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1

Utilizing of the Statistical Analysis for Evaluation of the Properties of Green Sand Mould

Abdulamer Dheya

Archives of Foundry Engineering

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2023

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Vol. 23, iss. 3

67--73

EN

A statistical approach was conducted to investigate effect of independent factors of the mixing time compactability and bentonite percentage on dependent variables of permeability, compression and tensile strength of sand mould properties. Using statistical method save time in estimating the dependent variables that affect the moulding properties of green sand and the optimal levels of each factor that produce the desired results. The results yielded indicate that there are variations in the effects of these factors and their interactions on different properties of green sand. The outcomes obtained a range of permeability values, with the highest and lowest numbers being 125 and 84. The sand exhibited high values of tensile and compressive strength measuring at 0.33N/cm2 and 17.67N/cm2 . Conversely it demonstrated low levels of tensile and compressive strength reaching 0.14N/cm2 and 9.32N/cm2 . These results suggest that the moulding factors and their interactions have an important role in determining properties of the green sand. ANOVA was used to assess effect of various factors on different properties of the green sand. The results obtained suggest that compactability factor play a significant effect on permeability, the mixing time or bentonite factor has a significant effect on the compressive strength and mixing time or compactability factor has a significant impact on the tensile strength with a significance level lower than 5%. It is found that neither the mixing time nor the amount of bentonite used in the green sand mix has a significant impact on its permeability. Compactability of the green sand does not has a significant effect on the compressive strength. Bentonite used in green sand mix does not have a significant impact on its tensile strength.

2

Evaluation of Mixing Efficiency and How it Affects the Properties of the New Green Sand Mixtures

Kielar Šimon, Bašistová Martina, Lichý Petr

Archives of Foundry Engineering

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2023

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Vol. 23, iss. 3

88--93

EN

The current trend in the preparation of green sand mixtures emphasizes the acceleration of the mixing process while maintaining the quality of the mixture. This requirement results in the necessity of determining the optimal conditions for mixing the mixture with a given mixer. This work aims to determine the optimal mixing conditions for the newly introduced eddy mixer LM-3e from the company Multiserw-Morek in the sand laboratory at the Department of Metallurgical Technologies, Faculty of Materials and Technology, VŠB - Technical University of Ostrava. The main monitored properties of mixtures will be green compressive strength and moisture of the mixture. The measured properties of the mixture mixed on the eddy mixer will be compared with the properties of the mixture mixed on the existing LM-2e wheel mixer. The result of the experiment confirmed that the eddy mixer is suitable for the preparation of a mixture of the same quality as the wheel mixer but with a significantly reduced mixing time.

3

No cutoff for circulants : an elementary proof

Abrams Aaron, Landau Henry, Pommersheim Jamie, Babson Eric, Landau Zeph

Probability and Mathematical Statistics

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2022

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Vol. 42, Fasc. 1

97--108

EN

We give an elementary proof of a result due to Diaconis and Saloff-Coste (1994) that families of symmetric simple random walks on Cayley graphs of abelian groups with a bound on the number of generators never have sharp cutoff. Here convergence to the stationary distribution is measured in the total variation norm. This is a situation of bounded degree and no expansion; sharp cutoff (or the cutoff phenomenon) has been shown to occur in families such as random walks on a hypercube (Diaconis, 1996) in which the degree is unbounded as well as on a random regular graph where the degree is fixed, but there is expansion (Diaconis and Saloff-Coste, 1993).

4

Some experimental studies concerning mixing of loose and liquid agricultural materials

Barwicki Jan, Roman Kamil, Borek Kinga, Mazur Kamila, Wardal Witold Jan, Kierończyk Marek

Inżynieria Materiałowa

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2021

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Vol. 42, nr 4-5

18--20

EN

In the study some experimental research concerning mixing process loose and liquid agricultural products were presented. The research is concerned the following aspects of the study: the theory of the mixing process, the trajectory of movement of the molecules involved in the mixing process, the forces affecting the structural elements of the mixers, the types of mass flow of mixed components, the method of assessing the degree of mixing of the components and the energy demand during mixing with the use of various design solutions of the mixers.

