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EN
The unmanned underwater tracked bulldozer (UUTB) is an indispensable equipment for dredging and cleaning obstacles on the river bed in the flood season. The investigation on the interaction properties between the UUTB tracks and sediments provides foundation for the evaluation of operation performance when it works on the inland river bed. Based on the current worldwide research, the sediments mixed by sand, bentonite and water with sand content 0%, 10% and 20% were configured in this study to replace the real sediments on the inland river bed in China. The current pressure-sinkage model and shear stress-shear displacement model were discussed. Three different tracks were tested for the pressure-sinkage and the shear stress-shear displacement on the platform. The relationship between pressure and sinkage under sand content 0%, 10% and 20% are revealed based on the experimental results. The modulus of cohesive deformation and friction deformation of the sediments under said sand content are presented. The curves of shear stress and shear displacement are also obtained, which demonstrates the properties between the tracks and configured sediments under sand content 0%, 10% and 20%. The relationship between the tractive force and slip ratio with three different tracks under said sand content is also presented based on the quantitative analysis, which provides reference for the dynamics control and performance evaluation of UUTB on the inland river bed.
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 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
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
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%.
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.
PL
Przeprowadzono gruntowny przegląd literatury na temat korelacji spadku ciśnienia, opracowano bank danych doświadczalnych obejmujący szeroki zakres zmian parametrów przepływowych oraz dokonano weryfikacji możliwości przewidywania wartości spadków ciśnienia w przepływach dwufazowych gaz-ciecz w minikanałach. Porównano wartości spadków ciśnienia obliczone zgodnie z dostępnymi w literaturze korelacjami z wartościami eksperymentalnymi. Analiza uzyskanych wyników obliczeń wykazała, że większość korelacji ma bardzo ograniczony zakres ważności i nie opisuje danych doświadczalnych z zadowalającą dokładnością. Zaproponowano równania do obliczania spadku ciśnienia w przepływie w minikanałach, i to niezależnie od rodzaju przepływu.
EN
Fundamentals and a review, with 17 refs., of pressure drop correlations and exp. pressure drop data. Performance of the correlations in correctly predicting the diverse data sets was verified. Most of the correlations developed are very restricted in terms of handling a wide variety of data sets.
10
Content available Bubble boiling in flow of refrigerating media
EN
The paper describes results of investigations of heat transfer and pressure drop during bubbly boiling of refrigerating media. In this article were presented of authors own experimental studies and were proposed new simple calculation model describing bubble boiling in the tubular channel. The author attempts to put forward a simplified description of the process of bubble boiling in a straight pipe. The two-phase one-component (liquid-vapour) system is treated as a continuum governed by the laws of conservation of energy, momentum and mass. The continuum is characterised by parameters that describe the two-phase system, such as density of the two-phase mixture, static void fraction or static equilibrium dryness fraction. In view of engineering applications, a one-dimensional model is used where physical quantities are cross-section averaged. This way the average velocity, pressure, temperature, and so on, are introduced. The results of the proposed model have been compared with the results of the experimental research with satisfactory compliance.
EN
This article presents the results of experimental research of R404A, R407C and R410A high-pressure refrigerants condensation in vertical pipe microchannels with an internal diameter dw below 1 mm. The study determined the local and average heat transfer coefficient in the full range of vapor quality, x = 1-0. On the basis of experimental investigations, the dependence of heat transfer coefficient on the vapor quality x, the mass flux density G and the channel internal diameter dw was obtained.
PL
Istnieje wiele algorytmów matematycznych, których głównym zadaniem jest określenie spadku ciśnienia w gazociągu przesyłowym. W artykule zostały dokładnie przeanalizowane najczęściej stosowane na świecie algorytmy do obliczenia spadku ciśnienia w gazociągach przesyłowych, a uzyskane wyniki obliczeniowe porównano z rzeczywistymi. W artykule przedstawiono wpływ poszczególnych modułów obliczeniowych na dokładność wybranych modeli matematycznych do wyznaczenia spadku ciśnienia w gazociągach przesyłowych.
EN
There are many mathematical algorithms, whose main task is to determine the pressure drop in the transmission pipeline. In the article was carefully analyzed the most used in the world algorithms to calculate pressure drop in transmission pipelines, and the obtained results were compared with actual data. In the article present impact of deferent algorithms on the accuracy of the selected mathematical models to calculation of pressure drop in transmission pipelines.
