bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparative Analysis of Thermal and Hydraulic Performance of a Mini-Channel Heat Sink With Supercritical Carbon Dioxide and Water Coolants
Authors: Mansur Yamin , Habib Md. Ahosan , Paul Titan C. , Morshed A. K. M. Monjur 
Published: February 2024

Abstract
This study investigates the heat transfer performance of supercritical carbon dioxide (s-CO2) in comparison to water as a coolant within circular tubes. The study was conducted numerically using the commercially available software FLUENT. The study was conducted for the s-CO2 for the temperature range of 305 K to 316 K at 8 MPa covering the pseudocritical temperature for the CO2. The thermal and hydraulic performance, including heat transfer coefficient and pressure drop, under varying inlet temperature, mass flux, and heat flux conditions, were evaluated and compared with those of water. The study finds that for s-CO2, the heat transfer coefficient reaches its peak value at the pseudocritical temperature, which is around 307.9K at an operating pressure of 8 MPa. The bulk fluid temperature ranging from 306 K to 308 K offers better thermal and hydraulic performance for s-CO2, with a higher heat transfer coefficient and lower pressure drop than water. However, beyond this temperature range, both the heat transfer coefficient and pressure drop of s-CO2 become worse than water. Furthermore, the study observes that the heat transfer coefficient for s-CO2 increases with mass flux, similar to water. However, the slope is steeper than water, and it becomes steepest at an inlet temperature of 308K. An interesting trend for s-CO2 is noted, as the heat transfer coefficient decreases with an increase in heat flux beyond the peak temperature (the temperature at which the maximum heat flux was observed). Conversely, the reverse scenario has been observed prior to the peak temperature. Water, on the other hand, does not show any significant change in this regard. The thermophysical properties of s-CO2, including specific heat capacity, density, thermal conductivity, and viscosity, around its pseudocritical temperature at 308 K (at 8 MPa) are critical for interpreting these results. The study identifies the optimum conditions at which s-CO2 proves to be better than conventional coolants such as water.
Thermal Characterization of Functionalized Nanodiamond Enhanced Phase Change Materials for Fast Response to Demand
Authors: Oliver Jared , Languri Ethan , Davidson Jim , Costa Lino , Kerns David 
Published: February 2024

Abstract
The latent thermal energy storage (TES) system is a well-known concept that utilizes the energy exchange from solid-liquid phase change for energy storage. TES can shift electrical demand from on-peak to off-peak hours, reducing costs and fuel that electrical power plants use to supply the energy needs of facilities. While TES can be very beneficial, the slow response rate commonly seen in TES is a major reason why industry hesitates to engage large-scale TES implementation. However, the response rate can be increased via the addition of higher conductivity particulates into PCMs that are commonly used in TES. This paper investigates the role of functionalized five-nanometer size diamonds, “nanodiamond” added to and interact with the molecules of PCMs to increase their thermal conductivity significantly, hence their response rate to thermal demands. Due to the extremely high thermal conductivity of diamonds and the utilization of five-nm particle-size diamonds chemically interfacing with the PCM host material, the thermal conductivity of the overall medium will increase significantly. However, there are downsides to increasing the response rate by adding particulates. Aside from displacing higher capacity materials, the addition of particulates that increase the overall thermal conductivity appear to reduce the latent heat of fusion of the materials. This paper studies the macro- and nano-scale characterizations of the base PCM and functionalized nanodiamonds in the PCMs.
Experimental Analysis of the Effect of Fluidic Oscillator Geometry on Heat Transfer Performance
Authors: Gomes Rita C. S. , Barbosa Flavia V. , Constantino Erany D. G. , Teixeira Senhorinha C. F. , Teixeira José C. F. 
Published: February 2024

