Flow Supply Research Articles

Holistic non-linear optimization of the layout, sizing, and operation of a district heating plant

A large fraction of district heating networks in Europe are still operating without thermal energy storage. While offering operational flexibility, the presence of energy storage complicates the problems of optimal sizing and control of the heat production plant. This necessitates a novel approach to system sizing based on non-linear programming in order to capture the system’s thermal response and inertia. Therefore, the present study focuses on such a typical plant in France and describes a holistic approach to optimize the capacities/parameters of system components, positions of the energy sources, as well as hourly flow rates. Such a simultaneous tuning of the system parameters and operating variables is essential to maximize the cost savings over the system's lifetime. The proposed framework here maintains the original non-linear form of the objective function and the constraints for more accuracy while allowing precise modeling of the thermally stratified storage tank by decoupling its calculations at a lower simulation level. Hence, the computation time in MATLAB® R2020A is mostly below 20 min on a typical personal computer. The lowest levelized cost of heat (57.259 EUR/MWh) is achieved when placing the gas boiler on a parallel line between the biomass boiler and the storage tank while sizing the two boilers using fractions of 0.33 and 0.73 of the maximum hourly demand, respectively, as well as a storage volume of 318.9 m3. Such relatively small storage reduces the lifecycle costs by a maximum of 1.34 % while reducing the specific carbon emissions by 17.33 %. Besides, it dampens the fluctuations in supply flow rates, minimizes unnecessary flow recirculation, and ensures a stable heat supply. Overall, thermal storage has a reasonable positive impact from an economic perspective, but a substantial impact on operational flexibility and mitigated carbon emissions.

Quantitative Models for Supply Chain Risk Analysis in Water Tank Manufacturing: A Case Study of a Factory in Aba, Nigeria

Quantitative models for supply chain risk analysis of water tank manufacturing company factory Aba, Abia state has been studied. Aba being one of the biggest cities known for commercial activities in southern part of Nigeria, couple the weight of weight and area of a water tank, has made the supply mechanism of the product costly. This study delves into the complexities of supply chain management, aiming to identify risk assessment models, vulnerabilities, propose optimal scenarios, and recommend enhanced risk management strategies. Risk factors identification, route time estimation, critical path analysis, cost-related risk assessment, comparison of logistic choices, and decision tree and mitigation were used to instigate and determine the best path for the supply flow of the system and save cost. From the results obtained, the analysis reveals that PATH 6 is the most time-efficient route, with the critical path identified as 62 hours, furthermore, two transportation/logistic choices were compared, with the second choice considered more cost-effective (N6.6m) than the first (N6.9m), the developed decision tree model, explores vulnerabilities in the supply chain and proposes mitigation strategies. This research has suggested some applicable guides to optimize supply chain managements, which includes partnering with distributors, leasing warehouses, or collaborating with retailers, with each decision weighed against various factors and costs to align with the company's best interests. The study underscores the importance of considering every component of the supply chain during decision-making to effectively mitigate risks.

Hypoxic-ischaemic encephalopathy based on clinical signs and symptoms and associated factors among neonates, Southern Ethiopian public hospitals: a case-control study.

Hypoxic-ischaemic encephalopathy (HIE) is a severe condition that results from reduced oxygen supply and blood flow to the brain, leading to brain injury and potential long-term neurodevelopmental impairments. This study aimed to identify the maternal and neonatal factors associated with hypoxic-ischaemic encephalopathy among Neonates. The authors conducted a case-control study in 15 public hospitals with 515 neonates and mothers (175 cases and 340 controls). The authors used a questionnaire and clinical records created and managed by Kobo software to collect data. The authors diagnosed hypoxic-ischaemic encephalopathy (HIE) by clinical signs and symptoms. The authors used logistic regression to identify HIE factors. Hypoxic-ischaemic encephalopathy (HIE) was associated with maternal education, ultrasound checkup, gestational age, delivery mode, and labour duration. Illiterate mothers [adjusted odds ratio (AOR)= 1.913, 95% CI: 1.177, 3.109], no ultrasound checkup (AOR= 1.859, 95% CI: 1.073, 3.221), preterm (AOR= 4.467, 95% CI: 1.993, 10.012) or post-term birth (AOR= 2.903, 95% CI: 1.325, 2.903), caesarean section (AOR= 7.569, 95% CI: 4.169, 13.741), and prolonged labour (AOR= 3.591, 95% CI: 2.067, 6.238) increased the incidence of HIE. This study reveals the factors for hypoxic-ischaemic encephalopathy among neonates in Ethiopia. The authors found that neonates born to illiterate women, those who experienced prolonged labour, those whose mothers did not have ultrasound checkups during pregnancy, those delivered by caesarean section, and those born preterm, or post-term were more likely to develop hypoxic-ischaemic encephalopathy. These findings indicate that enhancing maternal education and healthcare services during pregnancy and delivery may positively reduce hypoxic-ischaemic encephalopathy among neonates.

