Lower Viscosity Values Research Articles

Visco-resistive MHD study of internal kink (m = 1) modes

We have investigated the effect of sheared equilibrium flows on the m = 1, n = 1 resistive internal kink mode in the framework of a reduced magnetohydrodynamic model in a periodic cylindrical geometry. Our numerical studies show that there is a significant change of the scaling dependence of the mode growth rate in the Lundquist number in the presence of axial flows compared to the no flow case. Poloidal flows do not influence the scaling. We have further found that viscosity strongly modifies the effect of flows on the (1,1) mode both in the linear and nonlinear regimes. Axial flows increase the linear growth rate for low viscosity values, but they decrease the linear growth rate for higher viscosity values. In the case of poloidal flows, the linear growth rate decreases in all cases. Additionally at higher viscosity, we have found strong symmetry breaking in the behaviour of linear growth rates and in the nonlinear saturation levels of the modes as a function of the helicities of the flows. For axial, poloidal, and most helical flow cases, there is flow induced stabilisation of the nonlinear saturation level in the high viscosity regime and destabilisation in the low viscosity regime.

Sedimentation of solids in drilling fluids used in oil well drilling operations

Petroleum stands out as an important energy source. In oil well drilling operations, drilling fluids are used with the main purpose of cleaning and maintaining the hydrostatic pressure in the wellbore. Due to the importance of understanding solid-fluid interaction and the lack of quantitative studies on solids content in regions with high solids concentrations, this study evaluated the stability of drilling fluids. Rheological tests and gravitational and batch sedimentation tests with fluids differentiated by the addition of calcium carbonate assessed the separation dynamics as a function of time and position and determined the constitutive equations for pressure on solids, which are fundamental to solve models of flow through porous media. Gamma-ray attenuation, a non-destructive technique, quantified the local volumetric solids concentration in sedimentary regions. The results showed a shear-thinning behavior and thixotropic effects in the fluids and the influence of calcium carbonate on the sedimentation profile. The non-thickened suspension had lower values of apparent viscosity, higher sedimentation rates, and more compressible sediments than the thickened system. Thus, the formulation of drilling fluids affected the separation process in suspensions; for that reason, it must be adjusted to the operational conditions. This study contributed to increase rheological and stability knowledge on non-Newtonian suspensions.

Conversion of waste shipping oil into diesel-like oil via microwave-assisted pyrolysis

Waste shipping oil, a mixture of used lubricating oil and seawater derived from ship engine operation, was tested for its potential to be converted into a fuel product via an innovative microwave-assisted pyrolysis approach using a reaction bed of activated carbon. Higher carbon to waste ratio was found to have beneficial effects in promoting pyrolysis cracking to produce a higher yield of pyrolysis oil, recording a yield of up to 66wt%. The pyrolysis oil comprised of aliphatic hydrocarbons (C5–C15 hydrocarbons) that are within the hydrocarbon range for gasoline and diesel. Combined with the detection of low viscosity (2 − 5mm2/s) and high calorific value (46MJ/kg) nearly comparable to diesel, the pyrolysis oil shows potential to be upgraded to diesel fuel. The oil product was also detected to have low contents of oxygen (0.1wt%) and sulphur (0.02wt%), showing promising features as a ‘cleaner’ fuel source with potentially reduced formation of tar (an oxygenated byproduct) and low emission of SOx during the use of the oil as fuel in combustion process. Our results indicate that microwave-assisted pyrolysis shows potential as an alternative to transform waste shipping oil into an alternative fuel source.

Physicochemical properties, structural properties, and in vitro digestibility of pea starch treated with high hydrostatic pressure

The influence of high hydrostatic pressure (HHP) treatment at 150, 300, 450, and 600 MPa for 25 min on the physicochemical properties, structural properties, and in vitro digestibility of pea starch was studied. Compared to native and pea starch treated at 150–450 MPa, the morphology of pea starch at 600 MPa was completely destroyed and the particle size became larger, indicating complete gelatinization. The X‐ray diffraction results showed that the native pea starch was gradually changed from the C‐type into the B‐type pattern after 150–600 MPa HHP treatment. At 30–70°C, pea starch treated at 600 MPa had a higher water absorption index (p < 0.05), swelling power, and solubility than other samples did, but opposite results were obtained at 90°C. The rapid visco analyzer (RVA) results indicated that pea starch treated with high pressure at 600 MPa showed lower values of peak viscosity, trough, breakdown, final viscosity, and setback (p < 0.05), reflecting lower retrogradation. Gelatinization temperatures and enthalpy determined by differential scanning calorimetry (DSC) decreased with the increase of pressure. Furthermore, the in vitro digestibility of HHP treated pea starches was lower than that of native pea starch (p < 0.05). Therefore, it is an effective method for HHP treatment to modify the properties of pea starches.

