Dependence Of Flow Rate Research Articles

Using thin film freezing to minimize excipients in inhalable tacrolimus dry powder formulations.

We investigated the feasibility of preparing high-potency tacrolimus dry powder for inhalation using thin film freezing (TFF). We found that using ultra-rapid freezing can increase drug loading up to 95% while maintaining good aerosol performance. Drug loading affected the specific surface area and moisture sorption of TFF formulations, but it did not affect the chemical stability, physical stability, and dissolution of tacrolimus. Tacrolimus remained amorphous after storage at 40°C/75% RH, and 25°C/60% RH for up to 6months. Lactose functioned as a bulking agent, and it had little to no effect as a stabilizer for amorphous tacrolimus due to a lack of interaction between the drug and excipient. Additionally, the aerosol performance of TFF tacrolimus/lactose (95/5) did not significantly change after six months of storage at 25°C/60% RH. For processing parameters, the solids content and the processing temperature did not affect the aerosol performance of tacrolimus. Furthermore, both low- and high-resistance RS01 showed optimal and consistent aerosol performance over the 1-4kPa pressure drop range. In conclusion, TFF is a suitable technology for producing inhalable powder that contain high drug loading and have less flow rate dependence.

Lattice Boltzmann simulations capture the multiscale physics of soft flowing crystals.

The study of the underlying physics of soft flowing materials depends heavily on numerical simulations, due to the complex structure of the governing equations reflecting the competition of concurrent mechanisms acting at widely disparate scales in space and time. A full-scale computational modelling remains a formidable challenge since it amounts to simultaneously handling six or more spatial decades in space and twice as many in time. Coarse-grained methods often provide a viable strategy to significantly mitigate this issue, through the implementation of mesoscale supramolecular forces designed to capture the essential physics at a fraction of the computational cost of a full-detail description. Here, we review some recent advances in the design of a lattice Boltzmann mesoscale approach for soft flowing materials, inclusive of near-contact interactions (NCIs) between dynamic interfaces, as they occur in high packing-fraction soft flowing crystals. The method proves capable of capturing several aspects of the rheology of soft flowing crystals, namely, (i) a 3/2 power-law dependence of the dispersed phase flow rate on the applied pressure gradient, (ii) the structural transition between an ex-two and ex-one (bamboo) configurations with the associated drop of the flow rate, (iii) the onset of interfacial waves once NCI is sufficiently intense. This article is part of the theme issue 'Fluid dynamics, soft matter and complex systems: recent results and new methods'.

Investigating the Additional Components of Uncertainty of Measurment Result of Unsteady Flow

The additional components of uncertainty of measurement result of unsteady flow by means of pressure differential flowmeter are investigated in the article. In particular, the authors considered in detail the technique for estimating the additional component of uncertainty, caused by the nonlinearity of the flowrate dependence on the pressure drop on the standard primary device, as well as the additional component, which is related to the absence of the inertial term in the root expression of the quasi-steady flow equation. On the example of four differential pressure signals that reproduce the pulsating and unsteady flow modes of the fluid, the estimating the named components is carried out and the dependence of these components of uncertainty on the basic characteristics of the differential pressure signal (root mean square amplitude of pulsations and the maximum relative deviation) is demonstrated. It is shown that the increase of these signal characteristics leads to an increase in the corresponding components of the uncertainty and, consequently, in the resulting additional uncertainty of the measured value of flowrate. Particularly, for the investigated pressure drop signals for which the root mean square amplitude does not exceed 20% of the mean pressure drop, the resulting additional uncertainty of the measured flowrate reaches 0.5%. Since the additional uncertainty caused by unsteady flow is systematic and has a positive sign, it is possible to determine the correction coefficient based on this additional uncertainty and to correct the measured value of the flowrate by considering the correction factor in the flow equation. However, the authors propose to correct the measured value of the flowrate only if it is impossible to identify the causes of unsteady flow and to eliminate their impact on the flowrate.

