bluuebunny/crossref_metadata_2025 huggingface dataset:
Robust Mask-Layout and Process Synthesis Through an Evolutionary Algorithm
Authors: Ma Lin , Antonsson Erik K.
Published: November 2021

A method for automated mask-layout and process synthesis for MEMS is presented. The synthesis problem is approached by use of a genetic algorithm. For a given desired device shape, and several fabrication process choices, this synthesis method will produce one or more mask-layouts and associated fabrication process sequences (which when used can generate shapes close to the desired one). Given complicated device shapes and wide range of fabrication process possibilities, the designer may encounter difficulty producing the right mask-layout and fabrication procedure by experience and trial and error. An automated synthesis tool like this will be helpful to the designer by increasing the efficiency and accuracy of the design of MEMS devices.
Acoustically-Driven Microfluidic Systems
Authors: Wang Amy W. , Benett William J. , Tarte Lisa A. , Venkateswaran Kodumudi S.
Published: November 2021

We have demonstrated a non-contact method of concentrating and mixing particles in a plastic microfluidic chamber employing acoustic radiation pressure. A flow cell package has also been designed that integrates liquid sample interconnects, electrical contacts and a removable sample chamber. Increased antibody binding to magnetic porous glass beads was observed in the presence of acoustic mixing due to improved mass transport. Concentration of glass and polystyrene beads using acoustic radiation pressure was also demonstrated.
Electroosmotic Flow Control in Complex Microgeometries
Authors: Dutta Prashanta , Beskok Ali
Published: November 2021

A high-order (h/p type) spectral element method is developed, and verified for numerical simulation of combined electroosmotic and pressure driven flows in complex microgeometries. Analytical relations for wall shear stress, velocity and pressure distributions in straight channels are obtained. The electrokinetic pumping action is demonstrated. Electroosmotic flows in groove-channels, microchannel junctions and Y-split junctions are analyzed. Precise flow adjustment and separation control techniques using the electroosmotic forces are demonstrated. In the Stokes flow regime, the flow control is shown to have linear dependence on the magnitude of the external electric field. Hence, the electroosmotic forces can be used as linear actuators for various microfluidic applications.
Optimization of DNA Microsensor Arrays for Biological Detection
Authors: Gau Jen-Jr , Lan Esther H. , Dunn Bruce , Ho Chih-Ming
Published: November 2021

This paper describes the characterization and optimization of a reusable DNA microsensor array for rapid biological agent detection developed in previous publications. (Fig.1) [1–3] This MEMS based DNA sensor utilizes a standard three-electrode electrochemical cell configuration with novel micro fabricated structure design to minimize non-specific binding. The sensor module is easily to be adapted to various protocols and can be used for rapid detection of macromolecules (DNA, RNA) from targets such as uropathogenic Escherichia coli (E. coli) in urine and microorganisms causing otitis media (middle ear infection). Less than 105 E. coli cells can be detected from the urine sample of a patient with urine tract infection. The sensitivity is enhanced by appropriate sensor characterization and surface modification. The total detection time including sample preparation can be reduced to 25 minutes by using a POD conjugated oligonucleotide.
Magneto-Thermo-Fluidic (MTF) MEMS by Direct-Write (DW) Laser Micro-Fabrication (LμF)
Authors: Vakanas George P. , Tseng Ampere A. , Winer Paul
Published: November 2021

Keeping up with the highlight topic of this year’s ASME MEMS Symposium 2000 “Beyond Traditional Barriers”, this paper reports on operational principles, scaling, modeling and fabrication issues for magneto-fluidic MEMS. The research is an integral part of the on-going Laser Fabrication Program at Arizona State University. It is the premise of this paper that novel MEMS devices and applications can evolve by integrating materials with unique properties in new micro device designs (Grimes, 1997). Laser processing techniques, for 5μ-thick magnetic films on silicon, have already been reported elsewhere by the same authors (Vakanas et al, 2000). The focus of the current work is on expanding the applications envelop of laser-fabricated microstructures on magnetic thick films to enable new high-volume semiconductor and MEMS devices. Research results are presented in the form of preliminary laser-based rapid prototyping and fabrication (RP&F) as well as comparative taxonomies of operational principles and applications in microfluidics and micromagnetics, leading to the conceptual design of micro and meso -scale MHD and MTF devices. The paper concludes with the on-going research activity and remaining challenges.
Trends in the Energy and Engineering Industry From a Nuclear Power Perspective
Authors: Nordahl James H.
Published: November 2021

The purpose of this paper will be to discuss the role of nuclear power in world energy production during the 21st century. Nuclear power is currently a significant source of the global electricity supply, providing approximately 16% of the world’s electricity, and world consumption of nuclear power is continuing to grow. Worldwide nuclear capacity is projected to increase from 349 gigawatts (in 1998) to 368 gigawatts in 2010. Much of this near-term increase in nuclear capacity is due to aggressive plans for nuclear capacity expansion in Asia.

