bluuebunny/crossref_metadata_2025_split huggingface dataset:
Particle Transport and Deposition in a Ventilated Room With a Standing Mannequin
Authors: Azhdari Mehrdad , Tavakol Mohammad Mehdi , Ahmadi Goodarz 
Published: October 2020

Abstract
This study presents the results of a series of numerical simulations for airflow field and particle dispersion and deposition around a mannequin standing inside a ventilated room. A 3-D airway model was constructed from the nostril inlet to the end of 4th lung generation and was integrated into the standing mannequin model in the room. The computational domain included the region around the mannequin and inside the respiratory system. The room was ventilated by a mixing air-conditioning system that supplied air with a speed of 3m/s from a diffuser mounted on the top of the sidewall and exited from a damper mounted at the bottom of the side or front walls. In the first mode, the diffuser and damper were located on the wall in front of the mannequin and in the second mode on the wall at the right side of the mannequin. The mean airflow field inside the room was obtained by solving the Navier-Stokes and continuity equations using the Ansys-Fluent software. The k-ω SST transitional model was employed for turbulence modeling. Then, spherical particles with 5, 10, 20, and 40 μm diameter and unit density were released into the room, and their trajectories were tracked by using the Lagrangian trajectory analysis approach. Aspiration efficiency and deposition of particles for inhalation flow rates of 15 and 30 lit/min were analyzed with the improved discrete random walk (DRW) stochastic model using a user-defined function (UDF) coupled into the Ansys-Fluent discrete phase model. Simulation results for the mean airflow showed the formation of a large recirculation zone inside the room. In the first mode, the main recirculation zone formed behind mannequin that carried the flow streamlines toward the mannequin breathing zone. In the second mode, the recirculation formed in front of the mannequin face that led the streamlines out of the breathing zone. The simulation results for particle inhalation showed that the aspiration efficiency of particles is higher in the first ventilation mode compared to the second mode. Results also showed that the total deposition of particles in the airway passage increases as particle size increases.
Volumetric Three-Componential Velocity Measurements (V3V) of Flow Structure Behind Mangrove-Root Type Models
Authors: Kazemi Amirkhosro , Castillo Eduardo E. , Curet Oscar , Hortensius Ruben , Stamatios Pothos 
Published: October 2020

Abstract
Mangrove roots produce complex flow structure interactions with their environment, which affect the nutrient, habitat and aquatic animals. Analysis of the flow structure behind the roots extends to a broad range of mangrove-inspired applications that provides understanding into complex flows encountered in unidirectional riverine flows. In this work, we modeled the mangrove roots with a cluster of rigid circular cylinders to investigate the vortex structure downstream of the models. The vortex organization of the patch of cylinder wakes was studied experimentally by time-resolved volumetric three-componential volumetric velocimetry (V3V) at Reynolds numbers 1014 and 3549. The results show that the vortex structure in the 3-D flow field reveals a regular shedding at Re = 1014, forming von Kármán vortices dominating the 3D motion. The flow structure behind rigid patches is coherent and the streamwise velocity remains unchanged. The regime for a flexible patch at Re = 3549 produces an intricate pattern where the multiple counter-rotating vortexes distorted substantially and forming a chain of rhombus-like vortex cells in the near wake. The information for the 3D flow feature provides useful information to a robust structure for Seawall erosion.
Uniform and Gaussian UV Light Intensity Distribution on Droplet for Selective Area Deposition of Particles
Authors: Li Tianyi , Kar Aravinda , Kumar Ranganathan 
Published: October 2020

