bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heat Transfer Augmentation and Flow Visualization With Delta Winglets in a Tube: A Numerical Approach
Authors: Islam Md. , Guangda Liang , Alam Md. Mahbub 
Published: September 2020

Abstract
In this research, heat transfer and pressure penalty from a circular tube with delta winglets insert are numerically investigated through Computational Fluid Dynamics (CFD) methodology. Numerical analysis with and without vortex generators (VGs) insert in a tube are done for a turbulent air flow, Reynolds number ranging from 6000 to 33000, under constant heat flux condition on the circular tube model surface. In our current research, we employed the shear stress transport (SST) k-omega model. The Nusselt number and friction factor results show the influence of the VGs insert on thermal performance. Effects of different winglet attack angles and blockage ratios on thermal performance enhancement were examined. Thermal performance is enhanced 5.1–30.7% using winglets in a tube. It is observed that small blockage ratio, B = 0.1 performed better than its counterpart of 0.2 and 0.3 for all the Reynolds number and for the same attack angle. The attack angle β = 15° and 30° showed better thermal performance enhancement at lower Re while at higher Re, β = 15° showed better performance. The maximum enhancement obtained for β = 30° and B = 0.1. Winglet vortex generator could create swirling flow when attack angle is 0 or 15°. When attack angle is increased, both swirling flow and longitudinal vortices appeared. At attack angle of 45°, large longitudinal vortices was found.
Experimental Study of a Novel Hydro-Cyclone Apparatus (HCA) Using Flash Evaporation for Desalination and Water Remediation/Purification
Authors: Thyagarajan Ashok , Banerjee Debjyoti , Dhir Vijay 
Published: September 2020

Abstract
A novel apparatus that is capable of dynamic flash evaporation and phase separation using centrifugal flow (i.e., using a Hydro-Cyclone Apparatus/HCA) is explored in this study. The objective of this study is to demonstrate the segregation of phases using the novel apparatus that forms a stable air core at the center from a premixed air-water mixture. The stable air core is then retrieved using an air retrieval tube that is strategically placed in the test section for maximum retrieval of air. For the purpose of this study, a prototype of the apparatus was fabricated using rapid prototyping (3D Printing). Experiments were performed on the flow separator apparatus (HCA) by varying the ratio of the air and water flow rates. A high-speed digital image acquisition apparatus was used in this study for flow visualization in the HCA. Flow maps were generated based on the measurements for flow rates and pressure drops obtained from the experiments conducted in this study. This enabled the measurement of several parameters, which include: the dimensions and morphology of the stable air core, entrainment of the water from the air retrieval tube, etc. The data obtained from this study will be used in the design of experiments for the novel apparatus to demonstrate the feasibility of a compact dynamic flash evaporator and separator system that can be used for various water conservation applications, which include: desalination (e.g., seawater, brackish water, as well as total dissolved solids/ TDS from produced water in oil and gas industries), water remediation (e.g., suspended solids) and purification (e.g., urine purification apparatus/ UPA).
A Reduced Model for Efficient Simulation of Freezing of Water in Large Tanks
Authors: Ramesh Vishal , Terala Shashank , Mazumder Sandip , Matharu Gurpreet , Vaishnav Dhaval , Ali Syed 
Published: September 2020