Longer term high growth projections for nuclear power include assumptions of limited reactor aging effects, with more reactors operating after license renewals. In early 2000, the USNRC issued the first license renewals for nuclear power plants, for a 20 year extension beyond the expiration of the initial license term. In addition, utilities have already notified the USNRC of plans to submit renewal applications for more than 20 units by 2003. License renewal is expected to be an attractive option for companies as the most inexpensive means of future electricity generation.

Another factor pointing towards the positive prospects for nuclear power in the future are the substantial improvements seen in plant safety, reliability and output over the last two decades. Due to improved management practices, higher reliability and output, and shorter refueling outages, the average production cost of US nuclear power plants has steadily decreased over the last five years. Based solely on economic factors, most US nuclear units should be able to compete in a competitive electricity market.

Many additional factors point to nuclear power as an energy source which will become increasingly important in the 21st century. These factors include environmental considerations such as carbon emissions from fossil fuels, reduced waste quantities produced by nuclear power, and the security of supply of uranium reserves.
Solar Thermal Power Technology: Present Status and Ideas for the Future
Authors: Goswami D. Yogi
Published: November 2021

Rapid industrial developments and the resulting need for additional electrical power in major population centers of the world such as India, China and Brazil, have created a need and an opportunity for power from clean and renewable sources of energy. The need to develop and use resources such as solar energy, wind, and biomass has assumed even greater importance in view of the concern for environmental damage that could occur if all of the anticipated power demand in the expanding economies were met by fossil fuels.

Recent advances in wind energy technology have made it economically competitive with fossil-fuel-generated electricity, wherever sufficient wind resource is available. Solar thermal power can be economically competitive when compared with coal-generated electricity if environmental costs are accounted for (Goswami, 1994). However, without considering such environmental costs (a realistic scenario for developing countries like India and China) solar power may not be competitive at present because of the high capital costs. The potential exists for reducing these expenses by improving the performance of thermal power systems. The system performance can be improved by employing new and innovative ideas in thermal power cycles. This article reviews some of these ideas and research needs to make solar thermal power cost competitive.
A Constitutive Model for Cyclic Loading and Relaxation
Authors: Garmestani H.
Published: November 2021

A new model is proposed which incorporates inelastic flow during cyclic loading and relaxation processes. The model is an extension of Hart’s constitutive model for inelastic flow and is based on the non-steady state condition for the frictional glide process. A new state variable is introduced here as a microhardness parameter which represents the strength or the average lifetime of the mobile dislocations relative to the frictional glide viscous drag process. The evolution of the microhardness parameter is very similar to that proposed for the hardness parameter except that the recovery plays a major role. The results show that the model can predict the transient behavior for both cyclic loading and the reloading phenomena during inelastic deformation and load relaxation.
Dynamics of Vehicles Subjected to Extreme Steering
Authors: Forouhar Farshid A.
Published: November 2021

This simulation study examined the influence of first order suspension design attributes on minimum lateral acceleration required to overturn a vehicle (lateral acceleration at roll, “LAR”). When subjected to extreme “step-steer” maneuvers, many sport utility vehicles (SUVs) tip-up on two wheels. Lateral accelerations achieved during these tests, however, rarely approach corresponding values of LAR. Moreover, in many cases, transient dynamics during initial phases of the tests do not explain this discrepancy. To address why vehicles overturn in such circumstances, a lateral/directional model was developed. Phase-plane analyses of lateral/directional response uncovered an oscillatory mode of response that explains observed oscillations that, in turn, significantly influence the likelihood of overturn. Results of analyses also indicated inherently high sensitivity to initial conditions of the final outcome of extreme step-steer maneuvers.
An Optimum Design Approach Using Active and Semi-Active Suspensions for 3-D Vehicle Models
Authors: Bouazara M. , Richard M. J.
Published: November 2021

The primary purpose of this paper is to analyze the effects of vibrations on the comfort and stability of road vehicles as observed in the variation of different parameters such as suspension coefficients, road disturbances and the seat position. The conducting of this study required the development of a mathematical model to simulate the dynamic behavior of a 3-D vehicle. This model makes it possible to efficiently use various types of non-linear suspensions such as active and semi-active suspensions. The results obtained from the simulation of the 3-D vehicle demonstrated that the use of active and semi-active suspension models on road vehicles proved to be beneficial for comfort without unduly compromising stability.
Design Sensitivity Analysis Applied to Injection Molding Process: Injection Pressure and Multi-Gate Location Optimization
Authors: Kabanemi Kalonji K. , Hétu Jean-François , Derdouri Abdessalem
Published: November 2021

