bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimization Techniques for Hybrid Electric Vehicle Analysis Using Advisor
Authors: Markel Tony , Wipke Keith 
Published: November 2021

Abstract
System optimization is an extremely important step in the vehicle design process. Recently the National Renewable Energy Laboratory (NREL), both internally and through its subcontractors, has been actively developing and applying optimization tools to vehicle systems analysis problems associated with hybrid electric vehicles. We are applying both locally- and globally-focused optimization tools to these analysis problems. This paper describes the current status of the tools under development and the application of these tools to a specific problem. The optimization tools evaluated include FMINCON (gradient-based constrained optimization routine included in the MATLAB Optimization Toolbox), DIRECT (non-gradient based optimization routine), Response Surface Approximations and Direct Gradient-based Optimization (commercial routines available in VisualDOC 2.0 from Vanderplaats R&D).
The four optimization algorithms were applied to a simple two-dimensional problem so that the solution methods could be visualized and the relative performance quantified. The tools were then each applied to the optimization of a fuel cell-powered hybrid electric vehicle modeled in ADVISOR 3.1. Both the component sizes and the energy management strategy where included as design variables. The fuel economy was maximized under the constraint that vehicle performance must not be less than its conventional vehicle counterpart. Vehicle and/or component costs were not included in this study but could easily be included if suitable models were identified.
Based on this work, the following conclusions can be drawn:
• The impact of multiple local minimums and a small amount of objective function ‘noise’ (due to necessary state of charge balancing for hybrid vehicles) caused gradient based optimizers to stop before they were able to find design points as good as those found by the non-gradient based DIRECT routine.
• For the fuel cell-powered hybrid electric SUV design problem, several local optimums and one likely global optimum design have been determined. The global optimum is based on 2461 function evaluations. Based on the assumptions in this study, the optimal fuel cell-powered hybrid electric SUV would consist of a 66 kW (net) fuel cell, 107 kW and 16.8 kWh battery pack (twenty-eight 49 Ah modules, 372 volts) and a 126 kW traction motor. The optimal control for this system turned out to be mainly a series thermostat design with some power following capability under peak loads. This vehicle is expected to achieve a City/Highway composite fuel economy of 56.5 mpgge (miles per gallon gasoline equivalent).
Forced Convection Heat Transfer in the Combined Entry Region of Non-Circular Ducts
Authors: Muzychka Y. S. , Yovanovich M. M. 
Published: November 2021

Abstract
A new model for predicting Nusselt numbers in the combined entrance region of non-circular ducts and channels is developed. This model predicts both local and average Nusselt numbers and is valid for both isothermal and isoflux boundary conditions. The model is developed using the asymptotic results for flow past flat plates, thermally developing flows in non-circular ducts, and fully developed flow in non-circular ducts. Through the use of a novel characteristic length, the square root of cross-sectional area, the effect of duct shape on Nusselt number is minimized. Comparisons are made with several existing models for the circular tube and parallel plate channel and with numerical data for several non-circular ducts. Agreement between the proposed model and numerical data is within ± 15 percent or better for most duct shapes.
Nusselt Number in Micro and Nano Channels Under Conditions of Constant Wall Temperature
Authors: Hadjiconstantinou Nicolas G. , Simek Olga 
Published: November 2021

Abstract
We investigate the constant-wall-temperature convective heat-transfer characteristics of a model gaseous flow in two-dimensional micro and nano channels under hydrodynamically and thermally fully developed conditions. Our investigation covers both the slip-flow regime 0 ≤ Kn ≤ 0.1, and most of the transition regime 0.1 &lt; Kn &lt; 10, where Kn, the Knudsen number, is defined as the ratio between the molecular mean free path and the channel height. We use slip-flow theory in the presence of axial heat conduction to calculate the Nusselt number in the range 0 ≤ Kn ≤ 0.2, and a stochastic molecular simulation technique known as the direct simulation Monte Carlo (DSMC) to calculate the Nusselt number in the range 0.02 &lt; Kn &lt; 2. Inclusion of the effects of axial heat conduction in the continuum model is necessary since small-scale internal flows are typically characterized by finite Peclet numbers. Our results show that the slip-flow prediction is in good agreement with the DSMC results for Kn ≤ 0.1, but also remains a good approximation beyond its expected range of applicability. We also show that the Nusselt number decreases monotonically with increasing Knudsen number in the fully accommodating case, and that axial heat conduction increases the Nusselt number. The effect of axial heat conduction is largest at Kn = 0 and is of the order of 10%.
Parametric Study of Conjugate Heat Transfer in a Plate-Fin and Tube Heat Exchanger
Authors: Romero-Méndez Ricardo , Adame Rafael , Sen Mihir 
Published: November 2021

