bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Measurement of Transient 2-D Profiles of Velocity and Fuel Concentration Over Liquids
Authors: Ito Akihiko , Narumi Akira , Konishi Tadashi , Tashtoush Gassan , Saito Kozo , Cremers Clifford J. 
Published: March 2022

Abstract
We recently developed two different optical techniques in order to simultaneously measure transient 2-D profiles of velocity, temperature and fuel concentration that were generated by a spreading flame over liquid fuels. One technique employs a particle-track system combined with a laser-sheet system (PTLS) and a high speed camera, while the other technique employs a dual wavelength holographic interferometry (DWHI). The PTLS system revealed transient 2-D profiles of flame induced flow, while DWHI revealed 2-D profiles of fuel concentration over liquids. In this paper we present a series of velocity profiles for a pulsating flame spread over propanol and concentration profiles for gaseous propanol determined with PTLS and DWHI respectively. Other researchers have predicted the formation of small twin circulations, one a gas-phase circulation just ahead of the flame’s leading edge, and the other a small liquid circulation just underneath the gas-phase circulation. Our PTLS results confirmed these predictions, i.e., the formation of 5–10 millimeter diameter circulation in the gas phase and an accompanying approximately 20 millimeter diameter liquid circulation. Based on these data, we offer a phenomenological explanation of the mechanism of pulsating flame spread. In addition, we show that DWHI is a very promising technique for measuring transient fuel-concentration profiles over liquids.
Moving Matrix Reactor for Biomass and Organic Waste Gasification
Authors: Goldman Y. , Timnat Y. M. , Arfi P. 
Published: March 2022

Abstract
An organic waste gasification scheme based on the use of a new reactor concept has been investigated. The gasifier includes an intermediate heat carrier matrix, moving opposite to the gas stream. A technical embodiment of the concept is presented and a computational model for the description of the process in the reactor is developed. The first stage of the experimental study demonstrates the possibility of a two-phase counter-flow concept as a mean of providing super-adiabatic conditions, which are expected to enhance weak exothermic reactions and endothermic gasification reactions in the reforming zone. To perform a parametric study, the mathematical model was run in a simplified case with a single source of reaction-liberated energy. Temperature profiles were obtained and from our first predictive results, one can conclude that there is a broad range of combinations of gas velocity, matrix velocity and oxygen addition to control the gasification process. A feeding system and atomization into the moving matrix is currently developed to feed the reactor with an organic solid fuel downstream of the steam addition. The next stage of the research will allow us to test the complete gasification scheme with a selected biomass material. The simulation model will permit to evaluate anticipated performance of the moving matrix reactor and thus optimization of the process.
A Periodic Transient Method Using Liquid Crystals for the Measurement of Local Heat Transfer Coefficients
Authors: Baughn James W. , Anderson Michael R. , Mayhew James E. , Butler Robert J. 
Published: March 2022

Abstract
A new periodic transient method for the measurement of local heat transfer coefficients is described. In this method, the freestream temperature is periodically heated while the local surface temperature fluctuation is measured. The local heat transfer coefficient can be determined from the frequency, the ratio of the surface temperature fluctuation to the free stream temperature fluctuation and the wall thermal properties. Measurements on a Plexiglas flat plate with a laminar boundary layer are presented as a demonstration of this method. For this demonstration the free stream is electrically heated using a fine wire cloth. The surface temperature fluctuation is measured using liquid crystals with a hue analysis technique. The results show that this is a viable method for measuring local heat transfer coefficients. Its advantages are that it approximates a uniform temperature thermal boundary condition and it is not necessary to control or measure the initial wall temperature.
Thin Film Resistance Heaters for High Heat Flux Jet-Array Cooling Experiments
Authors: Younis Hesham F. , Dahbura Rudy S. , Lienhard John H. 
Published: March 2022

