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Carbon dots (CDs) show great potential as a new type of oil-displacing agent for unconventional oil and gas development. However, the instability and easy aggregation epitomize the challenges that accompany the application of CDs in high temperature and high salinity (HT/HS) reservoirs. In this research, novel benzene sulfonate-modified carbon dots (BS-CDs) with remarkable thermal stability and salt resistance were fabricated through an in-situ electrochemical exfoliation method. Molecular simulation verifies that the introduction of benzene sulfonate groups substantially strengthens the electrostatic repulsion between BS-CDs, leading to outstanding dispersibility and stability even at a temperature of 100 °C and salinity of 14 × 10 4 mg/L. Core flooding tests show that 0.05 wt.% BS-CDs nanofluid can significantly reduce the water injection pressure by 50.00% and enhanced oil recovery (EOR) to 68.39% under HT/HS conditions. According to the atomic force microscopy (AFM) scanning results, the adhesion force between the core (after BS-CDs treatment) and oil decreased by 11.94 times, indicating that the hydrophilicity of the core surface was increased. In addition, the distribution of the adhesion force curve is more concentrated, which means that the micro-scale wettability of the core changes from oil-wet to more homogeneous water-wet. This study provides a feasible way for the development and application of good thermal stability and salt resistance CDs in unconventional reservoir development.

This paper addresses the urgent need to meet increasing energy demand while avoiding greenhouse gas emissions by improving energy efficiency. One significant challenge is the energy losses that occur during gas pressure reduction at city gates in natural gas distribution systems. To tackle this issue, this study proposes installing pressure reduction turbines (PRTs) parallel to existing reduction valves, which can generate electricity and enhance system efficiency. This research mainly focuses on Brazil’s natural gas supply, where the potential for installing PRTs is evaluated. The methodology analyzes the country’s distribution network and estimates the electricity generation capacity achievable from PRTs. The results indicate a potential power generation of 66 MW, capable of avoiding the emission of 235,800 tons of CO 2 annually and generating 333 GWh/year of electricity, all at a LCOE of $27/MW. These contribute to the environment using the energy efficiency achieved through the installation of PRTs, consequently, Brazil can help to a cleaner and more sustainable energy future.

In order to further regulate equivalent circulating density (ECD), a novel downhole apparatus for reducing circulating pressure in high-temperature and high-pressure wells, the suction-type ECD reduction tool, was devised. The utilisation of this tool enables the bottomhole pressure of the equivalent circulating density to be attained in close proximity to its hydrostatic pressure, thereby facilitating the attainment of deeper drilling depths. The tool is composed primarily of a screw motor, scroll blades, annular seals, universal joints, and drilling columns. The tool operates by utilising the suction effect and hydraulic energy extracted from the circulating fluid by the screw motor, which is then converted into mechanical energy to create suction and enhance the flow energy of the drilling fluid within the annulus at the bottom of the well, thereby reducing the equivalent circulating density. Furthermore, based on ANSYS-FLUENT analysis simulations, the alteration of pressure drop characteristics in response to varying drilling fluid densities, displacements, and tool sizes was modelled. The simulation results demonstrate that the pressure drop effect is 1.0 MPa when the drilling fluid density is 1.2 g/cm3, 1.7 MPa when the drilling fluid density is 1.5 g/cm3, and 1.9 MPa when the drilling fluid density is 1.8 g/cm3. A pressure drop of approximately 2.3 MPa was observed when the drilling fluid density was 2.0 g/cm3. The maximum pressure drop is achievable with a flow rate ranging from 1500 to 2500 L/min. A maximum pressure drop of 2.3 MPa is observed when the flow rate is within the range of 1500 to 2500 L/min. Two distinct viscosity values (0.02 and 0.06 kg/(m·s)) were employed to assess the impact of viscosity on pressure drop characteristics in a suction-type ECD tool. The results demonstrated that the pressure drop remained largely unaltered, indicating that viscosity had minimal influence on this parameter. The flow rate emerged as the primary factor affecting pressure drop, with viscosity exerting a relatively minor effect.

