International Journal of Energy Research最新文献

Hydrogen refueling station (HRS) is an essential part of the infrastructure for promoting the hydrogen economy. Since hydrogen is a flammable and explosive gas, hydrogen released from high-pressure hydrogen storage equipment in HRS will likely cause combustion or explosion accidents. Studying high-pressure hydrogen leakage in HRS is a prerequisite for promoting hydrogen fuel cell vehicles and HRS. A computational fluid dynamics (CFD) model of an HRS in a demonstrated project in Ningbo, China, was established on the ANSYS FLUENT software platform. The CFD model for hydrogen leakage simulation was validated by comparing the simulation results with experimental data in the literature. The effects of the direction and mass flow rate of the hydrogen leakage jet, as well as the direction and speed of ambient wind, on hydrogen diffusion behavior were investigated. The spreading distances of the flammable hydrogen cloud were predicted using an artificial neural network for horizontal leakage. The results show that the jet direction strongly affected the flammable cloud flow. The greater the mass flow rate of the leak, the greater the hydrogen dispersion distance and the volume of the flammable hydrogen cloud. At a hydrogen leakage mass flow rate of 4.5589 kg/s, the volume of the hydrogen flammable cloud reached 6,140.46 m³ at 30 s of leakage. The ambient wind speed has complicated effects on spreading the flammable cloud. The wind makes the flammable cloud move in certain directions, and the higher wind speed accelerates the diffusion of the flammable gas in the air. The results of the study can be used as a reference for the study of high-pressure hydrogen leakage in HRS and will play an important role in the safe demonstration of the studied project.

Load forecasting plays a pivotal role in the efficient energy management of smart grid. However, the complex, intermittent, and nonlinear smart grids and the complexity of large dataset handling pose difficulty in accurately forecasting loads. The important issue is considering the cyclic features, which have not yet been adequately addressed through the trigonometric transformations. Furthermore, using long short-term memory (LSTM) or 1D convolution neural network (1D CNN) and existing hybrid models involve stacked CNN-LSTM architectures, employing 1D convolutions as a preprocessing step to downsample sequences and extract high- and low-level spatial features. However, these models often overlook temporal features, emphasizing higher-level features processed by the subsequent recurrent neural network layer. Therefore, this study considers a novel approach to independently process features for spatial and temporal characteristics using a parallel multichannel network comprising 1D CNN and bidirectional-LSTM (Bi-LSTM) models. The proposed model evaluated the National Transmission and Dispatch Company (NTDC) load dataset, with additional assessment on two datasets, American Electric Power and Commonwealth Edison, to ensure its generalizability. Performance evaluation on the NTDC dataset yields results of 3.4% mean absolute percentage error (MAPE), 513.95 mean absolute error (MAE), and 623.78 root mean square error (RMSE) for day-ahead forecasting, and 0.56% MAPE, 94.84 MAE, and 115.67 RMSE for hour-ahead load forecast. The experimental results demonstrate that the proposed model outperforms stacked CNN-LSTM models, particularly in forecasting hour- and day-ahead loads. Moreover, a comparative analysis with previous studies reveals superior performance in reducing the error gap between predicted and actual values.

In the case of multiple-failure accidents in light water reactors, it is imperative to demonstrate that a significant fuel damage can be prevented via prearranged mitigation measures performed by operators. However, the time elapsed from the initiation of the event to the implementation of mitigation actions significantly influences the progress and consequences of the accident. Therefore, assuming a specific time for operator mitigation actions does not provide sufficient insights for safety assessments, thereby calling for further investigations into the effect of the time delay from the prescribed value. In this study, the allowable operator action time for multiple-failure accidents of the Advanced Power Reactor 1400 was estimated by means of the sensitivity analysis using multi-dimensional analysis for reactor safety-KINS standard (MARS-KS), a best-estimate thermal–hydraulic analysis code used by the Korean nuclear regulatory authority. Three multiple-failure accidents were investigated, including small-break loss-of-coolant accident with the loss of safety injection (SI), intermediate-break loss-of-coolant accident with the loss of SI, and total loss of feedwater accident. The upper limit of the mitigation action time, which prevents core damage, was estimated based on the requirement for peak cladding temperature. This was in turn used to derive the tolerable delay from the assumed action time in the Korean accident management program for each multiple-failure accident.

