A capillary suction pump giving constant flow rates

Vincristine has been proven promising regarding its safety and efficacy for the renal artery denervation both in experimental models and in humans. The aim of the study was to compare in an experimental model the efficacy of constant versus random flow rate delivery of vincristine on renal sympathetic denervation. We used 10 juvenile Landrace swine. After the introduction of a 7F sheath into the femoral artery, a guide wire was advanced into the distal part of the renal artery. Then the first delivery balloon catheter, which delivers vincristine in random flow rate, was advanced at the proximal part of the artery, and the balloon was inflated in order to locally deliver vincristine to the media of the renal artery. The process was repeated in the contralateral renal artery, with the use of the double balloon catheter that delivers vincristine with a constant flow rate. Euthanasia of the animals was performed at 28 days. All sections were processed for histological and immunohistochemical analysis. The delivery of vincristine with both catheters was successful and uncomplicated. Immunohistochemistry showed that the mean number of intact nerves in all sections was significantly lower in the group of vincristine delivered with constant flow catheter compared to the group that the delivery was performed in a random fashion. (1.48 ± 0.37 vs. 1.70 ± 0.41, p = 0.04). Chemical renal denervation with vincristine by a constant flow rate catheter is more effective compared to the denervation performed by a catheter that delivers vincristine in a random fashion.

The response time of magnetorheological (MR) fluids to an external magnetic field is a few milliseconds. However, the overall response time in MR devices under a magnetic field is a function of electromagnetic parameters, the capabilities of the driving electronics, as well as, the operation conditions. Therefore, the overall response time of a MR device depends on the internal device design parameters. In this work, the response times of MR fluid and MR fluid valves have been studied under various flow configurations. Two types of valving geometries; annular flow, and radial flow are considered in the MR fluid valve designs. The transient pressure response of MR fluid valves are evaluated by using a diaphragm pump with a constant volume flow rate. The performance of each MR valve is characterized using a voltage step input, as well as, a current step input while recording the activation electric voltage/current, magnetic flux density, and pressure drop as a function of time. The variation of the response time of the MR valves under constant volume flow rate is experimentally investigated. The system’s time constant is determined under induced pressure changes. In order to obtain the response time of the MR fluid a Maxwell model with a time constant is employed to describe the field induced pressure behavior of MR fluid under a steady flow. The results demonstrate that the pressure response times of the MR fluid and the MR valves depend on the designs of the electric parameters and the valve geometry. MR valves in annular flow geometry have a slow falling response time compared to their rising response time. MR valves in radial flow geometry result in faster pressure response times both in rising and falling states.

In this study, the response times of magnetorheological fluids and magnetorheological fluid valves are studied under various flow configurations. Two types of valving geometries, annular flow and radial flow, are considered in the magnetorheological fluid valve designs. The transient pressure responses of magnetorheological fluid valves are evaluated using a diaphragm pump with a constant volume flow rate. The performance of each magnetorheological valve is characterized using a voltage step input as well as a current step input while recording the activation electric voltage/current, magnetic flux density, and pressure drop as a function of time. The variation of the response time of the magnetorheological valves under constant volume flow rate is experimentally investigated. The Maxwell model with a time constant is employed to describe the field-induced pressure behavior of magnetorheological fluid under a steady flow. The results demonstrate that the pressure response times of the magnetorheological fluid and the magnetorheological valves depend on the designs of the electric parameters and the valve geometry. Magnetorheological valves with annular flow geometry have a slower falling response time compared to their rising response time. Magnetorheological valves with radial flow geometry demonstrate faster pressure response times both in rising and in falling states.

The numerical analysis of nanofluids in heat pipe is investigated using CFD, computational fluid dynamics, software modeling, FLUENT. The modeling was completed for base fluids and validated against earlier study. The alumina-water nanofluids are used for the investigation due to availability of huge literature. The thermal conductivity and viscosity are evaluated on the basis of literature and used in the study. For the other thermo-physical properties such as density and specific heat, mass based mixture model approach has been used. To see the concentration effect of nanofluids, mixtures with volume fraction of 1, 2, 3 and 5% are considered. The nanofluids mixture assumed to be homogeneous fluid flow in this simulation. The inlet velocity boundary condition, BC, is given by two approaches, mass flow arte and volume flow rate. The results showed that the nanofluids performance is similar to the base fluids while inlet BC is constant volume flow rate. On the other hand, nanofluids enhanced the performance over the base fluid while constant mass flow rate BC is used.

