bluuebunny/crossref_metadata_2025_split huggingface dataset:
Adiabatic Availability
Authors: Metghalchi Mohamad 
Published: January 2022

Abstract
Adiabatic availability, a property, is defined as the largest work that can be done by a system in an adiabatic, constant mass and volume process. Adiabatic availability of all systems at any state is larger than or equal to zero. Adiabatic availability of a system in stable equilibrium state is zero. Adiabatic availability of a composite made of a system and a reservoir is the same as the available energy of the system with respect to the given reservoir. Change of adiabatic availability, transfer of adiabatic availability and destruction of adiabatic availability due to irreversibility for few processes have been investigated.
Improving the Performance of an Existing Air-Cooled Binary Geothermal Power Plant: A Case Study
Authors: Kanoğlu Mehmet , Çengel Yunus A. 
Published: January 2022

Abstract
An existing air-cooled binary geothermal power plant in Northern Nevada with an average net power output of 27 MW is studied. The current performance of the plant is analyzed with an emphasis on the effects of seasonal climate changes. Two potential sites have been identified to improve the performance of the plant. Northern Nevada has a dry climate particularly in hot summer months, and the temperature of cooling air can be decreased considerably by evaporative cooling. When the air temperature is decreased to the wet-bulb temperature, the decrease in the condenser temperature is determined to increase the power output by up to 29%. The required amount of water for this case is calculated to be about 200,000 tons per year. Several parametric studies are performed by simulating the operation of the plant with an equation solver with built-in thermophysical property functions. It is determined that the net power output of the plant can be increased by 2.8 percent by optimizing the maximum pressure in the cycle. Also, replacing the existing working fluid isobutane by other commonly used binary fluids such as butane, R-114, isopentane, and pentane can increase the net power output by up to 2.5 percent.
Exergy and Pinch Analysis of an Advanced Ammonia-Water Coal-Fired Power Cycle
Authors: McIlvried Howard G. , Ramezan Massood , Enick Robert M. , Venkatasubramanian Srikanth 
Published: January 2022

Abstract
An exergy analysis of a power system identifies the location, type, and magnitude of losses of the potential to do work, while a pinch analysis examines a heat exchange network efficiency. A complete exergetic analysis of Kalina cycle System 19, an advanced binary fluid (ammonia-water working fluid) power cycle, is presented along with a combined pinch/exergy analysis of the Kalina cycle heat exchanger/furnace/cooling utility network. The Kalina cycle System 19 has a net thermal efficiency (net work/furnace duty) of 43% (HHV), a furnace exergetic efficiency of 77.4%, and an exergetic plant efficiency (net work/exergy of flue gas) of 61.6%. Most of the exergy losses (21.5%) occur in the furnace; 9.6% of the exergy is lost in pumps, turbines, throttles, mixers, and the stack gas; and 7.3% of the exergy loss occurs in heat exchanger/cooling utility network. The System 19 total exergy loss in all heat exchange equipment is only 7.2% greater than its minimum value. Thus, the analysis indicates that the Kalina cycle System 19 is efficiently designed.
The Rational Efficiency of Fossil-Fuel Power Plants
Authors: Horlock J. H. , Young J. B. , Manfrida G. 
Published: January 2022

Abstract
The definition of open cycle rational efficiency is unequivocally based on the ratio of the actual shaft work output from a power plant to the maximum work that could be obtained in a reversible process between prescribed inlet and outlet states. However, the specification of this ideal process remains a matter for discussion. The “classical” definition specifies the outlet state as a “standard” atmosphere (p0,T0) with a given composition of constituent gases and an exergy of zero. The ideal work output is then the exergy of the fuel supplied, which is the sum of the Gibbs function change in reversible combustion at (p0,T0) and the work of extraction and delivery of the reactant and product species.
However, two other ideal processes may be considered in which different outlet states are specified leading to alternative definitions of rational efficiency. In one process all species enter and leave the ideal plant individually at (p0,T0) in thermal and mechanical (but not chemical) equilibrium with the environment. In the other, the exhaust is at (p0,T0) but the gas composition is the same as in the real process. A further complication occurs when water or steam is injected into a gas turbine plant. In such cases the exergy of the added water must be considered within any definition of rational efficiency. The three definitions of rational efficiency are discussed and compared and some illustrative calculations presented.
The Pressure-Exchange Ejector Heat Pump
Authors: Garris Charles A. , Hong Woo Jong , Mavriplis Catherine , Shipman Jeremy 
Published: January 2022

