaviour from an isolated artificial cavity on a superhydrophobic substrate, the working fluid is a binary mixture of Novec649 and Novec7000 with mole fractions between 0.05 – 99.5 as well as their pure counterparts. The results show an earlier onset of bubble departure as well as deceasing trends in bubble departure diameter in the presence of the binary mixture compared to pure cases. The bubble departure diameter is at its minimum and fastest growth rate at a mole fraction of approximately 0.50. Theoretical models from literature were tested and satisfactory agreement with different models were achieved depending on the concentration.
Development of physically based modelling of bubble behaviour for subcooled boiling applications
Authors: Cranmer J. , Giustini G. , Skillen A. , Tunstall R. 
Published: June 2024

Abstract
A methodology for the modelling of phase change phenomena in two-phase flow is presented, based on interface capturing simulation and the mechanistic modelling of interfacial heat and mass transfer. The volume of fluid approach is adopted, utilising a compressive scheme to maintain interface sharpness, allowing a continuum representation of mass and heat source terms to be used. The methodology is verified against analytical solutions for both evaporation and condensation phase change problems, demonstrating excellent agreement even in the case of a large phase density ratio and high rate of evaporation.
Prediction of heat transfer coefficient and pressure drop of flow boiling and condensation using machine learning
Authors: Galicia Edgar Santiago , Matamoros Andres Hernandez , Miyara Akio 
Published: June 2024

Abstract
Heat transfer coefficient and pressure drop are two critical parameters in diverse thermal engineering applications, and the prediction of these parameters plays a crucial role in the development of heat exchangers. Traditional methods are often reliant on empirical correlations based on limited refrigerants and experimental conditions. The present research explores the application of machine learning methods to predict the heat transfer coefficient and pressure drop of a wide range of pure and mixed refrigerants. The methodology involves the compilation of over 20, 000 experimental observations encompassing an extensive range of operating conditions, heat exchanger geometries, and refrigerants. A total of 27 machine learning algorithm models, such as regression tree, support vector machines, and deep neural networks, are trained on this diverse dataset to discern intricate patterns and dependencies. After dividing the dataset into 80% for training and the rest for validation, the machine learning prediction shows an ability to predict the heat transfer coefficient and the pressure drop with high accuracy in most of the refrigerants. Notably, the accuracy achieved by the machine learning models surpassed that of conventional correlations, highlighting their superior predictive capabilities. Furthermore, the accurate prediction of heat transfer enhancement methods added another layer of validation to the model’s effectiveness. It is noteworthy that the dataset employed in this study has been made publicly accessible online.
Advancements in laser-based spatiotemporal measurements of flow boiling
Authors: Chen Zengchao , Narayan Surya , Lobasov Aleksei S , Pervunin Konstantin S , Falsetti Chiara , Bucci Matteo , Markides Christos N 
Published: June 2024

Abstract
Recent advancements in laser and imaging systems, as well as in computational processing capabilities, have made quantitative optical imaging, which is often combined with laser illumination, highly adaptable, robust and reliable. Laser-based diagnostic techniques, such as planar laser-induced fluorescence (PLIF), offer the possibility of simultaneous spatiotemporally resolved measurements of temperature fields in the liquid phase at boiling conditions. In this paper, we examine the applicability of two-colour PLIF (2cPLIF), where the ratio between individual fluorescent emissions from uniformly dispersed dyes is used to take temperature measurements in the liquid phase in the presence of moving vapour-liquid interfaces typical of boiling flow. The implementation of 2cPLIF necessitates uniformity in the concentration of different dyes across the flow field. However, in the case of a multiphase flow such as boiling, thermophoresis can lead to inhomogeneous dye distributions. To overcome this challenge, a single-dye multispectral planar laser-induced fluorescence (SDMS-PLIF) method has been developed, which employs fluorescent emissions in different spectral bands of the same dye (Nile Red). The spectral characteristics of Nile Red were measured using a spectrometer to identify its temperature-sensitive bands over a wide range of dye concentrations, from 0.3 to 30 mg/L. Following this, we demonstrate the measurement capabilities of SDMS-PLIF thermography as applied to a boiling flow in a miniaturised vertical square channel, gaining insight into the thermohydrodynamic interactions between vapour bubbles and a heated wall.
Investigation of dropwise condensation of water through an efficient individual-based model
Authors: Tancon M , Abbatecola A , Mirafiori M , Bortolin S , Del Col D 
Published: June 2024

Abstract
In recent years, researchers have directed their studies towards solutions aimed at enhancing heat exchangers effectiveness. In this context, dropwise condensation (DWC) has been identified among the most promising solutions to increase the condensation heat transfer coefficient (HTC). In fact, DWC provides heat transfer coefficients up to ten times higher than those achievable during filmwise condensation (FWC), resulting in both economic and energy benefits. The DWC phenomenon is usually modelled by combining the heat exchanged through a single droplet and the drop-size distribution. The latter can be divided into a distribution of large droplets N(r), determinable analytically by semi-empirical models, and a distribution of small droplets n(r), typically determined through statistical approaches called population-based models. Another possibility for the determination of the droplet-size density is to simulate the DWC process by an individual-based model (IBM). In this case, each drop is tracked throughout its entire life cycle (nucleation, growth, coalescence, sliding), and the drop-size distribution is obtained as a result. In this paper, a new IBM for the simulation of DWC of steam is proposed. The developed model allows for the simulation of more than 10 million droplets while keeping an acceptable simulation time thanks to the implementation of parallel computing. The predictions obtained from the model, in terms of drop-size distribution and condensation heat flux, are compared against both PBM results and experimental data.
Experimental investigation of condensation heat transfer on vertically inclined grooved aluminium surfaces
Authors: Shatskiy Evgeny , Kumavat Parth S , O’Shaughnessy Seamus M 
Published: June 2024

