bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assessment of local temperature elevation at the surface of tissue exposed to radiation of milimeter waves using simplified analytical approach
Authors: Poljak Dragan , Saric Josipa 
Published: June 2024

Abstract
Dominant effect of human exposure to electromagnetic fields in GHz frequency range corresponding to operation of 5G mobile communications systems is tissue heating i.e. local temperature elevation at the body surface, i.e. skin, ear and eyes. For the frequencies below transition frequency of 6GHz specific absorption rate (SAR) is used to quantify the volume heating. On the other hand, the surface heating above 6GHz is quantified via absorbed power density (Sab
). Once these quantities are determined by means of internal field dosimetry procedures it is possible to determine the local surface temperature increase by solving the bio-heat transfer equation. The present paper deals with the calculation of tissue surface heating due to exposure to millimeter waves. Internal dosimetry is based on the planar tissue model exposed to dipole antenna radiation. Electromagnetic model is based on the analytical solution of Pocklington integro-differential equation while the assessment of tissue surface heating in planar tissue model has been carried by analytically solving a simplified variant of the bio-heat transfer equation. Some illustrative results for power density and temperature elevations will be presented for different antenna parameters.
A needle-form 3-omega sensor for thermal characterization of cryopreserved biological tissues
Authors: Alliston Spencer P , Dames Christopher E 
Published: June 2024

Abstract
Thermal properties of cryopreserved tissues are critically important to the biopreservation community, which continues to seek more effective ways to store biological samples for improved outcomes in organ transplants as well as to facilitate the preservation of a record of biodiversity. Here, we present a reusable thermal needle-type 3-omega method designed for in situ characterization of such tissues, as well as other soft materials. The 3-omega method is a classic thermal materials characterization technique, which has been integrated into a modified microfabricated neural probe. This enables the measurement to be robust to environmental and experimental factors in cryopreservation. We demonstrate the viability of such a sensor to measure thermal conductivity for amorphous and crystalline solid samples of biological tissues, as demonstrated on 3mm thick chicken liver. These measurements can also be used for differentiation of solid samples, which is of particular interest for studies involving the kinetic limits of amorphous solidification (vitrification). In this, we demonstrate the value of a packaged thermal sensor to advancing the thermal understanding of cryopreserved biological systems and other solid-liquid phase change systems.
Thermal management system for cell-biology experimental setup studying calcium signalling in microgravity
Authors: Hochuli A , Wuest S L , Stamatiou A , Fenk B , Estermann P , Schiffmann D , Ammann S , Palacios A , Zumbühl C , Kummer R , Böhmer M 
Published: June 2024

Abstract
A novel hardware featuring specific LED arrays shall be developed to investigate free calcium in biological cells exposed to microgravity conditions. The temperature-sensitive samples require a precise and reliable temperature control system that can operate without electricity. In this paper, we assess the effectiveness of a passive temperature control system based on phase change material. Two extreme operation scenarios are investigated simulatively with the software COMSOL 6.1 for correct dimensioning and material selection. The simulation results of the first operation scenario show that the required temperature range for mammalian cells can be maintained during a power interruption of two hours. The simulation results of the second operation scenario show that excess heat generated by the LED arrays is effectively evacuated with a phase change material-based thermal management system. The physics software modules “heat transfer in solids and fluids” and “surface-to-surface radiation” were required to simulate illuminating LEDs adequately.
Multi-phase-field lattice Boltzmann simulations of semi-solid simple shear deformation in thin film
Authors: Yamanaka N , Sakane S , Takaki T 
Published: June 2024

Abstract
Semi-solid deformation during casting often results in significant solidification defects, such as segregation bands. Consequently, the development of a numerical simulation tool is crucial for accurately replicating semi-solid deformation. In our previous study, we applied a multi-phase-field lattice Boltzmann (MPF-LB) model to semi-solid deformation, facilitating seamless simulation from polycrystalline solidification to semi-solid deformation in a two-dimensional (2D) problem. This study extends the 2D MPF-LB model to a three-dimensional (3D) problem and develops a simulation method for semi-solid simple shear deformation in thin films. To enhance the efficiency of the 3D semi-solid simulation, we implemented parallel computations using multiple graphics processing units. Through a discussion of the relationships among the stress–strain curve, grain rearrangement behavior, and fluid flow, we confirmed that the developed 3D MPF-LB model successfully reproduced the characteristic phenomena of semi-solid deformation, and has high potential to investigate the nuanced mechanisms of semi-solid deformation.
Effects of the asymmetric and oscillating turbulent melt flow on the heat transfer and solidification inside the thin slab continuous casting (TSC) mold under the applied electromagnetic brake (EMBr)
Authors: Vakhrushev A , Karimi-Sibaki E , Wu M , Tang Y , Hackl G , Watzinger J , Bohacek J , Kharicha A 
Published: June 2024

