bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nanoscale and Macroscale Effects of Mineral Deposition During Water Evaporation on Nanoporous Surfaces
Authors: McClure Emma R. , Carey Van P. 
Published: September 2020

Abstract
Recent studies have indicated that droplet evaporation heat transfer can be substantially enhanced by fabricating a thin nanoporous superhydrophilic layer on a metal substrate. Such surfaces have immense potential to improve spray cooling processes, however, little durability testing of the surfaces have been performed. In spray cooling applications, as water evaporates any impurities in the water will be deposited onto the surface. Primarily, this investigation serves to demonstrate how minerals in hard water deposit on the surface and interact with the ZnO nanopillars of the superhydrophilic surface. Quantifying the effects of mineral scale on droplet spreading and vaporization heat transfer on the surface is important in determining implementation requirements to advance the surface into industry applications. Micrographs of the surface demonstrate minerals deposit nonuniformly, and quickly fill the nanostructure. Despite a reduction in the extent of droplet spreading due to the mineral deposition, scaled surfaces still demonstrated improved thermal performance compared to the uncoated, smooth copper surface. Scale tended to build up on previously deposited scale leaving largely uncoated areas where droplets chose to preferentially spread resulting in a continued low contact angle. Maintaining these uncoated areas and reducing the contaminants present in the water will extend the life and performance of the nanostructured surface.
Temperature Distribution in a Turbulent Flow in the Heat Pollution Phenomena
Authors: Radulescu Victorita 
Published: September 2020

Abstract
The thermal pollution, with major effects on the water quality degradation by any process involving the temperature transfer, represents nowadays a major concern for the entire scientific world. The turbulent heat and the mass transfer have an essential role in the processes of thermal pollution, mainly in problems associated with the transport of hot fluids in long heating pipes, thermal flows associated with big thermo-electric power plants, etc. In the last decades, the problems of the turbulent heat and mass transfer were analyzed for different dedicated applications. The present paper, in the first part, estimates the universal law of the velocity distribution near a solid wall, with a specific interpretation of the fluid viscosity, valid for all types of flows. Most of the scientific researches associate nowadays both the turbulent heat and the mass transfer with the Prandtl number. In the turbulent fluid flow near a solid and rigid surface, there are three flowing domains, laminar, transient, and fully turbulent, each one with its characteristics. In this paper, it is assumed that the friction effort at the wall remains valid at any distance from the wall, but with different forms associated with the dynamic viscosity. By using the superposition of the molecular and turbulent viscosity and by creating the interdependence between the molecular and turbulent transfer coefficients is estimated the mathematical model of the velocity profile for the fluid flow and temperature distribution. Three supplementary hypotheses have been assumed to estimate the dependence between the laminar and thermal sub-layer and the hydrodynamic sub-layer. The theoretical obtained distribution was compared with some experimental results from the literature and it was observed there is a good agreement between them; the differences are smaller than 3%. In the second part of the paper is determined the temperature field for a fluid flowing also in presence of the solid surfaces with different temperatures, associated not only with the Prandtl number but also with the fluid viscosity and its dependence with the temperature, correlated with the Grashoff number. In the next paragraph is used the concept of the laminar substrate with different thicknesses for the hydrodynamic flows with thermal transfer to the solid walls, and also the inverse transfer from the solid walls affecting the fluid flow and the mass transfer. The obtained mathematical model is correlated with the semi-empirical data from the literature. By numerical modeling, the obtained results were compared with the experimental measurements and it was determined the dependence between the Stanton number and the Prandtl number. The numerical results demonstrate a good agreement with the experimental results in a wide range of the Prandtl numbers from 0.5 to 3000. Finally, are mentioned some conclusions and references.
Mechanical Performance of Concrete Thermal Energy Storage Subject to Operating Thermal Demands
Authors: Wang Shuoyu , Abdulridha Ahmed , Quiel Spencer , Naito Clay , Sulieman Muhannad , Caspar Justin , Bravo Julio , Neti Sudhakar , Romero Carlos , Yao Zheng , Oztekin Alparslan 
Published: September 2020

