Improved desalination performance of flow-electrode capacitive deionisation by a novel drop-shape channel

As an emerging desalination technology, flow-electrode capacitive deionisation (FCDI) has the advantages of theoretically infinite adsorption capacity and applicability to high-concentration brine. However, during the operation of FCDI, the flow electrode in the S-shape channel is prone to sedimentation and clogging the channel. This undesirable phenomenon brings low efficiency and security issues. Therefore, a drop-shape channel was designed for FCDI to improve the flow regime of the flow electrode. The flow simulation of the drop-shape channel was performed to select the appropriate geometry to avoid the formation of the vortex and low-velocity region. The simulation results showed that the streamlined design of the drop-shape channel has insignificant velocity gradients. It significantly reduces the low-velocity region and improves the phenomenon of particle sedimentation. The desalination performance with varieties of electrode flow rate, AC content, and voltage was used to investigate the advantage between S-shape and drop-shape channels. It was found that under the conditions of low flow rate, high AC content, and high voltage, the drop-shape channel FCDI system could still obtain better ASRR and CE.

Intrinsic dissolution rate modeling for the pharmacopoeia apparatus rotating disk compared to flow channel method

For a solid understanding of drug characteristics, in vitro measurement of the intrinsic dissolution rate is important. Hydrodynamics are often emphasized as the decisive parameter influencing the dissolution. In this study, experiments and computational fluid dynamic (CFD) simulations showed that the mixing behavior in the rotating disc apparatus causes an inhomogeneous flow field and a systematic error in the calculation of the intrinsic dissolution rate. This error is affected by both the experimental time and the velocity. Due to the rotational movement around the tablet center, commonly utilized in pharmacopeia methods, a broad variance is present with regard to the impact of fluid velocity on individual particles of the specimen surface. As this is significantly reduced in the case of uniform overflow, the flow channel is recommended for investigating the dissolution behavior. It is shown that rotating disc measurements can be compared with flow channel measurements after adjusting the measured data for the rotating disc based on a proposed, representative Reynolds number and a suggested apparatus-dependent correction factor. Additionally, modeling the apparatus-independent intrinsic dissolution rate for different temperatures in the rotating disc apparatus is possible using the adapted Levich's equation.

Mechanisms of Gravitational Influence on Weld Pool Behavior and Weld Bead Performance in Variable Polarity Plasma Arc Welding across Different Welding Position

This article comprehensively explores the cross-scale effects of gravity on macroscopic flow formation and weld bead formation in variable polarity plasma arc welding. Gravity-induced changes in welding direction were achieved through welding at different spatial positions. The properties of the weld bead were investigated at various spatial locations. Additionally, an elemental tracing technique was employed to study the internal flow behavior of molten metal. In the flat welding position, there is an observable trend of increasing grain size in the welded bead, accompanied by a significant expansion of the coarse grain zone. Consequently, the properties of the weld bead in the flat position are inferior to those achieved in the vertical welding position. This phenomenon can be attributed to the accumulation of molten metal at the exit side of the keyhole, resulting in temperature accumulation. Research indicates that the internal flow within the weld pool plays a critical role in causing this phenomenon. The study's findings reveal the presence of two distinct vortex flow patterns within the weld pool: one aligned with the welding direction and the other directed towards the interior of the weld pool. Particularly noteworthy is the substantial expansion of the flow channel area in the flat welding position, which significantly amplifies the impact of internal flow. This enhanced flow intensity inevitably leads to the increased buildup of molten metal at the keyhole exit side. These studies lay the groundwork for achieving high-quality and controllable spatial-position welding.

Intelligent Design Optimization System for Additively Manufactured Flow Channels Based on Fluid-Structure Interaction

Based on expert system theory and fluid–structure interaction (FSI), this paper suggests an intelligent design optimization system to derive the optimal shape of both the fluid and solid domain of flow channels. A parametric modeling scheme of flow channels is developed by design for additive manufacturing (DfAM). By changing design parameters, a series of flow channel models can be obtained. According to the design characteristics, the system can intelligently allocate suitable computational models to compute the flow field of a specific model. The pressure-based normal stress is abstracted from the results and transmitted to the solid region by the fluid–structure (FS) interface to analyze the strength of the structure. The design space is obtained by investigating the simulation results with the metamodeling method, which is further applied for pursuing design objectives under constraints. Finally, the improved design is derived by gradient-based optimization. This system can improve the accuracy of the FSI simulation and the efficiency of the optimization process. The design optimization of a flow channel in a simplified hydraulic manifold is applied as the case study to validate the feasibility of the proposed system.

Thermal Analysis on Active Heat Dissipation Design with Embedded Flow Channels for Flexible Electronic Devices

Heat generation is a major issue in all electronics, as heat reduces product life, reliability, and performance, especially in flexible electronics with low thermal-conductivity polymeric substrates. In this sense, the active heat dissipation design with flow channels holds great promise. Here, a theoretical model, validated by finite element analysis and experiments, based on the method of the separation of variables, is developed to study the thermal behavior of the active heat dissipation design with an embedded flow channel. The influences of temperature and flow velocity of the fluid on heat dissipation performance were systematically investigated. The influence of channel spacing on heat dissipation performance was also studied by finite element analysis. The study shows that performance can be improved by decreasing the fluid temperature or increasing the flow velocity and channel density. These results can help guide the design of active heat dissipation with embedded flow channels to reduce adverse effects due to excessive heating, thus enhancing the performance and longevity of electronic products.

