Flow rate variations in microfluidic circuits with free surfaces

The primary objective of this study is to develop a simultaneous approach for the synthesis of flexible heat exchanger networks (HENs) with non-isothermal mixing assumptions. The HENs synthesis procedure presented in this study took into consideration quantified uncertainties in inlet temperatures and flow rates with an unpredictable time of shift. The proposed multi-period MINLP model was used to generate a HEN with optimized heat exchanger areas and total annualized costs attributed to utility duties. A framework for generating the flexible HEN over a specified range of variations in flow rates and stream temperature was proposed in this study. The framework was based on a two-stage strategy; a HEN design stage was first performed before the testing stage where the energy-saving potential of the synthesized HEN was established. The effectiveness of the proposed approach was tested for energy minimization using a case study in literature with variation in inlet temperature and flow rate. It was observed that the inclusion of non-isothermal parameters in the non-linear model resulted in a HEN that optimally works under fluctuating conditions without losing stream temperature targets while maintaining economically-optimal energy integration.

Integrated analysis of pressure response using pressure-rate convolution and deconvolution techniques for varied flow rate production in fractured formations

• Powder delivery systems for directed energy deposition processes can exhibit oscillatory variation in mass flow rates, matching the characteristic speed of individual hopper components. • Flow rate variation can be observed at the nozzle exit, both by offline weight measurement and by imaging the powder flow. • Flow rate variation is observed to have a measurable effect on melt track height, with the potential to cause build quality issues. • Melt pool imaging shows a correlating pattern, indicating that flow rate variation can affect melt pool image brightness, and may influence the behaviour of image based control approaches. Powder flow rate is a key parameter in Directed Energy Deposition (DED) processes. During a typical build, if powder flow rate is reduced for just 1 second, 30 mm of melt track is affected. Consequently, even a small variation in powder flow rate can have significant implications on build quality. In this work, the powder flow stability for different types of 316 L steel powders was quantified using a combination of methodologies including offline weight measurements, flow imaging, in-situ build data and coaxial melt pool imaging. Flow rate oscillation was observed, correlated with the periodicity of powder hopper turntable rotation, at sufficient magnitude to cause build quality effects and be identifiable in coaxial melt pool imaging. The implications of flow rate variation on the use of melt pool imaging for closed-loop control are discussed.

An investigation on free water surface wetland, which has an area of 0.23 ha and is employed to control the non-point source pollution from a watershed of 7.4 ha, was carried out to examine how the WQvr (the ratio of stormwater inflow volume to water quality volume (WQv)) affects the wetland treatment performance. As stormwater went through the wetland, TSS (total suspended solids), TCOD (total chemical oxygen demand), TN (total nitrogen) and TP (total phosphorus) were reduced by 85%, 57%, 6% and 68%, on average, respectively. Increase in the WQvr resulted in a decrease in the reduction efficiencies of TSS, TCOD and TP, but a slight increase in TN removal. WQv was identified as a useful parameter for the design of stormwater wetlands, as this volumetric design approach overcomes the variation in flow rate and pollutant concentrations with respect to time and rainfall conditions. However, the design goal of 80% TSS reduction was not accomplished as inflow water volume equal to designed WQv. On the other hand, it was found that TCOD and TP reduction could also be considered as wetland design goals together with TSS. However, TN reduction did not show any significant relationship with the WQv.

Study of a modified non-contact Hall sensor-based flow transducer using centrifugal and momentum force principle

Experimental and numerical investigation of the temperature and flow rate variation on an industrial high-temperature thermocline storage for recovering waste heat

All theoretical studies conducted in modern hydrodynamics are based on a system of Eulerian equations, a continuity equation, and a characteristic equation [1]. In the area of hydraulics that is concerned with a one-dimensional motion, the basis for all theoretical investigations is a system of three equations: (i) a Bernoulli equation, which is a particular solution of the Eulerian system, (ii) a flow equation, which is an analog of the continuity equation, and (iii) a characteristic equation. These equations are used to study the motion of a fluid at a constant flow rate. For the case of motion of a fluid at a variable flow rate, these equations must be modified and augmented with new equations to make the system complete. Most studies were mainly concerned with formulating a “basic equation” for the motion of a fluid at a variable flow rate. For the first time, the problem of constructing a general complete system of equations for the motion of a fluid at a variable flow rate for unilateral division of the flow was brought to a logical conclusion by Kiselev [2]. To follow suit, it was our goal in this study to set up a general complete system of equations for the motion of a fluid at a variable flow rate for bilateral division of the flow. General equations for the fluid motion at a variable flow rate for bilateral flow offtake. We consider a model for constructing general equations. From the main stream flowing through a constraint space (a river, a channel, etc.), part of the fluid is uniformly and simultaneously diverted. Within an infinitesimal time interval At, the masses m lo and m ro moving with the velocities u lo and u ro are instantaneously diverted from the main stream of mass m moving with the velocity u (here the subscripts “lo” and “ro” denote the left-side offtake and right-side offtake, respectively). At the instant of diversion, the remaining mass m – m lo – m ro has the velocity u + Au = u. The lapse of time from At to dt is is a continuous process involving the change in mass. One can assume that at any instant of the unit time interval within the volume of fluid AW, the system in question can be partitioned into two parts: one is the mass of the main stream m, and the other is the diverted masses m lo and m ro . The space of volume AW is filled with fluid masses of the main and diverted flows. The fluid motion is assumed to be uninter