Effect of frying on the pasting and rheological properties of normal maize starch

Normal maize starch (NMS) with various water content was subjected to high temperature in the oil phase to mimic the frying process. The structure and physicochemical properties of the fried starchy samples were investigated. Frying induced the reduction in the swelling power, solubility, the amount of leached amylose, and the molecular weight of starch. Rapid visco-analysis (RVA) revealed the partial gelatinization and limited swelling of starch granules after frying treatment. The effect of frying on the pasting properties of starch was dependent on the water content. Creep curves were fitted with the Burgers model and results showed that the fried samples exhibited higher values of instantaneous creep compliance (J0) and viscoelastic creep compliance (Jm), whereas lower values of zero-shear viscosity (η0) as compared with those of native NMS. The low storage modulus (G′) and low loss modulus (G″) form dynamic viscoelasticity measurements indicated that the fried starch pastes exhibited viscoelastic properties that are inferior to those of native NMS paste. Flow state tests showed that fried starch pastes were less thixotropic than was native NMS. Present work confirmed the inhibitory effect of frying on starch granule swelling and starch molecules leaching. The formation of gelatinization layer near the surface of starch granules and the possible molecular degradation during frying were hypothesized to be responsible for the alterations of the pasting and rheological properties of starch.

Performance Evaluation of a Pressurized Cooking Stove Using Vegetable Cooking Oils as Fuel

Liquid petroleum gas (LPG) and kerosene can be substituted by vegetable cooking oils (VCOs) as fuel using pressurized cooking stove. The higher of ignition values, density and viscosity of VCOs compared to other oils, such as kerosene was a basic consideration to modify the vegetable oil pressure stove (VOPS). The voPs design employed with spiral coil pipe line as oil preheater that was intended to reduce viscosity and ignition values of VCOs. The spiral coil pipe line in this VOPS will auto preaheat the oil to decrease its viscosity and to produce smaller droplets before being combusted. The performance indicators fuel/stove/vessel combination were conducted by measurements, calculations and experiments. The performance parameters were represented by fuel characteristic, oil droplet diameter, combustion flame and fuel consumption. The main purpose of this experiment was to study of the use of VCOs as alternative fuels as well as combustion performance and economics evaluation. The experiment was conducted by using three kind of VCOs as fuel; used vegetable oil (UCO), crude VCO and fresh UCO on VOPS. The VCOs could be burned in a red bluish flame with a maximum flame temperature of flue gases of 1100 °C, 1042 °C and 920 °C, respectively. Atomization of all VCOs could produce fuel droplets diameter of 155 µm-650 µm and lower viscosity and lower ignition values of the fuels. The efficiency of the VOPS was 20%-32% calculated by the fuel consumption rate (FCR) of ±1.50 L/h and gave the economic values were cheaper than using kerosene or LPG as fuel.

Non-axisymmetric structure of the boundary layer of intensive cyclonic vortex

The secondary flows of different types were studied in a boundary layer of cyclonic vortex over localized heater. Near the periphery of the heating area system of horizontal rolls oriented along the basic flow is formed. Thermal plumes which are originated between counter-rotating horizontal rolls are pushed to the centre by basic flow and create spiral bands. Both types of observed secondary flows (rolls and spiral bands) are of convective nature. Cyclonic vortex becomes unstable at low values of viscosity and fast rotation of the experimental model. The instability of the vortex is tightly connected with a structure of the radial inflow. For moderate values of rotational Reynolds number Re the radial flows consist of several branches which transport angular momentum to the centre of the model. When Re exceeds critical value (about 23) radial inflow changes its structure and appears as one wide branch which does not reach the centre. As a result the vortex that slowly moves around the centre is formed instead of the vortex localized in the centre. Further increase of Re leads to chaotic state with several vortices which appears at different locations near the periphery of the heating area. The map of regimes with stable and unstable vortices is presented. The applicability of experimental results to the formation of large-scale atmospheric vortices is discussed.

