Simulating Fluid Flow in a Compressed Valve

The objective of the work is to study fluid flow behavior through a pinch valve and to estimate the flow coefficient (KV ) at different opening positions of the valve. The flow inside a compressed valve is more complex than in a straight pipe, and it is one of main topics of interest for engineers in process industry. In the present work, we have numerically simulated compressed valve flow at different opening positions. In order to simulate the flow through pinch valve, several models of the elastomeric valve tube (pinch valve tube) at different opening positions were constructed in 2D-axisymmetric and 3D geometries. The numerical simulations were performed with the CFD packages; ANSYS FLUENT and ANSYS CFX by using parallel computing. The distributions of static pressure, velocity and turbulent kinetic energy have been studied at different opening positions of the valve in both 2D-axisymmetric and 3D experiments. The flow coefficient (KV ) values have been measured at different valve openings and are compared between 2D-axisymmetric and 3D simulation results.

Analytical Calculation of Stall-inception and Surge Points for an Axial-flow Compresor Rotor

Recently, a theoretical criterion to calculate the stability of an axial-flow compressor rotor has been presented in the scientific literature. This theoretical criterion was used for determining the locus of the stability line over the rotor map and for predicting the post-stall evolution of the constant-speed line of a rotor. The main objective of this paper is to improve the predictions of such a model. To do that, the paper proposes a different characterization of the characteristic azimuthal length and a calculation of the ratio of specific heats based on a polytropic exponent. Thanks to these new values, the model predicts two bifurcation points in the behaviour of the flow: the inception point of the instability and the surge point. Experimental data from a pure axial compressor are used to validate the model showing that the prediction of the flow coefficient at the surge point has an error inferior to 5%. For the rotor studied, the paper provides a quantitative and qualitative description of the inception of the instability and of the mechanism involved in the instable region of the compressor map. The paper also discusses the role of rotor efficiency in the position of the bifurcations and gives a sensitivity analysis of its position. Finally, it presents a discussion about how the model can explain the different behaviours exhibited by the same rotor when the flow coefficient is reduced

Letkuventtiilin mitoitus säätökäyttöön

Tässä diplomityössä käydään läpi IEC-60534 -standardin mukainen säätöventtiilin mitoitus kokoonpuristumattomille ja –puristuville virtauksille laskennassa tarvittavine yhtälöineen. Teoreettisessa osassa esitellään RF-letkuventtiilien rakennetta ja ominaisuuksia. Lisäksi käydään läpi putkivirtauksen perusperiaatteita. Koska letkuventtiilissä virtaavana fluidina on usein jokin liete, on työssä esitelty menetelmä lietevirtauksen aiheuttaman paine-eron laskentaan. Työssä on käsitelty myös kavitaation syntyä, laskennalliset mahdollisuudet kavitaation ennustamiseen sekä keinoja kavitaation estämiseksi. Kokeellisessa osassa suoritettiin mittauksia kolmella erikokoisella RF-letkuventtiilillä, joissa kussakin käytettiin kolmea erityyppistä letkua. Mittausten perusteella pystyttiin laskemaan kapasiteettikertoimet sekä määrittämään säätökäyrät mitatuille venttiileille ja letkutyypeille. Näistä tuloksista säätökäyrille sovitettiin yhtälöt, joiden perusteella saatiin laskettua kapasiteettikertoimien arvot myös muille venttiilikoille.

Desempenho de gotejadores com uso de efluente de esgoto doméstico tratado

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Proposta de válvula bypass para controle de velocidade de PIGs instrumentados: protótipo e simulação em bancada

In the Oil industry, oil and gas pipelines are commonly utilized to perform the transportation of production fluids to longer distances. The maintenance of the pipelines passes through the analysis of several tools, in which the most currently used are the pipelines inspection cells, popularly knowing as PIG. Among the variants existing in the market, the instrumented PIG has a significant relevance; acknowledging that through the numerous sensors existing in the equipment, it can detect faults or potential failure along the inspected line. Despite its versatility, the instrumented PIG suffers from speed variations, impairing the reading of sensors embedded in it. Considering that PIG moves depending on the speed of the production fluid, a way to control his speed is to control the flow of the fluid through the pressure control, reducing the flow rate of the produced flow, resulting in reduction of overall production the fluid in the ducts own or with the use of a restrictive element (valve) installed on it. The characteristic of the flow rate/pressure drop from restrictive elements of the orifice plate is deducted usually from the ideal energy equation (Bernoulli’s equation) and later, the losses are corrected normally through experimental tests. Thus, with the objective of controlling the fluids flow passing through the PIG, a valve shutter actuated by solenoid has been developed. This configuration allows an ease control and stabilization of the flow adjustment, with a consequent response in the pressure drops between upstream and downstream of the restriction. It was assembled a test bench for better definition of flow coefficients; composed by a duct with intern diameter of four inches, one set of shutters arranged in a plate and pressure gauges for checking the pressure drop in the test. The line was pressurized and based on the pressure drop it was possible to draw a curve able to characterize the flow coefficient of the control valve prototype and simulate in mockup the functioning, resulting in PIG speed reduction of approximately 68%.