Abstract
Water-urea mixtures are used in diesel vehicles for exhaust aftertreatment. The liquid mixture, stored in a tank, is susceptible to freezing in cold weather. Depending on weather conditions, the tank size and the liquid fill level, the freezing of the entire liquid may span over a day. Mitigation strategies require understanding of the freezing history. Traditional computational fluid dynamics and heat transfer (CFD/CHT) methodologies are impractical for modeling such freezing processes because of restrictions in the time-step size — typically milliseconds — posed by numerical stability and physical time-scale considerations. The primary constraint for using small time-step sizes is the fine-scale motion generated by natural convection in both the liquid and the gas (unoccupied space). A new model is proposed and demonstrated for efficient prediction of the propagation of the solidification front. In this model, heat transfer due to natural convection is modeled as a diffusive process analogous to how turbulent transport is modeled using an eddy diffusivity and a gradient diffusion model. The model enables use of large time-steps since the fine-scale motions due to natural convection are no longer resolved. The model was validated against experimental data, which were also collected as part of the study. Each experiment collected data at intervals of 6 seconds for a total duration of about 24 hours. Several different tank fill levels were considered, and good agreement with experimental data was noted, especially for shallow fill levels. Large-scale parallel three-dimensional calculations were conducted in a few days of computational time using the proposed model as opposed to a year (projected) of computational time using traditional CFD/CHT models and the same computational resources.
Suppressing the Supercooling Effect of Erythritol by Bubbling for Latent Heat Storage
Authors: Yang Sheng , Shao Xue-Feng , Fan Li-Wu 
Published: September 2020

Abstract
Erythritol, a phase change material (PCM) pertinent to the medium temperature range latent heat storage applications, has the advantages of large storage density, non-toxicity, and high chemical compatibility, but it also suffers from serious supercooling upon cool-down to release the stored heat. In this work, the bubbling method was attempted as an economic and easy way to suppress the supercooling effect of erythritol. At a flow rate of 300 mL/min, N2 bubbles of the size of about 4.4 mm in diameter were continuously introduced into molten erythritol under various subcooling temperatures of ΔTsub = 30, 40, 50, 60, and 95 °C. At the same flow rate, slightly larger bubbles of about 6 mm in diameter were also tested as a contrast case at a single subcooling temperature of ΔTsub = 30°C. The presence of the bubbles was clearly exhibited to successfully facilitate crystallization process of erythritol. It was shown that when ΔTsub = 40, 50, 60, and 95 °C, the introduction of N2 bubbles can reduce the nucleation temperatures Tn by 7.0, 8.2, 10.0 and 5.7°C, respectively, and shorten the crystallization time tc by 19.7%, 14.8%, 13.8%, and 6.4%, respectively. At the lowest subcooling of ΔTsub = 30 °C, erythritol cannot crystallize without the presence of bubbles. The size of the bubbles was found to have negligible effect as the complete crystallization time remains almost the same with the two bubble sizes.
Quasi-Photon Monte Carlo on Radiative Heat Transfer: An Importance Sampling Approach
Authors: Mishra Utkarsh A. , Bansal Ankit 
Published: September 2020

Abstract
The radiative heat transfer phenomenon is a complex process with various events of absorption, emission, and scattering of photon rays. Moreover, the effect of a participating medium adds to the complexity. Existing analytical methods fail to achieve accurate results with all such phenomena. In such cases, brute force algorithms such as the Monte Carlo Ray Tracing (MCRT) or the Photon Monte Carlo (PMC) has gained a lot of importance. But such processes, even if they provide less error than analytical methods, are quite expensive in computation time. Moreover, there are various shortcomings with traditional PMC in effectively including the nature of the participating medium and high variance in results. In this study, a modified PMC is simulated for a one-dimensional medium-surface radiation exchange problem. The medium is taken to be CO (4+) band system, and the behaviour is modelled by Importance Sampling (IS) of the spectrum data for variance reduction. Furthermore, PMC with low-discrepancy sequences like Halton, Sobol, and Faure sequences, known as Quasi-Monte Carlo (QMC), was simulated. QMC proved to be more efficient in reducing variance and computation time. Effective IS included with QMC is observed to have a much smaller variance and is faster as compared to traditional PMC.
Retracted: “Flow Patterns of Liquid-Liquid Two-Phase Flow With Different Viscosities in Microchannels” [ASME 2020 Heat Transfer Summer Conference, Virtual, Online, July 13–15, 2020, Conference Sponsors: Heat Transfer Division, ISBN: 978-0-7918-8370-9, Copyright © 2020 by ASME. Paper No. HT2020-8995, pp. V001T12A012; 6 pages; doi: 10.1115/HT2020-8995]
Authors: ASME  
Published: September 2020

