Power Density Distribution Research Articles

Tidal stream energy resource characterization in the Salish Sea

The Salish Sea, a large estuary on the Pacific Northwest coast, represents a great tidal stream resource because of its strong tidal currents in many tidal channels. However, the tidal energy resource in the Salish Sea has not been systematically characterized. This paper presents a modeling study conducted to characterize the tidal energy resource in the Salish Sea based on a high-resolution tidal hydrodynamic model, which was validated using data derived from 10 tide gauges and 132 current stations. A total of 16 tidal channels with strong currents were identified as hotspots for potential tidal energy development in the Salish Sea. Probability distributions and exceedance of the cross-channel average velocity were calculated at all 16 channels based on international standards for tidal energy resource characterization. The tidal energy resource at the 16 hotspots was also characterized using power density distributions and kinetic energy fluxes. The ranking of the kinetic energy fluxes suggested that Admiralty Inlet, Rosario Strait, and Middle Channel are the top three tidal energy hotspots in the Salish Sea. The study demonstrated the need of a high-resolution modeling framework for accurate simulation of tidal currents in large complex estuarine systems, in the context of tidal resource characterization and assessment.

Power Density and Electric Field Distribution at End-turn Stress Grading System of Inverter-fed Rotating Machine under PWM Waveform

Power Density and Electric Field Distribution at End-turn Stress Grading System of Inverter-fed Rotating Machine under PWM Waveform

The Laser Alloying Process of Ductile Cast Iron Surface with Titanium

The article presents the results of the laser alloying process of ductile cast iron EN-GJS 350-22 surface with titanium. The laser alloying process was conducted on 2 kW high power diode laser (HPDDL) Rofin Sinar DL02 with rectangular focus and uniform power density distribution in the focus axis. The laser alloying was conducted with constant laser beam power and processing speed with titanium powder feed rate variation. The tests of the produced surface layers included macrostructure and microstructure observations, X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) analysis, Vickers hardness, and solid particle erosion according to ASTM G76-04 standard. To assess the erosion mechanism, SEM observations of worn surfaces after erosive test were carried out. As a result of laser alloying of a ductile cast iron surface, the in situ metal-matrix composite structure was formed with TiC reinforcing particles. The microstructure change resulted in the increase of surface layers hardness and erosion resistance in comparison to the base material.

Hybrid model of radio-frequency low-pressure inductively coupled plasma discharge with self-consistent electron energy distribution and 2D electric field distribution

Low-pressure radio-frequency (RF) inductively coupled plasmas (ICPs) are extensively used for materials processing. In this work, we have developed a hybrid model consisting of two-dimensional (2D) Maxwell equations with an open boundary, zero-dimensional Boltzmann equation under linear and quasilinear approximations, and a power balance equation. The hybrid model is capable of achieving a self-consistent description of the electron heating mechanism and electron kinetics for the RF ICPs at low pressures. This work presents an investigation of the influence of operating conditions on 2D distributions of electric field and power density, normalized electron energy probability function (EEPF) (effective electron temperature), and plasma density in a low-pressure RF Ar ICP using the hybrid model. The results show that the RF frequency and absorption power significantly affect the 2D distributions and amplitudes of electric field and power density. The normalized EEPF is almost independent of RF frequency and weakly dependent on absorption power but significantly modulated by pressure at low RF frequency. The plasma density is also almost independent of RF frequency but increases with absorption power and pressure. In addition, we have validated the hybrid model against experimental data obtained in the driver region of a two-chamber RF Ar ICP source, where the RF frequency is 13.56 MHz, the power range is 200–1000 W and the pressure range is 0.1–1.0 Pa. The hybrid model qualitatively (and even quantitatively for some cases) reproduces the experimentally normalized EEPF and plasma density. The discrepancies in these plasma parameters could be attributed to the simplified collision processes taken into account in the hybrid model. The developed hybrid model can help us to better understand the effect of discharge conditions on electron kinetics and electron heating mechanism, and to ultimately optimize the parameters of RF ICP sources.