Heat flow and heat conductivity coefficient measured in bottom sediments collected in Cruise 13 of R/V Akademik Sergey Vavilov in the Pechora Sea

In Cruise 13 of R/V Akademik Sergey Vavilov in the Pechora Sea, six heat flow varied from 50 to 75 mW/m**2. Deep heat flow in the Pechora Sea was calculated equal to 45 mW/m**2, which is confirmed by results of geological and geophysical studies and corresponds to Middle Baikal age of the basement. A model of structure of the lithosphere in the Pechora Sea is suggested. Total thickness of the lithosphere in the basin (190 km) determined from geothermal data agrees well with that in transition zones from the continent to the ocean. According to estimates of deep heat flow in the region obtained, thickness of the mantle (160 km), of the basaltic (15 km), and of the granitic (15 km) layers of the lithosphere were also evaluated. Temperature values at boundaries of the sedimentary layers were calculated over a geological and geophysical profile crossing the Pechora Sea basin. Temperatures obtained agree with the temperature interval of hydrocarbon generation and correspond to Permian-Triassic sedimentary sequences, which are the most productive ones in the Pechora Sea region from the point of view of oil and gas potential.

Variations of local heat transfer coefficient in piped flow of viscous liquids

Measurements were carried out to determine local coefficients of heat transfer in short lengths of horizontal pipe, and in the region of an discontinuity in pipe diameter. Laminar, transitional and turbulent flow regimes were investigated, and mixtures of propylene glycol and water were used in the experiments to give a range of viscous fluids. Theoretical and empirical analyses were implemented to find how the fundamental mechanism of forced convection was modified by the secondary effects of free convection, temperature dependent viscosity, and viscous dissipation. From experiments with the short tube it was possible to determine simple empirical relationships describing the axial distribution of the local 1usselt number and its dependence on the Reynolds and Prandtl numbers. Small corrections were made to account for the secondary effects mentioned above. Two different entrance configurations were investigated to demonstrate how conditions upstream could influence the heat transfer coefficients measured downstream In experiments with a sudden contraction in pipe diameter the distribution of local 1u3se1t number depended on the Prandtl number of the fluid in a complicated way. Graphical data is presented describing this dependence for a range of fluids indicating how the local Nusselt number varied with the diameter-ratio. Ratios up to 3.34:1 were considered. With a sudden divergence in pipe diameter, it was possible to derive the axial distribution of the local Nusse1t number for a range of Reynolds and Prandtl numbers in a similar way to the convergence experiments. Difficulty was encountered in explaining some of the measurements obtained at low Reynolds numbers, and flow visualization techniques wore used to determine the complex flow patterns which could lead to the anomalous results mentioned. Tests were carried out with divergences up to 1:3.34 to find the way in which the local Nusselt number varied with the diameter ratio, and a few experiments were carried out with very large ratios up .to 14.4. A limited amount of theoretical analysis of the 'divergence' system was carried out to substantiate certain explanations of the heat transfer mechanisms postulated.

Analysis of heat transfer coefficient in silica nanofluids with water as base fluid under transitional flow

The effect of Reynolds number variation in a vertical double pipe counterflow heat exchanger due to the changes in viscosity can cause the change in flow regime, for instance, when heats up and cools down, it can convert from turbulent to laminar or inversely, that can have significant effect on heat transfer coefficient and pressure drop. Mainly, the range of transition phase has been studied in this study with the investigation of silica nanofluid dispersed in water in three different concentrations. The results have been compared with distilled water sample and showed a remarkable raise in heat transfer coefficient while pressure drop has been increased respectively, as well. Although pumping power has to go up at the same time and it is a drawback, heat transfer efficiency grows for diluted samples. On the other hand, for the most concentrated sample, effect of pressure drop dominates which leads to decline in the overall efficiency.