Nowadays, with increasing energy consumption, global warming, and many problems caused by weather conditions, the tendency to use novel methods of energy generation with high efficiency and low cost that reduce environmental pollution has increased. This study investigates the feasibility of using gas pressure energy recovery in natural gas pressure reduction stations by turboexpanders for cogeneration of power and refrigeration. Turboexpanders and compression refrigeration cycles are employed to recover the energy from natural gas pressure reduction stations. Then, natural gas along with the compressed air enters the Brayton power generation cycle and its waste heat is used in the carbon dioxide (CO2) power generation plant, multistage Rankine cycle, and multi-effect thermal desalination unit. This integrated structure generates 105.6 MW of power, 2.960 MW of refrigeration, and 34.73 kg s−1 of freshwater. The electrical efficiencies of the Rankine power generation cycle, CO2 power generation plant, and the whole integrated structure are 0.4101, 0.4120, and 0.4704, respectively. The exergy efficiency and irreversibility of the developed integrated structure are 60.59% and 68.17 MW, respectively. The exergy analysis of the integrated structure shows that the highest rates of exergy destruction are related to the combustion chamber (59.68%), heat exchangers (14.70%), and compressors (14.46%). The annualized cost of the system (ACS) is used to evaluate the developed hybrid system. The economic analysis of the integrated structure indicated the period of return, the prime cost of the product, and capital cost are 2.565 years, 0.0430 US $ kWh−1, and 372.3 MMUS$ , respectively. The results reveal that the period of return is highly sensitive to the electricity price, such that the period of return in the developed integrated structure is less than 5 years for the electricity price of 0.092 US $ kWh−1 and more. Also, the period of return is less than 5 years for the initial investment cost of 632.9 MMUS$and less, which is economically viable.

This paper investigates the effect of the inclusion of geofoam layers at the interface of wall and backfill on the dynamic response of mechanically stabilized earth (MSE) walls. In this aspect, 1-g model shaking table tests were conducted with sand–crumb rubber mixtures as backfill. The model wall of height 600 mm was used in the study. Tests were conducted by applying stepwise increasing peak ground acceleration (PGA) values varying from 0.063 to 0.59 g. The effect of different thicknesses of geofoam layers varying from 0.08 to 0.16H (H is the height of the wall) was investigated. The results revealed that the acceleration amplification in the backfill was reduced in the presence of sand–crumb rubber backfill compared to the sand backfill. The rubber–sand backfill showed a 38% increase in shear modulus and a 24.3% increase in damping ratio compared to sand backfill. The presence of deformable geofoam significantly reduced the lateral wall displacement and dynamic pressure on the wall. The wall displacement was found to be maximum at the top of the wall and reduced by 38% in the presence of the geofoam of 0.16H thickness. The pressure reduction determined in terms of pressure reduction efficiency (ηp) was found to be 61.3%. Further, the effect of the additional surcharge of magnitudes 5 and 10 kPa on the wall pressure was investigated. The pressure generated due to the surcharge loading on the wall was found to reduce with the increase in the geofoam thickness. Hence, it was concluded that installing geofoam layers marked a significant reduction in wall pressure with and without surcharge.

The primary objective of this paper is to identify the critical components of the acoustic field for a piston-type pressure reducing valve (PRV) with a high pressure reduction ratio, as well as to predict unfavorable noise both experimentally and numerically. The numerical calculations were conducted using a hybrid approach that combines computational fluid dynamics (CFD) and computational aeroacoustics (CAA). Flow-induced pressure fluctuation from unsteady turbulent flow extracted by the throttling cone, the valve body and the baffle in the low-pressure chamber were considered as individual dipole acoustic sources during calculation of the internal acoustic field. The results indicated that the selected three dipole acoustic sources always played a vital role in the response of the acoustic field, and none of them could be ignored. In comparison, the throttling cone had the most salient contribution to acoustic field distribution, the valve body took second place, and the baffle had the least salient contribution. The radiated noise of interest was predicted using the indirect boundary element method (IBEM), incorporating all three components as dipole acoustic sources simultaneously; the numerical noise values showed strong validation against the experimental data. Furthermore, the distribution of sound pressure levels, as well as directional and planar field points, is also presented. This paper provides new insights into the role of each component in flow-induced noise, and offers technical support for noise reduction design and optimization of pressure reducing valves.

