bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal management of multi-chip electronic module with wavy fin heat sink-assisted immersion cooling
Authors: Suresh Pratheek , Vasista Kasavajhula Naga , Kushwaha Shailesh , Balaji Chakravarthy 
Published: June 2024

Abstract
Single-phase immersion cooling technology has emerged as a promising solution to effectively manage the thermal needs of electronics in modern high-heat-flux-density data centres. This approach involves submerging electronic components, such as heat-generating chips, into a thermally conductive dielectric liquid. The present study investigates the thermal performance of a multichip server module under single-phase immersion cooling using NOVEC 7500 (C
9
H
5
F
15
O) as dielectric flow media. A wavy fin heat sink design with varying number of fins on each heat sink is proposed to overcome the poor thermal performance of the dielectric fluid. Initially, an optimal plane fin combination is determined; it reduced the maximum temperature (Tmax
) and Root Mean Square Error of all chips by 22.4 and 7.7 0
C compared to the alternative combinations. Following this, the effect of amplitude (A) and wavelength (λ) of the wavy fin surface for the optimal fin combination from the initial result is studied. Average temperature (Tavg
) monotonically reduces with A and increases with an increase in λ. Due to the implementation of a wavy fin surface, Tavg
and Tmax
were further reduced by 3.9 and 5.3 0
C, respectively. The outcomes of the present study offer valuable insights into improving the thermal performance of single-phase immersion cooling systems and mitigating the thermal shadowing effect.
Experimental investigation of the cooling performance of an additively manufactured prototype for nuclear fusion energy application
Authors: Favero G , Bonesso M , Dima R , Doretti L , Pepato A , Righetti G , Zilio C , Mancin S 
Published: June 2024

Abstract
Metal Additive Manufacturing (MAM) is a non-traditional technology recently introduced to manufacture multifunctional mechanical components. In fact, recent developments in Laser Powder Bed Fusion (LPBF) process have enabled the production of materials characterized by high density and high thermal conductivity properties, such as copper alloys and pure copper, making the technology attractive for thermal science. In nuclear fusion energy applications, mechanical components often encounter extremely high heat fluxes. An innovative solution using unconventional integrated cooling channels is therefore required to safely manage the components. However, the high surface roughness in 3D-printed parts represents an intrinsic limitation of the LPBF technology: the cooling channels show high-pressure drops due to the high viscous dissipation generated by the rough surface. To address this challenge, a lab-scale prototype of an e-beam extraction grid for a fusion experiment with an original integrated cooling system was designed and manufactured. Additionally, a novel heating mask was designed and manufactured to reproduce the realistic heat load distribution on the grid during the experimental tests. The prototype was built using additive manufacturing with a CuCrZr copper alloy. The grid underwent heat treatment via solution annealing and age hardening, to increase thermal conductivity from about 100 W m−1 K−1 to almost 300 W m−1 K−1. The prototype was tested at three different constant heat fluxes by varying the water flow rate while measuring the pressure and the maximum temperatures of the grid. A CFD numerical model was also calibrated to estimate the thermo-hydraulic performance of the prototype under test conditions. The experimental and numerical results are presented in terms of overall thermal performance, maximum temperature, and pressure drop.
Measurement of effective thermal conductivity of composite powders of 2D materials and metals for additive manufacturing
Authors: Lee Hyunjong , Koutsioukis Apostolos , Jafari Davoud , Geurts Bernard J. , Wits Wessel W. 
Published: June 2024

