Stokes Flow Within Networks of Flow Branches

Superconducting cavity is usually needed to be gradually cooled from room temperature to the superconducting temperature zone (4.2 K and below) in the testing and sophisticated operation process of superconducting cavity. The purpose of this paper is to study the cooling law on the helium cooldown process for the 650 MHz two-cell superconducting cavity with the unsteady numerical simulation. A three-dimensional coupled heat-flow model of 650 MHz two-cell superconducting cavity was established. The unsteady numerical simulation of different inlet temperatures, flow rates and pressure conditions was carried out. The equivalent convective heat transfer coefficient and temperature distribution of 650 MHz two-cell superconducting cavity during cooldown process were obtained. The effects of cooling time and entrance parameters on the cooldown process were analyzed. The temperature distribution of the lower intersection lines has a large drop in the initial stage of cooldown process (120 s), while the temperature near the flanges at the both ends is still higher (remaining at the initial temperature of 300 K). With the passage of time, the temperature of the upper and lower intersection lines decreases. The maximum temperature difference on the lower intersections is within 2 K in the final stage of cooldown process (3600 s). The maximum temperature difference increases by 180%, and the difference between the maximum temperature and the minimum temperature (dT) at the end of a cooldown stage increases by 130% after 1 h, respectively, when the inlet temperature drops from 290 to 270 K (under the condition of the initial temperature of 300 K). The maximum temperature difference and the dT at the end of a cooldown stage increase with the decrease in the inlet temperature. The maximum temperature difference increases with the increase in the inlet flow rate, while the dT at the end of a cooldown stage decreases with the increase in the inlet flow rate. The effect of changing the inlet flow rate on the cooling rate is not as obvious as changing the inlet temperature. Once there is a certain flow rate, the advantage of further increasing the flow rate to reduce the temperature of the superconducting cavity is not so great.

This study aims to address the challenge of predicting pipe sticking accidents in petroleum drilling engineering. In response to the high blindness of tradi-tional empirical qualitative operations, the difficulty of mathematical models in accurately reflecting drilling laws, and their poor operability, machine learning methods such as neural networks (NNs), support vector machines (SVM), and random forests are introduced for pipe sticking prediction re-search. Adhering to the principles of sample representativeness, category balance, and diversity, 9 drilling parameters including depth, drilling speed, weight on bit (WOB), torque, friction coefficient, outlet temperature, rota-tional speed, inlet flow rate, and outlet flow rate were selected. Drilling data from 30 wells in the Yan'an area were collected. Measurement data within a certain period before pipe sticking were used as pipe sticking samples, which were cross-arranged with normal samples to construct the training dataset. By comparing the performance of SVM (linear kernel, radial basis kernel) and random forest models, the results show that the random forest performs the best. In its confusion matrix, the number of correctly predicted samples for true labels 0 and 1 is 190 and 207 respectively, with only 9 and 5 misclassifi-cations. The accuracy rate reaches 0.966. In summary, this study confirms that the random forest has significant advantages in balancing "accuracy and efficiency" in pipe sticking prediction tasks, providing a reliable early warning model and technical support for safe drilling operations.

Silver nanoprisms (SNPs) have attracted significant attention due to their surface plasmon resonance behaviour, which is strongly dependent on their size and shape. The enhanced light absorption and scattering capacity of SNPs, make them a promising candidate system for non-invasive imaging and drug delivery in nanoparticle-assisted diagnostics and therapy. However, systemic administration of silver nanoparticles (AgNPs) at high concentrations may result in toxic side-effects, arising from non-targeted bio-distribution. These drawbacks could be mitigated by employing liposomes as carriers for AgNPs. However, there is a lack of systematic studies on production and subsequent physico-chemical characterisation of liposomal systems encapsulating SNPs. The present study therefore investigated the synthesis of liposomes encapsulating SNPs (Lipo/SNPs) using a continuous-flow millimetre-scale reactor, whereby liposome formation was governed by a solvent exchange mechanism. An aqueous phase and an ethanolic lipid phase were conveyed through two separate inlet channels, and subsequently travelled through a serpentine-shaped channel where mixing between the two phases took place. The synthesis process was optimised by varying both liposome formulation and the operating fluidic parameters, including the ratio between inlet flow rates (or flow rate ratio) and the total flow rate. The obtained Lipo/SNPs were characterised for their size and electrostatic charge, using a dynamic light scattering apparatus. Liposome morphology and encapsulation efficiency of SNPs within liposomes were determined by transmission electron microscopy (TEM) imaging. The synthesised negatively charged Lipo/SNP samples were found to have an average size of ∼150 nm (size dispersity < 0.3). The AgNPs encapsulation efficiency was equal to 77.48%, with mostly single SNPs encapsulated in liposomes. By using a multiangle TEM imaging approach, quasi-3D images were obtained, further confirming the encapsulation of nanoparticles within liposomes. Overall, the formulation and production technique developed in the present study has potential to contribute towards mitigating challenges associated with AgNP-mediated drug delivery and diagnostics.

