scholarly journals Rheological Behavior of Mango Juice throughout the Production Process

2019 ◽  
Vol 9 (1) ◽  
pp. 4235-4239
Keyword(s):  
Activation Energy ◽  
Rheological Properties ◽  
Flow Behavior ◽  
Flow Index ◽  
Pumping Power ◽  
Power Requirement ◽  
Thixotropic Behavior ◽  
Calculated Activation Energy ◽  
Mango Juice ◽  
Calculated Activation

The need for studying the flow behavior of the treated juice in the three main parts of the process (After mixing, after Pasteurization and after cooling) is essential in predicting the pumping power requirement. In the present paper, the rheological properties of mango juice are determined at the end of three steps in the production line: First, after the mixing step, second after homogenization and finally after cooling. The following properties determined, Brix concentration, Acidity of solution, and the rheological properties. Mixed juice showed Bingham behavior with values of yield stress decreasing with increased temperature. The activation energy was determined to equal about 24 kJ.mol-1 . Samples collected after the homogenization step exhibited shear thinning behavior with an almost constant flow index of 0.525. The activation energy was determined as 10.93 kJ.mol-1 . The juice samples collected from that step exhibited a mild thixotropic behavior. The results of the third step involving cooling of the homogenized juice revealed that the liquid reverted to Bingham behavior with values of consistency index decreasing with increased temperatures. The calculated activation energy equals 11.22 kJ.mol-1 .

Effect of glycerol concentration and temperature on the rheological properties of cassava starch solutions

2013 ◽  
Vol 33 (2) ◽  
pp. 141-148 ◽  
Author(s):  
Germán Ayala Valencia ◽  
Ana Cecilia Agudelo Henao ◽  
Rubén Antonio Vargas Zapata
Keyword(s):  
Activation Energy ◽  
Rheological Properties ◽  
Apparent Viscosity ◽  
Weight Ratio ◽  
Exponential Model ◽  
Cassava Starch ◽  
Flow Index ◽  
Glycerol Concentration ◽  
Glycerol Content ◽  
All Solutions

Abstract Glycerol/starch (G/S) solutions were prepared at different concentrations, with a weight ratio of G/S=0.0, 0.1, 0.2, 0.3, 0.4 and 0.5, and rheological properties were analyzed at 30, 40, 50, 60 and 70°C. Power law dependency of the apparent viscosity as a function of the shear rate is the most appropriate model for describing the rheological behavior of cassava starch solutions as a function of glycerol concentrations. All solutions showed a pseudoplastic behavior; the flow index (n) did not show significant changes as a function of temperature and glycerol concentration. However, the apparent viscosity (μa) and the consistency coefficient (K) did show strong variations with temperature and glycerol content. The temperature variation of both μa and K were better fitted to an exponential model type exp(Ea /RT), logμa(K) vs. 1000/T. The activation energy of the K data for the solution without glycerol (G/S=0.0) was 13.64 KJ/mol, and it decreased with increasing the content of glycerol in the solutions, becoming 6.14 KJ/mol for G/S=0.5. On the contrary, the activation energy for the μa data increased when increasing the glycerol concentration. The effect of glycerol concentration was also modeled using polynomial and exponential fittings.

Annealing Behavior of the Compressed AZ31 Magnesium Alloy with Different Strain

2007 ◽  
Vol 546-549 ◽  
pp. 267-270
Author(s):  
Tian Mo Liu ◽  
Pan Xiao ◽  
Fu Sheng Pan ◽  
Qing Liu
Keyword(s):  
Activation Energy ◽  
Annealing Temperature ◽  
Hardness Test ◽  
Test Results ◽  
Annealing Behavior ◽  
Different Temperatures ◽  
Calculated Activation Energy ◽  
Calculated Activation ◽  
Crystallographic Orientations ◽  
Microhardness Tester

