bluuebunny/crossref_metadata_2025_split huggingface dataset:
High Temperature Microscale Reactor Analysis Using a Counterflow Heat Exchanger Model
Authors: Peterson Richard B. , Vanderhoff John A. 
Published: November 2021

Abstract
A microscale reactor model, with axial conduction and radiation heat loss, has been developed for predicting the thermal performance of high temperature systems. The model considers: 1.) flow loss due to non-unity effectiveness, 2.) thermal conduction along the axial direction, and 3.) radiation surface loss to the environment. A system of three coupled differential equations were developed where two of the equations modeled the temperature variation in the fluid streams and the third equation gave the temperature of the wall. The wall equation contained a highly non-linear term linked to radiation surface loss. This study is unique in several ways. First, the boundary conditions for the problem modeled a micro reactor attached to a substrate at ambient temperature while the hot end was free to assume a wall temperature half way between the two fluid temperatures. Next, surface radiation was treated explicitly as a heat loss term. At elevated temperatures, the overall thermal performance of the micro reactor was significantly impacted by this loss mechanism. Finally, an implicit method is described capable of solving the non-linear coupled differential equations. The results of the study are presented in the form of normalized total heat loss curves for each of the three loss mechanisms. A scaling study is presented showing what contributions to heat loss are important as the characteristic length scale of the device is reduced. This study demonstrates that both conduction and surface radiation losses are significant in high temperature micro reactors. Furthermore, the heat loss (in normalized form) by radiation is significant for larger scale devices but the ultimate size limits for a micro reactor will be governed by conduction losses through the structure. For high temperature micro reactor technology to be practical, this study demonstrates that devices must be designed with low thermal conductivity materials, high aspect ratio geometries, and low effective surface emissivities.
Feedback Thermal Control in Microscale Heat Transport
Authors: Tzou D. Y. , Monda E. 
Published: November 2021

Abstract
Feedback thermal control in ultrafast heating processes is studied in this work. The emphasis is placed on the desirable rate of heating that avoids the thermal instability developed during the short-time transient. Physical parameters characterizing the thermal instability and effects of thermalization and relaxation on the desirable heating rate are identified in the ultrafast process of heat transport.
Scanning Thermal Microscopy of Carbon Nanotubes
Authors: Shi Li , Plyasunov Sergei , Bachtold Adrian , McEuen Paul L. , Majumdar Arunava 
Published: November 2021

Abstract
This paper reports the use of scanning thermal microscopy (SThM) for studying heat dissipation and phonon transport in nanoelectronic circuits consisting of carbon nanotubes (CNs). Thermally designed and batch fabricated SThM probes were used to resolve the phonon temperature distribution in the CN circuits with a spatial resolution of 50 nm. Heat dissipation at poor metal-CN contacts could be readily found by the thermal imaging technique. Important questions regarding energy transport in nanoelectronic circuits, such as where is heat dissipated, whether the electrons and phonons are in equilibrium, how phonons are transported, and what are the effects of mechanical deformation on the transport and dissipation properties, are addressed in this work.
Mass/Heat Transfer in Rotating Dimpled Turbine-Blade Coolant Passages
Authors: Acharya Sumanta , Zhou Fuguo 
Published: November 2021

Abstract
Naphthalene sublimation measurements are made in a rotating dimpled square coolant flow passage with radially-outward flow. The coolant flow passage represents a typical internal cooling channel of a turbine blade. The dimples are in the form of hemispherical depressions and are arranged in staggered rows. In the present study, only the leading and trailing surfaces are dimpled. Measurements are made at a Reynolds number of 7,000 and 21,000 and for Rotation number of 0.2. The measurements indicate that dimples enhance surface mass transfer by a factor of about two compared to a smooth surface. With rotation, the trailing wall mass transfer is increased to nearly twice that of the leading wall mass transfer. Peak mass transfer occurs immediately downstream of the dimples, while the minimum mass transfer occurs in the dimple region itself. Higher mass transfer is also observed along the lateral edges of the dimple. The locations of the Sherwood number peaks suggest the existence of streamwise vortical structures generated from the leading and lateral edges of the dimples.
Non-Linear Numerical Analysis in Transient Cutting Tool Temperatures
Authors: Jen Tien-Chien , Gutierrez Gustavo , Eapen Sunil 
Published: November 2021