Abstract
Fluidic oscillators are used in several areas such as acoustics, fluid mechanics, and heat transfer. These devices generate sweeping jets with different frequencies, operating without the need for external forces. Therefore, this study aims to experimentally analyze the geometric and dynamic parameters that influence the performance of oscillating jets. Based on this analysis, the geometry of a Double Feedback Loop (DFO) oscillator prototype was defined. The appropriate materials and manufacturing processes were carefully chosen for its construction and the design parameters were selected based on the factors and levels that mainly influence the dynamics of the sweeping jet flow according to an extensive literature review. The geometry of the feedback channel, mixing chamber, and control port were defined as a result. To investigate the effect of these variables on the flow dynamics, an experimental setup was meticulously designed and constructed. This setup enables the adjustment of the flow rate and the introduction of seeding particles into the system, allowing the characterization of flow dynamics using a Laser Doppler Anemometry system. Besides the analysis of the jet flow dynamics, the heat transfer rate was measured using a heat flux sensor, contributing to the determination of the optimal design.
The Effects of Balloon Thickness on the Viability of a Microfluidic Cell Compression Device
Authors: Emeigh Carson , Pineda Rose , Harms Brennan , Ryu Sangjin 
Published: February 2024

Abstract
Cells respond to mechanical stimuli, and microfluidic devices are used to create highly controlled environments for cellular mechanobiology studies. Previously, we developed a microfluidic cell compression device using photolithography and soft lithography. The device consisted of an array of thin polydimethylsiloxane (PDMS) balloons that would inflate under an applied pressure. Hydrogel scaffolds seeded with cells placed over these balloons were shown to be compressed during device operation. The height of the inflated balloons was found to depend on the balloon diameter, and the observed dependency was compared to a theoretical model. The theoretical model predicts that the balloon height is also affected by applied pressure, balloon thickness, and Young’s modulus and Poisson’s ratio of PDMS.
In this study, we investigated the effect of the balloon layer thickness on the height to which the balloons can be inflated, following the previous study. Two microfluidic cell compression devices with different balloon thicknesses were fabricated using a 3D printed plastic mold, PDMS, spin-coating, and soft lithography. The height and diameter of the balloons were measured by microscopy imaging and image processing. The device was redesigned to facilitate imaging and following image processing. Fabrication was also slightly altered to improve the control over the balloon thickness. Additionally, Young’s modulus of PDMS was experimentally measured.
We found that the balloon height increased with the balloon diameter as expected, but it did not show clear dependence on the balloon thickness, as predicted by the theoretical model. Disagreement with the theoretical model may be due to the assumptions of the model, and errors and uncertainties in fabrication, imaging, and image processing. Height measurements with a secondary method is required for validation of findings.
Effects of Deterministic Gust Modeling for Large, Multi-Rotor Drones
Authors: Hoang Samantha , Shen I. Y. 
Published: February 2024

Abstract
Multi-rotor drones are becoming increasingly popular as a method for accomplishing critical operations such as fighting fires, search and rescue, and agriculture. To accomplish these tasks, the drones need to fly over long distances and potentially carry heavy payloads. They also need to be capable of flying in harsh environments with sudden gust disturbances. When designing these drones, it is important to be able to accurately simulate their flight before building and testing the drone. This paper demonstrates that simulated flight trajectories of an 18-rotor drone, with an overall size of 3 m in diameter and 1 m tall, are very sensitive to various parameters of deterministic gust disturbances. A simple gust disturbance, where the magnitude of the wind, the wind direction, and the number of affected rotors were varied, was used to demonstrate this sensitivity. When the windspeed is varied for two wind directions, the amplitude of the oscillations in the trajectories grow with the increase in the wind amplitude. The amount of the variation was not consistent with the largest change of 2.0 m in trajectory corresponding to the smallest windspeed increase from 5 to 10 m/s at a constant angle of 45 degrees and inconsistent changes in the trajectory for selected windspeed variations. When the wind angle with vertical is varied at a constant windspeed of 20 m/s, the simulations demonstrated different responses depending on if the wind came from above or below the drone. The responses to wind coming from above the drone was larger than the responses to wind coming from below the drone by a factor of almost 100 when comparing the largest responses. Like when the windspeed was varied, there was no quantitative or qualitative predictability in the drone’s response. Finally, no similarities in response were observed when the number of affected rotors was varied. When half of the rotors are hit by the gust, the drone exhibits a 5 to 10 times larger horizontal response in both position and orientation than when all the rotors are hit by the gust. In contrast, the response in the vertical direction when only half of the rotors is hit by the gust is half the magnitude of the response when all of the drones are hit by the gust. These results demonstrate that the drone’s response to a gust disturbance is heavily dependent on the properties of the gust and are not predictable using deterministic simulations, thus demonstrating a need to use stochastic simulations to achieve accurate simulation results.
Impact of Number of Blades and Solidity on the Performance of a Darrieus Vertical Axis Wind Turbine With Helical Blades
Authors: Saad Ahmed S. , Ahmed Mahmoud 
Published: February 2024