Purpose To investigate the impact of surgical or medical reduction of intraocular pressure (IOP) on progressive normal-tension glaucoma followed up over 15 years. Methods Sixty eyes of 60 patients were divided into 3 intervention groups: group 1 (trabeculectomy, n  = 17); group 2 (IOP reduction rate ≥15% with prostaglandin analogs, n  = 24); and group 3 (IOP reduction rate <15% with prostaglandin analogs, n  = 19). The preintervention and postintervention mean deviation (MD) slopes and IOP were compared. Factors associated with the rate of visual field progression were identified by multiple regression analysis. Results The mean follow-up was 19.8 years. In group 1, the preintervention and postintervention IOPs were 14.7 ± 1.3 and 9.1 ± 2.0 mmHg, respectively ( P  < .001, 38% reduction). The MD slope decreased significantly after trabeculectomy (−0.86 ± 0.51 versus −0.19 ± 0.20 dB/y; P  < .001). In group 2, the preintervention and postintervention IOPs were 14.7 ± 1.5 and 11.7 ± 1.2 mmHg, respectively ( P  < 0.001, 20% reduction), with significant differences in the MD slope (−0.52 ± 0.37 versus −0.31 ± 0.30 dB/y; P  = .019). In group 3, the preintervention and postintervention IOPs were 14.4 ± 1.8 and 13.2 ± 1.6 mmHg, respectively ( P  < 0.001, 8% reduction), with no differences in the MD slope (−0.40 ± 0.27 versus −0.50 ± 0.65 dB/y; P  > .05). Multiple regression analysis showed that the average IOP, IOP reduction rate, and preintervention MD slope were related to the extent of the postintervention reduction in the MD slope. The difference in the preintervention and postintervention MD slopes significantly correlated with the rate of IOP reduction ( r  = 0.559, P  < .001). Conclusions A pressure-dependent maintenance effect of the visual field was confirmed in progressive normal-tension glaucoma.

Long-distance gas transfer requires high pressure, which has to be reduced before the gas is conveyed to the customers. This pressure reduction takes place at natural gas pressure reduction stations, where gas pressure is decreased by using gas flow energy for overcoming local resistance, represented by a throttling valve. This pressure energy can be reused, but it is difficult to implement it at small pressure reduction stations, as the values of unsteadiness significantly increase when the gas approaches consumers, whereas gas flow rate and pressure decrease. This work suggests replacing throttling valves at small pressure reduction stations for expander-generator units, based on volumetric expanders. Two implementations are proposed. A mathematical model of gas-dynamic processes, which take place in expander-generator units, was developed using math equations. With its help, a comparison was made of the stability of the operation of two possible control schemes in non-stationary conditions, and the feasibility of using an expander-generator regulator as a primary one for a small natural gas pressure reduction station was confirmed.

Abstract In the water supply system, for stable operation and management, pressure control, and energy consumption are important factors. However, gravity flow water supply systems can cause leaks and pipe damage when high pressure from upstream moves downstream. Therefore, the only popular way to control pressure within an acceptable range is to use a pressure reduction valve to control pressure within an appropriate range. However, using only the pressure reduction valve causes indiscriminate energy waste in operating and managing the water supply system. Accordingly, a micro-hydro turbine was proposed to replace the pressure reduction valve to provide appropriate pressure control and energy recovery. In addition, existing micro-hydro turbine designs were designed with only energy recovery in mind, but for sustainable operation, various design factors must be considered for optimal design. However, in design, EPANET2.2, the model simulation program in this study, does not have a model that can calculate the size of the turbine, so it is replaced with the pressure reduction valve and designed using the corresponding pressure and flow rate. Therefore, in this study, the range that satisfies the appropriate pressure condition is determined by using the pressure reduction valve (if a micro-hydro turbine is used with a surplus pressure head considering appropriate pressure control, the potential energy recovery amount can be determined). Therefore, a multi-objective optimal design technique was proposed that can optimize objective functions such as energy recovery and installation cost. The optimization technique is a multi-objective harmony search, and benchmark networks were applied to verify the proposed methodology. Through this study, it is expected that it can be effectively used in the sustainable operation of the water supply system by considering various design factors through adjustment of the set pressure. Graphical Abstract Graphical Abstract

Water loss is a phenomenon frequently observed within water distribution systems (WDSs), that is considerably worsened by an excessive pressure throughout the network. As an alternative option to pipe replacement, the use of pumps working as turbines, throttle control valves (TCVs), or pressure reduction valves (PRVs) can be used to reduce leakage. For a preassigned number of these devices, their positions and settings can be chosen to minimize the water losses in the network or to minimise the costs associated with the leakage. On the other hand, for a preassigned reduction in leakage, the number, the position and the setting of valves could be optimized in order to minimize their installation and maintenance costs. Based on these observations, a procedure for the optimal choice of the number, position and setting of PRVs is devised. The procedure is aimed at reducing the whole cost associated with water loss in urban WDSs, due to the background leakage from joints, and the purchase, installation and maintaining of the PRVs themselves. The effectiveness of the procedure, which is based on the physical modelling of leakage from pipe joints as well as on the use of a genetic algorithm, is proven using a small but realistic example.