Viscous flow of medieval cathedral glass

AbstractA popular urban legend concerns the apparent flow of stained glass windows in medieval cathedrals, where the glass windows are commonly observed to be thicker at the bottom than they are at the top. Advances in glass transition theory and experimental characterization techniques now allow for us to address this urban legend directly. In this work, we investigate the dynamics of a typical medieval glass composition used in Westminster Abbey. Depending on the thermal history of the glass, the room temperature viscosity is on the order of 1024 to 1025 Pa·s, about 16 orders of magnitude lower than found in a previous study of soda lime silicate glass. This measurement is in quantitative agreement with a newly derived model for the composition dependence of the nonequilibrium viscosity of glass. Despite this significantly lower value of the room temperature viscosity, the viscosity of the glass is much too high to observe measurable viscous flow on a human time scale. Using analytical expressions to describe the glass flow over a wall, we calculate a maximum flow of ~1 nm over a billion years.

Development of biomedical 5-fluorouracil nanoplatforms for colon cancer chemotherapy: Influence of process and formulation parameters

In the present investigation solvent displacement or nanoprecipitation, and emulsion/solvent evaporation methods were utilized to optimize poly(D,L-lactide-co-glycolide) nanoparticles for the vehiculization of the 5-fluorouracil. Formulation components from both the aqueous and organic phases, as well as, operating conditions were varied. Particles were characterized in terms of particle size and morphology, electrical properties, rheology, drug loading, stability, and drug release. Furthermore, in vitro cytotoxicity on human colon cells and different colon carcinoma cells was evaluated. Four types of nanoparticles were selected for drug loading, revealing differences between variables. Low viscosity values and their Newtonian behavior could assure the suitability of the nanoformulation for the intravenous route of administration. The greatest drug entrapment efficiency and best stability was achieved when the chemotherapeutic agent was incorporated into the internal aqueous phase of particles prepared by double emulsion/solvent evaporation. However, a more sustained drug release at pH 7.4 was possible when 5-fluorouracil was added to the external aqueous phase. These were the nanoformulations reporting the greatest antiproliferative efficacy compared with the free drug. The nanocarrier can optimize the antitumor activity of 5-fluorouracil, thus being a potential nanotool against colon cancer.

Sugarcane bagasse valorization by fractionation using a water-based hydrotropic process

Sugarcane bagasse is abundant agro-industrial waste that can be potentially utilized as a source of valuable compounds and biopolymers. In the present study, sugarcane bagasse from Brazil was fractionated employing an environmentally friendly hydrotropic process. Several treatments were carried out at 150 and 170°C and dwell times of 60 and 120min using unmodified 30% hydrotropic solutions as well as the solutions acidified with formic acid. The major produced fraction was cellulose pulp obtained with the yield of 44–67% (bagasse based) and the cellulose content of 60–92%. Lignins dissolved during the treatments were isolated from the spent solutions by dilution with water and filtration. The yields of the lignins were 11.8–14.7% (bagasse based) and their purity ranged from 88 to 94%. Generally, the purity of both fractions and the yield of lignin were higher at more severe process conditions. However, the more severe conditions resulted in lower average molar masses of the lignins and lower intrinsic viscosity values of the cellulose fractions. The composition of the spent solutions also varied with the treatment conditions, and, besides the lignins, they contained different amounts of dissolved hemicelluloses, sugar monomers, furfural and acetic and formic acids. The results of the present study showed that the hydrotropic process could be successfully applied for the valorization of sugarcane bagasse by its fractionation into lignin, cellulose and other products.

Competition between supernucleation and plasticization in the crystallization and rheological behavior of PCL/CNT-based nanocomposites and nanohybrids

PCL was blended with pristine multiwalled carbon nanotubes (MWCNT) and with a nanohybrid obtained from the same MWCNT but grafted with low molecular weight PCL, employing concentrations of 0.25 to 5 wt % of MWCNT and MWCNT-g-PCL. Excellent CNT dispersion was found in all samples leading to supernucleation of both nanofiller types. Nanohybrids with 1 wt % or less MWCNTs crystallize faster than nanocomposites (due to supernucleation), while the trend eventually reverses at higher nanotubes content (because of plasticization). Rheological results show that yield-like behavior develops in both nanocomposites, even for the minimum content of carbon nanotubes. In addition, the MWCNT-g-PCL family, when compared with the neat polymer, exhibits lower values of viscosity and modulus in oscillatory shear, and higher compliance in creep. These rheological differences are discussed in terms of the plasticization effect caused by the existence of low molecular weight free and grafted PCL chains in the nanohybrids. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1310–1325

Instability of cyclonic convective vortex

Localized heating in the rotating layer of fluid leads to the formation of intensive cyclonic vortex. Cyclonic vortex becomes unstable at low values of viscosity and fast rotation of the experimental model. The instability of the vortex is tightly connected with a structure of the radial inflow. For moderate values of rotational Reynolds number Re the radial flows consist of several branches which transport angular momentum to the center of the model. When Re exceeds critical value (about 23) radial inflow changes its structure and appears as one wide branch which does not reach the center. As a result of strong anisotropy of radial inflow the cyclonic vortex is formed at some distance from the center. Further increase of Re leads to chaotic state with several vortices which appears at different locations near the periphery of the heating area. The map of regimes with stable and unstable vortices is presented.

