Continuous Operation Performance Research Articles

Energy and exergy analysis of a novel dual-source heat pump system with integrated phase change energy storage

In order to improve the application of renewable energy in cold regions and overcome the drawback of the low performance of traditional air source heat pumps (ASHP) in a low temperature environment, a novel type of dual-source heat pump system is proposed, which includes a heat pump, photovoltaic–thermal (PVT) modules, an air heat exchanger, and phase-change energy storage equipment. In response to different outdoor environmental parameters, the heat pump can use the PVT, ambient air, or solidification latent heat of water in the ice tank as the heat source. This study focuses on analyzing the applicability of this novel system in residential buildings. Firstly, the thermodynamic performance of the system under typical operating conditions is experimentally analyzed, proving that the system can effectively utilize solar energy under low solar irradiation. Then, the operational strategy of the system is optimized with the optimization goal of system exergy efficiency. Finally, the continuous operation performance of the system in winter is simulated and analyzed. The results show that the utilization ratio of solar energy reaches 2/3 in winter. Compared with the traditional ASHP system, the energy-saving rate of the novel system is 73.6 %, which can reduce the carbon emissions by 69 %. These results provide technical guidance for the application of the novel system in residential buildings in cold regions.

Enhanced salt removal performance using nickel hexacyanoferrate/carbon nanotubes as flow cathode in asymmetric flow electrode capacitive deionization

One of the most widely used CDI processes is flow electrode capacitive deionization (FCDI), which is preferred over conventional CDI with static electrode due to its continuous treatment of high-salt wastewater and ability to scale production. However, the discontinuous charge transport network in flow electrodes restricts the improvement of desalination performance. In this study, we prepared nickel hexacyanoferrate and carbon nanotubes composites (NiHCF@CNTs) by a simple ball-milling method and constructed an asymmetric FCDI (AFCDI) system using NiHCF@CNTs and AC as flow cathode and anode, respectively. Then the desalination performance of AFCDI was examined and compared with that of symmetric FCDI system using AC as both flow electrodes under different conditions. The stability was also investigated by a 20-cycle operation test. It was found that AFCDI system showed higher average salt removal rate and lower energy consumption compared with FCDI, owing to the enhancement of charge transport resulting from the couple of high specific capacitance of NiHCF and excellent electrical conductivity of CNTs. Moreover, AFCDI system has stable desalination performance in continuous operation. These results indicate that compositing Faradic materials and CNTs is an effective strategy for improving desalination performance of FCDI.

Performance‐based seismic classification of acceleration‐sensitive non‐structural elements

AbstractThis paper presents a general seismic classification procedure for acceleration‐sensitive non‐structural elements (NSEs) based on seismic qualification shake table testing and provides an application example for electrical cabinets in Italy. The proposed seismic classification procedure requires the definition of a set of required response spectra (RRS) for qualification shake table testing defined at different seismic hazard levels and the definition of a formal procedure to generate a test input motion. Each required response spectrum at a given seismic hazard level is then linked to different class levels and the requirements that an NSE should present to achieve each class level are defined. Using this framework, a seismic classification procedure for NSEs is developed for Italy, in which, the RRS are defined according to a peak floor spectral acceleration seismic hazard map of the territory so as to predefine regions in which an NSE belonging to a given class can be installed or not according to either a life safety performance objective or a continuous operation performance objective. Also, the limitations of the proposed seismic classification procedure are outlined. Finally, a nominal application example is presented in which four electrical cabinet specimens were tested on a shake table and their class levels were defined. The results of the application example are used to nominally show how the proposed classification procedure could be applied to discriminate between different types of the same NSE depending on the specific desired application.

Biomimetic fabrication of PET composite membranes with enhanced stability and demulsibility for emulsion separation

