bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of the operating characteristic of a demand-controlled 368 m deep CO2 thermosyphon geothermal borehole heat exchanger for building heating
Authors: Hagedorn Janina , Kahlfeld Robin , Nageler Malte , Kabelac Stephan 
Published: June 2024

Abstract
This paper examines a 368 m deep geothermal probe for heating an existing building. The geothermal probe based on the thermosyphon principle works with CO2. The working fluid evaporates and condenses in the probe so that no pump is required for transportation. The geothermal probe has an output of up to 22 kW at an underground temperature of up to 18°C. The demand-controlled use of the geothermal probe was investigated and the installed heat pump was optimized for its use. The average COP of the last heating season was between 2,3 and 4,6. For the second heating season the temperature of the soil around the probe is also measured via a distributed temperature sensing system, that covers the whole depth of the probe. It has been shown that the ground temperature only cools down to a certain point and does not fall below this point after a short regeneration period. It was shown that the heat pump with geothermal probe operates at constant temperatures at the evaporator compared to air heat pumps, even at cold outside temperatures.
Effect of water injector location on combustion and performance of an HCCI engine - A CFD analysis
Authors: Naik Bharat , Mallikarjuna J M 
Published: June 2024

Abstract
A homogeneous charge compression ignition (HCCI) engine is capable of producing high thermal efficiency with very low emissions. However, because of the limited upper load level constrained by knocking, the HCCI engine is not yet commercialized. Water injection can tackle this issue, enhancing the upper load limit without excessive heat release rate. However, the effectiveness of water injection depends on in-cylinder water evaporation, which in turn depends on water injection parameters. Therefore, this study is conducted to study the effect of water injector location on the combustion and performance characteristics of an HCCI engine by a computational fluid dynamic (CFD) analysis. The engine specifications and boundary conditions are taken from the literature. A three-dimensional computational fluid dynamics (3D CFD) model was developed using CONVERGE CFD coupled with detailed chemical kinetics to gain a better understanding of the phenomena of water injection in an HCCI engine. The CFD models used are validated from the available experimental data in the literature for the engine considered. Here, the water injector location is optimized based on the Water vapor distribution within the cylinder, nitric oxide (NOx) emissions, and maximum rate of pressure rise (MRPR). The results show that the water injector at 37 mm from the center of the cylinder gives better results than in other cases considered. With the optimum water injector location, the indicated mean effective pressure is increased by about 35.91% than without the water injection case. This study will be helpful in the development of HCCI engines.
3D CFD simulation of room air temperature and velocity with ceiling fan and exhaust fan and the resulting thermal comfort
Authors: Thomas Trino , Gedupudi Sateesh 
Published: June 2024

Abstract
The integration of energy-efficient solutions remains an essential hurdle in the pursuit of sustainable and comfortable indoor settings. As building energy consumption continues to climb, there is an urgent need to implement methods that reduce environmental effects, and at the same time, maintain adequate thermal comfort for occupant well-being and productivity. Ceiling fans, a standard fixture in many indoor settings, have gained popularity for their ability to provide better air movement and temperature adjustment while using substantially less energy than standard HVAC systems. This work presents a 3D Computational Fluid Dynamics (CFD) investigation of thermal comfort that can be achieved with a ceiling fan and an exhaust fan. A 3D fan zone model available in ANSYS Fluent was used to model the ceiling fan, considering the ceiling fan as a solid disc. Numerical methodology has been validated by verifying the transient simulation results against the experimental data available in the literature. The work analyzes thermal comfort parameters - temperature and velocity - in a room with a typical ceiling fan or an exhaust fan available in India. The room temperature and velocity distribution are presented for different times of a day in summer for a warm and humid climatic zone in India. The results show that the thermal comfort obtained with the exhaust fan is better than that with the ceiling fan for the evening, night, and early morning.
On the validation of numerical simulation with experimental results on compressible turbulent flow in an inertial particle separator device
Authors: Bahramian Linda , Amani Ahmad , Rigola Joaquim , Oliet Carles , David Pérez-Segarra C 
Published: June 2024