Criteria for choosing an intravenous infusion line intended for multidrug infusion in anaesthesia and intensive care units

Continued population growth demands a significant increase in agricultural production to ensure food security. However, agricultural output is limited by environmental crises and the negative impacts of open-field farm practices. As an alternative, vertical farming techniques, such as aeroponics, can be utilized to optimize the use of resources. However, the uneven size and distribution of spray droplets in aeroponics, issues that affect root development and nutrient delivery, continue to be problematic in spray performance analysis. In aeroponics, nutrient solutions are delivered to plant roots through pressurized nozzles, and the effectiveness of this delivery depends on the spray characteristics. Variations in flow rates directly affect droplet size, density, and coverage, which in turn influence nutrient uptake and crop growth. In this study, the flow rate was adjusted (3, 4.5, and 6 L/min) to quantitatively analyze spray performance using water-sensitive paper (WSP) as a deposit collector via a quick assessment method. Subsequently, image-processing techniques such as threshold segmentation and morphological operations were applied to isolate individual spray droplets on the WSP images. This technique enabled the quantification of the droplet’s coverage area, size, density, and uniformity to effectively evaluate spray performance. One-way ANOVA indicated that all the spray parameters varied significantly with respect to the flow rate (p < 0.05): For example, the average diameters of the droplets increased from 0.73 mm at 3 L/min to 1.29 mm at 6 L/min. The droplets’ densities decreased from 85.53 drops/cm2 to 30.00 drops/cm2 across the same flow range. The average uniformity index improved from 30.53 to 15.95 as the flow rate increased. These results indicate that the application of WSP is an effective and scalable approach for analyzing spray performance in aeroponics, as WSP can be rapidly digitized with simple tools, such as a cell phone camera, avoiding the limitations of flatbed scanners or specialized imaging systems.

IntroductionIntraosseous infusion is recommended if peripheral venous access fails for cardiopulmonary resuscitation or other medical emergencies. The aim of this study, using body donors, was to compare a semi-automatic (EZ-IO®) device at two insertion sites and a sternal intraosseous infusion device (FASTR™).MethodsTwenty-seven medical students being inexperienced first-time users were randomized into three groups using EZ-IO and FASTR. The following data were evaluated: attempts required for successful placement, insertion time and flow rates with and without external pressure to the infusion.ResultsThe first-pass insertion success of the EZ-IO tibia, EZ-IO humerus and FASTR was 91%, 77%, and 95%, respectively. Insertion times (MW±SD) did not show significant differences with 17±7 (EZ-IO tibia) vs. 29±42 (EZ-IO humerus) vs. 33±21 (FASTR), respectively. One-minute flow rates using external pressures between 0 mmHg and 300 mmHg ranged between 27±5 to 69±54 ml/min (EZ-IO tibia), 16±3 to 60±44 ml/min (EZ-IO humerus) and 53±2 to 112±47 ml/min (FASTR), respectively. Concerning pressure-related increases in flow rates, negligible correlations were found for the EZ-IO tibia in all time frames (c = 0.107–0.366; p≤0.013), moderate positive correlations were found for the EZ-IO humerus after 5 minutes (c = 0.489; p = 0.021) and strong positive correlations were found for the FASTR in all time frames (c = 0.63–0.80; p≤0.007). Post-hoc statistical power was 0.62 with the given sample size.ConclusionsThe experiments with first-time users applying EZ-IO and FASTR in body donors indicate that both devices may be effective intraosseous infusion devices, likely suitable for fluid resuscitation using a pressure bag. Variations in flow rate may limit their reliability. Larger sample sizes will prospectively be required to substantiate our findings.