With the use of theoretical models of filtration liquid flows in fractures of finite and infinite lengths, formed in an oil stratum, the problem on the production of oil from a well, operating in the regimes of constant differential pressure or constant flow rate in this stratum, was solved. On the basis of approximate solution of the problem on the flow of oil from a stratum into a fracture formed in it by the method of successive changing stationary states, fairly simple analytical formulas have been obtained. A comparison of the results of numerical calculations of the practically important parameters of an oil stratum and a hydraulic fracture in it by the approximate formulas constructed and the corresponding exact formulas, which are much more complex than the approximate formulas, has shown that these results are almost identical. In particular, the errors in determining the evolution of the pressure field in a well and its flow rate by the approximate formulas did not exceed several percent. On the basis of numerical analysis of the approximate solutions obtained, the influence of the porosity and permeability of the stratum, the length of a fracture in it, and the rheological properties of the liquid saturating the stratum on the evolution of the pressure in the fracture, the flow rate of a well operating in the regime of constant differential pressure in the stratum, and the changes in the pressures in the fracture and in the well at a constant well flow rate was investigated.

An inexpensive and simple pumping principle is described that is capable of delivering both small and constant flow rates (10–1,000 nl/min) over a longer period of time (days to weeks). The concept is based on controlled evaporation of a liquid through a membrane into a gas space containing a sorption agent. As long as the sorption agent keeps the vapor pressure in the gas phase below saturation, fluid evaporated from the membrane is replaced by capillary forces inducing flow from a reservoir. In a feasibility study, a total volume of 300 μl of Ringer's solution has been continuously pumped over a period of six days, resulting in an constant average flow rate of 35 nl/min (590 pl/s). The maximum liquid volume transported is limited by sorption capacity and amount of the sorption agent. Low fabrication costs, high reliability (no moving parts), the suitability for integration into planar system architectures and the lack of a special external energy source besides an environment of regulated temperature are important features of the concept, in particular with regard to its potential application in continuous patient monitoring. Truly continuous flow can be achieved in contrast to many other pump mechanisms leading to discontinuous, pulse-type flow. A challenge for a broader range of applications is the inherent temperature dependence of the flow rate. In its current version, the pump can only be used in a suction-mode.

A numerical investigation on the utilization of a depleted natural gas field for seasonal hydrogen storage: A case study for Değirmenköy gas field

This Paper introduces a feedback-type fluidic oscillator design with adjustable frequency at a constant flow rate. Details of the internal and external flowfields were revealed by numerical simulations with the help of frequency measurements and visualizations. Fluidic oscillator’s internal flowfield was manipulated by fluid injection from the islands of the oscillator into the interaction chamber. The interaction between the oscillator’s main jet and the control jets was observed to generate vortices in the mixing shear layers of the jets due to the Kelvin–Helmholtz instabilities. These vortices started to govern the separation bubble characteristics as the control flow rate was increased. After a certain control flow rate threshold was exceeded, the oscillations were no longer controlled by the feedback flow. Instead they were controlled by the vortices generated by the instabilities, resulting in much higher frequencies. These high-frequency oscillations in the supermode control flow rates were determined to be as high as five times the regular frequency of the oscillator. However, a reverse relationship between frequency and sweep angle was also identified. Depending on the amount of control flow at a constant total flow rate, three regions and five cases distributed in these regions are reported.