Computational analysis of gas–liquid flow in an idealised CANDU reactor header under conditions that are relevant to small-break loss-of-coolant and loss-of-flow accidents

The functionality of pressure regulating valves (PRVs) is important for proper uniformity and efficiency of irrigation during center pivot irrigation, especially when the center pivot operates on sloping terrain. In practice, the regulated pressure at the PRV outlet is slightly influenced by its inlet pressure, the flow rate through it, and hysteresis effects. The objectives of this work were (a) to evaluate operational characteristics of PRVs based on requirements stated by ISO 10522 (1993) and (b) to model the regulated pressure as a function of inlet pressure and flow rate through the valve considering hysteresis. We carried out tests to evaluate regulation uniformity, regulation curve, hysteresis, and the regulated pressure as function of flow rate and inlet pressure. The following three models of PRVs were evaluated: 10 PSI, 15 PSI, and 20 PSI. For each model, three samples were tested under increasing and decreasing conditions of inlet pressure, within the range from 49.03 to 784.53 kPa, with increments of 49.03 kPa. In addition, flow rates were tested within the range of 0 and 4 m3 h−1. From the gathered data, models to predict outlet pressure as a function of inlet pressure and flow rate were fitted.

The pressure distribution across a flowing electrolyte - direct methanol fuel cell (FE-DMFC) stack was numerically evaluated using semi-empirical equations for friction and loss coefficients. The stack is considered to have “U” shape manifold design with parallel serpentine fuel channels. The flow is assumed to be laminar and the flow rate in each cell of the stack is determined using the Hardy-Cross method. The results show that, the mass flow rate of methanol is greater at the inlet and declines as the fuel travels further within the stack manifolds. It was further discovered that pressure drop inside the inlet manifolds increases with stack length while the pressure drop inside the individual cell channels tend to decrease with stack length. Finally, the stack power output is estimated by assuming single cell power outputs at various operating current densities and methanol inlet flow rates based on experimental data obtained from the literature.

Solution reversible addition fragmentation chain transfer (RAFT) polymerization of butyl acrylate in 50 wt% toluene, initiated with 2,2′‐azobisisobutyronitrile and mediated with 3‐benzyltrithiocarbonyl propionic acid, is carried out in a tube reactor of 1.65 mm inner diameter. The tube reactor is operated in three modes: batch tube reactor (inlet and outlet closed, recycle open), continuous tube reactor (inlet and outlet open, recycle closed), and loop tube reactor (inlet, outlet, and recycle all open). The effects of inlet and outlet flow rates, residence time, and recycle ratio on the polymerization rate and polymer molecular weight distribution (MWD) are systematically investigated. The dynamic and steady state kinetics of the three modes of operation are analyzed and compared. Polymer samples having multimodal MWD are generated using the loop reactor. It is found that the MWD and multimodality can be readily controlled by residence time (τ) and recycle ratio.

