Thermal Gas Research Articles

Formation of secondary organic aerosols from Cl-initiated oxidation of anisole: Rapid release of ultrafine particles and organic chlorides

Recent studies have highlighted the increased occurrence of reactive chlorine, drawing significant attention to the process of chlorinated chemical oxidation of oxygenated aromatics emitted from biomass burning (BB) in the formation of secondary organic aerosols (SOA). This study selected an oxygenated aromatic, anisole, as a representative of BB, and investigated the products and mechanisms of its reaction with Cl•, as well as exploring the implications of precursor-to-oxidant ratio ([anisole/Cl2]0), NOx levels, and seed particles on SOA generation. The gas-phase composition, SOA composition, and particle information were determined using a single-photon ionization time-of-flight mass spectrometry (SPIMS), a thermal desorption unit gas chromatography mass spectrometry (TDU-GC/MS), and a scanning mobility particle sizer (SMPS), respectively. Experimental results indicate that within minutes of turning on the ultraviolet (UV) lights, a large quantity of ultrafine particles (UFPs) (diameter <100 nm) is immediately formed. The SOA yield is significantly dependent on [anisole/Cl2]0, decreasing from 66.2% to 20.0% as the [anisole/Cl2]0 increases. Upon oxidation by Cl•, anisole promptly released organic chlorides, including 2-chlorophenol and 2,4,6-trichlorophenol. The addition of NOx decreased the SOA yield, enhanced the role of OH• in the reaction process, and led to the formation of organic nitrogen products, such as C6H5NO3 and C7H7NO4. Furthermore, Cl• primarily initiates reactions through H-abstraction and Cl-substitution, resulting in the oxidation products largely retaining the benzene ring. This provides a potential explanation for the high SOA yield induced by Cl• in this study. Overall, our work suggests that the release of UFPs and organic chlorides can be found in the Cl-initiated oxidation of anisole, which contributes to high SOA yields. Against the backdrop of increasing wildfire frequency due to global warming, it is necessary to consider the contributions and sources of UFPs and organic chlorides caused by the reaction of wildfire emissions with Cl atoms.

VOC data-driven evaluation of vehicle cabin odor: from ANN to CNN-BiLSTM.

Emissions of volatile organic compounds (VOCs) in vehicles represent a significant problem, causing unpleasant odors. To mitigate VOCs and odors in vehicles, it is critical to choose interior parts with low odor and VOC emissions. However, prevailing odor evaluation methods are subjective, costly, and potentially harmful to the health of evaluators. In this study, we analyzed 139 automotive interior parts and 92 vehicles, establishing a cost-effective, data-driven method for odor evaluation. The contents of benzene, toluene, ethylbenzene, xylene, styrene, formaldehyde, acetaldehyde, acrolein, and total volatile organic compounds (TVOC) were detected by thermal desorption gas chromatography-mass spectrometry (TD-GC/MS) and high-performance liquid chromatography with an ultraviolet detector (HPLC-UV). Professional odor evaluators assessed the odors, identifying intensity levels from 2.0 to 4.5 in interior parts and 2.5 to 3.5 in whole vehicles. Leveraging this data, we applied four supervised learning algorithms to develop predictive models for the odor intensity of both interior parts and entire vehicles. During model training, we implemented early stopping techniques for the artificial neural network (ANN) and convolutional neural network-bidirectional long short-term memory (CNN-BiLSTM) models, while optimizing the support vector machine (SVM) and extreme gradient boosting (XGBoost) models using the GridSearch algorithm. The evaluation results reveal that the CNN-BiLSTM model performs the best, achieving an average accuracy of 89% for unknown samples within an odor intensity level of 0.5. The root mean square error (RMSE) is 0.24, and the mean absolute error (MAE) is 0.08. The model also underwent a sevenfold cross-validation, achieving an accuracy of 83.43%. Additionally, we employed SHapley Additive exPlanations (SHAP) for the interpretative analysis of the model, which confirmed the consistency of each VOC's odor contribution with human olfactory rules. By predicting odors based on VOCs through supervised learning, this study reduces the costs and enhances the efficiency and applicability of odor assessment across various vehicle interiors.

