bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural Modeling Considerations for Dynamic Optical Space Structure Simulations
Authors: Griffin Steven , Schrader Karl 
Published: November 2021

Abstract
Boeing-SVS has developed an integrated modeling tool, Zelink, which effectively combines three commercial standard codes, Zemax, Simulink and Nastran, to predict the effect of quasistatic and dynamic disturbances on optical metrics of interest in optical space structures. Examples of optical metrics are time-varying wavefront error, point spread functions and predictions of image degradation. A simulation might involve specification of a slew angle and prediction of time-varying wavefront error. Different command shaping and attitude control techniques might be evaluated with respect to their ability to minimize wavefront error. Implementation of such simulations has shown significant dependence of simulation results on the structural modeling approach. In particular, one approach may introduce errors in the optical metric of interest, where another approach may avoid errors. The sensitivity of the optical metric is related to the necessity of maintaining the optical prescription when there is no structural deformation. A quasistatic rotation of the space structure should not significantly distort the optical prescription, since there is almost no structural deformation associated with this maneuver. This paper discusses structural modeling approaches and makes recommendations specific to optical space structure simulations.
Development and Integration of a Semi-Analytical PCB Thermal Design Technique With an Infrared Thermal Imaging System
Authors: Park Hyunjae , Nigro Nicholas , Gollhardt Neil , Lee Ping 
Published: November 2021

Abstract
Traditionally, analytical models are developed to predict the thermal behavior of Printed Circuit Boards (PCBs). The predicted results are then verified with other analytical or experimental results prior to using the models in design. This is a time intensive process and the results predicted using these models may include limitation due to idealization. In order to overcome this disadvantage, a semi-analytical model is proposed in this study. The semi-analytical model uses analytic theory in conjunction with results obtained from an Infrared-Radiation Thermal Imaging System (IRTIS). The model is verified and updated, allowing the results to be immediately incorporated into PCB thermal design. The parameters in the semi-analytical model are determined by employing a least squares temperature curve fit for the first upstream heating component in conjunction with a simple conduction model for the PCB wall. The model was tested with a natural convection cooled PCB with three inline heating components. Temperature data for the first upstream component was measured with an IRTIS and fit to the semi-analytical model. The model predicted temperature results for all three heating components with good agreement. The PCB thermal design technique enables the IRTIS to be employed as a preliminary design tool that significantly reduces design iterations through the use of the semi-analytical model.
Compact Air-Coupled and Hydronically Coupled Microchannel Heat Pumps
Authors: Jiang Yirong , Garimella Srinivas 
Published: November 2021

Abstract
Novel air-coupled and hydronically coupled heat pumps using microchannel components were investigated in this study. The air-coupled system uses microchannel tube, multilouver fin heat exchangers as the evaporator and condenser. In the hydronically coupled heat pump, refrigerant in the evaporator as well as the condenser transfers heat to an intermediate fluid such as an ethyleneglycol solution. The glycol loops are connected to the indoor/outdoor air through liquid-air heat exchangers. Models to simulate cycle thermodynamics, and single- and two-phase heat transfer in the components were developed to design these systems for cooling and heating mode operation. The components were optimized to develop the most compact systems that would satisfy system performance requirements. These systems were also compared with a conventional round-tube, plate-fin heat pump, which was designed using a commercially available simulation tool.
Results from this study show that indoor and outdoor units of air-coupled microchannel systems can be packaged in only one-half and one-third the space required for a conventional system. Even more compact refrigerant heat exchangers are required in the hydronically coupled system, because of the high heat transfer coefficients for these liquid-coupled heat exchangers, and the counterflow orientation. The hydronic coupling offers flexibility in system location, and is well suited for integrated space-conditioning and water heating systems. Both air-coupled and hydronically coupled systems result in significant reductions in refrigerant inventories compared to round-tube systems. The refrigerant charge of the microchannel air-coupled system is 20% less than that of the round-tube heat pump. For the hydronically coupled system, the refrigerant charge is only 10% of the charge in the round-tube heat pump.
Modeling of a Transcritical Carbon Dioxide Vapor Compression Cycle: Validation and the Effect of Refrigerant Pressure Drop on Cycle Performance
Authors: Robinson Douglas M. , Groll Eckhard A. 
Published: November 2021