Impacts of EU Regulation on Green Hydrogen Production and Storage Capacity Design and Operation

In European Union green hydrogen production is regulated to guarantee that transition to green energy will really have positive effect on the mitigation of the climate change, and that the integration of hydrogen economy to existing energy system will be as smooth as possible. However, these regulations complicate the optimal design and operation of the hydrogen production. Requirement about one-hour temporal correlation between contracted variable renewable electricity production and green hydrogen production forces to invest in overcapacity of electrolyzers and high-capacity hydrogen storages to buffer variable hydrogen production to smooth supply flow to hydrogen end use processes. This paper explains these issues with a demonstrative example how different design parameters result to the operation performance of the hydrogen production process.

Survey of Pangolin Availability and Trade in Selected States of Southern, Nigeria

Purpose: The Study ascertain Pangolin availability and trade in five selected states of Nigeria. 
 Materials and Methods: Purposive sampling was use to select their involvement in wildlife trade especially Pangolins. Questionnaire was administered as interview guide to seventeen accessible marketers of wild animals and data were subjected to descriptive statistics and measure of central tendency.
 Findings: All marketers were married women, between ages 35-54 years, 47.2% had 1-10years business experience with 17.6% having 31-40 years business experience, 94% of respondents confirmed reduction in population of pangolin from the flow of supply through hunters, twelve dollars fourteen cents was the price depending on the size, Phataginus tricuspis was mostly traded and 21 species of wildlife were traded by these marketers.
 Implications to Theory, Practice and Policy: A proactive step should be taken by relevant stakeholders to reduce trade in pangolin, through stringent legislation, intensive conservation education, provision of alternative sources of livelihood to both the hunters and marketers in the study areas.

SUPPLY FLOW OPTIMIZATION IN THE PROCESS OF ACQUISITION OF WORK UNIFORMS: A CASE STUDY IN A NETWORK OF DEPARTMENT STORES IN JOINVILLE

With the growing need to serve customers with greater quality, seeking competitive advantages, it is essential that service employees remain properly uniformed. For this need to be met, the company must deliver these uniforms, maintaining a coherent and well-defined process flow in the logistics of this material. This article aims to optimize the supply flow in the process of acquiring work uniforms in a chain of department stores in Joinville through lean thinking. To meet this objective, it was necessary to analyze the current process flow and apply purchasing management, inventory management and process management tools. These applications resulted in the elimination of waste, increased process quality and a linear flow, without bifurcations, looping’s and low complexity.

Sustainable supply chain resilience for logistics problems: Empirical validation using robust and computational intelligence methods

A supply chain's ability to avoid an unexpected disruption or quickly return to a normal situation defines supply chain resilience. Prior works have emphasized the integration of supply chain resilience and sustainable development goals (sustainable supply chain resilience), which is the focus of this paper. This paper proposes a four-level supply chain consisting of suppliers, intermodal hubs, manufacturers, and distributors along with a heterogeneous fleet of vehicles. Two types of manufacturers are included: large and small. The small manufacturers are moveable. To contribute to sustainable logistics problems, the objectives are cost, carbon emissions, and job opportunities when the appropriate supply chain members and flow of materials are optimized. To contribute to supply chain resilience, this paper presents a new robust approach and a new multiobjective algorithm to capture uncertain parameters (e.g., supply cost and employee availability). A numerical example based on empirical data shows the applicability of the proposed model.