Membrane separation of highly emulsified oily wastewater is a critical requirement, but still challenging due to the poor demulsibility, unstable wettability, and low recyclability of oil/water separation membranes. Herein, inspired by beetles capturing water from the air, an inverse desert beetle-like membrane with excellent demulsibility and significant stability was fabricated using waste poly(ethylene terephthalate) (PET) bottles as building blocks for enhanced emulsion separation. Due to the unbalanced force formed by the surface energy gradient, the small tiny oil droplets of the oil-in-water emulsion can be captured by the superhydrophobic bumps (hierarchical Al2O3 clusters), thus strengthening the demulsification ability of the membrane. Interestingly, the membrane exhibits excellent emulsion separation efficiency (99.91%) and flux (2193.5 L m−2h−1) for surfactant-stabilized oil-in-water emulsions, as well as sustained and stable separation performance, which outperforms conventional single superhydrophilic PDA/PET membrane without superhydrophobic bumps structure. Moreover, a two-stages“growing-jumping” model for the water droplet discharge mechanism was revealed to depict the enhanced stable separation of APP3 membrane, avoiding sticky Wenzel states to destroy the superhydrophobicity of bumps. Thus, the as-designed membrane achieved stable emulsion separation performance in continuous operation, as well as good recyclability. This biomimetic membrane not only shows emergent application potential for emulsion separation, but also provides insights into designing advanced membrane-based separation technology.

Novel concept design of low energy hybrid battery thermal management system using PCM and multistage Tesla valve liquid cooling

To challenge the continuous operation performance of high energy density lithium-ion batteries at different ambient temperatures. A battery thermal management system combining Multi-stage tesla valve liquid cooling and Phase change material (MP) is proposed. After verification of the accuracy of the thermal model based on experimental measurements, numerical studies are performed at the end of 2C rate discharge. In addition, based on general full factorial design method, Kriging approximation model is used to construct complex nonlinear hybrid model between the spacing between batteries, the number of MSTV channels, coolant velocity and the performance of MP (pressure drop, standard deviation of surface temperature, and maximum temperature). At the same time, to avoid falling into local solutions, the adaptive simulated annealing (ASA) global search algorithm is integrated to optimize high-dimensionality multi-objective structural settings. The simulation results show that the designed MP-BTMS is connected with water/ethanol coolant and the inlet velocity is 0.193 m/s, the maximum temperature, standard deviation of surface temperature and pressure drop of the battery pack at 33.12 °C, 1.50 ℃ and 647.8 Pa, respectively. Finally, the optimised MP is used in continuous depth discharge conditions, as well as a range of simulation tests. The superiority of the optimum battery thermal management system in different application scenarios (liquid cooling/heating) is also verified. The cooling performance indicates that the use of MP reduces the total energy consumption required for coolant circulation by 79.9% compared to conventional BTMS. Moreover, it is found that at ambient temperature (Tamb = -10 °C), the use of MP can keep the battery module warm twice as long compared to conventional BTMS. This means that MP can significantly delay the temperature drop during cold stops of EVs, thus reducing the energy required for active battery heating after short-term parking.

Continuous Operation Performance of Bioreactor Based on Immobilized Petroleum Degrading Bacteria Beads

Continuous Operation Performance of Bioreactor Based on Immobilized Petroleum Degrading Bacteria Beads

Comparative Temperature Dependent Evaluation and Analysis of 1.2-kV SiC Power Diodes for Extreme Temperature Applications

Considering potential applications related to superconductivity and aerospace (typically less than 100 K), in this article, the temperature dependence of silicon carbide (SiC) power diodes is systematically characterized and analyzed over a wide temperature range of 90–478 K, especially focusing on cryogenic temperature. First, the static performance degradation mechanism of SiC diodes is established in an ultrawide temperature range, including forward/reverse I-V characteristics and junction capacitance ( Cj ) characteristics. Second, the reverse recovery characteristics are achieved, including peak reverse recovery current ( Irm ), reverse recovery charge ( Q rr), and switching energy ( E sw), clarifying a clearer internal relationship between reverse recovery and junction temperature. Meanwhile, the aforementioned critical parameters are further analyzed on an electrical scale with normal atmosphere temperature, including switching speed range of 62.3–2054.8 A/ μ s, load current range of 6–30 A, and dc voltage range of 400–1000 V. Third, based on newly proposed power loss analysis method, the continuous operation performance of SiC diodes is quantified and analyzed in actual cryogenic converters. The excellent temperature dependence indicates that SiC diodes have great superiority for extreme applications. Importantly, SiC mosfet 's body diode shows the great potential to operate as a freewheeling diode in the compact converter, especially at cryogenic temperature.