Abstract
Due to world wide restrictions on the use of fluorocarbon based refrigerants, carbon dioxide has recently received attention as a possible replacement for those refrigerants in certain applications. In order to evaluate the potential performance of a transcritical vapor compression refrigeration cycle using carbon dioxide as the refrigerant, a cycle model has been developed which can simulate the operation of a carbon dioxide based air conditioner. This model is called ACCO2 and includes a detailed heat transfer analysis of the heat exchangers, accounting for the effect of both thermodynamic and thermophysical properties of carbon dioxide, as well as other component models.
ACCO2 simulates the operation of a carbon dioxide based air conditioner that uses air as the heat source and heat sink. An overview of component models and the methodology to combine them into an overall cycle model (ACCO2) is presented. ACCO2 was validated using experimental data and data from another validated air conditioner model. During validation, it was noted that the accuracy of refrigerant pressure drop prediction had a strong influence on the accuracy of the prediction of overall cycle performance. In addition, conclusions were drawn concerning the impact of refrigerant pressure drop in an actual carbon dioxide based air conditioner. Conclusions are also drawn concerning the validation and future uses for ACCO2.
Effect of Comfort Constraints on Cycle Efficiencies
Authors: Richter Matthew , Bullard Clark , Hrnjak Pega 
Published: November 2021

Abstract
The traditional ideal Evans-Perkins cycle analysis is extended to include the effects of the comfort of the conditioned space and finite airflow rates on cycle efficiency. Based on this, the performance of R410A and R744 for residential heating and cooling applications is compared. The effect on annual efficiency of the two refrigerants based on load requirements for three diverse climates is also discussed.
A Catalytically Sustained Microcombustor Burning Propane
Authors: Hatfield Jonathan M. , Peterson Richard B. 
Published: November 2021

Abstract
The performance of a catalytically sustained microcombustor was investigated. The reactants for combustion were air and propane, which were mixed together and delivered to the end of a bayonet-style, heat recirculating combustor having a reaction volume measuring approximately 0.25 mm3. Platinum wire in the shape of a coil was used as an active surface to catalyze the exothermic reactions. Measurements of temperature and reactant flow rate were made during the study. Results show that propane can be burned in a self-sustaining fashion in the microcombustor with heat release rates as low as 1.0 Watt.
The Characteristic Physical Parameter Approach to Modeling Chillers Suitable for Fault Detection, Diagnosis and Evaluation
Authors: Jia Yongzhong , Reddy T. Agami 
Published: November 2021

Abstract
Model-based fault detection and diagnosis approaches based on statistical models for fault-free performance concurrently require a fault classifier database for diagnosis. On the other hand, a model with physical parameters would directly provide such diagnostic ability. In this paper, we propose a generic model development approach suitable for large engineering systems that usually come equipped with a large number of sensors. Such a methodology, called the characteristic parameter approach, is proposed for large centrifugal chillers which are generally the single most expensive piece of equipment in HVAC&R systems.
The basis of the characteristic parameter approach is to quantify the performance of each and every primary component of the chiller (the electrical motor, the compressor, the condenser heat exchanger, the evaporator heat exchanger and the expansion device) by one or two performance parameters, the magnitude of which is indicative of the health of that component. A hybrid inverse model is set up based on the theoretical standard refrigeration cycle in conjunction with statistically identified component models that correct for non-standard behavior of the characteristic parameters of the particular chiller. Such an approach has the advantage of using few physically meaningful parameters (as against using the numerous sensor data directly) which simplifies the detection phase while directly providing the needed diagnostic ability. Another advantage to this generic approach is that the identification of the correction models is simple and robust since it requires regression rather than calibration. The entire methodology has been illustrated with actual monitored data from a centrifugal chiller. The sensitivity of this approach to sensor noise has also been investigated.
Rational Design of Vehicles: I — Multi-Objective Optimization
Authors: Paulus David M. , Gaggioli Richard A. 
Published: November 2021

Abstract
The customer for a vehicle typically has several desiderata, such as top speed, fuel economy, range, acceleration, .... Generally, these desiderata are conflicting. So, in order to deduce a single objective function, a means is needed for weighting (implicitly if not explicitly) the relative importance of these desiderata. That is, for weighting these “multiple objectives.” This paper presents a rational methodology for developing a single-objective function to be optimized during the design of a vehicle. The methodology does require answers from the customer(s) to a straightforward set of questions, referring to the desiderata. Based on the answers, the objective function follows, mathematically, in a straightforward manner. An application to a light, personal aircraft serves as a case study.
Energy Storage With Solid/Liquid Phase Change in Presence of Natural Convection
Authors: Pinelli M. , Piva S. 
Published: November 2021

