The stator structure is one of the main factors affecting the electromagnetic performance of permanent magnet (PM) motors. In this paper, an in-depth study and analysis of how to reduce the cogging torque is carried out from the perspective of the stator structure. According to the theory of cogging torque synthesis, this paper presents a unified calculation formula for different PM motor skewed notch designs. This theory is verified with a 20-pole, 60-slot motor and a 20-pole, 24-slot motor, respectively. The formula worked out proved to be highly applicable. The formula is intended to address how to quickly obtain key data (skew angle, notch depth) in a skewed notch study.

As part of the design process of a chiller plant, one of the final stages is the energy testing of the system in relation to future operating conditions. Recent studies have suggested establishing robust solutions, but a conservative approach still prevails at this stage. However, the results of some recent studies suggest the application of a new co-design (control−design) approach. The present research involves a comparative analysis between the use of conventional staging and the co-design approach in the design phase of a chiller plant. This paper analyzes the energy consumption estimations of six different chiller plant combinations for a Cuban hotel. For the conservative approach using on/off traditional staging, the results suggest that the best option would be the adoption of a chiller plant featuring a symmetrical configuration. However, the outcomes related to the co-design approach suggest that the best option would be an asymmetrical configuration. The energy savings result... [more]

The kick-off process is an important aspect of the proper operation of an agricultural biogas plant. At this stage, various operational problems may arise, mainly related to the stabilization of the fermentation process and reaching the full biogas production capacity. This paper presents the results of research on the kick-off of the fermentation process carried out on three selected biogas plants located in Poland. For the experiments, titration, potentiometric, and spectroscopic methods (ICP-MS) were used. The biogas plants during the kick-off period operated on the following substrates: a mixture of cattle and pig manure, corn silage, and whey liquor. Special attention was paid to the dosing process of the formulation developed by the authors (CMP-S1) containing Mo, Co, Ni, Se, and Mn for the fermentation chambers, to which the mixture of the selected microelements was not dosed. The study was carried out under real conditions on an engineering scale. The study showed that suppleme... [more]

Recent R&D activities in nuclear fusion have identified the DEMO reactor as the ITER successor, aiming at demonstrating the technical feasibility of fusion plants, along with their commercial exploitation. However, the pulsed operation of the machine causes an “unconventional” operation of the system, posing unique challenges to the functional feasibility of the steam generator, for which it is necessary to define and qualify a reference configuration for DEMO. In order to facilitate the transitions between different operational regimes, the Once Through Steam Generator (OTSG) is considered to be a suitable choice for the DEMO primary heat transfer systems, being characterized by lower thermal inertia with respect to the most common U-tube steam generators. In this framework, the ENEA has undertaken construction of the STEAM facility at Brasimone R.C., aiming at characterizing the behavior of the DEMO OTSG and related water coolant systems in steady-state and transient conditions. A de... [more]

Single-atom catalysts (SACs) within carbon matrix became one of the most promising alternatives to noble metal-based catalysts for oxygen reduction reaction (ORR). Although SACs have significant benefits in reducing the total catalyst cost, it also has the disadvantages of weak interaction between atoms and poor stability. Hence, there is still much room for improvement for the catalyst activity. In response, we designed a Fe-Co-Pt ternary metal single atom catalyst anchored on covalent organic framework (COF)-derived N-doped carbon nanospheres (Pt, Fe, Co/N-C). Due to effective charge transfer between Pt single atom and neighboring Fe-Co components, an intense electron interaction can be established within the Pt, Fe, Co/N-C catalyst. This is beneficial for enhancing charge transfer efficiency, modulating d electronic structure of Pt center and weakening oxygen intermediate adsorption, thus distinctly accelerating ORR catalytic kinetics. As expected, the half-wave potential of Pt, Fe,... [more]