Abstract
The pressure-exchange ejector offers the possibility of attaining a breakthrough in the level of performance of ejectors by means of utilizing non-dissipative non-steady flow mechanisms. Yet, the device retains much of the mechanical simplicity of conventional steady-flow ejectors. If such a substantial improvement in performance is demonstrated, its application to ejector refrigeration will be very important. Such a development would provide significant benefits for the environment in terms of both CFC usage reduction and greenhouse gas reduction.
The current paper will discuss in detail the concept of pressure-exchange ejector refrigeration, compare it with existing technologies, and discuss the potential impact that might be derived if certain levels of ejector performance can be achieved. Since the limiting issue on the system performance is in the fluid dynamics of non-steady flow induction, research issues and recent progress will be discussed.
Valve Opening and the Onset of Flow in a Reciprocating Compressor Cylinder
Authors: Overfield Norbert W. 
Published: January 2022

Abstract
This paper describes ongoing development work on a new class of compressor valves. The significant feature of the new valve is that it opens promptly upon pressure reversal. This response differs markedly from conventional valves, which do not start to open until a substantial pressure difference (approximately ten percent of upstream pressure) is established. Improved adiabatic efficiency and reduced valve velocity at first contact with the lift stop were noted during the initial prototype tests of the new valve.
The current work is an attempt to gain a better understanding of the causes of these improvements. Specifically, the effects of valve spring pre-load and rate on the opening valve velocity and stop impact arc explored.
The results of a time domain study of valve opening are presented. Opening dynamics of both conventional plate valves and equivalent valves of the new design are investigated. The specific goals are to determine the effects of differing rates and pre-loads in the plate return springs.
Study of Heated Accumulator in Air-Source Heat Pump With Binary Mixture
Authors: Sami Samuel M. , Desjardins Daniel E. 
Published: January 2022

Abstract
In this paper, an experimental study is presented on the behavior of zeotropic versus azeotropic binary mixtures in heated accumulator air-source heat pump during heating mode. The experimental set up was composed of a fully instrumented air-source heat pump with a capacity of 36,000 BTUH and equipped with a heated suction accumulator.
Standard heating mode test conditions were used at the condenser inlet; however, the refrigerant temperatures were varied at the evaporator entrance from 5 to −40 °C, to simulate various conditions encountered in air-source heat pump applications. The primary parameters observed during the course of this study were mass flux, heat flux, quality, thermal capacities, power consumption and pressure ratios for the refrigerants under investigation.
The test results showed that a heated suction accumulator helps to evaporate the more volatile component of the binary mixture, thus, increasing the mixture thermal capacity. Furthermore, experiments have also shown capacity increases of 27% with heated accumulator over unheated accumulator at −30 °C outside air temperatures.
Heat Exchanger Mean Temperature Differences for Refrigerant Mixtures
Authors: Schaefer Laura A. , Shelton Samuel V. 
Published: January 2022

Abstract
Many of the refrigerants that have been examined as replacements for hydrochlorofluorocarbons (HCFCs) are zeotropic mixtures. The temperature of a zeotropic mixture does not remain constant throughout a heat exchanger, and zeotropes often exhibit a nonlinear temperature/enthalpy relationship. These factors contradict some assumptions that are made in deriving the Log Mean Temperature Difference (LMTD), a calculation that is used to compute the size of a heat exchanger (UA). Since the temperature is not an easily-determined function of enthalpy, in order to find a more accurate UA, the heat transfer process must be discretized and the properties determined at each point. An ammonia-water mixture and synthetic mixtures that are being studied as HCFC-22 replacements are analyzed. In each case, the actual UA is compared to the UA found using the LMTD. It is found that these errors can cause a heat exchanger to be undersized by as much as a factor of fifty.
Preliminary Secondary Power System Thermodynamic Analysis for Tactical Aircraft Pulsed Loads
Authors: Lykins Richard , Ramalingam Mysore L. , Donovan Brian D. , Cloyd James S. , Beam Jerry E. 
Published: January 2022

Abstract
A computerized thermodynamic analytical program has been developed to investigate the impact of secondary power system improvements on mission effectiveness and efficient pulsed power generation in a conventional tactical aircraft. Besides indicating that the engine performance in a conventional aircraft was more sensitive to pneumatic bleed than to shaft power extraction, the analysis also revealed a 5% improvement in fuel consumption with the use of a more electric secondary power system. Using the total fuel consumed by the conventional aircraft for a typical tactical mission as a baseline, several investigative options were considered for the excess fuel availability, for an identical situation with the more electric secondary power system. The result was the availability of multiple combat mission legs or an equivalent of 24 kW of pulsed power that could potentially be used for communications purposes or as a weapon load. The improvements in the quality of the pulsed power with the incorporation of cryogenic technologies and a trade study between open and closed cryogenic cooling systems are also presented in this investigation.
The Effects of Channel Height on Flow Boiling of Liquid Nitrogen
Authors: Lu W. , Chow L. C. 
Published: January 2022