Determination of formation permeability and well skin factor is important for forecasting flow rates of oil and gas wells. A new technique for analysing test data for stimulated oil wells produced at a constant bottomhole pressure (BHP) has been developed. The method presented in this paper allows one to calculate the skin factor and estimate the formation permeability. It is assumed that the instantaneous flow rate and time data are available from a well produced against a constant bottomhole pressure. Only records of the flowing time and flow rate data are required to compute the values of the skin factor and formation permeability. A semi-theoretical equation is used to approximate the dimensionless flow rate. Our objective is to validate the new suggested method (prior to conducting a field test) by using a simulated example, where a numerical solution is used as an ‘exact’ solution.‘Bottomhole pressure’ means the pressure determined at the face of the producing horizon by means of a pressure-recording instrument. In the case of gas wells or wells having no liquid in the well bore, it means the pressure as calculated by adding the pressure at the surface of the ground to the calculated weight of the column of gas from the surface to the bottom of the hole. Determination of bottomhole pressure (BHP) is an important problem in the oil and gas industry (Akhter and Kreitler, 1990; Schechter, 1992; Yang et al., 2003). At present the majority of well tests are conducted at constant flow rates, where simple solutions of the diffusivity equation can be applied. However, many investigators (Ehlig-Economides and Ramey, 1981; Sengul, 1983; Uraiet and Raghavan, 1980 a.o.) hold to the idea that in practice it is easier to conduct well tests at a constant bottomhole pressure (BHP). It is very difficult to maintain a constant flow rate during long flowing times (especially when testing low permeability formations). The advantages of the constant BHP test are: (1) the fluid production can be easily controlled (at constant flow rate tests the BHP is changing with time); and (2) wellbore storage effects on the test data are short-lived. One of the reasons that constant BHP tests have not been utilized in reservoir engineering is that only numerical solutions of the diffusivity equation for a cylindrical source with a constant BHP have been available. Due to the similarity in Darcy’s and Fourier’s laws, the same differential diffusivity equation describes the transient flow of incompressible fluid in a porous medium and heat conduction in solids. As a result, a correspondence exists between the following parameters: volumetric flow rate, pressure gradient, mobility (formation permeability and viscosity ratio), hydraulic diffusivity coefficient and heat flow rate, temperature gradient, thermal conductivity and thermal diffusivity. Thus, the same analytical solutions of the diffusivity equation (at corresponding initial and boundary conditions) can be utilized for determination of the above-mentioned parameters. Earlier we suggested a semi-theoretical equation to approximate the dimensionless heat flow rate from an infinite cylindrical source with a constant bore-face temperature (Kutasov, 1987). This equation (in terms of pressure and flow rate) was used to process data of step pressure tests when fluid is produced at two successive bottomhole pressures (Kutasov, 1998). The same equation was used to estimate the efficiency of stimulating operations (Kutasov and Kagan, 2003). In both cases a technique for determining the formation permeability and skin factor from flow tests in stimulated wells was developed. The objective of this paper is to suggest a similar technique for determination of the values of formation permeability and skin factor from drawdown constant BHP tests in stimulated wells. We should also like to mention that for damaged wells, when the dimensionless time based on the apparent well radius is very large, a simple equation can be used to process field data (Sengul, 1983; Earlougher, 1977).

Cement-based grout has been widely used in various civil engineering applications. The diffusion of cement-based grouts in porous media is an important issue in soil sealing and the estimate of grouting. To better understand the effects of grouting parameters on the viscosity of slurry, the porosity of an injected media and the pressure variations under constant flow rate and constant pressure conditions, a series of laboratory tests were conducted on the fractal characteristics of sand in a column. Additionally, different grouting flow rates and pressures, water/cement ratios and mass fractal dimensions were studied. The experimental results show the following responses: (1) the variation in the diffusion pressure of the slurry under the condition of a constant pressure is clearly different from that under constant pressure. (2) There is a strong correlation between the porosity and water/cement ratio regardless different hydraulic operating conditions, whereby a reduction or increase in the water/cement ratio control the range of the slurry diffusion. (3) Regardless of the hydraulic operating conditions, the grouting pressure presents a nonlinear decreasing law with the increase in distance from the grouting source. (4) An excessive flow rate or pressure is not conducive to the diffusion of slurry.