HYDRAULIC PROPERTIES OF SAND SLURRY FLOW IN A PIPE

The sand slurry flow in a cylindrical pipe is investigated using the Ostwald de Waele model. The dependence of the fluid flow rate on the pressure drop is determined, dependencies for the radial distribution of velocity and effective viscosity of flow are obtained. It is shown that the distribution of effective viscosity is characterized by a monotonic increase as it approaches the pipe walls. As the consistency increases, the mechanical energy dissipation of the flow also increases leading to an increase in hydraulic resistance. During the flow of dilatant media with the low nonlinearity index, the hydraulic resistance decreases with increasing pressure drop. When this index is 2, the hydraulic resistance does not depend on the pressure drop and is determined only by the liquid properties and the channel size. At highe values of the nonlinearity index, the increased pressure drop leads to an increase in hydraulic resistance. Keywords

Growth and Field Emission of Single‐Crystalline Hafnium Carbide Nanowires

<100>‐oriented hafnium carbide (HfC) nanowires are synthesized on the graphite substrate by chemical vapor deposition. The dependence of temperature, HfCl4content, and flow rate of CH4gas on the morphology of nanowires is investigated herein. The results indicate that the HfC nanowire often kinks to another growth direction at a high HfCl4content or a low temperature due to the destabilization of the catalyst droplet induced by either a faster growth rate or slower thermal activation. Reduced nanowire density and length are observed at the sample synthesized at a lower CH4flow rate. Based on the experimental results, high‐crystallinity nanowires with high aspect ratios and high densities are prepared at a lower HfCl4content, higher temperature, and high CH4flow rate. The field‐emission properties of a single HfC nanowire are also characterized by assembling a single HfC nanowire emitter. An extremely high field enhancement factor of 5.57 × 106 m−1is obtained herein.

The Effect of Physical Properties of Fluids on the Process of Purifying the Main Gas Pipeline from Liquid Pollutants

The article deals with modern technical methods of improving the efficiency of gas pipelines cleaning. The most effective method of improving the efficiency of a gas pipeline is its periodical cleaning with mechanical treating units. In practice, a large number of cleaning pistons of various technological designs are used. Regardless of the design, none of them can completely remove the fluid accumulations. The reason for the decrease in efficiency is the presence of fluid in the cavity of the pipeline. The fluid can be of two types – high-viscosity resinous deposits and low-viscosity liquid deposits. When moving, they perform the role of local resistance. The type of the main gas pipeline purification process is largely determined by the physical properties of the fluid which is being displaced. The authors specify the functional dependence of the velocity distribution in the pipe cross-section while displacing the Newtonian fluid, as well as the value of the initial pressure of the liquid phase on the cleaning piston. The interaction of a purifying device with fluid accumulations having different physical properties is investigated. The authors develop the algorithm of calculating the volume of the flows over a moving boundary into a back-piston space, in relation to their velocity. The dependence of the volume of fluid flows caused by hydraulic shock for Newtonian and non-Newtonian fluids is composed. Based on the calculations, the authors plot the graphical dependence of the correction coefficient on the ratio of dynamic viscosity to the degree of consistency, as well as the dependence of the total flow rate on the speed of movement of the cleaning unit. The formula for calculating the correction coefficient is obtained. The article presents the results of calculating the value of the correction coefficient which takes into account the rheological properties of the fluid. In relation to the properties and rheology of the non-Newtonian fluid, the authors determine the optimal velocity of a treating unit.

Performance Analysis of Solar Desalination System for Improved Productivity by using Waste Heat of Household Chimney

This work deals with the analysis of the proposed innovative humidification-dehumidification (HD) desalination unit in which waste hot air of kitchen chimney has been used for heating brackish water. The proposed system is configured with solar air heater also, thus both heated air and heated water has been used to improve the water yield of desalination unit compared to conventional system. Mathematical modeling of propose unit based on energy balance of flat plate air heater, humidifier, dehumidifier and brackish water tank has been used to evaluate the effect of operating condition. Potable water yield found to increase (with highest productivity of 6.5 kg/day) when mass flow rate of process air increases from 0.6 kg/min to 3 kg/min. Strong dependency of water mass flow rate has also been found as productivity increases (with maximum value of 6.7 kg/day and 7.5 kg/day) by increasing the mass flow rate of brackish water in humidifier and cold water in dehumidifier respectively. The higher initial temperature of brackish water also found beneficial as it increases productivity. Finally, the thermal performance of desalination unit has been evaluated in terms of Gain in Output Ratio and comparison has been made with conventional system. The higher GOR of the proposed system ensures the better utilization of thermal energy in potable water production.

Morphology of Shear-Induced Colloidal Aggregates in Porous Media: Consequences for Transport, Deposition, and Re-entrainment.

