bluuebunny/crossref_metadata_2025 huggingface dataset:
Waste Heat Recovery From Fly Ash of 210 MW Coal Fired Power Plant Using Organic Rankine Cycle
Authors: Roge Nitin Hanuman , Khankari Goutam , Karmakar Sujit
Published: November 2021

Combustion of coal in thermal power plants generates ash as a residue, which depends on the quality of coal, specific to its ash content and calorific value. In a typical Indian scenario, a standard 210 MW thermal plant produces ∼57 T/hr total ash, which has 80:20 fly and bottom ash share, considering coal with 40% ash content. This study aims to harness the waste heat of fly ash collected at the bottom of the electrostatic precipitator (ESP) by coupling organic Rankine cycle (ORC) with 210 MW subcritical coal-fired thermal power plant works on R134a. Thermodynamic properties of R134a are taken from the PYroMAT library (python 3.6) to develop a computer-based program that estimates the variability of key parameters with respect to log mean temperature difference (LMTD). The main plant's efficiency was 28.714%, with main steam pressure, reheat pressure, and temperature being about 134.35 bar, 24.02 bar, and 540 °C, respectively, and combustion of coal is about 141.5 T/hr. The study shows additional generation from fly ash waste heat is about 30.5 kW with an increase in net power output (0.0145%) and net energy efficiency (0.0146%). The optimum value of LMTD for the evaporator, condenser, and recuperator is 40, 7, and 16 K, which yields the optimum energy efficiency and developed cost-effective design. The proposed system is economically analyzed, considering 25 years of equipment life and 14% of loan interest. The study shows that the payback period and the generation cost of electricity of ORC is about 6.22 years and INR 3.14 per kWh, respectively.
Polymer Solution With Very Low Relaxation Time: A Combined Numerical-Experimental Determination Strategy
Authors: Maîtrejean Guillaume , Roux Denis C. D. , Rosello Maxime , Jay Pascal , Xing Jean , Barbet Bruno
Published: November 2021

For very low relaxation time (i.e., lesser than a microsecond), viscoelastic fluid experimental determination is difficult, if not impossible. In this work, the relaxation time measurement of a weakly elastic polymer solution, too low to be measured using classical rheometry techniques, is assessed using a mixed experimental-numerical strategy. First the fluid is rheologically assessed, by measuring its shear viscosity, surface tension, and density. Then the relaxation time is determined by comparing the jetting of polymer solution from a continuous ink-jet (CIJ) device, experimentally and numerically. The numerical approach is first validated using test cases, and a viscoelastic Oldroyd-B model is used to model the experimental solution. The relaxation time is then a parameter allowing us to fit numerical simulation onto experimental results. This mixed strategy is particularly convenient for weakly elastic solution for which physical parameters cannot be measured using an experimental rheometry setup.
Microstructural and Mechanical Properties of a Solid-State Additive Manufactured Magnesium Alloy
Authors: Robinson T. W. , Williams M. B. , Rao H. M. , Kinser R. P. , Allison P. G. , Jordon J. B.
Published: November 2021

In recent years, additive manufacturing (AM) has gained prominence in rapid prototyping and production of structural components with complex geometries. Magnesium alloys, which have a strength-to-weight ratio that is superior compared with steel and aluminum alloys, have shown potential in lightweighting applications. However, commercial beam-based AM technologies have limited success with magnesium alloys due to vaporization and hot cracking. Therefore, as an alternative approach, we propose the use of a near net-shape solid-state additive manufacturing process, additive friction stir deposition (AFSD), to fabricate magnesium alloys in bulk. In this study, a parametric investigation was performed to quantify the effect of process parameters on AFSD build quality including volumetric defects and surface quality in magnesium alloy AZ31B. In order to understand the effect of the AFSD process on structural integrity in the magnesium alloy AZ31B, in-depth microstructure and mechanical property characterization was conducted on a bulk AFSD build fabricated with a set of acceptable process parameters. Results of the microstructure analysis of the as-deposited AFSD build revealed bulk microstructure similar to wrought magnesium alloy AZ31 plate. Additionally, similar hardness measurements were found in AFSD build compared with control wrought specimens. While tensile test results of the as-deposited AFSD build exhibited a 20% drop in yield strength (YS), nearly identical ultimate strength was observed compared with the wrought control. The experimental results of this study illustrate the potential of using the AFSD process to additively manufacture Mg alloys for load bearing structural components with achieving wrought-like microstructure and mechanical properties.
Hybrid Electrical-Submersible-Pump/Gas-Lift Application to Improve Heavy Oil Production: From System Design to Field Optimization
Authors: Le Vu , Tran Son
Published: November 2021