Research on a Pressure Control Method for a Liquid Supply System Based on Online Updating of a Radial Basis Function Neural Network

In order to solve the problem of frequent pressure fluctuations caused by fluid quantity variation in hydraulic support liquid supply systems and the pressure response lag caused by long-distance pipelines, an online updated radial basis function neural network (RBF neural network) control method was proposed for the long-distance liquid supply system. Based on the analysis of the measured pressure fluctuations of the mining face and the process of the stable pressure liquid supply system, the influencing factors of the stable pressure liquid supply flow demand were obtained. The flow set of the stable pressure liquid supply system was established and fitted in the SimulationX–Simulink co-simulation model and the online correction was carried out by using the characteristics of the repeated action of the hydraulic support. Finally, the online updating RBF neural network regulator was established to realize the pressure regulator control of the pumping station, and the experimental platform was set up for verification. The results show that this method can effectively reduce the pressure fluctuations caused by the change in the flow demand of the mining face, and can adjust the flow rate of the mining face, reduce the pressure impact, and improve the efficiency of the machine.

Visualization of Bubble Behaviors in Flow Fields of PEM Water Electrolyzer

Proton exchange membrane water electrolyzer (PEMWE) has been considered to be a promising technology for green hydrogen production, primarily because of its significant advantages in terms of high efficiency, high purity and fast dynamic response [1]. During its operation, hydrogen/oxygen evolves from the catalyst layer (CL), transports through the diffusion layer (DL) and then releases to the flow channel, forming various two-phase flow regimes, including bubbly, slug, annular, etc [2]. The presence of bubbles not only covers the electrode surface, but also blocks the water delivery, creating a large mass transfer resistance and even terminating the cell operation [3]. Another issue associated with bubble management is that the conventional parallel and serpentine flow-field configurations showed a poor self-pumping effect, exhibiting a mismatch between bubble evolution and removal rates [4]. To address this issue, therefore, some novel flow field designs have also been proposed in recent years, but the underlying mechanism how two-phase flow regime in flow-filed channels affects the electrolyzer performance is still not clear.In this work, we investigate the effect of two-phase behavior on the electrolyzer performance via a visualization approach, as illustrated in Figure 1. Our preliminary results have shown that an increase of water supply flow rate has insignificant effect on the electrolyzer performance even at high current densities. It is observed that with increasing the water supply rate, many bubbles are still covering the electrode surface, meaning that water cannot be effectively supplied to the CL. To address this issue, a degassing layer, with a thinner rib and a wider channel, is introduced to the flow field design, which is able to promote the self-pumping effect of gas bubbles. This novel design can facilitate the rapid detachment of bubbles from the electrode surface, providing more paths for the water penetration into the CL. Acknowledgement This work was fully supported by a grant from the National Natural Science Foundation of China (Project No. 52022003). References Razmjooei, T. Morawietz, E. Taghizadeh, et al, Increasing the performance of an anion-exchange membrane electrolyzer operating in pure water with a nickel-based microporous layer, Joule, 5(7) (2021) 1776-1799.Rakousky, U. Reimer, K. Wippermann, et al, An analysis of degradation phenomena in polymer electrolyte membrane water electrolysis, J. Power Sources, 326 (2016) 120-128.Villagra, P. Millet, An analysis of PEM water electrolysis cells operating at elevated current densities, Int. J. Hydrog. Energy, 44(20) (2019) 9708-9717.O. Majasan, J.I.S. Cho, I. Dedigama, et al, Two-phase flow behaviour and performance of polymer electrolyte membrane electrolysers: Electrochemical and optical characterization, Int. J. Hydrog. Energy, 43(33) (2018) 15659-15672. Figure 1

Study on the modes transformation and emission characteristics of Ionic Liquid Electrospray Thrusters

Ionic Liquid Electrospray Thrusters (ILETs) exhibit distinct emission characteristics when operating in different emission mode under different conditions, which can significantly impact their performance. Therefore, to optimize the performance of ILETs and make them suitable for a wide range of space missions, it is necessary to investigate the emission mode characteristics of ILETs. In this study, the ionic liquid 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI-Im) was used to conduct experiments at varying supply voltage and flow rate conditions. The emitted current was measured and the liquid surface was imaged using a high-speed camera. The emission mode was estimated using algebraic calculations. Experimental results revealed that ILETs operate in the Ion-droplet Mixed mode at low flow rates, while the emission mode transforms into the Droplet mode as the flow rate increases. Similarly, as the supply voltage increases, the emission mode transforms from the Droplet mode to the Ion-droplet Mixed mode. The liquid surface height decreased with the supply voltage increase in each mode, and it increased with the flow rate in the Droplet mode. Notably, the liquid surface height in the Ion-droplet Mixed mode was similar to that in the Droplet mode at the lowest flow rate. Furthermore, the ion ratio significantly affected the thrust and specific impulse of ILETs.