In this work, we develop a numerical simulation method to optimize the injection molding process using the design sensitivity analysis (DSA). The optimization concerns the filling stage and focuses on the number and location of gates in a mold cavity as well as the injection pressure, considered as one of the key processing parameters, in order to minimize the fill time. Since the problem to be solved involves transient flow with free surfaces, the direct differentiation method is used to evaluate the sensitivities of the Hele-Shaw, filling fraction and the energy equations with respect to the design variables used in the analysis. The mesh domain parameterization is coped with using B-spline functions. Sensitivity equations are solved by means of finite element method. The proposed numerical approach is combined with the sequential linear and quadratic programming method of the DOT optimization tools to find the new design variables at each iteration. Starting with any initial gate locations and injection pressure profile, the method enables us to find the optimal gate locations together with the optimal injection pressure profile. Finally, numerical results involving complex mold geometries are presented and discussed to assess the validity and robustness of the proposed method.
Identification of Preform Permeability Distribution in Resin Transfer Molding
Authors: Minaie B. , Chen Y. F. , Mescher A. M.
Published: November 2021

This paper presents a numerical scheme that directly calculates the permeability field of the preform during the Resin Transfer Molding (RTM) process. The measured filling front locations as well as the corresponding inlet conditions are used in the proposed scheme to calculate the permeability field. The proposed scheme employs a numerical optimization algorithm to minimize a cost function that leads to the permeability filed of the preform. A time step independent RTM filling algorithm is utilized as a computational kernel to generate the cost function for the subsequent iterative minimization. The proposed permeability identification scheme is applied to test problems that involve isotropic and anisotropic permeability distribution within the perform. The results from these test problems verify the applicability of the proposed scheme.
CAE Simulation and Verification of Wire Sweep for BGA 436
Authors: Jong Wen-Ren , Chen You-Ren
Published: November 2021

The microelectronics industry continues to grow rapidly in size and importance. As thinner and denser IC packages become, packaging process becomes more challenging and troublesome. The ball grid array (BGA) technology uses substrate and solder balls to replace the traditional leadframe, which offers many advantages over fine pitch technology. These include better assembly yield, superior electrical performance, and higher I/O density. However, the high density of bonding wires form a separating layer which will hold back the molding compound flowing through these regions.

The paper presents the simulation of melt-front advancement and wire sweep for BGA 436. The results has been verified by the experimental studies. It is found that the high-density of wires has played a very important role in performing the CAE analysis. It shows that the melt-front advancement can be precisely predicted by CAE simulation software with proper consideration of wire density. With the accurate simulation of melt-front advancement, the CAE results can be further used to perform further engineering analysis. The wire sweep of the package demonstrates the use of CAE analysis, which also shows very good agreement with the experimental study.
Stress Intensity Factors for Cracks Within and Near to Bondlines in Soft Incompressible Materials
Authors: Smith C. W. , Gloss K. T. , Constantinescu D. M. , Liu C. T.
Published: November 2021

Using a polyurethane photoelastic material, thick test specimens of several configurations with bonded end tabs are examined for measuring stress intensity factors (SIFs) for cracks within and near to bondlines in bonded photoelastic models. Effects of specimen height, glued end tabs, bondline and crack size and location are studied and analyzed using a two parameter model for extracting the SIFs and results are compared with cracked, homogeneous model results.
Mixed Mode I/II Fracture and Fatigue Crack Growth Along 63Sn-37Pb Solder/Brass Interface
Authors: Nayeb-Hashemi H. , Yang Pinghu
Published: November 2021

Solder joints are extensively used in electronic packaging. They provide critical electrical and mechanical connections. Single edge notched sandwich specimens, which were made of two blocks of brass joined with a 63Sn-37Pb solder layer, were prepared for fatigue and fracture study of the joint under mixed mode loading. Mode I and mixed mode I/II fracture toughness, fatigue crack thresholds, and fatigue crack growth rates (FCGR) were measured at room temperature using a four point bending test setup.

It was found that the fracture toughness of the joint increased and FCGR decreased upon the introduction of mode II component. The interface fracture toughness was higher than that of reported for pure solder. The data of FCGR correlated well with the power law relation of da / dN = C* (ΔG)m. It was also observed that both fracture toughness and FCGR were a function of thickness of solder layer. When the solder layer thickness increased from 0.1mm to 1.0mm, the fracture toughness decreased substantially and FCGR increased slightly.

For mode I loading, fatigue crack propagated inside the solder layer. However, for mixed mode loading, once a crack initiated, it changed its direction toward the interface and then propagated along the interface. These observations were related to local mode I and mode II stress fields. Fracture surface showed sign of rubbing under mixed mode loading with elongated cavities at the crack tip. However, under mode I loading, fracture surface was covered with equi-ax voids.
Prediction for Post-Forming Spring Back of CICC in the Superconducting Tokamak Fusion Device via Virtual Manufacturing
Authors: Suh Yeong Sung , Ahn Jong Sung , Choi Sun Woong , Park Hyun Ki , Kim Yong Jin , Kim Kee Man
Published: November 2021