Unstructured Mesh–Based Neutronics and Thermomechanics Coupled Steady-State Analysis on Advanced Three-Dimensional Fuel Elements with Monte Carlo Code iMC

A thermomechanical fuel performance analysis module is implemented in the Korea Advanced Institute of Science and Technology Monte Carlo (MC) neutron transport code iMC. The module is designed particularly for advanced three-dimensional (3-D) fuel concepts, so an unstructured tetrahedral mesh grid is adopted for geometry flexibility. The cellwise detailed power density distribution is tallied from the MC transport and transferred to the thermomechanics module for the heat transfer, thermal expansion, and stress analysis. In this paper, a recently proposed 3-D fuel concept called the centrally shielded burnable absorber (CSBA) model was considered for numerical studies. Several fuel models were solved by the iMC code: a single CSBA pellet, a three-ball–loaded CSBA pellet, and a CSBA fuel-loaded 17 × 17 fuel assembly. From the analysis results, it was discovered that the uncertainty of the detailed power density distribution hardly affects the uncertainty of the thermomechanical analysis due to dissipation via conduction. Also, the importance of using detailed intrafuel power distribution data in such a thermal neutron spectrum has been demonstrated, showing about 30 K overestimation of peak temperature compared to the conventional uniform power assumption.

Analysis of Electromagnetic Field Distribution Generated in an Semi-Anechoic Chamber in Aspect of RF Harvesters Testing

The results of work in the field of analysis of the distribution of electromagnetic fields generated by the antenna of an RFID reader operating in the UHF frequency band have been presented in this paper. The carried-out tests concern the efficiency of obtaining energy from the field of an electromagnetic RFID reader. To analyze the distribution of the electric field strength, the calculation procedures were elaborated on the basis of the developed mathematical dependencies in the MathCad program. The developed numerical procedures enable the synthesis of the electric field strength and power density distribution for a given antenna radiation pattern, for any suspension heights of the transmit and receive antennas and any mutual distance between them. In order to verify the correctness of calculations the test stands and measurements were made for a model antenna. The measurements were carried out in a semi-anechoic chamber.

Thermal Effect of a Revolving Gaussian Beam on Activating Heat-Sensitive Nociceptors in Skin

We consider the problem of inducing withdrawal reflex on a test subject by exposing the subject’s skin to an electromagnetic beam. Heat-sensitive nociceptors in the skin are activated wherever the temperature is above the activation temperature. Withdrawal reflex occurs when the activated volume reaches a threshold. Previously we studied static beams with 3 types of power density distribution: Gaussian, super-Gaussian, and flat-top. We found that the flaptop is the best and the Gaussian is the worst in their performance with regard to 1) minimizing the time to withdrawal reflex, 2) minimizing the energy consumption and 3) minimizing the maximum temperature increase. The less-than-desirable performance of Gaussian beams is attributed to the uneven distribution of power density resulting in low energy efficiency: near the beam center the high power density does not contribute proportionally to increasing the activated volume; outside the beam effective radius the low power density fails to activate nociceptors. To overcome the drawbacks of Gaussian beams, in this study, we revolve a Gaussian beam around a fixed point to make the power density more uniformly distributed. We optimize the performance over two parameters: the spot size of static beam and the radius of beam revolution. We find that in comparison with a static Gaussian beam, a revolving Gaussian beam can reduce the energy consumption, and at the same time lower the maximum temperature.

Investigation and optimization of the ultra-thin metallic bipolar plate multi-stage forming for proton exchange membrane fuel cell

Multi-stage forming of the ultra-thin metallic sheets is a promising process for manufacturing fine width and high aspect ratio bipolar plates in proton exchange membrane fuel cell. Correlations between the processing parameters and the channel quality evaluation indicators are investigated experimentally and numerically. A novel parameter optimization method and stage number design guidance are established with the consideration of the indicator priorities and material properties. The forming depth can be increased by larger Stage II punch stroke along with smaller clearance and radius. Increasing or decreasing the Stage II punch stroke and radius simultaneously contributes to larger draft angle. Small Stage II punch stroke and radius are beneficial to greater rib width. More uniform thickness distribution can be achieved by using smaller Stage II punch stroke and clearance. Two-stage forming is enough for soft materials and three-stage forming is suitable for relatively hard materials. Both the output power density and voltage distribution uniformity of the proton exchange membrane fuel cell are improved by employing multi-sage formed bipolar plates. The relationship between the parameters and indicators, optimization method, stage number design guidelines, all serve as the design principles of the micro channel's multi-stage forming for bipolar plates with ultra-thin metallic sheets.