The energy transition, originating in the limitation of fossil resources and greenhouse gas (GHG) emission reduction, is the basis of many studies on renewable energies in different industrial applications. The diffusion absorption refrigeration machines are very promising insofar as they allow the use of renewable resources (solar, geothermal, waste gas, etc.). This technology is often considered an alternative to vapor compression systems in cooling and refrigeration applications. This paper aims to overview the thermal mechanisms related to modeling system energy sources and highlight the primary methodologies and techniques used. We study and analyze the technology’s current challenges and future directions and, finally, identify the gaps in the existing models to pave the way for future research. The paper also gives a classification of absorption refrigeration systems (ARS) to position and limit the scope of the study. The paper will help researchers who approach the various aspe... [more]

SAGD (Steam Assisted Gravity Drainage) is used in Canadian fields where there are interlayers that impede steam chamber development and thus impede production. Many experiments have been conducted on the effect of interlayers on oil recovery. However, the swelling characteristics of interlayers under different conditions, as well as the possible clay mineral transformation and particle migration of clay particles at high temperatures, are rarely studied. In this paper, the swelling characteristics of natural oil sands and artificial clay samples were studied by high temperature hydration swelling experiments to obtain a better comparison. The effects of temperature, pressure and solution type on the swelling rate of oil sand were studied. The uniaxial compressive strength of the core in the presence of clay was studied by the scribe test. In addition, before and after the aging test at 220 °C and 2.5 MPa, the clay mineral composition was studied by the X-ray diffraction method, and the... [more]

This study proposed two concepts for ammonia fuel storage for an ammonia-fueled ammonia carrier and evaluated these concepts in terms of economics. The first concept was to use ammonia in the cargo tank as fuel and the second concept was to install an additional independent fuel tank in the vessel. When more fuel tanks were installed, there was no cargo loss. However, there were extra costs for fuel tanks. The target ship was an 84,000 m3 ammonia carrier (very large gas carrier, VLGC). It traveled from Kuwait to South Korea. The capacity of fuel tanks was 4170 m3, which is the required amount for the round trip. This study conducted an economic evaluation to compare the two proposed concepts. Profits were estimated based on sales and life cycle cost (LCC). Results showed that sales were USD 1223 million for the first concept and USD 1287 million for the second concept. Profits for the first and second concepts were USD 684.3 million and USD 739.5 million, respectively. The second conce... [more]

The use of the Maisotsenko cycle (M-Cycle) in traditional wet cooling towers (TWCTs) has the potential to reduce the costs of electricity generation by cooling water below the inlet air’s wet-bulb temperature. TWCTs cannot provide sufficient cooling capacity for the increasing demand for cooling energy in the power and industrial sectors—especially in hot and wet climates. Due to this fact, an experimental system of an M-Cycle cooling tower (MCT) with parallel counter-flow arrangement fills was constructed in order to provide perspective on the optimal length of dry channels (ldry), thermal performance under different conditions, and pressure drops of the MCT. Results showed that the optimal value of ldry was 2.4 m, and the maximum wet-bulb effectiveness was up to 180%. In addition, the impact of air velocity in wet channels on the pressure drops of the novel fills was also summarized. This study confirms the great potential of using the M-Cycle in TWCTs, and provides a guideline for t... [more]

In this paper, an experimental study was carried out on the rotating instability in an axial compressor subjected to inlet steady paired swirl distortion. In order to deepen the understanding of the rotating stall mechanism under inlet steady paired swirl distortion, the dynamic-wall static pressure near the rotor tip was monitored to characterize the flow in the rotor tip region at different circumferential stations. In the experiment, the dynamic characteristics of the rotor tip flow field at a stable operating point and during the process from the stable point to complete stall were measured. The results indicated that for the compressor with a 2 mm rotor tip clearance, the inlet paired swirl distortion induced rotating instability (RI) near the stall point, causing the compressor to enter stall in advance. Compared with the RI intensity of the clean inlet, the distortion with a swirling blade stagger angle (αs) of ±20° increased the RI intensity up to 69.8%, while for αs equal to ±... [more]