The typical challenge encountered in developing heavy-oil reservoirs is inefficient wellbore lifting caused by complex multiphase flows. The literature on modeling of a hybrid artificial-lift (AL) system is relatively sparse and these works typically model the AL system on the basis of individual AL methods. This paper presents a case study of the design and optimization of a hybrid AL system to improve heavy-oil production. We systematically design and model a hybrid electrical-submersible-pump/gas-lift (ESP/GL) system to enhance wellbore lifting and production optimization. We found that the implementation of a hybrid ESP/GL system provides the flexibility to boost production and reduces production downtime. Results from the pilot test show that the production rate in hybrid mode are approximately 30% higher than in ESP-only mode. The power consumption of the hybrid mode is 3% lower in the ESP-only mode. Additionally, the average ESP service life exceeds 6 years which is better than expected in the field development plan. The pump-performance-curve model is built with corrections for density and viscosity owing to the increased water production. We observed a higher pressure drawdown with GL injection at fixed ESP frequency. The GL injection reduces the density of the fluid column above the ESP, resulting in less pressure loss across the pump, less power consumption, and potentially extended service life. The nodal analysis results suggest that the pump capacity can be considerably expanded by manipulating the GL rate instead of increasing the frequency.
Effects of Steady Angle of Attack on Nonlinear Flutter of a Delta Wing Plate Model
Authors: Tang Deman , Dowell Earl H.
Published: November 2021

Limit cycle oscillations (LCO) have been observed in flight for certain modern high performance aircraft. The nonlinear physical mechanism responsible for the LCO is still in doubt, even to the point of it not yet being determined whether the nonlinearity is principally in the flexible elastic structure of the aircraft or due to the fluid behavior in the surrounding aerodynamic flow field. One observation from flight tests is that by changing the angle of attack of aircraft, the flight velocity at which LCO begins may be raised or lowered and that the amplitude of the LCO may be reduced. It has been suggested that this sensitivity to angle of attack indicates the nonlinearity is in the fluid rather than in the structure. In the present paper we show that such effects of an angle of attack change can be the result of a structural nonlinearity. Specifically an investigation to determine the effects of a steady angle of attack on nonlinear flutter and limit cycle oscillation of a delta wing-plate model in low subsonic flow has been made. A three-dimensional time domain vortex lattice aerodynamic model and a reduced order aerodynamic technique are used and the structure is modeled using von Karman plate theory that allows for geometric strain-displacement nonlinearities in the delta wing structure. The results provide new insights into nonlinear aeroelastic phenomena not previously widely appreciated, i.e. limit cycle oscillations (LCO) for low aspect ratio wings that have a plate-like nonlinear structural behavior. The effects of a steady angle of attack on both the flutter boundary and the LCO are found to be significant. For a small steady angle of attack, α0 ≤ 0.1°, the flutter onset velocity increases, while for larger α0 it decreases. Moreover, as α0 increases, the maximum LCO amplitude decreases substantially. Such effects have been observed by Bunton and Denegri in flight flutter experiments. It is noted that the present theoretical results do not prove that the LCO phenomena observed in flight are due to structural nonlinearities; however, the results of the present analysis are consistent with those observed in flight and do show that a structural nonlinearity can give rise to the observed effects of angle of attack on LCO.
The Use of Risk Information for the Development of a Safety Policy Around an Airport
Authors: Ale B. J. M. , Piers M. A.
Published: November 2021

Schiphol, the main airport of the Netherlands, grows rapidly. The movements of aircraft cause considerable environmental burden to the surrounding population; notably noise, odour and safety risk. In the late nineteen eighties the discussion about further extensions of the airport were based on expectations of growth, which since then were exceeded by a factor of two.

The concern about 3PR was enhanced due to a crash of a Boeing 747 into an apartment building in a suburb of Amsterdam, the capital of the Netherlands. In this accident, which happened on October 4, 1992, the four crew members were killed together with 39 inhabitants on the ground.

In order to cope with this problem the methodology to assess these risks and the policy to deal with these risks had to be developed simultaneously. This led to interesting interactions between the two.

The development of the policy is described against the background of the continuing increase in growth expectations, the development of insight in the methodology to assess the risks and the risks themselves. This is illustrated with results of safety studies and policy debates of the last decade.

In the current discussion special attention has been given to the necessity to develop policies to limit the chance of large scale disasters. The results of a study of the potential for such policies is summarised in the remainder of the paper.

The discussion about the acceptability of this risk still continues just as the discussion about Schiphol’s fate in the future.
Snowblower Failure Analysis Case Study
Authors: Brickman Dennis B.
Published: November 2021

A failure modes and effects analysis was conducted to analyze the cause of a snowblower accident in which the operator’s hand came in contact with the rotating impeller. Systematic analysis showed that the accident was caused by multiple failures of the snowblower and improper snowblower service. Results of the analysis indicate that there are available design alternatives and countermeasures which would have prevented the accident.
Risk Assessment Benchmarks: Getting Started, Making Progress in Safety Through Design
Authors: Main Bruce W. , McMurphy Kristen J.
Published: November 2021

Hazard analyses and risk assessments are practical and effective methods to address safety issues during the design process. This safety through design process is gaining commercial acceptance as a method to improve safety, productivity, and cost efficiencies. No longer are safety factors, checklists, compliance with standards, or warning labels considered leading edge safety methods. Much like quality, safety is increasingly being addressed in design rather than as a retrofit activity.

