bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic Response of a Heat Damaged Fiber-Resin Beam Subjected to Harmonic Forcing at the Tip
Authors: Nayeb-Hashemi H. , Harrison A. 
Published: November 2021

Abstract
A cantilever beam built of fiber-resin composite material and damaged by heat is evaluated for its dynamic response using numerical methods. The goal of research is to produce a diagnostic process in which dynamic response can be used to estimate the severity of damage to the beam. Research proceeds from formulation of the continuous media equations for vibration in a multiply segmented beam, to the development of finite element models for the beam. It is discovered that the results of these two methods are qualitatively different from the predictions of a lumped system model, in that the lumped system predicts that frictional damping should reduce the dominant frequency of vibration while the more elaborated models indicate that damping may increase the dominant frequency. It is further discovered that the size and location of damage (the geometry) are equally as important as the local stiffness and damping of the damaged region (the material properties). The results indicate that the dominant frequency of dynamic response is not a sufficient symptom for complete diagnosis of damage in the beam.
Bolt Head Fillet Stress Concentration Factors in Cylindrical Pressure Vessels
Authors: Srinivasan Gowri , Lehnhoff Terry F. 
Published: November 2021

Abstract
Linear three-dimensional finite element analysis (FEA) was performed on bolted pressure vessel joints to determine maximum stresses and stress concentration factors in the bolt head fillet as a result of the prying action. The three-dimensional finite element models consisted of a segment of the flanges containing one bolt, using cyclic symmetry boundary conditions. The flanges were each 20 mm in thickness with 901.7 mm inner diameter. The outer flange diameter was varied from 1021 mm to 1041 mm in steps of 5 mm. The bolt circle diameter was varied from 960.2 mm to 980.2 mm in steps of 5 mm. The bolts used were 16 mm diameter metric bolts with standard head and nut thickness. The threads were not modeled. The internal vessel pressure was 0.6895 MPa (100 psi).
Stress concentration factors in the bolt head fillet were calculated and they ranged from 3.34 to 4.80. The maximum stress in the bolt as well as the stress concentration factors in the bolt head fillet increase with an increase in bolt circle diameter for a given outer flange dimension. Keeping the bolt circle diameter constant, bolt stress and stress concentration factors in the bolt head fillet decrease with increase in outer flange diameter. The maximum stresses in the bolt were also calculated according to the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code and the Verein Deutscher Ingenieur (VDI) guidelines and compared to the results observed through finite element analysis. The stresses obtained through FEA were larger than those predicted by the ASME and VDI methods by a factor that ranged between 2.96 to 3.41 (ASME) and 2.76 to 3.63 (VDI).
Resonant Heat Transfer Enhancement by Acoustic Excitation in a Side-Heated Rectangular Enclosure
Authors: Kim Seo Young , Kim Sung Ki , Kang Byung Ha 
Published: November 2021

Abstract
Resonant transport enhancement by acoustic excitation in a sidewall-heated rectangular enclosure, in which natural convection flow is initially dominant, is considered. The enclosure is made of Plexiglas which dimensions are 30cm in height, 30cm in width and 30cm in depth. One sidewall of the enclosure is heated by an electrical foil heater and the other sidewall is maintained at a cold temperature by a cold water circulation. A woofer speaker is mounted on the bottom wall of the enclosure to generate pressure fluctuation inside the enclosure. All the walls of the enclosure are thermally insulated. The experimental results obtained indicate that there exists a resonant forcing frequency and velocity amplitude, which enhances thermal transport from the heated wall to the cold wall. It is also observed that, at the resonant state, the air temperatures inside the enclosure gather to an averaged air temperature by enhanced flow mixing. The relationship between the resonant frequency and the boundary layer wave along the vertical sidewall is discussed.
Turbulent Flow in Closely-Pitched Internally Enhanced Tubes
Authors: Ravigururajan T. S. , Srinivasan J. 
Published: November 2021

Abstract
General correlations are developed and verified for friction factor and heat transfer coefficients for single-phase turbulent flow in internally augmented tubes, with low pitch to height ratios. Data from existing investigations were collected for a wide range of tube parameters with e/d: 0.01 to 0.2; p/e: &lt; 8; α/90: 0.2 to 1.0, and flow parameters; Re: 2000 to 250,000 and Pr: 0.66 to 37.6. The data were applied to a linear model to get normalized correlations that were then modified to approach smooth tube correlations, as the roughness variables became very small. The correlations predicted 92% of data from an independent study on microfin tubes within ± 30%. For closely-pitched enhanced tubes, the proposed correlations predict heat transfer/friction factor with better overall accuracy and are suitable for different types of internal enhancements. The heat transfer increases with decreasing p/e ratio and increasing helix angle. The effects of roughness height and pitch on both friction and heat transfer are similar to that experienced in traditional enhancement design (p/e &gt; 8).
Development of Improved Corrosion Inhibitors for Ammonia-Water Absorption Heat Pumps
Authors: Hannon C. L. , Gerstmann J. , Mansfeld F. B. , Sun Z. N. 
Published: November 2021

