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1
Content available remote Struktura roztworów polimerowo-micelarnych
PL
Roztwory polimerowo-micelarne swoje właściwości zmniejszania oporów przepływu zawdzięczają strukturze wewnętrznej. Struktura ta powstaje najczęściej podczas zmieszania roztworu polimerowego z roztworem zawierającym środek powierzchniowo czynny.
EN
Fundamentals and review with 24 refs.
EN
In the present work, rheological behaviour of a fine particulate fly ash slurry suspension is studied with and without addition of an additive. Rheological experiments are performed for the range of shear rate from 50 to 200 s1.Sodium sulfate is used as an additive in the fraction of 0.2, 0.4 and 0.6% (by weight). Addition of sodium sulfate to the fly ash slurry suspension leads to an improvement of its rheological characteristics. A reduction in relative viscosity and pressure drop is more pronounced with the addition of sodium sulfate in proportion of 0.4%, while marginal with 0.2 and 0.6% (by weight). The analysis reveals that the fly ash suspension has a potential to for being transported in a slurry pipeline with higher concentration and minimum energy consumption.
3
Content available remote Pressure drop reduction in fluid flows with a polymer solution
EN
This work is targeted at making available some data to enhance the development of better predictive models for drag reduction (DR) in two-phase flows. Oil-water flows studies were carried out by using a horizontal acrylic pipe (14 mm ID) with tap water and a middle distillate oil the flowing liquids. A hydrolysed polyacrylamide served as the polymer in the water phase. Polyethylene oxide (PEO) with two different molecular weights was equally investigated. At an optimal polymer concentration of 20 ppm, drag was lowered as Reynolds number increased. While drag reduction was effectively described by models, it increased with polymer weight.
4
Content available Model of forced turbulence for pulsing flow
EN
The article deals with fluid motion along an infinite hose. Taking into consideration the Stokes equation, the tangential friction stresses according to Newton and the Reynolds equation, the differential equation of the velocity change in radius is developed taking into account the pulsating component of the friction forces in the turbulent flow. Turbulence is defined as the impulse component of a flow, characterized by a pressure drop along a dynamic length of flow, a frequency response, and an oscillation amplitude of the pressure drop of pulse (which is given by the time equation of the oscillation). The velocity distribution along the radius of the hose in the time interval of one second was modelled for pressure drops in the range from 6000 to 18000 Pa and the amount of transported medium in the range from 1.667·10-5 to 6.667·10-5 m3 , which corresponded to the length of pulse plug. The dynamic viscosity of the medium (milk) of 1.79 · 10-3 Pa·s and its density of 10273 N·s2 /m4 were accounted at the simulation. The developed analytical dependence of the velocity of the forced turbulence of the pulsating flow allows to calculate the absolute value of the velocity at a given point of crosssection of the pipeline, and characterizes the physical process of flow of Newtonian fluids and gases in the pipeline.
EN
In this study, polypropylene meltblown nonwoven fabrics with different structure parameters such as fiber diameter, pore size, and areal density were prepared by the industrial production line. The morphology of meltblown nonwoven fibers was evaluated by using scanning electron microscope, and the diameter of fibers was analyzed by using image-pro plus software from at least 200 measurements. The pore size of nonwoven fabric was characterized by a CFP-1500AE type pore size analyzer. The filtration efficiency and pressure drop were evaluated by TSI8130 automatic filter. The results showed that the pressure drop of nonwoven fabrics decreased with the increase in pore size; the filtration efficiency and the pressure drop had a positive correlation with the areal density. However, when the areal density is in the range of 27–29 g/m2, both filtration efficiency and pressure drop decreased with the increase of areal density; when the areal density was kept constant, the filtration efficiency decreased as the pore size decreased; when the pore size of the meltblown nonwoven fabric is less than 17 μm, the filtration efficiency increased as the pore diameter decreased; when the pore diameter of the nonwoven fabric is larger than 17 μm. In a wide range, the pressure drop decreased as the fiber diameter decreased.
EN
In this paper, investigation of the effect of Reynolds number, nanoparticle volume ratio, nanoparticle diameter and entrance temperature on the convective heat transfer and pressure drop of Al2O3/H2O nanofluid in turbulent flow through a straight pipe was carried out. The study employed a computational fluid dynamic approach using single-phase model and response surface methodology for the design of experiment. The Reynolds average Navier-Stokes equations and energy equation were solved using k-ε turbulent model. The central composite design method was used for the response-surface-methodology. Based on the number of variables and levels, the condition of 30 runs was defined and 30 simulations were performed. New models to evaluate the mean Nusselt number and pressure drop were obtained. Also, the result showed that all the four input variables are statistically significant to the pressure drop while three out of them are significant to the Nusslet number. Furthermore, sensitivity analysis carried out showed that the Reynolds number and volume fraction have a positive sensitivity to both the mean Nusselt number, and pressure drop, while the entrance temperature has negative sensitivities to both.
