Constant Gas Flow Research Articles

Modeling and Energy Flow Calculation of Integrated Energy System Based on Partial Differential Equation Model

This paper discusses the modeling and energy flow calculation method of integrated energy system based on partial differential equation model. By constructing a model that integrates power, heat, and natural gas networks, we analyze in detail the process of energy transmission, conversion, and storage in the system. In the process of modeling, the influence of compressor in constant compression ratio, constant outlet pressure and constant natural gas flow is specially considered, and the accuracy of the model is verified by specific data. In terms of energy flow calculation methods, we compare the performance of the unified solution method and the decomposition solution method. Data analysis shows that the non-gradient descent iterative method, gradient descent iterative method and decomposition solution method show consistency in calculation accuracy, that is, the calculation results of the three methods are the same. However, in terms of computational efficiency, the gradient descent iterative method shows significant advantages. Specifically, under identical computing conditions, our analysis reveals that the gradient descent iterative method exhibits a convergence rate approximately 30% faster than the decomposition solution method, resulting in a notable reduction of around 25% in computational time. This pivotal observation serves as a solid foundation for selecting a more computationally efficient approach in practical applications. To further enhance the computational efficiency, we have delved into deriving the Jacobian matrix of the model and subsequently proposed an advanced gradient descent iterative calculation technique. Through the actual test, this method not only improves the calculation speed, but also ensures the stability and accuracy of the calculation. The research in this paper not only provides a strong theoretical support for the optimal operation of the integrated energy system, but also provides a valuable reference for future research in related fields. Through specific data analysis, we prove the effectiveness and practicability of the proposed method, laying a solid foundation for the sustainable development of integrated energy systems.

Investigation of Churn and Annular Flow Transition Boundaries in Vertical Upward Gas-Water Two-Phase Flow

ABSTRACT Flow patterns in two-phase flow in vertical upward pipes are crucial for predicting phase distribution, flow transitions, and stability. Existing studies on churn to annular flow transitions primarily focus on flow rates, physical parameters, pressure, and temperature, often overlooking pipe diameter. This study addresses this gap using a multiphase pipe flow experimental setup to examine transitions under varying pipe diameters, gas flow rates, and liquid flow rates. Results show that with a constant liquid flow rate, increasing pipe diameter requires a higher gas flow rate to form annular flow, leading to greater pressure gradients and smoother fluctuations. Conversely, with a constant gas flow rate, larger pipe diameters decrease the liquid flow rate needed for annular flow, resulting in smaller pressure gradients and smoother fluctuations. Smaller pipe diameters make annular flow formation easier, with smaller pressure gradients but larger fluctuations. A novel churn-annular flow transition boundary model was developed, considering factors like gas shear force, surface tension, gravity, viscous force, and pressure gradient. Evaluated with 804 experimental data sets, the new model’s prediction accuracy exceeds 98.19%, outperforming traditional models with 53.92%-86.27% accuracy, enhancing applicability across varying diameters.

Pressure Source Model of the Production Process of Natural Gas from Unconventional Reservoirs

This work is focused on developing a computational model to predict the production rate and pressure evolution of natural gas from unconventional reservoirs, particularly shale gas deposits. The model is based on the principle of conservation of mechanical energy and was developed from the transient solution of Bernoulli’s equation. This solution was obtained by computing the pressure evolution in the well resulting from the combined action of extracting the free gas and of gasification from kerogen. The transient behavior of gas production by hydraulic fracturing was calculated by numerically integrating Bernoulli’s equation. The curves representing gas flow evolution were considered as a series of stepwise steady states under a constant gas flow rate, similar to the pressure–time curves. These time steps were connected by instantaneous drops in pressure or gas flow rates. On the other hand, the delayed release of the adsorbed and dissolved gas in the kerogen was accurately calculated by introducing a semi-empirical gas pressure source term into the gas well pressure equation. The effect of this source is to gradually increase the gas pressure in the reservoir, emulating the gas release mechanisms from the organic matter. Model validation was based on production data from the unconventional reservoirs Eagle Ford, U.S.A., and Burgos basin, México. The initial measured gas production rate was used to determine a global friction factor of the gas flowing out from soil cracks and ducts. Additionally, measured production rate data were used to determine the coefficients of the source term function. Pearson correlation coefficients of 0.97 and 0.96 were obtained for Eagle Ford and Burgos basins data, respectively. In contrast, the corresponding coefficients calculated from the traditional Arps’ model were 0.89 and 0.5, respectively. The present pressure source model (PSM) represents a new approach to characterize the process of gas production from unconventional reservoirs, proving to be accurate in forecasting both the gas flow rate and pressure evolution during gas production. The postulated pressure source term was shown to mimic the desorption and diffusion kinetics, which release free gas from the kerogen.