BackgroundMultiple protocols for acquiring intracranial four-dimensional flow magnetic resonance (4D Flow MR) data and post-processing software employed to obtain hemodynamic parameters are available. However, insufficient validation exists to quantify the difference in measurements. This study aims to perform a comprehensive cross-comparison analysis of quantitative results from three major vendors and three post-processing software platforms.MethodsIntracranial 4D Flow MR was conducted on 20 healthy volunteers using three different 3.0T MRI scanners. For each subject, nine major intracranial arteries (a total of 180 arteries) were analyzed using three post-processing software platforms: CVI42, MASS, and TS FLOW. Key hemodynamic parameters—including flow rate, maximum velocity (Vmax), average velocity (Vavg), and delineated vessel area—was extracted. The study compared results across different vendors and software, and further assessed both intra-observer and inter-observer consistency.ResultsRegardless of the post-processing software used, no significant differences were observed in the flow rate across different scanners (p > 0.05), with ICC = 0.700-0.919 and equivalence testing results indicate the interchangeable use of all three scanners. For flow rate and Vmax, the MASS and CVI42 software were equivalent. For Vavg, TS FLOW and CVI42 were tested equivalent. For vessel area, various agreement was shown across software (ICC = 0.083–0.577). Additionally, the TS FLOW software exhibited repeatability and reproducibility (intra-observer ICC = 0.724–0.998; inter-observer ICC = 0.590–0.981).ConclusionsScanning protocols by different vendors appear to result in smaller variations in flow rate compared to using different post-processing software methods. It is recommended to employ single post-processing software or conduct software calibration when using multiple software platforms to ensure consistency in multi-center clinical studies.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12880-025-02039-8.

Impact of material properties and process variables on the residence time distribution in twin screw feeding equipment

An intensive study of water, overburden, and coal chemistry was conducted at a large surface mine in Ohio from May 1976 through July 1977. Sampling sites were chosen to include the final mine effluent at the outflow of a large settling pond and chemically-treated drainage from a coal storage pile. Samples were collected semimonthly and analyzed for total dissolved solids, total suspended solids, alkalinity, acidity, sulfate, chloride, and 16 metals. Field measurements included pH, flow rate, dissolved oxygen, and specific conductance. The final effluent, where sampled, generally complied with Office of Surface Mining reclamation standards for pH, iron, and total suspended solids. Comparison of the final effluent with water quality of an unnamed tributary above the mine suggested that elevated values for specific conductance, total dissolved solids, sulfate, calcium, magnesium, manganese, and zinc were attributable to the mine operation. In general, there were observable seasonal variations in flow rates that correlated positively to suspended solids concentrations and negatively to concentrations of dissolved constituents in the final effluent. Drainage from the coal storage pile contained elevated levels of acidity and dissolved metals which were not reduced significantly by the soda ash treatment. The storage pile drainage was diluted, however, by large volumes of alkaline water in the settling pond. Analysis of overburden and coal indicated that the major impact of mine drainage was pyrite oxidation and hydrolysis in the Middle Kittanning Coal and in the Lower Freeport Shale overlying the coal. However, the presence of a calcite-cemented section in the Upper Freeport Sandstone contributed substantial self-neutralizing capacity to the overburden section, resulting in generally alkaline drainage at this site.

A pressure builds up test was performed in a dry gas exploration well. According to geological data indicated that there are two intersecting faults near the well. The analysis result provided not only information of the reservoir characteristics such as average reservoir pressure, permeability, and formation damage, but also confirmation of the presence of those two intersecting faults. In this study, a reservoir simulator was used to model pressure build up test of a well located near two intersecting faults. The effect of several parameters namely the distance between well to the faults, flow rate, and reservoir pressure, on bottom hole pressure behaviour was observed. The simulation results showed that the effect of variation of the distance between well and faults as well as that of reservoir pressure on estimation of permeability and skin factor is not significant. While, the variation of flow rate may result in a significant deviation. If a constant flow rate cannot be maintained during flowing period of the pressure build up test.

An Internal Model based Sliding Mode Controller is proposed to compensate the slow response due to thermal sensor for variations in flow rate of gas. The Mass flow system is approximated to a third order dynamic model. Simulation is performed for Control based on Estimated flow rate using Proportional Integral Controller and Control based on Sensed flow rate using RST and Internal Model Sliding Mode Controller. Performance of the proposed Internal Model Sliding Mode Controller is compared with Proportional Integral and RST controllers using the performance measure RMSE (Root Mean Square Error). The proposed Internal model Sliding Mode controller yields excellent robustness and the simulation results show the feasibility of the proposed scheme.