Abstract
This paper reports on efforts to use plasma-sprayed metal films as resistance heaters for generating heat fluxes on the order of 10 MW/m2. These heaters are intended for use in testing a jet-array cooling module designed for removing extremely high heat fluxes. Convective cooling of the rear surface of an externally heated metal faceplate is provided by an array of impinging water jets. The metal film heater is electrically isolated from the faceplate by a plasma-sprayed ceramic film beneath it. Heat fluxes have reached 7.2 MW/m2 over an area of 10.3 cm2. Design and fabrication issues associated with these heaters include physical property differences between sprayed and bulk materials, thickness variations in the sprayed materials, high thermal resistance associated with the ceramic films, and fracture of the heater film at high temperatures.
Natural Convection From Vertical Helical Coils in a Cylindrical Enclosure
Authors: Taherian Hessam , Allen Peter L. 
Published: March 2022

Abstract
Experiments were conducted to investigate natural convection heat transfer from single enclosed helical coils in a vertical orientation. Coils having different diameter, pitch, and tube diameters were placed inside a cylindrical shell of fixed height and diameter, to form a natural convection shell-and-coil heat exchanger. Effects of tube diameter, coil surface area and coil pitch on heat transfer coefficient were studied. Nu-Ra correlations were presented based on different characteristic lengths. The data was correlated well by NuDhx = 0.002RaDhx0.630 using heat exchanger hydraulic diameter as the characteristic length.
Quantitative Flow Visualization Using a Water Table
Authors: Rani Sarma L. , Wooldridge Margaret S. 
Published: March 2022

Abstract
The current work describes the development of a new, non-intrusive optical method for the evaluation of water heights along a gravity wave in shooting water flows in an experimental water table facility. The technique involves superimposing alternating dark and clear mechanical fringes on the water flow. Images of the fringe deviation patterns formed due to the gravity waves are obtained. The images are analyzed to determine the angles and the lengths of fringe deviations, which are related to the local flow heights. It is proposed that the deviations can be simulated using flat-topped optical prisms oriented along the direction of the gravity wave. The height of such a prism corresponds to the local water height. In the present work, shooting flows past a wedge profile for a zero angle of attack have been studied. The variation of flow field heights along a gravity wave has been obtained by the optical technique and by a conventional intrusive depth-gauge technique. The results are in good agreement.
A Generalized Asymptotic Theory of Mixed Convection Boundary Layers
Authors: Chen Michael M. , Paolucci Samuel 
Published: March 2022

Abstract
We propose the use of generalized boundary layer equations and governing dimensionless parameters for mixed convection of either the forced-convection-dominated case or the free-convection-dominated case. Such equations are derived by considering the asymptotic limits of high Reynolds number or high Peclet number, and high Rayleigh number or high Boussinesq number, with small or large Prandtl and Richardson numbers as the case may be. Here, we illustrate the ideas in the forced-convection-dominated case in the small Prandtl number limit. We show that the exercise provides a more convenient format for displaying the results of computational or experimental investigations of mixed convection, leading to more general quantitative results as long as the asymptotic conditions are met, and possibly general qualitative results even when the asymptotic conditions are not strictly satisfied. In addition the contributions of normal and tangential buoyancy are also clearly separated.
Simulations of Three-Dimensional Flow and Augmented Heat Transfer in a Symmetrically Grooved Channel With Constant Temperature Walls
Authors: Greiner M. , Faulkner R. J. , Wirtz R. A. , Fischer P. F. 
Published: March 2022

Abstract
Direct numerical simulations of three-dimensional flow and augmented convection in a channel with symmetric, transverse grooves on two opposite walls are performed using the spectral element technique. The flow is driven by a constant pressure gradient. A method employing an exponentially decaying temperature scale is developed and used to calculate the fully developed heat transfer coefficient for constant temperature boundary conditions. Results are presented for the Reynolds number range 180 &lt; Re &lt; 1175.
A series of flow transitions is observed as the Reynolds number is increased, from steady two-dimensional flow, to traveling two and three-dimensional wave structures, and finally to three-dimensional mixing. Periodic ejection of slow moving fluid from the grooves causes significant flow rate unsteadiness. Three-dimensional simulations predict friction factor and Nusselt number values to within 20% of measured values over the narrow Reynolds number range where overlapping data exists. Two-dimensional simulations are found to be inadequate to calculate transport in this channel for Re &gt; 400.
Experimental Analysis of Thermal Instability in Natural Convection Inside Open-Ended Cavities With Uniform Heat Flux on Horizontal Walls
Authors: Manca Oronzio , Morrone Biagio , Nardini Sergio , Savarese Salvatore 
Published: March 2022