Colloid deposition in granular media is relevant to numerous environmental problems. Classic filtration models assume a homogeneous pore space and largely ignore colloid aggregation. However, substantial evidence exists on the ubiquity of aggregation within porous media, suggesting that deposition is enhanced by it. This work studies the deposition process in relation to aggregate size and structure. We demonstrate that aggregation is induced at typical groundwater velocities by comparing the repulsive DLVO force between particle pairs to the hydrodynamic shear force opposing it. Column experiments imaged with high-resolution X-ray computed tomography are used to measure aggregate structure and describe their morphology probability distribution and spatial distribution. Aggregate volume and surface area are found to be power-law distributed, while Feret diameter is exponentially distributed with some flow rate dependencies caused by erosion and restructuring by the fluid shear. Furthermore, size and shape of aggregates are heterogeneous in depth, where a small number of large aggregates control the concentration versus depth profile shape. The range of aggregate fractal dimensions found (2.22-2.42) implies a high potential for restructuring or breaking during transport. Shear-induced aggregation is not currently considered in macroscopic models for particle filtration, yet is critical to consider in the processes that control deposition.

Experimental study of dependence on humidity and flow rate for a modified flowthrough radon source

Flow-through radon sources were widely utilized in the calibration of radon equipment and radon studies. In this paper a broken 266Ra source which was made in 1983 by the Pylon Inc. was modified to a new flow-through radon source. The humidity and flow rate dependence of the new flow-through radon source was studied to get a reliable large-scale radon source. The results show that the equilibrium radon concentration of the new flow-through radon source is rather sensitive to flow rate, especially below 1 L/min of flow rate, which sharply decreases with the flow rate rising, however, it increases with the relative humidity rising. The radon emanation coefficient does not depend on the flow rate of 0.6–2.57 L/min. However, the radon emanation coefficient increases up exponentially with the rising of the air humidity, it increases up slowly at the relative humidity of 4–50%, but it does fast at the relative humidity of 60–85%. The humidity dependence of flow-through radon sources is more obvious than diffusion radon sources because a dominative radon transport mode from the solid source material into the air is seepage rather than diffusion.

Viscoplastic fluid flow modeling with the “solidification” effect in the straight channel of the annular cross section

On the basis of the viscoplastic fluid rheological model, which takes into account the manifestation of the “solidification” effect, a flow has been simulated in the annular cross section channel. It is shown that, depending on the pressure drop level, three different flow patterns are possible. For each pattern, the expressions that determine the fluid velocity distribution in the channel’s cross section have been obtained. It is shown that the dependence of the volume fluid flow rate on the pressure drop is not monotonic. Moreover, the increase in the pressure drop critical level ultimately leads to the flow rate decrease due to the narrowing of the channel’s passage section, which is caused by the formation of the “solidified” liquid layers.

LIQUID ASPHALT BINDERS IN CYLINDRICAL TUBE IN TERMS OF THE OSTWALD-DE WAELE MODEL

The liquid asphalt binder in a cylindrical tube is described in terms of the Ostwald-de Waele model. The dependence of the liquid flow rate on the pressure drop; dependencies are obtained for radial distribution of the flow rate and viscosity. The medium structuring, which is most noticeable at low values of nonlinearity leads to the almost uniform profile of the core flow rate, which is typical to the plastic flow. The liquid pseudoplastic media with a law nonlinearity is characterized by the presence of a highly viscous core and a narrow region of the near-wall flow with low values of effective viscosity. With increasing in medium consistency, the average viscosity increases. This effect is most pronounced for flow motions at a small pressure drop. For low values of the pressure drop, the non-Newtonian properties of the medium lead to a significant hydraulic resistance due to the presence of the inner structure. With increasing pressure drop, hydraulic resistance decreases due to the medium destruction.

OPERATIONAL FEATURES AND METHODS FOR DETERMINING THE OPTIMAL OPERATION PARAMETERS IN FRACTURED RESERVOIRS WITH A GAS CAP: OIL RIMS OF ORENBURG OGCF CASE STUDY

The paper deals with the features of well operation at the Eastern part of Orenburg oil and gas condensate field (OGCF). We propose a complex approach to determining the parameters of the fractured formation: based on the mathematical model of Warren–Root fracture reservoir, we find the dependence of the well flow rate on time and parameters of fracture under conditions of maintaining constant bottomhole pressure. Next stage is an extrapolation of this problem for the case of arbitrary dynamics of flow rates and pressures based on the deconvolution theory. The search of parameters of double fracture formation is carried out by their variation in the corridor of admissible values in order to minimize the deviation of the calculated flow rate relative to the true one. To identify possible reasons for the decline in well productivity with a decrease in bottomhole pressure, numerical experiments were performed on synthetic hydrodynamic models to determine the main influencing factors that can lead to an observed decrease in well productivity with increasing depression. Based on the information received, multivariate calculations of sector models of the EP OGCF were carried out in order to determine the optimal operating parameters to maximize oil production or minimize specific operating costs, taking into account the identified complicating factors.

