The article presents the results of permeability measurements of a zirconium alcohol coating applied on moulds and cores. The introduction extensively discusses the reasons for the application of protective coatings, as well as their advantages and disadvantages. Also, the problems related to the application of protective coatings are presented i.e. limited permeability and thus the possibility of the presence of gas-originated defects in the casts. Next, the paper discusses the methods of measuring the permeability of protective coating proposed by Falęcki and Pacyniak. The study also presents an indirect permeability measurement method. For the investigations, zirconium alcohol coatings with the three conventional viscosities 10, 20 and 30s were used. The viscosity was determined by means of the Ford cup with the clearance of 4mm. The coatings were applied onto profiles of Φ 50 x 50 mm, made of moulding sand consisting of a sand matrix with the mean grain size of dL = 0,11, 17, 24, 31 and 34 mm and phenol-formaldehyde resin. The effect of the matrix grain size on the permeability of the sand with and without a coating was determined.
The flow of a viscous incompressible fluid in small gaps hydraulic devices and devices based on the hop boundary changes in viscosity. For the distribution model adopted dynamic viscosity was integrate the equations of fluid motion, whereby expressions are obtained for the velocity of the liquid height of the gap. The expressions for calculation of the fall capacity flow section are determined. Examples of the calculation of distributions velocity and falling bandwidth to a narrow gap are given.The estimation of the limits of applicability of classical approach to the calculation of viscous flow in micro gap is executed.
The study presents the possible use of optoelectronic system for the measurement of values specific for hydrodynamics of two-phase gas very-high-viscosity liquid flow in vertical pipes. An experimental method was provided, and the findings were presented and analysed for selected values which characterise the two-phase flow.
In this study the results of simultaneous measurements of dynamic viscosity, thermal conductivity, electrical conductivity and pH of two nanofluids, i.e., thermal oil/Al2O3and thermal oil/TiO2are presented. Thermal oil is selected as a base liquid because of possible application in ORC systems as an intermediate heating agent. Nanoparticles were tested at the concentration of 0.1%, 1%, and 5% by weight within temperature range from 20°C to 60°C. Measurement devices were carefully calibrated by comparison obtained results for pure base liquid (thermal oil) with manufacturer’s data. The results obtained for tested nanofluids were compared with predictions made by use of existing models for liquid/solid particles mixtures.
The nanocomposites based on water glass matrix were attempted in the study. Nanoparticles of ZnO, Al2O3 or MgO in organic solutions were applied into water glass matrix in the amounts of: 1.5; 3; 4 or 5 mas. %. Wettability of the quartz sad by the nanocomposites based on water glass matrix was determined by testing changes of the wetting angle θ in time τ for the system: quartz – binder in non-stationary state, by means of the device for measuring wetting angles. Wettability measurements were carried out under isothermal conditions at an ambient temperature (20 – 25 oC). The modification improves wettability of quartz matrix by water glass, which is effective in improving strength properties of hardened moulding sands. Out of the considered modifiers in colloidal solution of propyl alcohol water glass modified by MgO nanoparticles indicated the smallest values of the equilibrium wetting angle θr. This value was equal app. 11 degrees and was smaller no less than 40 degrees than θr value determined for not modified water glass. Viscosity η of nanocomposites based on water glass matrix was determined from the flow curve, it means from the empirically determined dependence of the shearing stress τ on shear rate γ: τ = f (γ) (1), by means of the rotational rheometer. Measurements were carried out at a constant temperature of 20 oC. The modification influences the binder viscosity. This influence is conditioned by: amount of the introduced modifier as well as dimensions and kinds of nanoparticles and organic solvents. The viscosity increase of the modified binder does not negatively influence its functional properties.
An axially symmetric, gravity driven, steady flow of a grounded polar ice sheet with a prescribed temperature field is considered. The ice is treated as an incompressible, non-linearly viscous, anisotropic fluid, the internal structure (fabric) of which evolves as ice descends from the free surface to depth in an ice sheet. The evolution of the ice fabric is described by an orthotropic constitutive law which relates the deviatoric stress to the strain-rate, strain, and three structure tensors based on the current (rotating) principal stretch axes. The solution of the problem is constructed as a leading-order approximation derived from asymptotic expansions in a small parameter that reflects the small ratio of stress and velocity gradients in the lateral direction of the ice sheet to those in the thickness direction. Numerical simulations of the flow problem have been carried out for various sets of rheological parameters defining the limit strength of the anisotropic fabric in ice. The results of calculations illustrate the influence of the ice anisotropy, basal melt conditions and temperature field in ice on the glacier thickness and lateral span, and on the depth profiles of the flow velocity.