Abstract
A numerical analysis, using a control volume approach, is conducted to study the transient cutting tool temperatures with temperature dependent thermal properties. With temperature dependent thermal properties, the governing conduction equation is non-linear and thus, the standard analytical solutions are no longer valid. In any cutting processes, the temperature distribution is intrinsically three-dimensional and very steep temperature gradient may be generated in the vicinity of the tool-chip interface. In this region, where the maximum temperature occurs, the effect of variable thermal properties may become important. The full three-dimensional non-linear transient heat conduction equation is solved numerically to study these non-linear effects on cutting tool temperatures. The extremely small size of the heat input zone (tool-chip interface), relative to the tool insert rake surface area, requires the mesh to be dense enough in order to obtain accurate solutions. This usually requires very intensive computational efforts. Due to the size of the discretized domain, an efficient algorithm is desirable in the solution of the problem. Four different iterative schemes are explored, and an optimized numerical scheme is chosen to significantly reduce the required computing time. This numerical model can be used for process development in an industrial setting. The effect of two different heat flux input profiles, a spatially uniform plane heat flux and a spatially non-uniform plane heat flux at the tool-chip interface, on the tool temperatures are also investigated in the present study. Some recommendations are given regarding the condition when these non-linear effects can not be ignored.
Numerical Simulation of Condensation on a Capillary Grooved Structure
Authors: Zhang Yuwen , Faghri Amir 
Published: November 2021

Abstract
Condensation in a capillary grooved structure is investigated using the Volume of Fluid (VOF) model. The governing equations are written in a generalized form and are applicable to both liquid and vapor phases. Condensation on the fin top and at the meniscus is modeled by introducing additional source terms in the continuity, VOF, and energy equations. The effects of temperature drop, contact angle, surface tension, and fin thickness on the condensation heat transfer are investigated.
On the Potential for Homogeneous Nucleation in Aqueous Salt Solutions at Elevated Temperatures and Pressures
Authors: Smith Kenneth A. , Hodes Marc , Griffith Peter 
Published: November 2021

Abstract
Recent studies have experimentally and theoretically examined the rate of salt deposition by natural convection on a cylinder heated above the solubility temperature corresponding to the concentration of salt in the surrounding solution at conditions typical of the Supercritical Water Oxidation (SCWO) process (Hodes et al., 2000A; Hodes, 1998). The total deposition rate of salt on the cylinder is the sum of the rates of deposition at the salt layer-solution interface (SLSI) formed on the cylinder and within the porous salt layer. The rate of deposition at the SLSI can not be accurately computed without determining whether or not salt nucleates homogeneously in the adjacent (natural convective) boundary layer. A methodology to determine whether or not homogeneous nucleation in the boundary layer is possible is presented here. This is accomplished by computing the temperature and concentration profiles in the boundary layer under the assumption that homogeneous nucleation does not occur. If, under this assumption, supersaturation does not occur, homogeneous nucleation is impossible. If supersaturation is present, homogeneous nucleation may or may not occur depending on the amount of metastability the solution can tolerate. It is shown that the Lewis number is the critical property in determining whether or not homogeneous nucleation is possible and a simple formula is developed to predict the Lewis number below which homogeneous nucleation is impossible for a given solubility boundary and set of operating conditions.
Heat Transfer Correlations for Air-Water Two-Phase Flow of Different Flow Patterns in a Horizontal Pipe
Authors: Kim Dongwoo , Kim Jae-yong , Ghajar Afshin J. , Dougherty Ronald L. 
Published: November 2021