Abstract
The thin slab casting (TSC) is a breakthrough near-net-shape technique for flat products accompanied by rapid casting and solidification rates. The TSC quality hinges on the turbulence, super-heat flow and growth of the solidified shell. The electromagnetic brake (EMBr) is commonly applied to control the fresh melt flow after feeding through a submerged entry nozzle (SEN). Numerical modelling is a perfect tool to investigate the multiphase phenomena in the continuous casting (CC). The presented study considers the heat transfer through the solid shell and water-cooled copper mold including the averaged thermal resistance of the slag skin and the air gap coupled with the turbulent flow and magnetohydrodynamics (MHD) model using an in-house code developed inside the open-source computational fluid dynamics (CFD) package OpenFOAM®. The model is applied to investigate different undesired asymmetric melt flow issues: (i) with the misaligned or (ii) partially blocked SEN; (iii) caused by the mean flow fluctuations with the natural frequencies; (iv) related to the oscillations of the fresh melt jets for the specific SEN designs and casting regimes. The variation of the flow pattern and superheat distribution is studied and presented for different scenarios both with and without applied EMBr.
Effect of Marangoni flow during the solidification of a Fe-0.82wt.%C steel alloy
Authors: Sari Ibrahim , Andreas Ludwig Menghuai Wu , Kharicha Abdellah 
Published: June 2024

Abstract
A two-phase Mixture model is proposed to simulate the liquid-solid phase transition of a Fe-0.82wt%C steel alloy under the effect of Marangoni flow. This model simplifies computations by solving a single momentum and enthalpy equation for the mixture phase using a three-dimensional finite volume method. The simulation involves solidifying a rectangular ingot (100 × 10 × 100 mm3) from the cold bottom surface towards the hot-free surface at the top. To facilitate heat exchange with the surrounding environment, a high heat transfer coefficient of h = 600 W/m2/K was applied on the bottom surface to establish an upward solidification direction. However, a lower heat transfer coefficient of 20 W/m2/K was applied on the top free surface, which was considered flat. This study aims to examine the effect of Marangoni flow generated by surface tension on flow and segregation patterns. The results show that the Marangoni flow emerges at the free surface and penetrates into the liquid depth, leading to the formation of hexagonal patterns along the liquid thickness. Upon full solidification, macro-segregation also exhibits hexagonal structures, mirroring the stationary hexagonal shapes generated by Marangoni flow.
A new hybrid local radial basis function collocation method for 2.5D thermo-mechanical modelling of continuous casting of steel
Authors: Vuga Gašper , Dobravec Tadej , Mavrič Boštjan , Šarler Božidar 
Published: June 2024

Abstract
This study presents a new strong-form meshless method to solve the thermo-mechanical problem of the solidification process in the continuous casting of steel. A two-dimensional slice that travels in the casting direction is modelled in the Lagrangian system. The newly developed mechanical model is one-way coupled to the thermal model, where the heat flux due to the mould, sprays, rolls and radiation are imposed to solve heat transfer in the strand. The resulting temperature and metallostatic pressure govern the Norton-Hoff visco-plastic model used for computing shrinkage of the solid shell and induced residual stresses. The results are used to estimate critical areas susceptible to hot-tearing formation. The mechanical model uses a generalised plane strain assumption that includes linear strains perpendicular to the slice and enables the computation of the straightening of the strand. The thermo-mechanical model is spatially discretised with a local radial basis function collocation method (LRBFCM). The mechanical part includes a new hybrid method that combines LRBFCM with finite differences for increased stability. The presented work shows how the developed model is used to assess the impact of casting velocity on the solid shell shrinkage and the probability of hot-tearing occurrence in the continuous casting of square billets.
Fast thermodynamic simulation of electrical control cabinets via thermal resistor networks
Authors: Haag D , Stergiaropoulos K 
Published: June 2024

Abstract
A fine-grid Computational Fluid Dynamics (CFD) simulation without thermo-electric coupling provides an accurate prediction of temperatures inside low-voltage control cabinets. But due to its high computational demand and complexity, the approach is not eligible for a widespread use in pre-production design. This study presents a lightweight and robust model based on the thermal-electrical analogy and Kirchhoff’s current law. The thermal resistor network is created for each control cabinet individually. An isothermal coarse-grid CFD simulation is used to approximate flow resistances. Convective resistances are calculated with Nusselt number correlations. The approach was tested on 120 randomly generated 2D control cabinet configurations. Component temperature errors were evaluated based on a normal distribution approximation. For moderate temperature rises up to 20 K the model had a mean error of 0.38 K and a standard error of 1.51 K compared to the reference fine-grid CFD model and was up to 12.8 times faster.
Optimization of Switching Algorithms for a Thermal Switch-PCM-Switch Stack in a Building Wall for Energy Savings
Authors: Chen Sarah M , Kaur Sumanjeet , Dames Christopher E 
Published: June 2024