This presentation examines the increasing commercial interest in the design safety process including six key forces pushing safety through design: costs, competition, legal requirements, international influences, risk assessment advances, and the Institute for Safety Through Design (ISTD). The emergence of task-based risk assessments and computer tools for implementing safety through design is also discussed.
New Approach for Surface Microstructuring
Authors: Mardilovich Peter , Routkevitch Dmitri , Govyadinov Alexander
Published: November 2021

A new approach for microstructuring of aluminum and alumina surfaces based on localized anodization of aluminum is described. It is based on the self-organized equilibrium at the metal/oxide interface and dynamic interactions between individual oxide growth sites. Hexagonal and square closed-packed arrays of hemispherical and pyramidal features from alumina and aluminum on the micrometer scale were prepared. Potential applications of such microstructured surfaces are discussed.
Novel Resistive Point Heater for MEMS Remote Solder Self-Assembly
Authors: Kladitis Paul E. , Bright Victor M.
Published: November 2021

MEMS structures can be assembled using the surface tension of molten solder (solder self-assembly). Until this novel development, solder self-assembly was performed at the wafer or chip level where the whole chip needed to be heated to melt the micro sized solder droplets used to assemble devices. In this paper we present the design, testing, and modeling of a resistive point heater that is used to assemble an individual device on a chip without affecting neighboring devices. The point heater was packaged in 14 and 24 pin ceramic dual inline packages and tested in air, nitrogen, and formic-acid/nitrogen vapor. The lowest power needed to liquify a 63Sn/37Pb, 8 mil diameter equivalent volume solder droplet and assemble a device in formic-acid/nitrogen vapor was found to be 714 mW. The average power, of several trials, required to liquify a solder droplet is 998 mW at 141 mA and 7.08 V. A steady-state heat transfer model predicts 986.4 mW is required to keep the droplet at 181 °C (the observed minimum temperature at which 63Sn/37Pb solder is in liquid state). Growth of pure Sn platey crystals, varified by X-ray flourescence, was noted on the point heater assembly and surroundings during assembly in formic-acid/nitrogen vapor.
Linear and Geometrically Nonlinear Behavior of Metal/Polysilicon Plate Microstructures Subjected to Temperature Changes
Authors: Dunn Martin L. , Zhang Yanhang , Bright Victor M.
Published: November 2021

We study the deformation behavior of a series of gold/polysilicon MEMS plate structures fabricated by the MUMPS surface micromachining process and subjected to uniform temperature changes from 100°C to room temperature. We measured, using an interferometric microscope, full-field deformed shapes of a series of square (L×L) gold (0.5 μm thick)/polysilicon (1.5 μm thick) plate structures of sizes ranging from L = 150 μm to L = 300 μm. In general, we observed three regimes of deformation as characterized by the average curvature as a function of temperature change: i) linear thermoelastic response independent of plate size, ii) geometrically nonlinear thermoelastic response that depends on plate size, and iii) bifurcations in the curvature-temperature response that also depend on plate size. We modeled the deformation response both analytically and with the finite element method. Good qualitative and quantitative agreement was obtained between predictions and measurements in all three deformation regimes. Good agreement was also obtained between measurements and predictions of the spatial nonuniformity of the curvature across the plate.
Three-Dimensional Silicone Device Fabrication and Interconnection Scheme for Microfluidic Applications Using Sacrificial Wax Layers
Authors: Dharmatilleke Saman , Henderson H. Thurman
Published: November 2021

A simple room-temperature procedure is reported herein for formation of true three-dimensionality of “microfluidic components” and complete microfluidic systems in silicone elastomer, this is achieved by molding the plastic to simply encapsulate a pre-formed network of sacrificial wax threads or other connected wax configurations which are ultimately to become micro channels, microfluidic components and cavities in the plastic motherboard. When these wax sacrificial areas are etched away with acetone, precise cavities, channels, and capillaries result with direct arbitrary three-dimensionality. This method leads also to a simple and effective external interconnection scheme where ordinary fused silica tubes may be press-fitted into the surface opening to withstand high pressure. An array of micro channels having circular cross sections with diameters of 100, 150 and 200 microns, membrane type valves, pinch valves, mixing chambers and reservoirs for fluid storage were molded in silicone elastomer using wax filaments. The wax filaments were dissolved in acetone after the silicone elastomer became hardened, leaving the micro channels, valves, mixing chambers and reservoirs in the silicone elastomer. This scheme gives the flexibility of allowing multi stacks of components (motherboards) while being able to control the channel lengths within the stacks as desired.
Micro-to-Macro Fluidic Interconnectors With an Integrated Polymer Sealant
Authors: Tsai Jr-Hung , Lin Liwei
Published: November 2021