Abstract
This study details the experimental investigation of surface condensation heat transfer on vertically inclined aluminium surfaces with simple modifications. A bespoke experimental apparatus was constructed to control the saturation conditions inside the condensation chamber where the test surface is located. The degree of subcooling of the test surface was precisely controlled by an external heat exchanger. The meter bar technique was used to evaluate the condensation heat flux. Using distilled water as the working fluid and a plane aluminium test surface as the baseline case, the experimental apparatus was validated by comparison of the determined heat transfer coefficient with Nusselt’s model of filmwise condensation on a vertical plane surface, where an excellent agreement was obtained. 7 different aluminium test surfaces were subsequently investigated, each one modified with grooves measuring 0.5mm by 0.5mm (height and width), with a consistent spacing of 0.5mm between them. Groove angles relative to the vertical axis of 0° (180°), 30°, 45°, 60°, 90°, 120°, and 150° were investigated, where grooves were symmetrically mirrored at the centre of each test surface. Results highlighted a significant influence of groove angle on the heat transfer coefficient, with the best-performing sample (150˚) producing a maximum enhancement of 45% and an average enhancement of 34% compared to the baseline test surface over the respective range of subcooling.
Meshfree RBF–FD methods for numerical simulation of PDE problems
Authors: Larsson Elisabeth , Mavrič Boštjan , Michael Andreas , Pooladi Fatemeh , Tominec Igor 
Published: June 2024

Abstract
The meshfree RBF–FD method is becoming an increasingly popular discretization method for challenging PDE problems due to its flexibility with respect to geometry and its ease of implementation. Using a combination of polyharmonic spline basis functions and polynomial basis functions has proven to be particularly successful with a convergence rate depending on the polynomial degree and good behavior at boundaries due to the contribution of the spline part. A challenge that has been observed is that derivative boundary conditions can give rise to large errors. A known remedy for this problem is to introduce one or more layers of ghost points, which improves the boundary approximations. In a recent paper, Tominec, Larsson, Heryudono (2021), it was shown that using oversampling is another effective way to handle this problem. Oversampling also allows for theoretical analysis of the method, which can then be viewed as a discretization of a continuous least-squares projection. By looking deeper into the error estimates we gain an understanding about how to best implement the method.
Enhancing fluid distribution in additively manufactured heat exchangers using autogenerated geometries
Authors: Kimmich J. 
Published: June 2024

Abstract
The heat exchanger distributor, which connects the tube carrying the medium to the heat transfer geometry, has received less attention in research studies compared to heat transfer geometries. However, the flow distribution is critical to efficiency. Therefore, a model-in-the-loop approach is presented to optimize additively manufactured distributors. A quasi-fractal distributor and all connected geometries, including pipe connections, heat transfer geometry and collector, are meshed and simulated in OpenFOAM using steady-state computational fluid dynamics. The volumetric flow rates determined from the simulation are assigned to the respective flow cross-sections during the distribution process. The flow cross-sections of the geometric model are modified within an optimization process, considering the prevailing volumetric flows. The results indicate a 64 % decrease in the standard deviation of volume flow across all 85 channels with a simple optimizer and few simulation loops. The printable geometry can be extracted directly out of Python using common file formats. The presented workflow has been proven feasible. Future improvements could involve using the automated model-in-the-loop simulation and creating optimizing algorithms considering fluid flow behavior.
Effect of the plates geometry on the performance of a cross-flow recuperator for indirect evaporative cooling systems
Authors: Caruana Roberta , Marocco Luca , De Antonellis Stefano , Guilizzoni Manfredo 
Published: June 2024

Abstract
In recent years, Indirect Evaporative Cooling (IEC) is becoming a very interesting technology, as it can guarantee a good cooling effectiveness with low energy demand, thus helping to face the issues of climate change. In this work, a Computational Fluid Dynamics (CFD) model has been used to evaluate the effects of the plates geometry on the performance of a recuperator for IEC systems with dry primary and secondary channels. The model was validated against experimental data for a cross-flow IEC system with dimpled plates, and the validation results were quite satisfactory. Therefore, five types of dimpled plates differing from the original one in shape and size of the dimples were investigated. The results showed that a good trade-off between the improvement of dry-bulb effectiveness and restrained pressure losses along the channels is obtained with dimples in the shape of right prisms with either triangular, or pentagonal, or circular base section, depending on the application.
Numerical study of solar evaporation in 3D-printed structures
Authors: Fillet R , Nicolas V , Celzard A , Fierro V 
Published: June 2024

Abstract
In this study, we used three-dimensional (3D) printed concave geometries filled with activated carbon to create a unique 3D solar evaporator for clean water production. The evaporation process was modeled considering airflow and solar radiation to investigate the advantages of 3D concave geometries. This work encompasses a series of studies, focusing on mass transfer inside the concavity and around the structure, to elucidate specific exchange points. Additionally, the research explores the effects of air velocity and the incorporation of additional holes within the structure, with the aim of improving evaporation.