The wake energy of an electromagnetic harvesting device is derived from the phenomena of wake-induced vibration (WIV). Experiments were conducted to determine the effects of the Reynolds number, the resistance of the circuit, and the distance between two concentric circular cylinders on the wake energy of the flow. The mechanism of the diaphragm energy harvester (DEH) consists of a single and tandem circular cylinders, which were examined separately. An elastic diaphragm with a magnet was also mounted in the wake of the cylinders. The Reynolds number varies between 2000 and 5000. The converter transforms the wake energy of the flow into electricity due to the vibration of the cylinder in a magnetic field. This research fills a critical gap in the literature by investigating the energy performance of a DEH under the wake-induced vibration of two fixed circular bluff bodies, demonstrating for the first time the feasibility of capturing vortex energy through the wake in the presence of a diaphragm. This unique approach distinguishes our work in the field of electromagnetic energy-harvesting devices, showcasing the potential for practical applications in renewable energy generation. The test results indicate that increasing the Reynolds number enhances the converter’s power output. Additionally, it has been observed that two critical distances are significant for the output voltage: the gap between the tandem cylinders (L^∗) and the distance between the edge of the diaphragm and the center of the cylinder (X^∗). The voltage output of tandem cylinders suggests that an optimal cylinder spacing falls within the range of 4 ≤ L^∗ < 5.

Interest in thermoelectric generators (TEGs) for waste heat recovery (WHR) and geothermal energy has grown significantly in recent years due to the ability to convert low-grade thermal energy into electricity, which is essential to reduce carbon emissions. One of the main challenges in TEG power generation is the expandability and the number of layers in TEG devices. The currently reported maximum number of layers is six. In this study, the expandable TEG devices with different number of layers, up to 20, were designed and manufactured. The field tests have been then conducted with these TEG devices using the waste heat from a coal bed methane power plant at a temperature of around 80°C. To our best knowledge, this is the lowest temperature at which TEG field tests have been implemented. At a flow rate of about 3 m³/hr, a TEG unit with a volume of about 3 m³ can generate a power of 15 kW at a temperature difference of 60°C. The power density and power per unit area of the TEG are investigated and compared to those of diesel generators and photovoltaic panels at different temperature differences. Furthermore, to offer guidance for the commercial-scale implementation of TEG, we have estimated the fabrication and installation costs, as well as the levelized cost of electricity, across various temperature differences. The results indicate that TEG is a feasible and promising technology for large-scale power generation and WHR.

Free convection heat transfer in hybrid nanofluids in a differentially heated wavy enclosure is studied. The wavy enclosure moves at a constant counterclockwise rotational speed along its longitudinal axis. The enclosure is filled with a hybrid nanofluids consisting of water (H₂O) and nanoencapsulated phase change materials (NEPCMs). These NEPCMs consist of a polyurethane coating and a core of N-nonadecane, which undergoes a phase transition and has the capacity to retain or emit a significant quantity of latent heat. The dimensionless forms of the governing equations have been solved using finite element method. The validity of the present code is demonstrated by comparing its predictions with published results. The governing parameters under consideration are the corrugated number, 0 ≤ N ≤ 3, the volume fraction of hybrid nanoparticles, 0.0 ≤ ϕ ≤ 0.05, the Taylor number, 8 × 10² ≤ Ta_H2O ≤ 2 × 10⁴. Changing the rotation speed is found to alter the melting and solidification zones in terms of pathways and size zones. The melting zone has a large size at moderate wave number, and its size shrinks and shifts downward as the wave number increases. An increase in the heat transfer rate values up to 38% is obtained when the concentration is adjusted from 1% to 5% for N = 1.

A hybrid material, LiNi_0.8Co_0.1Mn_0.1O₂, with excess lithium and wrapped in reduced graphene oxide (rGO), has been synthesized through ultrasonication employing Triton X as a surfactant. The ultrasonication process breaks down the initially clustered large particles into small nanoparticles, ensuring a uniform composite with reduced graphene oxide. With a consistent capacity retention of 87.56% over 100 cycles, the cathode composite exhibits a promising initial capacity of around 250 mAh g⁻¹ at 0.1 C. Notably, the composite has high-rate capability, providing capacities of 230 and 178.9 mAh g⁻¹ at 0.2 and 2 C, respectively. These experimental results indicate that the well-dispersed LiNi_0.8Co_0.1Mn_0.1O₂ nanoparticles and the porous reduced graphene oxide framework work in concert to enhance the electrochemical performance of the reduced graphene oxide-wrapped LiNi_0.8Co_0.1Mn_0.1O₂ cathode material, which was achieved through ultrasonication with Triton X (TX-100) surfactant assistance. This synergy allows for the fast diffusion of both Li ions (Li⁺) and electrons (e⁻) while also allowing volumetric variations during the introduction and withdrawal of Li ions (Li⁺). As a result, the fabrication of this reduced graphene oxide-wrapped LiNi_0.8Co_0.1Mn_0.1O₂ cathode material shows promise as a high-rate cathode material, especially for energy storage applications.

