Fracturing and thermal extraction optimization methods in enhanced geothermal systems

Fracture networks, fluid flow and heat extraction within fractures constitute pivotal aspects of enhanced geothermal system advancement. Conventional hydraulic fracturing in dry hot rock reservoirs typically requires high breakdown pressure and only produces a single major fracture morphology. Thus, it is imperative to explore better fracturing methods and consider more reasonable coupling mechanisms to improve the prediction efficiency. Cyclic fracturing using liquid nitrogen instead of water can generate more complex fracture networks and improve the fracturing performance. The simulation of fluid flow and heat transfer processes in the fracture network is crucial for an enhanced geothermal system, which requires a more comprehensive coupled thermo-hydro-mechanical-chemical model for matching, especially the characterization of coupling mechanism between the chemical and mechanical field. Based on the results of field engineering, laboratory experiments and numerical simulation, the optimum engineering scheme can be obtained by a multi-objective optimization and decision-making method. Furthermore, combining it with the deep-learning-based proxy model to achieve dynamic optimization with time is a meaningful future research direction.Document Type: PerspectiveCited as: Yang, R., Wang, Y., Song, G., Shi, Y. Fracturing and thermal extraction optimization methods in enhanced geothermal systems. Advances in Geo-Energy Research, 2023, 9(2): 136-140. https://doi.org/10.46690/ager.2023.08.0

4-(4-Chloro­phen­yl)-5-(4-nitro­phen­yl)-3-phenyl-4H-1,2,4-triazole

The title compound, C20H13ClN4O2, was synthesized by the condensation of 4-nitro­benzohydrazide and N-(4-chlorophen­yl)­benzimidoyl chloride in N,N-dimethyl­acetamide. The asymmetric unit contains two independent mol­ecules. In one molecule, the triazole ring is oriented at dihedral angles of 23.1 (5), 85.4 (1) and 10.5 (1)° with respect to the phenyl, chlorophenyl and nitrophenyl rings, respectively. In the other molecule, the corresponding dihedral angles are 29.8 (9), 73.4 (7) and 16.4 (3)°

BIM-based space management system for operation and maintenance phase in educational office buildings

Lists and floor plans have been widely adopted as space management tools for educational office buildings. However, the two-dimensional floor plans fail to present the indoor complexity, which hinders users from intuitively observing the indoor equipment arrangements and adapting to the indoor environment within a short time. Meanwhile, insufficient research has been conducted on space management tools regarding building indoor navigation. A Building Information Modeling Space Management (BIMSM) system was proposed in this study based on BIM. This system is comprised of two components, i.e. indoor space allocation management and indoor path navigation. The real-time space usage can be queried and user demands may be matched with available space by applying the Space Usage Analysis (SUA) theory. After the establishment of indoor maps, an improved A* algorithm is used to provide smooth navigation paths, and the visualization of such paths can be provided in mobile terminals. The BIMSM system was applied in an office building in a university in Shanghai, China. In this case study, the overall user satisfaction reached 91.6% by greatly reducing space arrangement failures. The time indoor navigation took outperformed that based on the traditional A* algorithm, with the search efficiency increasing 5.28%. First published online 17 December 201

Damage detection of pipeline multiple cracks using piezoceramic transducers

To study the feasibility of detecting pipeline multi-cracks damage using piezoceramic transducers, the electromechanical impedance method and the stress wave based active sensing method were used respectively to perform the damage detection of pipeline with multi-cracks. In this research, the lead zirconate titanate (PZT) type transducers were used due to its strong piezoelectric effect and low cost. During the experiments, two artificial cracks on the pipeline specimen were created, ranging from 0 mm to 9 mm, and seven different operating conditions were generated for each artificial crack. In the monitoring test, for the electromechanical impedance method, the damage index based on Root Mean Square Deviation (RMSD) was used, and for the active sensing method, the damage index based on Wavelet Packet Energy Loss (WPEL) was used. In addition, the relationship between the crack depth and RMSD as well as the relationship between the crack depth and location and WPEL were analyzed. The results show that RMSD and WPEL indices increase with the increase of the depth of pipeline cracks. In addition, the WPEL index increases with the appearance of new cracks. Quantitative analysis of pipeline crack damage can be realized by electromechanical impedance method, and localization analysis on the pipeline multi-cracks damage can be achieved by stress wave method based on sensor arrays

Changes in the Microbial Community Structure and Soil Chemical Properties of Vertisols Under Different Cropping Systems in Northern China

The predominant cropping system and management practices play an important role in soil physico-chemical properties and microbiome composition and diversity. This study analyzed the changes in soil fertility and the microbial community in four soybean-based cropping systems over 12 years. Amplification subsequencing techniques were used to compare soil community structures among the systems and identify significant positive and negative fertility factors. Soybean cropping favored the accumulation of OM and the available N, K DTPA Fe, Mn, Zn and Cu contents in soil but not fixed available P. The WS and CS cropping systems were conducive to the fixed available P, but they consumed OM, DTPA K, and Zn. The SC exhibited the lowest soil bacterial and archaeal abundance and diversity but high fungal abundance and diversity. The dominant Proteobacteria in the SC were significantly positively correlated with soil DTPA Fe and Mn. The dominant Actinobacteria were positively correlated with available P, DTPA Cu and Mn. The FS cropping system contained 764 unique bacterial species, 724 unique fungal species and the highest relative abundance of Protista. The FS had high microbial diversity, with high relative abundances of Bacteroidetes and Zygomycota and a significantly lower relative abundance of Actinobacteria. The Bacteroidetes were significantly correlated with available N, OM and DTPA Fe and negatively correlated with available P and DTPA Cu. Zygomycota was negatively correlated with available P and DTPA Cu. In the CS and WS, the soil bacterial abundance and diversity were moderate. The dominant Acidobacteria was significantly negatively correlated with soil DTPA, Fe and Mn. The CS exhibited the lowest fungal abundance and diversity. Furthermore, the relative abundance of Ascomycota was significantly improved in the WS and significantly positively correlated with available P and DTPA Cu. Decreases in the available P, K, DTPA Cu, and Mn of Vertisols greatly affect microbial community structure, and these nutrients regulate bacterial and fungal abundance and diversity. Compared to the SC, the FS, WS, and CS had more balanced soil fertility and microbial stability, but diverse cropping systems are most conducive to soil productivity. These findings are of great relevance for protecting the ecological environment

Thermal and Mechanical Analyses of Clamping Area on the Performance of Press-Pack IGBT in Series-Connection Stack Application

Press Pack Insulated Gate Bipolar Transistors (PP- IGBTs) are commonly connected in series and stacked together with heatsinks using an exterior clamping fixture in order to achieve high voltage dc-link levels. A suitable contact area between the clamping fixture and the device is essential to ensuring optimal PP IGBT thermo-mechanical performance, especially for the first and last devices in a stack. In this study, the effects of the clamping area on collector deformation, temperature, and stress distribution are investigated by means of the finite element method (FEM). Moreover, the paper analyzes the influence of heatsink thickness to maximize the stress evenness of the terminal PP IGBT and reduce the overall length of the stack system. The results indicate that the collector lid is prone to warpage due to thermal expansion, which results in a decrease in the effective contact area between component layers. As the contact resistance increases, the chips accumulate considerable heat. Increasing the clamping area at this point can adequately compensate for the warp deformation and can also improve the stress uniformity of the chips. Finally, an experiment making use of stress-sensitive film has been carried out to verify the developed FEM models