bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modeling and Testing of an Autonomous Swimming Vehicle Powered via Smart Materials
Authors: Borgen Michael G. , Washington Gregory N. , Kinzel Gary 
Published: November 2021

Abstract
This work details the design of a miniature swimming vehicle that propels itself through oscillations of a flexible fin mounted in the stern. The fin is driven through a mechanism that is actuated by two curved-beam bending piezoelectric actuators. An optimization routine is used to design the mechanism for rigid body guidance. The actuators are modeled statically using the Bernoulli-Euler method. Hamilton’s principle is applied to the actuators and, by employing modal analysis, a dynamic actuator model is developed and compared to experimental data. The physical evolution of the swimming vehicle is discussed, and a prototype for an onboard digital control circuit is evaluated. The latest vehicle design, which incorporates onboard digital control, is presented in terms of its design and experimental performance characteristics. The current swimming vehicle prototype achieves fish-like maneuvering and an approximate velocity of 0.25 m/s.
Thermal Characteristics of a Free Radial Liquid Jet Impinging on a Hot Surface
Authors: Hassaneen Ahmed , Rahman Muhammad M. 
Published: November 2021

Abstract
This paper presents results of CFD computation of the heat transfer process in a radial impinging free liquid jet. The jet is impinging on a flat circular disk and the flow downstream of the impinging area spreads outward and inward on the disk. The solution is made under steady state and laminar flow conditions. The solution is obtained for the axisymmetric radial jet with two free surfaces. Different incidence angle of the jet and different flow Reynolds number (Re) were considered in the analysis. The effect of jet elevation from the disk is discussed in addition to different thickness of the hot plate. Due to lack of experimental data on this typical flow problem, the results were qualitatively compared with the available experimental data of the closest flow condition in the literature. The jet incidence angle and jet elevation were found to have strong effects on the velocity field and the free surface position of the spreading flow on the disk and consequently affected the heat transfer process. The disc thickness is also found to have a strong effect on the local and average Nusselt number. Results are documented by plotting the distribution of local and average Nusselt number versus the geometrical parameters.
Wettability Measurement and Criterion for a Falling Film Absorber
Authors: Kim Jin-Kyeong , Park Chan Woo , Kim Ig Saeng , Jurng Jong Soo , Kang Yong Tae 
Published: November 2021

Abstract
The objectives of this paper are to develop a new method of wettability measurement and to study the effect of surface roughness on the wettability in a LiBr/H2O falling film absorber. Three absorber tubes with micro-scale roughness are tested in a falling film absorber installed in a test rig. Inlet solution temperature (30–50°C), concentration (55–62 weight % of LiBr) and mass flow rate (0.74–2.71 kg/min) are considered as key parameters. A new method is proposed to estimate the wettability of a tube by measuring a minimum mass flow rate to wet the tube completely. Reynolds number is ranged from 30 to 120 by controlling the inlet mass flow rate. The wettability for the structured surfaces was higher than that for the bare tube. The wettability decreased linearly along the vertical location as low as 65% for the bare tube and 75% for the micro-scale scratched tubes. The wettability increased with increasing the solution temperature and the solution mass flow rate. The effect of film Reynolds number on the wettability in the bare tubes was more significant man that in the micro-scale scratched tubes. The experimental results of wettability can be used in the design of absorbers with micro-scale roughness.
Analysis of Inner-Cylinder Rolling Piston Compressors
Authors: Wang Guoliang , Guo Bei , Zhang Wei , Li Liansheng , Shu Pengcheng 
Published: November 2021

Abstract
A new inner cylinder installed in a rolling piston compressor is proposed here. The rotor is hollowed out in to a new cavity. Thus a new working cavity is formed and the utilization rate of the cylinder increases. Compared with the traditional rolling piston compressor, the proposed one has higher effective volume and will be widely applied.
Study of the Discharge Pressure Pulsation Within Twin Screw Compressors
Authors: Xing Ziwen , Peng Xueyuan , Zhang Xiaojun , Cui Tiansheng 
Published: November 2021