PL

W pracy przedstawiono wybrane badania eksperymentalne dotyczące procesu mieszania sypkich i płynnych produktów rolniczych. Badania dotyczą takich aspektów pracy, jak: teoria procesu mieszania, trajektoria ruchu cząsteczek biorących udział w procesie mieszania, siły działające na elementy konstrukcyjne mieszadeł, rodzaje przepływu masowego mieszanych składników, metoda oceny stopnia wymieszania składników i zapotrzebowania na energię podczas mieszania z wykorzystaniem różnych rozwiązań konstrukcyjnych mieszadeł.

5

Studies of a mixing process induced by a rotating magnetic field with the application of magnetic particles

Rakoczy Rafał, Kordas Marian, Markowska-Szczupak Agata, Konopacki Maciej, Augustyniak Adrian, Jabłońska Joanna, Paszkiewicz Oliwia, Dubrowska Kamila, Story Grzegorz, Story Anna, Ziętarska Katarzyna, Sołoducha Dawid, Borowski Tomasz, Roszak Marta, Grygorcewicz Bartłomiej, Dołęgowska Barbara

Chemical and Process Engineering

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2021

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Vol. 42, nr 2

157-–172

EN

We demonstrate in this study that a rotating magnetic field (RMF) and spinning magnetic particles using this kind of magnetic field give rise to a motion mechanism capable of triggering mixing effect in liquids. In this experimental work two mixing mechanisms were used, magnetohydrodynamics due to the Lorentz force and mixing due to magnetic particles under the action of RMF, acted upon by the Kelvin force. To evidence these mechanisms, we report mixing time measured during the neutralization process (weak acid-strong base) under the action of RMF with and without magnetic particles. The efficiency of the mixing process was enhanced by a maximum of 6.5% and 12.8% owing to the application of RMF and the synergistic effect of magnetic field and magnetic particles, respectively

6

High flow, low shear impellers versus high shear impellers; dispersion of oil drops in water and other examples

Pacek Andrzej W., Nienow Alvin W.

Chemical and Process Engineering

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2021

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Vol. 42, nr 2

77–-90

EN

Flow patterns generated by two ChemShear impellers, CS 2 and CS 4 have been measured and flow numbers calculated; Fl = 0.04 for both impellers. Transient and equilibrium drop sizes, d32 μm of 3 different viscosity silicone oils agitated by a high-shear Rushton turbine, RT, a low-shear, high-flow HE3 impeller and the two ChemShears were determined. The equilibrium d32 are correlated for all impellers, by d32 = 1300(εT )−0.58 max.svv0.14 with an R2 = 0.94. However, the time to reach steady state and the equilibrium size at the same specific power do not match the above descriptors of each impeller’s characteristics. In other literature, these descriptors are also misleading. In the case of mixing time, a high shear RT of the same size as a high flow HE3 requires the same time at the same specific power in vessels of H/T = 1. In bioprocessing, where concern for damage to cells is always present, free suspension animal cell culture with high shear RTs and low-shear impellers is equally effective; and with mycelial fermentations, damage to mycelia is greater with low shear than high. The problems with these descriptors have been known for some time but mixer manufacturers and ill-informed users and researchers continue to employ them.

7

Analysis of liquid blending dynamics with Maxblend impellers by Electrical Resistance Tomography

Iwasawa Suzuka, Kubo Honami, Takenaka Katsuhide, Pintus Sandro, Maluta Francesco, Montante Giuseppina, Paglianti Alessandro

Chemical and Process Engineering

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2021

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Vol. 42, nr 3

197-–207

EN

The aim of the investigation was liquid mixing time measurement in a laboratory scale stirred tank equipped with a metal Maxblend impeller and comparison with the corresponding mixing time obtained with other conventional impellers. The data are collected by Electrical Resistance Tomography, whose applicability in this case is non-trivial, because of the electrical interferences between the large paddles of the impeller and the measuring system. The raw data treatment methodology purposely developed for obtaining the homogenization dynamics curve is presented. A robust approach for a fine and low cost investigation of the mixing performances of close-clearance impellers in opaque systems is suggested. The analysis of the local and averaged conductivity time traces reveals the effect of important variables, such as the fluid viscosity and the vessel configuration, on the mixing time under various agitation conditions. The data collection and post processing procedures open the way to the application of the technique to multiphase and non-Newtonian fluids stirred with close-clearance impellers.