The ever-escalating CO₂ concentration in the atmosphere calls for accelerated development and deployment of carbon capture processes to reduce emissions. Mixed matrix membranes (MMMs), which are fabricated by incorporating the beneficial properties of highly selective inorganic fillers into a polymer matrix, have exhibited significant progress and the ability to enhance the performance of a membrane for gas separation. In this research, an amine-based ionic liquid (IL) [APTMS][AC] was prepared, which has greater CO₂ affinity and greater solubility due to its amine moiety. The metal–organic framework (MOF) UiO-66 with a multidimensional crystalline structure was used as a filler due to its appropriate porosity and tunable properties, and it was functionalized with NH₂. MOFs were further modified with an IL to prepare UiO-66@IL and UiO-66-NH₂@IL, and MMMs incorporating each MOF were fabricated with the polymer Pebax-1657. All the prepared membranes and MOFs were characterized to predict their separation efficiency. Several characterization techniques, namely, FTIR spectroscopy, XRD, and SEM, were used to successfully synthesize UiO-66@IL and UiO-66-NH₂@IL composites and confirmed proper dispersion and excellent polymer‒filler compatibility at filler loadings ranging from 0 to 30 wt.%. The separation performances were investigated, and the results showed that the incorporation of RTIL with the highly crystalline structure and large surface area of UiO-66 enhanced the separation efficiency of the membrane. The permeability of CO₂ for all fabricated membranes continuously increased with increasing filler concentration, wherein the permeability was comparatively high for the UiO-66-NH₂ MMMs. The CO₂/CH₄ selectivity improved by 35%, 54%, and 60%, respectively, for UiO-66@IL, UiO-66-NH₂, and UiO-66-NH₂@IL MMMs compared to simple UiO-66 for CO₂/CH₄ and by 28%, 36%, and 63%, respectively, for CO₂/N₂, with an increase in filler loading in the MMMs.

This study explored the heat transfer performance of a decaying swirl flow generated by a four-lobed swirl generator with simulations and experiments. In the experimental studies, the thermal performance of a swirl generator was compared with that of a circular tube, indicating that the printed swirl generator provided better heat transfer performance than the printed circular tube. Further experiments were performed over a range of Reynolds numbers with different lengths of post-swirl, circular pipe to assess the decay of swirl, downstream. Here, for shorter lengths of post-swirl, circular pipe, the thermal improvement was maintained, but this advantage was lost with longer circular pipe runs. In numerical studies, the effect of various pitch-to-diameter (PD) ratios of the swirl pipe, including the actual swirl pipe (in-swirl) as a part of the heat exchanger or excluding it (ex-swirl), and the effect of different post-swirl section lengths were investigated. The heat transfer rate and pressure drop increased with the reduction of the PD ratio, and the in-swirl arrangements gave higher thermal enhancement and similar pressure loss compared with the ex-swirl arrangements. The PD6 in-swirl arrangement gave the highest thermal enhancement for all the geometries. Applying the swirl intensity and the field synergy principle confirmed these results, showing that any thermal enhancement created by swirl generators disappeared rapidly after exiting the swirl tube. In addition, the field synergy principle was more suited to explain the thermal enhancement effect of the decaying swirl flow instead of swirl intensity. This study demonstrates that by optimising the post-swirl pipe length, overall heat transfer performance can be increased by around 5% with a pressure drop of less than 16%.

Nuclear accidents, such as the Fukushima nuclear accident, have highlighted the necessity for accident-tolerant fuel (ATF) cladding. Previous studies focused on coating the outside of Zr alloy currently used in nuclear reactors with an oxidation-resistant material in a vacuum environment. This limits the coating to the inside of the cladding and does not tend to achieve a uniform coating on meter scale cladding. In this study, a room temperature and non-vacuum-based swaging–drawing process was demonstrated as an alternative cladding manufacturing process. It enables both the inner and outer sides of the 2-m-long Zr alloy cladding to be uniformly covered with a 100-μm-thick corrosion-resistant material (316-L stainless steel; SS316L), thereby minimizing its high-temperature oxidation and avoiding failures. After the swaging–drawing process, there was a gap of less than 1 µm between outer SS316L and Zr alloy and a gap of about 12 µm between inner Zr alloy and SS316L. The high-temperature oxidation properties of the resulting triplex Gachon ATF cladding tube (G-tube) were evaluated up to 1,200°C in an atmospheric environment. Following heat treatment at 1,200°C, the control cladding completely oxidized and ruptured, potentially causing leakage of radioactive material during application. In contrast, only 15% of the G-tube cladding manufactured by the swaging–drawing process was oxidized despite a gap, and the Zr alloy of the G-tube changed phase from α-Zr to α-Zr (O) and prior β-Zr. The cladding microstructure, oxide layer, and oxidation mechanism were analyzed through microscopy, X-ray diffraction, and thermogravimetric analysis. As a result, it was confirmed that SS316L completely prevented oxygen diffusion into the bulk Zr alloy. In addition, there was no elemental diffusion between SS316L and the Zr alloy. These results demonstrate the feasibility of using room temperature, nonvacuum environment-based swaging–drawing process to fabricate structurally stable ATF cladding at extremely high temperatures.