Abstract
Solid/liquid phase change process has received great attention for its capability to obtain high energy storage efficiency. In order to analyse these systems, undergoing a solid/liquid phase change, in many situations the heat transfer process can be considered conduction-dominated. However, in the past years, it has been shown that natural convection in the liquid phase can significantly influence the phase change process in terms of temperature distributions, interface displacement and energy storage.
In this paper, a procedure to analyse systems undergoing liquid/solid phase change in presence of natural convection in the liquid phase based on the utilisation of a commercial computer code (FLUENT), has been developed. This procedure is applied to a cylinder cavity heated from above and filled with a Phase Change Material. It was found that when the coupling with the environment, even if small, is considered, natural convection in the liquid phase occurs. The numerical results are then compared with available experimental data. The analysis shows that the agreement between numerical and experimental results is significantly improved when the results are obtained considering the presence of circulation in the liquid phase instead of considering the process only conduction-dominated. Furthermore, some interesting features of the flow field are presented and discussed.
Exergy Analysis of a Turbojet Engine Over a Complete Flight Cycle
Authors: Rosen Marc A. 
Published: November 2021

Abstract
Exergy analysis is used to evaluate the efficiency of a turbojet engine over an entire flight (including climb, cruise and descent), and to assess the sensitivity of these results to the selection of the reference environment. This study is an extension of previous work where the accuracy of an exergy analysis of a turbojet engine is evaluated for different reference environments on an instantaneous basis. The present work evaluates cumulative engine efficiencies. The results show that the use of a constant reference environment set at cruise altitude conditions yields cumulative exergy efficiencies that are within 0.01% of those found using a variable reference environment (equal to the operating environment conditions at all times) over a 3,500 km flight. This result is in contrast to the use of a constant sea-level reference environment where such are 3.7%. This significant cumulative efficiency difference with the choice of reference environment is not observed when using an instantaneous exergy analysis. Care must be exercised when using a constant reference environment, as for both constant sea-level and cruise-altitude reference environments cumulative rational efficiencies increase over the majority of the flight, whereas for a continuously varying reference environment these efficiencies decrease.
Introducing Thermal System Optimization in an Introductory Engineering Thermodynamics Course
Authors: Byerley Aaron R. , Newton Harry N. , Tuite John R. 
Published: November 2021

Abstract
This paper describes a thermal system analysis, design, and optimization project that has been successfully used for two years in an introductory engineering thermodynamics course. The project has provided the students with an opportunity to gain a first-order understanding of the optimization process through the use of spreadsheets and math applications packages. The assignment has been based on the modeling and optimization of a non-ideal gas turbine cycle for use in an Unlimited Class Hydroplane. Student teams are guided through the five steps of the engineering design process including 1.) “information gathering” using mostly web-based material; 2.) “problem definition and alternative generation” using the rules published by the Unlimited Class Hydroplane Racing Association; 3.) “evaluation” of the alternatives using a predictive model based upon thermodynamic principles; 4.) “decision making” using graphical and numerical results generated by spreadsheets and math applications packages; and 5.) “presentation” of the design recommendations in both oral and written reports. Compressor pressure ratio and isentropic efficiencies for the compressor and turbine were the three design variables. Penalty functions were assigned to each to account for component cost, weight, volume, and complexity. The objective function was defined as the ratio of “shaft power to total penalty units” and was maximized using surface plots generated in Excel 97. The optimal solution was also obtained using Mathcad 8.0, Mathematica 3.0, Solver (an add-in tool for Excel 97), and Ada 95, a general programming language. Animated surface plots clearly illustrated the underlying mathematical operations of optimizing a system of non-linear equations.
An Application of the Dynamic Balance Equation
Authors: Geskin Ernest S. 
Published: November 2021

Abstract
The Onsager formalism (generalized fluxes, sources and variables) is used to construct the dynamic balance equation. Previously this equation has been applied to the investigation of energy balance, which includes all interactions between a system and the environment. In this paper the work and non-work interactions are discussed separately. The corresponding forms of the generic balance equation are considered and the dynamic balances of the representative variables ( P V ¯ and enthalpy) are examined. It is shown that the equilibrium relations constitute particular cases of the constructed equations. At the same time the dynamic equations also reveal additional information about a system in question, for example, the developed equations determine the available work of a non-steady process. The paper demonstrates that the dynamic thermodynamic functions constitute an effective tool for systems description.
Design, Construction, Start-Up and First Experimental Trials of a Test Rig for Single Fuel Cells
Authors: Desideri Umberto , Lunghi Piero , Ubertini Stefano 
Published: November 2021