Micro-to-macro fluidic interconnectors with integrated polymer sealants have been successfully demonstrated. Two types of sealing processes, discrete and integrated, have been developed as the post fabrication processes to build interconnectors for microfluidic systems. In the demonstrating examples, capillary tubes of 320μm in outer diameter have been connected to a microfluidic system with microchannels of 100μm wide, 20μm deep and 800μm long by using Mylar (a polyester film by DuPont) as the sealant. The interconnection was completed on fluidic ports of 350μm in diameter. Both leakage and pull-out tests have been conducted to prove functionalities and to characterize performances of the interconnectors. The pressure test result indicates that no leakage is observed up to 190KPa. The pull-out test results show 100% survival rate under a 2 Newton pulling force.
Characterization of a MEMS-Fabricated Mixing Device
Authors: Lee Yi-Kuen , Tabeling Patrick , Shih Chiang , Ho Chih-Ming
Published: November 2021

This paper discusses the fabrication and the characterization of a MEMS-based micromixer. Active perturbations provided by a pressure source/sink system are used to enhance the mixing between two fluid streams. From our preliminary test, it appears that an effective mixing is possible through the generation of chaotic-like distortions at the interface between two streams. A numerical simulation based on a kinematical model reveals a similar behavior under the same condition.
Key Reliability Factors for IC and MEMS Packaging
Authors: Ghaffarian Reza
Published: November 2021

During the last decade, research and development of microelectromechanical systems (MEMS) has shown a significant promise for a variety of commercial applications including automobile and medical purposes. For example, accelerometers are widely used for air bag in automobile and pressure sensors for various industrial applications. Some of the MEMS devices have potential to become the commercial-off-the-shelf (COTS) components. While high reliability/harsh environmental applications including aerospace require much more sophisticated technology development, they would achieve significant cost savings if they could utilize COTS components in their systems.

This paper reviews the current status of IC and MEMS packaging technology with emphasis on reliability, compares the norm for IC packaging reliability evaluation and identifies challenges for development of reliability methodologies for MEMS, and finally proposes the use of COTS MEMS in order to start generating statistically meaningful reliability data as a vehicle for future standardization of reliability test methodology for MEMS packaging.
The Influences of the Material Properties on Ceramic Micro-Stereolithography
Authors: Sun Cheng , Zhang Xiang
Published: November 2021

Micro-stereolithography (μSL) was recently introduced in the fabrication of complex 3D ceramic microstructures. Light scattering is found to be the key factor influencing the micro-stereolithography of ceramics. In this work, numerical simulation based on the Monte-Carlo ray tracing method has been developed to investigate the influences of the important materials properties on the ceramic micro-stereolithography. It is found that the scattering are strongest when size of the ceramic powders approaches to the laser wavelength (0.3 μm). It also found that the higher the refractive index contrast between the particle and the solution, the stronger the light scattering. High laser intensity is required to fabricate high UV absorption ceramic materials to compensate the laser energy absorbed by the ceramic particle. μSL from three typical ceramic powders are examined by numerical model. The numerical model have been demonstrated as an efficient tool to optimize the micro-stereolithography process.
Cellular Automaton Approach on Micro Solidification Process of Two Phase Alloy in Horizontal Casting
Authors: Tsuta Toshio , Iwamoto Takeshi
Published: November 2021

A mathematical model of micro morphology generation in solidification process has been developed using cellular automaton approach, and heterogeneous nucleations from the wall and the grain growth kinetics are simulated by using the Monte-Carlo simulation. In the next place, the change in the micro morphology from the dendritic to the equiaxial, has been analyzed in the same way, under the condition that the liquid metal in the vessel is excited from magnetic stirrer. The results are compared with those obtained by the experiments on horizontal, continuous casting and the applicability of the method has been verified.
A Closed Loop Full-Scale Automotive Climatic Wind Tunnel for Vehicle Environment Simulation
Authors: Abdul Ghani S. A. A. , Aroussi A. , Rice E.
Published: November 2021

This paper describes the simulation of vehicle natural climatic environment in a closed loop full-scale automotive climatic wind tunnel. The tunnel simulates wind, rain, and temperature for several road conditions. It generates under controlled heat loading, wind speeds of up to 50kph with different approach boundary conditions, rainfalls from drizzle to cloudburst and road inclines up to 15° in any direction. The design and optimization process of the tunnel functions is outlined and examples of its use in vehicle development are given. The size constraint and the need for a compact design are important features of the tunnel. The tunnel provides an important test bed for close scrutiny of the relationship between rain ingress, vehicle speed, road condition, heat loading and vehicle geometry. The tunnel can also be used to study vehicle thermal management, vehicle thermal comfort, engine cold starting, and wipers efficiency in severe cold weather. Computational Fluid Dynamic (CFD) simulation is used to optimize and asses the performance of a number of key tunnel components. The resulting tunnel is approximately 9.5m in length, 9.5 m in height and 3 m in width.
Challenges in Controlling Active Suspensions for High-Speed Off-Road Vehicles
Authors: Efatpenah Keyanoush , Beno Joseph H. , Nichols Steven P. , Longoria Raul G.
Published: November 2021

The literature includes several useful control approaches for active suspension of off-road vehicles. Some of these approaches rely on preview (look-ahead) of the terrain, while others require knowledge of certain variables that have proven difficult to measure reliably for off-road applications. Sky-hook damping is a widely accepted active suspension control law.