Identification of exhaled volatile organic compounds that characterize asthma phenotypes: A J-VOCSA study

BackgroundAsthma is characterized by phenotypes of different clinical, demographic, and pathological characteristics. Identifying the profile of exhaled volatile organic compounds (VOCs) in asthma phenotypes may facilitate establishing biomarkers and understanding asthma background pathogenesis. This study aimed to identify exhaled VOCs that characterize severe asthma phenotypes among patients with asthma. MethodsThis was a multicenter cross-sectional study of patients with severe asthma in Japan. Clinical data were obtained from medical records, and questionnaires were collected. Exhaled breath was sampled and subjected to thermal desorption gas chromatography-mass spectrometry (GC/MS). ResultsUsing the decision tree established in the previous nationwide asthma cohort study, 245 patients with asthma were divided into five phenotypes and subjected to exhaled VOC analysis with 50 healthy controls (HCs). GC/MS detected 243 VOCs in exhaled breath samples, and 142 frequently detected VOCs (50% of all samples) were used for statistical analyses. Cluster analysis assigning the groups with similar VOC profile patterns showed the highest similarities between phenotypes 3 and 4 (early-onset asthma phenotypes), followed by the similarities between phenotypes 1 and 2 (late-onset asthma phenotypes). Comparisons between phenotypes 1–5 and HC revealed 19 VOCs, in which only methanesulfonic anhydride showed p < 0.05 adjusted by false discovery rate (FDR). Comparison of these phenotypes yielded several VOCs showing different trends (p < 0.05); however, no VOCs showed p < 0.05 adjusted by FDR. ConclusionsExhaled VOC profiles may be useful for distinguishing asthma and asthma phenotypes; however, these findings need to be validated, and their pathological roles should be clarified.

Abell 746: A Highly Disturbed Cluster Undergoing Multiple Mergers

We present deep XMM-Newton, Karl G. Jansky Very Large Array, and upgraded Giant Metrewave Radio Telescope observations of Abell 746, a cluster that hosts a plethora of diffuse emission sources that provide evidence for the acceleration of relativistic particles. Our new XMM-Newton images reveal a complex morphology of the thermal gas with several substructures. We observe an asymmetric temperature distribution across the cluster: the southern regions exhibit higher temperatures, reaching ∼9 keV, while the northern regions have lower temperatures (≤4 keV), likely due to a complex merger. We find evidence of three surface brightness edges and one candidate edge, of which three are merger-driven shock fronts. Combining our new data with published LOw-Frequency ARray observations has unveiled the nature of diffuse sources in this system. The bright NW relic shows thin filaments and a high degree of polarization with aligned magnetic field vectors. We detect a density jump, aligned with the fainter relic to the north. To the south, we detect high-temperature regions, consistent with the shock-heated regions and a density jump coincident with the northern tip of the southern radio structure. Its integrated spectrum shows a high-frequency steepening. Lastly, we find that the cluster hosts large-scale radio halo emission. A comparison of the thermal and nonthermal emission reveals an anticorrelation between the bright radio and X-ray features at the center. Our findings suggest that Abell 746 is a complex system that involves multiple mergers.

Thermal structural damage and thermal decomposition characterization of GAP propellants with nitrate ester plasticizers

AbstractGAP and nitrate ester compounds are introduced into the solid propellant formulation as energetic binders and energetic plasticizing agents, respectively, to further enhance the energy level of solid propellants. However, under abnormal thermal conditions, various components within GAP propellants, especially nitrate ester plasticizers, can collectively result in the generation of a large number of voids within the propellant due to factors such as thermal stress and slow component decomposition. This phenomenon can impact the safety of solid rocket engines, necessitating research into their thermal decomposition processes and thermal damage structures. In this study, the thermal decomposition characteristics and gas products of GAP propellants with different nitrate ester plasticizer formulations were investigated using DSC‐TG and FT‐IR. The damage structure of GAP propellants heated under unignited conditions was studied through Micro‐CT, examining the influence of heating conditions and nitrate ester plasticizers on the thermal damage structure of GAP propellants. During heating, the thermal damage structure of GAP propellants was found to include voids generated within the GAP binder and cracks at the interface between the GAP binder and particles, with nitroglycerin as a plasticizer exacerbating the thermal damage of GAP propellants (about 2.2–2.9 times).