Abstract
This paper was removed from publication at the author’s request. October 2, 2020.
Copyright © 2020 by ASME
Retracted: “Temperature and Velocity Behaviour During Melting of a PCM in a Uniformly Heated Circular Cavity” [ASME 2020 Heat Transfer Summer Conference, Virtual, Online, July 13–15, 2020, Conference Sponsors: Heat Transfer Division, ISBN: 978-0-7918-8370-9, Copyright © 2020 by ASME. Paper No. HT2020-9016, V001T16A003; 7 pages; doi: 10.1115/HT2020-9016]
Authors: ASME  
Published: September 2020

Abstract
This paper was removed from publication at the author’s request. January 15, 2021.
Copyright © 2021 by ASME
Conditional Stability of Direct Contact Steam Condensation
Authors: Alden Zach , Maples Gunnar , Dressler Kristofer , Nellis Gregory , Berson Arganthaël 
Published: September 2020

Abstract
An investigation into the conditional stability of direct contact steam condensation is presented. Direct contact steam condensation systems heat process fluids more effectively than indirect contact heat exchangers because the total energy of the steam is introduced directly into the process fluid, bypassing any resistances associated with having to cross the heat exchanger boundary. In the present work, superheated steam is injected perpendicular to a flow of subcooled liquid water. Conditional stability of direct contact steam condensation stems from the type of fluctuations exhibited by the steam plume structure. Under certain flow conditions the steam plume condenses in the form of a stable conical jet with little to no acoustic noise or resultant pressure fluctuations. However, other conditions cause the steam plume to increase in oscillation intensity, eventually transitioning to an intermittent bubbling structure that results in high-amplitude acoustic noise and large pressure fluctuations in the flow of liquid water. A regime map is presented to establish the process criteria for the onset of instability of condensation. The transitional profile to instability is also presented as an analysis of plume oscillation frequencies and associated pressure oscillations propagating from these fluctuations. It is found that, as the mode of condensation goes unstable, steam plume oscillations increase in intensity and decrease in frequency until the structure collapses into bubbles that provoke strong pressure oscillations in the surrounding water.
A Computational Investigation of Dynamic Stabilization of Rayleigh-Bénard Convection Under System Acceleration
Authors: Topcuoglu Ilker , Kunz Robert F. , Smith Robert W. 
Published: September 2020

Abstract
The static and dynamic stability of Rayleigh-Bénard convection in a rectangular flow domain is computationally investigated. Sinusoidal vertical oscillations are applied to the system to provide dynamic flow stabilization. Stability maps are produced for a range of flow and heating conditions, and are compared to experimental measurements and linear stability analysis predictions from existing literature. Density variation is introduced through: 1) the Boussinesq approximation, 2) a linearly varying temperature dependent equation of state (EOS) and 3) the perfect gas EOS. Significant effects of choice of EOS on dynamic stability are observed. These weakly compressible flows are solved efficiently using an implicit numerical method that has been developed to solve the momentum, continuity, enthalpy and state equations simultaneously in fully coupled fashion. This block coupled system of equations is linearized with Newton’s method, and quadratic convergence is achieved. The details of these numerics are presented.
Effect of Surfactants and Nanoparticle Materials on the Stability and Properties of CuO-Water and Fe3O4-Water Nanofluids
Authors: Mane Nikhil S. , Hemadri Vadiraj 
Published: September 2020