Potential storage augmentation impacts on hydropower production, irrigation water supply and environmental flows in the Indus Basin in Pakistan

Study regionIndus River basin, Pakistan Study focusThe study assesses the implications on irrigation water reliability, hydropower production and environmental flows to the Indus Delta resulting from the implementation of large new storages on the Indus River. These large dams have the potential to impact water supply security of the Indus Basin Irrigation System which operates with a priority of maximising irrigation supply via the 1991 Water Apportionment Accord. Implementation of the Accord under future scenarios involving new large dams is open to interpretation. This study uses the daily time step Indus River System Model to simulate the potential impact of these new large dams on hydropower production, irrigation water supply and flows to the Indus Delta under different Accord interpretations. New insights for the regionPakistan possesses significant potential for increasing hydropower production from the Indus River through the construction of new reservoirs, which could raise the nationwide share of electricity generated from hydropower from 29% to 44–53%. This study demonstrates that augmenting storage capacity can yield threefold benefits – improved end-of-system environmental flows, more reliable irrigation supply for the Rabi season, and increased hydropower production. Additionally, this modelling approach can be instrumental in strengthening the existing water governance arrangements when considering the construction of new dams, thereby improving the health of the Indus delta ecosystem through the construction of dam construction.

Theoretical research on the application of impedance calculation in the design of high-intensity low-frequency acoustic generator

The impedance matching is essential in producing high-intensity acoustic waves. This paper studies the impedance calculation methods of modulators and double-chamber Helmholtz resonators based on fluid mechanics, aeroacoustics, and electro-acoustic analogy principles. The results: ① The impedance expression of the resonators is derived. ② The impedance variation law of the chamber volume, the stator size, the air supply pressure, the air supply flow, and the working frequency is calculated. ③ The impedance-matching design scheme of the two-chamber Helmholtz low frequency and high acoustic intensity generator is given. Based on the experimental results of the high acoustic intensity generating device that the author has manufactured in the closed space, the correctness of the impedance calculation and matching design scheme in this paper is verified. This method has guiding significance for the design of high-intensity acoustic generating devices in confined space.

Experimental investigation on diffusion and fountain behavior of bubble plumes in quiescent water

Bubble plumes are a common phenomenon, which are simultaneously hazardous and exploitable. Diffusion and fountain behavior, regarded as significant characteristics of bubble plumes, were investigated in this experiment utilizing high-speed photography and image processing techniques within a rectangular bubble column crafted from organic glass. The diffusion, coalescence, and collapse phenomena of bubble plumes were visualized during their ascent under varying gas flow rates in quiescent water. Furthermore, the influence of gas supply pressure, flow rate, and water depth on the fountain height was examined. The research findings demonstrate that an increase in gas supply pressure and flow rate leads to a subsequent rise in fountain height once the bubble plume reaches the surface. Conversely, a reduction in the fountain height is observed with an increase in the depth of gas release. Through the application of a dimensionless analysis method, the factors influencing the fountain height were correlated, resulting in the proposal of a relationship formula for predicting fountain height. The predicted outcomes exhibited good consistency with the data reported in this experiment.

Analyzing environmental flow supply in the semi-arid area through integrating drought analysis and optimal operation of reservoir