Energy big data abnormal cluster detection method based on redundant convolution codec

Due to the scattered distribution and poor clustering of abnormal clusters in energy big data, the ability to detect anomalies is poor. Therefore, a high-energy data anomaly clustering detection method based on redundant convolutional encoding is proposed. Quantitative analysis of the coupling characteristics of electrical thermal gas optical time series for multi energy users based on Copula function, and incorporating quantitative values into multi energy feature indicators to extract the energy consumption behavior characteristics of multi energy users. Utilize redundant convolutional codecs to recombine and structurally encode abnormal features of energy big data, and capture multi energy coupling time features using coupling time capsule layers. Then, coupling time features are synthesized through fully connected linear regression layers to generate anomalous clustering feature components, and the energy time series data is then transformed into feature values of the time series in three-dimensional space. Based on this, a comprehensive energy system and massive multi energy user energy big data anomaly clustering analysis are carried out to determine the optimal number of multi energy users. Then, based on linear layers, the electricity heat gas light load characteristic map of multi energy users is transformed into one-dimensional form, and an energy big data anomaly clustering detection model is constructed to complete anomaly detection. The simulation results show that the proposed method has excellent feature clustering performance, detection accuracy above 98.7%, fast convergence speed, and an error rate below 0.1, which has reliable application value.

Extending the flight endurance of stratospheric airships using regenerative fuel cells-assisted pressure maintenance

This study presents a comprehensive analysis of the design considerations and trade-offs involved in developing a stratospheric airship with in-flight gas replenishment based on regenerative fuel cells (RFC). To address the challenge of lift gas leakage and enhance flight endurance, the primary aim is to optimize energy acquisition, storage, and buoyancy maintenance. A solution utilizing RFCs to supply lift gas has been proposed, leveraging the combined utilization of hydrogen for energy and buoyancy maintenance. The flight endurance model considering thermal effects, energy system and gas leakage is established to provide insights into its potential for extending the flight endurance of stratospheric airships by 25.5 % based on the design of Stratobus. Scaling up the energy system provides surplus energy for hydrogen production; however, it may impact gas-tightness due to increased weight allocation. Various weight configurations were evaluated, demonstrating the significant impact of weight distribution on endurance. Without gas replenishment, the longest endurance was 60.4 days. With increased energy storage distribution and gas replenishment consideration, endurance improved to 87.2 days. Furthermore, a longer flight endurance extension to 118.2 days can be reached by applying a gasbag storage system. This underscores the importance of exploring innovative storage solutions to achieve longer endurance.

Pyrolysis and combustion of industrial hemp, coal and their blends for thermal analysis by thermogravimetric analysis/Fourier transform infrared spectrometer.

In this study, the thermal behaviours of Cannabis sativa (CS), coal and their five different blends at a heating rate (β) of 10, 20, 30, 40 and 50°C min-1; the synergistic effects between CS and coal; and the distribution of gases formed during pyrolysis and combustion were investigated by using the thermogravimetric analysis/Fourier transform infrared spectrometer (TGA/FTIR) integrated system. The TG and DTG curves showed that the thermal decomposition of pyrolysis and combustion of all feedstocks at all β values had three main decomposition stages. The synergistic effect was observed for DTGmax, mass loss (ML), or final residue (FR) at least once at a given β of each blend; and the synergy was more effective for DTGmax and ML in pyrolysis than in combustion, whereas the opposite was true for FR. The lowest emissions of CO2, CH4, NOx and SO2 except CO during pyrolysis occurred at the blend of 0% CS + 100% Coal. However, the highest emissions of CO, CH4, NOx and SO2 except CO2 during combustion were observed at the blend of 80% CS + 20% Coal. The emissions of CO, CO2, NOx and SO2 from all samples during pyrolysis were lower than that of combustion, indicating that pyrolysis can be preferred due to its lower emission to the environment. Different structural properties of CS, coal and their blends caused different thermal behaviours, synergistic effects and gas products during pyrolysis and combustion by TGA/FTIR, suggesting detailed further investigation for upper-scale pyrolysis and combustion applications.