Abstract
New heat transfer correlations were developed for two-phase heat transfer in a horizontal pipe for different flow patterns. Flow patterns were observed in a transparent circular pipe (2.54 cm I.D. and L/D = 96) using an air/water mixture. Visual identification of the flow patterns was supplemented with photographic data, and the results were plotted on the flow regime map proposed by Taitel and Dukler and agreed quite well with each other. A two-phase heat transfer experimental setup was built for this study and a total of 150 two-phase heat transfer data with different flow patterns were obtained under a uniform wall heat flux boundary condition. For these data, the superficial Reynolds number ranged from 640 to 35,500 for the liquid and from 540 to 21,200 for the gas. Our previously developed robust two-phase heat transfer correlation for a vertical with modified constants predicted the horizontal pipe air-water heat transfer experimental data with good accuracy. Overall the proposed correlations predicted the data with a mean deviation of 1.0% and an rms deviation of 12%.
Metal Monoxide Diagnostics in Particle Synthesis Flames
Authors: Chen Yijia , Colibaba-Evulet Andrei , Glumac Nick G. 
Published: November 2021

Abstract
Recent measurements of metal monoxides in powder producing flames are reviewed and discussed. While the mole fraction profiles of species such as SiO, AlO, and TiO can in principle be used to infer useful information about metalorganic decomposition in flames, the dominant features of these profiles appear to be due to the partial pressure of the solid product. Most monoxides do serve as good markers of the flame zone, but are no better than emission profiles of key excited intermediates. Monoxide profiles may, however, be of significant value in validating future comprehensive multiphase models of the synthesis process.
The Mathematical Modeling of Utility Boilers at IST
Authors: Coelho P. J. , Azevedo J. L. T. , Coelho L. M. R. 
Published: November 2021

Abstract
The mathematical modeling of utility boilers is a difficult problem due to the multiplicity of physical phenomena involved and to the interaction between different phenomena. However, reliable models are extremely useful since they can be used to design new equipment, and to optimize and retrofit units in operation. In this paper a survey of the work carried out at Institute superior Técnico (IST) in Lisbon is reported. Only the work based on comprehensive models, i.e., those accounting for all the relevant physical phenomena taking place in the combustion chamber is addressed. The models employed are briefly outlined. Then, four examples of application are given, two of them for coal-fired boilers where the effect of low NOx burners and coal over coal reburning is investigated, and the other two for oil-fired boilers where parallelization of the code and simulation of the convection chamber are reported.
Structural Acoustic Optimization of a Composite Cylindrical Shell Using FEM/BEM
Authors: Johnson W. M. , Cunefare K. A. 
Published: November 2021

Abstract
A finite element/boundary element design tool is used to perform a structural acoustic optimization on an eight-ply graphite epoxy cylindrical shell. The shell is subject to two external monopole sources vibrating at a single frequency. The goal of the optimization is the minimization of the sum of the squared pressure amplitudes within the enclosed acoustic cavity. The ply angles serve as the design variables in optimization. The optimal design was obtained after 15 iterations with a 2 dB reduction in the average interior sound pressure level. The ply angle orientation shifted from an initially symmetric lay-up to an unsymmetric lay-up in the final design.
Micro-Scale Acoustic Streaming Pump Performance Characteristics
Authors: Frampton Kenneth D. , Martin Shawn E. 
Published: November 2021

Abstract
Acoustic streaming theory, applied to micro-scale pumps is presented. A mathematical model based on streaming equations and Mason’s model [9] of the piezoelectric transducer is described. Using this model, the effect of geometric scaling, frequency variation, and excitation amplitude on head and flow rate are examined. The significance of high body forces in the AC boundary layer are demonstrated, along with their effect on mass flow rates for small geometries. It is shown that flow velocities are inversely proportional to the flow tube diameter for small sizes. Experimental data for a macro-scale pump is provided and used to corroborate the static head versus excitation relationship predicted by the model. Compression wave acoustic streaming pumps are shown to have potential viability for micro-scale applications.
Silicon Micromachined Ultrasonic Transducers
Authors: Khuri-Yakub Butrus T. , Cheng Ching-Hsiang , Degertekin Fahrettin-Levent , Ergun Sanli , Hansen Sean , Jin Xue-Cheng , Oralkan Omer 
Published: November 2021

