scholarly journals Dynamic Viscosity and Activation Energy of Wort During Fermentation and Storing

2016 ◽  
Vol 19 (1) ◽  
pp. 6-9
Author(s):  
Peter Hlaváč ◽  
Monika Božiková ◽  
Vladimír Cviklovič
Keyword(s):  
Activation Energy ◽  
Temperature Dependence ◽  
Exponential Function ◽  
Dynamic Viscosity ◽  
Structural Changes ◽  
Effect Of Temperature ◽  
Rotational Viscometer ◽  
Viscosity Measurements ◽  
Sample Resistance

This paper presents the results of wort dynamic viscosity and activation energy during fermentation. The effect of temperature and storing time on both parameters was investigated. Measurements were performed on two wort samples. The first sample was taken at the beginning of fermentation, and the second sample after three hours of fermentation. Both samples were also measured after three weeks of storing. Dynamic viscosity measurements were performed with a digital rotational viscometer Anton Paar DV-3P, the principle of which is based on the dependency of sample resistance to probe rotation. Results of measurements are shown as graphical dependencies of both analysed parameters on temperature. The temperature dependence of dynamic viscosity can be characterised by a decreasing exponential function, while in case of activation energy linear increasing characters were obtained. Longer fermentation and storing period caused a decrease in both analysed parameters, due to the structural changes in wort samples during fermentation and storing.

scholarly journals Temperature Relations of Selected Engine Oils Dynamic Viscosity

2014 ◽  
Vol 17 (4) ◽  
pp. 105-108
Author(s):  
Peter Hlaváč ◽  
Monika Božiková ◽  
Radmila Presová
Keyword(s):  
Dynamic Viscosity ◽  
Effect Of Temperature ◽  
Motor Oil ◽  
Exponential Functions ◽  
Rotational Viscometer ◽  
Engine Oils ◽  
The Third ◽  
Used Oil ◽  
Different Types ◽  
Sample Resistance

Abstract This article focuses on temperature relations of dynamic viscosity for selected engine oils. The effect of temperature on new and used oil dynamic viscosity was investigated. Measurements were performed on three different motor oil samples. All the three motor oil samples were synthetic. The first oil sample was new, the second sample was used for 15,000 km, and the third sample was used for 30,000 km. There were made two measurements of samples in one week. Dynamic viscosity was measured using a digital rotational viscometer Anton Paar DV-3P. The principle of measurement is based on the dependence of sample resistance to probe rotation. The results of measurements are shown as graphical relationships between dynamic viscosity and temperature. Decreasing exponential functions in temperature relationships were used for all the samples. The highest difference between the first and second measurement was observed in the new oil, and very small differences were found in other oils. Due to different types of oils and different stage of usage, the results could not be compared.

scholarly journals Effect of Temperature and Used Ingredients on Rheological Parameters of Pancake Dough

2013 ◽  
Vol 16 (3) ◽  
pp. 63-66
Author(s):  
Peter Hlaváč ◽  
Monika Božiková
Keyword(s):  
Rheological Properties ◽  
Dynamic Viscosity ◽  
Kinematic Viscosity ◽  
Fat Content ◽  
Effect Of Temperature ◽  
Rheological Parameters ◽  
Rotational Viscometer ◽  
Two Samples ◽  
Dynamic And Kinematic Viscosity ◽  
Temperature Dynamic

Abstract This paper presents the selected rheological properties of pancake dough such as dynamic and kinematic viscosity and fluidity. The effect of used ingredients and temperature on rheological properties is investigated. Measurements were performed on three pancake dough samples. In two samples, there was used milk with a different fat content, and in the third sample, all ingredients were in a powder state. A digital rotational viscometer Anton Paar DV-3P was used for measuring the rheological properties. The principle of viscometer measurement is based on the dependence of sample resistance to probe rotation. Results of measurements are shown as graphical dependencies of rheological parameters on temperature. Exponential functions were used to express the dependencies of all rheological parameters on temperature. Dynamic and kinematic viscosity decreased, and fluidity increased with temperature. The highest values of dynamic viscosity were obtained for pancake dough from powder ingredients. A higher fat content of used milk caused higher values of dynamic viscosity.

scholarly journals Temperature Dependence of Viscosity and Density of cis-1,4/trans-1,3-Dimethylcyclohexane and Several other Commonly Used Organic Solvents

2003 ◽  
Vol 217 (6) ◽  
pp. 707-722 ◽  
Author(s):  
A. A. Ruth ◽  
H. Lesche ◽  
B. Nickel
Keyword(s):  
Low Temperature ◽  
Temperature Dependence ◽  
Organic Solvents ◽  
Temperature Regime ◽  
Dynamic Viscosity ◽  
Temperature Range ◽  
Viscosity Measurements ◽  
Glass Forming ◽  
Temperature Ranges