Abstract
Particle transport through Marangoni convection inside a sessile droplet can be controlled by the UV light distribution on the surface. The photosensitive solution changes the surface tension gradient on the droplet surface and can induce clockwise and counter-clockwise circulations depending on the incident light distribution. In this paper, the stream function in the sessile drop has been evaluated in toroidal coordinates by solving the biharmonic equation. Multiple primary clockwise and counter-clockwise circulations are observed in the droplet under various concentric UV light profiles. The downward dividing streamlines are expected to deposit the particles on the substrate, thus matching the number of deposited rings on the substrate with the number of UV light rings. Moffatt eddies appear near the contact line or centerline of the droplet either due to a sharp change in the UV light profile or because the illuminated region is away from them.
Open-Source Accelerated Vortex Particle Methods for Unsteady Flow Simulation
Authors: Stock Mark J. , Gharakhani Adrin 
Published: October 2020

Abstract
A new open-source CFD solver is being developed based on the vorticity transport equations for simulation of unsteady incompressible flow in complex geometries. This is a hybrid approach, which uses a compact high-order finite-difference method to predict the flow in the near-boundary region and a Lagrangian Vortex Particle Method (LVPM) for the off-boundary vorticity-containing region. This paper focuses on the latter, presenting the particular LVPM implemented in the package and demonstrating selected benchmarks from simulations of flow in 2D lid-driven cavity, flow around a rotating cylinder (both at Re = 1,000), and impulsively started flow over a sphere at Re = 25, 40, 60, 80, 100. In addition, novel ideas on the development of an efficient and lightweight Graphical User Interface (GUI), as well as new approaches to cross-platform hardware acceleration for Teraflop/s computing on a desktop — achieving over two orders of magnitude speedup vs. an optimized serial code — are discussed.
Developing an Optimum Design of the Double Layer Microchannel Heat Sink for High Speed CPUs
Authors: Radwan Ali , Abo-Zahhad Essam M. , Abdelrehim O. , El-Shazly A. H. , Ookawara Shinichi , Awad M. M. , El-Kady M. F. , Elmarghany Mohamed R. , Salem Mohamed S. , Shouman Mahmoud A. 
Published: October 2020

Abstract
High speed CPUs and electronic chips usually dissipate relatively large quantities of energy in the form of heat. The limited available cooling space requires innovative and efficient thermal management techniques. These techniques must accomplish low operation temperatures along with uniform temperature distribution over the chip surface. Recently, several researches focused on developing different microchannel heat sink (MCHS) designs for this purpose. Among these designs is the double layer microchannel heat sink (DL-MCHS), which can be operated in either parallel flow (PF) or counter flow (CF) operation modes. The thermo-hydraulic characteristics of this heat sink was comprehensively investigated in the literature using numerical methods. However, based on the authors literature survey, all the previous numerical investigations considered the computational domain as a straight section with multi-channels in each layer. This approach assumes a uniform velocity for all the flow channels in each layer and neglect the effect of the inlet and outlet headers. In addition, the heat interaction between the coolant in both layers through the header section was not considered. These assumptions cause a considerable discrepancy between the numerical results in the literature and the realistic conditions. Therefore, in this work, a detailed 3D conjugate heat transfer model is developed. In this 3D model, DL-MCHS is designed with and without headers. The designed heat sinks are operated under PF and CF conditions. For a specific electronic chip with dimensions of 13 mm × 40 mm at a heat flux of 5 kW/m2. The model is validated with the experimental results in the literature. It is found that, including the header design in the simulation of the DL-MCHS must be considered in the simulation to predict the accurate thermo-hydraulic performance of the DL-MCHS specially in the CF. Further, using the DL-MCHS in PF operation accomplished a lower average chip temperature compared with the CF. Furthermore, at high coolant flowrate, neglecting the effect of the header in the CFD calculations can be approximated to predict the chip surface temperature. And finally, neglecting the header in the CFD calculations significantly affect the calculated pumping power for both PF and CF operated DL-MCHS.
Four Compartments Stepwise Varied Width Microchannels Cooling Approach for Densely-Packed Module of Concentration Photovoltaics
Authors: Abo-Zahhad Essam M. , El-Shazly A. H. , Ookawara Shinichi , El-Kady M. F. , Ali Abdallah Y. M. , Elqady Hesham I. , Elmarghany Mohamed R. , Salem Mohamed S. , Shouman Mahmoud A. , Radwan Ali 
Published: October 2020

