Effects Of Key Design Parameters Research Articles

Characterization and performance analysis of a shear thickening fluid damper

Shear thickening fluid is a smart material with rheological properties that can be rapidly varied by excitation changes. To fully explore the advantages of using shear thickening fluid in various devices, a phenomenological model for simulating complex viscosity characteristics of the shear thickening fluid has been developed, and an analytical model has been presented to predict the mechanical characteristics and performance of a damper filled with shear thickening fluid. Based on the analytical model, the force displacement curves are first analyzed for different excitation amplitudes and frequencies. Second, an investigation of the time history of the damping force at various excitation amplitudes is conducted. Finally, the effects of key design parameters on the force displacement and force velocity curves are discussed. The results show that the shear thickening fluid damper exhibits significant velocity correlation, and the damping force increased as the shear rate of shear thickening fluid increased until the threshold value. For the vibration with high frequency, or fast velocity, or large amplitude, the shear thickening fluid is easy to have high shear rate, which results in a great vibration control capability for the shear thickening fluid damper.

Determination of key parameters for sizing the heliostat field and thermal energy storage in solar tower power plants

The optimal sizing of the solar tower power plant with thermal energy storage is critical for increasing the system reliability and reducing the investment cost. However, the combined effects of key design parameters for sizing the solar tower power plants, including design direct normal irradiance, solar multiple and thermal storage hours, on the thermo-economic system performance under different solar resources are still unclear. In this study, a thermo-economic model for a 50 MW solar tower power plant based on steam Rankine cycle with molten salt storage has been developed to explore the optimal combinations of these parameters at four sites in China. The coupled relationship between these parameters and their effects on the annual electricity generation, solar-to-electricity efficiency and levelized cost of energy have been identified. The results show that the optimal design direct normal irradiance for minimal levelized cost of energy depends on both the annual irradiation level and the distribution of solar irradiance, which differs from the recommended values obtained from the traditional methods. It is found that the irradiation received by heliostats at the optimal design condition accounts for a specific percentage (i.e., 72–75%) of the annual irradiation for the cases in this study. The sensitive analysis by varying the main financial parameters indicates that the optimal design direct normal irradiance and the corresponding percentage slightly vary with the heliostat cost. The results can provide a theoretical reference for determining the optimal size of the heliostat field and thermal energy storage for solar tower power systems under different solar resources.

Thermo-fluid dynamics analysis of ITER Cryostat Space Room

This paper presents the results of an integrated numerical thermo-fluid dynamic analysis of the ITER Cryostat Space Room (CSR) with the primary goal of determining the temperature distribution of the Cryostat and Bio-Shield walls, during normal operating conditions. This has been possible by performing a global analysis of the integrated configuration of the machine properly accounting for the main structures between the driving heat sinks: the building area outside the Bio-Shield, the Tokamak basement and the Cryostat Thermal Shield. The results of this study may be used to support the validation of the input data and boundary conditions, which have been considered for the design of some critical components like the thermal shield as well as to provide preliminary information about the thermal conditions in specific areas of interest. Due to the complexity of the geometry a multi-step approach has been followed, including building-up a number of sub-models to determine equivalent properties to be used in global simulation models. Sensitivity studies have also been performed in some areas to study the effect of key design parameters.

Reprogrammable 3D Mesostructures Through Compressive Buckling of Thin Films with Prestrained Shape Memory Polymer

The mechanically guided assembly that relies on the compressive buckling of strategically patterned 2D thin films represents a robust route to complex 3D mesostructures in advanced materials and even functional micro-devices. Based on this approach, formation of complex 3D configurations with suspended curvy features or hierarchical geometries remains a challenge. In this paper, we incorporate the prestrained shape memory polymer in the 2D precursor design to enable local rolling deformations after the mechanical assembly through compressive buckling. A theoretical model captures quantitatively the effect of key design parameters on local rolling deformations. The combination of precisely controlled global buckling and local rolling expands substantially the range of accessible 3D configurations. The combined experimental and theoretical studies over a dozen of examples demonstrate the utility of the proposed strategy in achieving complex reprogrammable 3D mesostructures.

Engineering the Kinetics of Directed Self-Assembly of Block Copolymers toward Fast and Defect-Free Assembly.