Longitudinal and shear ultrasonic wave velocities were measured versus temperature in the viscosity standards of Paragon S8000S, N30000S and Cannon N2700000. The measurements were performed by the through-transmission method at the frequency of 2 MHz. Ultrasonic pulses were sent via polymethyl methacrylate (PMMA) waveguides between the tips of which a small amount of the particular standard liquid was placed. The velocities of longitudinal and shear waves were determined to depend on the viscosity of the liquid and increase with the viscosity.
In this paper the chemo-rheological behavior of aqueous TiC suspension and physical properties of gelcasted green body were investigated. The monomer system used in this project was acrylamide (AM) and methylenebisacrylamide (MBAM). Polymerisation reaction was promoted by the addition of tetramethyl ethylenediamine as a catalyst and ammonium persulfate as a initiator. The effects of tetramethylammonium hydroxide (TMAH), polyethylenimine (PEI) and polyethylene glycol (PEG) dispersants on the premix solution containing TiC powder have been studied via observation of the zeta potential and rheological behavior. The optimal amount of TMAH was achieved 0.4 wt.% at pH 9. The chemorheological results showed that the gelation time decreased and viscosity increased with increasing the monomer content, solid loading, initiator amount and temperature. The highest flexural strength of gel casted green body was obtained with 50 vol% solid loading and 25 wt.% monomers content.
The aim of this paper is to investigate the effect of thermal stratification together with variable viscosity on free convection flow of non- Newtonian fluids along a nonisothermal semi infinite vertical plate embedded in a saturated porous medium. The governing equations of continuity, momentum and energy are transformed into nonlinear ordinary differential equations using similarity transformations and then solved by using the Runge-Kutta-Gill method along with shooting technique. Governing parameters for the problem under study are the variable viscosity, thermal stratification parameter, non-Newtonian parameter and the power-law index parameter.The velocity and temperature distributions are presented and discussed. The Nusselt number is also derived and discussed numerically.
This article presents measurements of the thickness of alcohol-based coatings on sand foundry cores and moulds. These coatings were applied using two methods, the dipping method and the painting method. For the purposes of the study, a zircon alcohol-based coating was prepared with three different levels of nominal viscosity; very thin at 10s, average at 20s, and thick at 30s. The coating was applied to a core made of quartz sand and furan resin. The cores were made of sand with three different grain sizes; dL = 0.22 mm – fine sand, dL = 0.33 mm medium sand, and dL = 0.47 mm coarse sand. In the study, the thickness of the coating obtained to the core was measured immediately after application as well as after drying. Additionally, the extent of penetration into the intergranular spaces of the core matrix was measured. On the basis of this study, the impact of the grain size of the core matrix on the thickness of the coating and its penetration into the core was assessed. The thickness of coatings obtained using different application methods was also assessed.
The role of slag in the process of continuous casting of steel (CCS) is reduced to the thermal and chemical insulation of the liquid steel surface, and additionally to refining. The ability to adsorb non-metallic inclusions flowing off from the crystallizer, mainly Al2O3, determines its physicochemical properties. As a result of adsorption and dissolution of inclusions tin he liquid layer the viscosity and thickness of mould flux change, which eventually affects the technological parameters and behavior of slag in the crystallizer. The influence of aluminum oxide on the viscosity of slag was empirically investigated with a structural viscosity model worked out by Nakamoto. The results of the simulation are presented in the form of plots. Authors observed a significant influence of Al2O3 on the slag viscosity, which suggests that this effect should be taken into account when selecting chemical composition of mould flux for definite types of steel. The results of calculations also show that the disturbances in casting caused by the use of the mould slag may be connected with the content of non-metallic inclusions in steel.