Abstract
Even in the absence of valves, flow through the discharge port of a screw compressor is oscillatory in nature. This unsteady but periodic flow variation at the discharge port excites the pressure pulsation. In this paper, the one-dimensional unsteady gas flow equations describing the discharge pressure pulsation are established, which allow for the effects of the viscosity friction and heat transfer between the gas and the pipe, and the boundary conditions of discharge pressure pulsation are considered. With Two-Step Lax-Wendroff scheme used, the one-dimensional unsteady gas flow equations are solved. In order to verify the theoretic analysis, the discharge pressure pulsation at variable working conditions is measured. It is shown that the model established in this paper is valid for getting a better understanding of the mechanism governing the behavior of the pressure pulsation in discharge pipe. It is found that the most important factor that affects the discharge pressure pulsation is the pressure difference between the actual discharge pressure and the design discharge pressure.
Development of Solar/Waste Heat Driven Dual-Mode, Multi-Stage, Multi-Bed Regenerative Adsorption System
Authors: Saha B. B. , Koyama S. , Akisawa A. , Kashiwagi T. , Ng K. C. , Chua H. T. , Yoon J. L. 
Published: November 2021

Abstract
Over the past three decades there have been considerable efforts to use adsorption (solid/vapor) for cooling and heat pump applications, but intensified efforts were initiated only since the imposition of international restrictions on the production and use of CFCs (chloroflurocarbons) and HCFCs (hydrochloroflurocarbons). Closed-type, conventional adsorption refrigeration and heat pump systems have an increasing market share in Japan. In this paper, a dual-mode, three-stage non-regenerative, 6-bed regenerative silica gel-water adsorption chiller design is outlined along with the performance evaluation of the innovative chiller. This adsorption chiller utilizes effectively solar or waste heat sources. Two operation modes are possible for the advanced chiller. The first operation mode will be to work as a highly efficient conventional chiller where the driving source temperature is between 60 and 95°C. The second operation mode will be to work as an advanced three-stage adsorption chiller where the available driving source temperature is very low (between 40 and 60°C). With this very low driving source temperature, no other cycle except an advanced adsorption cycle with staged regeneration will be operational. The drawbacks of this operational mode are its poor efficiency in terms of cooling capacity and COP.
Two-Layer Model to Simulate the Effect of Marangoni Enhancement of Absorption
Authors: Arora Ravi , Herold Keith E. 
Published: November 2021

Abstract
Absorption of vapor into a laminar film of liquid is a well-known problem that has received considerable interest in the literature. In many practical systems, the mass transfer process in the liquid phase is a limiting factor because the diffusion of mass is much slower than the diffusion of energy. Enhancement of absorption usually involves some scheme to mix the liquid, causing the effective diffusivities to increase. One such enhancement method is the use of surfactants that drive Marangoni flow in the liquid. This method is used very effectively in absorption chillers based on aqueous lithium bromide. The complexity of the resulting liquid flow is significant and this may explain why there are few studies of this effect found in the literature.
In the present paper, a model is described which treats the liquid film as composed of two-layers: the inner layer is laminar and the outer layer is fully mixed. The relative thickness of the two layers is a parameter that must be known to enable use of the model. The layer thickness was determined from comparisons between the model results and absorption data from a vertical tube absorber. The layer thickness is found to be a function of liquid flow rate and surfactant concentration.
A Distributed Model for the Transient Performance of a Space Heat Pump
Authors: Jiang Haobo , Radermacher Reinhard 
Published: November 2021