The timing of the valves of a hydraulic motor plays an important role in determining the throttling energy. To reduce this dominating energy loss, the timing of the valves must allow the fluid in the chamber to be precompressed and decompressed such that there is minimal pressure differential across the transitioning valve. The optimal valve timing to achieve precompression and decompression is a function of the motor displacement, angular velocity, pressure, and air content of the fluid, thus to achieve high efficiency at all conditions, active valve timing is required. The valves in most hydraulic motor architectures are mechanically timed to the piston displacement, rendering it impossible to change the valve timing as a function of operating conditions. This paper presents one novel valve architecture that allows for such processes: a rotary valve that is controlled independently of the piston displacement, enabling active timing control. To validate the concept and test the motor valve at fixed timing and fixed displacement conditions, a prototype valve was installed on a single cylinder 3.5 cc/rev slider-crank piston motor. The nominal timing of the valve was optimized for operation for a pressure of 7 MPa, 2% entrained air by volume, and an angular velocity between 10 and 30 Hz. A model, including the pressure dynamics, leakage, compressibility, check valve dynamics, and geometry dependent parameters is developed, simulated, and compared to the experiment. The experimental system includes instrumentation for measuring the inlet and outlet flow rates, piston position, and pressure in the inlet, outlet, and cylinder. A comparison between the model and experimental data shows good agreement and demonstrate the large impact of valve timing on efficiency.

Operating cost reduction and/or air pollution abatement via hydrogen integration is a research issue that has recently attracted considerable attention in the petroleum refining industries. Although a number of mathematical programming models have been developed to generate the optimal hydrogen distribution schemes, there is still room for further improvement. In particular, the primary deficiencies in current modeling practices can be attributed to (1) unreasonable unit models of the hydrogen users and producers and (2) incomprehensive design considerations. The conventional models of hydrogen users (such as the hydrotreater and hydrocracker) were usually formulated according to fixed throughputs and also constant feed and product concentrations. On the basis of the shortcut calculation method proposed in this study, not only these inlet and outlet flow rates and concentrations can be treated as decision variables but also their interactions can be characterized with more consistent material-balance constraints. On the other hand, because every hydrogen producer, e.g., the steam reforming plant, was regarded only as a simple hydrogen source in the past, the more rigorous models of its embedded units are built and incorporated in the improved mathematical program. As a result of these modifications, better design options can be identified in the present study. To ensure comprehensive design considerations, all often-encountered seasonal variations in model parameters and options to add extra compressors, purifiers, and fuel cells are considered in a novel multiperiod formulation. Furthermore, as an alternative to numerically solving this model, a systematic timesharing algorithm is also devised to manually integrate the conventional single-period designs to form a less economical but more flexible network structure for operations in all periods. Finally, extensive case studies have been carried out to test the proposed design methods, and three examples are reported.

This study examines the effects of water vapor on the performance and stability of a Roots-type hydrogen circulation pump. The accuracy of the numerical model was initially confirmed using air as the experimental medium, and subsequent simulations were conducted with pure hydrogen or mixed media containing water vapor. Analysis of pressure and velocity distribution within the pump revealed that water vapor does not significantly impact these factors. However, the interaction between hydrogen and water vapor results in the formation of larger hydrogen clusters, reducing internal leakage flow and leading to a slight increase in inlet and outlet flow rates. The presence of water vapor in the suction chamber increases turbulence energy in the root region of the rotor, influencing flow patterns and creating multi-scale vortex structures. In the exhaust chamber, the turbulence energy is lower and there are fewer vortices, but high-energy vortices may occur at the connection to the exhaust pipe, affecting the outlet flow rate.

We describe a technique for the fabrication and use of a microfluidic flow device that has portions that are open to the external environment. Matching inlet and outlet flow rates in the device forms virtual walls through surface tension at the liquid-air interface. Traditional instrumentation, such as the patch-clamp pipette, can be introduced into the flow stream through the surface-tension walls, thereby combining decades of electrophysiology techniques with the benefits of microfluidic environmental control of in-vitro tissue samples such as neural cultures and brain slices.