Abstract
Laser Powder Bed Fusion (LPBF), a promising additive manufacturing technique for composites of 2D materials and metals, requires knowledge of thermophysical properties, such as the thermal conductivity of powder, for process optimization. In this study, we measured the effective thermal conductivity of the most representative Cu-graphene composite powder in the field of heat transfer applications. To measure thermal conductivity, we propose a differential scanning calorimetry (DSC) method to measure the thermal resistances of a powder bed under steady-state heat flow conditions. We observe that the thermal conductivity of a composite powder is 1,000 times lower than that of the bulk metal without 2D material addition; e.g., exhibiting ~ 0.30 W/mK in Cu-1wt.% graphene powder. Furthermore, we discuss powder size and morphology impact on thermal conductivity influencing the number of contact points and thermal contact resistance. Our findings contribute to understanding the thermal conductivity of composite powders in a powder bed and aid in optimizing LPBF processes.
Determination of transient heat transfer by cooling channel in high-pressure die casting using inverse method
Authors: Bohacek J , Mraz K , Hvozda J , Lang F , Raudensky M , Vakhrushev A , Karimi-Sibaki E , Kharicha A 
Published: June 2024

Abstract
Complex shapes of aluminum castings are typically manufactured during the short cycle process known as the high-pressure die casting (HPDC). High productivity is ensured by introducing die cooling through a system of channels, die inserts or jet coolers. Die cooling can also effectively help in reducing internal porosity in cast components. Accurate simulations based on sophisticated numerical models require accurate input data such as material properties, initial and boundary conditions. Although the heat is dominantly dissipated through die cooling, indicating the importance of knowing precise thermal boundary conditions, open literature lacks a detailed information about the spatial distribution of heat transfer coefficient. This study presents an inverse method to determine accurate heat transfer coefficients of a die insert based on temperature measurements in multiple points by 0.5 mm K-type thermocouples and a subsequent solution of the two-dimensional inverse heat conduction problem. The solver was built in the open-source CFD code OpenFOAM and the free library for nonlinear optimization NLopt. The results are presented for the commonly used 10 mm die insert with a hemispherical tip and coolant flow rates ranging from 100 l/h to 200 l/h. Heat transfer coefficients reach values well above 50 kW/m2K in the hemispherical tip, which is followed by a secondary peak and then a gradual drop to values around 1 kW/m2K further downstream.
On the conditions for the occurrence of crystal avalanches during alloy solidification
Authors: Shayesteh G , Ludwig A , Stefan-Kharicha M , Wu M , Kharicha A 
Published: June 2024

Abstract
Experimental studies on the solidification of ammonium-chloride-water alloys in relatively large containments reveal conditions that lead to the formation of numerous crystal avalanches. Columnar segments that occasionally slide downwards along a vertical mushy zone further fragmentate and so crystal multiplication occurs. As a condition for this phenomenon solidification-induced solutal buoyancy that leads to a rising interdendritic flow was identified for the present case. The interaction with sedimentation-induced downward flow ahead of a vertical columnar region results in a redirection of the interdendritic flow and thus, to local conditions that slow down further solidification or even lead to remelting. Gravity is then pulling loose segments downwards. In larger containment, the flow in the bulk melt is generally unsteady and even turbulent. Thus, the outlined flow-solidification/melting interplay happens frequently at numerous positions but in a stochastic manner.
Thermal control circuit modelling with TCCbuilder
Authors: Vozel Katja , Klinar Katja , Petelin Nada , Kitanovski Andrej 
Published: June 2024

Abstract
Thermal control elements (TCEs) and thermal control circuits (TCCs) are a promising addition to conventional methods of thermal management, as they enable non-linear, switchable, and active control of heat. However, TCEs and TCCs are still at an early stage of development and are not yet ready for use in commercial applications. The combinations of TCEs in TCCs and the transient operation of TCEs and TCCs have not yet been sufficiently investigated. We have developed an open-source TCC simulation tool with a user-friendly graphical user interface (GUI), TCCbuilder. TCCbuilder enables the design of TCEs and TCCs and offers the possibility to analyse their behaviour in (quasi-)steady state and transient operation. The tool has an extensive library of materials and TCEs (thermal switches, thermal diodes, etc.) compiled from extensive literature research and contributions from fellow researchers. TCCbuilder’s library of materials provides input data (e.g. temperature- and/or external field-dependent thermal properties) for simulations. However, users can also enter their own data. This article demonstrates the simple design and simulation of a TCC with a caloric device using TCCbuilder.
Oscillating thermal switch using electrostatic forces
Authors: Petelin N , Pečar B , Vrtačnik D , Perne J , Tomc U , Kitanovski A 
Published: June 2024