Abstract
This paper reviews capacitor micromachined ultrasonic transducers (cMUTs). Transducers for air-borne and immersion applications are made from parallel-plate capacitors whose dimensions are controlled through traditional integrated circuit manufacturing methods. Transducers for airborne ultrasound applications have been operated in the frequency range of 0.1–11 MHz, while immersion transducers have been operated in the frequency range of 1–20 MHz. The Mason model is used to represent the cMUT and highlight the important parameters in the design of both airborne and immersion transducers. Theory is used to compare the dynamic range and the bandwidth of the cMUTs to piezoelectric transducers. It is seen that cMUTs perform at least as well if not better than piezoelectric transducers. Examples of single-element transducers, linear-array transducers, and two-dimensional arrays of transducers will be presented.
Flow Noise Predictions for Automotive Air Rush Noise
Authors: Howell James , Humbad Niranjan G. , Hargrove Jeff , Porada Robert A. 
Published: November 2021

Abstract
Noise from automotive air handling systems is an important issue for driver comfort. This study was undertaken to quantify the noise from the air handling system and to develop a predictive model for the noise level and spectrum at the drivers right ear location. Tests were conducted on six vehicles to develop the predictive model and then four more vehicles were tested and used to verify the prediction model. All vehicles tested were production level designs ranging from small economy cars to large luxury trucks. The study shows that the noise generated by the air handling system can be modeled with the parameters of static pressure across the blower (ΔP) and system air flow rate (Q). When the measured noise levels were compared to the predicted noise levels, there was a mean error of −0.03 dBA with a standard deviation of 1.31 dBA for all vehicles and for various modes of operation. This model can be used in the early stages of design using CFD/CAE analysis, or in evaluating the effects of design changes on the sound pressure level and spectrum.
Cepstral Analysis Applied to Identification of Longitudinal Vibration in Timber Piles
Authors: Pardue Sally J. , Renfro Michael W. , Ramsagar Prasanna 
Published: November 2021

Abstract
A method for field measurement of timber pile length in bridge foundations is possible by determining the natural frequency spacing between consecutive resonant peaks in the longitudinal frequency response function (FRF) as well as experimental determination of the longitudinal wave speed. The measurement procedure relies on vibration modes excited through the attachment of small actuators driven with random input and the recorded response of attached accelerometers.
The identification of natural frequencies in timber piles is complicated by the inhomogeneous nature of wood and the location of measurement points at possible longitudinal nodes along the pile. Missing peaks and corrupted spectrums are common in the experimental data collected during the testing of timber piles. A form of cepstral analysis using the FRF shows promise towards overcoming some of the inherent difficulties in identifying the natural frequency spacing between resonant peaks in the spectrum.
The details of the signal processing and natural frequency spacing identification are presented and demonstrated on a laboratory aluminum bar and typical timber pile data.
New Algorithms to Improve Noise Source Location Using a Microphone Array
Authors: Darvennes Corinne M. , Bhatt Tarun K. 
Published: November 2021

Abstract
Several algorithms are presented to improve noise source location using a microphone array. The estimation of the source location is essentially a two step process: first, time delays of arrivals (TDOA’s) are calculated using the unwrapped phase (UP) method; then the TDOA estimates are used to determine the coordinates of the source. The first algorithm was developed to calculate TDOA’s automatically by removing the data points with low coherence from the unwrapped phase and by using a delay error rather than a mean square error to choose the best distance estimate. A simplex algorithm was then implemented to evaluate source coordinates from the TDOA’s. Finally, a pruning algorithm was devised to remove unreliable data from the source coordinate calculations. Experimental data is presented to illustrate the use and benefits of these algorithms.
Comparison of Static and Dynamic Stiffness for Beams Undergoing Flexural and Torsional Loading With an Intermediate Mass
Authors: Garcia Arnoldo , Lumsdaine Arnold , Yao Ying X. 
Published: November 2021