К ВОПРОСУ РАСЧЕТА И ИСПОЛЬЗОВАНИЯ ГИДРОМЕТРИЧЕСКОГО ЛОТКА ПАРШАЛЛА С СОВРЕМЕННЫМИ ПРИБОРАМИ УЧЕТА ВОДЫ

Purpose: the use of a flow-metering flume and a modern metering device for water metering in an open canal with a flow rate of up to 1.5 cubic meters per second with the subsequent prospect of automating the measurement process. Materials and methods: the main function of the hydrometric structure – giving the fluid flow a given regime and pattern within a limited channel is theoretically used in the article. With the help of a hydrometric structure (Parshall flume) using the well-known “velocity-area” method, it is possible to determine the functional dependence of the water flow rate on one measured parameter, in this case on the level. With the use of modern sensors or devices for metering this parameter, it is easy in the future to automate the process of its metering, registration and transmission over a distance. Results and Discussion: the calculation of the maximum flow rate of the chute according to the selected empirical formula showed the correct selection and calculation of its parameters for the structure in accordance with a given maximum flow rate (up to 1.5 cubic meters per second), which does not require additional calibration of the chute during application. Conclusions: recently, more and more attention has been paid to the accuracy of used water metering in open irrigation canals with a low flow rate. With introduction of new modern devices that convert the measured parameter into the amount of measured water flow, the relevance of their use together with hydrometric devices increases. To measure water flow in an open canal, it is proposed to use Parshall flume with a modern measuring device, consisting of a submersible pressure sensor and a remote control and monitoring unit installed in a stilling well. The description of design and an example of clarifying the geometric dimensions of a flume with a measured water flow rate of up to 1.5 cubic meters per second is provided. The design diagrams of the flume and stilling well with the placement of a modern measuring device are presented.

Optimization of the process of reproducing units of mass and volume of liquid in a stream, mass and volumetric flow rates of liquid for calibration units with weighing devices

The publication presents an experimental method for estimating the minimum time interval for filling a storage tank with a working fluid with a fixed geometry of the nozzle of the flow switch of the calibration plant when playing units of mass and volume of fluid in the flow, mass and volumetric flow rates of the fluid. Experimental studies were performed in a wide range of mass flow rate 11,10–83,26 kg/s (40–300 t/h) with repeated static weighing of the working fluid. The flow switch is made with a fixed geometry of the flow part of the nozzle exit, which is typical for a large number of calibration units in use in our country with weighing devices. The graphical dependences of the mass flow rate on the time of filling the storage capacity obtained from the research results are the basis for optimizing the process of reproducing units of mass and volume of liquid in the flow, mass and volumetric flow rates of the liquid for calibration plants with weighing devices. These graphical dependencies made it possible to formulate recommendations on the reasonable choice of the minimum interval for filling the storage tank with working fluid in the studied range of mass flow rate. Optimization has been tested and can be extended to calibration units with weighing devices from various manufacturers with individual design and operating parameters.

Regime Analysis in Ranque Tubes with Circular and Square Working Channels

This study compares detailed regime maps in the case of operation using the air of two Ranque tubes with circular and square working channels with identical inlet guides and identical outlets. The degree of air expansion and the fraction of a flow rate through a cold outlet vary in ranges of 2–8 and 0.2–0.8, respectively. It is observed for both tubes that, as the degree of expansion increases, the dependences of a volumetric flow rate and a cooling ratio on the fraction of a cold flow rate become invariant. It is revealed that the cooling ratio in a circular tube is 1.5–2.0 times greater than that in a square channel, with the volumetric flow rate therein being approximately 10% lower.

Numerical simulation of conjugated heat exchange in the turbulent motion of fluid in an oil well

The mathematical model of conjugate heat exchange is proposed for the turbulent movement of reservoir oil in a vertical well section. The motion of the medium is described using a two-dimensional axisymmetric stationary formulation and boundary layer equations. The movement of the turbulent flow of reservoir oil due to reservoir energy is presented. The liquid medium is a mixture of reservoir oil with dissolved gas and formation water. The results of the numerical modeling are presented in the form of dependences of the changing flow rate, temperature, and mass fraction of paraffin deposits that occur along the full vertical extent of the well. The results obtained describe the thermobaric state of the well under the condition of conjugate heat exchange between the fluid flow and the production pipe.