Evolution law of pulsating seepage and thermal deformation by injecting high‐temperature steam into coal for thermal coalbed methane recovery

AbstractChinese coal reservoirs are characterized by low pressure and low permeability, which need to be enhanced so as to increase production. However, conventional methods for permeability enhancement can only increase the permeability in fractures, but not the ultra‐low permeability in coal matrices. Attempts to enhance such impermeable structures lead to rapid attenuation of gas production, especially in the late stage of gas extraction. Thermal stimulation by injecting high‐temperature steam is a promising method to increase gas production. The critical scientific challenges that still hinder its widespread application are related to the evolution law of permeability of high‐temperature steam in coal and the thermal deformation of coal. In this study, an experimental approach is developed to explore the high‐temperature steam seepage coupled with the thermal deformation in coal under triaxial stress. The tests were conducted using cylindrical coal specimens of ϕ50 mm × 100 mm. The permeability and thermal strain in coal were investigated when high‐temperature steam was injected at 151.11, 183.20, 213.65, and 239.76°C. The experimental results reveal for the first time that as the amount of injected fluid increases, the steam permeability shows periodic pulsation changes. This paper introduces and explains the main traits of this discovery that may shed more light on the seepage phenomenon. When the injected steam temperature increases, the amplitude of pulsating permeability decreases, whereas the frequency increases; meanwhile, the period becomes shorter, the pulsation peak appears earlier, and the stabilization time becomes longer. The average peak permeability shows a “U‐shaped” trend, decreasing first and then increasing as the steam temperature increases. Meanwhile, with the extension of steam injection time, the axial, radial, and volumetric strains of coal show a stage‐wise expansion characteristic at different temperatures of steam injection, except for the radial strains at 151.11°C. A two‐phase flow theory of gas–liquid is adopted to elucidate the mechanism of pulsating seepage of steam. Moreover, the influencing mechanism of inward and outward thermal expansion on the permeability of coal is interpreted. The results presented in this paper provide new insight into the feasibility of thermal gas recovery by steam injection.

Thermal rarefied gas flow simulations with moving boundaries based on discrete unified gas kinetic scheme and immersed boundary method

Rarefied gas flows in complex geometries with heat transfer and moving boundaries have received remarkable attention due to the prevailing of micro/nano science and engineering applications. This study presents an immersed boundary (IB)-based discrete unified gas kinetic scheme (DUGKS) for the simulation of complex moving boundary thermal rarefied flows. The fluid and temperature fields are solved according to the DUGKS with Shakhov collision model (SDUGKS), which is capable of modeling non-unit Prandtl number problems in all Knudsen regimes. The IB approach, featured by its superior performance to incorporate complicated boundary constraints on Cartesian grids, is applied here to handling the interaction between the micro gas and curved boundaries. Specifically, for the IB adopted in this study, we use the least square method for the reconstruction of the distribution functions near the boundary. The accuracy of the IB-SDUGKS is explored comprehensively in six benchmark problems, including the micro lid-driven cavity flow, thermal equilibrium gas in a circular domain, thermal transpiration in an enclosure, moving shuttle in a rarefied gas, movement of a piston with pressure differences and particle free motion in a lid-driven cavity. The present results agree well with the corresponding analytical and direct simulation Monte Carlo (DSMC) solutions, illustrating the versatility of the present IB-SDUGKS complex thermal rarefied flows.

Transient analysis of temperature field and fission gas about the arc plate fuel element

Obtaining the temperature field and fission gas release of fuel elements are crucial to the study on fuel behaviors and ensure the safety of elements. In order to enhance fuel efficiency, providing a design idea to make the fast reactor with high flux and multi-function, we have designed a core of the lead-based fast reactor with arc plate fuel elements. Based on above, a transient performance analysis program of arc plate fuel elements (TPAPAFE) was developed in this paper, for analyzing the thermal and fission gas module of arc plate fuel element by calculating transient variation in the maximum pellet temperature, internal and external coolant outlet temperature, and fission gas release share. The modular verification was done by comparing the results of TPAPAFE with others. Besides, the result of the arc plate fuel analyzed by TPAPAFE shows that the code is feasible and rational, and the single arc plate is so thin that coolant outlet temperatures on both sides of the plate are almost the same. Meanwhile, the error in temperature data between TPAPAFE and the steady-state program is only 5%. Furthermore, fission gas release fraction increased linearly with pellet temperature and bubble growth.