Dynamics of bubble formation on superhydrophobic surface under a constant gas flow rate at quasi-static regime

Dynamics of bubble formation on superhydrophobic surface under a constant gas flow rate at quasi-static regime

Optimization of CRDI engine operating parameters using response surface methodology utilizing lemon peel oil biofuel enriched with hydroxy gas

The current study aims to optimize the operational variables of a CRDI engine in Dual-Fuel Mode (DFM). Hydroxy gas (HHO) was generated through water electrolysis using a concentric four-cylinder dry cell electrolyzer with NaOH catalyst, and it was introduced into the inlet manifold as the primary fuel. The pilot fuel consisted of Lemon Peel Oil (LPO) and pure diesel directly injected into the cylinder. An experimental matrix comprising 17 distinct runs was designed using Design of Experiments (DoE), utilizing Box-Behnken Design (BBD) based on Response Surface Methodology (RSM). The RSM model was created depending on the experimental data, and then operating parameters were optimized utilizing the desirability technique. The optimal engine operational variables were identified for the B25 LPO mixture with a constant HHO gas flow rate of 0.5 LPM, a Compression Ratio (CR) of 21.5, an Injection Pressure (IT) of 450 bars, and an inlet air temperature of 87℃. The optimized results were 30.18 % for Brake Thermal Efficiency (BTE), 9.532 g/kW-hr for Carbon Monoxide (CO) emission, 0.253 g/kW-hr for Unburned Hydrocarbon (UHC) emission, and 23.510 g/kW-hr and Nitrogen Oxides (NOx) emission, yielding a total desirability of 0.7641. Empirical validation of the optimized responses at these input conditions demonstrated their conformity to acceptable error ranges.

Lumped model for a quasi-continuously operating open metal hydride heat pump system

Hydrogen as a potential future fuel for fuel cell vehicles is mostly stored in high-pressure tanks at 350 or 700 bar, which requires energy-intense compression of typically 15 % of the lower heating value. For the recovery of parts of the compression work, a promising possibility is the usage of an open metal hydride heat pump. Similarly to other sorption-based heat pump systems, in order to reach high specific thermal power, it is crucial to find a trade-off in the design and operation of the reactor between two main factors: enabling fast reaction dynamics and reducing losses due to temperature switches. The present work introduces a steady-state model with lumped metal hydride and reactor mass considering one-dimensional heat and mass transfer, which is able to quickly predict the corresponding specific thermal power and efficiency. A special focus is on the calculation of the non-complete conversion due to an operation at constant gas flow. The model is validated with existing experimental data over a broad range of operation conditions in terms of metal hydride specific hydrogen mass flow (1.6–7.6 gH2 min−1 kgMH-1) and temperature boundary conditions (cold side temperature: 13–25 °C, hot side temperature: 24–42 °C). It is capable of describing the specific thermal power and the efficiency as the two main performance indicators with a suitable accuracy. To give an example of the applicability of the developed tool, a generic discussion of the performance limitations of the selected reactor design is carried out, indicating that the reactor of the validation experiment is mainly mass transport limited.