Experimental and analytical research with active suspension systems for on- and off-road vehicles have successfully demonstrated substantial improvement in ride quality. The paper begins with a short discussion of a bond graph model of an off-road vehicle equipped with an electromechanical active suspension. The bond graph model facilitated the development of a SIMULINK model used for simulation. Comparison of simulation and experimental results has validated the model, especially for high-frequency terrain inputs. The paper examines how specific examples of off-road conditions challenge control algorithm development. Simulations demonstrate that sky-hook damping (without modification) with gains selected for very high attenuation of high-frequency terrain disturbances do not perform well in response to large displacement, low-frequency inputs and cause suspension bottoming out. By modifying the basic control laws and selecting appropriate controller gains, excellent ride performance was achieved in recent field tests under general terrain conditions.
Effects of Process Conditions on Shrinkage and Warpage: Experiments and Simulations
Authors: Wang James T. , Yoon C. K.
Published: November 2021

In the injection mold process, a pressure gradient exists from the polymer entrance to the last-fill location. At different planar locations of a part, when the polymer melt cools down to the transition temperature and freezes (changes from liquid to solid) at different pressures, shrinkage at the various locations will be different. If cooling channels are not arranged properly, the mold wall temperatures on the cavity and core sides can be different. This unbalanced cooling can also cause the melt at the upper and lower halves of the cavity to shrink differently, because they freeze at different times and different pressures. These two types of non-uniform shrinkage will cause parts to warp.

Reducing shrinkage and warpage is one of the top priorities for improving the quality of injection molded parts. In addition to part design and material properties, process conditions are the most important determinants of part quality. In this paper, the relationship between process conditions and in-cavity residual stress will be studied. In-cavity residual stress is the driving force that causes parts to deform after they are taken out of the mold. The effects of process conditions on injection-molded part quality (in terms of shrinkage and warpage) will be discussed. Different packing pressure levels, together with unbalanced cooling from mold wall temperatures, will be examined. Deformation of injection molded parts will be measured. Comparisons between experimental and numerical simulation results will be reported.
Macro Modeling of Reactive Infiltration Using Level Set Finite Element Formulations
Authors: Balagangadhar Dinesh , Rajesh Gopalaswamy
Published: November 2021

The process of reactive melt infiltration can be used to fabricate ceramics and ceramic matrix composites. This process involves a liquid metal being allowed to infiltrate a medium with which the liquid reacts to form a resultant ‘matrix’ along with the already present reinforcing fibers. The authors’ previous work on this area revealed that the transient porosity and permeability of a porous medium can be determined for certain geometries from the reaction kinetics and coupled heat and mass transfer problem occurring at the pore level. But the formulation at the macro level, which is essential to optimize the process, has been limited. Towards this end, this paper solves the macro reactive flow problem in a porous medium analytically as well as numerically. The focus of this article will be on the solutions for the advance (displacement) of the ‘infiltration front’ with progressive chemical reaction occurring between the medium and the infiltrant. A finite element formulation is used to solve the problem computationally; a level set formulation is used to track the infiltration front during the process. Excellent agreement is obtained between the analytical and computational solutions thereby validating the level set finite element formulations.
On the Equivalence of the Stress and Displacement Methods in Planar Anisotropic Elasticity
Authors: Gao Xin-Lin , Rowlands Robert E.
Published: November 2021

The stress formalism of Lekhnitskii and the displacement formalism of Eshelby, Read and Shockley (ERS) are firstly recapitulated and compared for problems of planar anisotropic elasticity. It is explicitly demonstrated that for such problems the two formalisms lead to the identical characteristic equation and thus are equivalent. An alternative displacement formulation method is then presented for the same problems using an extended version of Green’s theorem. This approach introduces a displacement function, which satisfies a fourth-order partial differential equation whose characteristic equation is identical with that obtained using the methods of Lekhnitskii and ERS. The new approach is proved to be equivalent to those of Lekhnitskii and ERS for problems of planar anisotropic elasticity. The present displacement function method exhibits similarities with the Airy stress function method.
Heat Transfer Enhancement by Turbulent Impinging Jets
Authors: Kumagai M. , Amano R. S. , Jensen M. K.
Published: November 2021

A numerical and experimental investigation on cooling of a solid surface was performed by studying the behavior of an impinging jet onto a fixed flat target. The local heat transfer coefficient distributions on a plate with a constant heat flux were computationally investigated with a normally impinging axisymmetric jet for nozzle diameter of 4.6mm at H/d = 4 and 10, with the Reynolds numbers of 10,000 and 40,000. The two-dimensional cylindrical Navier-Stokes equations were solved using a two-equation k-ε turbulence model. The finite-volume differencing scheme was used to solve the thermal and flow fields. The predicted heat transfer coefficients were compared with experimental measurements. A universal function based on the wave equation was developed and applied to the heat transfer model to improve calculated local heat transfer coefficients for short nozzle-to-plate distance (H/d = 4). The differences between H/d = 4 and 10 due to the correlation among heat transfer coefficient, kinetic energy and pressure were investigated for the impingement region. Predictions by the present model show good agreement with the experimental data.
Dimensionless Parameters for the Optimization of Annular-Finned Tubes
Authors: Cortés Cristóbal , Arauzo Inmaculada , Campo Antonio
Published: November 2021