Abstract
The high concentration of solar radiation on the multijunction solar cells used in the highly concentrated photovoltaic modules cases a very high cell temperature. Also, high cell temperature operations overall performance and increase thermal stresses. Therefore, an efficient cooling arrangement is mandatory to achieve a higher net output power from the high concentrator photovoltaic structures. In this work, the comprehensive three-dimensional (3D) model was developed and manipulated to investigate the performance of an HCPV system under the active cooling scheme to figure out its ability to handle effective heat dissipations. Various novel cooling microchannels manifold designs were numerically investigated and compared in the term of cooling down a densely packed high concentration photovoltaic. The solar cell type is the latest product of AZURSPACE triple junction of 3 × 3 mm2 solar cell. A 64 multijunction solar cells (electrical efficiency of 42.3% at cell temperature 25 °C) module were considered in this work. The influence heat sink design, channel dimensions, and inlet flow rate on the cooling performance of the manifold heat sink device were examined. The same external dimensions are considered, and the flow was laminar and the inlet temperature 25 °C for all designs for a reasonable comparison. the heat sink material the maraging steel. The concept of dividing the heat sink area to many segments is adopted to improve the heat removal capacity. The concept of channel width variation along the flow stream length was studied. The heat sinks including rectangular channels were adopted as they are easy to be fabricated. The limitations of 3D metal printing and pumping requirements were considered for all proposed designs where the minimum channel width is 0.8 mm. The comparison between all studied designs is highlighted concerning surface average temperature surface temperature uniformity and pressure drop.
Heat Transfer and Fouling Performance During Falling Film Evaporation in Vertical Porous Tubes
Authors: Wang Lei , Tang Weiyu , Zhao Limin , Li Wei 
Published: October 2020

Abstract
An experimental investigation was conducted on falling film evaporation along two porous tubes, which were sintered by stainless-steel powder with a diameter of 0.45 and 1 um, respectively. The test section is a 2 m long sintered tube with an outer diameter of 25 mm and a wall thickness of 2 mm. During the experiment, the pressure inside the tube was maintained at 1 atm, the inlet temperature was 373 K, and mass flux ranged from 0.51 to 1.36 kg/ (m s). Conditions of the steam outside the pipe, which was the heat source, were fixed, while the fouling tests were carried out at a constant mass flow of 0.74 kg/ (m s) using high-concentration brine as work fluid. The overall heat transfer coefficient under different working conditions was tested and compared with the stainless steel smooth tube of the same dimensions. The heat transfer coefficient of the two porous stainless tubes are about 35% and 20% lower than that of the smooth one, showing an inferior effect because the steam in the pores of the pipe wall during the infiltration process will reduce the heat conductivity. The heat transfer coefficient of the smooth tube deteriorated severely due to the deposition of calcium carbonate, which had little effect on the sintered tubes. Besides, the fouling weight of porous tubes is 2.01 g and 0 g compared with 5.52 g of the smooth tube.
Condensation Characteristics of Flows Inside the Three-Dimensional Enhanced Tubes
Authors: Zheng Boren , Shen Kunrong , Li Wei , Ma Xiang , Zhang Chuancai , He Yan , Ke Hanbing , Lin Yuansheng 
Published: October 2020

Abstract
This paper presents experimental condensation characteristics of R134a inside two three-dimensional enhanced heat transfer tubes (1EHT1 and 3EHT) and one equivalent smooth tube. The 1EHT1 tube has the primary elliptical dimples and secondary petal arrays, and the 3EHT tube has the grooves and square bulge. All the tested stainless-steel tubes have the same outer diameter of 15.88 mm. The test tubes are installed in a horizontal test section with an effective length of 2 m. In these experiments, condensation temperature is kept constant at 318K. The refrigerant qualities at the test section inlet and outlet are 0.8 and 0.2. Mass flux is varied from 70 kg/(m2s) to 170 kg/(m2s). In a comparison of condensation heat transfer performance, the 1EHT1 tube has the best heat performance followed by the 3EHT tube. Condensing coefficients of the 1EHT1 tube and the 3EHT tube are about 1.45 times and 1.16 times that of the smooth tube, respectively. The experimental results in this study are compared with other experiments conducted by R410A under similar experimental conditions to evaluate the thermal performance.
Review of Enhancement Techniques With Vapor Extraction During Flow Boiling in Microchannels
Authors: Moreira Debora C. , Ribatski Gherhardt , Kandlikar Satish G. 
Published: October 2020