Role of carbonization parameters on surface and microstructural and crystalline properties of mesoporous coconut shell char: Quantitative and structural study

The present work focuses on the synthesis of inactive mesoporous char using the carbonization method. The experiment was conducted at various conditions using a constant flow of nitrogen gas with variable temperature ramp and carbonization temperature i.e., 5 °C /min to 20 °C /min and 400 °C to 800 °C respectively. The product was identified by calculating its surface area, pore size, micro strain, interplanar spacing, packing density, full-width half maximum, crystallite size, lateral size, no of layers, dislocation density, crystallinity index, and morphological characterization. It was revealed that the best results in terms of surface area, pore size, micropore volume, and burn-off value of the char were observed at a carbonization temperature of 700 °C with a heating rate of 10 °C/min. The calculated values of surface area, pore size, micropore volume, and burn-off were found to be 211.816 m2/g, 2.288 nm, 0.121 cm3/g, and 20.2 % respectively.

Coke formation pathway under various reaction conditions during the production of syngas in a dielectric barrier discharge plasma environment using CeO2 nanorods supported Ni catalysts

Plasma-assisted dry reforming of methane (DRM) was investigated using CeO2 nanorods (NR) supported Ni catalysts in a fixed-bed coaxial dielectric barrier discharge (DBD) reactor. This study individually examined the catalyst support, packing material, and 10 wt% Ni-CeO2 NR catalyst under pure thermal and plasma-assisted thermal DRM environments to explore the plasma-thermal synergy. Support and packing material displayed no discernible reactivity under thermal DRM within 450 °C; however, the catalyst exhibited reactivity beginning around 350 °C. Alternatively, plasma-assisted DRM experiments revealed a distinct reaction occurrence at significantly lower temperatures across all sample types. Introducing plasma demonstrated a significant enhancement in CH4 conversion compared to CO2 conversion. The 10 wt% Ni-CeO2 NR catalyst in plasma-assisted DRM testing showed increasing conversions of CH4 and CO2 with rising temperatures, peaking at 52.1 % and 46.1 %, respectively, at 450 °C. The catalyst’s improved performance in the plasma environment can be attributed to the enhanced metal-support interaction between NiO and the CeO2 NR support, a consequence of the rich surface oxygen vacancy concentration. However, this increase in conversion was accompanied by an escalation in carbon deposition. Considering contributions from the thermal DRM process, the optimal operating temperature was determined as 350 °C. Increasing plasma power at this temperature led to enhanced conversion. However, beyond a threshold of 23.8 W power, the reaction path altered, resulting in reduced syngas output. Increasing the CH4:CO2 feed gas flow ratio, while maintaining constant plasma power and temperature, elevated H2/CO generation. Moreover, increasing the total flow rate under identical conditions, with a constant feed gas flow ratio, reduced both conversions due to decreased chemical residence time. Consequently, under a constant feed gas ratio, a higher syngas yield is achievable with lower overall flow rates.

Optimization of Wire Arc Additive Manufacturing Process Parameters for Low‐Carbon Steel and Properties Prediction by Support Vector Regression Model

This study aims to optimize the process parameters of wire arc additive manufacturing for ER70S6 steel and to build a machine‐learning (ML) model to predict the properties of deposited specimens. Process parameters such as current, voltage, and travel speed are optimized considering other process parameters constant (gas flow rate, contact tip to the work distance, and preheat). The optimization is made using the response surface method and validated the properties by experimentation, including tensile testing and metallography. A support vector regression (SVR) ML model is implemented to predict the material's properties to substantiate the outcomes’ values in every possible combination for the given parameters. In the study's findings, a significant enhancement is revealed in specimen quality, marked by reduced irregularities and porosity, and a remarkable increase in ultimate tensile strength up to 40%, validated through the SVR model. In this study, a valuable path that can be extended to predict properties of other material systems is sketched.

Experimental investigation of CO2-CH4 core flooding in large intact bituminous coal cores using bespoke hydrostatic core holder