Abstract
To remove particles from entering the engine or Environmental Control System (ECS), an Inertial Particle Separator (IPS) can be situated in the intake. In IPS, a rapid change in flow direction is induced, and particles separate from the core outlet because of their inertia. Small particles with a low Stokes number (St) follow the flow and often enter the core outlet, while the large particles with a high St are thrown into the scavenge by their high inertia. Accurately capturing the unsteadiness of the fluid is crucial, especially with low scavenge mass flow fraction for the particles with low St. The numerical simulation of the compressible flow is validated here, implementing the 3D Improved Delayed Detached Eddy Simulation (IDDES) and the Reynolds-averaged Navier–Stokes (RANS) methods against experimental data. It is shown that the IDDES method can capture correctly the unsteadiness of the flow. After validation of the fluid phase, the particle separation efficiency was studied for different particle diameters using these turbulence numerical methods along with three different ambient temperatures: standard, hot, and cold. The separation efficiency values were in agreement with the experimental data.
Magnetocaloric refrigerator with magnetic pump and liquid metals
Authors: Rajamani Keerthivasan , Stolwijk Bob , Shahi Mina 
Published: June 2024

Abstract
One-seventh of the worldwide electricity is used for refrigeration related activities. When compared to the predominantly used vapor compression refrigeration system, magnetocaloric refrigeration provides an energy-efficient and eco-friendly alternative. It utilizes a magnetocaloric material which undergoes temperature changes when exposed to magnetic field changes. Nearly 60% of the total system cost is due to the permanent magnets used. For a given cooling power, the amount of permanent magnet needed is determined by the residence time required by the heat transfer fluid in each cycle. The start-of-the-art systems utilizes water-alcohol mixture as the heat transfer fluid, and a mechanical pump for its circulation. By utilizing non-toxic and non-hazardous gallium-indium-tin based liquid metals as heat transfer fluid, which has three order of magnitude higher thermal diffusivity, the residence time and the permanent magnetic material is reduced nearly by a factor of 10. Even accounting for the cost of the liquid metal, it results in considerable savings in the system cost. We present experimental results on the entropy change of using liquid metal with (Mn,Fe)2(P,Si)-based magnetocaloric material, and numerical results on the system level analysis. Further, to improve the reliability of the system, we propose to use magnetic pumping for heat transfer fluid circulation, which does not have any moving parts. The state-of-the art magnetic pump works at frequencies in the range of 100 to 1000 Hz. However, they cause detrimental heating effects due to eddy current losses. To overcome this, we have designed a pump that operates at 1 Hz and still achieves comparable flow rates. We present numerical results on the pump design by studying the dynamics of ferrofluid rise in a vertical pipe with multiple electromagnetic coils.
Characterization of different darken sand particles and behavior under fluidized and irradiated conditions
Authors: Cerutti-Cristaldo LM , Díaz-Heras M , Pérez-Flores JC , Canales-Vázquez J , Almendros-Ibáñez JA 
Published: June 2024

Abstract
The use of solid particles in a fluidized bed with concentrated solar irradiation from the top is a promising technology for the next generation of concentrated solar power (CSP) plants. Sand is an inexpensive and abundant material easy to fluidize, but it has a low absorptivity, which is around 0.5 according to different previous works. This optical property is a key parameter for CSP applications with solid particles. This work presents a novel methodology to induce darkening of the sand surface by inducing solid state diffusion of Mn in SiO2, rendering a stable material resistant to abrasion upon the fluidization process. For this study, two different samples considering different MnCO3:SiO2 weight ratios (1:30 and 1:50) were analyzed. The objective is to compare the two samples and optimize the concentration of MnCO3 to get the desired darkening of the sand and high absorptivity. First, the main properties of the particles were analyzed (particle size, morphology, color and absorptivity). Second, the samples were tested in a lab-scale fluidized bed directly irradiated from the top with a beam-down 4kW Xe lamp. Both samples were tested under three different fluidized velocities: 1.5, 2.0, and 2.5 times the minimum fluidization velocity (Umf). In both cases, there is a significant increase in the maximum temperature reached during the process, with temperatures exceeding 260 °C. This is clearly higher than the case of raw sand, which reaches 230 °C under the same conditions. Furthermore, these values exceed the highest temperature reached by SiC in the same facility, which is 250 °C, and it is considered as one of best tested materials for CSP applications.
Study on the difference in subcooling flow boiling of materials in a vertical rectangular channel at a low flow rate
Authors: He Sihong , Zhao Jiyun 
Published: June 2024