Abstract
The number of blades and the solidity ratio for Darrieus vertical axis wind turbines are two factors that significantly influence the performance of these wind turbines. Therefore, the objective of the current study is to investigate the impact of varying numbers of blades (2, 3, and 4 blades) as well as various solidity ratios ranging from 0.3 to 0.65 on the performance of a helical-bladed Darrieus rotor with helical angle of 90 degrees. Accordingly, the Reynolds-Average Navier-Stokes equations in three dimensions along with the turbulent model of (SST) k-ω are developed and numerically simulated. In this study, experimental results from the literature are used to validate the results predicted by the current numerical model. Thus, numerical predictions of the variations of the coefficient of power versus tip speed ratio can be made.
Predicted results revealed that the coefficients of power are higher for the helical-bladed Darrieus rotor with three blades at higher ranges of tip speed ratios with respect to rotors with two and four blades. The peak coefficient of power significantly increases with raising the solidity ratio up to an optimal value 0.5, then a deterioration in peak coefficient of power is attained by a further increment of solidity ratio beyond this value. The helical Darrieus rotor with three blades and solidity ratio of 0.5 attains the highest peak coefficient of power of 0.338. Helical Darrieus rotors have a wide range of tip speed ratios at which high power coefficients can be achieved when the solidity is lower. Furthermore, as rotor solidity increases, the optimal tip speed ratio of the helical Darrieus rotor tends to decrease.
Renewable Convective Heating by the Metallic Strips Heated via a Solar Vacuum Tube
Authors: Alshweiki Ali , Olukeye Tiwaloluwa , Demisse Wondwosen , Tyagi Pawan 
Published: February 2024

Abstract
The majority of power consumption nowadays goes to heating. Global warming, air and water pollution caused by burning fossil fuel for heating encourage researchers and engineers to focus more on renewable energy. The solar system is one of Earth’s primary sources of clean power. Apart from photovoltaic panels and their effectiveness of power generation contribution, solar heaters are primarily used in different applications to recover heating needs in residential and commercial buildings. This paper focuses on an experimental study to generate heat by a solar system using metallic strips immersed in cement inside a solar vacuum tube. Heat can be transferred from inside the tube to the outside using metallic strips with high conductivity. Then, the metallic strips can be used as a heater to heat water or air in an isolated tank by direct contact between the hot strips and the fluid. In order to keep the system providing heat after the absence of sun’s rays, cement is used in this experiment as a heat repository.
Application of Modal Superposition Method With Response Dependent Nonlinear Modes on the Forced Response Analysis of Bolted Joint Connections
Authors: Beyan Humeyra , Cigeroglu Ender 
Published: February 2024