EN
The effect of shell side and coil side volume flow rate on overall heat transfer coefficient, effectiveness, pressure drop and exergy loss of shell and helical coil heat exchanger were studied experimentally under steady state conditions. The working fluid, i.e., water was allowed to flow at three different flow rates of 1, 2, and 3 l/min on shell side (cold water) and at 1, 1.5, 2, 2.5, and 3 l/min on coil side (hot water) for each shell side flow rate at the temperatures of 298±0.4 K and 323±0.4 K, respectively. The results found that the overall heat transfer coefficient increased with increasing both shell side and coil side volume flow rates. The inner Nusselt number significantly increased with the coil side Dean number.
8
Content available remote Features of hydrates transportation in a fluid flow
EN
Significant deposits of natural gas are in a gas-hydrated state. One of the options for a possible solution is the transport of hydrates in a fluid flow. The stability of crystalline hydrates, namely, their presence in the solid state, affects both temperature and pressure. The influence of the concentration of solid particles on the reduction or increase of the friction factor is shown, which leads to a decrease or increase in pressure drop during the flow of liquid with solid admixtures. The analytical dependences of the friction factor from the Reynolds number on a certain concentration of solid admixtures in a liquid are proposed A plot of the dependence of the friction factor from the Reynolds number on a certain concentration of rubber crumb and different granulometric composition was constructed.
EN
Due to the application of coil-shaped coils in a compressed gas flow exchanger and water pipe flow in airconditioner devices, air conditioning and refrigeration systems, both industrial and domestic, need to be optimized to improve exchange capacity of heat exchangers by reducing the pressure drop. Today, due to the reduction of fossil fuel resources and the importance of optimal use of resources, optimization of thermal, mechanical and electrical devices has gained particular importance. Compressed heat exchangers are the devices used in industries, especially oil and petrochemical ones, as well as in power plants. So, in this paper we try to optimize compressed heat exchangers. Variables of the functions or state-of-the-machine parameters are optimized in compressed heat exchangers to achieve maximum thermal efficiency. To do this, it is necessary to provide equations and functions of the compressed heat exchanger relative to the functional variables and then to formulate the parameter for the gas pressure drop of the gas flow through the blades and the heat exchange surface in relation to the heat duty. The heat transfer rate to the gas-side pressure drop is maximized by solving the binary equation system in the genetic algorithm. The results show that using optimization, the heat capacity and the efficiency of the heat exchanger improved by 15% and the pressure drop along the path significantly decreases.
EN
Nanofiber properties, and the possibilities of their application in industry, including the production of car air intake filtration materials for vehicle engines are discussed. The attention is paid to the low efficiency of standard filtration materials based on cellulose in the range of dust grains below 5 μm. The properties of filtration materials with nanofibers addition are described. The conditions, and methodology of material filter paper tests at the station with particle counter were developed. Studies on the filtration characteristics, such as: efficiency, accuracy, as well as pressure drop of filtration materials differing in structure were made: standard paper, cellulose, and these materials with the addition of nanofibers. These are commonly used filter materials for filter inserts production of car air intake systems. Test results show significantly higher values of the efficiency, and filtration accuracy of materials with nanofiber layer addition of dust grains below 5 μm in comparison with standard filter paper. It was found that there are 16 μm dust grains in the air flow behind the insert made out of cellulose, which may be the reason for the accelerated wear of the engine's "piston-piston ring-cylinder" association. Lower values of dust mass loading coefficient km for filtration materials with the addition of nanofiber layer, in relation to standard filter paper were observed.
PL
Praca zawiera opis eksperymentalnych badań przepływowych procesu skraplania wysokociśnieniowych czynników chłodniczych w pionowych minikanałach rurowych. Zbadano wpływ gęstości strumienia masy, stopnia suchości pary i średnicy wewnętrznej minikanału na proces skraplania. W tych samych warunkach skraplano czynniki R404A, R407C, R410A. Opracowanie obejmuje również podsumowanie danych uzyskanych podczas procesu skraplania wszystkich trzech badanych czynników chłodniczych. Wyniki badań eksperymentalnych porównano z wynikami modelowania teoretycznego według zależności opracowanych przez innych autorów. Zgodność danych modelowania z wynikami eksperymentu została uznana za niezadowalającą. Na podstawie wyników danych eksperymentalnych uzyskano model służący do predykcji spadków ciśnienia dla niskich strumieni ciepła (q do 5000 W/m2).