The aim of this case study is to implement the Lean Six Sigma methodology to reduce the scrap rate of the edge-bending process of a metal door case used in the assembly process of refrigeration appliances. This study was initiated because the assembly process of refrigerators does not work at maximum capacity due to the scrap that occurs for this component. Losses have direct effects on a company’s profits and on its competitiveness on the market. This research provides an overview of the identification of the most optimal and useful tools that can be used in each context; this will help to establish a protocol which can be applied in similar contexts. Although this study is limited to one process, the results will have direct effects on the assembly line of the organization. The purpose of this study is to increase the capability of the process and to improve the efficiency of the delivery of the component parts to the assembly line. This case study provides further evidence of the ef... [more]

The conventional V2O5 preparation processes include ion exchange, chemical precipitation, solvent extraction, and other processes. Given the long process and complex operation nature of traditional V2O5 production methods, we herein developed a short-process, low-temperature, and convenient operation method of isolating vanadium (in the form of V2O5) from shale acid leaching solution. The acid leaching solution was oxidized with NaClO3 and pH-adjusted with NaOH to form a vanadium-containing precipitate, which was mixed with AlCl3 (V:AlCl3 = 1:5, mol/mol) and roasted for 120 min at 170 °C to afford vanadium oxytrichloride (VOCl3) with a purity of 99.59%. In addition, the vanadium-containing precipitate was mixed with AlCl3 and NaCl (V:AlCl3:NaCl = 3:12:8, mol/mol/mol) and roasted for 120 min at 170 °C to afford VOCl3 with a purity of 99.94%. VOCl3 (purity of 99.94%) was dissolved in ultrapure water, and the solution (32 gvanadium/L) was treated with NH3·H2O (NH3:V = 1.34, mol/mol) at 50... [more]

The process of single-point incremental forming (SPIF) is a relatively new technology that is primarily used in the production of prototypes and small quantities of products. However, the process has several limitations with respect to the quality characteristics of its products. This study examined the effects of four process parameters—namely, tool diameter, feed rate, step size, and sheet thickness—on the characteristics of the final product. A total of 15 product responses were measured and/or calculated during the experiments. The responses fell under three different categories; surface profile accuracy, strain/stress/thinning, and forming forces. In previous published work, responses were studied separately for each category. The aim of this paper was to determine the relationships between responses using a principal component analysis (PCA). PCA is a well-known multivariate analysis technique used to reduce the dimensionality of data. As a result of the PCA, the product’s charac... [more]

High-frequency ultrasound (HFU) is an ultrasound technology with a frequency higher than 1000 kHz. It has become increasingly recognized as an emerging process intensification technology in various fields, such as biofuel production, carbon dioxide absorption, and wastewater treatment. HFU is seen as a potential intensifier technology for biofuel production, as its mechanisms, such as cavitational phenomena, microstreaming, and fountain formation, can benefit biofuel production. Previous research has shown that HFU can decrease the reaction time required for biofuel production, aid in lipid extraction, increase carbon dioxide absorption rates, and be effective in destroying pathogens in wastewater treatment. However, despite the potential benefits, there are limited reports on the use of HFU technology for biofuel production, which has led to uncertainties and constraints in its industrial deployment. These constraints include equipment design, economic analysis, and safety concerns, w... [more]

The core excitation saturation and vibration caused by DC bias are one of the important considerations in the design of high-frequency transformer (HFT). This paper studies the electromagnetic vibration characteristics of DC biased HFT with different winding structures. The vibration mechanism of iron core and winding under DC bias is analyzed. The optimal topology size of HFT is determined by area product (AP) method. In addition, the electromagnetic vibration multi-physical coupling model of a 500 V HFT under DC bias is established. At the same time, the electromagnetic vibration characteristics of interleaved winding and continuous winding of HFT are compared. The research shows that the current fluctuation of interleaved winding is smaller than that of continuous winding because of its ability to withstand impulse voltage. In addition, the average loss and maximum vibration displacement of HFT with entanglement winding are reduced in different degrees. The above research rules have... [more]