The cold-compressed AZ31 magnesium alloys with different (2.5%, 5%, 7.5%, 10%, 12.5% and 15%) were annealed at different temperatures (573, 623 and 673K) for different time. With aid of the optical microscopy, and microhardness tester, the microstructural evolution during annealing at different temperature of the compressed AZ31 has been investigated. The microstructural characterized results were further related to the hardness test results and the calculated activation energy. The results showed that for the compressed AZ31, the recrystallization can occur on the samples with the strain just above 10% and the deformation twinning plays an important role on the nucleation and grain growth of the recrystallization. It was found that the twinning boundary was the location of the recrystallization nuclei and a lot of recrystallized grains with equiaxed shape were found along the twinning boundaries. The relationships among the nuclei orientations and the crystallographic orientations on both sides of the twining boundary have been statistically investigated. The effects of the compressed strain and the annealing temperature on annealing behavior were also discussed based on the experimental results.

scholarly journals DTA Evaluation of Spruce Wood Degradation Process

2017 ◽  
Vol 25 (40) ◽  
pp. 41-48
Author(s):  
Ivan Hrušovský ◽  
Peter Rantuch ◽  
Jozef Martinka ◽  
Simona Dzíbelová
Keyword(s):  
Activation Energy ◽  
Room Temperature ◽  
Degradation Process ◽  
Heating Rates ◽  
Wood Degradation ◽  
Wood Sawdust ◽  
Spruce Wood ◽  
Calculated Activation Energy ◽  
Two Stages ◽  
Calculated Activation

Abstract The decomposition stages of spruce wood sawdust were analyzed by means of sequential differential calorimetry. Two stages of decomposition were identified and activation energy of one stage was calculated using the Kissinger method. The DTA was conducted by means of SEDEX safety calorimeter. Sample was analyzed under three heating rates of 10, 20 and 45 °C/h in temperature range from room temperature to 400 °C. The calculated activation energy for the last and most clear decomposition peak was 122.63 KJ/mol. The results are comparable with the data calculated by J.V. Rissanen et al., who calculated activation energy for Spruce hemicellulose as 120 KJ/mol.

A method of preparation of x-casein and some observations on its nature

1962 ◽  
Vol 29 (2) ◽  
pp. 163-171 ◽  
Author(s):  
G. C. Cheeseman
Keyword(s):  
Activation Energy ◽  
Calcium Ions ◽  
Ion Concentration ◽  
Gel Formation ◽  
Protein Nitrogen ◽  
First Order ◽  
Electrophoretic Patterns ◽  
Calculated Activation Energy ◽  
Milk Coagulation ◽  
Calculated Activation

SummaryDetails are given of the method used in this laboratory for the preparation of k-casein. The recovery is about 25% and the material has a purity, estimated from electrophoretic patterns, of about 90% with β-casein as the main contaminant. Higher temperatures and lower ion concentration caused precipitation of k-casein in the presence of calcium ions, 0·1m-acetate buffer at pH 6·5 being sufficient to stabilize a 0·5% solution in the presence of 0·01–0·2m-CaCl2 at 20 and 30°C but not at all calcium concentrations at 40°C. It was also found that solutions of para-k-casein did not aggregate in the presence of concentrations of electrolytes above about 0·25m.The rate of release of non-protein nitrogen and decline in viscosity during the enzymic stage of gel formation in solutions of k-casein and rennin had similar apparent first order constants (0·087 ± 0·03 min—1 and 0·086 ± 0·021 min—1, respectively, at 25°C). A gel could be formed by rennin action in a solution containing as little as 6·25mg of the protein per litre. In the non-enzymic stage of gelling of k-casein solutions the calculated activation energy over the range of 20–40°C was much lower than that obtained from the non-enzymic stage of milk coagulation.

scholarly journals Rheological properties of loose sands subjected to upward flow

2017 ◽  
Vol 54 (5) ◽  
pp. 664-673 ◽  
Author(s):  
Hyo Sub Kang ◽  
Yun Tae Kim
Keyword(s):  
Shear Rate ◽  
Debris Flow ◽  
Rheological Properties ◽  
Yield Stress ◽  
Flow Behavior ◽  
Fluid Pressure ◽  
Hydraulic Gradient ◽  
Flow Index ◽  
Loose Sand ◽  
Upward Flow