EN
The paper consists a description of experimental flow tests of high- -pressure refrigerants condensation process in vertical pipe minichannels. The influence of mass flux density, vapour quality and minichannel’s internal diameter on the condensation process was investigated. Under the same conditions, R404A, R407C, R410A refrigerants were condensed. The work also includes a summary of data obtained during the condensation process of all three tested refrigerants. The results of experimental studies were compared with the results of theoretical modeling according to correlations developed by other authors. The compliance of the modeling data with the results of the experiment was considered unsatisfactory. Based on the results of experimental data, a pressure drop prediction model was obtained for low heat fluxes (q up to 5000 W/m2).
EN
Helical coil heat exchangers are widely used in a variety of industry applications such as refrigerationsystems, process plants and heat recovery. In this study, the effect of Reynolds number and theoperating temperature on heat transfer coefficients and pressure drop for laminar flow conditions wasinvestigated. Experiments were carried out in a shell and tube heat exchanger with a copper coiledpipe (4 mm ID, length of 1.7 m and coil pitch of 7.5 mm) in the temperature range from 243 to 273 K.Air – propan-2-ol vapor mixture and coolant (methylsilicone oil) flowed inside and around the coil,respectively. The fluid flow in the shell-side was kept constant, while in the coil it was varied from 6.6to 26.6 m/s (the Reynolds number below the critical value of 7600). Results showed that the helicalpipe provided higher heat transfer performance than a straight pipe with the same dimensions. Theconvective coefficients were determined using the Wilson method. The values for the coiled pipe werein the range of 3–40 W/m2·K. They increased with increasing the gas flow rate and decreasing thecoolant temperature.
13
Content available remote Flows of Sisko Fluid Through Symmetrically Curved Capillary Fissures and Tubes
EN
This paper presents a general analytical method for deriving mathematical relationships between pressure losses and the volumetric flow rate for laminar flows of a Sisko fluid. In this paper, only the laminar flow of Sisko type fluids is considered. It was demonstrated that the method can be used to find solutions for other pseudoplastic fluids and for different hapes of fissures and tubes. It can also be a good basis for numerical integration when analytical expressions are hard to obtain due to mathematical complexities. As an example, the following cases of convergent-divergent or divergent-convergent fissures and tubes, namely: parabolic, hyperbolic, hyperbolic cosine and cosine curve were considered. For each example, the formulae for pressure losses, volumetric flow rate and flow velocity were obtained. The most general forms of these formulas can be obtained by introducing hindrance factors.
EN
Experimental and Numerical studies were carried out on turbulent heat transfer and friction factor loss through a triangular chevron channel. For uniform wall heat flux equal 1350 (W/m²) using air as a working fluid. Reynolds number varied from 3000 to 10000, phase shifted at the range of 0≤ϕ≤180, with variation distance between chevron surfaces (5 ≤ D ≤ 35 mm). Nu increased and TEF decreased in increasing of Re. The TEF and Nu increased with closing to channel phase shift angle 90˚, the best performance was noticed on phase shift, ϕ=90º. At the end of this paper effect of distance between chevron surfaces presented, The TEF and Nu increased with decreasing to channel distance and the best performance was noticed on closing to D=5(mm).
EN
Nanofiber properties and the possibilities of their application in industry, including car air intake filtration materials production for vehicle engines are discussed. The attention is paid to the standard filtration materials low efficiency in the range of dust grains below 5 μm. Filtration materials properties with nanofibers addition are presented. Filter paper test conditions and methodology at the station with particle counter were developed. Filtration efficiency characteristics, and accuracy studies as well as filtration materials pressure drop differing in structure were made: standard paper, and materials with nanofibers addition. These are commonly used filter materials for car air intake systems production. Filtration materials with nanofibers addition test results show significantly higher efficiency values, and efficiency for dust grains below 5 μm in comparison with standard filter paper. It was found that there are 16 μm dust grains in the airflow behind the cellulose insert, which may be the reason for the accelerated wear of the engine’s “piston-cylinder” association. Lower dust mass loading km values of filtration materials with nanofibers addition in relation to standard filter papers were observed.
PL
Przedstawiono wyniki badań dotyczących hydrodynamiki przepływu układu gaz-ciecz w rurze poziomej wypełnionej pianą metalową. Podczas badań mierzono opory przepływu układu powietrzewoda na odcinku rury wypełnionej pianą metalową. Otrzymane wyniki pomiarów porównano z wartościami oporów przepływu obliczonymi zgodnie z modelami zarówno powszechnie uznanymi dla przepływu układów dwufazowych w pustej mrze, jak i odnoszącymi się do ich przepływu przez ośrodki porowate. Analiza zmierzonych i obliczonych wartości oporów przepływu dała podstawę do oceny wpływu obecności piany metalowej w rurze na hydrodynamikę przepływu układu gaz-ciecz.