To construct the CICC for the superconducting Tokamak fusion device, the 3-roll bending, that inherently has a difficulty to form the coil with accurate radius of curvature, is used for continuous winding. In order to obtain precise dimension, a trial-an-error operation is inevitable. To reduce the effort of tryout, a relation between travel of the bending roller and spring back displacement was obtained via virtual manufacturing. The radius of CICC after forming was expressed as a function of the bend-roll travel. Next, the variation of the CICC cross-section (reduction of the conduit cross-section) was investigated during the first turn and during conduit bending with largest curvature. With largest curvature, the cross-sectional area was not much reduced. Finally, the residual stress on the CICC before roll bending was measured in order to examine the influence of the original residual stress on the final deformation behavior. The principal stress and von Mises stress were measured at the surface of CICC using specially designed strain gauge. The measured values were considered in the virtual forming. The results indicate that the residual stresses generated during the fabrication of the CICC (before coiling) do not have much influence on the final stress state.
Yield Function for Structural Porous Metals
Authors: Alam M. Khairul , Ahmed Shatil S. , Kuriger Rex J.
Published: November 2021

To reduce weight while maintaining high specific strength, Structural Porous Metals (SPM) are being developed. These materials are alloys containing an inert gas in distributed pores at very high pressures. The pores of gas are incorporated into SPM during processing. Since the pores are closed pores at high pressures, the material can be processed by standard methods such as rolling or forging without collapsing the gas pores. These materials must be treated as a composite material with special deformation behavior under applied stresses. It should be noted that, unlike solids, shear stresses can not be present in a gas medium in static equilibrium. This paper deals with the determination of the yield stress of structural porous metals. The yield function is calculated from the principle of virtual work. In this approach it is assumed that a constant amount of energy needed to deform the material to the yield point. In the case of SPM, the yield function must include the work needed to deform the gas pores as the material yields. The energy of deformation for the gas in the pores is evaluated according to the ideal gas law. The total work done in deforming the gas and the solid metal is taken into account in determination of the yield function of SPM. The result of the analysis is then compared with classic yield functions for monolithic alloys.
Effect of Promoter Orientation on Enhancement of Heat Transfer From Vertical Fins
Authors: Onbasioglu Seyhan U. , Onbasioglu Huseyin , Egrican Nilufer
Published: November 2021

The promoters redirect the flow and enhance the heat transfer both in laminar and turbulent cases. In the present study, the special care has been intensified first on the parameters such as the height and the pitch of the promoters and then the orientation of the repeated promoters with varying heights has been investigated. It is concluded that the enhancement of the heat transfer is sensitive to all of the parameters. Meanwhile, turbulence has been observed exceeding a certain value of the promoter height and the separation region occurring along the downstream plate has been analyzed. The flow and temperature fields have been obtained by means of a modified k-epsilon turbulence model developed for the present case. Results of the 3-D computations compare well with the experimental observations.
Heat Transfer Investigation of an Offset Strip Fin Using Liquid Crystals
Authors: Shin Seunghoon , Lavine Adrienne S.
Published: November 2021

The heat transfer characteristics of an offset strip fin are investigated by the transient liquid crystal method. It is found that there are various flow patterns that may occur, such as separation, reattachment, flow acceleration, expansion, and trailing vortex, and that the heat transfer is directly influenced by them. These flow patterns vary depending on the fin geometry and Reynolds number. For a sparsely stacked fin array (strip thickness-to-fin pitch, t/D < 0.1), the heat transfer pattern is close to a flat plate in a free stream such that the heat transfer is high at the leading edge and decreases along the plate. A distinct pattern change occurs at ReDh ≈ 2300. The heat transfer is high at the leading edge, but decreases rapidly over the first 10–20% of the strip, then increases to a maximum at 25–30%, then decreases again over the rest of the strip. The maximum at 25–30% of the strip indicates flow reattachment there. The same trend is found in a densely stacked fin array (t/D = 0.25) but the pattern change occurs at much lower Reynolds number (ReDh ≈ 800). The influence of flow reattachment is comparable at these Reynolds numbers in both of the fin arrays but it becomes more significant in the densely stacked fin array as Reynolds number increases. It appears that this is due to more dominant flow separation and reattachment, caused by an adverse pressure field near the leading edge of the strip in the densely stacked fin array. The results indicate the importance of the fin pitch in understanding the flow and heat transfer characteristics of offset strip fins.
Absorption-Compression Heat Pump for Space Heating and Cooling Using Organic Fluids
Authors: Nogues M. , Valles M. , Bourouis M. , Boer D. , Coronas A.
Published: November 2021

The combination of compression and absorption technologies can provide heat pumps with high efficiency and a wide operating range. The aim of this research project lies in the development and testing of a gas-fired double effect absorption-compression heat pump working with organic pairs for space heating and cooling.

For these applications, the use of suitable organic working pairs makes possible heat pump operation at higher temperature lifts than that of conventional water-lithium bromide systems. In our research, the combination Methanol and Tetraethylenglycoldimethylether (TEGDME) has been selected as working pair. The heat pump is targeted to operate in both cooling and heating modes. Therefore, the basic structure of the heat pump is an absorption-compression double effect cycle for cooling mode, that can be switched to a single effect cycle, in order to achieve the required higher temperature lift for the heating operation.