Abstract
Many studies have been performed to analyze the natural frequency of beams undergoing both flexural and torsional loading. For example, Adam (1999) analyzed a beam with open cross-sections under forced vibration. Although the exact natural frequency equation is available in literature (Lumsdaine et al), to the authors’ knowledge, a beam with an intermediate mass and support has not been considered. The models are then compared with an approximate closed form solution for the natural frequency. The closed form equation is developed using energy methods. Results show that the closed form equation is within 2% percent when compared to the transcendental natural frequency equation.
A Study on Gradient Polymer Materials Used as Damping Coatings: Focus on Free Damping Coatings
Authors: Remillat C. , Tomlinson G. R. 
Published: November 2021

Abstract
This paper discusses the damping capabilities of polymer materials with mechanical characteristics which vary through the thickness. The case studied is that of a beam coated with a single layer of this material, which can be classified as a free layer damping coating. A simple mechanical model of the system is proposed, together with a suitable modelling of the gradient material. Simulation results based on realistic cases are presented for different types of distribution through the thickness and their damping performance is assessed.
On the Exploitation of Thermoelectric Coupling for Characterization of Inclusions in Metals
Authors: Nayfeh Adnan H. , Carreon Hector , Nagy Peter B. 
Published: November 2021

Abstract
It was recently discovered that inclusions and other types of inhomogeneities can be nondestructively detected by thermoelectric measurements in an entirely non-contact way by using high-sensitivity magnetometers to sense the weak thermoelectric currents around the affected region when the specimen is subjected to directional heating or cooling. This paper presents theoretical models capable of predicting the magnetic field produced by thermoelectric currents around inclusions under external thermal excitation. We investigated how the magnetic signal to be detected depends on (i) the relevant physical properties of the host and the inclusion, (ii) the size of the inclusion, (iii) the polarization of the magnetometer, (iv) the lift-off distance of the magnetometer from the specimen, and the (v) direction and (vi) strength of the external heating or cooling applied to the specimen. The presented analytical model is numerically evaluated for comparison to experimental results that were obtained by measuring the magnetic field produced by thermoelectric currents around surface-breaking spherical tin inclusions in copper under external thermal excitation for different lift-off distances between the sensor and the surface of the specimen. The diameter of the inclusions and the lift-off distance varied from 2.4 to 12.7 mm and from 12 to 20 mm, respectively. A fairly modest 0.7 °C/cm temperature gradient in the specimen produced peak magnetic flux densities ranging from 1 to 250 nT, that could be easily measured by a commercial fluxgate magnetometer. The experimental results were found to be in very good agreement with our analytical predictions.
Understanding Stage Matching of a High-Efficiency Multi-Stage Centrifugal Gas Compressor
Authors: Cave Michael J. , David Tim 
Published: November 2021

Abstract
A series of closed loop development tests were conducted on a new high-efficiency, multi-stage gas compressor. Using the test data and a 1-D compressor analysis software program, stage characteristics were modeled for each of the six stages. Overall stage results from the 1-D model were compared to development test data to validate the model. Once the model was validated, it was used to understand stage-to-stage matching at design and off-design conditions.
Hybrid System Stability and Capacitive Shunting of Piezoelectric Stiffness
Authors: Kurdila Andrew J. , Feng Yunfei , Lesieutre George A. 
Published: November 2021

Abstract
Recent research demonstrated that an actively-switched capacitive shunt circuit across a piezoceramic stiffness element can provide the basis for a frequency-tunable solid state vibration absorber. From a theoretical standpoint, the stability characteristics of such a design are amenable to conventional mechanical systems analysis when the shunt circuit operates in quasi-steady manner. However, when active tracking of a disturbance is desired to enhance broadband disturbance attenuation, the conditions for closed loop stability of the electromechanical system are not clear. In the present research, a simplified mechanical model of a switch-shunted piezoceramic was first developed. This model was amenable to study as a hybrid or Witsenhausen switching system. Using the method of multiple Lyapunov functions, the simplified model was shown to be unstable for some switching strategies. Subsequently, a coupled electromechanical model was developed and used as the basis for numerical performance simulation. In this model, all switching strategies evaluated resulted in stable systems, although some exhibited considerably higher effective damping than others. These results indicate the importance of retaining electrical states in dynamical models of switched piezoelectric systems.