This paper presents the CO2-CH4 core flooding and permeability studies conducted with large intact coal core samples. A bespoke core holder was designed and commissioned to conduct the core flooding experiments. The CO2 and CH4 core flooding experiments were performed to understand the CH4 displacement efficiency of CO2 from the coal cores and the permeabilities of CO2 and CH4 during the core flooding. The CO2-CH4 gas displacement experiments were performed on intact coal cores of 9.9 cm in diameter with varying lengths to make up 60 cm-long cores that were extracted from coal blocks using a diamond core-drilling machine. The CO2 and CH4 core flooding experiments were conducted using the core holder at maximum of 1450 psi confining pressures and at 298.15 K. A constant gas flow rate of 1 mL/min was maintained to flood the core with an outlet backpressure set at 25 to 30 ± 2 psi. The core holder is equipped with two differential pressure taps to measure the pressure change along the core length to measure the differing permeability along the core lengths which is difficult to observe in the smaller size intact samples. Both coals, EMB and ZM, showed favourable CH4 displacement efficiencies of CO2 about 96.5% and 99.7%, respectively. The dependency of the core lengths on the permeability measurements is more pronounced in the results obtained in the current study. The results indicated a decreasing trend in CO2 permeability and increasing CH4 permeability during CO2 injection. The observation indicated CO2 adsorption and CH4 displacement. Overall, the core flooding experiments improved the current understanding of CO2-CH4 core flooding by showing the core size dependence in permeability measurement experiments. In contrast to the single species CO2 flow experiments, the permeability variation during the CO2-CH4 flooding and the CH4 sweeping efficiency of CO2 provided insights into the CO2-ECBM operational design.

Continuous measurement of gas permeability in non-homogeneous hydrate reservoirs under effective pressure via a novel apparatus

Gas permeability is a key physical parameter to determine the exploitation efficiency of natural gas hydrate (NGH). However, the relevant research mainly focuses on the permeability of homogeneous hydrate reservoirs, there have been no studies of non-homogeneous hydrate reservoirs. Therefore, a novel permeability measurement apparatus was designed in this study, which used two core holders in parallel to achieve the spatio-temporal continuous measurements of gas permeability for non-homogeneous reservoirs. Marine soils obtained from the South China Sea were used to remold the non-homogeneous hydrate reservoirs, including two homogeneous hydrate reservoirs with water saturation of 40% (reservoir A) and 80% (reservoir B), respectively. The constant gas flow of 0.5 ml/s and constant back pressure of 3 MPa was carried out to measure the gas permeability. The experimental results showed that the gas permeability measured in this work had similar regularities with other literature data. When the effective pressure increased from 1 MPa to 6 MPa, the permeability of reservoir A, reservoir B, and non-homogeneous hydrate reservoir decreased from 15.2 mD to 10.9 mD, 10.5 mD to 4.6 mD, and 12.5 mD to 8.5 mD, respectively. In addition, the variation in the non-homogeneous coefficient showed three stages: 1–2 MPa stage, 2–3 MPa stage, and 3–6 MPa stage. What's more, the permeability damage rate of non-homogeneous reservoirs increased by nearly 35% with the increase of effective pressure. These findings obtained by this apparatus will enhance the understanding of gas permeability in the non-homogeneous hydrate reservoirs, and guide further field exploitation of hydrate reservoirs.

Non-Catalytic and Catalytic Conversion of Fruit Waste to Synthetic Liquid Fuel via Pyrolysis

Plum stone stands out as an alternative biomass source in terms of obtaining fuel and chemicals with or without catalysts under different conditions. Under variable heating rates (10, 50, and 100 °C min−1) and pyrolysis temperatures (400, 450, 500, 550, and 600 °C), plum stone was pyrolyzed at a constant rate in a constant sweep gas flow (100 cm3 min−1) in a tubular fixed-bed reactor. According to the results, an oil yield reaching a maximum of 45% was obtained at a heating rate of 100 °C min−1 and pyrolysis temperature of 550 °C in the non-catalytic procedure. The catalytic pyrolysis was carried out with two selected commercial catalysts, namely ZSM-5 and PURMOL-CTX and clinoptilolite (natural zeolite, NZ) under optimum conditions with a catalyst ratio of 10% of the raw material. With the addition of catalyst, the quantity and quality of bio-oil increased, including calorific capacity, the removal of oxygenated groups, and hydrocarbon distribution. In the presence of catalysts, an increase was observed in terms of desirable products such as phenol, alkene, and alkane, and a decrease in terms of undesirable products such as acids. Considering and evaluating all the results, the use of zeolite materials as catalysts in pyrolysis is a recommended option for obtaining enhanced chemicals and fuels.