Abstract
A prototype heat pump was designed and tested as a means of active thermal management for electronics packages to be used on stratospheric balloon missions. The evaporator worked as a cold plate to absorb heat dissipated by the electronics, while the condenser rejected heat primarily by radiation to the rarified environment.
To predict the transient performance of the heat pump under varying environmental temperature and cooling load conditions, a dynamic model of the heat pump was created with a graphical user interface (GUI). The simulation of the evaporator and condenser are fully transient and the components are segmented, whereas the compressor and expansion device are lumped models and assumed to be at quasi-steady state. A detailed model for the mass and energy conservation in the two heat exchangers is presented. The spatial and temporal variation of temperature and mass flow rate in the heat exchangers are predicted. Several types of transient conditions such as step changes of the space temperature and cooling load, system start-up, shutdown, and cycling, are studied. The space temperature, cooling load, compressor power, mass flow rates of the compressor and expansion device, pressures and refrigerant charges of the condenser and evaporator, and temperature distribution in the heat exchangers are dynamically displayed on the GUI. The simulation results are compared with experimental data for step changes in the cooling load and show good agreement in terms of trends.
Thermodynamic Analysis of Expander Applications in Refrigeration Cycles
Authors: Vaisman Igor B. 
Published: November 2021

Abstract
Modern expander applications in refrigeration are associated with two-phase expanders to replace the irreversible throttling process of liquid refrigerants. This paper relates to vapor expander applications utilizing available waste heat for complete power recovery to drive power-consuming equipment of R134a air conditioning systems and reducing the global warming effect. The vapor compression and expansion refrigeration cycle is introduced and its thermodynamic analysis is provided. The calculated performance characteristics on boiling temperature in the boiler, condensing temperature in the condenser, evaporating temperature in the evaporator, and compressor and expander isentropic efficiencies are presented and compared with the regular refrigeration cycle and the two-phase expander refrigeration cycle.
CO2 Transcritical Cycles for High Temperature Applications
Authors: Hwang Yunho , Huff Hans-Joachim , Preissner Marcus , Radermacher Reinhard 
Published: November 2021

Abstract
A breadboard CO2 prototype heat pump for stationary applications was designed, constructed, and tested. Test results of the CO2 prototype showed about 12% lower cooling capacity but a similar cooling Coefficient of Performance (COP) at 40°C (104°F) ambient temperature as compared to R-22 environmental control units (ECU). However the projected COP of the CO2 prototype at 52°C (125°F) is lower than that of the original R-22 ECU. Therefore it is necessary to investigate methods to improve the efficiency while considering the design issues especially for high temperature operation. As means to improve the performance of the CO2 cycle at higher ambient conditions, four methods were investigated: a suction-line heat exchanger, an expander, an evaporatively cooled gas cooler, and a two-stage split cycle. It is expected that a suction-line heat exchanger can increase the high temperature capacity and COP of a CO2 system by approximately 10% and 20%, respectively. For an expander inlet temperature of 52 °C (125°F), the COP improvement is about 27% with an expander efficiency of 50%. An improvement in COP of 17% to 24% is achieved by using an evaporatively cooled gas cooler while the system cooling capacity improved by 6% to 8% at ambient temperatures of 35°C (95°F) and 45°C (113°F), respectively. The two-stage split cycle with intercooling offers 38% to 63% COP improvement at 30 to 50°C (86 to 122°F) ambient conditions.
If one of these methods are implemented, the performance of the CO2 system can compete with R-22 ECUs. If two or more of above methods are implemented, the benefits may be higher than each one of them. However the benefit cannot be simply superpositioned due to the counteract effects. Therefore, the benefits of the implementation of two or more of above methods remain as a further study.
A Procedure for Filtering the Induced Effects in the Thermoeconomic Diagnosis of an Energy System
Authors: Verda Vittorio , Serra Luis , Valero Antonio 
Published: November 2021