Abstract
The arguments in favor of using nanofluids in thermal applications have been increasing substantially for the last few decades. Nanofluids provide improved performance in heat transfer processes in comparison to their base fluids as a result of their superior thermal properties. Even though nanofluids exhibit better thermal properties, their usage has been limited due to their stability issues. The stability of the nanofluid greatly affects its thermal properties over a period of time. The stability and thermal properties of nanofluids can be affected by parameters like surfactants used and their concentrations, and also on the nanomaterial used in the nanofluid. In this study, surfactant material and nanoparticle material are selected as process variables and for each variable two levels are selected. For surfactant material, Sodium Lauryl Sulfate (SLS) and Cetyl Trimethyl Ammonium Bromide (CTAB) are selected. Surfactant concentration ratios are taken as 1:2 for CuO and 1:4 for Fe3O4 material. Four nanofluid samples are prepared with 0.1% weight of nanoparticles and their stability and properties are studied. The feasibility of turbidity as an indicator for stability is also explored in this work.
The results show that the zeta potential and hydrodynamic characteristics are largely dependent on the surfactant material. Both surfactants show good stability of nanofluids. In-line with earlier observations, it is also observed that the nanoparticle material has a dominant effect on the thermal conductivity of the nanofluids. Comparing the turbidity of the nanofluids to the zeta potential, it is observed that the turbidity measurement gives first-hand information about the stability of nanofluids and can act as an index for stability. But still, more exploration is necessary for this field so a quantitive relation can be established between turbidity and zeta potential of different nanofluid materials and concentrations.
Application of the Neural Networks in Prediction of the Thermal Flow on the Jiu River
Authors: Radulescu Victorita 
Published: September 2020

Abstract
Water temperature is an important parameter that influences the life near watercourses. The physical and chemical properties as the density and viscosity, gas solubility in water and in particular of the oxygen, the kinematics of the micro-biological and chemical phenomena affects not only the aquatic life but also the human life and animals living near the watercourse. In the Jiu river is discharged the water coming from the cooling towers of three thermo-electric power plants placed upstream. According to the recent researches realized by the EU Environmental Commission in Romania until 2050 the average temperature could rise by about 2°C. This paper presents the ability of a “neural networks” model to predict the water temperature in the lower part of the Jiu River. A database realized in over nine years in the measuring station Izbiceni, from the Olt County is used, concerning the water temperature (Tw) and the air temperature (Ta). The developed neural network is structured on five input variables and 9 hidden layers, 7 as sub-input and 2 as output. The stochastic time series is based on the separation of values for water Tw and air Ta in seasonal and daily fluctuations components. The schematic structure of the implemented neural network is presented, for obtaining the short-term and the seasonal components of the temperatures. The contact points are adjusted by the method of reprogramming after a gradient algorithm, in order to minimize the quadratic error between the output results and the relevant observed values. The performance of the neural network is based on estimation the thermal changes of the operation mode. For testing the numerical model, the calculations were performed using only the data recorded in nine years, in order to estimate a forecast for the next two years. The results are very close to the experimental recorded data and the obtained errors are less than 0.5°C. At the end of the paper are presented some results, conclusions and references.
Modeling Nanobubble Interactions and Behavior Using Multiphase Lattice Boltzman Methods
Authors: Cooney Alanna Y. , Carey Van P. 
Published: September 2020

Abstract
A multiphase lattice Boltzmann model is used to explore the presence, evolution, and behavior of nanobubbles. The existence and behavior of nanobubbles has been a recent area of interest since the presence of nanobubbles challenges classical nucleation theory which dictates that bubbles below the critical radius should collapse. Nanobubbles have many areas of interest including cleaning of surfaces, nucleate boiling in microchannels, and nucleation on nanostructured materials. Multiphase Lattice Boltzmann methods (LBM) have been demonstrated to be an effective mesoscale approach to modeling multiphase flows and phase-change processes. These methods provide accurate macroscopic results while accounting for microscopic interactions without invoking an extraordinary computational cost. In this study, an LBM is used to model the evolution of nanobubbles with diameters ranging from 5 to 50 nanometers. LBM results are provided for a variety of real physical conditions that are of interest for exploring nanobubble existence within a nanoporous layer. In addition to the single nanobubble analysis, the effects of bubble interaction with smooth surfaces and within nanostructured surfaces are also presented. The results show that the hydrophilic nature of the surfaces is likely the cause of suppression in the onset of nucleate boiling which is often seen in hydrophilic nanoporous layers. The implications of these results on heat transfer applications including multiphase flows and nucleate boiling in roughened nanostructured surfaces are discussed.
A New Design Methodology of Thermal Barrier Coating (TBC) for Internal Combustion Engines
Authors: Singh Chandra Pratap , Taibani Arif , Krishnan Shankar 
Published: September 2020