Abstract
This paper presents a lab-scale investigation of the use of structural concrete for sensible heat storage in power plants. Transient thermal and mechanical analyses are simulated via coupled finite element models to study the thermo-mechanical performance of a cylindrical concrete block with 4-in diameter and 8-in length under thermal loading. The model is validated by performing experiments on high strength concrete (HSC) cylinders with this geometry in an oven, which heats the specimens from the outside. The models are then modified to simulate thermal energy storage (TES) application with thermal loading applied at the interior surface of a hole running through the longitudinal center of the cylinder. Thermal cycles have a varying heating rate (5, 10, or 24 hours) followed by consistent durations of soaking (2 hours) and cooling (13 hours). In the TES simulations, a steel jacket is also applied to the external surface of the concrete cylinder to provide confinement. The resulting thermal distribution and maximum principal stresses during heating and cooling are observed as a function of time. This study provides insight into the mechanical requirements and impact on material integrity for concrete modules subjected to representative TES heating regimes.
Experimental Study on the Thermal-Hydraulic Performance of Louvered Fin and Flat Tube Heat Exchangers
Authors: Khan Tariq Amin , Li Wei , Xiaolong Yan , Yang Zhuo 
Published: September 2020

Abstract
In this study, the air side heat transfer and pressure drop characteristics of flat tube with louvered fins compact heat exchangers have been experimentally investigated. Three samples of heat exchangers, i.e., one without fins, one with flat louver fins and one with corrugated louver fins are studied. The louvers in the present samples have small louver pitch (Lp = 0.8mm) and high louver angle (θl = 37°) due to the space constraints in automotive applications. The performance tests were conducted in a high standard test facility which are composed of an evaporator chamber, condenser chamber and auxiliary units. In our study, only evaporators are tested and hence the condenser section is the same during the tests.
Experimental results under the wet surface conditions show that the cooling capacity and pressure drop performances of evaporator with flat louver fins (HX2) is higher than the one with corrugated louver fins (HX3) while the evaporator without fins has the minimum heat transfer due to no interruptions. This can be due to higher number of tubes in the case of HX2 having small tube pitch. However, the overall performance (ratio of heat transfer per unit volume to pressure drop per unit volume) of HX2 is better than HX3 which signifies the importance of corrugated louver fins.
Copper-Carbon Nanotube Micropillars for Passive Thermal Management of High Heat Flux Electronic Devices
Authors: Rojo Gerardo , Darabi Jeff 
Published: September 2020

Abstract
Miniaturization of electronic products and a consequent rapid increase in power density of advanced microprocessors and electronic components have created a need for improved cooling techniques to efficiently remove heat from such devices. Traditional air-cooled heat sinks have been utilized for several decades as the most cost-effective cooling technique for electronic cooling applications. However, the existing thermal management solutions are unable to maintain the temperature of the next generation of complex electronic systems within acceptable limits without adding considerable weight and complexity. This paper reports a microstructured wick for application in passive thermal management systems such as heat pipes and vapor chambers. The wick structure consists of mushroom-like composite copper-carbon nanotubes (Cu-CNT) micropillars. The small spacing between micropillar heads provides a higher capillary pressure whereas the large spacing between the base of micropillars provides a higher permeability for liquid flow. The micropillar array was fabricated on a copper substrate using an electroplating technique. The micropillar array was then tested in a controlled environment to experimentally measure its thermal performance under several operating conditions. A heat removal capability of 80 W/cm2 was demonstrated at a wall superheat of 15° C. In addition, a computational study was performed using ANSYS Fluent to predict the thermal performance of the micropillar array. Model predictions were compared with the experimental results and good agreement was obtained.
Impact of Micropillar Density Distribution on the Capillary Limit of Heat Pipes
Authors: Hassaine Daoudji Doriane Ibtissam , Struss Quentin , Amnache Amrid , Léveillé Étienne , Salim Shirazy Mahmood Reza , Fréchette Luc G. 
Published: September 2020