Abstract
The aim of the diagnosis techniques usually applied in energy systems is the detection of signs of possible malfunctions, in particular those malfunctions that can cause failures, if not removed. The thermoeconomic diagnosis is applied to detect and locate possible inefficiencies of the plant components that provoke variations of the plant efficiency.
Thermoeconomic diagnosis procedures are based on the comparison between the real operation conditions and carefully selected reference conditions, usually characterized by the same qualitative and quantitative plant productions. In this way a difference in the overall fuel consumption (fuel impact) is an index of the presence of malfunctions due to the component inefficiencies. The use of the thermoeconomic theories for the location of anomalies presents the problem of the induced malfunctions [1], In fact, when an anomaly takes place in a component, not only its efficiency decreases, but also other components change their behaviour, due to the modified working conditions provoked by the anomaly. The induced malfunctions have two different causes: 1) the malfunctioning component requires a larger amount of fuel to maintain constant its production, so the other components must increase their production too, thus varying their efficiency; 2) as the values of some set-point variables can have been modified, the regulation system must operate to restore its set-point value. Its action modifies the plant working conditions, inducing new malfunctions.
In this paper a procedure for filtering and canceling the induced malfunctions is proposed. Hence, the devices suffering the real inefficiencies can be identified and located. The proposed procedure is based on the knowledge of the system behaviour when the regulation parameters vary. A first fictitious working condition, called free condition [2], is mathematically built, starting from the operation conditions and restoring the regulation parameters corresponding to the reference operating conditions. In this way the free condition does not include the regulation system contribution. A second state is then built for every single component in order to take into account the malfunctions induced by the degradation of the components behavior. The procedure is particularly useful when the number of malfunctions is unknown, as it happens in the usual operation of an actual plant. If the induced malfunctions are filtered, all the component inefficiencies can be identified at the same time.
The proposed procedure is applied to a 33 MW gas turbine plant, also providing 63 MW of thermal power to a district-heating network. A mathematical model of the plant has been used to simulate the behavior degradation of the gas turbine devices, when several components inefficiencies occur.
A Diagnosis Procedure for Energy Conversion Plants: Part II — Application and Results
Authors: Stoppato Anna , Carraretto Cristian , Mirandola Alberto 
Published: November 2021

Abstract
By applying the diagnostic procedures discussed in Part I to some actual plants (a coal fuelled steam power plant, a combined plant running on natural gas and a steam cogenerative plant fed by solid wastes) significant results have been obtained. A software system has expressly been implemented and connected with plant acquisition and control devices.
Operation data have been collected and processed, focusing on the main components failures (i.e. boiler, condenser and steam turbine stages) and on plant conditions after long periods without maintenance (hence highlighting wear and fouling effects on the overall performances). These tests allowed to validate the system modules and obtain useful information about sensitivity and applicability of the methods. The structure of the software and its available strategies to detect and weigh malfunctions are deepened in the paper.
Optimization of Sulfur Sublimators Used in the Colombian Flower Industry
Authors: Huertas José Ignacio , Rodríguez Julián D. 
Published: November 2021

Abstract
The Oidio is considered one of the strongest diseases that attack the rose plantations. To control it, different alternatives are used, being the most common the application of fine sulfur powder over the leaves of the plant. To spray these powder, it is used a sulfur sublimator which warms the sulfur by electrical resistors up to the working temperature, where the sulfur is melted and evaporation takes place. The evaporated sulfur condenses forming very fine particles, which are transported by the natural convective airflow inside the greenhouse. Finally the fine powder is uniformly distributed over the leaves of the rose plants.
Previous studies have found that the thermal efficiency of the commercial sulfur sublimators is less than 0.1% and that the use of these sublimators represent more than 60% of the total electrical consumption of the farm.
Analytical and experimental work was conducted in order to find the optimum working temperature and the appropriate geometry of high efficiency sublimators. The work involved the characterization of commercial sublimators and the development of a mathematical model to describe the evaporation phenomena in the sublimator. Results showed that the working temperature should be 220°C, the appropriate geometry should be similar to a jar, and that the maximum attainable thermal efficiency working at 220°C is ∼2%. Based on these results, 2 prototypes of sublimators were manufactured. The new sublimators showed efficiencies close to 1%.
The Bio-Fuel Boiler House Concept in the District Heating Applications
Authors: Dzierzgowski Mieczysław , Zwierzchowski Ryszard 
Published: November 2021