Abstract
Currently available Internal combustion (IC) engines contribute 25% of the total world energy consumption. IC engines convert only 40% of the fuel energy into the indicated power[1]. Roughly, 30 percent of heat energy is lost from the combustion chamber to the environment. Interest in the design and development of thermal barrier coating (TBC) is increasing due to an increase in fuel costs and due to the decrease in high quality fuel production[2], [3]. The coating materials with low thermal conductivity and high heat capacity led to problems of high surface temperature, which degrade the volumetric efficiency and an increase in the NOx emission. On the other hand, thin TBC of low thermal conductivity and low heat capacity showed high thermal efficiency. Thin coatings could able to prevent intake air heating with effective resistance during the combustion[4].
However, fundamental relationships between thermal efficiency and thermophysical properties, structure, and durability of TBC still need to be investigated. Few studies suggested that the heat interaction study based on the crank angle position could be the best method to estimate the thermodynamics efficiency than the conventionally calculated heat rejection by the adiabatic engine[5], [6].
This work shows a design methodology to develop a thermal barrier coating (TBC), which can reduce heat loss by maintaining the minimum temperature difference between the surface and the in-cylinder gas temperature. The temperature fluctuation of TBC improves the thermal efficiency of internal combustion (IC) engines by reducing the heat loss to the coolant. This work also investigates the thermophysical behaviour of nearby available material and the applicability as a TBC.
Equilibrium Pressure of Liquid Confined in Nanopores Using Molecular Dynamics Simulations
Authors: Zou An , Maroo Shalabh C. , Gupta Manish 
Published: September 2020

Abstract
Liquid in a confined environment or immediate vicinity of a surface is a ubiquitous phenomenon in natural and technological systems. In such circumstances, the intermolecular forces between the liquid and surface cannot be neglected, and therefore the thermodynamic properties of liquid can be significantly different from the bulk. Here we present an investigation of equilibrium pressure in hydrophilic nanopore connected to bulk using molecular dynamics simulations. With similar bulk pressure, negative pressure was observed in 2 nm pore while positive pressure equilibrated in 4 nm pore. Due to wall attraction, liquid atoms were layered near the wall inside the pore, which dominated the pore pressure, no matter if it was negative or positive.
Numerical Analysis of Thermal Stress Development of Steel Slabs in a Pusher-Type Reheat Furnace
Authors: Zambrano Francisco J. Martinez , Worl Bethany , Li Xiang , Silaen Armin K. , Walla Nicholas , Johnson Kurt , Fabina Lawrence , Zhou Chenn 
Published: September 2020

Abstract
During the steelmaking and hot rolling processes, various defects and cracks appear throughout the steel product. These cracks may initiate and grow throughout the hot rolling process and result in a lower quality of the product than is acceptable. The most energy-intensive part of the hot rolling process is the reheating furnace, where slabs are heated up to a target rolling temperature largely through radiant heat transfer. In the reheat furnace, large stresses may develop due to the thermal gradients within the steel product.
A thermal-stress analysis is proposed based on finite element method (FEM) to study the impacts of charging temperature, slab velocity, and heating rate on stress development as the steel slab travels through an industrial pusher-type reheat furnace. Furnace zone information is taken from a previously validated computational fluid dynamics (CFD) model and applied as thermal boundaries and constraints within the thermal-stress FEM models.
Temperature and stress results were taken at the core, top, bottom, top quarter, and the bottom quarter of the steel slab at different residence times. Moreover, temperature lines and contour plots taken along the length of the slab allow visualization of the gradual development of temperature and identification of the locations corresponding to temperature variations as the slabs move in the furnace. The slab temperature predicted by the FEM model was found valid when compared with industrial data. Stress predictions found similar trends with previously published works as well as evidence of thermal shock in the sub-surface near the beginning of the residence time.