Abstract
This paper shows the performance enhancement of heat pipes by tailoring the density distribution of micropillar wicks to minimize viscous pressure loss while maintaining sufficient capillary pumping. In a heat pipe, capillarity and permeability are linked, since small pores create higher capillary pumping while unfortunately inducing more pressure drop along the heat pipe. This pressure loss accumulates along the heat pipe, leading to a non-uniform pressure difference between the liquid and vapor. Therefore, we do not need a uniform capillary pressure to withstand this difference. This provides the opportunity to spatially tailor the wick structure, aiming for a high capillarity to pump the liquid, but a low permeability to induce less pressure loss. Our study offers a compromise between capillarity and permeability by designing the density distribution of the pillar wick structure. This density distribution, which was not studied before, will be shown to enhance the heat pipe performance.
The theoretical models show that a tailored density distribution can enhance the heat pipe performance by a factor of 1.5. To support this result, ‘rate of rise’ measurements along a pillar array demonstrate that the liquid pressure loss in a tailored density array are less compared to a constant pillar density.
Effect of Temperature on Velocity Profiles of Ions and Water Molecules in Charged Nanotubes
Authors: Wang Yu , Liu Zhenyu 
Published: September 2020

Abstract
High surface charge density makes it possible for charge inversion to occur in the electrical double layer, in which cases, flow reversal appears for electroosmotic driven flow that is one of the best-known methods of fluid transport based on the electro-kinetic phenomenon. Reverse electroosmotic flow of an aqueous solution of KCl was studied using MD method in this work. Nonequilibrium molecular dynamics simulations were carried out to investigate the effect of temperature on velocity profiles of ions and water molecules confined in charged carbon nanotubes (CNTs) with a diameter of 3.0 nm. The results demonstrate that the temperature dependence of velocity of ions and water molecules is obviously different for various distances to the tube wall. It is found that the temperature has a direct effect on the ion velocity profiles, that is, as the temperature increases, the velocity of either counter-ion or co-ion in the diffuse layer increases significantly though the velocity drops sharply in the vicinity of the tube wall surface. As for water molecules, the MD simulations show plenty of velocity profiles, in which the velocity is slightly positive near the tube wall, but is negative in most of the rest region. The temperature effect on reverse electroosmotic flow is clearly observed, which is reflected in two aspects: the viscosity of the fluid and the velocity profiles of ion and water molecule.
Numerical Investigation of Single Bubble Dynamics Passing a Mesh-Based Structure
Authors: Alnaimat Fadi , Mathew Bobby , Alhammadi Omar 
Published: September 2020

Abstract
In this article, investigations of the dynamic behaviors of a single bubble flowing across a mesh-based structure domain was conducted using the volume of fluid (VOF) model. The study was investigated in various mesh structure sizes, including hole size and gap distance. The fundamental behavior of bubble deformation and the effects of gap sizes were analyzed. Subsequently, the predicted dynamics of the deforming bubble area and the effect of the surface tension were examined inside the mesh holes. The discharging bubbles from the mesh structure resulted in a slight difference in the physical features from the original bubble dynamics before entering the mesh (flow restriction). This drafted the bubbles in different trajectories and led to behave differently based on the mesh characteristics. The complex interactions and the subsequent deformations were observed between different mesh sizes. For the validation of the bubble dynamics, the results of computational fluid dynamics (CFD) simulation were tested under different mesh sizes detailing the velocity field, exiting trajectory, bubbles deformation, and residence time, which helps to reveal the affected parameters on the separation mechanism of the original bubble.
Technique for Determining Local Nucleate and Film Boiling Correlations for Large Diameter Tubes
Authors: Azih Chukwudi , MacCoy Reilly , Mazhar Hazem , Fraser Chris 
Published: September 2020