Abstract
The quest for high-power electronics operating in a cryogenic environment has given rise to the need for very effective cryogenic cooling of the electronic devices. Electronic chips are usually mounted on the circuit boards. Those boards are stacked one above or next to the others. For the electronic engineers who design the electronic systems, how close the circuit boards can be stacked together is very important. This paper presents an investigation of effects of flow channel heights on flow boiling heat transfer with liquid nitrogen from small, discrete heat sources that simulate electronic chips. The experimental apparatus is designed to allow visual observation of the phase-change phenomena of cryogen (liquid nitrogen) at the heat sources. Experiments with different flow channel heights have been conducted. It is noted that the channel height has little effect on the CHF until the channel height is decreased to approximately 1.6 mm. The critical heat flux (CHF) and the heat transfer coefficient decreases significantly. There is no significant difference between the heat transfer conditions in flow channel heights of 6.35 mm and 3.18 mm, which indicates that distance between the multi-layer-stacked electronic boards should be larger than the critical height (1.6 mm) in order to obtain optimum cooling results. A model to describe the heat transfer mechanism near CHF was developed using the present results and those of previous investigators. A correlation was established using this model and the experimental data. This correlation provides a good fit to the experimental data from various flow channel heights.
Heat Spreaders for High-Power Electronics Employing Boiling Mechanisms in a Narrow Space
Authors: Gao M. , Cao Y. 
Published: January 2022

Abstract
To achieve a high heat-flux level and reduce manufacturing costs associated with conventional heat pipes, the concept of network heat spreaders employing boiling heat-transfer mechanism in a narrow space has been proposed and several flat-plate wickless heat spreaders have been designed and fabricated. The heat spreaders have been tested under different working conditions and orientations relative to the gravity with very good results. The previously tested network heat spreaders, however, were based on plates with a relatively large size for general heat spreading purposes. In the present study, network heat spreaders with overall dimensions of 78 × 62 × 3.2 mm are designed and fabricated. The spreaders with this size are intended for use as heat sinks of high-power electronic components. External cooling fins are attached to enhance air-cooling heat transfer rate. The network heat spreaders are tested under various working conditions with water as the working fluid. The maximum heat input rate achieved is about 150 W with a corresponding heat flux of 60 W/cm2. Compared to the performance of a solid copper plate having the same overall size as the spreader, the maximum temperature difference over the surface is reduced from about 32 °C to 3.3 °C. The heat transfer performance of the spreader is also largely dependent on the filling ratio of the working fluid and the boiling heat transfer in the narrow space. For these reasons, boiling heat transfer mechanisms in a narrow space are analyzed, and a spreader design that would improve the performance in a horizontal position is described.
Processing Induced Warpage in Composite Cylindrical Shells
Authors: Meink Troy E. , Shen M.-H. Herman 
Published: January 2022

Abstract
This paper investigates a cause for warpage in structures manufactured using filament winding or fiber placement. This warpage phenomena has been determined to be caused by fiber/resin consolidation resulting from manufacturing parameters including: cure pressure, winding tension, and material system characteristics. This is a non-thermal phenomena and is independent of cure temperature, or finished part operational environments. A novel theory has been developed to predict the warpage or “springback” resulting from the processing induced strain gradient that develops in laminates due to the consolidation. This paper utilizes a strain model derived previously to develop a warpage prediction model utilizing Classical Laminated Plate Theory (CLT). This theoretical solution is than compared to experimental results for hoop wound test specimens. The end goal of the research is to develop a springback prediction model that can be applied to large scale parts utilizing consolidation parameters measured at the coupon level.
Micro Instabilities in a System of Particles in Silos During Filling Process
Authors: Gavrilov Dmitri , Vinogradov Oleg G. 
Published: January 2022

Abstract
The process of filling a silo with particles is simulated by placing them one-by-one at random locations. In simulations, a plane problem is considered and the particles are represented by disks. After each disk is placed on the system of disks already in a silo, the distribution of normal and shear stresses is recalculated. If any shear stress exceeds the predetermined limit, then a slip takes place. It is found that a slip can occur between a few particles simultaneously. Such a micro-slip reflects a physical instability in the system. It also results in a numerical instability. A Recursive Inverse Matrix Algorithm (RIMA) is implemented to account for the topological changes in the system during the loading. It allows efficient addition/removal of contact interfaces between the particles by updating the inverse matrix of the system rather then generating and solving a system of equations after each topological change. The extent of instabilities is determined numerically using RIMA update algorithm iteratively. As a result of irreversible events taking place during the filling operation, the final stress distribution in a filled silo is loading history-dependent. A numerical example of filling a silo with 500 particles is given as an illustration.
Biomechaimical Study of Ballistic Impact on Helmets: Injury of Head and Neck
Authors: Kwon Y. W. , King Q. M. 
Published: January 2022