Rheological and thermal properties of exfoliated graphite nanoplatelets‐filled impact modified polypropylene nanocomposites

The objective of this research was to investigate the influence of exfoliated graphite nanoplatelets (xGnP) particle diameter, filler loading, and the addition of coupling agents on the rheological and thermal properties of xGnP‐filled impact modified polypropylene (IMPP) nanocomposites. xGnP‐filled IMPP composites were manufactured via melt mixing with and without the addition of polypropylene‐graft‐maleic anhydride (PP‐g‐MA). Particle diameter of xGnP had no significant effect on the melting (Tm) and crystallization (Tc) temperatures as well as degradation behavior of the composites. Storage modulus (E′) of the composites increased with increasing xGnP percent at high filler loadings and the incorporation of xGnP did not significantly affect the glass transition temperature, but filler loading does have a significant effect on the magnitude of the tan delta max peak values. The shear storage modulus (G′) of the composites with smaller diameter xGnP particles was lower than those of the composites with big diameter particle xGnP at lower frequencies. The higher the xGnP content of the composite, the higher the shear viscosity and the smaller particle diameter of xGnP results in lower viscosity values. Addition of a coupling agent decreased the melt viscosity of the xGnP‐filled nanocomposites and caused a slight reduction in the shear‐thinning behavior. POLYM. COMPOS., 39:E1512–E1519, 2018. © 2017 Society of Plastics Engineers

Monoethanolamine-based deep eutectic solvents, their synthesis and characterization

Since reporting the Reline (choline chloride and urea at 1:2 M ratio) deep eutectic solvent (DES) few years ago, a diversity of similar solvents have been prepared, characterized and used in different practical applications. The need is still available for converting some conventional solvents into a eutectic formulation for different reasons. In this work, the monoethanolamine (MEA) is combined with three different quaternary salts to form DES at different molar compositions. The resulting DESs were characterized by measuring their main physical properties including melting point, density, viscosity, surface tension, and refractive index within the temperature range of 298.15–358.15 K. An FTIR analysis was also conducted to provide an evidence of any chemical structural changes. These new eutectic fluids have melting points below 279.15 K and of relatively low density and viscosity values. The molar composition of these DESs have significant effect on their physical properties. These new fluids can be utilized for a variety of applications involving adsorptive gas separation and particularly carbon dioxide capture.

Rheological properties of rice flour treated with mild solutions of citric acid.

Effects of milling methods and organic acids treatments on rheological properties of rice flour were investigated. The average particle-size of wet-milled rice flour was lower and showed lower pasting temperature, peak viscosity, and storage modulus values than those of dry-milled rice flour. Wet-milled rice flour treated with citric acid showed significantly low viscosity and viscoelastic properties, as the concentration of citric acid increased, whereas wet-milled rice flour treated with acetic acid was not significantly affected by the acetic acid concentration. Rheological property of baekseolgi (Korean rice cake) made with wet-milled citric-acid-treated rice flour showed a similar trend in viscoelasticity, wherein citric acid treatment lowered the hardness of the rice. However, cohesiveness increased with increasing citric acid concentration. Overall, milling method affected the particle size, which influenced the viscosity and heat stability, whereas citric acid treatment affected the rheological properties of rice flour. These results are expected to contribute to the development of an appropriate method for rice flour application.

Production and Characterization of Green gasoline Obtained by Thermal Catalytic Cracking of Crude Palm Oil (Elaeis guineensis, Jacq.) in a Pilot Plant

This study investigated the production and characterization of green gasoline obtained from crude palm oil (Elaeis guineensis, Jacq.), which was submitted at a process of thermal catalytic cracking in a pilot plant. The cracking reactions were carried out in a reactor of 143 L, operating in batch mode at 450ºC and atmospheric pressure, using 20% (w/w) sodium carbonate (Na2CO3) as catalyst. The organic product liquid (OLP) obtained in the cracking was submitted the distillation in laboratory scale using a column vigreux type. The results show that the yields in OLP obtained in the presence of Na2CO3 were of 65.86%, with acid value of 1.02 mg KOH/g and an elevated formation of gas residual. In relating to the green gasoline this presented a low kinematic viscosity value of 0,72 (mm2.s-1) and acid value of 1,11 mg KOH/g. GC–MS analysis indicated in chemical composition of the green gasoline a percentage of 52,78% of hydrocarbon, of these 15,78% are paraffinic compounds, 31,54% of olefin, 3,50% of naphthenic and 1,94% of aromatic compounds