AbstractThe dynamic viscosity (η) of the glass-forming 50:50 mixture of cis-1,4/trans-1,3-dimethylcyclohexane (ct-DMCH) was measured from 293 K down to ≈ 126 K where η ~ 1.2 × 106 mPas. The viscosity measurements of several other commonly used solvents cover the range from 293 K down to ≈ 148 K (η ~ 1.4 × 104 mPas) for 1-propanol (1-Prop), to ≈118 K (η ~ 2.5 × 102 mPas) for 2-methylpentane (2-MP), to ≈ 167 K (η ~ 10.0 mPas) for isooctane (Isooct), to ≈ 183 K (η ~ 2.8 mPas) for cyclopentane (CP) and down to ≈ 98 K (η ~ 4.6 × 102 mPas) for the 30:70 mixture of cyclopentane/isopentane (CP/IP). The density (ρ) of all solvents was measured correspondingly over appropriate temperature ranges. For the solvents studied here, the temperature dependence of the viscosity can be represented by a single Arrhenius term down to ~180 K. Over a wider temperature range down to ~118K the sum of two Arrhenius terms is required, and in the low temperature regime a Vogel–Tammann–Fulcher expression is necessary to adequately describe the temperature dependence of the dynamic viscosity.

Effect of Temperature on Dynamic Viscosity and Activation Energy of Milk and Acidophilus Milk

2014 ◽  
Vol 1059 ◽  
pp. 53-59
Author(s):  
Peter Hlaváč ◽  
Monika Božiková
Keyword(s):  
Activation Energy ◽  
Dynamic Viscosity ◽  
Arrhenius Equation ◽  
Viscosity Measurement ◽  
Effect Of Temperature ◽  
Rheological Parameters ◽  
Physical Parameters ◽  
Measured Temperature ◽  
Regression Equations ◽  
Increasing Functions

This article is focused on temperature dependencies of rheological parameters as the dynamic viscosity and activation energy of milk and acidophilus milk. Viscosity measurement was performed using a single-spindle viscometer. The relations of dynamic viscosity and activation energy in the temperature range 5–25 oC for milk and acidophilus milk were measured. The relations of all physical parameters of milk to temperature showed the influence of relative fat content. The effect of temperature on milk and acidophilus milk parameters is shown in Fig. 1–4. In the measured temperature interval, dynamic viscosities of milk ranged between 2.0 mPa.s and 1.3 mPa.s, and of acidophilus milk between 443.4 mPa.s and 244.1 mPa.s. Measured relations of dynamic viscosity for milk and acidophilus milk during temperature stabilisation had an exponential decreasing progress (Fig. 1–2), which is in accordance with Arrhenius equation. Temperature dependencies of activation energy are described by linear increasing functions (Fig. 3–4). Obtained values of activation energy were in the range 356.97–1267.70 J/mol for milk and in the range 615.94–2129.96 J/mol for acidophilus milk. The mathematical description of the dependencies is summarised by regression equations 2 and 3. Coefficients of regression equations and coefficients of determination approximately in the range 0.984–0.999 are presented in Table 1.

Effect of Molecular Weight, Shape of the Molecule, and Presence of Polar Groups on the Autohesion of High Polymers. III

1957 ◽  
Vol 30 (2) ◽  
pp. 548-554 ◽  
Author(s):  
S. S. Voyutskiĭ ◽  
B. V. Shtarkh
Keyword(s):  
Activation Energy ◽  
Molecular Weight ◽  
Temperature Dependence ◽  
Structural Changes ◽  
Chain Molecule ◽  
Complete Disappearance ◽  
Short Side ◽  
Polar Groups ◽  
Kinetics Of ◽  
High Polymers

Abstract 1. It is shown for polyisobutylenes of different molecular weight that increase in the size of the chain molecule retards autohesion, but increases the limiting value to which the work of autohesion tends with increasing contact time. 2. Investigation of the temperature dependence of autohesion of polyisobutylenes showed that the activation energy does not depend on the molecular weight of the polyisobutylene. 3. It is shown for polybutadienes with varying contents of 1,4- and 1,2-structures that autohesion decreases with increase in the number of short side groups in the molecule, which apparently hinder diffusion by purely steric causes. 4. Investigation of the temperature dependence of autohesion of butadienenitrile copolymers with different contents of acrylonitrile in the molecule showed that the activation energy of autohesion increases with increase of polar nitrile groups in the polymer. 5. It is shown for the vulcanization of natural rubber that the formation of a spatial structure results in complete disappearance of autohesion in high polymers. It is shown that the kinetics of changes of autohesion during vulcanization can effectively characterize the structural changes which take place in the polymer during the process.

scholarly journals Temperature Dependence of Limiting Fluorescence Anisotropy of POPOP in Cellulose Acetate Film