EN
Analysis of the state of-the-art in research of minichannel heat exchangers, especially on the topic of flow maldistribution in multiple channels, has been accomplished. Studies on minichannel plate heat exchanger with 51 parallel minichannels with four hydraulic diameters, i.e., 461 μm, 574 μm, 667 μm, and 750 μm have been presented. Flow at the instance of filling the microchannel with water at low flow rates has been visualized. The pressure drop characteristics for single minichannel plate have been presented along with the channels blockage, which occurred in several cases. The impact of the mass flow rate and channels’ cross-section dimensions on the flow maldistribution were illustrated.
EN
Investigations of refrigerant condensation in pipe minichannels are very challenging and complicated issue. Due to the multitude of influences very important is mathematical and computer modeling. Its allows for performing calculations for many different refrigerants under different flow conditions. A large number of experimental results published in the literature allows for experimental verification of correctness of the models. In this work is presented a mathematical model for calculation of flow resistance during condensation of refrigerants in the pipe minichannel. The model was developed in environment based on conservation equations. The results of calculations were verified by authors own experimental investigations results.
EN
Experimental investigation was conducted on the thermal performance and pressure drop of a convective cooling loop working with ZnO aqueous nanofluids. The loop was used to cool a flat heater connected to an AC autotransformer. Influence of different operating parameters, such as fluid flow rate and mass concentration of nanofluid on surface temperature of heater, pressure drop, friction factor and overall heat transfer coefficient was investigated and briefly discussed. Results of this study showed that, despite a penalty for pressure drop, ZnO/water nanofluid was a promising coolant for cooling the micro-electronic devices and chipsets. It was also found that there is an optimum for concentration of nanofluid so that the heat transfer coefficient is maximum, which was wt. % = 0.3 for ZnO/water used in this research. In addition, presence of nanoparticles enhanced the friction factor and pressure drop as well; however, it is not very significant in comparison with those of registered for the base fluid.
EN
The paper presents a numerical analysis of pressure drop and acoustic attenuation performance (transmission loss) of two identical acoustic helicoidal resonators arranged in parallel ducts with different rotation angles. The air stream is divided from one cylindrical duct of a diameter D=140mm to a two parallel cylindrical ducts of diameter d=125mm with two helicoidal resonators inside – one per one duct. The ratio of helicoidal pitch s of helicoidal resonators to a cylindrical duct diameter d equals s/d=1,976. Other geometrical relationships of helicoidal resonators, as a mandrel diameter dm to duct diameter ratio dm/d=0.024, thickness g of helicoidal profile g/d=0.0024, and the number of helicoidal turn n=0,695 for both resonators. The investigated range of rotation angles covered the three characteristic positions of helicoidal resonators gaps, when considering the air stream distribution from central large duct with diameter D. The value of normal inflow velocity v[m/s] equaled 1 for all investigated cases.
PL
W artykule przedstawiono prosty model matematyczny wymiany ciepła oraz modyfikacji spadku ciśnienia w kanale, w którym uwzględniono modyfikację charakterystyki cieplno-przepływowej wymiennika na skutek zatykania się kanałów. Model porównano z własnymi danymi eksperymentalnymi prototypu wymiennika mikrokanałowego. Model ten jest szczególnie użyteczny w przypadku konieczności oceny pracy wymiennika, w którym występuje zagadnienie jego zatykania się, bez konieczności rozbierania takiego wymiennika. Jest to zatem nieniszcząca metoda wyznaczenia stopnia zatkania kanalików wymiennika.
EN
In the paper a simple mathematical model of heat transfer and flow resistance is given for heat exchangers with partially blocked channels. The predictions are compared with own experimental data for a prototype micro channel heat exchanger. Presented model is particularly useful for evaluation of a heat exchanger performance with partially blocked channels without its dismantling. Determination of the blockage degree is then possible with this model.
18
Content available remote Diagnozowanie rurociągów
PL
Przedstawiono filozofię budowania relacji diagnostycznych w oparciu o potencjał eksploatacyjny węzłów zespołów funkcjonalnych. Przedstawiono odcinek rurociągu jako węzeł hydrodynamiczny. Wymieniono miary potencjału eksploatacyjnego odcinka rurociągu. Opisano relacje potencjał eksploatacyjny odcinka rurociągu – spadek ciśnienia na odcinku rurociągu i relacje spadek ciśnienia na przeszkodzie w rurociągu - emisja akustyczna w otoczeniu przeszkody w rurociągu.