Abstract
An experimental investigation of air natural convection between heated parallel plates has been carried out by the visualization of the flow and the measurement of air temperature. Grashof numbers, based on the gap between the plates and the longitudinal aspect ratio (L/b), varied in the 3.8·102–1.1·105 range. The investigated distance between the plates, b, were 20.00, 32.25 and 40.00 mm, corresponding to aspect ratios L/b of 20, 12.4 and 10 and plate width/gap between the plates ratio of 22.5, 14 and 11.25. The Ohmic heat fluxes have been changed in the 60–240 W/m2 range. Furthermore, three heating modes have been tested in order to analyze their peculiar patterns and the onset of secondary motions. The typical main flow pattern resembles a C shape (C-loop). In fact, the flow penetrates inside the channel close to the leading edge of the lower plate and exits from the upper part, by reversing its motion inside the channel. The flow visualization shows that secondary flows add to the C-loop main flow, when the lower plate is heated. Such secondary structures start in the form of thermals and, then, they change into longitudinal vortex, whereas in the upper region of the open-ended cavity a chaotic motion is detected. The existence of these structures is confirmed by the measurement of istantaneous temperature values. They show that the greater the Grashof number the more chaotic the turbulent flow in the outflow region of the C-loop, when the lower plate is heated and the upper plate is unheated.
Application of a 3D Numerical Model for Shell-and-Tube Heat Exchanger Simulation and Comparison With Other Methods
Authors: Prithiviraj M. , Andrews M. J. 
Published: March 2022

Abstract
This paper describes a three-dimensional numerical model for simulation of turbulent flow and heat transfer inside shell-and-tube heat exchangers. A SIMPLE (Patankar and Spalding, 1972) type solution algorithm is used on a colocated grid. The simulation of shell-and-tube heat exchangers is based on a distributed resistance method that uses a modified two equation k-ε turbulence model. Volume porosities and non-homogeneous surface permeabilities account for tubes, nozzles, and an arbitrary arrangement of baffles. Sub-models are used for shellside pressure drop by tubes, turbulence generation and dissipation by tubes, baffle-shell and baffle-tube leakage, shellside and tubeside heat transfer. These sub-models use parameters that have not been altered from their published values. The details of the sub-models are described in detail by Prithiviraj and Andrews (1995, 1996).
The numerical model was validated by comparison with experimental data for shell-and-tube heat exchangers from University of Delaware (Bell, 1963) and Argonne National Labs (Halle et al., 1984) by Prithiviraj and Andrews (1996). Good agreement was obtained between the computations and experiments. This paper uses the model to simulate flow and heat transfer in Full Bundle and No Tubes In The Window (NTIW) bundle types (In the NTIW design, tubes in the window region are removed). The effect of shell type and bundle type on the pressure drop and heat transfer is examined. The performance of the numerical model is compared with the methods of Bell (1981), Kern (1950), and Donohue (1949), for a range of shellside Reynolds numbers. It is shown that at the price of an increased computation cost, the three-dimensional numerical model yields better predictions than the above methods, along with detailed flow, turbulence, and temperature fields.
High Resolution Single Crystal Silicon Accelerometer Using Silicon Fusion Bonding and Deep Reactive Ion Etching
Authors: van Drieënhuizen B. P. , Maluf N. I. 
Published: March 2022