Abstract
Alloy materials with excellent properties are widely used in different industrial fields. Conducting flow boiling studies on alloy surfaces will help explore their applications in flow boiling, especially in heat exchange equipment. Five alloys were selected, including 304SS, Inconel600, Monel400, Zr4 and FeCrAl. Bubble dynamics in a vertically upward-flowing rectangular channel were observed using a high-speed camera under the condition of atmospheric pressure, 400 kg·m^-2·s^-1 mass flowrate and 5 K inlet subcooling. Results show that roughness and wettability cannot individually define material-sensitive heat transfer coefficient (HTC) and critical heat flux (CHF). Thermal effusivity shows a linear relationship to HTC. Material-sensitive CHF seems to be a power-law function of the nondimensional parameter of the product of the maximum nucleation site density and the minimum bubble nucleation area.
Analysis of microscale inner-grooved tubes during condensation of low-GWP R1234ze(E): Flow regime visualization and enhancement factors
Authors: Irannezhad N , Rossetto L , Diani A 
Published: June 2024

Abstract
In an attempt to attenuate the global warming contribution in the refrigeration industry, several regulations have been legislated. HydroFluoroOlefins (HFOs) could be construed as feasible candidates from which R1234ze(E) with GWP approximately equal to unity for various applications has been subjected to experimental investigations. Owing to its prevalence in many industrial applications, flow condensation and boiling inside tubes have received particular attention in such experimental campaigns. The current experimental investigation aims at determining the degree of augmentation of the thermal performance with the usage of inner grooved tubes. In this case, tubes with various geometrical properties are employed for flow condensation of R1234ze(E) at a saturation temperature of 30°C. Measuring the experimental heat transfer coefficient (HTC) allows obtaining the enhancement factor of the enhanced tube which is defined as HTC of an inner grooved tube to that of a conventional smooth tube of the same diameter. Furthermore, since the efficacy of enhanced surfaces is directly linked to prevailing flow patterns, for different operating conditions (G = 100 to 400 m−2 s−1, x = 0.01 to 0.95) the flow pattern has been identified with the aid of a high-speed camera. Lastly, results of flow pattern visualizations and enhancement factors are provided on a non-dimensional graph of EF (enhancement factor) versus JG
(non-dimensional gas velocity) that allows a comprehensive performance analysis of enhanced surfaces.
Effect of an artificial cavity on the microlayer and contact line dynamics during bubble growth in nucleate boiling
Authors: Tecchio C , Regoli I , Cariteau B , Zalczer G , Cabarrocas P Roca i , Bulkin P , Charliac J , Vassant S , Nikolayev V S 
Published: June 2024

Abstract
We present an experimental study on the near-wall phenomena during the growth of a single bubble in saturated pool boiling of water at atmospheric pressure. Our focus is on the dynamics of triple contact line and liquid microlayer that can form between the heater and the liquid-vapor interface of the bubble. The microlayer thickness, the wall temperature distribution and the bubble shape are measured simultaneously and synchronously at 4000 fps by white light interferometry, infrared thermography and sidewise shadowgraphy, respectively. To study the effect of cavities (artificial nucleation sites) we compare two experiments using different heaters. In the first experiment, the bubble grows on a smooth surface of nanometric roughness whereas in the second, the bubble grows over a cylindrical cavity of 25 µm diameter and 50 µm depth. We found that the cavity reduces three times the required wall superheating to trigger the bubble growth. Moreover, the radii of the bubble, microlayer and dry spot are smaller by half and the macroscale bubble dynamics is also slower. The microlayer is thinner and is measurable in a larger portion of its extent. Based on the absence of interference fringes near the contact line (due to high interface slopes) and on recent numerical simulations, we conclude that the microlayer consists in two regions: a dewetting ridge near the contact line that grows over time and a flatter and wider region that thins over time. The microlayer can be seen as a film deposited by the receding meniscus and its profile is controlled by the viscous and surface tension effects; its thinning over time is due to local evaporation only. The ridge is a result of liquid accumulation due to contact line receding and strong viscous shear in the film.
Flow boiling in microgravity
Authors: Mbaye Modou , Qaisar Raza Md. , Sebilleau Julien , Colin Catherine 
Published: June 2024