Investigation of Criticality and Relative Power Density Distribution in VVER-1000 Nuclear Power Reactor

Nükleer güç reaktörlerinin tasarımının ve güvenle çalışmasının en önemli öğelerinden biri, kritiklik ve bağıl güç yoğunluk dağılımının incelenmesidir. Bu çalışmada VVER-1000'in kritiklik ve bağıl güç yoğunluk dağılımını içeren nötronik performans analizleri MCNP nötronik kod yardımıyla hesaplanmıştır. Dört farklı yakıt tipi için nötronik hesaplamalar gerçekleştirilmiştir. Her bir yakıt demeti için yapılan hesaplamalar sonucunda reaktör korunda kritiklik ve bağıl güç yoğunluk dağılımları elde edilmiştir. Bu çalışmada elde edilen sonuçlar literatürle karşılaştırılmış ve elde edilen kritiklik ve bağıl güç yoğunluk dağılımı değerlerinin birbirleriyle benzerlik gösterdiği görülmüştür.

Continuous flow microwave system with helical tubes for liquid food heating

Abstract The structural parameters of tubes (straight or helical tubes) might affect the heating liquid foods in continuous flow microwave system. Therefore, the objectives were to build a mathematical model for continuous flow microwave heating system with helical tubes for liquid foods heating. A finite element calculation was used for the model, and distilled water, as a representative of liquid foods, was used to validate experimentally and numerically. This model was employed to analyze the liquid heating efficiency with different pitch circle diameters (PCDs), tube diameters, and screw pitches of helical tubes. The heating efficiency was affected by electromagnetic power density distribution, secondary flow intensity, and dielectric properties of heated fluid. Furthermore, the optimal heating efficiency with these variations were given. This study is expected to provide advice to enhance the heating efficiency of liquid foods in design and optimization studies for continuous flow microwave system.

Femtosecond laser polishing of SiC/SiC composites: Effect of incident angle on surface topography and oxidation

In this article, a new ultrafast laser polishing method for SiC/SiC composites was reported and the effects of different incident angles were discussed in detail. The results indicated that the incident angle had a great influence on the polishing of SiC/SiC composites. Under the normal incident condition, the surface roughness was barely improved and the laser-induced defects even degraded the process quality. With the increasing incident angle, surface oxidation and defects dramatically decreased. At 80 degrees, the surface convex structure is almost eliminated and the protruding fiber was neatly cut off. Furthermore, a theoretical model of laser polishing for SiC/SiC composites is used to analyze the laser propagation and power density distribution in different incident angles. The model successfully predicted the laser energy resonance enhancement and illustrated the formation mechanism of laser-induced defects and nanoripples. Meanwhile, the result shows that the laser energy concentrated on the convex fiber of composites as the incident angle increased, which explained that the SiC/SiC composites polishing quality was significantly improved under the inclined incident condition.

Research of various inductors configurations for heating titanium slabs

In this paper various inductors configurations for heating a titanium slab, as well as the influence of frequency changes on efficiency of inductors are considered. The calculations are carried out by means of finite element method. In this research a three-dimensional time-harmonic model in A-formulation of Maxwell’s equations is used. In the framework of this work, only electromagnetic problem was calculated, since the main aim of this work is to assess the effectiveness of inductor configurations in terms of electromagnetic problem. Efficiency of inductor and the uniformity coefficient introduced herein have been chosen as the comparison parameters. Ultimately, distribution of electromagnetic power density in the workpiece is shown, also conclusions are drawn for each of inductor configurations.

Power density dynamics in a nuclear reactor with an extended in-core pulse-periodic neutron source based on a magnetic trap

The article examines the features of the spatial kinetics of an innovative hybrid nuclear power facility with an extended neutron source based on a magnetic trap. The fusion-fission facility under study includes a reactor plant, the core of which consists of an assembly of thorium-plutonium fuel blocks of the HGTRU reactor of a unified design and a long magnetic trap that penetrates the near-axial region of the core. The engineering solution for the neutron plasma generator is based on an operating gas-dynamic trap based on a fusion neutron source (GDT-FNS) developed at the Novosibirsk G.I. Budker Nuclear Physics Institute of the Siberian Branch of the Russian Academy of Sciences. The GDT-FNS high-temperature plasma pinch is formed in pulse-periodic mode in the investigated hybrid facility configuration, and, at a certain pulse rate, one should expect the formation of a fission wave that diverges from the axial part of the system and propagates throughout the fuel block assembly in a time correlation with the fast D-D neutron pulse source. In these conditions, it is essential to study the fission wave propagation process and, accordingly, the power density distribution formation within the facility blanket. The paper presents the results of a study on the steady-state and space-time performances of neutron fluxes and the power density dynamics in the facility under investigation. The steady-state neutronic performance and the space-time fission wave propagation were simulated using the PRIZMA software package developed at FSUE RFNC-VNIITF.