Abstract
The boiling behaviour on the surface of large diameter tubes is known to be strongly dependent on the local orientation of the surface around the circumference. Understanding such local variations in boiling behaviour is of particular interest in the CANDU® nuclear industry, where part of the heat removal path for cooling the fuel under postulated accident conditions is via pool-boiling on the surface of the 132 mm diameter calandria tube that is immersed in a pool of the heavy water moderator. While the average pool boiling behaviour of the calandria tubes has been well studied with integrated experiments, local boiling correlations have not been developed for prototypical diameter calandria tubes. Local boiling correlations will allow for more detailed modelling of postulated accident scenarios and better quantification of safety margins. In this study, the nucleate and film pool-boiling characteristics of a large diameter Zircaloy-2 CANDU® calandria tube were tested in a pool of subcooled water. A novel technique is developed to derive the local boiling curve along the circumference of the tube, involving the local heating, measurement of the wall temperature, and heat flux. The adequacy of the technique is determined by comparing the local boiling curves with previous experiments in which averaged pool boiling characteristics were obtained.
Inverse Model for Fire Heat Release Rate Using Deep Neural Networks
Authors: Kou Luyao , Wang Xinzhi , Zhang Hui , Yang Rui , Liu Yi 
Published: September 2020

Abstract
The estimation of heat release rate (HRR) in a building fire is a meaningful yet challenging task to improve first emergency response. Inspired by the capability of deep learning method that mines patterns from raw data, the inverse model based on Gated Recurrent Unit (GRU) is presented for the inversion of HRR. First, a series of fire scenarios is simulated to form the dataset by forward fire modeling. Second, GRU is applied to learn representations from windows of time-series sensor data. Output layer is used to map the learned representations to targets. Third, the HRR is estimated by the trained GRU network with observed data from the fire. Finally, the accuracy and efficiency of the inverse model are evaluated in a multi-compartment configuration. Preliminary results indicate that GRU network can be applied to the inversion of fire HRR with higher accuracy and efficiency.
Experimental Investigation on Heat Transfer of Water Spray Cooling by Addition of n-Butanol
Authors: Cai Chang , Liu Hong , Chen Han , Zhao Chuanqi , Gao Jiuliang , Jia Ming , Yan Yan'an 
Published: September 2020

Abstract
Heat transfer characteristics of water spray cooling with n-butanol additive were experimentally studied in this paper. The results indicated that adding n-butanol can effectively enhance the heat dissipation and control the surface temperature. The optimal concentration of n-butanol corresponding to the best heat transfer performance is 0.5 vol%. The experimental Nusselt numbers also agree well with a previous correlation with Weber, Prandtl, Jacob and Reynolds numbers, evidenced by a maximum absolute error of 6.34%. The measurement also showed that the decrease of surface tension and contact angle of the n-butanol-water mixture is the main mechanism to enhance the spray cooling heat transfer, while other physical properties also play an important role. The surface temperature non-uniformity in the radial direction is more apparent at a high heat flux while the addition of different contents of n-butanol has a negligible effect.
Experimental Investigation of a PCM-Based Topology Optimized Heat Sink for Passive Cooling of Electronics
Authors: Ho Jin Yao , Leong Kai Choong 
Published: September 2020

Abstract
A thermal energy storage unit filled with phase change material (PCM) can serve as a heat sink for the cooling of electronics with intermittent or periodic heat dissipation rates. The use of thermal conductive structures (TCS) is an effective method of improving the thermal performance of a PCM-based heat sink. In this paper, topology optimization is explored to develop a new class of TCS with a tree-like structure to enhance the thermal performance of a trapezoidal heat sink. The topology-optimized heat sink was then fabricated by Selective Laser Melting (SLM) using an aluminum alloy, AlSi10Mg, as the base powder. Experiments were performed to evaluate the thermal performance of the topology-optimized heat sink with the tree-like structure. In addition, a conventional longitudinal-fin heat sink of the same solid volume fraction (φ = 16.2%) and a heat sink without enhanced structure were also fabricated and experimentally investigated for comparison. Rubitherm RT-35HC paraffin wax was used as the PCM. Three different heat fluxes of 4.00 kW/m2, 5.08 kW/m2 and 7.24 kW/m2 were applied at the base of each specimen by a silicone rubber heater. The structure wall and the PCM temperatures were measured over time. Our results show that, for all heat rates tested, the topology-optimized heat sink was able to maintain a lower base temperature as compared to the fin-structure and the plain heat sinks. A thermal enhancement ratio (ε) is defined to evaluate the performance of the heat sinks with and without the use of PCM. From the experimental results, the highest ε value of 8.6 was achieved by the topology-optimized heat sink. These results indicate the better performance of the topology-optimized heat sink in dissipating heat as compared to the other specimens.
Improved Accuracy of a Machining Tool With a Constant Cutting Speed Vector and Outside Approach Path
Authors: Suzuki Takamaru , Iwama Shoya , Hirogaki Toshiki , Aoyama Eiichi , Ikegami Takakazu , Akai Takayuki 
Published: September 2020