Directed self-assembly (DSA) of block copolymers (BCPs) can achieve perfectly aligned structures at thermodynamic equilibrium, but the self-assembling morphology can become kinetically trapped in defective states. Understanding and optimizing the kinetic pathway toward domain alignment is crucial for enhancing process throughput and lowering defectivity to levels required for semiconductor manufacturing, but there is a dearth of experimental, three-dimensional studies of the kinetic pathways in DSA. Here, we combined arrested annealing and TEM tomography to probe the kinetics and structural evolution in the chemoepitaxy DSA of PS- b-PMMA with density multiplication. During the initial stages of annealing, BCP domains developed independently at first, with aligned structures at the template interface and randomly oriented domains at the top surface. As the grains coarsened, the assembly became cooperative throughout the film thickness, and a metastable stitch morphology was formed, representing a kinetic barrier. The stitch morphology had a three-dimensional structure consisting of both perpendicular and parallel lamellae. On the basis of the mechanistic information, we studied the effect of key design parameters on the kinetics and evolution of structures in DSA. Three types of structural evolutions were observed at different film thicknesses: (1) immediate alignment and fast assembly when thickness < L0 ( L0 = BCP natural periodicity); (2) formation of stitch morphology for 1.25-1.45 L0; (3) fingerprint formation when thickness >1.64 L0. We found that the DSA kinetics can be significantly improved by avoiding the formation of the metastable stitch morphology. Increasing template topography also enhanced the kinetics by increasing the PMMA guiding surface area. A combination of 0.75 L0 BCP thickness and 0.50 L0 template topography achieved perfect alignment over 100 times faster than the baseline process. This research demonstrates that an improved understanding of the evolution of structures during DSA can significantly improve the DSA process.

On the Heat Transfer Enhancement of Plate Fin Heat Exchanger

The plate fin heat exchanger is a compact heat exchanger applied in many industries because of its high thermal performance. To enhance the heat transfer of plate fin heat exchanger further, three new kinds of wavy plate fins, namely perforated wavy fin, staggered wavy fin and discontinuous wavy fin, are proposed and investigated by computational fluid dynamics (CFD) simulations. The effects of key design parameters, including that of waviness aspect ratios, perforation diameters, staggered ratios and breaking distance are investigated, respectively, with Reynolds number changes from 500 to 4500. It is found that due to the swirl flow and efficient mixing of the fluid, the proposed heat transfer enhancement techniques all have advantages over the traditional wavy fin. At the same time, serration is beneficial to reduce the friction factor, and the breaking technique can reduce heat transfer area. Through the performance evaluation criteria, the staggered wavy fin has an advantage over the small waviness aspect ratio; with increasing waviness aspect ratio, this predominance is gradually surpassed by the perforated wavy fin, and the advantage of the discontinuous fin is the smallest and almost invariable. A maximum performance evaluation criteria (PEC) as high as 1.24 can be obtained for the perforated wavy fin at the waviness aspect ratio γ = 0.45.

Conceptual design and preliminary performance analysis of a hybrid nuclear-solar power system with molten-salt packed-bed thermal energy storage for on-demand power supply

In support of more efficient utilization of solar and nuclear energy in power generation, the present work proposes a conceptual design of a hybrid nuclear-solar power system (HNSPS) for on-demand power supply, based on a parallel thermal integration of small modular reactors with commercialized molten-salt concentrating solar power tower plants. A cost-effective thermal energy storage system is employed as a thermal coupling and a heat dispatcher to coordinate both nuclear heat and solar heat with power demands. The overall configuration and operation strategy of the hybrid system are elaborated. A numerical model of the hybrid system is developed based on the circulation of molten-salt. Using the model, a 7-day performance analysis of the hybrid system with different considerations are conducted. Effects of key design parameters on system performances are investigated by a parametric study. A customized evaluation parameter, named as “design score”, is defined to assess the suitability of the designed configurations. The performance analysis shows that the integration of nuclear power with concentrating solar power allows the system to be less dependent on heat dispatch to achieve required power regulations, comparing to a standalone CSP plant with an equivalent power capacity. The parametric study indicates that a higher heat generation utilization of the hybrid system requires a larger TES and a smaller heliostats field, while a higher power supply efficiency of the hybrid system is accompanied with a larger TES, a larger heliostats field, and a higher nuclear power capacity proportion. The optimum design configuration of a 200 MWe HNSPS is estimated to have a nuclear power capacity proportion of 50%, a theoretical thermal energy storage duration of 14.8 h, and a heliostats field with a solar multiple of 1.27. This configuration can completely satisfy the power demand without any heat generation curtailment during the 7-day operation. The obtained results allow the HNSPS to be considered as a promising non-carbon-emitting power generation system for on-demand power supply.