Abstract
This study reports some results obtained on nucleate flow boiling on an isolated nucleation site in microgravity. The experiments have been carried out aboard the International Space Station thanks to the Reference Multiscale Boiling Investigation (RUBI) device. Results reveal the pronounced influence of heat flux, subcooling temperature, flow rates on the bubble behavior, and more specifically on its growth rate. Deviations from the classical square-root time law of diffusive growth are observed at high subcoolings and high flow rates.
Superbiphilic hierarchical aluminum surfaces for exceptional pool boiling performance
Authors: Hadžić Armin , Može Matic , Zupančič Matevž , Golobič Iztok 
Published: June 2024

Abstract
The advancement in high-power electronic devices coupled with the need to ensure reliable and efficient heat dissipation of two-phase cooling systems underscores the urgent necessity for breakthroughs in enhancing boiling performance and especially critical heat flux (CHF) to minimize the risk of system failure. In this field, surfaces with tailored wettability have already demonstrated their potential to enhance boiling heat transfer intensity, while surfaces featuring wickable structures like micropillar arrays have shown significant improvements in CHF. In this study, we investigate the use of aluminium micropillar surfaces with tailored wettability to simultaneously enhance nucleate boiling heat transfer performance and specifically increase of the CHF. We fabricated the micropillar surfaces using a combination of nanosecond laser texturing and chemical etching in hydrochloric acid, while the wettability of selected surfaces was further tailored by application of a fluoroalkyl phosphonic acid and an additional laser texturing step. Three micropillar patterns were tested under pool boiling conditions using saturated twice-distilled water at atmospheric pressure. Importantly, our results revealed that the bottom part of the boiling interface (i.e., the superhydrophilic area) ensured increased liquid supply, while the top parts (i.e., the superhydrophobic area) tend to serve as nucleation sites. When combined, these two effects allowed us to simultaneously improve the CHF and the heat transfer coefficient, resulting in enhancements of up to 113% (2343 kW m−2) and 450% (205 kW m−2 K−1), respectively, compared to the benchmark untreated surface. This research provides a practical and reliable approach to enhancing heat transfer by fabricating hierarchical surfaces, offering potential applications in ultrahigh heat flux thermal technologies.
Flow boiling in microchannels coupled with micro-nano-modified surfaces
Authors: Pontes P , Perez M , Moreira A L N , Moita A S 
Published: June 2024

Abstract
This paper addresses part of a wider project aiming at the development of a microchannel based heat sink to cool photovoltaic panels. The work presented here gives emphasis to working conditions leading to flow boiling in a microchannel and focuses on flow instabilities and on the potential effect of surface microstructuring in heat transfer enhancement and in controlling such instabilities. After identifying the flow boiling regimes, the observed phenomena are qualitatively and quantitatively described. The results show that a regular pattern of microcavities on the surface to cool enhances heat transfer and promotes the occurrence of a more stable flow.
Enhanced Pool Boiling Heat Transfer with Porous Ti-6Al-4V-Coatings Produced by Cold Spray Metal Additive Manufacturing
Authors: Garivalis Alekos Ioannis , Chen Yan , Shatskiy Evgeny , Robinson Anthony , Marco Paolo Di , Lupoi Rocco 
Published: June 2024