Comparative Study between Physical Properties of Virgin Oil and Re-Refining Oil

The lubricating oils are essential for operating engine with high efficiency. Therefore, the physical properties of oil such as flash point, pour point, kinematic viscosity, specific gravity and the American Petroleum Institute are necessary to be studied to indicate good quality of the lubricating oil. In this study, we compare the physical properties of two virgin oils with re-refining oil. The results indicated slight differences in the re-refining oil properties in comparing to virgin oils due to larger values of specific gravity and carbon residue, and lower value of flash point, pour point, kinematic viscosity, and American Petroleum Institute.

Pyrolytic Conversion of Olive Mill Wastewater Sludge to Biofuels Using Red Mud as Catalyst

Olive mill wastewater sludge (OMWS) is an environmental pollutant in olive oil industry. The problem stems from the strong odor and poor biodegradability of OMWS because of its high phenolic compounds. In most Mediterranean countries, olive mill wastewater is stored in evaporation ponds and the residual sludge is landfilled for disposal. To address this environmental pollution problem, fluidized bed catalytic pyrolysis of OMWS was developed to produce pyrolysis liquids that are stable, low viscosity (5-7 cP), neutral pH (6-7), and high higher heating value (41 MJ/kg). The pyrolysis was conducted at 400-500°C in a red mud catalyst bed. The yields of the organic fraction were 29-35 mass%; char/coke yield was 20-29 mass%; and gas yield was 24-37 mass%. The 13C NMR and GC/MS analyses of the liquid products showed predominance of aliphatic hydrocarbons and small fractions of aromatic hydrocarbons and ketones. The composition of these liquid products is in sharp contrast with most lignocellulosic biomass pyrolysis products which are normally rich in aromatic compounds and have very low aliphatic product content. In the absence of the red mud catalyst, the liquid product was viscous and contained acidic compounds.

Hyaluronic acid decreases the mechanical stability, but increases the lytic resistance of fibrin matrices

Hyaluronic acid (HA) is a large, non-sulfated glucosaminoglycan abundantly present at sites where fibrin is also formed (during wound healing, in arterial restenotic lesions and eroded atherosclerotic plaques). The aim of the present study was to characterize the structure of composite fibrin-HA clots with scanning electron microscopy (SEM), pressure-driven permeation and small-angle X-ray scattering (SAXS) and their viscoelastic properties with an oscillation rheometer. In addition the efficiency of fibrinolysis in these clots was investigated by kinetic turbidimetric and chromogenic assays for dissolution of fibrin and plasminogen activation by tissue-type plasminogen activator (tPA). Fibrin formed in the presence of native (1500kDa) HA and its 500kDa fragments had thicker fibers and larger pores according to the SEM and clot permeation data, whereas the 25kDa HA fragments had only minor effects. SAXS evidenced a mild disarrangement of protofibrils. These structural alterations suggest that HA modifies the pattern of fibrin polymerization favouring lateral association of protofibrils over formation of branching points. Rheometer data showed softer fibrin structures formed with 1500kDa and 500kDa HA and these clots presented with lower dynamic viscosity values and lower critical stress values at gel/fluid transition. tPA-catalysed plasminogen activation was markedly inhibited by HA, both in free solution and on the surface of fibrin clots, in the presence and in the absence of 6-aminohexanoate suggesting a kringle-independent mechanism. HA of 1500 and 500kDa size prolonged clot lysis with both plasmin and tPA and this inhibition was kringle-mediated, because it was abolished by 6-aminohexanoate and was not observed with des-(kringle1–4)-plasmin. Our data suggest that HA size-dependently modifies the pattern of fibrin polymerization with consequent inhibition of fibrinolysis. At sites of tissue injury and inflammation, HA could stabilize fibrin through modification of its structure and lysibility.

Evaluation of the fuel quality values of bay laurel (Laurus nobilis L.) oil as a biodiesel feedstock

ABSTRACTDoubts about energy resources are forcing scientists to seek new energy sources. Environmental concerns force scientists to evaluate less damaging alternative fuels such as biodiesel. The aim of this study is to evaluate the availability of bay laurel oil (BLO) in diesel engines as alternative fuel. In this work, the fuel quality of pure bay laurel oil is tested. The measured fuel quality values were density, cetane number, viscosity, pour point and flash point. According to the results, BLO has a low cetane number, high density and viscosity values, and also a high free fatty acid (FFA) value.