Bar splicing is considered an essential part of the construction process of reinforced concrete (RC) due to the ease of installation in construction, transportation constraints, and restricted length of reinforcing bars. Splices serve the primary role of joining reinforcement bars in standard RC elements such as columns, walls, beams, slabs, and joints. Bond behavior between the bars and the concrete is one of the fundamental qualities required for appropriate RC structure design and analysis, as it affects serviceability and ultimate limit states. The most common failure found in lap splice locations is debonding, which occurs at the splice region and insufficient lapped length is considered as the primary cause because of design or construction mistakes, design by outmoded code, and natural catastrophes. As a result, strengthening existing substandard splices in RC structures is critical. The purpose of this research is to analyze and summarize experimental strengthening solutions fo... [more]

The increasing demand for electricity in South Africa has led to a rise in the deployment of solar photovoltaic systems. The integration of these systems requires the installation of power transformers to convert the generated DC power into AC power that can be fed into the grid. However, the high cost of these transformers can hinder the widespread adoption of solar PV systems. Consequently, the primary objective of this work is to introduce a novel service-lifetime loss estimation method that acknowledges the unique requirements of transformers facilitating solar photovoltaic applications. In reality, these transformers are required to facilitate a sporadic energy source, which advocates for an appropriate method to assess the cost of their service-lifetime losses and total ownership cost. Thus far, the energy elements of classical coal-power generation are inadequate, and in conformity with operational and financial considerations of solar PVs, a novel method incorporating the outco... [more]

Realizing the large-scale development and utilization of siderite, a difficult iron ore reserve, has great practical significance in ensuring the supply of iron ore resources. Therefore, a new in-house conveyor bed magnetization roasting−dry cooling process was pilot-tested using low-grade siderite from the Daxigou iron ore mine. A two-stage weak magnetic separation method was used for a beneficiation test to investigate the influence of temperature and CO content on the magnetization of siderite. At 600 °C and 800 °C under suspension, iron minerals were converted into magnetite with an effective 3−5 s residence time. Furthermore, at 600 °C and 750 °C, increasing the calcination temperature increased the iron grade and the concentrate recovery rate. However, calcination at temperatures >750 °C resulted in a slight decrease in the iron grade and recovery rate of the concentrate. 61.50% Fe grade and 80.30% concentrate recovery rate were obtained under 750 °C from magnetization roasting.... [more]

Biological methanation of carbon dioxide using hydrogen makes it possible to improve the methane and energy content of biogas produced from sewage sludge and organic residuals and to reach the requirements for injection into the natural gas network. Biofilm reactors, so-called trickling bed reactors, offer a relatively simple, energy-efficient, and reliable technique for upgrading biogas via ex-situ methanation. A mesophilic lab-scale biofilm reactor was operated continuously for nine months to upgrade biogas from anaerobic sewage sludge digestion to a methane content >98%. To supply essential trace elements to the biomass, a stock solution was fed to the trickling liquid. Besides standard parameters and gas quality, concentrations of Na, K, Ca, Mg, Ni, and Fe were measured in the liquid and the biofilm using ICP-OES (inductively coupled plasma optical emission spectrometry) to examine the biofilms load-dependent uptake rate and to calculate quantities required for a stable operation.... [more]

Solar photovoltaic self-consumption is an attractive approach to increase autarky and reduce emissions in the building sector. However, a successful deployment in urban rooftops requires both accurate and low-computational-cost methods to estimate the self-consumption potential and economic feasibility, which is especially scarce in the literature on net billing schemes. In the first part of this study, a bottom-up GIS-based techno-economic model has helped compare the self-consumption potential with net metering and net billing in a Mediterranean municipality of Spain, with 3734 buildings in total. The capacity was optimized according to load profiles obtained from aggregated real measurements. Multiple load profile scenarios were assessed, revealing that the potential self-sufficiency of the municipality ranges between 21.9% and 42.5%. In the second part of the study, simplified regression-based models were developed to estimate the self-sufficiency, self-consumption, economic paybac... [more]