Abstract
Thermal control devices such as thermal switches, thermal diodes, thermal regulators and thermal capacitors can control the intensity and direction of heat flow, which has proven useful in various thermal management applications. Their operation is analogous to that of their electrical counterparts, where temperature differences correspond to voltage differences and heat flow corresponds to electric current. Here we design and fabricate a thermal switch that controls the heat flow from the heat source by changing the thermal conductance when switching ON and OFF. The thermal switch uses electrostatic forces for actuation and makes thermal contact between the heat source and the heat sink when in the ON state, and breaks contact when in the OFF state. The thermal switch is constructed using the commercially available materials. The heat sink and heat source are made of silicon, and the active part of the heat switch is a flexible gadolinium sheet with a thickness of 161 µm. The proof-of-concept device was evaluated for a magnetocaloric application; however, the proposed thermal switch can be used in any thermal circuit for fast thermal regulation and advanced thermal control.
Thermal control of thin films with nano structure
Authors: Sato M , Takahara Y , Matsumoto M , Kajinami N , Hanaoka M , Iwakawa M 
Published: June 2024

Abstract
Thermoelectric energy conversions have been attracting much attention, which directly generate electric energy from thermal one by utilizing the Seebeck effect. Among various efforts to improve the conversion efficiency, control of phonon propagation with nano-scale structures has been popular, which utilize phonon scatterings on structural interfaces. The concept is based on the difference of mean free path (MFP) between phonons and electrons (charge carriers). In typical cases with silicon-base devices, MFP of phonons is in an order of 100 nm while that of electrons is 1-10 nm. Thus structures of 10-100 nm size are expected to be effective for suppressing the phonon heat transfer without much reducing the electric transport, leading to conversion efficiency improvement. We have developed a numerical scheme to investigate phonon transport based on the Boltzmann transport equation (BTE) for time development of the phonon distribution function. To treat various shapes of nano-scale structures, we have newly introduced a VOF (volume of fluid) like scheme. In the presentation, we will show results of several test systems of nano-structured Si thin films, with evaluation of effective electric conductivity, to discuss how much nano-scale structures improve the conversion efficiency.
Thermal control devices and thermal circuits
Authors: Klinar Katja , Kitanovski Andrej 
Published: June 2024

AbstractIt is becoming evident that conventional thermal management methods like conventional thermal insulation and conventional thermal storage cannot meet the thermal control requirements of advanced, especially small systems with higher power densities or potentially transient, fluctuating, or migrating hot or cold spots, and for temperature-sensitive devices. This challenge is most evident in electronic components that experience degradation and loss of efficiency without constant and effective heat dissipation. To overcome these limitations, thermal control devices have emerged in various areas of thermal management. These small-scale devices provide non-linear, switchable, and active control of heat, similar to the way their electrical counterparts regulate electric current. Among others, notable thermal control devices include thermal conduits (which act as solid-state heat routers), thermal resistors (which provide thermal insulation), thermal switches (which actively control heat transfer through on-off states), and thermal diodes (which rectify heat currents). In this paper, we provide state of the art on the research activities and applications of thermal control devices.
Advancing thermochemical storage: synthesis and characterization of cement-based composite materials
Authors: Mondello A , Morciano M , Lavagna L , Pavese M , Chiavazzo E 
Published: June 2024