Abstract
This paper presents a single crystal silicon accelerometer with high dynamic range fabricated in a CMOS compatible, low cost technology. This technology uses a combination of Silicon Fusion Bonding (SFB) and Deep Reactive Ion Etching (DRIE). which allows thick devices (up to several hundred μm) to be defined with high aspect ratios (up to 25). In addition to the advantages of single crystalline material, the high aspect ratio results in higher sensitivity thus providing significant performance improvement. Prototypes use a hybrid approach, with an 1.0 × 1.5 mm2 accelerometer and a capacitive sensor interface providing closed-loop force-balancing to minimize non-linearity. Characterization tests of a 2 G (1 G = 9.8 m/s2) full scale device have shown a sensitivity of 2.2 V/G. The non-linearity is below the noise level, limited by 1/f noise in the electronics inherent to the foundry CMOS process. At 100 Hz, the measured noise power spectral density is approximately 80 μGrms/√Hz, which is significantly higher than the estimated 6 μGrms/√Hz noise figure for the mechanical element due to Brownian motion.
MEMS for Fluidic Controls
Authors: Ho Chih-Ming , Tai Yu-Chong 
Published: March 2022

Abstract
During the past decade, micromachining technology has become available to fabricate micron-sized mechanical parts. Micromachines have several unique features. First, typical micromachined transducer sizes are on the order of 100 microns, which can be one or more orders of magnitude smaller than traditional sensors and actuators. The drastic reduction in inertia due to these smaller sizes means a substantial increase in the frequency response. Second, the batch processing, which is characteristic of IC fabrication, can be used to make a large number of transducers for distributed sensing and actuation over a wide area. This capability enables us to sense certain flow characteristics in a 2-D domain and to perform control at the proper locations. Potential application areas include the reduction of surface shear stress in a turbulent boundary layer. Third, micromachine manufacturing technology is derived from, though not completely compatible with, IC fabrication so it is possible to integrate the IC with micro transducers to provide logic capability. The integrated microelectronics and micromachines constitute an integrated micro system, which is capable of executing sense-decision-actuation on a monolithic level.
A micro system for shear stress reduction was fabricated on a 1-cm × 1-cm die; 18 micro shear-stress sensors, 3 micro flap actuators, as well as circuits for logic sensor drivers, and actuator drivers are monolithically integrated. The lifetime of the high-speed streaks is short, and a large number of the streaks need to be controlled at the same time. If all of the sensor outputs were to be sent to a central computer and the control command were to be sent from the computer to each actuator, a very high bandwidth signal path and large number of leads would be required. Implementing local and simple signal processing is obviously a necessity for alleviating these problems. Neural networks are a viable approach. A neural-network-based circuit was developed to determine the time and the spatial extent of the high-speed streaks passing the shear-stress-sensor array. The output of the circuit was used for actuation.
Designing High-Performance Micro-Pumps Based on No-Moving-Parts Valves
Authors: Bardell Ron L. , Sharma Nigel R. , Forster Fred K. , Afromowitz Martin A. , Penney Robert J. 
Published: March 2022

Abstract
Micro-pumps utilizing no-moving-parts (NMP) valves, driven by a piezoelectric element bonded to a flexible membrane have been developed by a number of research groups (Olsson et al, 1995a; Forster et al, 1995; Gerlach and Wurmus, 1995). Recently, pump heads of over 7 m of H2O have been achieved (Olsson et al, 1996). However, no systematic methods have been reported that predict pump performance and guide the design of optimally performing pumps. We have developed a linearized dynamic system model that provides a detailed understanding of the relationship between a realistic set of system parameters and pump performance. These parameters include flow characteristics of the NMP valves, characteristics of the working fluid, pump geometry, and materials used in fabrication. Utilization of the model as a design tool, resulted in a dramatic improvement from previous “flexible” pump designs with maximum heads of approximately 0.24 m of H2O to a “stiff” design with a maximum head of 4.75 m of H2O, a twenty-fold increase in performance. Corresponding flow rates increased from 85 to 750 μl/min, a nine-fold increase.
A Lateral Repulsive-Force Drive Using Asymmetric Electrostatic Field
Authors: Lee Ki Bang , Cho Young-Ho 
Published: March 2022