Abstract
Flow boiling heat transfer in microchannels can remove high heat loads from restricted spaces with high heat transfer coefficients and minimum temperature gradients. However, many works still report problems with instabilities, high pressure drop and early critical heat flux, which hinder its possible applications as thermal management solutions. Much comprehension on the phenomena concerning flow boiling heat transfer is still missing, therefore many investigations rely on empirical methods and parametric studies to develop novel configurations of more efficient heat sinks. Nevertheless, investigations involving vapor extraction have successfully addressed all these previously reported issues while also increasing the heat transfer of heat sinks employing flow boiling in microchannels. In this sense, the objective of this review is to identify the main techniques employed for vapor extraction in microchannels-based heat sinks and analyze the physical mechanisms underneath the observed improvements during flow boiling, such that some design guidelines can be drawn. Three main strategies can be identified: passive vapor extraction, active vapor extraction, and membrane-based vapor extraction. All these strategies were able to dissipate heatfluxes higher than 1 kW/cm2, with the best performance achieved by a membrane-based heat sink, followed by active and passive designs. According to the present experimental and numerical data available in the literature, there is still room for improvement.
Insight to Innovation: An Overview of Research Journey of Dr. Satish Kandlikar
Authors: Raghupathi Pruthvik , Owens Alyssa , Steinke Mark , Lin Ting Yu , Kalani Ankit , Moreira Debora , Gonzalez-Hernandez Jose-Luis , Lu Zujie , Banerjee Rupak , Daino Michael , Jaikumar Arvind , Chauhan Aranya , Rishi Aniket , Perez-Raya Isaac , Emery Travis , Guimarães Aguilar Fernando 
Published: October 2020

Abstract
Professor Satish G. Kandlikar has been an outstanding researcher in the field of heat transfer having published some of the most widely cited publications over the last 30 years. Through the years he has co-authored 212 journal paper in various areas of heat transfer. The present paper provides a compressive look at Professor Kandlikar’s research work over the years. The research work has been broadly categorized into 1) flow boiling correlations, 2) fluid flow and heat transfer in microchannels, 3) roughness effect at microscale, 4) pool boiling heat transfer and CHF modeling, 5) surface enhancements for pool boiling, 6) numerical modeling of bubble growth in boiling, 7) modeling liquid-vapor and liquid-liquid interfaces, 8) water transport in PEM fuel cells and 9) infrared imaging to detect breast cancer. The research conducted in each of these areas has produced some landmark findings, some of the most widely used theoretical models and an abundance of high quality experimental data. The focus of this paper is to collate major finding and highlights some of the common themes that guided the research in Professor Kandlikar’s group. This will help the readers gain a comprehensive understanding of each of the areas of study in Professor Kandlikar’s group and place the findings of the paper in a larger context.
Microalgae Harvesting in a Microfluidic Centrifugal Separator for Enhanced Biofuel Production
Authors: Sharma Rohan , Shirley Scott , Farrukh Tahir , Kavosi Mohammadhassan , Kim Myeongsub 
Published: October 2020