Abstract
In advancing industrial heat transfer mechanisms, surface coatings offer significant potential. This research elucidates the efficacy of the metal additive manufacturing Cold Spray deposition technique for producing enhanced boiling surfaces, specifically focusing on Ti-6Al-4V (Ti64) coatings on Aluminium substrates. This offers a rapid and low-cost fabrication method for producing lightweight enhanced boiling surfaces. The Cold Spray method is typically used to create dense metal deposits. Here, the process has been specially tuned to create highly inhomogeneous honeycomb-type porous Ti64 coatings. Critical Cold Spray deposition parameters, such as particle velocity, preheat temperature, and deposition rate have been identified to create repeatable porous coatings, with thicknesses of up to 3.0 mm achievable. Following deposition, several samples were subjected to systematic boiling heat transfer tests in a purpose-built pool boiling apparatus. Boiling curves were generated for the augmented Cold Spray surfaces as well as a bare surface, with the latter acting as a baseline to which enhancement levels were assessed. Initial data analysis shows that some of the tested surfaces exhibit a notable increase in boiling heat transfer coefficient and Critical Heat Flux (CHF). This enhancement is potentially attributed to increased surface area, increased nucleation site density, capillary wicking, and mitigation of lateral bubble coalescence, though excessive coating thickness may degrade heat transfer. In summary, the novel Ti64 surface structures developed using the Cold Spray deposition technique exhibits high potential for industries necessitating superior boiling heat transfer performance. Importantly, the manufacturing process is industrially scalable, offering the capacity to rapidly coat large areas at low cost compared with subtractive manufacturing other metal additive manufacturing methods.
Study of nucleate boiling growth regime on thin surfaces.
Authors: Jaunet Y , Bucci M , Zupančič M , Sebilleau J , Colin C , Golobič I 
Published: June 2024

Abstract
In a context of energy transition, heat exchanges are a key for energy sobriety. Among those exchanges, nucleate boiling is the preferred heat transfer method for high heat flux. Vaporisation plays an important role in the nuclear industry, but also in thermal machines such as cooling systems in data centers. In spite of decades studying boiling thermodynamics, modelling heat transfers in the nucleate boiling is still a major difficulty because of its numerous parameters. In the 1960s, scientists developed promising models called heat flux partitioning models. These models have been improved over the years, but they need closure laws about bubbles dynamics and nucleation site density. For the purpose of improving those models, we took part in an international collaboration (ANR TraThI) to study interface heat transfer. Project focuses on boiling with a controlled nucleation site density with a strong emphasis on studying isolated bubbles in water pool boiling, and later addressing multiple bubble interactions in pool and flow boiling. This work focuses on the bubble growth regimes on thin metallic foil observed in a water pool boiling experiment, with a distinction between microlayer and contact line growth regime. Pulsed nanosecond laser was used to create active nucleation site, while high-speed infrared thermography and shadowgraphy were implemented to record transient wall temperatures and bubble dynamics, respectively. This work shows that our experimental configuration induced two different bubble growth regimes, depending on the imposed heat flux and the recent past at the nucleation site and its vicinity. Study provides a framework for further in-depth investigations with different experimental configurations.
Bubble dynamics in high-pressure flow boiling conditions
Authors: Kossolapov Artyom , Hughes Matthew T. , Phillips Bren , Bucci Matteo 
Published: June 2024

Abstract
High resolution measurements of key parameters relevant to bubble departure processes in high-pressure water systems has been a major challenge over the past several decades due to the small size and fast motion of vapor bubbles, making conventional optical measurements unreliable. Addressing this difficulty is critical, as accurate bubble departure data and computationally inexpensive models are needed for future two-phase heat transfer models. To close this gap, we use high-speed imaging to track bubble size and velocity in high-pressure flow boiling conditions (10 – 40 bar). It is observed that bubbles are almost always perfectly spherical in shape and slide along the boiling surface immediately after nucleating. To predict sliding, we conduct a force balance on the bubble and derive an equation of motion in the direction of the bulk flow. Interestingly, we find that at high pressure conditions, the equation of motion can be significantly simplified, resulting in an analytical expression for the bubble motion, growth time and departure diameter, allowing us to develop simple and computationally efficient equations. The applicability of the model and departure criterion across a broader range of high-pressure conditions is discussed, and recommendations for further characterization of bubble departure processes are made.