Abstract
A finite element code is used to analyze the conjugate heat transfer over the external side of a single-row plate-fin and tube heat exchanger. The conditions for which the simulations are conducted are similar to those of real plate-fin and tube heat exchangers where both conduction through the fins and convection over them are present. The influence of several parameters on the temperature distribution and local heat transfer is analyzed. From the simulations it is seen that the region of high heat transfer that appears in the leading edge of the fins is the most affected by the finite conductivity of the fin material. There is a decrease of the local heat transfer there when either the fin conductivity or the fin thickness is decreased. This is due to the decrease of the temperature gradient between the fin leading edge and the entering fluid. The effect of increasing the Reynolds number is to reduce the efficiency of the fins. This causes the local Nusselt number not to grow as fast as it would have grown if the fins had infinitely large conductivity. Finally, the effect of the eccentricity of the tube with respect to the fin length is studied. The results illustrate that by moving the tube nearer to the trailing edge of the fin, the area of low heat transfer behind the tube is reduced in size and, at the same time, the temperature gradient between the fin leading edge and the fluid above is reduced causing a reduction of the heat transfer ahead of the tube. This suggests that there is an optimum position of the tube with respect to the fin length.
Numerical Prediction of Flow and Heat Transfer in a Rectangular Channel With a Built-in Circular Tube
Authors: Basu S. , Eswaran V. , Biswas G. 
Published: November 2021

Abstract
Numerical investigation of flow and heat transfer in a rectangular duct with a built-in circular tube has been carried out for a Reynolds number of 1000 and blockage ratio of 0.44. Since the heat transfer in the duct is dictated by the flow structure, the present study is directed toward characterization of the flow structure. To this end, the topological theory shows the promise of becoming a powerful tool for the study of the flow structure. Computations show helical vortex tubes in the wake and existence of horseshoe vortices. The w component of velocity is surprisingly large in front and in the near wake of the tube. The limiting streamlines on the tube and the bottom-plate reveal a complex flow field. The separation lines as well as singularity (saddle and nodal) points have been investigated. The iso-Nusselt number contours and the span-averaged Nusselt number in the flow passage shed light on the heat transfer performance in the duct.
Assessment of Surface Wettability and its Relation to Boiling Phenomena
Authors: Nagai Niro , Carey Van P. 
Published: November 2021

Abstract
The methods for evaluating surface wettability during boiling phenomena are reviewed. Surface wettability strongly affects boiling phenomena such as boiling nucleation, bubble growth and departure, evaporation near the three phase contact line and so on. Consequently, in most regions of boiling curves other than the fully-developed film boiling regime, surface wettability has strong effects on boiling curves. In order to evaluate surface wettability, the equilibrium contact angle measured at room temperature has been commonly used. In this paper, the authors describe evidence that indicates that the equilibrium contact angle is not sufficient to estimate surface wettability as a parameter in boiling phenomena. Some other indexes of surface wettability, such as advancing and receding contact angle, dynamic contact angle, surface energy, and potential energy scale between liquid & solid molecules are reviewed and discussed.
Molecular Dynamics Simulation and Measurement of Contact Angle of Water Droplet on a Platinum Surface
Authors: Kandlikar Satish G. , Maruyama Shigeo , Steinke Mark E. , Kimura Tatsuto 
Published: November 2021

Abstract
A water liquid droplet in contact with a platinum surface was simulated by the molecular dynamics method. Water molecules were modeled by SPC/E and one layer of harmonic molecules represented the platinum surface with the constant temperature heat bath model using the phantom molecules. Here, the water-platinum pair potential developed by Spohr (1989) based on extended Hückel calculations was employed. In the spreading process of the liquid droplet on the platinum surface, the area of contact region between water and platinum expanded just in proportional to the one-third power of time. This spreading rate was clearly in contrast to the case of Lennard-Jones droplet.
The contact angles of water on a platinum surface under saturated conditions are measured. The measurements are made in a vacuum container using de-ionized and degassed water on a clean platinum surface. The equilibrium static, advancing and receding contact angles are measured by changing the orientation of the platinum surface. The droplets of different masses are placed on the horizontal platinum surface. The surface is the inclined to 20, 30 and 40 degrees. The advancing and receding contact angles under these conditions are measured.
Heat Transfer in a MEMS for Determination of Fluid and Flow Characteristics
Authors: Damean Nicolae , Regtien Paul P. L. 
Published: November 2021

Abstract
The paper presents an one-dimensional model for the heat transfer in a limited but significant zone of an actuator-sensor structure for the determination of fluid and flow characteristics. As an essential step for the designing process of this structure, the usefulness of the model in the framework of the structure’s functionality is underlined. The main heat transfer mechanisms are detailed by qualitative and quantitative evaluations. Finally we compare the data obtained by simulating this model with the experimental data. The modeling errors are discussed. The achieved results might be used directly or adapted for various thermal based sensors for flow measurement both in micro and macro world.
A Mixture Theory Model for the Flow Through an Unsaturated Wellbore
Authors: Martins-Costa Maria Laura , Gama Rogério M. Saldanha da 
Published: November 2021