Abstract
Thermally switchable building envelopes can provide energy savings compared to their traditional static counterparts. For example, in the summertime cooling season the envelope can switch into a thermally conductive state at night to exploit the free cooling of the nighttime air, while switching back into a highly insulating state during the warm daytime. Further benefits can be realized by incorporating phase change materials (PCMs) into the same building envelope between two thermal switches, because the PCM can store that nighttime cooling for later use during the day. Here we use analytical and numerical modelling to investigate the advantages of a switch-PCM-switch building envelope and specifically look to optimize the switching algorithms for the two switches. We frame the problem using dimensionless groups in order to identify the key parameter groupings that determine the response. We then build a lightweight lumped element model with runtime speeds of <0.5 seconds per scenario, which enables a brute force search of over 300,000 potential switching algorithms to identify the one with the highest total and net energy savings. We compare the results of the brute force approach with an algorithm that was proposed previously based on physical intuition [1]. We then conduct a similar brute force investigation of switching algorithms optimizing for average daily cost of energy, focusing on scenarios where time-of-day energy pricing is important. Using the resulting optimal switching algorithms, we present cost and energy savings for several real cities based on their realistic temperature data and time-of-day pricing.
Thermal management of high-powered short-duration electronics aided by a phase change material thermal energy storage
Authors: Martheleur D , Groulx D 
Published: June 2024

Abstract
Quantifying the performance of phase change materials (PCMs) for thermal energy storage in high-power short-duration electronics applications requires performing tests that push the material to its limit. This involves designing experiments to test solid-liquid PCMs in near real-world thermal load conditions to test its performance. Conventional cooling methods are sized to manage the maximum loading the cooling system will be subjected to in its operation, even if this loading occurs for a short period of time. This design ethos is inefficient and results in heavy and expensive equipment being used in an application where it will be underutilized most of its useful life. In this work, a PCM thermal energy storage (TES) device was built using a plate-and-frame heat exchanger and investigated to determine the suitability of this system to manage the temperature of high-power electronics with a low duty cycle. These experiments showed how a PCM-TES can be used in conjunction with conventional temperature management equipment to create a reliable cooling solution while allowing the conventional cooling components to be decreased in size and capacity. This work shows that, for a given application, a cooling system can be more efficiently designed with the use of a PCM-TES and opens the door to additional research on this topic.
Limitations of the enthalpy-porosity method for numerical simulation of close-contact melting on inclined surfaces
Authors: Van Riet V , Shockner T , Beyne W , Ziskind G , De Paepe M , Degroote J 
Published: June 2024

Abstract
One of the main challenges for latent thermal energy storage (LTES) systems is low heat transfer rates due to the low thermal conductivity of most phase change materials (PCM). Close-contact melting (CCM) can accelerate melting times in LTES systems but the current numerical techniques for solid liquid phase change have difficulties with accurately predicting this process. In this study, close-contact melting of PCM on an inclined surface is simulated using the enthalpy-porosity method in ANSYS Fluent. All PCM properties, including density, are temperature-dependent. In this way, phenomena such as natural convection, volume change and buoyancy between the solid and liquid are taken into account. The volume change is compensated by a gaseous expansion volume. Both 2D and 3D simulations are used to show discrepancy between state-of-the-art enthalpy porosity modelling and experimentally observed phenomena in the case of CCM. The mushy zone constant, which is set to 105 to allow motion of the solid bulk, causes the solid phase to deform as a highly viscous fluid instead of moving as a rigid body. The velocity differences inside the solid are more than 50 % of its sinking velocity. As a result, the movement of the solid resembles creep behaviour and the obtained CCM patterns are not physically accurate. Furthermore, the density difference between the solid and liquid phases causes an avalanching effect in the mushy zone, which artificially strengthens convection. In conclusion, the enthalpy porosity method exhibits significant limitations in accurately capturing close-contact melting phenomena.
Experimental validation of a design model for latent thermal energy storage extended with sensible heat
Authors: Beyne Wim , Degroote Joris , De Paepe Michel 
Published: June 2024