Antifoam, dilution and trace element addition as foaming control strategies in mesophilic anaerobic digestion of sugar beet pulp

The effectiveness of foaming control strategies, including trace element addition, feedstock dilution and use of antifoams, was assessed for the anaerobic digestion of sugar beet pulp (SBP) at laboratory scale under mesophilic conditions. Semi-continuous digestion at an organic loading rate (OLR) of 2 g VS L−1 day−1 resulted in methane yields of 0.316 L CH4 g−1 of volatile solids (VS), with a VS destruction rate of ~91%. At OLR of 3 g VS L−1 day−1 or above, foaming occurred, accompanied by small increases in alkalinity ratio and volatile fatty acid (VFA) concentrations and a slight fall in specific biogas and methane production, indicating a minor reduction in process stability and performance. At OLR 5 g VS L−1 day−1 foaming was persistent and severe. In contrast, digesters fed at OLR 5 g VS L−1 day−1 and supplemented with selected trace elements showed stable performance with no foaming. Dilution has proved an effective control strategy for other feedstocks, but feeding with diluted SBP (1:1 w/w) led to a decline in gas production and operational stability, with no significant benefits in eliminating foaming. Seven antifoams were tested for foam reduction and effects on batch digestion at a range of concentrations. Addition of certain antifoams at dosages of 0.5 mL L−1 or more could inhibit gas production. A selected antifoam agent was then trialled in semi-continuous digestion at OLR 5 g VS L−1 day−1. Repeated high antifoam dosing of 1 mL L−1 digestate was required to reduce foaming, and eventually proved inhibitory. More reliable screening tests are needed for antifoam selection, as batch toxicity testing may not provide a satisfactory guide to performance in continuous operation.

Improved virtual synchronous control for grid-connected VSCs under grid voltage unbalanced conditions

This paper presents an improved virtual synchronous control (VSynC) for the grid-connected voltage source converter (VSC) so as to continuously operate under the grid voltage with steady unbalance. The improved VSynC introduces the negative sequence power controls on basis of conventional VSynC. The improved VSynC is capable of regulating the negative sequence internal voltage to reduce the negative-sequence injected currents and oscillated powers of the VSC aroused by the negative-sequence grid voltage. Three alternative local control objectives for the VSC itself under steady state unbalanced grid conditions and their corresponding power references are deduced and computed. Simulated and experimental results are presented to validate the correctness and effectiveness of the proposed improved VSynC to enhance the continuous operation performance of VSynC-based VSCs during grid voltage steady-state unbalance.

Controlling thickener underflow rheology using a temperature responsive flocculant

Continuous solid–liquid separations with the temperature responsive flocculant poly (N‐isopropylacrylamide) (PNIPAM) were conducted in a pilot‐scale thickener for the first time, using fine quartz as the feed slurry. The performance in continuous operation was compared to batch sedimentation. The increase in sediment consolidation on cooling in batch sedimentation was less significant in the continuous operation due to kinetic limitations of the deeper sediment bed and shorter residence times in the pilot‐scale thickener. The reduction in underflow rheology which results when using the temperature responsive polymer as flocculant is significant. Paste‐like behavior results when underflow is discharged at 50°C, whereas low viscosity, near Newtonian behavior results when the underflow is discharged at 20°C. Compared to conventional polyacrylamide‐based flocculants, PNIPAM produces higher concentration underflow but lower clarity overflow and most importantly, significantly reduced underflow rheology (viscosity and yield stress). Temperature responsive flocculants have significant potential to reduce underflow pumping energy and cost for mineral tailings. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2940–2948, 2014

Three-component distillation using structured packings: Performance evaluation and model validation

This paper presents results of continuous feed and total reflux distillation experiments carried out with a common type and size structured packing using two- and three-component mixtures of common alcohols and water. With the binary mixture, the packing performed slightly better than with a three-component mixture. Surprisingly, the continuous operation performance appeared slightly better than in case of the total reflux operation. Delft model predictions of the overall mass transfer efficiency appeared to be conservative enough around the operating/design point load of the packing in question. The composition profiles measured with the three-component mixture were used to validate the rate-based (non-equilibrium) model developed at the Nagoya Institute of Technology, which appeared to be highly accurate, but also sensitive to the choice of the predictive method for the interfacial area.