The nominal working conditions for cooling are 5°C at the evaporator and 35 to 45°C at me absorber-condenser. These conditions can be achieved with a double effect absorption-compression cycle. Different solution circuit flow configurations as serial, parallel and reverse flow have been considered. The heating operation of the heat pump aims at a temperature of the useful delivered heat between 45 and 60°C for an evaporator temperature of 0°C. In order to achieve the required temperature lift with an attractive performance (COP in the heating mode higher than unity), the unit should operate as a single effect absorption-compression heat pump. The performance analysis was based on a thermodynamic model considering the equilibrium properties of the working pair and energy and mass balances in the different components. Results in both operating modes have been evaluated in terms of the solution flow rate, the coefficient of performance COP and the primary energy ratio PER. Very interesting performances are found even for high temperature lifts. The serial flow configuration has been selected due to its good performance and technological aspects.

This work forms part of the project CLIMABGAS. A prototype of this heat pump is under construction for a cooling power of 20 kW and a heating power of 24.5 kW.
Experimental Study of the Absorption Process of Organic Fluids in a Plate Heat Exchanger
Authors: Vallès M. , Bourouis M. , Boer D. , Nogués M. , Coronas A. , Villanova A.
Published: November 2021

In this paper, the absorption process in a plate heat exchanger with organic fluids has been experimentally investigated. It is well known that the absorber is the key component in absorption systems. The absorber studied consists of an adiabatic mixing chamber and a plate heat exchanger. In the mixing chamber, the solution that is poor in refrigerant is sprayed on the vapor refrigerant. Then, the two-phase mixture that is formed enters into the plate heat exchanger where the absorption process is completed by cooling the solution.

Experiments have been performed using the organic fluid mixtures: Methanol-Tetraethyleneglycol dimethylether (TEGDME) and Trifluoroethanol (TFE)-TEGDME. The effect of the solution mass flow rate, the absorber pressure and the cooling water temperature on the absorber performance has been analyzed. The results obtained are discussed in terms of the absorber load, subcooling of the solution at the outlet of the absorber, overall heat transfer coefficient and absorbed mass flux. The information achieved should serve to understand better the absorption process for such mixtures and design an absorber using plate heat exchangers for air conditioning applications.
Heat Transfer in an Oil-Injected Screw Compressor and in Its Discharge Pipe
Authors: Hammerl Klaus , Moser Johannes
Published: November 2021

Because of the extremely inhomogeneous oil distribution and the very short contact time of a few milliseconds between gas and oil, the heat transfer between the two phases inside a liquid injected screw compressor is strongly incomplete and the compression of gas runs almost adiabatic. To be able to judge the heat transfer inside the compressor, the air-oil mixture is withdrawn from the compressor and separated in such a way that the increase of the enthalpy of the oil can be determined. The final air temperature after compression is calculated via an energy balance. A similar schema is applied to the annular two phase flow in the discharge pipe following the compressor. The results show that the heat transfer from oil to air occurs mainly inside the pressure piping and the oil separator.
An Experimental and Computer Simulation Investigation of the Performance of a Heat Pump for Stratospheric Balloon Missions
Authors: Jiang Haobo , Borkowski Chris , Radermacher Reinhard , Didion Jeffrey
Published: November 2021

An environmental control system based on a heat pump was designed and built to provide a constant temperature environment for electronic packages used on stratospheric balloon missions. The major challenges in the design of this system are in creating the control hardware and control strategies for the heat pump, which is subjected to varying loads and environmental sink temperatures. The initial experiment and modeling effort, which will be used to develop an optimized hardware design and control strategy, is described.

An experiment was implemented to simulate the operating conditions the heat pump would experience in the stratosphere. The rarified environment of the stratosphere requires that the primary mode of heat exchange with the environment be radiative in nature. The heat pump was placed in a vacuum chamber to: 1) investigate the effect of the radiative coupling between the heat pump radiator/condenser and the environment (thermal source/sink) on the system performance, charge requirements, and temperature control of the evaporator, 2) investigate the effect of radiative cooling from the compressor shell on the compressor performance, and 3) determine if the compressor electronics heat exchanger could be sufficiently cooled by the heat pump suction line.