Design research for the porous hexagonal prism shaped fuel element adopted in nuclear thermal propulsion reactor based on neutronics and thermal-hydraulics coupled method

The Porous hexagonal prism shaped fuel element has the advantages of simple structure, high reliability and good practicability. It has been widely adopted by many nuclear thermal propulsion (NTP) reactor designs. A design method is present in this paper for determining key geometrical parameters of the porous hexagonal prism shaped fuel element. Four sets of fuel elements geometrical parameters are involved, including cases of 127, 169, 217 and 271 cooling passages. And they adopt different flow hole void fractions to have the same distance between adjacent cooling passages, this is done in order to ensure the reliability of fuel element. Three-dimensional neutronics/thermal-hydraulics coupled analyses of them are conducted to study their thermal hydraulic performances. The distributions of power density, coolant mass flow, temperature, coolant velocity and total pressure are obtained. The results indicate that the fuel element with larger numbers of cooling passages and smaller flow hole void fraction tends to have more uniform flow distribution, and the heat transfer efficiency of fuel element is improved at the same time. But those performance improvements by increase in numbers of cooling passages become much smaller when the number of cooling passages exceeds a certain value. Meanwhile, each additional of cooling passages would lead to almost doubled increase in the flow resistance of fuel element. Finally, through contrastive analyses, one set of geometric parameters is considered as the optimal choice which could ensures excellent heat transfer performance and relatively low flow resistance. This study could help set appropriate geometrical parameters for porous hexagonal prism shaped fuel element, thus being beneficial to improve the thermal-hydraulic performance of NTP reactor.

Microwave assisted sintering of Na-β’’-Al2O3 in single mode cavities: Insights in the use of 2450 MHz frequency and preliminary experiments at 5800 MHz

Microwave assisted sintering of Na-β’’-Al2O3 in single mode cavities was accurately investigated. The use of single mode cavity allowed monitoring the parameters affecting the sintering process, like the forward power, together with the temperature evolution, making possible to perform energy efficiency and specific energy consumption evaluations. Experiments have been performed at the frequency of 2450 MHz, but preliminary results are also reported using the higher frequency of 5800 MHz, in order to investigate its effect on important parameters like the power density distribution as well as the penetration depth, which are responsible of the resulting heating rate and sintering outcome. Dielectric properties of the powders were measured as a function of temperature in order to partially predict and support the understanding of their experimental heating behaviour. Furthermore, dielectric properties provide the fundamental information needed for the multiphysics numerical simulation, performed with the aim to reach insights into the power density evolution in the specimen as sintering proceeds.

Performance evaluation of a wind farm using different power density distributions

ABSTRACT Several wind resource assessment studies showed that the various power density functions (PDFs) were not always able to reproduce the wind regime available in different regions. Moreover, the impact of the PDFs on the assessment of wind farm performance was not widely investigated. Thereby, in the present study, the generalized extreme value (GEV), Weibull and Normal distributions are considered to investigate whether the expected performances of an actual wind farm are well predicted. This study is applied to Kaberten wind park located at Adrar, in south of Algeria. First, the selected PDFs are applied to analyze wind data collected at the meteorological station of Adrar. Then, the expected annual energy production (AEP), capacity factor and number of operating and non-operating hours of the wind park are computed using the PDFs. Thereafter, these predicted performances are compared to actual data of Kaberten wind park, and errors are assessed for every PDF. The results show that the errors on the mean wind speed are less than 0.5% for the three PDFs, whereas the available wind power density relative error varies from about 2.5% for Weibull to 20.9% for GEV, while it is about 5.9% for Normal distribution. Nevertheless, the AEP errors vary from about 8% for the GEV distribution to more than 24% for the two other distributions. Thus, these results indicate that for the studied case, the three PDFs are comparable for estimating the average wind speed, while the GEV distribution is more suitable for estimating the AEP.

Maximization of wave power extraction of a heave point absorber with a sea-state-based causal control algorithm

A causal control strategy is developed to tackle the non-causality arising in the real-time implementation of optimal wave energy control. The proposed control strategy utilizes a causal approximation transfer function to link the current wave force to the desired buoy velocity so as to eliminate the non-causality. An optimum model of the approximation transfer function is derived considering the power density distribution of the local wave spectrum. Based on the optimized approximation transfer function, the desired buoy velocity is achieved by tuning the power take-off mechanical force with the PID control. The efficiency of the proposed causal control strategy is assessed for a heaving point-absorber, in a set of random wave conditions. Generally, the heaving point-absorber could extract wave power up to 90% of the theoretical upper bound using the proposed control strategy. The sensitivity of the proposed control to viscous damping effect due to drag and wave spectrum bandwidth is investigated. Although it is less efficient in broad-banded sea state, the control efficiency is still within an acceptable level (above 70%).