Abstract
We present a new electrostatic actuation method using a lateral repulsive-force induced by an asymmetric distribution of electric field. The asymmetric electric field is induced when an electrostatic induction voltage is applied between a movable electrode and a pair of adjacent fixed electrodes. A simple analytical equation of the repulsive force has been derived from a finite element simulation. A set of repulsive-force polysilicon microactuators has been designed and fabricated by a 4-mask surface-micromachining process. Static and dynamic drive tests of the fabricated microactuators have been performed at atmospheric pressure for a varying induction voltage. The static displacement of the fabricated microactuator is proportional to the square of the DC induction voltage and is obtained as 1.27μm for the DC induction voltage of 140V. The dynamic amplitude of the fabricated microactuator has been measured as 1.9μm for the DC induction voltage of 140V with the AC drive voltage of 20V. The resonant frequency of the repulsive-force microactuator increases from 11.7 kHz to 12.7 kHz when the DC induction voltage increases up to MOV. The characteristics of the repulsive-force drive have been discussed and compared with those of the conventional attractive-force actuation.
Characterization of Thin-Film Impact Microactuators
Authors: Hipwell Roger L. , Muller Richard S. , Pisano Albert P. 
Published: March 2022

Abstract
This paper presents analysis for surface-micromachined, thin-film impact microactuators. Empirical data are given for the characterization of such a linear microactuator. These data include actuator performance trends due to slider design parameters, as well as measurements to model thin-film microscale impact. The impact is modeled by planar impulse-momentum techniques that include the effects of tangential sliding motion between the impactor and the slider during contact. The physical placement and size of the slider guides are shown to affect the magnitude of slider displacement subsequent to impact.
Periodic Heat Flux-Temperature Phase Difference for Thin Metal Films
Authors: Hays-Stang Kathy J. , Haji-Sheikh A. 
Published: March 2022

Abstract
The two-step parabolic model approximately describes microscale heat transfer in metals. Heat transfer in thin films with sinusoidal heat flux input on one surface is described by a Green’s function solution of the two-step parabolic model. The dimensionless phase angle between the sinusoidal energy input and the lattice temperature response at the opposite surface of a thin film is calculated for several dimensionless parameters that include the energy input frequency, electron-phonon coupling factor, thermal conductivity, thickness of the film, and electron and lattice heat capacities. For low dimensionless frequencies, the temperature behavior is essentially Fourier except for very thin metal films and/or for materials with very low electronphonon coupling factors. The departure from Fourier behavior as input frequency increases could allow future experimental determination of electron-phonon coupling factor and electron heat capacity. Comparison with previous calculations for thermal wave and Fourier heat transfer models shows that the dimensionless phase angle for the two-step model is generally less than for the other models.
Numerical and Experimental Study on Thermal Performance of Low Temperature Heat Pipe With Two Heaters
Authors: Park Jong Heung , Lee Seong Pal 
Published: March 2022

Abstract
A study on the operation of a heat pipe with two heat sources has been performed to optimize the heat distribution of two heaters. A numerical modeling is used to predict the temperature profiles for the heat pipe assuming cylindrical two dimensional laminar flow for the vapor, and the conduction heat transfer for the wall and wick. An experimental study using the copper-water heat pipe with a length of 0.45 m has been performed to evaluate the numerical model developed. Temperature profiles at the outer wall and the comparison of temperature distribution for the total heat input range from 29W to 94W are presented. Also the correlation between the heat input and the temperature increase is presented for the optimum distribution on two heaters. The result shows that the outer wall temperature can be controlled by redistribution of heat sources.
Development of Numerical Simulation System on Residual Gravity and Marangoni Convection
Authors: Imai Ryoji , Yoda Shinichi , Nakamura Hirohiko , Murata Keiji , Watanabe Nobuhiro , Takahashi Shingo , Isaka Norikatsu 
Published: March 2022

Abstract
A numerical simulation system to calculate residual gravity and Marangoni convection has been developed by NASDA (National Space Development Agency of Japan) in order to support researchers who conduct material processing experiments in microgravity. Boundary fixing methods and finite difference methods are applied to solve the governing equations. Residual gravity convection, solidification combined convection, and Marangoni convection are calculated by this system, and are evaluated by comparison with experimental results.