Abstract
Technology has improved dramatically over the last quarter century. It has allowed the development of personal body armor capable of preventing penetration of fragments traveling in excess of 609 m/s (2000 ft/s). However, these strides have also exposed the body to greater impact energies without a lethal penetration. The objective of this study was to examine how the body, in particular the head-neck complex, responds to these impacts. A finite element model was developed to characterize the behavior of this biomechanical system. This model was validated against experimental work. The validated model was then subjected to impacts at different positions to induce different load cases. Each set of results was then compared to Head Injury Criteria (HIC), Abbreviated Injury Scale (AIS), and the Injury Assessment Reference Values (IARVS) for evidence of injury potential. Disc stiffness was found to be proportional to the injury potential. Rupture of the disc was considered likely for most cases considered. Fracture of the vertebral body was considered likely in a half of the cases under study.
Impact Damage Resistance of Aluminum Alloy Foams
Authors: McRae Jametta , Kelkar Ajit , Grace Christopher , Craft William , Giamei Tony 
Published: January 2022

Abstract
While some polymers are engineered to improve strength and endurance under elevated temperatures, these same materials are costly both economically and environmentally with the latter of the two stimulating the interest for this study. Polymers, more specifically foam cells are generally flame retardant. When ignited, toxins such as fluorine, bromine and other metallic salts are given off in the air. This poses potential environmental hazards. However, metallic materials (Aluminum) with their high strength, stiffness and ductility are much more environmentally friendly. Even if alloyed with appropriate compounds, the resulting core material could be melted down, separated then cast into new stock. Moreover, the use of an alloyed material can generally enhance the strength and stiffness of sandwich composite structures so essential in aerospace applications.
United Technologies Research Center provided a plate of Aluminum alloy foam for impact testing by North Carolina A&T Researchers and graduate students. The material was provided by Austrian Metals Co. (AMAG) to UTRC under ONR Contract # N00014-95-C-0231, Thompson & Renauld (1997). All specimens were cut from one sample of nominal dimensions of 20 inches by 20 inches by 0.65 inches in thickness. The sample mass was 3142 grams and the apparent density was 0.737 g/cc. The chemical composition is close to that of 6061. The sheet sample was formed by AMAG and heat treated to T5 specifications consisting of 14 hours in a furnace at 160 °C.
Generally the bending stiffness and failure mechanisms were substantially different from those of polymeric foam sandwich cores made of Rohacell, a polymethacrylimide (PMI) foam in a prior study, Craft et al (1997). Rohacell is an easily machined, but a hygroscopic form with low shear strength and stiffness, but it and many other organic foams have a relatively uniform cellular construction in a wide variety of densities.
Fatigue-Life Prediction of SiC Particulate Reinforced Aluminum Alloy 6061 Matrix Composite Using a Weibull Distribution Model
Authors: Shan D. , Nayeb-Hashemi H. 
Published: January 2022

Abstract
This paper presents the feasibility of acoustic emission technique in predicting the residual fatigue life prediction of 6061-T6 aluminum matrix composite reinforced with 15 vol. % SiC particulates (SiCp). Fatigue damages corresponding to 40%, 60% and 80% of total fatigue life were stimulated at a cyclic stress amplitude. The specimens with and without fatigue damage were subjected to tensile tests. The acoustic emission activities were monitored during tensile tests. The number of the cumulative AE events increased exponentially with the increase of strain during tensile tests. This exponential increase occurred when the material was in the plastic regime and was attributed mainly to SiC particulate/matrix interface decohesion. The cumulative events during post fatigue tensile tests reduced with the decrease of the fatigue residual life. Based on the high cycle fatigue damage accumulation model, a Weibull probability distribution model is developed to explain the post fatigue AE activity of specimens during tensile test. Using the model, the residual fatigue life can be predicted by testing the specimen in tension and monitoring the AE events. In high cycle fatigue, it was observed that the residual tensile strengths of the material did not change significantly with prior cyclic loading damages since the high cycle fatigue life was dominated by the crack initiation phase.
A New Look at the Stochastic Linearization Technique for Hyperbolic Tangent Oscillator
Authors: Colajanni P. , Elishakoff I. 
Published: January 2022

Abstract
Stochastic linearization technique is reconsidered for oscillator with restoring force in form of hyperbolic tangent. We show that a subtle error was made in the previously known procedure for derivation of the linearized system parameters. Two new error-free procedures, namely, those based on minimization of mean square difference between (a) restoring force or (b) potential energy of the original non-linear system and their linear counterparts, are suggested. The results of numerical analysis are shown.