Abstract
This paper describes the initial results of a research project to develop an improved corrosion inhibitor for the protection of carbon steel surfaces of ammonia-water absorption heat pumps and chillers using rare earth metal salt (REMS) compounds. Chromate compounds are currently used as corrosion inhibitors, but they are toxic, environmentally harmful, and their use is being phased out in many localities. An effective corrosion inhibitor is needed to make advanced ammonia-water absorption heat pump and chiller systems practical. Low-temperature screening tests were conducted to evaluate the potential of cerium salts, a class of REMS compounds, to act as an inhibitor for steel in ammonia-water solutions. Successful results from these tests led to high-temperature (HT) testing in an innovative test apparatus, which simulated a range of temperatures, ammonia concentrations, and phases typically found in ammonia-water absorption systems. HT testing further demonstrated the effectiveness of cerium nitrate as a corrosion inhibitor, and suggested that it may outperform the Chromate compounds currently used. An additional outcome of the project was the successful demonstration of a cerium based surface pretreatment procedure, termed cerating, as an additional corrosion protection feature. Cerated surfaces will prevent corrosion of steel surfaces and ammonia decomposition at steel surfaces. These results have lead to the concept of a dual corrosion protection strategy utilizing a cerium based solution inhibitor with a cerating surface pretreatment to prevent both corrosion and ammonia decomposition. This approach is presently being pursued in a more intensive study.
Experimental Characterization of Oil-Refrigerant Two-Phase Flow
Authors: Lacerda V. T. , Prata A. T. , Fagotti F. 
Published: November 2021

Abstract
Several phenomena occurring inside refrigerating systems depend on the interaction between the refrigeration oil and the refrigerant working fluid. Regarding the refrigeration cycle, good miscibility of oil and refrigerant assure easy return of circulating oil to the compressor through the reduction of the oil viscosity. Inside the compressor the lubricant is mainly used for leakage sealing, cooling of hot elements and lubrication of sliding parts. In the compressor bearing systems the presence of refrigerant dissolved in the oil greatly influences the performance and reliability of the compressor due to the outgassing experienced by sudden changes in temperature and pressure resulting in a two-phase mixture with density and viscosity strongly affecting the lubricant characteristics. A general understanding of the oil-refrigerant mixture flow is crucial in developing lubrication models to be used in analysis and simulation of fluid mechanics problems inside the compressor. In the present investigation the refrigeration oil flow with refrigerant outgassing is explored experimentally. A mixture of oil saturated with refrigerant is forced to flow in two straight horizontal tubes of constant diameter. One tube is used for flow visualization and the other is instrumented for pressure and temperature measurements. At the tubes inlet liquid state prevails and as flow proceeds the pressure drop reduces the gas solubility in the oil and outgassing occurs. Initially small bubbles are observed and eventually the bubble population reaches a stage where foaming flow is observed. The flow visualization allowed identification of the two-phase flow regimes experienced by the mixture. Pressure and temperature distributions are measured along the flow and from that mixture quality and void fraction were estimated.
Design and Analysis of a Miniature Reciprocating Compressor Driven by a Comb Drive
Authors: Hao Z. , Kapat J. S. , Chow L. C. , Sundaram K. B. 
Published: November 2021

Abstract
The design and working principle of a miniature reciprocating compressor driven by an electrostatic comb drive is presented and its basic parameters are discussed. The compressor, which is 6 mm in diameter and less than 0.5 mm in thickness, has a simple structure consisting of a compressor chamber, a corrugation diaphragm driven by a vertical comb-drive, and two active micro-valves. Using air as working medium, the simple mechanical system enables a compression ratio of 1.5. With a working voltage of 320V, the device gives flow rates of 2.7 ml/ min. The three-dimensional flow field in the chamber is also simulated using a commercial computational fluid dynamics software.
Intermittent Convective Heat Transfer for Ground-Source Heat Pump Design
Authors: Stevens James W. 
Published: November 2021