Abstract
Biofuel is one of the renewable energy resources alternatives to fossil fuels [1]. Among various sources for biofuels, microalgae provide at least three-orders-of-magnitude higher production rate of biodiesel at a given land area than conventional crop-based methods. However, microalgal biodiesel still suffers from significantly lower harvesting performance, making such a fuel less competitive. To increase the separation performance of microalgae from cultivation solution, we used a spiral microchannel that enables the isolation of biofuel-algae particles from water and contaminants contained in the culturing solution. Our preliminary data show that separation performance in the microfluidic centrifugal separator is as high as 88% within a quick separation time of 30 seconds. To optimize separation performance, multiple parameters of algae behaviors and separation techniques were studied and were manipulated to achieve better performance. We found that changing these factors altered the separation performance by increasing or decreasing flocculation, or “clumping” of the microalgae within the microchannels. The important characteristics of the separator geometry, fluid properties, and environmental conditions on algae separation was found and will be further studied in the forthcoming tests. This introductory study reveals that there is an opportunity to improve the currently low performance of algae separation in centrifugal systems using much smaller designs in size, ensuring a much more efficient algae harvesting.
Effect of Wetted Microtexturing on Friction in Microchannel Flow
Authors: Rabiei Nastaran , Hidrovo Carlos 
Published: October 2020

Abstract
Microchannel flows are widely used in applications where small diffusion length scales are important. However, their inherent dimensional constrain also translates into high pumping power requirements. Inspired by nature, one possible method to reduce the large viscous pressure losses is to introduce textures in a microchannel. Depending on the interaction between the textured surface and the liquid, the microstructures can either be wetted or nonwetted. Less adhesion between solid and liquid in nonwetted state has made it popular in most of the friction reduction studies. However, in the nonwetted state, preventing liquid from penetrating into the grooves under pressurized conditions and the gas-liquid interface acting like a solid boundary open space to consider the wetted state for friction reduction as well. When dealing with the wetted state we should be aware that penetration of the flow inside the grooves can induce the pressure drag alongside the skin drag. Therefore, the wetted state will lead to a trade-off between skin and pressure drag. The aim of this work is to understand how different microtextures affect the total drag in a laminar microchannel flow. Textured microchannels with width-to-depth aspect ratios of 1, 10 and 50 and different width of the land region have been tested. In order to perform correct comparisons, the textured and baseline microchannels are designed to have the same volume. The results show that increasing the aspect ratio of the trenches introduces an extermum point in the hydraulic resistance of the microchannels. The optimum aspect ratio for the tested microchannels is 10, in which the trenches are not wide enough for streamlines to bend inside the trenches and increase the skin drag and they are not highly dense along the microchannel to reveal the negative effect of the pressure drag. On the whole, the hydraulic resistance of the textured channels is higher than the equivalent baseline for all the tested geometries.
Ice Formation due to Condensation of Moist Air on Commercial Wicks
Authors: Stallbaumer Emily , Cernas Adan , Betz Amy , Derby Melanie 
Published: October 2020

Abstract
Heat pipes are valuable heat transfer devices that can be used in space; however, when exposed to the extremely low temperature of space, the working fluid can freeze. Currently, there are different methods to help mitigate freezing effects, including non-condensable gas-charged heat pipes and understanding ice formation on surfaces (e.g., typically surfaces with hydrophobic coatings). However, there is limited research about ice formation on wicks. Different wicking structures may delay freezing or mitigate freezing effects. This paper will investigate ice formation on two surfaces — commercial sintered and grooved wicks. An indoor environmental chamber was used to control ambient air temperature (i.e., 22°C) and relative humidity (i.e., 60% RH) and a Peltier cooler was used to control the surface temperature (i.e., −5°C). The resulting condensation of water onto the surface and then freezing was recorded for an hour and analyzed for the time freezing began on the surface (i.e., ice is initially visible) and the time freezing was complete on the surface. Initial results indicate that the sintered wick begins to freeze first (on average at 10.73 minutes versus 13.66 for the grooved wick) and the freezing front propagates faster (taking on average 10.83 minutes versus 12.44 minutes for the grooved wick). From the analysis, it is seen that the wicking surface structure influences the initial freezing time and the rate the freezing front propagates across the surface. These differences and the causes are investigated in this paper. These differences can, in the future, be exploited to design an optimal freeze-tolerant heat pipe and heat pipe freezing models.