Abstract
A five-axis machining center is equipped with a direct drive motor on a rotary axis and is capable of synchronous control, which makes it a feasible tool for quickly and accurately machining complicated three-dimensional surfaces such as propellers and hypoid gears. However, the accuracy of the machined shape and consistency of the freeform machined surface both need to be improved. We developed a method for maintaining the feed speed vector at the milling point by controlling three axes of the five-axis machining center (two linear and one rotary) to improve the quality of the machined surface considering differences in the servo characteristics of the three axes during the actual process. Experimental results showed that using the proposed method with an outside approach path for the machining tool greatly reduced the shape error. The effectiveness of the proposed method was verified by using a wireless Internet of Things holder to monitor the machining force.
Design of a Two-Piece Brassiere Cup From its Data Points Toward its Automation
Authors: Yoshida Kotaro , Wakamatsu Hidefumi , Morinaga Eiji , Kubo Takahiro 
Published: September 2020

Abstract
A method to design the two-dimensional shapes of patterns of two piece brassiere cup is proposed when its target three-dimensional shape is given as a cloud of its data points. A brassiere cup consists of several patterns and their shapes are designed by repeatedly making a paper cup model and checking its three-dimensional shape. For improvement of design efficiency of brassieres, such trial and error must be reduced. As a cup model for check is made of paper not cloth, it is assumed that the surface of the model is composed of several developable surfaces. When two lines that consist in the developable surface are given, the surface can be determined. Then, the two-piece brassiere cup can be designed by minimizing the error between the surface and given data points. It was mathematically verified that the developable surface calculated by our propose method can reproduce the given data points which is developable surface.
Study on Adhesion With Stress and Temperature in Drilling of Aluminum Alloy
Authors: Matsumura Takashi , Arakawa Satoshi , Tamura Shoichi 
Published: September 2020

Abstract
Aluminum alloys have been widely used for automobile and aircraft parts. In cutting of aluminum alloy, adhesion sometimes occurs to deteriorate surface finish. The study discusses the adhesion characteristics in drilling of aluminum alloy (A7075) with a flat tool at a point angle of 180 degrees.
The adhesion volumes on the rake face of the tool were measured in drillings of blind holes for the cutting speeds and the feed rates. Then, the stress and the temperature distributions were estimated in the cutting simulation. In the simulation, the cutting force is predicted in the chip flow model based on the minimum cutting energy. The cutting temperature is analyzed in Finite volume method using the result in the cutting force prediction. The adhesion volumes are associated with the stress and temperature on the rake face. The adhesion volume becomes large in the temperature ranged from 400 to 500 K. The adhesion volume increases with the stress up to 500 MPa.
Scheduling-Based Adaptive Operations of Handling Manipulators to Reduce Downtime in Manufacturing Systems
Authors: Yonemoto Ryo , Suwa Haruhiko 
Published: September 2020

Abstract
Unexpected interruptions in manufacturing such as machine breakdowns often incur degradation of productivity. This study aims to build an automatic scheduling method that responds to the occurrence of uncertain events flawing a schedule and catch up the planned schedule as quickly as possible. We here focus on building adaptive operations of a material handling robot according to the predetermined schedule revision policy to cope with uncertainties and to reduce the total downtime of the manufacturing system. The applicability of the proposed method is demonstrated through physical experiments.