Abstract
An accurate estimate of the heat transfer from a buried pipe to the surrounding ground is essential for the design of the ground loop portion of a ground-source heat pump. Exact analytical solutions to this problem are complicated by the fact that heat pump systems rarely operate continuously. Complete numerical simulations of system designs can be carried out, but these are unwieldy and difficult to justify for initial scoping calculations, or for preliminary performance estimates. The purpose of this paper is to describe the development of simple algebraic correlations that can be used to approximate the intermittent overall heat transfer between a fluid flowing in an isolated buried pipe and the surrounding ground.
The correlations described in this paper were drawn from results of a numerical finite-difference analysis of a fluid flowing intermittently in a single round pipe and exchanging heat with the surrounding ground. The two-dimensional analysis was carried out for ranges of the parameters of intermittence factor, thermal diffusivity of the ground, and convective heat transfer coefficient at the fluid-wall interface. The surrounding ground is unbounded for the purposes of the analysis. The dimensionless heat transfer can be easily related to the overall thermal resistance between the flowing fluid and the ground far from the buried pipe.
It is found that the cycle average heat transfer is always lower for the intermittent case than for the continuous case, but that the average over just the active part of the cycle is always higher for any intermittent case than for the continuous case. The effect of the ground thermal diffusivity is largest when the heat transfer coefficient is large, and decreases with decreasing heat transfer coefficient. The range of heat transfer coefficients where isothermal wall conditions are approached is illustrated. Correlations for the operating average and cycle average total heat transfer are presented as functions of the thermal diffusivity, intermittence factor, and heat transfer coefficient.
Air-Side Heat Transfer and Pressure Drop Characteristics of Multi-Louver Fin and Flat Tube Heat Exchangers
Authors: Kim Man-Hoe , Bullard Clark W. 
Published: November 2021

Abstract
An experimental study on the air-side heat transfer and pressure drop characteristics for multi-louvered fin and flat tube heat exchangers has been performed. For 45 heat exchangers with different louver angles (15–29°), fin pitches (1.0, 1.2, 1.4 mm) and flow depths (16, 20, 24 mm), a series of tests were conducted for the air-side Reynolds numbers of 100–600, at a constant tube-side water flow rate of 0.32 m3/h. The inlet temperatures of the air and water for heat exchangers were 21°C and 45°C, respectively. The air-side thermal performance data were analyzed using effectiveness-NTU method for cross-flow heat exchanger with both fluids unmixed. The heat transfer coefficient and pressure drop data for heat exchangers with different geometrical configurations were reported in terms of Colburn j-factor and Fanning friction factor f, as functions of Reynolds number based on louver pitch. Correlations for j and f factors are developed and compared to other correlations.
The Dead State According to the Available Energy of Gibbs
Authors: Paulus David M. , Gaggioli Richard A. 
Published: November 2021

Abstract
For exergy calculations, it is necessary to choose a reference environment. Typically the ambient conditions surrounding the system are chosen. It will be argued here that the outdoor environmental conditions are not always correct as a reference “dead state” for evaluating a system or accounting. The constraints on the system must be considered when choosing this “dead state”. Gibbs’ original available energy concept allows a proper dead state to be chosen, especially when a system has no or only partial interaction with the environment. The application of this theory is demonstrated in this paper through the example of a hypothetical plant, which serves as both a chiller and a heat pump.
Second Law Aspects of Simplified Models for Sensible Thermal Storage
Authors: Homan K. O. 
Published: November 2021

Abstract
This paper presents results for entropy generation during the inflow of a low temperature stream into a sensible thermal storage vessel initially filled with a uniformly high temperature liquid. The level of internal entropy generation due to thermal mixing between the cold and hot liquid corresponds to losses in the usable fraction of the stored volume and therefore decreased efficiency. Empirically, the observed behavior of sensible storage devices spans the range of nearly mixed to well stratified. In this investigation, analytical models for these two limits, the fully mixed and ideally stratified conditions, are used to bound the entropy generation levels of the observed behaviors. A numerical model for stratified storage systems based on the one-dimensional convective energy equation which accounts for aspects of the observed thermal mixing is then examined in relation to the afore-mentioned limits. The results show that even at moderate throughflow rates, the fully mixed and ideally stratified limits are separated by orders of magnitude in terms of entropy generated. The empirically-based numerical model exhibits mixing levels midway between these two limits and thereby underscores the potential for significant improvements in efficiency. Examination of the numerical model shows the crucial importance of resolving the evolution of the interior thermal layer and the boundary heat fluxes in computing the entropy generation.
LO.CO.MO.DIA: Low Cost Monitoring for Diagnostic Purposes of a Small Scale CHP Plant
Authors: Fantozzi Francesco , Desideri Umberto 
Published: November 2021