This study proposes a novel form of environmental reservoir operation through integrating environmental flow supply, drought analysis, and evolutionary optimization. This study demonstrates that simultaneous supply of downstream environmental flow of reservoir as well as water demand is challenging in the semi-arid area especially in dry years. In this study, water supply and environmental flow supply were 40% and 30% in the droughts, respectively. Moreover, mean errors of supplying water demand as well as environmental flow in dry years were 6 and 9 m3/s, respectively. Hence, these results highlight that ecological stresses of the downstream aquatic habitats as well as water supply loss are considerably escalated in dry years, which implies even using environmental optimal operation is not able to protect downstream aquatic habitats properly in the severe droughts. Moreover, available storage in reservoir will be remarkably reduced (averagely more than 30×106 m3 compared with optimal storage equal to 70×106 m3), which implies strategic storage of reservoir might be threatened. Among used evolutionary algorithms, particle swarm optimization (PSO) was selected as the best algorithm for solving the novel proposed objective function. The significance of this study is to propose a novel objective function to optimize reservoir operation in which environmental flow supply is directly addressed and integrated with drought analysis. This novel form of optimization system can overcome uncertainties of the conventional objective function due to considering environmental flow in the objective function as well as drought analysis in the context of reservoir operation especially applicable in semi-arid areas. The results indicate that using either other water resources for water supply or reducing water demand is the only solution for managing downstream ecological impacts of the river ecosystem. In other words, the results highlighted that replanning of water resources in the study area is necessary. Replacing the conventional optimization system for reservoir operation in the semi-arid area with proposed optimization system is recommendable to minimize the negotiations between stakeholders and environmental managers.

The outflow characteristics of PV water lifting systems based on multiple tracking strategies

In order to clarify the problems of high failure rate, low efficiency, and low outflow rate of PV water pumping stations in pastoral areas due to large differences in resource conditions and poor equipment matching, this study uses the PV water supply model, establishes a pilot site for PV human storage water supply in pastoral areas, carries out research on the relationship between solar energy resources, water supply demand and power system of PV water pumping stations based on group observation tests in the field, and analyzes the PV system. We analyzed the relationship between different tracking operation modes and the amount of solar radiation and water supply flow, and compared the outflow characteristics of fixed type, single-axis tracking type, and double-tracking axis type, in order to explore a kind of PV water pumping station technology suitable for human storage and drinking water in pastoral areas, which can meet the water demand of pastoral water users. The research results show that the single-axis and dual-axis water lifting systems are significantly more efficient than the fixed-support water lifting system, receiving solar radiation at more than 80% of the maximum radiation throughout the day, and lifting water flow at more than 90% of the maximum discharge flow. Compared with the fixed-support PV water lifting system, the radiation of the single-axis PV water lifting system increases by 28.9%, and the daily water output increases by 43%; for the dual-axis PV water lifting system, compared with the single-axis PV water lifting system, the daily radiation of the dual-axis PV water lifting system increased by 4.8% and the daily water output increased by 3.2%; the starting radiation of the PV water lifting system was 256 W/m2.

A novel personal comfort system for older adults in hot conditions: Design, modelling, and performance

This study introduces a novel personal comfort system aimed at establishing a relatively uniform thermal microclimate around the body to meet the thermal needs of seated elderly individuals under hot conditions. The system integrates cool air supply vents into a chair to provide thermal comfort by i) generating upward airflow by colliding jets to disperse cool air across the upper body; and ii) releasing air flow targeting the lower body by relying on buoyancy for air confinement.A computational fluid dynamic model was developed to predict the flow and thermal fields around the occupant who is seated on a chair equipped with the proposed system. The model was experimentally validated in a climatic chamber using a thermal manikin. An elderly bioheat and thermal sensation models were used to predict skin temperatures and corresponding sensation of elderly users. The microclimate was assessed in terms of effective confinement of cool air around users and improvement in elderly thermal sensation. At a total chair supply flow of 17 l/s, microclimate air confinement was attained. At 29 °C room temperature, the proposed system lowered the mean skin temperature from 34.15 °C to 33.33 °C and improved the whole-body TS, which decreased from slightly warm to neutral. At 33 °C room temperature, the mean skin temperature decreased from 35.6 °C to 33.99 °C and the sensation improved, decreasing from above warm to below slightly warm.

A novel solar system for photothermal-assisted electrocatalytic nitrate reduction reaction to ammonia