Abstract
The biomass boiler house concept in the district heating applications, both from technical and economical point of view is detailed analyzed to assure the most effective investment and future operation.
This paper is concerned with the application of the Bio-fuel Boilers (BfB) as a one of perspective way of the District Heating System (DHS) modernization programs in Poland. Considering use of bio-fuels, Poland has relatively big potential particularly in bio-mass. Appropriate bio-mass technology is mainly related to the potential and supply of the bio-mass in cosidered region of the country. Usually, due to supply of bio-fuel, bio-mass fired boiler house not exceeds 30–40 MW.
For the purpose of selection of appropriate type and capacity of the BfB for installation in the District Heating Plant (DHP), operational analysis of the DHS and investigation of possible implementation of the Thermal Energy Storage (TES) systems were performed. Also, investment costs for the BfB and the TES system application in the DHS were assessed.
Operational analysis of the DHS covered supply and demand side i.e., heat generation by the DHP and heat consumption by the consumers. Heat consumption analysis during summer season was carried out in order to increase operational efficiency of the BfB installations and for investigation of the TES systems application in the DHS.
Heat storage in the DHS and its influence on capacity and operation of the BfB was also investigated. Both, heat accumulation by the District Heating Network (DHN) and by the non-pressure TES system were analyzed.
Finally, results of calculation of the required capacity of the TES systems assuring continuous and efficient operation of the BfB installation in the DHS, especially during summer season were shown. Some advantages of the TES system implementation in the DHS in case where the BfB are applied in the DHP were presented as well.
Analysis of a High-Efficiency Natural Gas-Assisted Steam Electrolyzer for Hydrogen Production
Authors: Martinez-Frias Joel , Pham Ai-Quoc , Aceves Salvador M. 
Published: November 2021

Abstract
This paper presents a description and analysis of a high-efficiency hydrogen production system. The main component of the system is a novel steam electrolyzer. In conventional electrolyzers, oxygen produced from electrolysis is usually released into the environment. In this design, natural gas is used to react with the oxygen produced in the electrolysis, reducing reduce the chemical potential difference across the electrolyzer, thus minimizing electricity consumption. The oxygen produced from the electrolysis is consumed in either a total oxidation or a partial oxidation reaction with natural gas. Experiments performed on single cells shown a voltage reduction as much as 1 V when compared to conventional electrolyzers. A heat recovery system (heat exchangers and catalytic converter) has been incorporated to the electrolyzer to obtain a high efficiency hydrogen production system. Results from a thermodynamic analysis show up to 70% efficiency with respect to primary energy source.
Second Law Analysis of a Combined Cycle With Integrated Compressor Inlet Air Cooling
Authors: Razani A. , Patterson M. , Kim K. J. 
Published: November 2021

Abstract
A gas/ammonia combined cycle is proposed in which exhaust gases from a Brayton gas topping cycle are used to produce superheated ammonia in a Heat Recovery Ammonia Generator (HRAG). To increase the power of the gas turbine in the combined cycle, when the environmental air temperature is high, inlet air to the compressor is cooled in the evaporator of an ammonia refrigeration cycle added to the combined air/ammonia power cycle. In this integrated combined power cycle a small fraction of high-pressure ammonia liquid, from the exit of the ammonia pump, is used in the ammonia refrigeration cycle to cool the air. The second law analysis and optimization of the above combined cycle is presented. The effect of important system parameters on the irreversibility of components in the cycle and the exergy of exhaust streams are evaluated. Reasonable constraints for system components are assumed. The power and efficiency of the cycle are evaluated and their dependences on system parameters are presented.