Development of a Thermal Separation Probe Gas Chromatography–Mass Spectrometry Method for Evaluating Wax–Resin Removal by Evolon® CR

Historically, many canvas paintings were infused with wax–resin mixtures that have discolored over time, distorting the aesthetics of the work, limiting treatment options, and introducing unstable materials into the object. Removal of the wax–resin is often desirable, but before works of art can be treated, a protocol to evaluate the efficacy of the treatment must be established. A mock-up painting was infused with a known amount of a wax–resin mixture made from beeswax and dammar; this material was then extracted through six intervals of exposure to solvent-loaded and dry sheets of Evolon® CR, a non-woven textile with a high sorbent capacity. Samples from the Evolon® CR sheets from each extraction round were analyzed using thermal separation probe gas chromatography–mass spectrometry (TSP-GC/MS). Normalization of peak areas related to beeswax and dammar to those of Evolon® CR revealed the relative amount of wax and resin removed throughout the extraction. The data show that, under these test conditions, the beeswax and dammar appear to be extracted with the same relative efficiency, information that cannot be provided through UV-induced visible fluorescence imaging of the Evolon® CR sheets or weight data alone, but which is critical to capture as it has implications for treatment success and the long-term stability of an artwork.

Effects of capacity on the thermal runaway and gas venting behaviors of large-format lithium iron phosphate batteries induced by overcharge

Large-capacity lithium iron phosphate (LFP) batteries are widely used in electric bicycles. However, while crucial, thermal runaway (TR) behaviors under overcharge conditions have rarely been studied, leading to frequent fire accidents. This paper investigates the overcharge behavior and TR characteristics of four LFP batteries with the same components and materials but varying capacities (86, 100, 120, and 140 Ah). Overcharge tests were conducted in a customized apparatus, and the surface temperature, mass loss, and gas venting phenomenon were recorded. The results revealed that under the same overcharge conditions, the TR early warning temperature can differ considerably with respect to battery capacity, highlighting the importance of selecting the appropriate early warning temperature in real-time temperature monitoring based on the capacity of the LFP battery. Three characteristic times were used to describe the thermal behavior of the batteries, namely, the time to reach the voltage plateau (tPV), the time when the safety valve opens (tSV), and the start time of TR (tTR). Analysis of critical heat accumulation indicated that the 86 Ah LFP battery has the lowest tolerance to overcharge and, thus, the highest TR risk. However, after TR, the 86 Ah LFP battery exhibited the smallest maximum temperature (Tmax), maximum temperature increase rate (Rmax), maximum total mass loss, and maximum mass loss rate (Mmax) among all the batteries, suggesting the least TR hazard. Consequently, a safety evaluation and scoring system using these six parameters was established considering the overcharge behavior and TR characteristics of LFP batteries. The results indicated that the TR risk ranking of LFP batteries with different capacities was 86 Ah LFP > 100 Ah LFP > 140 Ah LFP > 120 Ah LFP, while the TR hazard ranking was 140 Ah LFP > 120 Ah LFP > 100 Ah LFP > 86 Ah LFP. This comparative study of LFP batteries with varying capacities enhances our understanding of their overcharge behavior and TR characteristics, and a safety evaluation and scoring system can also be used for risk and hazard assessments of other types of batteries.

Experimental and mechanistic studies on the thermo-electric synergistic catalytic oxidation of acetone over MnO2/TiO2-Ni foam catalyst

Volatile organic compounds (VOCs) cause serious environmental and human health risks and must be efficiently removed. In this work, a metal-structured catalyst of Ni foam loaded Mn/Ti oxides was used for the oxidation of acetone, a typical VOC compound. The catalyst was in-situ joule heated when applying an electric current and produced the thermo-electric synergistic oxidation (TEO) effect. Compared with conventional thermal oxidation (CTO), the oxidation rate of acetone significantly increased by 124.19 % and the energy consumption of per unit complete oxidation rate was reduced by 66.67 % in TEO reaction with a 12 A electric current at 200 °C. The efficiency gradually improved (from 16.12 % to 36.14 %) and the energy consumption of per unit complete oxidation rate decreased (from 2.85 W/% to 0.95 W/%) with the increase of electric current. Besides, the thermal (including the catalyst thermal effect and reaction gas thermal effect) and electric effects in TEO reaction were analyzed by the statistical analysis method. With the temperature increasing from 200 °C to 400 °C, the proportion of electric effect slightly decreased while that of reaction gas thermal effect increased from 5.2 % to 18.1 %. It proved that the TEO method has the advantage of improving low-temperature catalytic activity. Furthermore, the mechanism of electric effect was investigated, in which it enhances the conversion of lattice oxygen in TiO2 to surface-adsorbed oxygen species and promotes the oxidation of Mn oxides, sequentially improving the oxidation of acetone.