Capillary pumping systems for solar heating application

Capillary pumping two-phase loops have been continuously investigated for electronic cooling systems, satellite thermal control and other space applications. Most tests were performed in capillary evaporators using plastic or metallic porous wick as capillary structure and anhydrous ammonia as the working fluid. In this work, capillary pumping system assisting flat solar collectors is proposed as an alternative to residential and commercial water heating systems, using fine circumferential grooves as capillary structure and acetone as the working fluid. The experimental results are obtained for a small-scale solar heating system, using one capillary pump attached to a flat copper plate of 46 cm in length and 6 cm in width. The capillary pump consists of a 19 mm OD and 500 mm long aluminium tube, with fine internal circumferential groves as the capillary structure. The working fluid is pumped from a condenser designed to delivery heat to the water storage. Heat inputs up to 14 W (507 W/m 2) were estimated for heating purpose. The system presented reliable start-ups and good performance in continuous operation. The measurements were found to be in good agreement with theoretical results for the temperature field and solar power absorbed by the system.

Enhancement of continuous operation performance of HVDC with self-commutated converter

This paper describes a converter control scheme to enhance continuous operation performance of HVDC system with voltage source type self commutated (SC) converter. The continuous operation of SC converter can be achieved by suppressing converter overcurrents and AC overvoltages in the case of AC line faults including phase failure. Development of a new control scheme has been accomplished by experiment using an AC/DC power system simulator in CRIEPI and the EMTP (Electro Magnetic Transients Program) analysis. At first, we show that converter overcurrents and AC overvoltages are caused by lack of control information to static limiter and insufficient control performance to negative-sequence current of SC converter. Next, an adequate converter control scheme is proposed which is composed of an ACR's (automatic current legulator) adjustable dynamic limiter to suppress the converter overcurrents, and the limit logic of SC converter to suppress AC overvoltages during phase failure.

Selective Transport of a Peptide from Its Mixture with an Amino Acid Using a Supported Liquid Membrane Process

Abstract Some experimental results on the separation of a peptide from a mixture of peptide and amino acid through a continuous supported liquid membrane process are described. As a model system a mixture of tryptophan (Trp, an amino acid) and tryptophan-leucine (Trp-Leu, a dipeptide) was chosen. The liquid membrane contained an anionic surfactant, sodium di-2-ethylhexyl sulfosuccinate (Aerosol OT/AOT), as a carrier dissolved in oleyl alcohol, as an organic solvent, supported on a commercial grade support (Celgard 2500). The liquid-liquid extraction experiments were carried out to study the influence of feed pH, feed and strip flow rates, and feed and carrier concentrations on the selective transport of Trp-Leu from its mixture with Trp. At pH 4–5 the transport rate of Trp-Leu was significantly higher than that of Trp. The increase in flow rate up to a value of 40 mL/h did not effect the selective removal of Trp-Leu. The flux rate increased with an increase of the carrier concentration up to 20% AOT, but the selectivity for Trp-Leu was highest at 10% AOT. An increase of Trp concentration up to 10-fold had little effect on the flux rate of Trp-Leu. The stability of SLM system in continuous removal of Trp-Leu from a single component system and from a binary mixture with Trp was studied. The effect of a competitive component did not alter significantly the flux rate and long-time performance in continuous operation. A procedure for regenerating SLM was examined, and the regenerated SLM performed as good as the freshly prepared one.

Theoretical Consideration and Recent Progress of Chemical Enrichment Process for Uranium Enrichment

Research and development for uranium enrichment by oxidation-reduction chromatography, begun in 1972 despite the prevailing view that a chemical process would require several centuries of operation to attain fuel-grade uranium enrichment and would thus be impractical, led to the establishment of basic process technology permitting attainment of 3% enrichment within several months of operation by the mid 1980, through advance which brought increased electron exchange and oxidation-reduction reaction rates, effective uranium adsorption band formation and maintenance, and equilibrium plate height reductions based on elucidation of mobile-phase dispersion. Theoretical descriptions of the enrichment factor and the isotopic abundance curve of the adsorption band were developed, and the theoretical and experimental development and verification of an intracolumn mechanism of redox agent self-regeneration led to a new “Super” process version characterized by greater simplicity and efficiency than previously thought possible. A pilot plant with enrichment columns of 1 m diameter and 3 m height, constructed at Hyuga City in Miyazaki Prefecture, demonstrated the recovery of 3% enriched uranium in April 1988. Subsequent development work has brought further advances in process economy and continuous-operation performance.