This article presents results of studies on multicriteria optimisation in the decopperisation process of flash smelting slags coming from the process of decopperisation at the "Głogów II" Copper Smelter. Measurements of viscosity were conducted using a high-temperature viscometer manufactured by Brookfield company. An addition in the form of calcium fluoride has an advantageous influence on decreasing the liquidus temperature of slag, and the effect of decreasing viscosity at the participation of calcium fluoride is significant. A motivation to conduct studies on viscosity of decopperised slags is an optimisation of the process of decopperisation at an improvement of this process parameters, i.e. the time of melt per one production cycle and consumption of electric power in the whole process. The efficiency of optimisation of the process course depends not only on an accepted criterion of the quality of controlling, a type of technological parameters, but also, to large extent, on characteristics and features of these parameters. CaCO3 currently added to the process of decopperisation efficiently decreases viscosity of flash slag, at the same time has influence on an increase of the yield of copper in alloy, but on the other hand, it increases the mass of slag, artificially under representing concentration of this metal. The article is completed with a conclusion of discussed issues, stating that a search for a new technological addition is still necessary,
This study presents the rheological properties of sewage sludge after conditioning with the application of biomass ash. The impact of sewage sludge pre-treatment on its viscosity, ﬂow curves and thixotropy was investigated. The increase of shear stress and the decrease of viscosity were observed with the increase of shear rate. Obtained results were compared with raw sewage sludge and the sludge after modiﬁcation by means of polyelectrolyte in the dosage of 1.5 g (kg d.m.)-1. The ﬁndings proved that samples of raw and conditioned sewage sludge had thixotropic characteristics. The correlation between moisture content and capillary suction time reduction as well as selected rheological parameters were also determined. On the basis of the obtained results it was stated that the Ostwald de Vaele model best ﬁts the experimental data.
Each bitumen has a slightly different group composition, thus bitumen modifi cation with the SBS copolymer gives slightly different results in each case. Both in the industry and construction prac-tice there is still no simple method available which would allow the evaluation of the impact of SBS content and the group composition of bitumen on the structural and rheological properties of the polymer bitumen mix. The article presents the results of the dynamic viscosity tests of three bitumen types. Based on the analysis of the results obtained, it was found that changes in the rheological properties caused by SBS additive are characteristic for each of the bitumens tested and their chemical and group composition. They are also proportionate to the amount of the modifi er added. In order to have a possibility to measure this impact, three coeffi cients rheologically charac-terizing polymer and bitumen mixes were applied.
The study discusses the issues connected with the production of thin-walled ceramic slurry in the replicast cs technology. In the ceramic mould production process, a special role is played by the liquid ceramic slurry used to produce the first layer of the mould. The study examines selected technological properties of liquid ceramic slurries used to produce moulds in the replicas cs technology. The ceramic slurries for the tests were prepared based on the binders Ludox Px30 and Sizol 030, enriched with Refracourse flour. The wettability of the pattern's surface by the liquid ceramic slurry and the dependence of the apparent viscosity on the ceramic flour content in the mixture were determined. The wettability of the pattern surface by the liquid ceramic slurry was determined based on the measurement of the wetting angle. The angle was determined by means of an analysis of the computer image obtained with the use of a CDC camera.
The aim of the present study was to develop a modifier for water glass. The method of thermal generation of metal oxide nanoparticles was adapted and used in the research. Nanoparticles of ZnO from the thermal decomposition of basic zinc carbonate were used. A method for the modifier introduction was developed, and the effect of modifier content and organic solvent type on the physico-chemical properties of binder (viscosity) and quartz wettability was determined. Binder viscosity was examined from the flow curves plotted with the help of a RHEOTEST 2 rotational rheometer equipped with proper software. Quartz wettability was determined examining timerelated changes in the value of the contact angle in a quartz-binder system, until full stabilisation of the angle value has been achieved. Binder modification was carried out on sodium water glass designated as R"145". The water glass modifiers were suspensions of ZnO nanoparticles in propanol and methanol at a fixed concentration of c = 0.3 M and with the size of nanoparticles comprised in a range of <61 - 981 nm>. Water glass modification with the suspensions of ZnO nanoparticles in methanol and propanol showed the effect of modifier on the water glass viscosity and quartz wettability. This effect depends on the type of alcohol used. The ZnO suspension in propanol (alcohol with a longer hydrocarbon chain) affects more strongly the viscosity of binder and quartz wettability than the methanol suspension.
The purpose of the presented experiment was to develop an effective water glass modifier. In the conducted research, an attempt was made to determine the effect of modifier addition on the wettability of quartz grains, viscosity and cohesion of binder and strength Rm U of the sand mixture. Water glass modification was carried out with, obtained in electrochemical process , colloidal suspension of ZnO nanoparticles in methanol (modifier I) or propanol (modifier II), characterised by a constant molar concentration of c = 0.3 M. It was demonstrated that the addition of a colloidal suspension of ZnO nanoparticles in propanol (modifier II) had a significant effect on wettability of quartz grains improvement without the accompanying increase in binder viscosity. Testing the mechanical properties Rm U of sand mixtures containing modified binder (modifier II) hardened at ambient conditions showed an approximately 28% increase in strength compared with the Rm U of the sand bonded with an unmodified binder.