EN
Measurements results related to the hydrodynamics of gas-liquid system flow are presented. During the research, the pressure drop of air-water system flow through a pipe section filled with metal foams was measured. The obtained results were compared with pressure drop values calculated according to commonly recognized models for twophase flow through an empty pipe as well as models relating to twophase flow through porous media. The analysis of measured and calculated pressure drop values led to the assessment of influence of metal foam presence in a pipe on two-phase flow hydrodynamics.
PL
Przedstawiono wyniki obliczeń CFD dotyczących przepływu przez zwężkę pomiarową z odbiorem przy tarczowym. Obliczenia wykonano za pomocą programu Ansys Fluent 16.0 przy użyciu modelu Species transport oraz modelu turbulencji k-ω SST. Podano wartości spadków ciśnień obliczone dla pięciu wydatków objętościowych mieszaniny gazów. Porównano je z wynikami uzyskanymi za pomocą oprogramowania TNflow 3.10, które jest specjalistycznym narzędziem do projektowania zwężek pomiarowych. Błąd względny porównywanych wyników mieścił się w zakresie 10,6÷3,7%.
EN
The paper focuses on CFD simulations included results of llow through the orifice with the close-to-plate tapping. The presented calculations were made with the use of commercial CFD code Ansys Fluent 16.0. Additionally, Species transport model and k-ω SST turbulence model applied in simulations. The pressure drop for five values of gas mixture volumetric flow rate is given. Numerical results were compared with TNflow 3.10 software being a tool dedicated to the orifice design. The relative error of compared results was in a rangę 10.6÷13.7%.
PL
W artykule omówiono prace związane z zastąpieniem dotychczas stosowanej normy dotyczącej filtracji powietrza dla wentylacji ogólnej (PN-EN 779) serią norm PN-EN ISO 16890. Zaprezentowano aktualne zasady badania oraz klasyfikacji filtrów powietrza. Przedstawiono wyniki badania zmian skuteczności filtracji i oporu przepływu aerozolu w zakresie cząstek stałych o wielkości od 0,3 µm do 10 µm, w celu określenia przynależności przykładowego filtru powietrza do grupy PM10, PM2,5 lub PM1.
EN
The article discusses the replacement of the existing standard for air filtration for general ventilation (PN-EN 779) with a series of standards PN-EN IS0 16890 This article presents current T, for testing and classification of an filters. The results of the study which investigated changes in" filtration efficiency and aerosol flow resistance in the range of O 3 µm to 10 µm were presented to determine the inclusion of an exemplary air filter in the group PM10, PM2.5 and PM1. 41
EN
The paper describes issues related to pressure drop that accompanies the phenomenon of maldistribution of working fluid between the channels of a model minichannel plate heat exchanger. The research concerns a single exchanger’s plate containing 51 (in every geometry) parallel rectangular minichannels of hydraulic diameters 461 µm, 571 µm, 750 µm, and 823 µm. In addition, more complex geometry has been investigated, equipped with additional diagonal channels (so called extended geometry). The moment of the liquid phase transition through the heat exchanger was recorded at the flow rates ranging from 0.83 g/s to 13.33 g/s in the inlet manifold. The paper discusses the total pressure drop as a function of the flow rate and the characteristic dimension of minichannels, as well as the pressure drop as a function of the time of the fluid passage through the main part of the measuring section in which measurements were done. The resulting profiles correlate with the images of the flow distribution between channels recorded using the fast shutter speed camera, that allows to draw a further conclusions about the specifics of the maldistribution process. The impact of the total pressure drop on the actual range of optimum operating conditions of the heat exchanger was analyzed.
EN
The disposal of ash in a thermal plant through the slurry pipe is subjected to some erosion wear due to the abrasive characteristics of the slurry. A simulation study of particle-liquid erosion of mild steel pipe wall based on CFD-FLUENT that considers the solid-liquid, solid-solid and solid-wall interaction is presented in this work.The multi-phase Euler-Lagrange model with standard k- ϵ turbulence modeling is adopted to predict the particulate erosion wear caused by the flow of bottom ash water suspension. Erosion rate for different particle size and concentration is evaluated at variable flow rate. It is observed that the pressure drop and erosion rate share direct relationships with flow velocity, particle size and concentration. The flow velocity is found to be the most influencing parameter. A model capable of predicting the erosion wear at variable operating conditions is presented.The simulation findings show good agreement with the published findings.
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