A solvent gradient mode was applied to the simulated moving bed (SMB) chromatography for the separation of two amino acids, phenylalanine and tryptophan, for the first time. The optimal design of such a solvent gradient SMB (SG-SMB) system was performed under a four-zone open loop configuration, in which zone IV is disconnected from zone I. One of the prerequisites for such an optimal design is to obtain the adsorption isotherm and mass-transfer parameters (i.e., intrinsic parameters) of ethanol that functions as a mobile phase modifier. For this task, a multiple frontal experiment was carried out, which showed that ethanol followed a Langmuir-type adsorption behavior. Based on the resultant parameters of ethanol, the SG-SMB for amino acid separation was optimized to maximize the productivity under the constraints of pump capacities and product purities. The inlet and outlet flow rates, the switching time, and a local distribution of ethanol along the chromatographic bed were optimized using non-dominated sorting genetic algorithm with elitism and jumping genes (NSGA-II-JG) and rate-model simulations. The optimal SG-SMB for amino acid separation was found to have 110% higher productivity, 53% lower desorbent consumption, and 71% higher product concentration, compared to the corresponding isocratic SMB.

Over the past few decades, oil recovery is becoming a more significant issue. Not only in reservoirs but also in surface equipment, the loss of oil has to be degraded owing to its value. Especially, in Karakus Field, Turkey, throughout a year, more than 6,000 bbl oil is lost from just free water knock out (FWKO) which is a strikingly challenge which has to be dealt with. Technically, due to stability of microemulsion for oil in water, the loss of oil occurs. In terms of increasing operating pressure of FWKO, entropy decreases. Thus, increments of Gibbs free energy can be supplied. Consequently, by breaking the stability of microemulsion, better quality separation can be obtained in disposal water. This study explained that oil loss from outlet of the FWKO was attenuated by increasing pressure of vessel, while other parameters were steady such as temperature, inlet and outlet flow rate and etc. in Karakus Field. By 50 psi gradually increment of vessel pressure from 100 psi to 300 psi, quantity of oil in water from outlet of the vessel was observed at 4,300 and 6,200 bbl/day disposal water rates. By augmenting the pressure of knock out, oil in disposal water which was conveyed to injection wells reduces dramatically. According to experimental results, a significant relation as exponentially between pressure and oil in water was found. Briefly, 900 and 1,500 bbl of oil can be saved annually in order with two disposal water rates.

In this paper, a computational fluid dynamics (CFD) calculation was used to evaluate the effects of the inlet feed flow rate and concentration fluctuations on the hydrocyclone's separation performance. A mixture model was used to model the multiphase flows, while the Reynolds stress model (RSM) modeled the turbulence in the inner field of the dynamic hydrocyclone. After a numerical investigation, it is found that when the flow rate at the inlet was below a certain value, favorable separation efficiency was obtained with some fluctuations that most likely resulted from the influence of the wall at the high rotary speed. When the flow rate at the inlet was too large, the separation efficiency would dramatically decrease. When the inlet concentration was below a certain range, it would have little influence over the separation efficiency; however, when it became too large, the separation efficiency would rapidly decline. The simulation results agreed with the theoretical results.

In this paper, a novel algorithm is proposed for balancing water looped network in steady state through a fully automated general framework of hydraulic networks regardless of their topological complexity. The model is developed by combining the following two steps, firstly a set of independent loops are identified based on a graph theoretical analysis in a looped network. Further the second step is devoted to the equilibrium process by determining the flow rate distribution within the network ducts and the pressure in the delivery nodes. The above such equilibrium process gives rise to a system of non linear algebraic equations which are solved numerically using both Hardy Cross (HC) and Newton Raphson (NR) methods. In HC method, the flow correction term is modified and a generalized expression is given to consider various possibilities of independent loops selection. Some real networks topologies that were commonly used as benchmarks, for testing various independent loops selection algorithms, are taken as case studies to apply the general automatic framework for hydraulic network analysis. Such network analysis enhances proving the applicability as well as the effectiveness of the proposed approach. Also, during the equilibrium procedure, it is proved that NR method is capable of producing accurate results and it converges more rapidly comparing to the widely used HC method. Moreover, it is demonstrated that NR’s iterative process, contrary to HC’s one, converges to reliable results even with a choice of random initial flow rates which makes a NR algorithm quite simple to implement without affecting the accuracy of the results.