EN
The philosophy of building diagnostic relationships based on the were margin of functional units nodes is presented. A pipeline section is presented as a hydrodynamic node. The measure of wear margin of pipeline section has been listed. The relationships wear margin of pipeline section – loss of pressure along the pipeline section and relationships loss of pressure in obstacle in the pipeline - acoustic emission around the obstacle in the pipeline has been described.
19
Content available remote Prognozowanie pracy sieci gazowej za pomocą sztucznych sieci neuronowych
PL
Podczas wprowadzania ograniczeń w dostawach gazu ziemnego przedsiębiorstwa przemysłowe odczuwają problemy z zaopatrzeniem w gaz, co przekłada się na ich sytuację finansową. W takim przypadku, zakładając rozwój liberalizacji na rynku gazu ziemnego, może nastąpić spadek cen paliw gazowych. Gospodarstwa domowe, które korzystają z gazu w celach komunalnych (ogrzewanie budynków) oraz bytowych (przygotowanie posiłków i ogrzewanie wody) z mocy prawa są chronione w razie zakłóceń dostaw gaz ziemnego. Wystąpienie zakłóceń (nieodpowiednia kaloryczność gazu) i braków dostaw gazu ziemnego może skłonić także wielu użytkowników z tej najliczniejszej grupy do rezygnacji z korzystania z paliw gazowych. Niniejszy artykuł przedstawia możliwości prognozowania pracy sieci gazowej średniego ciśnienia. Analizowanym parametrem jest spadek ciśnienia gazu dostarczanego do odbiorców domowych przyłączonych do systemu sieci dystrybucyjnej. Dzięki uzyskanym pomiarom przepływu gazu, temperatury oraz spadku ciśnienia możliwe będą analizy wykorzystujące wzory matematyczne, program STANET oraz uczenie z wykorzystaniem sztucznej sieci neuronowej. Otrzymane wyniki dają możliwość porównania poszczególnych metod w 20-godzinnym przewidywaniu zmian ciśnienia gazu.
EN
During the introduction of restrictions in the supply of natural gas, industrial enterprises experience problems with the supply of gas, which is reflected in their financial situation. In this case, given the development of the liberalization of the natural gas market, there may be a decline in prices of gas. Households that use gas for utility purposes (heating of buildings) and living (preparing meals and heating water) by law are protected in the event of disruption in the supply of natural gas. Any disruptions such as the inadequate calorific value of gas and shortages of natural gas supplies may also induce many users from the largest group to abandon the use of gaseous fuels. The following article introduces possibilities concerning the forecast of how medium-pressure gas network, works. The parameter which is analyzed is the decrease in the gas pressure supplied to households connected to the distribution network system. The measurements (gas flow, temperature and the decrease in the pressure) will enable analysis using mathematical formulas, STANET software and the model of artificial neural network. The results will enable a comparison of particular methods in a twenty-hour forecasting of changes in gas pressure.
20
Content available remote Rozdział emulsji woda-olej napędowy przy użyciu mikrofiltrów
PL
Przedstawiono wyniki badań doświadczalnych rozdziału emulsji woda-olej napędowy. Do rozdziału emulsji wykorzystano mikro-filtry o średnicy por 30 pm: polipropylenowy (PP 30) oraz poliamidowy (NN30). W przypadku filtra poliamidowego dominował mechanizm wychwytywania kropel wody przez włókna filtra. W filtrze polipropylenowym funkcjonował mechanizm zderzania kropel wody między sobą oraz o włókna filtra, w wyniku czego powstawały większe krople, łatwiejsze do oddzielenia od fazy ciągłej. Różny mechanizm rozdziału emulsji wpływał na czas trwania procesu oraz na spadki ciśnienia podczas przepływu emulsji przez mikrofiltr.
EN
Results of experimental investigation on water-diesel fuel emulsion separation are presented in the paper. Microfilters of 30 pm pore diameter made of polypropylene (PP 30) and polyamide (NN30) were applied in emulsion separation. Different mechanisms of separation in filters made of different materials were observed. In case of polyamide filter dominates the mechanism of water droplet capture by filter fibers. In case of polypropylene filter the coalescence of droplets is mainly caused by impact of droplet into another droplet or a fiber. It leads to the formation of bigger droplet that can be easily separated from the continuous phase. A different mechanism of emulsion separation influences the separation time and determines the pressure drop in liquid during its flow through the niter.
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