In addition to the experiment, a simple computer model was created to simulate the experimental heat pump. This model is compared against the experiment. The computer simulation predicted the performance of the heat pump at different heat loads, compressor speeds, space temperatures, and refrigerant charges. The predicted electric power agreed with the experimental results within −2% and 12%, and with evaporator and condenser temperature variations between 1K to 2K, and 3.5K to 6K respectively.
Optimal Design and Operation of a Hybrid Gas/Electric Chilled Water Plant
Authors: Ellis Michael W. , Permana Adhi , Ellis Kimberly P.
Published: November 2021

Large commercial buildings and many industrial facilities use central chilled water plants to provide chilled water for air conditioning and process cooling requirements. Equipment for producing chilled water can be driven by electric motors, natural gas fueled engines, or by thermal energy through absorption cooling cycles. The chilled water plant equipment is expensive and pricing structures for electricity, natural gas, and thermal energy are often complex. In order to minimize the cost associated with owning and operating a central chilled water facility, the design approach and operating strategy must consider equipment cost, cooling requirements for the facility, utility cost structures, and equipment performance characteristics.

A mathematical model of the chilled water plant design and operation problem is developed. The model minimizes the life cycle cost of a chilled water plant through selection of chilled water plant equipment and specification of an optimal operating schedule for the equipment. The problem is formulated as a mixed integer linear programming problem where non-linear chiller performance curves are transformed into linear constraints through the use of integer variables. The model is decomposed into design and operation problems. The design problem is solved heuristically with the underlying operational problem solved using branch and bound techniques. The solution approach is demonstrated through application to a case study. Results indicate that the approach can be used to establish a plant configuration and an operating strategy for all-electric, all-gas, and hybrid chiller plant configurations with the optimal design dependent upon the utility cost structure.
Analysis of Extended Environomic Cost Influence on Conventional Energy Systems Design
Authors: Borchiellini R. , Calì M. , Santarelli M.
Published: November 2021

In the paper the authors analyse how the application of an extended environomic procedure, based on charges linked to the pollutant activities of energy systems, influences the energy behaviour of energy systems.

If in the economic balance of an energy plant a cost is assigned only to the pollutant emissions (Environmental Cost), it can be shown that this choice allows a good promotion of the abatement devices and of the switching fuel approach, but the efficient utilization of energy resources is not sufficiently promoted.

The extended approach, here analysed, takes into account both the pollutant emissions and the inefficient use of energy resources. In the proposed method, on the basis of thermodynamic considerations, a cost is assigned to the exergy rate destroyed inside the system and to the exergy flows rejected into the biosphere with the plant wastes (Efficiency Penalty).

Many calculations have been developed using different sets of both the Environmental Cost and the Efficiency Penalty; assigning different weights to them. The calculations have been applied to a 30 MWel gas turbine cogeneration power plant (CGAM), and to an existing 350 MW combined cycle, considering the pollutant emissions of CO, NOx, SOx and CO2. The obtained results show that this approach can become a real energy policy instrument: in fact it allows to stimulate high efficiency design of conventional plants and advanced high-efficiency low-pollutant energy systems, becoming an opportunity to disseminate advanced technologies that still have difficulties to compete in the energy market due to their high investment costs.
Enhancing the Steam-Reforming Process With Acoustics: A Theoretical Investigation of Potential Benefits for Application in Fuel Cell Vehicles
Authors: Erickson Paul A. , Roan Vernon P.
Published: November 2021

This paper provides a theoretical basis for the investigation of using acoustic waves as a means of enhancing performance in conjunction with the hydrocarbon fuel steam-reforming process for application in fuel cell vehicles. In order to minimize liabilities associated with steam-reforming, a novel reforming enhancement is being investigated.

A reformation process that utilizes acoustic fields in critical fluid paths is introduced. Potential benefits of using acoustic fields in the reformation process are decreased effective space velocity, an increase of convective heat transfer rates, and increased specie mixing that would help produce an increase in capacity and overall reaction rate for a given reformer volume. The proposed acoustic enhancement should result in some combination of quicker start up times, faster dynamic response, smaller size and lower weight.
Enhancing Fuel Cell/Gas Turbine Hybrid Power Systems via

Reduced

Fuel Utilization Within Indirect Internally Reforming (IIR) Fuel Cell Stacks
Authors: Haynes Comas , Wepfer William J.
Published: November 2021

A system design process innovation is reported, in conjunction with a fuel cell/ gas turbine hybrid power system (HPS). Lowering cell stack fuel utilization increases system power generation and cost effectiveness. This occurs with minimal penalty to the system’s lofty efficiency. The cell stack produces more power at lower fuel utilizations, because reactant flows to the stack actually increase. The bottoming gas turbine also increases in power production, because a greater amount of unreacted fuel fires it. Since power generation installation cost is normalized per unit capacity rating (e.g., $/kW), increasing power production is a viable means of lowering capital costs. At lower cell stack fuel utilizations, enhanced regenerative effects within the HPS counteract the increasing prevalence of combustion. System efficiency thus remains stable. The adage that best system performance occurs at the highest cell stack fuel utilizations is based on “parallel plant” logic. The investigators have shown, however, that such reasoning is not necessarily applicable to these HPS designs (which incorporate indirect internal reformation). A process patent is pending.
Thermoeconomic Analysis of Power Plants With Integrated Exergy Stream
Authors: Kim Duck-Jin , Lee Hyun-Soo , Kwak Ho-Young , Hong Jae-Ho
Published: November 2021