Mechanical Characteristics of Structural Thick Plates Depending on Vacuum Time of RH Process

The structural thick plates were manufactured by varying the vacuum time at a constant argon gas flow rate and degree of vacuum during the Ruhrstahl Heraeus (RH) refining process. The inclusion and mechanical properties of the structural thick-plate specimens were evaluated according to vacuum time. The nitrogen in the converter had an effect after the RH process, and as the vacuum time of the RH process increased, the nitrogen content also increased. The nitrogen in the continuous casting (CC) decreased more than that in the converter, and as the vacuum time increased, the hydrogen decreased. Al2O3·CaO, MnS and Al2O3·MgO inclusions were observed in the structural thick plate. The average size of the oxides was (6.1 to 33.46) μm, while the average size of the Al-O-based inclusions was (4.26 - 6.3) μm. The mechanical properties, such as tensile strength, yield strength, and elongation, were affected by the vacuum time of the RH process with 10 min being the best. The micro-Vickers hardness showed dispersion regardless of the vacuum time of the RH process, which can be explained by the Weibull probability distribution. From the shape and scale parameters, although the specimen with the vacuum time of the RH process of 10 min showed a large dispersion in the micro-Vickers hardness, the characteristic value of 63.2 % was the best.

The Tritube: Facilitating Upper Airway Surgery With an Ultrathin Cuffed Airway Device.

The Tritube is a narrow-bore cuffed tracheal tube (outer diameter 4.4 mm and inner diameter ~2.4 mm) that permits effective alveolar gas exchange using flow-controlled ventilation. Constant gas flow delivers physiological minute volumes, within preset pressure limits, and applies suction to the airway during expiration. The technique has attracted interest for laryngotracheal microsurgery as it provides superior surgical exposure and avoids many of the complications associated with high-frequency jet ventilation. Cuff inflation protects the lower airway and produces a motionless operating field. We describe the structure of the device, discuss its benefits, and suggest how it should be used clinically.

Gas hold-up analysis in an unsteady stirred vessel by means of infinite series

Abstract The use of a liquid level sensor made it possible to measure changes in gas hold-up over time in a stirred tank during unsteady mixing. These results were subjected to Fourier time series analysis and a model of gas hold-up changes in time was proposed. It allowed one to determine the model value of gas hold-up, which can be useful for characterizing gas hold-up during unsteady mixing and as a comparison to gas hold-up during steady mixing. The characteristic frequency was also determined, which corresponds to about twice the oscillation frequency. Model gas hold-up values for coalescing and non-coalescing systems were compared. Moreover, the change of the gas hold-up at constant maximum stirrer rotation frequency and variable gas flow rate for different oscillation frequencies was investigated.

Synthesis and Characterization of Nanosized Ti<sub>3</sub>O<sub>5</sub> Crystals under Inert Gas Flow

In the research, we show that suboxidic Ti7O13 and rutile TiO2 phases formed in addition to the general Ti3O5 phase when the sintering temperature was set at constant argon gas flow rate. Suboxidic Ti7O13 and rutile TiO2 phases were removed by tuning the flow rate of argon gas at constant sintering temperature. At the 1300°C temperature, the smallest Ti3O5 nanocrystals with a size of ~9 nm were produced. Flat shaped particles of Ti3O5 crystals were observed in SEM measurements.

Automatic control of the boiler heat power based on changing hydrocarbon fuelʼs calorific value

This paper is devoted to the development and research of an advanced approach to automatic control of the heat output of the boiler when compensating the load disturbances by regulating the composition of the combusted hydrocarbon fuel mixture. The proposed approach gives the opportunity to design the boiler’s automatic control system (ACS) with the possibility of creating the conditions for the formation and determination of the current calorific value of the gases mixture, which corresponds to the current heat load of the boiler, as well as determining the flue gas flow and temperature in the boiler. The implementation of the developed approach of the boiler’s load control allows for providing a constant nominal flue gas flow at any level of heat output. The fuel composition control process consists of mixing certified and non-certified hydrocarbon gases, which ensures maximum efficiency and compliance with environmental emission standards. The effectiveness study of the proposed approach is carried out in the development of the heat output ACS for the GM-50 boiler and conducting a computational experiment of operating at a power different from the nominal one. The obtained results fully confirm the high efficiency of the developed approach, as well as the expediency of its application for boilers of various types and capacities when operating at a power different from the nominal one.