This paper addresses the problem of optimizing an array of annular fins starting from an empirical fit of the average convection coefficient that recognizes the influence of the fin spacing. A dimensionless formulation is proposed to reduce the number of independent parameters to only four, being applicable to a rather generic situation. The formulation is illustrated with a parametric study encompassing the ranges of interest of the variables: Reynolds number, thermal conductivity ratio, volume constraint and fin spacing and thickness. Applied to the standard designs of annular-finned heat exchangers, the method predicts fully coherent points of optimum thermal performance. A sequence is suggested to integrate the optimization process within the design calculations of heat exchangers, and several graphs are presented which are suitable to this purpose. The method can be applied to the design and scaling calculations of annular-finned tube bundles for gas-liquid or gas-gas applications.
Eight-Ton Advanced GAX Cycle Prototype Results
Authors: Anand G. , Erickson Donald C.
Published: November 2021

The advanced Vapor eXchange Generator Absorber heat eXchange (VX GAX) cycle has similar components as the basic GAX cycle but is a three-pressure cycle and makes more complete use of the GAX temperature overlap. Less external heat is supplied to the generator, and the cycle efficiency is increased.

A breadboard prototype of a gas-fired heat pump using the VX GAX cycle has been developed and tested. A higher COP was achieved using reliable and cost effective components.

This paper presents the VX GAX cycle breadboard design concept, the hardware realization, and the performance achieved. Several novel concepts were incorporated to achieve the design objectives of higher efficiency and capacity, lower cost, compactness, avoidance of code restrictions, and operability from 49°C (120°F) summer to −8°C (17°F) winter ambient conditions.

The prototype results have confirmed the high performance capability of the advanced GAX cycle. At 35°C (95°F) ambient air-cooled conditions, a gas-cooling COP of 0.85 was achieved at design capacity. This is a 20% improvement relative to current basic GAX chillers. The eight-ton capacity is ideal for small-scale commercial applications and provides economy of scale. The wide ambient operating range is key to year-round operation and attractive payback in all climate zones. The demonstrated improvement in both system performance and cost is key to achieving nationwide mass-market status.
The Role of Surfactant Adsorption Rate in Heat and Mass Transfer Enhancement in Absorption Heat Pumps
Authors: Koenig Michael S. , Grossman Gershon , Gommed Khaled
Published: November 2021

The importance of heat and mass transfer additives in absorption chillers and heat pumps has been recognized for over three decades. However, a universally accepted model for the mechanisms responsible for enhanced absorption rates has yet to be proposed. The Marangoni effect — an instability arising from gradients in surface tension at the liquid-vapor interface — is generally accepted as the cause of the convective flows that enhance transfer rates. Certain surfactant additives can significantly improve absorption rates and thus reduce the overall transfer area required by a given machine. Any means available that can increase the efficiency and acceptability of absorption machines is to be welcomed, as this technology provides an alternative to vapor compression systems which is both environmentally friendly and more versatile with regards to energy sources.

This study investigates the rate at which a surfactant additive adsorbs at a liquid-vapor interface. The residence time of the falling liquid solution in an absorber is quite short. An effective additive must not only reduce the surface tension of the solution; it must do so quickly enough to cause the Marangoni instability within the short absorption process time. The entrance region of an absorber features a freshly exposed interface at which no surfactant has adsorbed.

A numerical model is used to analyze surfactant relaxation rates in a static film of additive-laced solution. Kinetic parameters for the combination of the working pair LiBr-H2O and the additive 2-ethyl-1-hexanol are derived from data in the literature for static and dynamic surface tension measurements. Bulk, interfacial and boundary parameters influencing relaxation rates are discussed for surfactant adsorption occurring in the absence of absorption, as well as for concurrent adsorption and stable vapor absorption. Initial solution conditions and absorption driving force are shown to impact the potential for instability in the effect they have on the rate of interfacial additive adsorption.
Exhaust Energy Recovery for Control of a Homogeneous Charge Compression Ignition Engine
Authors: Martinez-Frias Joel , Aceves Salvador M. , Flowers Daniel , Smith J. Ray , Dibble Robert
Published: November 2021

This work investigates a purely thermal control system for HCCI engines, where thermal energy from exhaust gas recirculation (EGR) and compression work in the supercharger are either recycled or rejected as needed. HCCI engine operation is analyzed with a detailed chemical kinetics code, HCT (Hydrodynamics, Chemistry and Transport), which has been extensively modified for application to engines. HCT is linked to an optimizer that determines the operating conditions that result in maximum brake thermal efficiency, while meeting the restrictions of low NOx and peak cylinder pressure. The results show the values of the operating conditions that yield optimum efficiency as a function of torque for a constant engine speed (1800 rpm). For zero torque (idle), the optimizer determines operating conditions that result in minimum fuel consumption. The optimizer is also used for determining the maximum torque that can be obtained within the operating restrictions of NOx and peak cylinder pressure. The results show that a thermally controlled HCCI engine can successfully operate over a wide range of conditions at high efficiency and low emissions.
An Investigation Into the Drying of Distribution Transformers Using the Hot Air Vacuum Method
Authors: Gopalan R. , Al-Jumaily A. M. , Leece P.
Published: November 2021