The traditional Haber-Bosch process for ammonia synthesis is plagued by high energy consumption and significant CO2 emissions, leading to a noticeable environmental impact. As a promising solution, solar photovoltaic electrocatalytic synthesis of ammonia has garnered significant attention. This study designed an electrocatalytic nitrite reduction system for ammonia production that employs solar photothermal-assisted and investigate the effects of different photovoltaic power supply voltage, heating temperatures, and flow velocities. The results demonstrate. the maximum ammonia production performance was achieved at 1.3 V under normal temperature conditions, resulting in a maximum current density and ammonia production rate of 26 mA cm−2 and 1422.4 μg, respectively. Upon heating to 40 °C, the maximum average current density of the system is 40 mA cm−2, and ammonia production is 2293 μg, representing 53.8 % and 61.2 % increasing in comparison to ambient temperatures. Although elevating the temperature to 60 °C led to increased average current density and ammonia production, the system's stability decreased to certain extent. Cyclic electrolysis conducted at 1.1 V and 40 °C for an hour revealed that ammonia production is 553.2 μg, 957.8 μg, 714.6 μg for flow rates of 10 mL/min, 20 mL/min, and 40 mL/min, respectively. These findings provide a reliable reference for implementing solar energy as a power source in ammonia synthesis.

Experimental investigation of flame behaviors of turbulent diffusion flames with different ullage heights

This work is aimed examine the effect of ullage height (tank roof to fuel surface) on the flame behavior of turbulent diffusion flames. A series of experiments with eight ullage heights (h = 0–28 cm) were conducted. Propane was issued from a gas burner (D = 20 cm) with different fuel supply rates. Experimental results showed that the total flame consists of an upper flame (Lupper, outside the tray) and a down-reaching flame (Ldown, inside the tray). It was found that Ldown decreases with fuel supply flow rate and there is a critical fuel supply flow rate (Q˙s,c), independent of the ullage height, above which there is no down-reaching flame. Depending on the ullage height and fuel supply rate, the flame behaviors can be divided into three regimes: (Ⅰ) restricted down-reaching, (Ⅱ) free down-reaching and (Ⅲ) no down-reaching. Based on the dimensionless analysis, correlations were developed to predict the down-reaching, upper, and total flame lengths, respectively. These correlations were validated against the experimental data in the paper and the previous literature. The present results are of importance to understand the flame behaviors for the burning of fires with large ullage heights and provide guidance in risk assessment of tank fires.

Analysis of Supply Chain Management Performance in the Community Coffee Production System in Bajawa, Ngada Regency

Research on Supply Flow Performance Management in the Bajawa People's Coffee Production System was carried out in Ngada Regency, with the aim of finding out the relationship between cooperation and the performance of the Bajawa coffee supply flow, knowing the relationship between information sharing and the supply flow performance of Bajawa coffee and knowing the long-term relationship with Bajawa coffee supply flow performance. Many factors can influence the performance of supply flow management in companies, including information sharing, long term relationships, and cooperation. The method used in this research is to analyze the relationship between the dependent variable (cooperation, information sharing and long-term relationships) and the independent variable (Bajawa coffee supply flow performance). From the results of the multiple linear regression analysis carried out, it shows that: the long-term relationship variable has the greatest influence on the Bajawa coffee SCM performance variable (dependent) with a coefficient value of (0.047), then the cooperation variable with a value of ( 0.019 ), and which has a The smallest influence is the information sharing variable (0.018). This means that the three independent variables have a positive and significant effect on the dependent variable.

Temperature distribution and heat transfer mechanism at the upstream surface of a moving burner

Moving fires are challenging because of their aerodynamic effects, which have gained wide attention recently. Concurrent flame spread can occur due to tilted flames, and the backward heating behavior of moving fires has not yet been addressed. To investigate these fundamental problems, a 1:10 scale burning car with an embedded propane-fueled porous burner was designed. Moving model experiments with eight heat release rates (HRRs) ranging from 6.1 to 27.3 kW and seven moving velocities varying from 2 to 10 m/s were conducted. The upstream two-dimensional temperature and the heat flux were measured by a thermocouple array and water-cooled heat flux gauges, respectively. The flame was extinguished when the velocity of the burning car (VBC) reached a threshold value, and this critical extinction VBC generally increases with the HRR. The maximum temperature on the upstream surface generally increased with the increase in VBC, and an exponential increase followed by a power law decay was observed for larger dimensionless HRRs (6.24–7.243). The upstream centerline temperature was correlated as two regimes because the difference between the intermittent and plume regions was small at higher VBCs. The exponents for the intermittent and plume regions were 0 and −7/2, respectively. Finally, the heat transfer mechanism for moving fires was elucidated. The movement effect played a dual role: accumulating and dissipating heat during the combustion process, and the cooling effect of the fuel-rich zone was more obvious for larger fuel supply flows.