Abstract
Small scale Internal Combustion Engines (ICE) powered Combined Heat and Power (CHP) plants are economically convenient when availability and efficiencies are above specified limits. Nevertheless these plants are often run without a monitoring device capable of data storing and trending and of performance evaluation.
This paper describes the setting up of a powerful low-cost monitoring system for the CHP plant that powers the School of Engineering of the University of Perugia. Data acquisition is performed by interfacing a Personal Computer (PC) to existing control panels via, serial port, and to a data acquisition board for those variables that are not measured by existing devices. Performance indexes are then calculated via software. Alarms and controls are stored as well to set up a database for diagnostic purposes.
The monitoring itself has already shown its troubleshooting capability in interface to maintenance personnel: history trending of variables speeds up the phase of failure identification because it eliminates those possibilities that are negated by cross referencing values of different variables.
Performance and Emission Analysis of a Variable Load Operated Gas Turbine
Authors: Bozza Fabio , Cameretti Maria Cristina , Marro Antonio , Tuccillo Raffaele 
Published: November 2021

Abstract
The authors present a methodology for the prediction of performance and emissions of a gas turbine under a wide range of load conditions. The engine, of the aero-derivative type, is employed in a natural gas recompression plant.
The paper deals, in its first part, with the reconstruction of the whole operating region of both the gas generator set and the power turbine including its matching with the centrifugal compressor for natural gas delivery in the pipeline. This phase also leads to an effective prediction of pollutant emission, with a chemical kinetics based sub-model.
Next, a refined CFD based simulation analyzes a number of operating cases, so providing a detailed insight of the actual phenomena which control the combustion chamber temperature distribution and the activation of the pollutant formation mechanisms.
Parametric Analysis of a Thermally Actuated Cooling System for Space Applications
Authors: Freudenberg K. , Lear W. E. , Sherif S. A. 
Published: November 2021

Abstract
Integration of new and existing technologies for thermal management will be required to meet the challenges associated with the increased need for an efficient, lightweight, heat rejection system. Subsystem design requirements, such as thermal and mass management, must be brought into me design cycle to establish an optimal configuration. This paper provides a parametric analysis that determines a range of parameters under which a proposed system becomes viable from a weight management standpoint. The analysis can be applied to essentially any space-operated thermally-actuated heat pump with power and refrigeration subsystems. By applying the techniques demonstrated in this paper, designers can identify and optimize conceptual configurations during the initial prototype development stages to reduce payload weight and increase financial savings.
Investigation of a Novel Gas Turbine Cycle With Coal Gas Fueled Chemical-Looping Combustion
Authors: Jin Hongguang , Ishida Masaru 
Published: November 2021

Abstract
A new type of integrated gasification combined cycle (IGCC) with chemical-looping combustion and saturation for air is proposed and investigated. Chemical-looping combustion may be carried out in two successive reactions between two reactors, a reduction reactor (coal gas with metal oxides) and an oxidation reactor (the reduced metal with oxygen in air). The study on the new system has revealed that the thermal efficiency of this new-generation power plant will be increased by approximately 10–15 percentage points compared to the conventional IGCC with CO2 recovery. Furthermore, to develop the chemical-looping combustor, we have experimentally examined the kinetic behavior between solid looping materials and coal gas in a high-pressure fixed bed reactor. We have identified that the coal gas chemical-looping combustor has much better reactivity, compared to the natural gas one. This finding is completely different from the direct combustion in which combustion with natural gas is much easier than that with other fuels. Hence, this new type of coal gas combustion will make breakthrough in clean coal technology by simultaneously resolving energy and environment problems.
Prediction of Radiative Heat Transfer in a 2D Enclosure With Blocked-Off, Multi-Block, and Embedded Boundary Treatments
Authors: Byun Do Young , Baek Seung Wook , Kim Man Young 
Published: November 2021

Abstract
A prediction of radiative heat transfer in a complex geometry was performed using different boundary treatments such as blocked-off, spatial-multiblock, and embedded boundary methods. The formulation of embedded boundary treatment for finite volume was derived here. The finite-volume method (FVM) was used to model the radiative transfer in an absorbing and emitting medium which is maintained at an isothermal condition and enclosed by cold and black walls. While the body-fitted grid system was used for the spatial multi-block treatment, the Cartesian grid system was chosen for the others. Their results were compared and discussed for three different cases including trapezoidal enclosure, semi-circular enclosure with internal block, and incinerator-shaped enclosure. The accuracy obtained by application of each treatment was shown to be highly satisfactory. Consequently, each treatment was suitable for modeling the radiative heat transfer in the complex geometry. However, the solution obtained by the blocked-off treatment has yielded some errors compared with the others, since the Cartesian grid used in the blocked-off treatment could not exactly configure the complex boundaries. Especially, the radiative heat flux on the non-orthogonal wall was largely underestimated due to its stepwise description of the wall.