Abstract
Latent thermal energy storage can be a key technology for a green energy transition by matching fluctuating heat demand and supply. In order to implement a storage system, it needs to be designed which requires estimating the outlet temperature of a system for a given geometry and time history of the heat transfer fluid’s mass flow rate and inlet temperature. Currently, design methods are either overly simplistic, focusing solely on e.g. the phase change time or requiring the solution of partial differential equations which can be computationally expensive. The present paper proposes a novel approach where a latent thermal energy storage system is decomposed into a heat transfer fluid vessel, a sensible storage system and a storage system with only latent heat. Computationally inexpensive models are available for all three of these sub heat exchangers. A heat exchanger model is obtained by connecting the sub heat exchangers in parallel. This novel approach is used to model an industrial scale shell and tube latent thermal energy storage heat exchanger. The predicted outlet temperature is compared to the measured outlet temperature and the design model obtains good agreement.
1D modelling of a latent heat thermal energy storage prototype using boiling water as heat transfer fluid
Authors: Col Amandine Da , Bentivoglio Fabrice , Stutz Benoit 
Published: June 2024

Abstract
This paper presents a numerical model to simulate the thermohydraulic behaviour of a shell-and-tubes Latent Heat Thermal Energy Storage (LHTES) during discharging period, involving a boiling heat transfer fluid (HTF). It is based on a 1D homogeneous approach for the HTF (water) and a 1.5D approach for the phase-change material (sodium nitrate) allowing calculation times significantly shorter than those of CFD. This approach has been validated with experimental data in a previous study for a LHTES with a monophasic HTF. The two highlights of this paper are as follows: On the one hand, computational fluid dynamics has been used to develop equivalent homogeneous materials for PCM side, integrating the thermal properties of the phase-change material and the helical and longitudinal fins present in the LHTES. On the other hand, the model uses the asymptotic correlation of Steiner and Taborek to describe boiling heat transfers and usual correlations for single phase heat transfers. The paper focuses on the validation of the model against experimental data from the InPower project. The prototype is a 340 kWh storage that has been tested under different conditions. The model reproduces the total energy retrieved during a system discharge with relative error of 8.5% and an absolute mean error of 8.23 kW on outlet power. The main weakness of the model is the homogeneous model for the HTF that generates error in water level and local temperatures.
Melting of a phase change material in a rectangular cavity in the presence of metallic fins
Authors: Naldi C , Martino G , Dongellini M , Biserni C , Morini G L , Lorente S 
Published: June 2024

Abstract
The melting of the phase change material (PCM) octadecane, confined in a rectangular cavity heated from the bottom, is numerically studied. Simulations are performed through finite element software in order to analyze the impact of metal fins within the enclosure on the melting time. The results are analyzed in terms of the time-dependent position of the melting front, time-dependent average liquid fraction, and time needed for the PCM melting. The obtained outcomes highlight how, with a low number of metallic fins, the initial melting regime dominated by conduction at a certain time gives way to a convective melting regime characterized by Rayleigh–Bénard cells, in full agreement with the results of the theoretical analysis. On the contrary, with a high number of metallic fins, conduction is the only mechanism that governs heat transfer and the rapid melting slows down when the phase change front reaches the top of the fins. More specifically, the addition of the fins within the cavity yields a reduction in the time needed for the complete PCM melting up to 90% in the analyzed cases. The reported results provide new insights regarding the heat transfer mechanisms involved in PCMs melting within bottom-heated enclosures.
Study of the phase change processes of encapsulated phase change material for solar thermal energy storage in domestic hot water production
Authors: Bianqui C , Viedma A , Egea A , García A 
Published: June 2024

Abstract
This study aims to examine the melting processes of encapsulated PCM in a cylindrical-shaped capsule, made of stainless steel. It has a diameter of 60 mm and a height of 20 mm. The chosen PCM is the paraffin RT35HC, which has a melting point around 35 ºC. Experiments are conducted in a water-filled thermal bath, placing the capsule vertically and heating the water using a thermostat. Temperature field analysis of the PCM is performed using thermocouples, and simultaneously, the inside of the encapsulated material is observed through a transparent wall. It has been proven that the sensors are capable of detecting the gradual evolution of the liquid phase of the PCM and its accumulation at the top of the capsule due to its lower density.
Experimental thermal analysis of an innovative heat sink coupled to a nanoemulsion
Authors: Righetti G , Burgos J , Hernández L , Mondragón R , Barison S , Agresti F , Biasetto L , Mancin S 
Published: June 2024

Abstract
This work presents some new experimental measurements collected on a very innovative system proposed for electronic cooling. This setup combines a classical heat sink with a latent thermal storage. The storage material is a phase change nanoemulsion made of water and 5 wt% of a commercial RT40HC paraffin wax with 1-octadecanol as nucleating agent (weight fraction 1:10 with respect to PCM), while the heat sink is made of copper via 3D printing. The integration between the two components does not interfere with the external air convective heat transfer, as the emulsion is embedded inside the heat sink, which has an internal cavity. The tests analyse the temperature of the component and the emulsion in different locations during the charging and discharging phases at several heat fluxes.