8

Agitation efficiency of different physical systems

Karcz Joanna, Szoplik Jolanta, Major-Godlewska Marta, Cudak Magdalena, Kiełbus-Rąpała Anna

Chemical and Process Engineering

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2021

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Vol. 42, nr 2

139–-156

EN

Efficiency of agitation was considered for different physical systems on the basis of our own experimental studies on homogenisation, heat and mass transfer as well as gas hold-up. Measurements were performed for different physical systems: Newtonian liquids of low and higher viscosity, pseudoplastic liquid, gas–liquid and gas–solid–liquid systems agitated in vessels of the working volume from 0.02 m3 to 0.2 m3. Agitated vessels of different design were equipped with a high-speed impeller (10 impellers were tested). Comparative analysis of the experimental results proved that energy inputs (power consumption) should be taken into account as a very important factor when agitation efficiency is evaluated in order to select a proper type of equipment. When this factor is neglected in the analysis, intensification of the process can be estimated only.

9

Investigation of mixing time in liquid under influence of rotating magnetic field

Przybył A., Rakoczy R., Konopacki M., Kordas K., Drozd R., Fijałkowski K.

Chemical and Process Engineering

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2017

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Vol. 38, nr 4

555--565

EN

The aim of the study was to present an experimental investigation of the influence of the RMF on mixing time. The obtained results suggest that the homogenization time for the tested experimental set-up depending on the frequency of the RMF can be worked out by means of the relationship between the dimensionless mixing time number and the Reynolds number. It was shown that the magnetic field can be applied successfully to mixing liquids.

10

Strong stationary duality for Möbius monotone Markov chains : examples

Lorek P., Szekli R.

Probability and Mathematical Statistics

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2016

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Vol. 36, Fasc. 1

75--97

EN

We construct strong stationary dual chains for nonsymmetric random walks on square lattice, for random walks on hypercube and for some Ising models on the circle. The strong stationary dual chains are all sharp and have the same state space as original chains.We use Möbius monotonicity of these chains with respect to some natural orderings of the corresponding state spaces. This method provides an alternative way to study mixing times for studied models.

11

Badania hydrodynamiki w kolumnie air-lift z zewnetrzna cyrkulacja płynu

Szoplik J., Stelmasińska P.

Inżynieria i Aparatura Chemiczna

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2015

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Nr 6

360--361

PL

Analizowano udział gazu zatrzymanego w cieczy w strefie wznoszenia i opadania, prędkość cieczy w strefie wznoszenia i opadania oraz czas mieszania w kolumnie air-lift z zewnętrzną cyrkulacją płynu. Badano układy woda-powietrze oraz roztwór gliceryny-powietrze dla różnych objętościowych strumieni powietrza. Wykazano, że w zakresie przeprowadzonych pomiarów typ układu ciecz-gaz miał wpływ na prędkość cieczy w strefie wznoszenia i opadania oraz czas mieszania, a nie wpływał istotnie na wielkość udziału gazu zatrzymanego w cieczy.

EN

The gas hold-up and liquid velocity in a riser and downcomer as well as mixing time in the external-loop airlift reactor were analyzed. Two systems: air – water and air – glycerol in water solution for various volumetric gas flow rates were investigated. It was proved that in the range of performed measurements a type of gas – liquid phase affects the liquid velocity in a riser and downcomer and mixing time but does not significantly affects gas hold-up.

12

The analysis of the ECFM-3Z combustion model in the marine 4-stroke engine for the exhaust gas composition

Kowalski J.

Journal of Polish CIMAC

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2014

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Vol. 9, no 1

95--102

EN

The paper presents ECFM-3Z combustion model analysis in the marine, 4-stroke diesel engine. The purpose of the modeling was to determine the composition of the exhaust gas. This composition depends on the composition of the combustible mixture, combustion time and thermodynamic conditions prevailing in the engine cylinder during the working process. Mentioned parameters are variable in time and space, and therefore require the use of 3-dimensional model based on the finite volume method, taking into account the fuel injection, brake-up and evaporation, mixing with air, auto-ignition and combustion. All models presented in the literature are adapted to the parameters of relatively small engines. Different marine engine parameters require significant modifications taking into account the heat exchange with the structural elements of the engine, leakage through piston rings and energy losses by riction. It should also be noted that dimensions of the marine engine require careful optimization of spatial moving meshes according to computation time and quality of results. Paper presents influence of mixing time, start of injection and autoignition delay on modeling results of the exhaust gas composition.

13

Studies of a mixing process by using the various types of magnetic particles as active micro-stirrers

Konopacki M., Frąckowiak A., Tabero P., Fijałkowski K., Rakoczy R.