Abstract
Thermal Energy Storage (TES) is crucial for sustainability of the energy sector, yet the development of cost-effective, robust materials remains a significant challenge. This study aims at exploring the synthesis and thermal characterization of cement-based composites for seasonal thermochemical energy storage, with the goal to harness the high energy density of hygroscopic salts while mitigating their limitations. We investigate composites with several cement matrices to improve salt-cement compatibility. Furthermore, we investigate the possible incorporation of porous low-cost compounds to enhance porosity and improve economic aspects. As far as the characterization aspects are concerned, we show experimental adsorption isotherms at different temperatures to estimate key material properties like isosteric heat and water uptake, along with the relevant figures of merit such as energy density. Our research leverages on adjustable porosity and affordability of cement as a host matrix for the ‘active phase’. We studied two synthesis approaches: traditional dry impregnation and an in-situ technique suitable for cements. The in-situ method, being straightforward and reproducible, permits greater control over salt content. Preliminary cost analysis positions these composites competitively in the market. Although we are still at sub-optimal stage, potential cost reduction of some less popular cement matrices suggests an opportunity for improvement.
Optimizing MOF properties for seasonal heat storage: a machine learning approach
Authors: Trezza G , Bergamasco L , Fasano M , Chiavazzo E 
Published: June 2024

Abstract
In the quest to enhance thermochemical energy storage using promising sorbents, this work presents a study on the optimization of Metal Organic Frameworks (MOFs) properties for gas sorption, with a focus on CO2 and H2O adsorption. Through the analysis of crystallographic descriptors, the study aims to streamline the selection of MOFs that could potentially exceed the performance of existing water sorbent pairs. A comprehensive comparison of sequential learning (SL) algorithms reveals a method for identifying the minimal set of descriptors that influence adsorption properties of MOFs. The protocol involves constructing and training machine learning (ML) models to determine the number of influential descriptors and utilizing SHAP analysis to evaluate their importance. Findings suggest that including only these critical descriptors in the exploration space reduces computational load. Notably, the COMBO and the FUELS algorithms consistently outshine random guessing, validating their efficacy in materials optimization. The challenge of accessing full adsorption properties across the entire coverage range is addressed by a computational screening procedure requiring minimal input data. This method suggests that some vanadium based MOFs, originally designed for different purposes, could surpass the current leading compounds for thermal energy storage, primarily due to their optimal Henry coefficient values for water adsorption.
Enhanced latent thermal energy battery with additive manufacturing
Authors: Morciano Matteo , Alberghini Matteo , Fasano Matteo , Almiento Mariella , Calignano Flaviana , Manfredi Diego , Asinari Pietro , Chiavazzo Eliodoro 
Published: June 2024

Abstract
The low thermal conductivity of Phase Change Materials (PCMs), such as paraffin waxes, hinders efficient latent heat storage, especially for rapid charging and discharging cycles. To address this issue, this study explores experimentally and numerically the use of metal additive manufacturing to create a latent heat storage system operating at medium temperatures (around 90°C). A 3D Cartesian metal lattice is manufactured through laser powder bed fusion to optimize heat conduction within the PCM. Experimental tests show impressive specific power densities (approximately 714 ± 17 W kg−1 during charging and 1310 ± 48 W kg−1 during discharging). Moreover, the device exhibits stability over multiple cycles. Finally, the validated finite-element model has the potential to provides a basis for general design guidelines to boost the system’s performance further. Potential applications of this technology are highlighted in the automotive industry, where such systems could efficiently manage thermal energy, for instance, by capturing excess heat from an engine’s cooling radiator to expedite the warm-up process during a cold start, which is a critical phase for reducing pollutant emissions.
Numerical study on hybrid battery thermal management system integrating water, phase change material, and fins, under New European Driving Cycle
Authors: Thakur Satyam Singh , Kumar Lalit 
Published: June 2024

Abstract
This study introduced a hybrid thermal management system for a 4×4 cylindrical lithium-ion battery module, simulating New European Driving Cycle (NEDC) conditions. The system integrated water, phase change material (PCM), and fins for enhanced heat dissipation. The batteries, attached to an aluminium shell, incorporated PCM and a central coolant path. Fins were introduced between the coolant channel and Al shell to enhance heat transfer between batteries, PCM, and water. Comparative analysis against passive (PCM only) and active (liquid) cooling systems revealed the hybrid system’s superior performance. With a water flow rate of 2×10−8 m3/s, the system consistently kept temperatures below 50°C during charge-discharge cycles. Compared to active cooling, it achieved a significant temperature reduction of 18.47% and 5.01% after the charge and discharge processes. An intermittent cooling strategy further demonstrated its effectiveness in preventing thermal runaway (> 60°C) compared to the active cooling system. The proposed hybrid system demonstrated efficient thermal performance with low pumping power, suggesting its potential for multiple charge/discharge cycles.
CFD simulation of solid/liquid phase change in commercial PCMs using the slPCMlib library
Authors: Buruzs Adam , Giordano Fabrizia , Schieder Manuel , Reichl Christoph , Goderis Maité , Beyne Wim , De Paepe Michel , Barz Tilman 
Published: June 2024