The energy group structure of a multi-group cross section library matched with a deterministic method has a significant influence on shielding calculation. The complex resonance cross section of Fe-56 has a significant influence on accuracy with different energy group structures when processing multi-group cross section data. In this study, in order to more accurately test the influence of the iron resonance phenomenon on shielding calculations, this group structure is modified by the 199-group with 69 points interpolated into its group boundaries at an energy range from 1.1 keV to 3.1164 MeV. The new 269-group library is then tested with selected SINBAD iron sphere benchmarks and compared with the results of 199-group, 299-group, and 172-group libraries and measurements. Upon analysis, it is shown that the resonance of Fe-56 has a great influence on the accuracy of the calculated leakage. Further, it is noted that the finer the energy group division, the greater the calculated leakage... [more]

This paper is related to light pollution and the energy efficiency of outdoor amenity lighting. It concerns the standard design assessment parameters of light pollution, the Upward Light Ratio (ULR) and Upward Flux Ratio (UFR), and the classic energy efficiency parameter—Normalized Power Density (NPD). The motivation for this research was the observation of certain inaccuracies related to the applicability and interpretation of these parameters in practice and the lack of connection between parameters of light pollution and energy efficiency. The multi-variant computer simulations of the exemplary large-area parking lot lighting system were conducted. Over four hundred cases were carefully analyzed. Individual cases differ in the shape of the task area, luminaire arrangements, mounting height, luminous intensity distribution, aiming, and maintenance factor. The results confirmed that the criteria values of ULR and UFR are often overestimated for modern luminaires, which emit luminous f... [more]

In this study, flow and heat transfer characteristics in novel non-closed 3/4 ring-shaped micro-pin-fin arrays with in-line and staggered layouts were investigated numerically. The flow distribution, wake structure, vorticity field and pressure drop were examined in detail, and convective heat transfer features were explored. Results show that vortex pairs appeared earlier in the ring-shaped micro-pin-fin array compared with the traditional circular devices. Pressure drop across the microchannel varied with layout of the fins, while little difference in pressure drop was observed between ring-shaped and circular fins of the same layouts, with the maximum difference being 1.43%. The staggered ring-shaped array was found to outperform the in-line array and the circular arrays in convective heat transfer. A maximum increase of 21.34% in heat transfer coefficient was observed in the ring-shaped micro-pin-fin array in comparison with the circular micro-pin-fin array. The overall thermal-hyd... [more]

To strike a better balance between gas quality and production cost of biomass-based syngas, a process for high-safety and cost-effective syngas production is designed and studied, which takes advantage of biomass O2-enriched air gasification with 40−70% O2 purity and methanation synthesis. Based on the simulation data, the process is evaluated from techno-economic aspects, including syngas composition, higher heat value (HHV), upper and lower explosive limits (UEL and LEL), toxicity, unit production cost (UPC) and levelized cost of energy (LCOE). Five kinds of biomass are studied as feedstock. The effects of O2 purity, methanation pressure, feedstock cost, and plant scale are determined, respectively. The results show that O2 purity is an important parameter for technical performance, while methanation pressure is a minor parameter except for exergy efficiency. With respect to cost indicators, feedstock cost, and plant scale are crucial variables; by contrast, O2 purity plays a relativ... [more]

The continual generation and discharge of waste are currently considered two of the main environmental problems worldwide. There are several waste management options that can be applied, though anaerobic digestion (AD) process technology seems to be one of the best, most reliable, and feasible technological options that have attracted remarkable attention due to its benefits, including the generation of renewable energy in the form of biogas and biomethane. There is a large amount of literature available on AD; however, with the continuous, progressive, and innovative technological development and implementation, as well as the inclusion of increasingly complex systems, it is necessary to update current knowledge on AD process technologies, process variables and their role on AD performance, and the kinetic models that are most commonly used to describe the process-reaction kinetics. This paper, therefore, reviewed the AD process technologies for treating or processing organic biomass... [more]