Study on the effect of low-temperature cycling on the thermal and gas production behaviors of Ni0.8Co0.1Al0.1/graphite lithium-ion batteries

With their high energy density and long cycle life, lithium-ion batteries (LIBs) are currently the most promising electrochemical energy storage system for electric vehicles. However, their safety and cycling performance can be significantly compromised in low-temperature environments due to lithium plating and other factors. Therefore, it is essential to study the safety of aging batteries. In this study, we focused on a commercially available high-specific-energy Ni0.8Co0.1Al0.1 cathode system battery and simulated the aging of the battery by long-term cycling at 0 ℃. This study compares and analyzes the samples on the basis of the previous ones in terms of heat production power, thermal runaway (TR) characteristics and gas production characteristics. It reveals the influence of low-temperature aging on the comprehensive performance of lithium batteries in a more comprehensive way. The results show that the charging pattern of all three characteristics is related to the aging degree of the battery. In terms of the thermal characteristics, the relative change in specific heat capacity of the aged battery is only between 0.32 % and 1.08 % compared to that of a fresh battery, so the effect of ageing on the specific heat capacity of the battery is negligible. The average heat generation power of batteries with different state of health (SOH) is not monotonically increasing with the decrease of SOH, the threshold of dramatic increase is SOH = 80 %. In terms of TR characteristics, the onset temperature of exothermic reactions (TOER) of aged batteries is significantly lower than that of fresh batteries. With the decrease of SOH, TOER also decreases gradually. Compared with batteries with different SOHs, the more seriously aged the battery safety valve opens earlier, and the TR occurs earlier. In terms of the TR gas production characteristics, the more severely aged the battery, the earlier the safety valve opens compared to a fresh battery. The most gas is produced when SOH = 70 %, which increases the risk of catastrophic damage.

Adsorption behavior of CuO doped GeS monolayer on the thermal runaway gas evolution in lithium battery energy storage systems

Considering that the thermal runaway failure of lithium battery energy storage system will cause serious safety accidents, and lithium battery thermal runaway will precipitate various detectable gases through the safety gas valve. Effective monitoring of the precipitated gas can ensure the safe operation of the energy storage system. In this study, the adsorption behavior of CuO-GeS towards the main precipitated gases CO, CO2, CH4, and C2H4 in Lithium battery before thermal runaway is systematically studied based on DFT. The adsorption structure, DOS, DCD, and ELF are analyzed to explore the interactions between CuO-GeS monolayer and the gases. The results show that CuO-GeS monolayer achieves strong adsorption of CO and C2H4 and highly sensitive monitoring of CO2 and CH4. Furthermore, the relative molecular mass ratios of CxHy and CxHy-1F (x = 1, 2 y=2, 4, 6) gases to doped CuO can satisfy Smoothing Spline with adsorption energy and charge transfer, which can be used to estimate the adsorption properties of the homologous gases. The potential application of CuO-GeS monolayer in lithium battery energy storage systems lays a theoretical research foundation for the adsorption and detection of thermal runaway gas in lithium battery energy storage systems.

Multi-Energy Flow Integrated Energy System Considering Economic Efficiency Targets: Capacity Allocation and Scheduling Study

An integrated energy system (IES) breaks down barriers between different energy subsystems, enhancing energy reliability and efficiency. However, issues such as uneven equipment capacity allocation and suboptimal scheduling persist in multi-energy flow IES. To maximize economic benefits while ensuring energy balance and the operational characteristics of the equipment, a capacity matching optimization and scheduling strategy model for IES was developed. Firstly, mathematical models for the electricity, gas, and thermal networks within the IES were established. Secondly, considering the efficiency of energy conversion between different forms and constraints of energy storage in the electricity–thermal–gas interconnected energy system, optimization solutions were obtained using regional contraction algorithms and sequential quadratic programming methods. Finally, case studies conducted in a real park demonstrated that, through optimized capacity matching, unit prices for electricity, heat, and gas decreased by 39.9%, 90.5%, and 74.2%, respectively, effectively improving the economic viability of the system.