A hot air vacuum method with considerable difference in design and constructional features as compared with the conventional process of a normal convection oven has been built and operated for drying transformers up to 1000 kVA, 33 kV. Moisture-equilibrium charts for kraft paper were used for designing the drying system. A high temperature air circulation fan placed inside the vacuum chamber simplified the construction and using air ducts directed at the transformer inside the autoclave improved the heat transfer capability and reduced the heating time for the transformer. A dry vacuum pump used for moisture removal eliminated the need for condensing water vapour before exhausting it into the atmosphere. A mathematical model for predicting the heating and vacuum cycle for distribution transformers in the autoclave has been presented with reasonably accurate results. Experimental results give a 1% or less moisture content in the insulation after dryout in about 10–12 hours. This indicates energy savings over a conventional air circulation process of about 70%.
Experimental Study of Thermal Energy Storage System
Authors: Yang Bing-Chwen , Huang Shr-Hau , Lin Hsiang-Hui
Published: November 2021

In this paper, the feasibility of phase change material that used for thermal energy storage in the range of 400 ∼ 600°C in the form of latent heat is examined for nine different salts and eutectic salts. The Differential Scanning Calorimeter (DSC) was used to perform the quantitative measurement of the phase change temperature (Tm) and latent heat (ΔH). The thermal properties of NaCl-CaCl2 at repeated heating and cooling cycles were studied with a heating chamber. The quality observation for this phase change material was also performed with this heating chamber to understand its physical phenomena during heating and cooling process. It is found that NaCl-CaCl2 is a good candidate of thermal energy storage material for its stable properties, low cost, and no toxic. Finally, the thermal storage unit with NaCl-CaCl2 as thermal energy storage material was tested to study and evaluate its performance as the application in the waste heat recovery system.
Dynamic Behavior of a Directly Combined Binary Turbine System Using a Mixture (R134a/R123)
Authors: Tanzawa Yoshiaki , Amano Yoshiharu , Hashizume Takumi , Usui Akira
Published: November 2021

Our previous binary turbine system, which employs steam as the primary working fluid, used R11 as the secondary working fluid because R11 has good characteristics as a working fluid in power plants. However, substitute LBMs (Low Boiling temperature Mediums) are being developed because of the ozone layer depletion by CFCs. We investigated the system using R123 in the next stage. Because R123 is also controlled, in the previous paper, modeling of the dynamics of a directly combined binary turbine system using a mixture of R134a and R123 are described. In this paper, the steady state characteristics and dynamic behavior of the system using a mixture of R134a and R123 are investigated taking into account the mole fraction of the mixture. In addition to the investigation using the experimental system, the following are clarified using our model: In the steady-state characteristics, there are remarkable differences in pressure based on the thermodynamic properties and in the load allotment of the two turbines. However, in the dynamic characteristics, the effect of the mole fraction could hardly be observed on the response characteristics of the rotating components to the load change.
Study of a Fuel Cell Cogeneration System Applied to a Brazilian Tertiary Sector
Authors: Silveira Jose Luz , Leal Elisângela Martins
Published: November 2021

In this paper, a methodology for the study of a molten carbonate fuel cell cogeneration system and applied to a computer center building is developed. This system permits the recovery of waste heat, available between 600°C and 700°C, which can be used to the production of steam, hot and cold water, hot and cold air, depending on the recuperation equipment associated. Initially, some technical information about the most diffusing types of the fuel cell demonstration in the world are presented. In conclusion, the fuel cell cogeneration system may have an excellent opportunity to strengthen the decentralized energy production in the Brazilian tertiary sector.
Handling of Collimated Irradiation on a Plane-Parallel Participating Medium
Authors: Proulx Christian , Rousse Daniel R. , Vaillon Rodolphe , Sacadura Jean-François
Published: November 2021

This article presents selected results of a study comparing two procedures for the treatment of collimated irradiation impinging on one boundary of a participating one-dimensional plane-parallel medium. These procedures are implemented in a CVFEM used to calculate the radiative heat flux and source. Both isotropically and anisotropically scattering media are considered. The results presented show that both procedures provide results in good agreement with those obtained using a Monte Carlo method, when the collimated beam impinges normally.
A PIV Methodology for High-Resolution Measurement of Flow Statistics
Authors: Cummings Eric B. , Schefer Robert W. , Chung Jacob N.
Published: November 2021