The objective of this study was to investigate the rheological properties of loose sands subjected to upward flow by using a vane-type rheometer that controlled upward flow in the loose sand specimens. Various hydraulic gradients (i.e., i = 0–2.0) were applied to loose sands. The rheological properties of the loose sands, such as yield stress and viscosity, were determined based on the Bingham and Herschel–Bulkley models. The experimental results showed that the flow behavior of loose sand samples exhibited a shear thickening when the Herschel–Bulkley model was applied (i.e., nondimensional flow index n > 1) and exhibited a Bingham-like within a limited shear rate range (i.e., 1∼30 1/s). The latter is clearly shown for a relatively high shear rate. As the hydraulic gradient was increased, the flow characteristics were close to the Bingham fluid. Yield stress showed a tendency to decrease linearly as hydraulic gradient was increased. However, the viscosity of the loose sands maintained a constant value irrespective of hydraulic gradient. The test results indicated that the pore fluid pressure resulting from upward flow in a soil sample affects yield stress, which contributes to the initiation of debris flow mobilization. As a result, it was possible to estimate the rheological properties of soil at the condition of liquefaction (critical hydraulic gradient), or initial occurrence of debris flow.

Calculations of activation energy and frequency factors for corn leafs pyrolysis using excel solver: new concept

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Omar Salim Al-Ayed ◽  
Mohammad Waleed Amer ◽  
Sura Al-Harahshah ◽  
Birgit Maaten ◽  
Muhammad Sajjad Ahmed
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Frequency Factor ◽  
Heating Rates ◽  
First Order ◽  
First Order Kinetics ◽  
Calculated Activation Energy ◽  
Apparent Activation Energies ◽  
Excel Solver ◽  
Calculated Activation

Abstract Thermal degradations of biomass corn leaves were studied for kinetic modeling. Thermogravimetric-differential analyzer runs at 5, 10, 20, and 30 °C min−1 heating rates were employed. Apparent activation energy and frequency factor values were calculated for first-order kinetics using several procedures. The procedure of Coats and Redfern showed 28.89 to 31.78 kJ mol−1 apparent activation energy and 15.5 to 157.12 min−1 frequency factor, respectively. Calculation of the apparent activation energy and frequency factor using Kissinger–Akahira–Sunose procedure gave 229.9–364.2 kJ/mol and 8.567 × 1023 and 1.13 × 1031 (min−1), respectively as the conversion increased from 0.1 to 0.9. The newly introduced excel solver procedure indicates a distribution activation energy over the entire range of conversion. For first-order reaction kinetics, the calculated apparent activation energy magnitudes ranged between 5.0 kJ mol−1 with frequency factor equals to 0.239 and 196.2 kJ mol−1 with frequency factor 2.89 × 1012 in the studied range. The low or high magnitudes of the calculated activation energy are not associated with a particular value of the conversion. The calculated apparent activation energies are related to the direct solution of the simultaneous equations that constitute the basis of the excel solver.

Derivation of interionic potentials using embedded quantum-mechanical clusters: Cation and anion impurities in MgO

1990 ◽  
Vol 5 (3) ◽  
pp. 623-628 ◽  
Author(s):  
Ravindra Pandey ◽  
Jun Zuo ◽  
A. Barry Kunz
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Quantum Mechanical ◽  
Impurity Potential ◽  
Data Comparison ◽  
Defect Energies ◽  
Calculated Activation Energy ◽  
Calculated Activation

The ICECAP methodology is used to derive interionic potentials of some cation and anion impurities in MgO, namely, Li+, Na+, K+, Be2+, H−, S2−, and O2−. Analysis is given of the defect energies obtained by using the derived impurity potentials. Based on the available experimental data, comparison is made to justify the reliability of the derived impurity potential for Be2+. The calculated activation energy for Be2+ diffusion comes out to be 1.54 eV as compared to the experimental value of 1.60 eV, which is considered to be very satisfactory.

Electronic-Ionic Conductivity of Lithium- Vanado- Phosphate Glasses

2017 ◽  
Vol 14 (1) ◽  
pp. 9-14
Author(s):  
Eraiah B
Keyword(s):  
Activation Energy ