AC Power Supply Research Articles

Effects of Decay Heat Distribution on Water Temperature in a Spent Fuel Pit and Prediction Errors With a One-Region Model

Abstract A prediction system with a one-region (1R) model was developed to predict water temperature in a spent fuel pit (SFP) after the shutdown of its cooling systems based on three-dimensional (3D) thermal-hydraulic behavior computed by using the computational fluid dynamics (CFD) software, FLUENT 6.3.26. The system was later extended to compute the water level in the SFP during the loss of all AC power supplies. This study aimed at confirming the applicability of the 1R model by the comparison of 3D computation results and 1R calculation results. Some of the effects that influence the SFP water temperature increase are decay heat and its distribution. Also, decay heat decreases with time, so for low decay heat, natural circulation force in the SFP becomes weak and the effect of heat loss to air for the water temperature increase will be relatively bigger than that for high decay heat. Therefore, in this study, the 3D computations with FLUENT 15.0 were done for four typical patterns of decay heat distribution and for three decay heat values (10, 5, and 1-MW). The computational results were compared to each other and evaluated. It was found that the effects of decay heat distribution were small on water temperature calculations, and the 1R model for SFP water was applicable to the prediction of SFP water temperature during the loss of all AC power supplies without consideration of the decay heat distribution.

Enhanced Degradation of Benzene in Surface/Packed-Bed Hybrid Discharge System: Optimization of the Reactor Structure and Electrical Parameters

The effects of reactor structure parameters (wire diameter of the coil electrode, screw pitch of the coil electrode, inner diameter of the quartz tube, and packing material) and electrical parameters (power supply mode, pulse repetitive frequency, and pulse-forming capacitance) on discharge characteristics and benzene degradation have been systematically investigated in a surface/packed-bed hybrid discharge (SPBHD) reactor. The experimental results indicate that the coil electrode with a wire diameter of 1 mm and a screw pitch of 7.5 mm appears to be more advantageous with respect to both degradation efficiency and energy yield (EY). The quartz tube with larger diameter is more beneficial to benzene degradation but not for $EY$ . The reactor packed with BaTiO3 hollow cylinders can decompose benzene more effectively than that packed with the other materials, but goes against $EY$ . The reactor driven by bipolar pulsed power supply favors the generation of energetic electrons and active species than ac power supply, and thus accelerates benzene degradation. Increasing the pulse voltage and pulse repetitive frequency are found to be favorable for improving energy injected into the SPBHD reactor as well as the benzene degradation, while more energy is consumed. In this system, ${f}=50$ Hz and ${C}_{{p}}=2$ nF are the optimal pulse repetitive frequency and pulse-forming capacitance for the bipolar pulsed power, respectively, after considering the benzene degradation and $EY$ comprehensively.

Thermistor based, low velocity isothermal, air flow sensor

The semiconductor thermistor technology is applied as a flow sensor to measure low isothermal air velocities (<2 ms−1). The sensor is subjected to heating and cooling cycles controlled by a multifunctional timer. In the heating stage, the alternating current of a main AC power supply source guarantees a uniform thermistor temperature distribution. The conditioning circuit assures an adequate increase of the sensors temperature and avoids the thermal disturbance of the flow. The power supply interruption reduces the consumption from the source and extends the sensors life time. In the cooling stage, the resistance variation of the flow sensor is recorded by the measuring chain. The resistive sensor parameters proposed vary significantly and feature a high sensitivity to the flow velocity. With the aid of a computer, the data transfer, storage and analysis provides a great advantage over the traditional local anemometer readings. The data acquisition chain has a good repeatability and low standard uncertainties. The proposed method measures isothermal air mean velocities from 0.1 ms−1 to 2 ms−1 with a standard uncertainty error less than 4%.

Using Square Wave Input for Wireless Power Transfer

A wireless power transfer (WPT) circuit is composed of a transmitting circuit with an AC power supply and a receiving circuit with a load, and the circuits are wirelessly connected each other. Then a designer chooses the wave form of the AC power supply. Many papers about WPT adopt a sinusoidal wave as the input. The frequency of the sinusoidal wave is generally determined to the resonant frequency of the circuit for high power transfer. Since the number of circuit elements in the power supply to generate a square wave is much less than that of a sinusoidal wave, WPT with a square wave input should be treated. In fact, some papers about WPT adopt a square wave as the input, and adjust the frequency of the square wave to the resonant frequency of the circuit. In this paper, we examine how the frequency of a square wave input affects power and efficiency of WPT circuits, and propose a procedure how to determine the frequency of the input to improve power and efficiency. Finally we discuss which wave should be adopted as an input and how the frequency of the input should be determined, regardless of whether resonant phenomena occur or not.

Unsolved issues related to thermal-hydraulics in the suppression chamber during Fukushima Daiichi accident progressions

ABSTRACTOn 11 March 2011, the Great East Japan Earthquake and Tsunami hit the Fukushima Daiichi Nuclear Power Station. The Fukushima Daiichi Units 1–3 lost all DC and AC power supplies, which set in motion a chain of events that led to releases of radioactivity to the environment. Since then, TEPCO has made many efforts to investigate the accident progressions and the status of the reactors and containment vessels. However, there still exist several tens of unsolved issues to be investigated for the fully understanding of the accident. In this paper, we introduce the unsolved issues related to thermal-hydraulics in the suppression chamber during the Fukushima Daiichi accident progressions. Especially, in Units 2 and 3, there are possibilities that thermal stratification inside their suppression chambers played an important role. It is important that these phenomena are addressed following both theoretical and experimental approaches as support to severe accident simulations.

Critical heat flux of highly subcooled water flow boiling in circular tubes with and without internal twisted tapes under high mass fluxes

This study focuses on the critical heat flux (CHF) of highly subcooled water flow boiling under high mass fluxes, particularly with respect to the thermal–hydraulics analysis in fusion reactor components. The experiments were performed in vertical circular tubes those were uniformly heated by a large AC power supply. Twisted tape was employed to induce swirl flow in order to further enhance the subcooled CHF. This study obtained several high CHF data points in both smooth tubes and twisted-tape tubes, which can enhance relevant high-CHF databases. The influences of thermodynamic quality, mass flux, pressure, and twisted tape on subcooled CHF were discussed. The results show that twisted tapes can allow significant increase in subcooled CHF under high mass fluxes. The CHF enhancement effect is more obvious when using twisted tapes with smaller twist ratios. Available existing subcooled CHF correlations were compared with the experimental data from the present and others’ studies for both smooth tubes and twisted-tape tubes. For smooth tubes, the CHF look-up table has satisfactory prediction accuracy. For twisted-tape tubes, a modified correlation of Arment et al. was proposed to predict the swirl-flow subcooled CHF.

&lt;i&gt;In-Situ&lt;/i&gt; Domestic Load Harmonic Detection and Reduction Based on GLRM Algorithm for Optimum Filter Excerpt

Power Quality measures the reliable operation between the system and to the connected loads of same system. A poor power quality causes physical damage to the equipment and also results in lower productivity with increase in energy costs. Power disturbances range from micro seconds to hours and the prolonged disturbances in hours would damage the equipments. The power quality decreases due to growth of nonlinear loads in domestic appliances, such as home Uninterrupted Power Supplies (UPS), Induction stove, Television etc. Nowadays Domestic loads are controlled or powered with power electronic devices. The power electronic devices with Direct Current (DC) components generate high frequency signal for DC-Alternating Current (AC) conversion. The conversion introduces multiple frequencies in the AC power supply. The multiple frequencies in AC power supply are called as harmonics. The harmonics in AC supply affects the lifetime of home appliances, consumes more electric current, affects the power factor, transformer efficiency, and other electricity supply systems. Till now, to avoid harmonics, the filters are erected only in industrial loads or in the substations. In this paper a novel method to detect and control harmonics in domestic appliances is proposed. Harmonic control with various filters in the filter bank, based on detection of harmonic voltage let out from the domestic appliances for power saving. To select the appropriate filter to improve power quality, we apply a novel Genetic Algorithm based Linear Regression Method (GLRM) algorithm for optimum Filter Selection. From the results we were able to reduce the total harmonic distortion level to 3.68%.The current consumption of each household appliance is reduced considerably and finally the electricity bill is reduced to 15% and overall system efficiency improves to 85%.

Development of Remote Control System for Residential AC Power Supply Based on GSM Technology

The present study deals with the development of remote control system based on the Global System for Mobile Communication (GSM) technology for switching the low voltage AC power supply system at residential consumer. Function of this system is to disconnect and reconnect the electricity supply to consumers. The introduction of the GSM technology and particularly the use of hand-held mobile phones has brought the innovative distance communication to remote locations. This utilization of this technology for the remote control of systems and appliances will make life easier, safe and quick from anywhere. GSM module was used for receiving short message service (SMS) from user’s mobile phone that automatically enable the controller to take any further action such as to switch on and off the consumer load at the incoming power supply. The system was integrated with microcontroller and GSM network interface using assembly language. AVR Studio 4 software was utilized to accomplish the integration. The system is activated when user sends the SMS to GSM controller circuit at electric meter consumption panel board. Upon receiving the SMS command, the microcontroller unit then automatically controls the incoming power supply by switching on or off the device according to the user command. In other words, the developed system reads message from the mobile phone and responds to control the devices according to the received message. The system can also give feedback to the user to inform the status of switching operation if such command is received.

Development of Remote Operation System on Residential AC Power Supply Using Radio Frequency

This paper deals with the development of a remote operation system for residential AC power supply using medium radio frequency transmission. Application of this system is to disconnect and reconnect the electricity supply which is operated by power utility company. Radio frequency (RF) remote control consists of a transmitter and receiver, which is the main module of the developed system. The transmitter will send a control signal through the module equipment transmitting antenna and the signal will be received by the antenna radio frequency transceiver module. Then, the recipient will control the electrical signals through the contactor as an interface with all electrical equipment. The operation of this system is at a fixed frequency of 315 MHz and distance control of electrical equipment is up to 10m at open space and subject to any restriction, antenna and supply of power. The results of this system are successfully demonstrated in the prototype of the remote control system for residential AC power supply. Some modifications have been proposed to improve the function of remote control system.

Analysis on voltage oscillation of a mid-frequency series resonant inverter for DRMP coils on J-TEXT

This paper deals with the voltage oscillation of an AC power supply for generating dynamic magnetic perturbation (DRMP) on J-TEXT. The power supply is a series resonant inverter with a matching transformer. It was noted that the high-voltage oscillation at transformer primary side is caused by an interaction between the line inductance and the stray capacitance of the matching transformer at switching transitions. In order to reduce the high-voltage oscillation and consider the requirement for soft-switching technique simultaneously, the switching frequency should be chosen properly by fine-tuning. The dead time should be chosen according to the relative size of minimum required dead time for protection and the optimal dead time.

Study of Cold Atmospheric Plasma Jet at the End of Flexible Plastic Tube for Microbial Decontamination

Recently, cold atmospheric plasmas have demonstrated very promising antimicrobial activity in vitro and in vivo including selective destruction of tumor cells. However, the size and the rigidity of most plasma systems limit the clinical application for treatments in internal organs or regions with difficult access (e.g., mouth). Here, we report a device that allows ignition of cold He plasma jet at the tip of 1 m long, 3.5 mm diameter, flexible plastic tube. It is connected to a dielectric enclosure where dielectric barrier discharge (DBD) is generated by a low‐frequency AC power supply. A thin wire at floating potential put inside the plastic tube assists the formation of plasma jet at the downstream tube end. The flexible tube can be kept and manipulated by hand without electric shock and thus the plasma jet can be easily directed to a target. Variation of duty cycle of the applied voltage signal allows precise adjustment of the discharge power. The anti‐microbial efficiency of plasma jet system with flexible tube was tested against fungus Candida albicans seeded on agar.

Development of dielectric barrier discharging power supply

Due to the demand of a dielectric barrier discharge power supply, a high voltage and high frequency AC power supply was designed and implemented. Its output voltage is standard or approximate standard sine waveform with the frequency range of 1 kHz to 50 kHz. The output voltage and output frequency can be adjusted individually. The maximum output power of the power supply is 2 kW. It can be operated through local or remote control. The power supply has been used in the dielectric barrier discharging research under different conditions.

Highly insulating alumina films by a bipolar reactive MF sputtering process with special arc handling

Abstract Aluminum oxide (Al 2 O 3 ) thin films are used in microelectronics and sensor applications due to their good insulating properties. Usually, RF sputtering processes are used to produce insulating coatings for sensors, but this process has major drawbacks, mainly, a very low deposition rate which leads to higher production costs. AC reactive sputtering processes present higher deposition rates, but issues regarding arcing and creation of defects in the films need to be addressed. In this work, an AC power supply with a new concept for fast arc handling and limited current output was investigated. Alumina films were produced by means of a bipolar reactive sputtering process, using large area double rotatable cathodes. The process was very stable and arc counts are as low as 3–10 arcs/h in the best deposition conditions. High deposition rates were also observed, reaching 2–3 μm/h. The films obtained excellent insulating properties with breakdown voltages higher than 3 kV for films with thicknesses between 2 and 3 μm and a corresponding breakdown strength of 1.5 kV/μm (15 MV/cm).

DEVELOPMENT OF METHODS OF CALCULATION OF TRACTION POWER SUPPLY SYSTEMS AND ENERGY SYSTEMS FEEDING THEM

Currently, the cause deterioration of quality rating of electricity on tire traction substations AC can be either how mode of operation of power systems, industrial loads so and the impact of electric traction. The experience of energy surveys show that the loss from flow potential equalization currents in each the third plot between traction substations AC is amount to not less than 250 thousand kW∙h per year. To select the optimum power and places location of the device longitudinal capacitive of compensation and decision other tasks it is necessary methodology of systems of calculation that takes into account the complex nature of the mutual influence of the quality of the electricity coming from the energy system of and the transportation process. In the paper proposed three options for calculation algorithms modes work of existing and perspective systems, traction power supply AC jointly with power supply their by energy systems, including the algorithm for calculating networks of different nominal voltages using the transformations; decomposition and synthesis of networks with different voltage levels; the iterations and probabilistic assessment of the impact of power mains. Developed the schemes formalization of graphs and the matrices of portions of the outer and traction power supply and method of selecting parameters and places location of the devices longitudinal capacitive of compensation, which are based on direct methods solving systems of linear algebraic equations with a dense banded and profile-sparse the matrix. Are generalized ways of formation and transformation of graphs of schemes traction power supply and feeding them energy systems and proposed the method of calculation the complex the moment of schemes, which increases the accuracy of calculating of flows power on traction networks to 1-2 % and allows you to select the optimal parameters and places location of the devices longitudinal capacitive of compensation. Analysis of the results of modeling and real modes of traction network shows that the efficiency of use longitudinal capacitive compensation is high on traction substations for which the resistance external electric power supply system of the is greater than 0.5 ohms, and the degree of compensation is within the allowable K = 0.7.

Carbon dioxide dissociation to carbon monoxide by non-thermal plasma

The decomposition of carbon dioxide was investigated in a non-thermal plasma dielectric barrier discharge reactor filled with glass balls. The CO2 conversion was maximum by using a sinusoidal excitation compared to pulsed excitation. The CO2 conversion and the CO selectivity are increased in the presence of helium, particularly with the AC power supply, but with a decrease in energy efficiency. The formation of solid materials composed of carbon but also of silica was highlighted for the first time, proving that carbon was incorporated into the silica network along with CO2 dissociation under non-thermal plasma conditions. The temperature control of the reactor wall has shown that the CO selectivity is favored by a low temperature wall, whereas the CO2 conversion remained constant, suggesting that the carbon balance default is due to the CO decomposition on the reactor wall.

Study on Microstructure of the Matrix/Dense Inner Layer Interface in Micro-Arc Oxidizing on Magnesium Alloys

An extensive study was made of the boundary area microstructure between the matrix and dense inner sublayers of the ceramic coating formed on AZ91 magnesium alloy substrate by micro-arc oxidation(MAO).The coating was prepared in an alkaline electrolytic solution composed of 5-20g/l of NaH2PO4, 1-5g/l of NaOH, 5-8g/l of KF; 0.5-2g/l of Na3C6H5O7, and 0.5-2g/l of EDTA , employing a constant-current controlled AC power supply with a current density of 10-30A/dm2; and the microstructure of the coatings was characterized using transmission electron microscopy(TEM) and scanning electron microscopy(SEM). It was found that (1) the main constituent of the coating adjacent to the boundary was microcrystalline and nanocrystalline; (2) the microhardness of the coating adjacent to the boundary was improved than that of the matrix. It was due to the formation of the intermixing of Mg and MgO and their grains were refined, these leaded to fine-crystal strengthen.

Determination of 5-nitroimidazole residues in milk by capillary electrochromatography with packed C18 silica beds

This work presents a novel methodology for analysing 5-nitroimidazole residues in milk samples by capillary electrochromatography using lab-made packed columns, produced by carrying out a high pressure packing procedure using acetone as driving solvent and C18 silica uncapped particles (5µm particle size) as packing material. Column frits resulted from sintering the proper stationary phase by heating the packed material for 20s with a nichrome ribbon (80% Ni–20% Cr, 28cm×2mm×0.2mm, electric resistance 1.3Ω) connected to a 7V AC power supply. Lab-made C18 silica packed capillaries (40cmx50µm i.d.) were employed for the determination of 5-nitroimidazole drugs. Milk samples were treated by a salting-out assisted liquid–liquid extraction followed by a solid phase extraction with Oasis®HLB cartridges prior to their injection. Samples were hydrodynamically injected into the column for 120s at 11.5bar. Afterwards eight 5-nitroimidazole compounds were separated in isocratic mode under an applied voltage of 27kV and a temperature of 30°C. The selected mobile phase consisted of a mixture 60:40 acetonitrile:ammonium acetate (2.5mM, pH=5). Separation was monitored at 320nm and it was performed in less than 15min. The method was characterized in terms of linearity (R2≥0.993) and precision (repeatability, RSD≤12.2% and reproducibility, RSD≤14.5%), obtaining detection limits lower than 29µg/L for all compounds under study.

Proof-of-Concept of a Millisecond-Scale Electromagnetic Levitator Using High-Temperature Superconducting Coils

This paper proposes a millisecond-scale electromagnetic levitator using high-temperature superconducting (HTS) coils. The proposed apparatus consists of an AC power supply, short-circuit switches, an aluminum plate, and two HTS coils. The HTS coils are wound in opposite directions and electrically connected in parallel. Thus, in a symmetric current distribution, the magnetic fluxes generated by the two HTS coils ideally cancel each other. However, in a sudden asymmetric current distribution created by the short-circuit switches, the magnetic fluxes are not cancelled, and the effective magnetic flux induces an eddy current in the aluminum plate placed above the HTS coils. The magnetic flux generated by the eddy current in the aluminum plate and the effective magnetic flux generated by the HTS coils together generate the repulsive force to levitate the aluminum plate. In this paper, numerical calculations and experimental verification of the repulsive force are performed. We show that this apparatus is able to provide a levitation force that we expect will be helpful for devices that need fast switching behavior of the levitation force.

Role of ambient dielectric in propagation of Ar atmospheric pressure nonequilibrium plasma jets

A single-electrode atmospheric pressure nonequilibrium plasma jet surrounded with different ambient dielectrics is investigated driven by AC power supply. Another three ambient dielectrics, distilled water, ethanol, and carbon tetrachloride, are adopted to compare with air. By examining electrical and optical characteristics, it was found that the molecular polarity of ambient dielectrics had its significant effect on the propagation of atmospheric pressure nonequilibrium plasma jets. When the polarization of molecules was enhanced, the discharge current and the bullet velocity were also increased. For nonpolar dielectric of carbon tetrachloride, this was mainly resulted from the electron polarization in the built-in electric field. For polar dielectrics of ethanol and distilled water, in addition to the electron polarization, orientation polarization was the main cause for the further increase in discharge current and bullet velocity.

Subcooled flow boiling heat transfer of water in circular tubes with twisted-tape inserts under high heat fluxes

This paper presents the heat transfer of subcooled water in swirl flow under high heat fluxes with respect to the heat removal technologies for the divertors in the International Thermonuclear Experimental Reactor (ITER). The experiments were conducted in a vertical circular tube that was heated uniformly with a large AC power supply. A twisted tape with a twist ratio of 2 or 4 was inserted into the circular tube to induce the swirl flow. The test parameters were as follows: heat flux q=5–19.5MW/m2; system pressure P=3, 4.2, 5MPa; mass flux G=6000, 8000, 10,000kg/(m2s); and inlet bulk temperature Tb,i=50–200°C. The heat transfer coefficients and boiling curves are obtained from single-phase forced convection to fully developed nucleate boiling. The influences of mass flux, heat flux, system pressure, thermodynamic quality, and inlet subcooling on heat transfer are discussed in detail. Special attention is paid to the effect of the twisted tape on subcooled heat transfer. More importantly, a wide set of heat transfer correlations are evaluated on the basis of our experimental data, and relevant recommendations for engineering applications are made according to their prediction accuracies.