Exegetic and thermoeconomic analysis were performed for a 500-MW combined cycle plant and a 137-MW steam power plant without decomposition of exergy into thermal and mechanical exergy. A unit cost was assigned to a specific exergy stream of matter, regardless of its condition or state in this analysis. The calculated costs of electricity were almost same within 0.5% as those obtained by the thermoeconomic analysis with decomposition of the exergy stream for the combined cycle plant, which produces the same kind of product. Such outcome indicated that the level at which the cost balances are formulated does not affect the result of thermoeconomic analysis, that is somewhat contradictory to that concluded previously. However this is true for the gas-turbine cogeneration plant which produces different kinds of products, electricity and steam whose unit costs are dominantly affected by the mechanical and thermal exergy respectively.
The Combined First and Second Laws of Thermodynamics and Exergy Analysis
Authors: Adebiyi George A.
Published: November 2021

A novel approach is proposed for combining the first and second laws of thermodynamics for systems undergoing arbitrary, non-reversible processes. A reference environment at an intensive state (p0, T0) is assumed, and combination of the two laws of thermodynamics yields the familiar equations used in the exergy analysis of processes.

The application of the laws of thermodynamics was made first to non-flow processes involving closed systems. An extension to the control volume and flow processes was carried out via the use of the Reynolds transport theorem.
Theoretical and Experimental Evaluation of the EvGT-Process
Authors: Lindquist Torbjörn O. , Rosén Per M. , Torisson Tord
Published: November 2021

In recent years the interest for new advanced thermodynamical gas turbine cycles has increased. One of the new designs is the evaporative gas turbine cycle. A lot of effort worldwide has been put into predicting the possible efficiency, pollutants, and dynamic behaviour of the evaporative gas turbine cycle, but all results so far have been affected by uncertain assumptions. Until now this cycle has not been demonstrated in a pilot plant. The purpose of this work has been to identify the potential of this cycle, by erecting a pilot plant at the Lund Institute of Technology. The project was financed on a 50/50 basis from the Swedish National Energy Administration and the industrial partners.

Three different thermodynamical cycles have been tested in the pilot plant: the simple, the recuperative, and the evaporative cycles. The final pilot plant roughly consists of a 600 kW gas turbine, a hydraulic brake, a recuperator, a humidification tower, an economiser, and a flue gas condenser. All layout and functional analysis were made within the project. The pilot plant is, however, optimized neither for best efficiency nor for best emissions. It has only been built for demonstration purpose.

It has been shown from the performance tests that the efficiency for the simple, recuperative, and evaporative cycles are 22, 27, and 35%, respectively, at rated power output. The NOx emissions were reduced by 90% to under 10 ppm, and the UHC and CO were not measurable when running the evaporative cycle at rated power output. The performance of the humidification tower was better than expected. The humidified air out from the humidification tower is always saturated. The pinch point, i.e. the temperature difference between the outcoming water from the humidification tower and the saturation temperature of the incoming air, is around 3°C. The water circuit was closed, i.e. there was no need for additional water, when the flue gases after the flue gas condenser reached a temperature of 35° C.

The inhouse heat balance program, used for both cycle optimization and evaluation, has been verified. The evaporative gas turbine cycle has, when optimized, at least the same efficiency as the best combined cycle today, based on the same gas turbine. The evaporative cycle will also show very good performance when used in small scale power plants.
An Integrated Approach for Gas Turbine Engine Simulation
Authors: Xie Zhiwu , Su Ming , Weng Shilie
Published: November 2021

The static and transient performance of a gas turbine engine is determined by both the characteristics of the engine components and their interactions. This paper presents a generalized simulation framework that enables the integration of different component and system simulation codes.

The concept of engine simulation integration and its implementation model is described. The model is designed as an object-oriented system, in which various simulation tasks are assigned to individual software components that interact with each other. A new design rationale called “message-based modeling” and its resulting class structure is presented and analyzed.

The object model is implemented within a heterogeneous network environment. To demonstrate its flexibility, the codes that deal with different engine components are separately programmed on different computers running various operating systems. These components communicate with each other via a CORBA compliant ORB, which simulates the overall performance of an engine system.

The resulting system has been tested on a Local Area Network (LAN) to simulate the transient response of a three-shaft gas turbine engine, subject to small fuel step perturbations. The simulation results for various network configurations are presented. It is evident that in contrast to a standalone computer simulation, the distributed implementation requires much longer simulation time. This difference of simulation efficiency is analyzed and explained.