Design and optimization of ARC less InGaP/GaAs single-/multi-junction solar cells with tunnel junction and back surface field layers

There has always been an inexorable interest in the solar industry in boosting the photovoltaic conversion efficiency. This paper presents a theoretical and numerical simulation study of the effects of key design parameters on the photoelectric performance of single junction (InGaP- or GaAs-based) and dual junction (InGaP/GaAs) inorganic solar cells. The influence of base layer thickness, base doping concentration, junction temperature, back surface field layer composition and thickness, and tunnel junction material, were correlated with open circuit voltage, short-circuit current, fill factor and power conversion efficiency performance. The InGaP/GaAs dual junction solar cell was optimized with the tunnel junction and back surface field designs, yielding a short-circuit current density of 20.71mAcm−2, open-circuit voltage of 2.44V and fill factor of 88.6%, and guaranteeing an optimal power conversion efficiency of at least 32.4% under 1 sun AM0 illumination even without an anti-reflective coating.

Review of the Savonius rotor's blade profile and its performance

The utilization of urban wind energy through small wind turbines has become an arising technology to ease the conflicts between rising energy demands in buildings and depletion of traditional energy resources. Many studies have reported that drag type vertical axis wind turbines have superior performance in the unsteady wind because of their attractive features. Several review studies have been conducted on these turbines. They mainly focused on the geometrical design parameters, the flow patterns, the research methodology, and the wind tunnel blockage correction. However, less research has been conducted to classify the Savonius rotor based on the classification criterion of the blade profile and has made a comprehensive performance comparison between different types of Savonius rotors. The blade profile is the essential design issue for a Savonius rotor; therefore, the variation of the blade profile will change the design parameters and affect the rotor's performance significantly. So, the classification based on the blade profile can not only present the effect of key design parameters on rotor's performance for each blade profile easily but also obtain the functional features of different profiles and the comparison among different profiles. Hence, in this article, we aim to summarize the classification of Savonius wind turbines according to the blade profile and present the development of this promising low speed generator.

Global Sensitivity Analysis of the Vibration Reduction System with Seated Human Body

The paper deals with the global sensitivity analysis for the purpose of shaping the vibroisolation properties of suspension systems under strictly defined operating conditions. The variance‐based method is used to evaluate an influence of nonlinear force characteristics on the system dynamics. The proposed sensitivity indices provide the basis for determining the effect of key design parameters on the vibration isolation performance. The vibration transmissibility behaviour of an exemplary seat suspension system is discussed in order to illustrate the developed methodology.

Analytical and experimental study on the seismic performance of cold-formed steel frames

This study aims to investigate the seismic performance of an innovative cold-formed steel (CFS) moment-resisting frame experimentally and analytically. A half-scale CFS moment-resisting portal frame was tested under static monotonic loading until failure. The frame consisted of two box-shaped columns (face-to-face channels connected with inside plates), a back-to-back lipped channel beam section and fully moment-resisting CFS bolted connections. During experimental tests, damage mostly concentrated at the top and bottom of the CFS columns due to the web crippling of the channels close to the connections, while no fracture or obvious slippage was observed at the connection zones. A detailed Finite Element (FE) model was developed using ABAQUS by taking into account the material non-linearity and geometrical imperfections. The lateral load-displacement behaviour, ultimate strength and failure modes predicted by the model were in very good agreement with the experimental results. The validated FE model was then used to assess the effects of key design parameters on the lateral load capacity, ultimate displacement, energy dissipation, ductility, and ductility reduction factor of the frame. It is shown that the proposed system can provide good seismic performance subjected to the appropriate design of the main structural elements. Increasing the axial load ratio of the columns by 50% resulted in 26%, 62%, and 50% decrease in the ultimate lateral load, energy dissipation capacity, and ductility ratio of the CFS frame, respectively. However, the energy dissipation capacity and the ductility ratio of the proposed system increased significantly by decreasing the width-to-thickness ratio of the columns.