Abstract
Modelling the solidification and melting behavior of phase change materials (PCMs) can present several challenges, including non-isothermal phase change, multi-step transitions, complex enthalpy-temperature relations and convective heat transfer. To tackle these challenges, this study proposes a novel numerical method based on real experimental data for modelling complex phase change behavior of commercial PCMs in Ansys Fluent CFD software. The phase transition of PCMs is simulated with the apparent heat capacity (AHC) method, which is implemented as a User-Defined Function (UDF). Heat convection is simulated with the Boussinesq approximation. The method is validated by comparing to the Ansys Fluent built-in Solidification and Melting (S&M) model for the case of piecewise constant heat capacity. The results show that AHC method provides excellent agreement with S&M model for a piecewise constant heat capacity model. In addition, the AHC method solves convergence problems even for narrow phase change temperature ranges when a smooth heat capacity function is assumed. Finally, the AHC model is also tested on a set of commercial PCMs exhibiting complex phase change behavior. Temperature dependent specific heat capacities are determined from heat capacity data provided by PCM manufacturing companies and are imported as cubic Hermite spline functions from the solid-liquid phase change material library slPCMlib available at https://slpcmlib.ait.ac.at/. From the presented case study and tested PCMs it can be concluded that the AHC method is numerically robust when used with sufficiently smooth heat capacity functions, and it can be recommended for the analysis of heat transfer with PCMs showing a complex phase change behavior.
Numerical modelling of thermal hysteresis in melting and solidification of phase change materials
Authors: Goderis Maité , Buruzs Adam , Giordano Fabrizia , Barz Tilman , Beyne Wim , De Paepe Michel 
Published: June 2024

Abstract
This research focuses on exploring the impact of thermal hysteresis effects on the performance of Phase Change Materials (PCMs) used in thermal storage or buffering applications. Computational Fluid Dynamics modeling in ANSYS Fluent is employed to investigate thermal hysteresis phenomena during solid-liquid phase change. The traditional enthalpy-porosity method is extended by introducing an alternative relationship between the liquid fraction and PCM temperature, implemented in Fluent through User Defined Functions. The study demonstrates the developed model by simulating a rectangular PCM enclosure with a heated wall featuring a time-dependent temperature boundary condition. Considering convective heat transfer, a comparison is made between the newly developed hysteresis model and the default solidification-melting model of ANSYS Fluent. The new model facilitates numerical analysis of thermal hysteresis during partial and complete melting and solidification processes, enabling the study of hysteresis effects on the part-load operation of PCM systems.
Characterization of hydration levels of salt hydrate using X-ray computed tomography
Authors: Fenk Benjamin , Stamatiou Anastasia , Guarda Dario , Martinez-Garcia Jorge , Schütz Philipp , Gwerder Damian , O’Neill Poppy , Ravotti Rebecca , Mancin Simone , Fischer Ludger , Worlitschek Jörg 
Published: June 2024

Abstract
Salt hydrates are promising phase change materials (PCMs) for energy storage due to their high enthalpy of fusion and cost-effectiveness. However, they face challenges like segregation. X-ray computed tomography (XCT) is suggested for non-destructive analysis to assess the formation of segregation. But first, the feasibility of using XCT to distinguish between different hydration levels of salt hydrates needs to be investigated. This study compares XCT gray values of anhydrous and salt hydrate samples, particularly sodium acetate (SA) hydrates, to understand the influence of hydration level on XCT images, aiming to assess XCT’s suitability for salt hydrate investigation.