The Study of Ocean Wave and Wave Power Observations by Synthetic Aperture Radar in Nearshore Waters

Wan, Y.; Zheng, C.W.; Zhang, J.; Dai, Y.; Li, L.; Qu, X., and Zhang, X., 2020. The Study of Ocean Wave and Wave Power Observations by Synthetic Aperture Radar in Nearshore Waters. In: Zheng, C.W.; Wang, Q.; Zhan, C., and Yang, S.B. (eds.),Air-Sea Interaction and Coastal Environments of the Maritime Polar Silk Roads.Journal of Coastal Research, Special Issue No. 99, pp. 9-15. Coconut Creek (Florida), ISSN 0749-0208.Based on 2 RADARSAT-2 SAR (Synthetic Aperture Radar) SLC (Single Look Complex) data and the cross-spectrum method, the distributions of significant wave heights and mean wave periods of ocean wave were inverted, and the distributions of the wave power density, which can represent the wave power, were calculated. Some comparisons between the results of the SAR and those of the ECMWF (European Center for Medium-Range Weather Forecasts) dataset were carried out, and the observation ability for the distribution characteristics of wave and wave power by the SAR was studied in detail. The results show that compared with buoys, which are single-point observations, and wave models, which are simulated observations, the SAR is an ideal tool for extensive wave observations in nearshore waters. The advantage of SAR observations is that some fine structure and microcosmic changes in wave and wave power can be found, which helps us understand the internal structure and transformation patterns of wave better. Therefore, the SAR showed extremely extensive application prospects in the field of wave observations. The contributions in this paper will provide some references for researchers aiming for ocean wave detection by remote sensing and promote the application level of SAR in the detection of wave and wave power.

Development of Core Monitoring System for a Nuclear Power Plant using Artificial Neural Network Technique

Core Monitoring System (CMS) has been developed to estimate Power Peaking Factors and other reactor physics safety parameters in normal power mode for core surveillance of Chashma Nuclear Power Plant Unit-1 (C-1). The CMS is based on the combination of Artificial Neural Network Technique (ANNT) and INCOPW processing code. The CMS methodology utilizes four inputs i.e. Power level, T4 control bank position, Effective Full Power Days (EFPDs) and individual burnup of 30 Fuel Assemblies. Seventy reactor operation states with different power density distributions are selected from five fuel cycles of C-1 for ANNT training. The CMS takes input parameters in real time and calculates output parameters. The CMS has been validated online at C-1 during cycle-11. The results indicate that CMS can be used for real time core monitoring of Chashma reactors. It would be beneficial for Chashma reactors to increase time interval between in-core flux maps from 30 to 90 EFPDs.

Microwave assisted freezing part 1: Experimental investigation and numerical modeling

The aim of this study was to develop an innovative process dedicated to enhancing the quality of frozen food using microwaves. A microwave assisted freezing device was designed at the laboratory scale to perform experiments in controlled conditions. Small samples of methylcellulose gels were frozen using nitrogen gas in a TE10 waveguide, where microwaves at 2.45 GHz were emitted intermittently or continuously. A numerical model was also developed to obtain results difficult to measure such as the local electric field and the corresponding energy density. The phase change part of the model was based on an enthalpy formulation and on the growth of spherical ice crystals. An original “hybrid 2D-3D” solving methodology was used to reduce the duration of the simulations. Favourable comparisons between the predicted temperatures and the experimental data highlighted the relevance of the models used for the thermophysical and dielectric properties. The analysis of the interactions between microwaves and matter, performed with numerical simulations, revealed the role of the freezing front as a boundary. The strong influence of sample size and of dielectric properties on the power density distribution were also illustrated when comparing our results with those published previously. The scientific knowledge obtained through this study and the original structure of the numerical model will be used to optimize microwave assisted freezing and link the process parameters to the reduction of ice crystal size highlighted in the companion paper. Industrial relevanceMicrowave assistance during freezing can improve frozen product quality by reducing ice crystal size. This innovative and promising process has not yet been given much attention. Developing an accurate model which describes microwave – matter interactions during phase change permits numerical simulations that can facilitate the design of industrial equipment, and determine optimal product dimensions.