Respostas agudas da variabilidade da frequência cardíaca após sesão de exercício de força com restrição de fluxo sanguíneo = : Acute responses of heart rate variabiblity afer blood flow restriction resistance exercise

Universidade Estadual de Campinas . Faculdade de Educação Física

Development of a Multicommutated Flow System with Chemiluminometric Detection for Quantification of Gentamicin in Pharmaceuticals

A new flow procedure based on multicommutation with chemiluminometric detection was developed to quantify gentamicin sulphate in pharmaceutical formulations. This approach is based on gentamicin's ability to inhibit the chemiluminometric reaction between luminol and hypochlorite in alkaline medium, causing a decrease in the analytical signal. The inhibition of the analytical signal is proportional to the concentration of gentamicin sulphate, within a linear range of 1 to 4 mu g mL(-1) with a coefficient variation <3%. A sample throughput of 55 samples h(-1) was obtained. The developed method is sensitive, simple, with low reagent consumption, reproducible, and inexpensive, and when applied to the analysis of pharmaceutical formulations (eye drops and injections) it gave results with RSD between 1.10 and 4.40%.

A flow injection procedure based on solenoid micro-pumps for spectrophotometric determination of free glycerol in biodiesel

A flow system designed with solenoid micro-pumps is proposed for fast and greener spectrophotometric determination of free glycerol in biodiesel. Glycerol was extracted from samples without using organic solvents. The determination involves glycerol oxidation by periodate, yielding formaldehyde followed by formation of the colored (3,5-diacetil-1,4-dihidrolutidine) product upon reaction with acetylacetone. The coefficient of variation, sampling rate and detection limit were estimated as 1.5% (20.0 mg L(-1) glycerol, n =10), 34 h(-1), and 1.0 mg L(-1) (99.7% confidence level), respectively. A linear response was observed from 5 to 50 mg L(-1), with reagent consumption estimated as 345 mu g of KIO(4) and 15 mg of acetylacetone per determination. The procedure was successfully applied to the analysis of biodiesel samples and the results agreed with the batch reference method at the 95% confidence level. (C) 2010 Elsevier B.V. All rights reserved.

An environmentally friendly flow system for high-sensitivity spectrophotometric determination of free chlorine in natural waters

A green and highly sensitive analytical procedure was developed for the determination of free chlorine in natural waters, based on the reaction with N,N-diethyl-p-phenylenediamine (DPD). The flow system was designed with solenoid micro-pumps in order to improve mixing conditions by pulsed flows and to minimize reagent consumption as well as waste generation. A 100-cm optical path flow cell based on a liquid core waveguide was employed to increase sensitivity. A linear response was observed within the range 10.0 to 100.0 mu g L(-1), with the detection limit, coefficient of variation and sampling rate estimated as 6.8 mu g (99.7% confidence level), 0.9% (n = 20) and 60 determinations per hour, respectively. The consumption of the most toxic reagent (DPD) was reduced 20,000-fold and 30-fold in comparison to the batch method and flow injection with continuous reagent addition, respectively. The results for natural and tap water samples agreed with those obtained by the reference batch spectrophotometric procedure at the 95% confidence level. (C) 2010 Elsevier By. All rights reserved.

A greener and highly sensitive flow-based procedure for carbaryl determination exploiting long pathlength spectrophotometry and photochemical waste degradation

An environmentally friendly analytical procedure with high sensitivity for determination of carbaryl pesticide in natural waters was developed. The flow system was designed with solenoid micro-pumps in order to improve mixing conditions and minimize reagent consumption as well as waste generation. A long pathlength (100 cm) flow cell based on a liquid core waveguide (LCW) was employed to increase the sensitivity in detection of the indophenol formed from the reaction between carbaryl and p-aminophenol (PAP). A clean-up step based on cloud-point extraction was explored to remove the interfering organic matter, avoiding the use of toxic organic solvents. A linear response was observed within the range 5-200 mu g L(-1) and the detection limit, coefficient of variation and sampling rate were estimated as 1.7 mu g L(-1) (99.7% confidence level), 0.7% (n=20) and 55 determinations per hour, respectively. The reagents consumption was 1.9 mu g of PAP and 5.7 mu g of potassium metaperiodate, with volume of 2.6 mL of effluent per determination. The proposed procedure was selective for the determination of carbaryl, without interference from other carbamate pesticides. Recoveries within 84% and 104% were estimated for carbaryl spiked to water samples and the results obtained were also in agreement with those found by a batch spectrophotometric procedure at the 95% confidence level. The waste of the analytical procedure was treated with potassium persulphate and ultraviolet irradiation, yielding a colorless residue and a decrease of 94% of total organic carbon. In addition, the residue after treatment was not toxic for Vibrio fischeri bacteria. (c) 2010 Elsevier B.V. All rights reserved.