CRUD deposition induced multi-physics effects analysis in PWR

In PWR, the deposition of corrosion products from the steam generator leads to the formation of Chalk River Unidentified Deposits (CRUD) on the surface of fuel rods. CRUD deposition can cause issues such as CRUD induced localized corrosion, axial power anomaly and deterioration of cladding heat transfer. A new multi-physics program named CIFF (CRUD Induced eFFects analysis) is developed to analyze the effects caused by CRUD deposits. CIFF is a 1.5D model and can be used to simulate the variations in surface temperature, cladding corrosion and fuel deformation caused by CRUD deposition. A three-node CRUD deposition model is developed based on mass transfer theory and chemical equilibrium. The calculations of heat transfer, mechanical deformation, oxide layer growth, CRUD deposition and fission gas behavior are fully coupled based on finite element analysis and numerical solution technology. Axisymmetric element is used to solve the deformation of fuel rod under thermal expansion, gas pressure, creep and radiation swelling. The performance of CIFF is validated through IFA-513, ANO-2, Oconee and PCCL cases. The DBN-1 case is used to explore the influence of CRUD. The results indicate that CRUD deposition and CRUD induced local corrosion deteriorate the heat transfer of cladding, resulting in a three-stage increase of cladding temperature and accelerated growth of the oxide layer. CRUD deposition also leads to a relative increase in the gap pressure exceeding the coolant pressure by 8.4 %, a relative increase in the fuel rod strain by 10 % and a relative decrease in the gap size by 11 %, which indirectly leads a premature pellet-cladding mechanical interaction by 90 days.

Research on loss rules of oil and gas in preserved shale cores after open air exposure

There is a large amount of oil and gas loss in traditional conventional core samples. Revealing the rules of oil and gas loss is of great significance for restore the pristine oil content and oil component in the shale. In this study, four preserved shale cores with different thermal maturity (Ro = 1.01–1.53%) and different total organic carbon content (TOC = 1.69–5.48 wt.%) were selected. The samples are obtained from the first member of the Qingshankou Formation in the Gulong Sag. Nuclear magnetic resonance (NMR) T1–T2 mapping and thermal desorption gas chromatography (TD–GC, at a constant temperature of 300°C for 3 min) were performed on the preserved cores and their replicas that were exposed in open air for different times, to study dynamic loss process and the molecular composition changes of shale oil. The results show that during exposure, shale experiences a large amount of oil loss, with a loss ratio of about 42%–78%, and the higher the maturity, the greater the loss ratio. The oil loss is mainly contributed by free oil, with a loss ratio as high as 88%. The adsorbed oil content, however, remains basically unchanged and has a good positive correlation with the TOC of shale. Once the cores were crushed, the gaseous hydrocarbon in oil was basically evaporated in just 5 min. After long-term storage, 90% of the C14- light hydrocarbon is lost, while the C14+ heavy hydrocarbon experiences basically no loss. Therefore, effective and timely analysis of preserved shales is extremely important. The oil content of uncrushed shale cores characterized by NMR T1–T2 mapping is much greater than that of the crushed sample measured by TD-GC, which means that NMR T1–T2 mapping can be important method to evaluate the original fluid saturation of shale.

Effect of hydrogen blending on the accuracy of smart gas meters

The exploitation of green hydrogen blending with natural gas (NG) is expected to contribute in lowering greenhouse gas emissions and fostering the share of renewable energy sources (RES). The NG infrastructure, in fact, can act as a storage facility for green hydrogen produced from excess RES, also providing flexibility to the electric system. However, the unbalance of the networks and the raise of protection issues for consumers may occur as a consequence of the potential decay of the metrological performance of gas meters operating with natural gas and hydrogen blends. In this paper, the authors present the results of an experimental campaign aimed at analysing the effect of hydrogen blending on the accuracy of smart domestic gas meters. Experimental tests were performed in the laboratory using air, natural gas and gas-hydrogen blends up to 23%vol. The results show no criticalities occur for diaphragm and ultrasonic gas meters, regardless of the hydrogen content. On the other hand, thermal mass gas meters show good reliability when hydrogen blends are within 2%vol, whereas for higher hydrogen contents, reliability is demonstrated only when they are equipped with a specific new design routine capable to address the gas quality changes.