Determination of Inherent Dissolution Performance of Drug Substances

The dissolution behavior of novel active pharmaceutical ingredients (API) is a crucial parameter in drug formulation since it frequently affects the drug release. Generally, a distinction is made between surface-reaction- and diffusion-controlled drug release. Therefore, dissolution studies such as the intrinsic dissolution test defined in the pharmacopeia have been performed for many years. In order to overcome the disadvantages of the common intrinsic dissolution test, a new experimental setup was developed within this study. Specifically, a flow channel was designed and tested for measuring the mass transfer from a flat, solid surface dissolving into a fluid flowing over the surface with well-defined flow conditions. A mathematical model was developed that distinguishes between surface-reaction- and diffusion-limited drug release based on experimental data. Three different drugs-benzocaine, theophylline and griseofulvin-were used to investigate the mass flux during dissolution due to surface reaction, diffusion and convection kinetics. This new technique shows potential to be a valuable tool for the identification of formulation strategies.

Visualizing the macroscale spatial distributions of biofilms in complex flow channels using industrial computed tomography

The presence of biofilms in enclosed pipelines can lead to numerous deleterious issues. To date, it has been difficult to use optical imaging techniques to monitor the macroscale spatial distributions of biofilms. To address this concern, a combination of industrial computed tomography (ICT) and a contrast agent was explored to noninvasively visualize biofilms in three types of drip irrigation emitters. The results showed that ICT successfully observed and quantified the macroscale spatial distributions of biofilms. The complex hydrodynamic characteristics in the emitter channels affected the local distributions of biofilms. Biofilms were mainly attached to the lateral and medial faces and biomass decreased along the flow directions. Based on the distributions of biofilms, some emitter structural design defects were further diagnosed. Applying ICT in combination with the contrast agent could potentially provide a visual and effective way to reveal the formation mechanisms of biofilms and to optimize flow channel structures to avoid biofilm accumulations.

The investigation of systolic and diastolic leaflet kinematics of bioprostheses with a new in-vitro test method

OBJECTIVES

We aimed to investigate leaflet kinematics of bioprostheses with a novel high-speed imaging method.

MATERIAL AND METHODS

High-speed-imaging (1000 Hz) was used to evaluate leaflet kinematics of the Carpentier-Edwards Perimount Magna (PM) and Magna Ease (PME) aortic bioprostheses. Both prostheses (diameter 23 mm) were placed inside a model aorta under pulsatile flow conditions. Frequencies (F) and different stroke volumes (S) were simulated. Maximum aortic valve area (AVA), total ejection time (TET), rapid valve opening time (RVOT) and rapid valve closing time (RVCT) as well as opening (OS) and closing (CS) speeds were evaluated.

RESULTS

Both bioprostheses showed different results dependent on flow conditions. The test setup was capable of identifying small AVA-differences between both valves (235 vs. 202 mm², F60/S60; 272 vs. 207 mm²; F70/S80), as well as differences in OS and CS (2.36 vs. 1.62 mm²/ms; 2.97 vs. 2.44 mm²/ms, F80/S60). TET was comparable (638 vs. 645 ms F60/S60; 341 vs. 343 ms, F90/S60), while results for RVOT and RVCT were equal, and dependent on frequency and stroke volume.

CONCLUSIONS

The novel evaluation method is sensitive to detect differences between valves, although differences were found to be small. PM has a larger visible AVA associated with higher opening and closing speeds in contrast to PME.

Experimental and computational analysis of a novel flow channel to assess the adhesion strength of sessile marine organisms

Bioadhesives produced by marine macroalgae represent a potential source of inspiration for the development of water-resistant adhesives. Assessing their adhesion strength, however, remains difficult owing to low volumes of adhesive material produced, low solubility and rapid curing time. These difficulties can be circumvented by testing the adhesion strength of macroalgae propagules attached to a substrate. In this paper, we present a simple, novel flow channel used to test the adhesion strength of the germlings of the fucalean alga Hormosira banksii to four substrates of biomedical relevance (PMMA, agar, gelatin and gelatin + lipid). The adhesion strength of H. banksii germlings was found to increase in a time-dependent manner, with minimal adhesion success after a settlement period of 6 h and maximum adhesion strength achieved 24 h after initial settlement. Adhesion success increased most dramatically between 6 and 12 h settlement time, while no additional increase in adhesion strength was recorded for settlement times over 24 h. No significant difference in adhesion strength to the various substrates was observed. Computational fluid dynamics (CFD) was used to estimate the influence of fluid velocity and germling density on drag force acting on the settled organisms. CFD modelling showed that, on average, the drag force decreased with increasing germling number, suggesting that germlings would benefit from gregarious settlement behaviour. Collectively, our results contribute to a better understanding of the mechanisms allowing benthic marine organisms to thrive in hydrodynamically stressful environments and provide useful insights for further investigations.