Numerical simulation of air flow in short metro ventilation shafts caused by a piston effect

Protecting the infrastructure of the metro from unauthorized actions with the help of ventilation openings of the systems is one of the main security problems of this type of transport. This article discusses the problem of the dynamics of distribution of the mass flow rate of ventilation air in a two-component system “tunnel vertical ventilation shaft”, due to the piston effect of a moving train. The dependence of the mass flow rate of ventilation air passing in both directions in short ventilation shafts (up to 10 m), on the speed, location of the rolling stock and cross-sectional area of the ventilation shaft is investigated. It is shown, that at speeds of 10–20 m / s of rolling stock and sections of the ventilation shaft of more than 4 m2, the mass flow rate of air passing through the ventilation shaft must be taken into account with the mass flow rate of ventilation air in the transport tunnel for assessing the safety of the harmful aerosols. These processes can have a significant impact on the air quality of the underground infrastructure of the metro.

IMPROVING THE STEAM-ASSISTED GRAVITY DRAINAGE INTEGRAL SIMULATOR TO PREDICT THE TIME OF STEAM BREAKTHROUGH INTO THE PRODUCER

One of the main problems for Steam Assisted Gravity Drainage (SAGD) is the risk of steam breakthrough into the producer. A relevant task is to simulate SAGD to predict steam breakthrough. The existing models do not predict many technological parameters, and the integral model, developed earlier, does not consider the risk of a steam breakthrough. In this article, for the first time, an integral model is proposed in a dimensionless form, which considers risk of steam breakthrough and allows calculating all stages of SAGD. The aim of this study is to improve the previously developed SAGD model to calculate the vertical coordinate of the upper boundary of liquid phase level. This has required a system of equations based on mass and heat balances both in the chamber and in the region of liquid phases. The system of equations is represented in dimensionless form. The research methodology involves using an explicit finite-difference scheme to solve this system and to verify the model according to the data by Ya. Yang et al. The nonlinear equation included in the system is solved using Newton’s iterative method. The lowering of the upper boundary of liquid phases’ region means steam breakthrough. The results have provided the dependences of volumetric oil flow rate, the vertical coordinate of the upper boundary of the level of liquid phases and steam-oil ratio on time of process. These results are compared with the production data from the Celtic field with good agreement of the calculated data with the actual data. A fast drop in the upper boundary of the liquid phases region, observed with the data used approximately 100 days after the end of vertical growth of the steam chamber, indicates the risk of steam breakthrough.

Analytical and numerical study of gaseous flow in microchannel with sudden change of section (expansion / contraction)

In this paper, we study an isothermal gas flow (Argon) through a rectangular microchannel with sudden change of section (expansion / contraction). For that, we used two approaches, analytical and numerical, both based on the Navier-Stokes equations, which allows us predicting the pressure driven mass flow rate in the hydrodynamic and slip flow regimes. The analytical approach is elaborated considering the hypothesis of Stokes. The numerical approach is performed using the software Ansys/ Fluent for compressible flow. In the slip regime, the boundary conditions on the wall were added in the Ansys/Fluent software. Both the analytical and numerical mass flow rates show a good agreement in the hydrodynamic and slip flow regimes. The obtained results indicate that the diodicity (the dependence of the mass flow rate from the direction on perfusion) depends on the position of the sections’ change in the microchannel, and it is of the order of 2 in our configuration.

Influence of formulation parameters on the freeform extrusion process of ceramic pastes and resulting product properties

The rheology of a ceramic paste is known to be a key factor in the process of additive manufacturing of ceramic parts via extrusion freeforming. The rheological properties of ceramic pastes can be influenced by several formulation parameters. In this study, the mutual influence between formulation parameters, printing properties and mechanical properties of ceramic pastes (Al2O3) and the resulting green bodies are investigated. Special focus is set on elucidating the origins and causes of the altered paste properties to allow targeted material development of pastes for the use in extrusion freeforming. Glycerine and nanoparticulate boehmite needles are tested as additives and they successfully improve the printability in the extrusion freeforming process of the paste and compression strength of the green body. Considerable difference in the dependency of the mechanical properties on the formulation parameters was detected after a partial sintering of the green bodies at 1000 °C. Dewatering, shrinkage during drying and a running of the deposited lines could be reduced successfully by adjusting the formulation. The impact of the formulation parameters on the printing performance could be linked to the dependency of the volume flow rate on the ratio of pressure over viscosity.