Particle-image velocimetry (PIV) is a flow-diagnostic technique that provides velocity fields from a comparison of images of particulate-laden flow. We have developed a PIV processing methodology that extracts measurements of the particle-displacement probability density function (PDF) from a flow video or ensemble of flow-image pairs. Single-pixel measurement of mean velocity can be obtained from an ensemble of O(103) images. Measurements of higher-order moments of the velocity PDF require spatial averaging (i.e., lower spatial resolution), larger ensembles of images, or a combination of the two. We present single-pixel-resolution PIV measurements of a steady microflow and high-resolution measurements of the velocity PDF of a stationary turbulent flow. This methodology has applications in quantifying velocity statistics in other stochastic flows, e.g., bulk and near-wall boiling.
The Effect of Radiation on Turbulent Convective Heat Transfer Over an Ablating Solid
Authors: Akyuzlu K. M. , Antoniou A. , Kagoo R.
Published: November 2021

A numerical study is conducted to investigate the effect of thermal radiation on turbulent flow (upstream of the flame front) inside a subscale planar hybrid rocket motor. The physical model adopted for the study is based on an unsteady two-domain (solid fuel and gaseous oxidizer) concept where both domains are assumed to be two-dimensional. Furthermore, the oxidizer gas flow is assumed to be incompressible and turbulent with boundary layer approximations. The radiative heat transfer is incorporated to the energy equation for the oxidizer using the Rosseland diffusion approximation. Fuel is assumed to be a nontransparent isotropic solid. The two domains are coupled through an energy balance at the interface that includes heat transfer due to radiation, conduction, and ablation. The solution to the governing differential equations of the present model is obtained by first linearizing the equations using Newton linearization method, discretizing them by a fully implicit finite-difference technique, and then solving the resulting set of algebraic equations by a block tridiagonal matrix solver. Finally, the proposed mathematical model is used in a parametric study to determine the effect of various operational parameters, such as flame temperature and oxidizer mass flow rate, on heat transfer from the solid fuel. Results indicate the significance of radiation on turbulent convective heat transfer over an ablating solid.
Description of Chemotactic Cell Migration via Optical Flow Methods
Authors: Choi Lisa , Georgiadis John G. , Horwitz Alan R.
Published: November 2021

The application of optical flow image processing methods in the quantification of cell migration on substrates is reported here. By extracting pixel-based displacement vectors from time-lapse microscopy, this technique allows the accurate and objective analysis of the cell motility process.
Two Fiber Optical Fiber Thermometry
Authors: Jones Matthew R. , Farmer Jeffery T. , Breeding Shawn P.
Published: November 2021

An optical fiber thermometer consists of an optical fiber whose sensing tip is given a metallic coating. The sensing tip of the fiber forms an isothermal cavity, and the emission from this cavity is approximately equal to the emission from a blackbody. Temperature readings are obtained by measuring the spectral radiative flux at the end of the fiber at two wavelengths. The ratio of these measurements is used to infer the temperature at the sensing tip. However, readings from optical fiber thermometers are corrupted by emission from the fiber when extended portions of the probe are exposed to elevated temperatures. This paper describes several ways in which the reading from a second fiber can be used to correct the corrupted temperature measurements. It is shown that two of the correction methods result in significant reductions in the systematic errors. However, these methods are sensitive to random errors, so it is preferable to use a single fiber OFT if the uncertainties in the measurements are large.
Heat Transfer Implications in the First MEMS Fabricated Thermal Transpiration-Driven Vacuum Pump for Gases
Authors: Vargo Stephen E. , Green Amanda A. , Muntz E. P.
Published: November 2021

The success of NASA’s future space missions and the development of portable, commercial instrument packages will depend greatly on miniaturized components enabled by the use of microelectromechanical systems (MEMS). Both of these application markets for miniaturized instruments are governed by the use of MEMS components that satisfy stringent power, mass, volume, contamination and integration requirements. An attractive MEMS vacuum pump for instruments requiring vacuum conditions is the Knudsen Compressor, which operates based on the rarefied gas dynamics phenomenon of thermal transpiration. Thermal transpiration describes the regime where gas flows can be induced in a system by maintaining temperature differences across porous materials under rarefied conditions. This pumping mechanism provides two overwhelmingly attractive features as a miniature vacuum pump — no moving parts and no working fluids or lubricants. Due to favorable power, volume and mass estimates a Knudsen Compressor fabricated using MEMS fabrication techniques (lithography, deep reactive ion etching) and new materials (silicon, aerogel) has been completed. The experimental testing of this MEMS Knudsen Compressor device’s thermal and pumping performance are outlined in this manuscript. Good agreement between experiments and numerical predictions using a transitional flow analysis have also been obtained although simple simulations based on the aerogel’s structure are difficult to perform.
Applications of Artificial Neural Network Analysis in Thermal Systems
Authors: Mahajan R. L. , Yang K. T.
Published: November 2021

Artificial neural networks (ANNs) are good at approximating complex and non-linear data. In addition, they have excellent predictive capabilities and can be configured to be self-adaptive. As a result of these characteristics, the potential applications of ANNs are many and in diverse fields. These range from predicting the output of a manufacturing process through differentiating between handwritten letters to predicting the winner of a horse race. In this paper, we focus on applications of artificial neural networks to thermal systems including chemical vapor deposition, thermal management and heat exchangers.