Abstract
This work studies the dynamics of the filling up of a rigid cylindrical porous matrix by a Newtonian fluid, in order to build a preliminary local model for flows through a wellbore, using a mixture theory approach in their modeling. The mixture consists of three overlapping continuous constituents: a solid (porous medium), a liquid and an inert gas, included to account for the compressibility of the mixture as a whole. A set of two nonlinear partial differential equations describes the problem which is approximated by means of a Glimm’s scheme, combined with an operator splitting technique.
Statistics of Mathematical Two-Scale Closure of Momentum, Heat and Charge Transport Problems With Stochastic Orientation of Porous Medium Capillaries
Authors: Travkin V. S. , Hu K. , Catton I. 
Published: November 2021

Abstract
The history of stochastic capillary porous media transport problem treatments almost corresponds to the history of porous media transport developments. Volume Averaging Theory (VAT), shown to be an effective and rigorous approach for study of transport (laminar and turbulent) phenomena, is used to model flow and heat transfer in capillary porous media. VAT based modeling of pore level transport in stochastic capillaries results in two sets of scale governing equations. This work shows how the two scale equations could be solved and how the results could be presented using statistical analysis. We demonstrate that stochastic orientation and diameter of the pores are incorporated in the upper scale simulation procedures. We are treating this problem with conditions of Bi for each pore is in a range when Bi ≳ 0.1 which allows even greater distinction in assessing an each additional differential, integral, or integral-differential term in the VAT equations.
Three-Dimensional CFD Analysis of Gas Mixing in Large Volumes
Authors: Smith Brian L. 
Published: November 2021

Abstract
The paper describes three-dimensional Computational Fluid Dynamics (CFD) calculations undertaken in support of analyses of steam/air mixing which takes place in the drywell volumes of the 1/40th-scale ESBWR1 mock-up facility PANDA under conditions of symmetric steam/air injection and asymmetric outflow. Steady-state simulations for pure steam conditions illustrate how the flow streams mix to ensure balanced outflow conditions to the condensers. A transient calculation has also been performed to examine how air released from solution in the PANDA boiler would ultimately accumulate in the separate condenser units. Results provide a possible explanation for the rundown in performance of one of the condensers which was repeatedly observed in some of the PANDA tests.
Experimental and Numerical Modeling of Gaseous Carbon Dioxide Injecting Into Aqueous Water in Bottle Filler System
Authors: Zheng Y. H. , Amano R. S. 
Published: November 2021

Abstract
An efficient enhancement of the carbonation rate in the bottle filling stage can substantially increase the production in beverage industries. The bottle filling system currently used in most of the manufacturers can still be improved for a better performance of carbonation by designing the injection tube system. This paper reports on an experimental and numerical mass transfer modeling that can simulate the dissolution process of gaseous carbon dioxide into aqueous water in the bottle filler system. In order to establish the operating characteristics of the bottle filler system, an ordinary tap water and pure carbon dioxide were used as the liquid-gas system. The two-phase numerical modeling was developed that can serve as a framework for the continuous improvement of the design of the carbonation process in the bottle filler system. For an optimal design of CO2 injection tube and flow conditions, a computational fluid dynamics (CFD) approach is one of the most power tools. However, since only limited experimental data are available in the open literature to verify the computational results, an experiment study was performed to obtain measurements of CO2 level, temperature, and pressure during the carbonation process in the bottle filled with liquid. Both experimental and numerical studies of various flow condition and different sizes of injection tube are presented in this paper.
An Experimental Study of Liquid Entrainment by Rapid Surface Swelling of Two-Phase Mixture in a Vessel
Authors: Chun Moon-Hyun , Seo Kyong-Won , Kim Hyeng-Kuk 
Published: November 2021

Abstract
An experimental study of liquid entrainment by rapid surface swelling of a two-phase mixture in a vessel has been performed. To investigate the effects of air flow rate and initial water level on the liquid entrainment, a series of experiments have been performed using air and water as working fluid.
A total of 64 experimental liquid entrainment rate data have been obtained for various combinations of the test parameters (i.e., for six different initial water levels and various air flow rates) using two test vessels that have the same height but different inner diameters (0.15 and 0.3m, respectively) for vertical bubbly and churn-turbulent flow conditions.
An empirical correlation for the liquid entrainment rate, E has been developed in terms of the superficial velocity of air, the initial water level, the density of gas, the surface tension, and the gravity. This correlation shows a good agreement with the present experimental data within ±30% over a wide range of flow parameters.
Numerical Simulation of Bubble Dynamics in the Presence of Boron in the Liquid
Authors: Bai Qiang , Dhir V. K. 
Published: November 2021