Accurate measurement of relative permeability curve is the basis for evaluating gas reservoir performance. The unsteady-state method could bring significant measurement error for low-permeability cores. However, it is difficult to control the constant gas flow rate in the traditional steady-state method, which obstacles the experimental operation. In this study, an improved steady-state method was proposed. First, the pressure value obtained from the experiment, when the gas permeability no longer changed with the average pressure on the rock core, was set as the testing pressure. Then, the gas was injected under constant pressure, and the water was injected with a constant flow rate. Finally, the relative permeability values of gas and water phases were calculated based on Darcy’s law. Comparative analysis of the results of the relative permeability curves under formation pressure and pressure with negligible slip effect indicates that the relative permeability curves are the same in gas and water phases, proving the feasibility of the new method. Further, the results were compared with those of the test method at normal pressure, the water-phase relative permeability showed no significant change, the relative permeability of gas phase was larger, the two-phase flow area became wider, and the irreducible water saturation was lower than that at the normal pressure. This result reflects that pressure does not significantly affect the flow of wetting phase but tremendously influences the nonwetted phase under low pressure. The relationship between relative permeability and water saturation is linear in the semilogarithmic coordinate diagram and can be described by using the following relationship: ln k rg / k rw = a S w + ln b . With the decrease in the core permeability, relative permeability curve, and isotonic point moved to the right, irreducible water saturation gradually increased, and residual gas saturation decreased, indicating that the smaller permeability induced a lower gas-phase flow capacity.

Dehydrogenation performance of metal hydride container utilising MgH2-based composite

Velocity of capillary flow in closed or open channels decreases as the flow proceeds down the length of the channel, varying as the inverse of the square root of time or as the inverse of travel distance. In order to increase the flow rate-and extend the duration of the flow-capillary pumps have been designed by mimicking the pumping principle of paper or cotton fibers. These designs provide a larger volume available for the wicking of the liquids. In microsystems for biotechnology, different designs have been developed based on experimental observation. In the present paper, the mechanisms at the basis of capillary pumping are investigated using a theoretical model for the flow in an open-channel "capillary tree" (i.e., an ensemble of channels with bifurcations mimicking the shape of a tree). The model is checked against experiments. Rules for obtaining better designs of capillary pumps are proposed; specifically, we find (1) when using a capillary tree with identical channel cross-sectional areas throughout, it is possible to maintain nearly constant flow rates throughout the channel network, (2) flow rate can be increased at each branch point of a capillary tree by slightly decreasing the areas of the channel cross section and decreasing the channel lengths at each level of ramification within the tree, and (3) higher order branching (trifurcations vs bifurcations) amplify the flow rate effect. This work lays the foundation for increasing the flow rate in open microfluidic channels driven by capillary flow; we expect this to have broad impact across open microfluidics for biological and chemical applications such as cell culture, sample preparation, separations, and on-chip reactions.

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

Using the Ansys Fluent 2020 R2 computational fluid dynamics suite, a method for calculating the three-dimensional velocity field in helicoid-type turbine flowmeters has been developed, based on the torque balance equation, i.e. the equality of the driving and retarding torques on the turbine, which is achieved at an equilibrium rotation speed for a given constant volumetric flow rate (which is fulfilled when the angular acceleration is equal to zero). At constant flow rate, when the rotor speed changes, the moment on the rotor blade is determined. The value of the speed is found at which the moment changes sign. The dependence of the torque on the number of revolutions is plotted on a graph and the true number of revolutions is determined at which the torque is zero for a given flow rate. The basis for the mathematical description of turbulent three-dimensional flow in flow meters is a system of differential equations of conservation of mass (continuity equation), momentum and the standard k-ω turbulence model (based on the Wilcox model) with partial derivatives in cylindrical coordinates in a three-dimensional problem setting. The multiple reference frame method incorporated into the Ansys Fluent computing suite allows reducing a problem involving stationary and rotating elements to a stationary one. The numerical calculation was performed at various flow rates (from 354 to 1982 m3/h) and kinematic viscosity (from 0.2 to 140 cSt). The main characteristics of turbine flowmeters are determined: the specific meter factor (or K-factor), Strouhal and Roschko numbers. The greatest discrepancy between the numerical calculation and the experimental data on the K-factor value is obtained at low flow rates and at the highest viscosity of 140 cSt (which is beyond the scope of application of the researched flowmeter) and is no more than 5%.