Design Optimization of Transversely Laminated Synchronous Reluctance Machine for Flywheel Energy Storage System Using Response Surface Methodology

Design and optimization of synchronous reluctance machine for medium-speed flywheel energy storage system (FESS) applications is presented in this paper. High efficiency and high torque density are the main design criteria of the motor/generator system for electromechanical storage systems. Moreover, high salience ratio and appropriate stator design are required to achieve a high torque density and acceptable efficiency in synchronous reluctance machine. In this paper, the effects of key design parameters on the performance of the motor/generator system are investigated and an optimization procedure based on response surface methodology coupled to finite-element model is performed to achieve optimum value for stator and rotor parameters. The finite-element simulation results confirm that the performance of FESS improves significantly in comparison with initial design, by using the proposed design procedure. Finally, a prototype motor/generator system is implemented and experimental results are presented.

Optimal scheduling for wind-powered ammonia generation: Effects of key design parameters

Ammonia is a critical chemical to fertilize plants and feed the world. Recently, a first of its kind renewable ammonia plant has been built in Morris, MN, powered by wind energy. A broader deployment of such renewable plants will require careful selection of location and unit sizing to keep costs low and optimize the entire ammonia supply chain. In this paper, a 48-h receding horizon optimization problem is developed to optimally schedule unit set points for the system in order to minimize annual operating costs. This optimization formulation is then used to examine how the optimal operating cost depends on the key design parameters of location and unit size. Using the results obtained, simple correlations are developed which capture the dependence of operating costs on ratios of unit capacities, properly scaled to remove the dependence on location.

Parametric Design of an Ultrahigh-Head Pump-Turbine Runner Based on Multiobjective Optimization

Pumped hydro energy storage (PHES) is currently the only proven large-scale energy storage technology. Frequent changes between pump and turbine operations pose significant challenges in the design of a pump-turbine runner with high efficiency and stability, especially for ultrahigh-head reversible pump-turbine runners. In the present paper, a multiobjective optimization design system is used to develop an ultrahigh-head runner with good overall performance. An optimum configuration was selected from the optimization results. The effects of key design parameters—namely blade loading and blade lean—were then investigated in order to determine their effects on runner efficiency and cavitation characteristics. The paper highlights the guidelines for application of inverse design method to high-head reversible pump-turbine runners. Middle-loaded blade loading distribution on the hub, back-loaded distribution on the shroud, and large positive blade lean angle on the high pressure side are good for the improvement of runner power performance. The cavitation characteristic is mainly influenced by the blade loading distribution near the low pressure side, and large blade lean angles have a negative impact on runner cavitation characteristics.

Exergy-based optimization of an organic Rankine cycle (ORC) for waste heat recovery from an internal combustion engine (ICE)

In this study, exergy analysis of a two-parallel-step organic Rankine cycle (ORC) for waste heat recovery from an internal combustion engine (ICE) is performed. A novel two-step configuration to recover waste heat from the engine coolant fluid and the exhaust gas simultaneously is first introduced. The working fluids considered for this heat recovery system are R-123, R-134a, and water. A comprehensive thermodynamic modeling of the cycle was performed and optimization of the system was carried out to observe the simultaneous effect of key design parameters on the system performance. The net output power and the exergy efficiency were used as the objective functions with a goal of maximizing them. The design variables for this study are the first and second step pressures of the cycle, the pump and the expander isentropic efficiencies, and the exhaust gas temperature after waste heat recovery. The results show R-123 as the best working fluid under the considered conditions, which generates 468kW of net output power with an exergy efficiency of 21%. A sensitivity study was also performed on the optimized design to identify the component that impacts the ORC performance the most.

Effect of key design parameters on bacteria community and effluent pollutant concentrations in constructed wetlands using mathematical models.

Constructed wetlands are currently recognized as an effective environmental biotechnology for wastewater treatment, but the influence of their design parameters on internal functioning and contaminant removal efficiency is still under discussion. In this work, the effect of aspect ratio and water depth on bacteria communities as well as treatment efficiency of horizontal subsurface flow constructed wetlands (HSSF) under the Mediterranean climate was evaluated, using a mathematical model. For this purpose, experimental results from four pilot-scale wetlands of equal surface area but different aspect ratios and water depth were used. The HSSF system was fed with municipal wastewater. The experimental data were simulated using the BIO_PORE model, developed in the COMSOL Multiphysics™ platform. Simulations with the BIO_PORE model fitted well to the experimental results, showing a higher removal efficiency for the shallower HSSF for COD (93.7% removal efficiency) and ammonia nitrogen (73.8%). The aspect ratio had a weak relationship with the bacteria distribution and the removal efficiency. In contrast, the water depth was a factor. The results of the present study confirm a previous hypothesis in which depth has an important impact on the biochemical reactions causing contaminants transformation and degradation.