1985 ◽  
Vol 40 (6) ◽  
pp. 559-561
Author(s):  
A. Kawski ◽  
A. Kubicki ◽  
I. Weyna ◽  
I. Janić
Keyword(s):  
Temperature Dependence ◽  
Cellulose Acetate ◽  
Fluorescence Anisotropy ◽  
Thermal Relaxation ◽  
Effect Of Temperature ◽  
Torsional Vibrations ◽  
Slow Increase ◽  
Cellulose Acetate Film ◽  
Luminescent Centre

The effect of temperature (103 K < T < 303 K) upon the limiting fluorescence anisotropy r0 of POPOP was investigated in a cellulose acetate film. A slow increase in r0 was observed when reducing the temperature. Based on the Jabłoński theory, the frequency of the torsional vibrations of POPOP was determined to be w = 1.3 x 1012s−1. The depolarization due to these torsional vibrations was found to occur immediately following excitation during the thermal relaxation of the luminescent centre, thus somewhat lowering the value of the fundamental fluorescence anisotropy rf to the limiting r0 value.

ENTROPY INFLUENCE ON THE DEPENDENCE OF THE NANOFLUIDS VISCOSITY ON TEMPERATURE AND SHEAR RATE

2021 ◽  
Vol 7 (3) ◽  
pp. 89-105
Author(s):  
Lyudmila P. SEMIKHINA ◽  
Daniil D. Korovin
Keyword(s):  
Activation Energy ◽  
Shear Stress ◽  
Shear Rate ◽  
Viscous Flow ◽  
High Reliability ◽  
Narrow Particle Size Distribution ◽  
Disperse Systems ◽  
Rotational Viscometer ◽  
Surfactant Micelles ◽  
Dispersed Systems

A Brookfield DV-II + Pro rotational viscometer was used to study the viscosity of 7 samples of concentrated nanodispersed systems (nanofluids) with a similar viscosity (6-22 mPa ∙ s), the particles of the dispersed phase in which are nanosized surfactant micelles and conglomerates from them. It was found that for 5 out of 7 studied reagents, there is a decrease in viscosity typical for dispersed systems with an increase in the shear rate, and their flow curves, that is, the dependence of the shear stress on the shear rate, correspond to the ideal plastic flow of non-Newtonian fluids. Moreover, with high reliability, R2 ≥ 0.999 is described by the Bingham equation with a small value of the limiting shear stress (less than 0.2 Pa). It is shown that all the studied reagents are also characterized by an increase in the activation energy of a viscous flow Е with an increase in the shear rate. As a result, a decrease in viscosity with an increase in shear rate, typical for disperse systems, including nanofluids, is provided by a more significant increase in entropy changes ΔS compared to Е. It has been substantiated that, depending on the ratio between the activation energy of viscous flow Е and the change in entropy ΔS, the viscosity of concentrated micellar dispersed systems with an increase in the shear rate can decrease, remain unchanged, and increase. The last two cases, not typical for disperse systems and nanofluids, were identified and studied using the example of two demulsifiers, RIK-1 and RIK-2, with a maximum of a very narrow particle size distribution at 160 ± 5 nm, corresponding to the size of a special type of very stable micelles Surfactant — vesicle.

scholarly journals Photocatalytic Degradation of Textile Dyeing Wastewater Using Titanium Dioxide and Zinc Oxide

2008 ◽  
Vol 5 (2) ◽  
pp. 219-223 ◽  
Author(s):  
Abbas J. Attia ◽  
Salih H. Kadhim ◽  
Falah H. Hussein
Keyword(s):  
Activation Energy ◽  
Zinc Oxide ◽  
Titanium Dioxide ◽  
Photocatalytic Degradation ◽  
Irradiation Time ◽  
Effect Of Temperature ◽  
Dyeing Wastewater ◽  
Textile Dyeing ◽  
Textile Factory ◽  
Textile Dyeing Wastewater

Photodegradation of a real textile dyeing wastewater taken from Hilla textile factory in Babylon Governorate, Iraq have been investigated. Photocatalytic degradation was carried out over suspensions of titanium dioxide or zinc oxide under ultraviolet irradiation. Photodegradation percentage was followed spectrophometrically by the measurements of absorbance at λmax equal to 380 nm. The rate of photodegradation increased linearly with time of irradiation when titanium dioxide or zinc oxide was used. A maximum color removal of 96% was achieved after irradiation time of 2.5 hours when titanium dioxide used at 303K and 82% color reduction was observed when zinc oxide used for the same period and at the same temperature. The effect of temperature on the efficiency of photodegradation of dyestuff was also studied. The activation energy of photodegradation was calculated and found to be equal to 21 ± 1 kJ mol-1 on titanium dioxide and 24 ± 1 kJ mol-1 on zinc oxide.

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