Abstract
Deposition of boron on the fuel rod cladding during boiling of water containing boron can depress the neutron flux and lead to a decrease in nuclear reactor power output. There is practically little precise information on the temperature field, the gradients of chemical concentration and deposition of boron on the cladding surface. The objective of the present work is to simulate the nucleate boiling process along with velocity, temperature and concentration fields of aqueous boron in the vicinity of the cladding of a fuel rod.
As a first step in solving the complete problem, two-dimensional numerical simulation of a bubble growth on a horizontal surface is considered. A finite difference scheme is used to solve the equations governing conservation of mass, momentum, energy and species concentration. The calculation domain is divided into macro and micro regions. In macro-region, the governing equations are used to calculate the distributions of velocity, temperature, and concentration. The Level Set method is used to capture the evolving liquid-vapor interface. For micro-region, lubrication theory is used, which includes the disjoining pressure in the thin liquid film. The solutions for micro-region and macro-region are matched at the outer edge of the micro-layer. A dilute aqueous Boron solution is considered in the simulation. From numerical simulations, the dynamic change in concentration distribution of boron during the bubble growth shows that the precipitation of boron can occur near the advancing and receding liquid-vapor interface when the ambient boron concentration level is 0.003.
Multiphase Flows With Two Liquid Phases
Authors: Hewitt G. F. 
Published: November 2021

Abstract
Liquid-liquid two-phase flows and liquid-liquid-gas flows occur widely in industrial applications. A particularly important case is in hydrocarbon recovery where such flows occur in subsea pipelines carrying produced fluids (oil, water and natural gas) from subsea wells to on-shore or platform-based processing facilities. The presence of a second liquid phase makes gas-liquid flows even more complex. At higher gas velocities, the liquid phases tend to become inter-dispersed. The dispersions formed can either be of oil drops dispersed in water or water drops dispersed in oil. The transition between one form of dispersion and the other is called phase inversion and is accompanied by anomalous behaviour signalled by a large increase in pressure gradient. A similar inversion phenomenon occurs in liquid-liquid flows at high superficial velocity. In this presentation, recent Imperial College work on this class of flows will be presented. This includes studies of overall parameters such as pressure gradient and phase holdups (the latter being measured using dual energy gamma densitometry) and investigations of local phenomena and parameters (e.g. drop size and interfacial structure) using advanced optical and other techniques. Both steady state and transient flow have been studied. Progress on meeting the formidable challenges of modelling such flows is also reviewed.
Small Diameter Effects on Internal Flow Boiling
Authors: Kendall Gail E. , Griffith Peter , Bergles Arthur E. , Lienhard John H. 
Published: November 2021

Abstract
Since the 1950’s, the research and industrial communities have developed a body of experimental data and set of analytical tools and correlations for two-phase flow and heat transfer in passages having hydraulic diameter greater than 6 mm or so. These tools include flow regime maps, pressure drop and heat transfer correlations, and critical heat flux limits, as well as strategies for robust thermal management of HVAC systems, electronics, and nuclear power plants. Designers of small systems with thermal management by phase change will need analogous tools to predict and optimize thermal behavior in the mesoscale and smaller sizes. Such systems include a wide range of devices for computation, measurement, and actuation in environments that range from office space to outer space and living systems. This paper examines important proceses that must be considered when channel diameters decrease, including flow distribution issues in single, parallel, and split flows; flow instability in parallel passages; manufacturing tolerances effects; nucleation processes; and wall conductance effects. The discussion focuses on engineering issues for the design of practical systems.
Dynamics of the Flows in Micro-Channels of a Capillary Pumped Loop (CPL) Evaporator
Authors: Lee Hyoung-In , Cho Hye-Jung , Song In-Seob , Lee Ju-Hyeong 
Published: November 2021

Abstract
Cooling of electronic components is often limited by space availability and power consumption. Capillary-pumped loops (CPL) are utilized to achieve a coolant circulation via self-activated capillarity (Faghri, 1995). However, CPL is extremely unstable due to a nonlinear feedback among capillarity, viscous force, and heat transfer. Conventional refrigeration theories, which usually allow a larger pressure jump due to an external pumping, failed to explain the CPL cycle.
The dynamics of a flow through a CPL cooling cycle is investigated with a particular attention to the flow in the micro-channels. Full numerical approaches, by which multi-component multi-phase flows are solved, tend to obscure the engineers from identifying outstanding design parameters. Instead, one here adopts several simplified semi-analyitic approaches, namely, models based on single-phase flows with discrete zones of heating and cooling. The analytical and numerical results could explain some general tendencies in the dynamical features like dry-out and flooding. However, the problem still requires closer and more realistic modeling.