Combustion Characteristics of Ethanol/Liquid-Oxygen Rocket-Engine Combustor with Planar Pintle Injector

The pintle injector is a promising candidate for propellant-injection systems for various rocket engines. However, fundamental studies focusing on the pintle injector are rather limited, and the effects of key design parameters on combustion behaviors of the injector are still not identified. Therefore, combustion tests of an ethanol/liquid-oxygen rocket-engine combustor with a planar pintle injector are conducted to investigate the effects of total momentum ratio and on the combustion characteristics of the pintle injector. The total momentum ratio and vary from 1.0 to 2.2 and from 0.32 to 3.65, respectively, whereas the combustion pressure is kept constant at approximately 0.4 MPa. The spray structures are observed with high-speed cameras. The characteristic exhaust velocity () efficiency increases with the increase in in the fuel-centered configuration, and the opposite tendency is observed in the oxidizer-centered configuration. The efficiency decreases with the increase in the total momentum ratio due to the impingement of propellant droplets on the combustor wall. The effect of the total momentum ratio on the efficiency is larger in the oxidizer-centered configuration than that in the fuel-centered configuration due to the difference in the amount of the impinging propellant. The atomization characteristics are improved as the propellant-injection velocity increases, which results in the high efficiency.

Risk analysis of combined rainwater detention and pumping systems

Storm sewer systems (SSSs) are complex, with many hydraulic, mechanical and electrical components which may fail during natural extreme events, changing environmental conditions (including urban development), or simply due to poor maintenance. System complexity and management are important and still debated concepts within the framework of SSS risk analysis. A new probabilistic model for a conceptualized urban SSS, including a storage unit (SU) and a pumping station (PS), shows how single-component risk analysis can be extended to complex SSSs and demonstrates the combined effect of key design parameters (SU volume, detention time, prescribed outflow discharge) and management strategy on the overall SSS risk of failure. The risk of failure evaluated in a typical case study, demonstrates that economic restrictions leading to the loss of reliability of PS elements and the lack of redundant mechanical elements represent a major threat to SSSs and suggests a new risk-based definition of ’extended’ SU.

Theoretical model and design of electroadhesive pad with interdigitated electrodes

Electric fields alter adhesive forces between materials. Electroadhesive forces have been utilized in diverse applications ranging from climbing robots, electrostatic levitation to electro-sticky boards. However, the design of electroadhesive devices still largely relies on empirical or “trial-and-error” approaches. In this work, a theoretical model is presented to analyze the electrostatic field between the supporting wall and the electroadhesive device with periodic coplanar electrodes. The air-gap between the surface of electroadhesive device and the dielectric wall is explicitly taken into account in the model to consider its significant impact on electroadhesive forces. On the basis of this model, the electroadhesive force is calculated by using the Maxwell stress tensor. The effects of key design parameters and working environments on the electroadhesion behavior are further investigated. This study not only provides a tool to reveal the underlying mechanisms of electroadhesion but also suggests potential strategies to optimize novel electroadhesive devices for engineering applications.

Thermodynamic analysis and optimization of a two-stage organic Rankine cycle for liquefied natural gas cryogenic exergy recovery

A two-stage ORC (organic Rankine cycle) is proposed, by which low-grade heat of exhaust flue gas of a 123.5 MW gas-steam combined cycle power generating unit, as well as the cryogenic energy of LNG (liquefied natural gas) can be effectively recovered and utilized. R227ea and R116 are selected as working fluids for the system. Based on the thermodynamic mathematical models, the effects of key design parameters, including that of turbine inlet pressures, mass flow rates of working fluids and outlet steam fractions of evaporators on the system performance are investigated from the view of both thermodynamics and economics with CPP (cost per net power output) as the objective function. The results obtained the optimal inlet pressure of turbines, under which, the CPP has the minimum value. It is found that the CPP also decreases with the mass flow rate of R227ea and R116. The rate of absorbed heat in top cycle to that in bottom cycle has a positive impact on CPP, but very weak. The optimized two-stage ORC system can output net work with 1776.44 kW with the thermal efficiency of 25.64% and exergy efficiency of 31.02%. Cost per net power output is 6.3$/W, while the LNG temperature can be raised to 283.15 K.