Co-Carbonization of Discard Coal with Waste Polyethylene Terephthalate towards the Preparation of Metallurgical Coke

Waste plastics such as polyethylene terephthalate (w-PET) and stockpiled discard coal (d-coal) pose a global environmental threat as they are disposed of in large quantities as solid waste into landfills and are particularly hazardous due to spontaneous combustion of d-coal that produces greenhouse gases (GHG) and the non-biodegradability of w-PET plastic products. This study reports on the development of a composite material, prepared from w-PET and d-coal, with physical and chemical properties similar to that of metallurgical coke. The w-PET/d-coal composite was synthesized via a co-carbonization process at 700 °C under a constant flow of nitrogen gas. Proximate analysis results showed that a carbonized w-PET/d-coal composite could attain up to 35% improvement in fixed carbon content compared to its d-coal counterpart, such that an initial fixed carbon content of 14-75% in carbonized discard coal could be improved to 49-86% in carbonized w-PET/d-coal composites. The results clearly demonstrate the role of d-coal ash on the degree of thermo-catalytic conversion of w-PET to solid carbon, showing that the yield of carbon derived from w-PET (i.e., c-PET) was proportional to the ash content of d-coal. Furthermore, the chemical and physical characterization of the composition and structure of the c-PET/d-coal composite showed evidence of mainly graphitized carbon and a post-carbonization caking ability similar to that of metallurgical coke. The results obtained in this study show potential for the use of waste raw materials, w-PET and d-coal, towards the development of an eco-friendly reductant with comparable chemical and physical properties to metallurgical coke.

The Influence of Direct Non-Thermal Plasma Treatment on Soot Characteristics under Low Exhaust Gas Temperature

This study aimed to assess the effectiveness of nonthermal plasma (NTP) technology utilizing a dielectric barrier discharge (DBD) reactor, both with and without exhaust gas recirculation (EGR), in reducing soot particles and their impact on nitrogen oxides (NOx). The experiment involved maintaining a constant flue gas flow rate of 10 l/min, employing high voltage values of 0, 6, and 10 kV, fixed frequency of 500 Hz and setting the various IMEP of 5, 6, and 7 bar and the engine speed at 2,000 rpm. The findings demonstrated that NTP was successful in removing NOx by approximately 16.84% and 17.01%, achieving particle matter (PM) removal efficiencies of around 60.79% and 81.13%, and effectively reducing activation energy by approximately 18.34% and 31.5% (with and without EGR, respectively) at a high voltage of 10 kV. These results highlight the potential of NTP technology in mitigating emissions and reducing the environmental impact associated with diesel engines.

Study the Effect of Dielectric Barrier Discharge (DBD) Plasma on the Decomposition of Volatile Organic Compounds

Recently, research has focused on non-thermal plasma (NTP) technologies as a way to remove volatile organic compounds from the air stream, due to its distinctive qualities, which include a quick reaction at room temperature. In this work, the properties of the plasma generated by the dielectric barrier discharge (DBD) system and by a glass insulator were studied. Plasma was generated at different voltages (3, 4, 6, 7, 8 kV ) with a fixed distance between the electrodes of 5 mm, and a constant argon gas flow rate of (2.5) I/min. DBD plasma emission spectra were recorded for each voltage. The Boltzmann plot method was used to calculate the electron temperature in the plasma ( ), and the Stark expansion method was used to calculate the electron density ( ). The decomposition of organic compounds (cyclohexane) was also studied using DBD plasma. The results showed that the potential difference between the two electrodes has a clear effect on the plasma parameters, as the temperature of the electrons and the density of electrons increase with the increase in the potential difference between the two electrodes. The DBD plasma system proved to be a good way to decompose volatile organic compounds, as the results proved the emission of hydrogen gas as one of the dissociation products of cyclohexane.