Abstract
Due to ease of mounting, high strength feature and availability, bolted joints are one of the most common and widely used connection methods. Nonlinear modeling of bolted joints is a complex problem. One common approach of modeling bolted joints is the use of macroslip friction elements distributed around the bolted connection. The use of multiple macroslip friction elements increases the computational time of the analysis. Therefore, in this study, in order to decrease the computational time Modal Superposition Method (MSM) with Response Dependent Nonlinear Modes (RDNMs) is utilized to obtain the solution of the jointed structures. RDNMs, which are calculated during the solution, are a special set of normal modes which captures the dynamics of the nonlinear problem much more accurately than linear modes of the system. Therefore, use of RDNMs decreases the number of modes that should be used in the analysis drastically. Hence, the dimension of the nonlinear algebraic equation set to be solved and the resultant solution time decrease significantly. The obtained form of nonlinear algebraic equation set is solved by using Newton’s method with arc-length continuation. A half-lap bolted joint is considered as a case study. Performance of classical MSM that uses linear modes of the system is compared with the MSM with RDNMs.
Advanced Exergetic Evaluation of a Stig Cycle and Cooled Inlet Air Gas Turbine Powered by Mixtures of Natural Gas and Hydrogen in Tropical Climates
Authors: Fajardo Juan , Barreto Deibys , Yabrudy Daniel , Piña-Martinez Andrés 
Published: February 2024

Abstract
Using mixtures of hydrogen and natural gas as primary energy sources in current power generation systems with gas turbines is one of the worldwide trends for global decarbonization goals. However, despite the problems of adaptation of the existing assets for the use of hydrogen, little has been studied about its effects on gas turbine generation systems that operate in tropical climatic conditions where temperatures are higher than 30 °C, and relative humidity reaches values higher than 80%.The gas turbine generator plant with steam injection and cooled air inlet studied consisted of a General Electric LM5000 gas turbogenerator composed of a low-pressure compressor, high-pressure compressor, combustion chambers, turbine, and generator. The steam injection system comprises a heat recovery steam generator and two MUP pumps. The air-cooling system comprises two electric coolers, a cooling tower, two pumps, a cooling coil, two evaporators in series, and two condensers in parallel. The air-cooling system allows for reaching the minimum temperature of 8.8 °C. Plant with Stig cycle in ISO conditions (15°C and 60% RH) produces 52 MW with a thermal efficiency of 43%. The atmospheric conditions in the geographical location of the power plant are, on average, 32°C and 80% relative humidity at sea level. Therefore, the plant with the Stig cycle under local operating conditions produces a power of 44.4 MW with a thermal energy efficiency of 41.6 %. A simulation was conducted in a Stig cycle generation system with a gas turbine, steam injection in the combustion chamber, and cooling air at 8.8°C at the compressor inlet. The system is set to produce 44.4 MW for fuel mix ranges between 0–50% hydrogen.
The study results showed that for every 5% by volume of hydrogen added to the H2-natural gas mixture, 5.6% kJ/m3 of energy is lost. Thermal efficiency decreases an average of 2.67% for every 10% increase in hydrogen, which forces an increase in the volume of the fuel mixture to generate the same power. For a percentage of 20% by volume of H2 in the fuel mixture, there are increases in global exergy destruction, avoidable exergy destruction, and unavoidable exergy destruction of 21.5%, 16%, and 31%, respectively. In comparison, the exergetic efficiency decreases by 13.7%. The component most affected by the use of the fuel mixture is the combustion chamber, in which exergy destruction increases by 17.8 MW compared to using 100% natural gas. In addition, the combustion chamber suffers an increase in exergy destruction of 29,2% for every 10% increase in the percentage of hydrogen injection in the fuel mixture. For every 10% increase in H2 volume, there is an average increase in the NOx concentration of 0.4% and a 5% decrease in the CO2 concentration.
Model Based Evaluation of a Turbocharged Engine Exhaust Heat Recovery by Auxiliary Turbine
Authors: Carapellucci Roberto , Di Battista Davide 
Published: February 2024