Abstract
The recent spreading of the interest for fuel cells brings, as a consequence, the need of intense effort for components and system development and testing. While the most resourceful cell developers have realized experimental set-ups for cell duration estimation, it is very rare to find test rigs for complete characterization of cell performance as a function of the numerous input parameters i.e. streams mass flow, composition, temperature and purity, fuel utilization factor, current density. In the present state of the art some modelling of the influence of these factors exists as well as some experimental results for cell potential evaluation at different current densities. What is not found in literature and is difficult to obtain is a complete experimental characterization of fuel cells in which the dependence of performances on a single factor is disaggregated from the others and clearly evaluated. This paper present a test rig for single cell designed to reach these targets and its first tests on a Molten Carbonate Fuel Cell. The experimental setup has revealed to be very flexible allowing the characterization of the system at different operating conditions.
Effects of Heat Accumulation on the Thermodynamic and Economic Performance of CHP
Authors: Portacha Jozef , Smyk Adam , Zielinska Alicja , Fiszdon Jerzy K. 
Published: November 2021

Abstract
Heat accumulation in cogenerating plants allows increased electricity production during highest demand period. It also causes change of the overall electricity production. Changes in cogeneration coefficient follow the same trend. This paper examines the effect on the average cogeneration factor caused by adding the heat accumulator to the existing CHP. Variation of this coefficient influences the plant economics, since electrical energy is most expensive during the peak hours. In the model presented the operating conditions vary due to variations in the surroundings temperature and due to cyclical operation of the heat accumulator. Assumptions made, the mathematical model, and numerical method used are also presented.
District Heating in the City of Tokyo: A Case Study Using a New Integrated Simulation Environment
Authors: Burer M. , Li H. , Favrat D. , Kraines S. , Wallace D. 
Published: November 2021

Abstract
This paper aims to illustrate a new holistic modeling environment through a case study implementing a district heating system to supply four groups of users identified in the city of Tokyo. The holistic modeling environment, called DOME (Distributed Object-based Modeling Environment) is being used by researchers in the Alliance for Global Sustainability (AGS) to develop a platform for assessing technologies and policies in order to significantly reduce CO2 emissions in large cities. DOME is used as an information based collaboration platform for supporting the decentralized integration of models built independently under various application tools and operating systems. It provides system engineers with the ability to access experts’ models over the Internet through user-friendly interfaces. The interfaces provide clearly identified input and output variables to support a facilitated integration. The DOME environment also provides tools for analyzing the resultant integrated system.
In this district heating simulation, a GIS (geographic information system) based land-use database manager, implemented as an object in DOME, is used to obtain the total ground area, the total building floor area, and the number and type of buildings in a specified region of Tokyo. Using the land use database manager, four groups of users are established. The heat demands of the users are derived using specific heat consumption data for the types of buildings considered. Users are either connected to the district heating system through direct heat exchangers on the supply or return line, or through local heat pumps which adapt the temperature to the needs locally, allowing a lower network temperature. Two different options are considered for the district heat supply: 1) a heat pump based superstructure comprising a gas turbine and a gas engine as cogeneration units, as well as an auxiliary boiler for peak load, and 2) a gas turbine / steam turbine combined cycle based superstructure with various options like steam injection and/or CO2 separation unit.
Physical and costing models for the two alternative production unit superstructures and for the district heating system are connected with the GIS database manager using DOME.
The environomic methodology, a simultaneous consideration of thermodynamic, economic and environmental criteria expressed as an aggregated cost, is used to assess the alternatives under different scenarios characterized by the cost of natural gas and the degree of pollution cost internalization.
The Use of Collaborative Learning in Biomedical Engineering Education
Authors: Gaver Donald P. 
Published: November 2021

Abstract
At Tulane University, we have developed a course that is intended to bridge the gap between traditional mathematics ‘tools-based’ courses taken by undergraduates and the application of these tools to model biological systems. This course, ‘Mathematical Modeling and Analysis of Biological Systems,’ was developed initially as a graduate-level course, and has migrated to become required of all Biomedical Engineering undergraduates.
A Matlab-Based Cardiac Mechanics Course: Exportable Tools for Graduate-Level Soft Tissue Biomechanics
Authors: Holmes Jeffrey W. 
Published: November 2021

Abstract
Graduate courses in finite elasticity and soft tissue biomechanics must deliver substantial theoretical content to prepare students for the complexities of soft tissue mechanics. In the laboratory students often discover that practical tasks such as calculating three-dimensional finite strain from marker data or reconstructing three-dimensional marker positions from two-dimensional views are not obvious despite mastery of the underlying theory. This course sought to replace as much didactic time as possible with hands-on MATLAB programming and simulations to illustrate basic theory and help students make the bridge to practical applications.