The limitations of this endeavor, along with some future research topics, are also reported in this paper.
Optimization of the Thermodynamic Efficiency of a Recuperative Heat Exchanger
Authors: Adebiyi George A.
Published: November 2021

A heat exchanger is strictly speaking a thermal exergy transfer device, and the proper measure of its efficiency is the second law efficiency. This article considers the efficiency of a single-pass, recuperative heat exchanger in which a given stream of hot fluid is available for heating a cold stream of fluid in a specified manner. The analysis takes cognizance of the required exergy input to overcome fluid friction in the flow passages, as well as the thermal exergy flow rates for the fluid streams, in the determination of the second-law efficiency. Maximization of the second-law efficiency is found to provide a basis for sizing the heat exchanger for optimum thermodynamic efficiency of operation.

The key parameters that determine this optimum include the number of transfer units (NTU), the ratio of thermal capacity rates (Cr), a dissipation parameter which involves the Eckert and Prandtl numbers, and the flow configuration (whether parallel-flow, or counter-flow). Other parameters relevant to the performance of the heat exchanger are the tare capacity (εtare), and the ratio of the inlet temperature of the hot fluid to the ambient temperature.
Evaluation and Optimization of Automated Operation in Small CHP Plants
Authors: Grue Jeppe , Andersen Jens , From Niels , Bach Inger
Published: November 2021

In Denmark power generation is extensively based on small combined heat and power plants, which produce electric power and district heating. This work will focus on the small plants around 1 MW in size, which are often unmanned and operating completely automatically. The objective of this work is to formulate a method which can be used to determine the optimal operating strategy for a CHP plant, and that this strategy must be fully automated. The contribution margin of the plant is used as the objective function for the optimization. Finally the method is tested on a small CHP plant, which is a gas engine producing 1.34 MW electrical power and 1.6 MJ/s district heating. The methods, which are developed, can be used in general for the evaluation and optimization of automated strategies for the operation of small-unmanned CHP plants. The strong feature of the method is that it sets an ultimate target that is the best possible one to obtain with a view to any strategy. This provides a basis for the evaluation and optimization of the actual strategy.
Determining Optimal Operating Conditions for Cogeneration Systems Using Minimum Entropy Generation Rate and Maximum Performance Criterion
Authors: Kowalski Gregory J. , Zenouzi Mansour
Published: November 2021

Many systems, such as domestic residences and business, institutional or shopping building complexes, require both a power input and a heat input to properly operate. Usually, the power input is in the form of electricity. An analysis for determining the most advantageous method of satisfying the energy requirements for these types of systems and of estimating the maximum possible value of the energy utilization factor is developed using an idealized regeneration cycle with heat exchangers that operate between different temperature reservoirs. The results are summarized in terms of the ratio of the heat load to the required power, (HLRP). The HLRP ratio is the significant design factor for these system and all results are scalable with it. The first law thermal efficiency or energy utilization factor and the entropy generation rate, (EGR), are determined at different practical operating conditions. The EGR is directly proportional to the rate of exergy destruction because of the system definition used in the analysis. The usefulness of the thermal efficiency and the EGR as design tools is investigated. The first law thermal efficiency reaches a maximum possible value of 76% at a HLRP ratio value of 0.67 for practical values of the operating conditions. At this HLRP ratio value the heat rejected from the heat engine equals the required heat load, the critical HLRP value. No minimum behavior was observed for the EGR as a function of the HLRP ratio for the cogeneration system. The EGR results are not a useful design tool during the initial design phase for cogeneration systems because of this trend. The results suggest that cogeneration systems should be selected for HLRP ratio values that are greater than the critical value. As the HLRP ratio increases the performance of the cogeneration system approaches that of the traditional system and are in an operating range that is governed by cost factors rather than energy usage factors. The results are compared to irreversible heat engine system and to a system without cogeneration. This research is the only first step of an investigation that will include the cost analysis and comparison to operating cogeneration installations in the next phase.
A New Type of Gas Turbine Based-Hybrid Propulsion System: Part 1—Concept Development, Definition of Mission Parameters and Preliminary Sizing
Authors: Cioffarelli Emiliano , Sciubba Enrico
Published: November 2021

A hybrid propulsion system of new conception for medium-size passenger cars is described and its preliminary design developed. The system consists of a turbogas set operating at fixed rpm, and a battery-operated electric motor that constitutes the actual “propulsor”. The battery pack is charged by the thermal engine which works in an electronically controlled on/off mode. Though the idea is not entirely new (there are some concept cars with similar characteristics), the present study has important new aspects, in that it bases the sizing of the thermal engine on the foreseen “worst case” vehicle mission (derived from available data on mileage and consumption derived from road tests and standard EEC driving mission cycles) that they can in fact be accomplished, and then proceeds to develop a control strategy that enables the vehicle to perform at its near–peak efficiency over a wide range of possible missions. To increase the driveability of the car, a variable-inlet vane system is provided for the gas turbine.

After developing the mission concept, and showing via a thorough set of energy balances (integrated over various mission profiles), a preliminary sizing of the turbogas set is performed. The results of this first part of the development program show that the concept is indeed feasible, and that it has important advantages over both more traditional (Hybrid Vehicles powered by an Internal Combustion Engine) and novel (All-Electric Vehicle) propulsion systems.