Czasopismo Techniczne. Chemia

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2014

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R. 111, z. 2-Ch

45--54

EN

The main purpose of this report is to present the effect of various types of magnetic particles on the mixing time. The magnetic particle may be treated as a miniaturized mixer and it may offer a unique, alternative approach to mixing. The obtained results suggest, that the mixing time under the rotating magnetic field (RMF) may be worked by using the relation between the mixing time number and the modified Reynolds number.

PL

Głównym celem pracy jest przedstawienie wyników dotyczących procesu mieszania z zastosowaniem wirującego pola magnetycznego i cząstek magnetycznych. Uzyskane wyniki zostały przedstawione w formie relacji wiążącej bezwymiarowy czas mieszania i modyfikowaną liczbę Reynoldsa.

14

Mixing characteristics for gas-liquid system in an external-loop air-lift column

Musiał M., Bitenc M., Karcz J.

Czasopismo Techniczne. Chemia

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2014

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R. 111, z. 2-Ch

105--114

EN

This paper presents the results of the experimental investigations of hydrodynamics for an external-loop air-lift column. Process characteristics (gas hold-up, liquid velocities, liquid circulation time and mixing time) were analyzed as a function of the modified Froude number. The obtained results were presented graphically and in the form of the quantitative correlations.

PL

W tym artykule przedstawiono wyniki doświadczalnych badań hydrodynamiki dla kolumny air-lift z zewnętrzną cyrkulacją płynu. Charakterystyki procesowe (udział gazu zatrzymanego w cieczy, prędkości płynu, czas cyrkulacji oraz czas mieszania) analizowano w funkcji zmodyfikowanej liczby Froude’a. Wyniki badań opracowano graficznie i matematycznie.

15

Porównanie sposobów zwiększenia efektywności mieszania płynów lepkich w mieszalniku z dwoma mieszadłami

Woziwodzki S., Broniarz-Press L., Jędrzejczak Ł, Zaworska K

Inżynieria i Aparatura Chemiczna

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2013

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Nr 4

378--379

PL

W pracy podjęto próbę porównania efektywności mieszania w mieszalniku z niecentrycznie umiejscowionymi mieszadłami oraz w mieszalniku z mieszadłami wykonującymi ruch oscylacyjny typu forward-reverse. Stwierdzono, iż stopień segregacji maleje wraz ze wzrostem czasu mieszania. Porównanie czasów mieszania dla obu sposobów mieszania pozwala stwierdzić, iż najmniejszy czas mieszania uzyskano dla układów RT-RT i RT-PBT (forward-reverse, Re= 9 i 29) oraz dla układu PBT-PBT (układ niecentrycz- ny, Re = 40). Wyższa efektywność mieszania typu forward-reverse zanika dla Re > 40.

EN

In the work an attempt was undertaken to compare the mixing effectiveness of in a vessel with eccentrically located impellers and in a vessel with impelers performing oscillatory (forward-reverse) motion. The results showed that fourfold increase in frequency causes the decrease of mixing time. Comparison of mixing time periods leads to the conclusion that the smallest mixing time was achieved for the RT-RT and RT-PBT systems (forwardreverse, Re = 9 and 29) and for the PBT-PBT system (eccentric system, Re = 40). A higher efficiency of forward-reverse mixing in comparison the eccentric system disappears for Re > 40.

16

Analiza wpływu mieszania na właściwości fizykochemiczne roztworów wodnych saponin uzyskiwanych w procesie ich wielokrotnego uwalniania z orzeszków piorących

Broniarz-Press L., Dulska D., Szaferski W.

Przemysł Chemiczny

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2011

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T. 90, nr 9

1625-1627

17

Wpływ mieszania na zmianę właściwości powierzchniowo czynnych roztworów saponin zawartych w owocach Sapindus mukorossi

Broniarz-Press L., Dulska D., Szaferski W.

Inżynieria i Aparatura Chemiczna

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2010

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Nr 3

25-26

PL

Występujące w przyrodzie surfaktanty, których przykładem są saponiny, mogą być wykorzystywane w gospodarstwach domowych i na skalę przemysłową ze względu na łatwą i ekonomiczną wydajność. W pracy przedstawiono wyniki badania wpływu czasu mieszania na wartość napięcia powierzchniowego saponin zawartych w orzeszkach piorących. Uzyskane wyniki wartości napięcia powierzchniowego są porównywalne z wartościami literaturowymi dla czystych saponin. Z punktu widzenia technologicznego 24-krotne obniżenie czasu ekstrakcji świadczy o przewadze zastosowanej : metody dynamicznej w stosunku do statycznej.