Abstract
Recent developments in terms of vehicle emissions and fuel consumption regulations have pushed the transportation sector toward electrification and hybridization of powertrains. In order to meet these environmental targets, a transition era, where the internal combustion engines (ICEs) still play a crucial role, is approaching, and technologies already mature should be rapidly applied to reduce fuel consumption. Waste heat recovery from exhaust gases has been studied for decades and can now be readly applied to existing engines, particularly in hybrid configurations, where the recovered energy is converted into electrical form and used on board. It is particularly important for heavy duty transportation, where the potential is enormous and the difficulties to fully electrify the powertrain are higher. Among various technologies proposed for waste heat recovery, the use of additional turbine in the engine exhaust is surely one of the most mature, although there are not many applications in the market. In this work, a 3.0 L turbocharged diesel engine, used to equip commercial and heavy duty vehicles, is considered. Having the opportunity to test the engine at representative working points, the potential of exhaust heat recovery using an additional turbine has been extensively explored. Data from the engine test bench has been used as a boundary condition to develop a mathematical model of the exhaust line and, in particular, the turbocharger. This is controlled by a variable geometry inlet nozzle, opening and closing a pre-statoric row of vanes on the turbine, in order to match the instantaneous requests of the compressor placed on the same shaft. Hence, a model of an auxiliary turbine has been derived and used to evaluate the possible energy recovery when it is placed downstream of the existing one (so-called series turbocompound). Results in terms of mechanical power produced (and possible electrical conversion) have been assessed, considering the real turbine behavior (expansion ratio vs. flow rate vs. revolution speed vs. efficiency) and has an average value of 6% in a wide range of operating conditions of the engine. The new thermodynamic conditions of the exhaust line have been re-evaluated, calculating the new equilibrium of the turbocharger when the additional turbine is introduced and its related backpressure increase on the exhaust, which can reduce the net power recovered value. In fact, the backpressure effect on the engine increases the specific fuel consumption, which should be compared to the benefit of the additional power produced by the turbocompound. Environmental considerations, such as the amount of CO2 avoided thanks to the recovery section, have been also calculated, showing very interesting results (averagely 45 g/kWh) considering emissions reduction policies worldwide and the electrification of fleets.
Dynamic Analysis of a Cracked Composite Beam
Authors: Sarker Pratik , Chakravarty Uttam K. 
Published: February 2024

Abstract
Composite materials tailored for specific applications exhibit customized properties which the ordinary materials do not possess. Therefore, performance analysis of composite materials for desired applications is important to ensure the longer life of the structure without failure. When subjected to dynamic loading, the crack growth and corresponding vibration behavior of the composite structures are of special interest. Therefore, in this research, vibration characteristics of a proposed cracked composite beam is investigated by conducting computational simulation. The composite structure is composed of four layers of fiberglass-epoxy material and a soft honeycomb structure sandwiched between the top and bottom layers of the composite material. Symmetric configurations of different ply angles of composites with respect to the midplane of the structure are used. The corresponding finite element model is created in the commercially available finite element package of Abaqus. A V-shaped crack is considered in the composite beam structure with various crack opening sizes. The variations of natural frequencies of vibration of the composite cracked beam with variations in the crack opening sizes are presented for different modes. Then the variations of natural frequencies with the depths and positions of the cracks along the length of the beam are studied. Variations of vibration characteristics are presented for the composite beam for the rotating and nonrotating cases. Convergence study for the solution accuracy of the beam is conducted for both the rotating and nonrotating cases.
Brake System Dynamics and Control for an Autonomous Personal Rapid Transit Vehicle
Authors: Patil Nikhil , Best Dustin , Hollar Seth 
Published: February 2024

Abstract
This paper presents an overview of the brake system development and control strategy for an autonomous personal rapid transit vehicle prototype. An electro-hydraulic system is developed using a set of electric linear actuators and master cylinders to allow the onboard computer to stop the vehicle or control the speed. A classical electronic braking force distribution is incorporated into the system to maximize deceleration and avoid wheel lock-up during emergency braking. The incompressible braking fluid yields fast response time for brake pressure gain, thus a spring loaded mechanism is introduced to obtain higher resolution in controlling the brake gain and subsequently the vehicle’s deceleration. The authors propose an optimal control strategy based on Pontryagin’s minimum principle for vehicle speed reduction to improve passenger comfort by reducing acceleration during the braking duration. The optimization problem is set up to be simulated in Matlab Simulink environment, and results are discussed.