EN

Natural surfactants, e.g. saponins, can be very useful in households and in industry due to accessibility and economical efficiency. Soap nuts containing saponins are completely natural detergents. Results of mixing effect on surface tension in water solution of soap nuts are presented in the paper. The results of experimental studies showed that values of surface tension for Sapindus saponins are comparable with the ones suggested in literature. Two dozen shorter extraction time proved the dynamic method superiority over the static one.

18

Wpływ dodatku soli na czas mieszania w roztworach polimerów

Różańska S., Broniarz-Press L.

Inżynieria i Aparatura Chemiczna

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2010

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Nr 1

95-96

PL

W pracy przedstawiono wyniki badań doświadczalnych czasu mieszania w wodnych roztworach polimerów jonowych i niejonowych (soli sodowej karboksymctylocelulozy, częściowo zhydrolizowanego poHakryloamidu oraz gumy guar) w czystej wodzie i z dodatkiem soli (NaCl). Czas mieszania wyznaczano za pomocą opracowanej w tym celu metody optycznej. Analiza danych Teologicznych wykazała, że dodatek soli powoduje obniżenie lepkości roztworów polielektrolitów, co wpływa na skrócenie czasu mieszania.

EN

The paper deals with experimental studies on the determination of mixing time for ionic and non-ionic polymer solutions (carboxymetyhylcellulose sodium salt, partially hydrolyzed polyacrylamide and guar gum) in clear water and with salt additives. The optical method was applied to evaluate mixing time in fluids studied. Analysis of rhcological data showed that salt causes a decrease of viscosity of polyelectrolyte solutions, what as a result influences mixing time shortening.

19

Czas mieszania w micelarnych roztworach środków powierzchniowo czynnych dla mieszadeł trubinowych

Broniarz-Press L., Różańska S., Różański J.

Inżynieria i Aparatura Chemiczna

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2009

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Nr 1

86-87

PL

W pracy przedstawiono wyniki badań nad czasem mieszania kationowych środków powierzchniowo czynnych w mieszalniku wyposażonym w mieszadła turbinowe o różnej konstrukcji. W badaniach zastosowano kationowe środki powierzchniowo czynne: bromek tetradecylotri-metyloamoniowy oraz chlorek heksadecylotrimetyloamoniowy. Jako dodatek wspomagający proces asocjacji micelarnej zastosowano salicylan sodu.

EN

The results of studies on the mixing time for cationic surfactant solutions in an agitated vessel equipped with turbine impellers of different construction are presented in the paper. Aqueous solutions of cationic surfactant such as tetradecyltrimethylammonium bromide and hek-sadecyltrimethylammonium chloride wen' used in measurements. Sodium salicylate was applied as an additive promoting the micellar association process.

20

Modelowanie przepływu stali w kadzi pośredniej urządzenia cos w stalowni Baildon Gonar-Bis sp. z o.o.

Merder T., Pieprzyca J., Kudliński Z., Bulkowski L., Galiasz U., Kania H.

Hutnik, Wiadomości Hutnicze

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2009

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Vol. 76, nr 3

178-184

PL

Celem badań było zdiagnozowanie warunków hydrodynamicznych występujących w kadzi pośredniej, stosowanej w stalowni Baildon Gonar-Bis. Analizowany obiekt to kadź pośrednia typu "T". Nominalna pojemność kadzi 7,5 Mg ciekłej stali. W związku Z tym podjęto działania zmierzające do określenia szczegółowych charakterystyk pracy obiektu. W kadzi rozpatrywano różne zabudowy urządzeniami sterującymi przepływem (UPS). W niniejszej pracy przedstawiono wyniki badań modelowych (fizycznych I numerycznych) identyfikujące charakterystyki przepływowe w kadzi pośredniej.

EN

The objective of the study is to diagnose the current condition of the tundish currently used In the steelworks Baildon Gonar-Bis. The investigated object is a 'T'-type tundish. The nominal capacity of the tundish is 7.5 Mg of liquid steel. Instigations were undertaken to determine the detailed characteristics of the working conditions of the facility. Different flow control devices configurations in tile tundish were tested. The present work include results of both, physical and numerical models that identify the flow characteristics in a tundish.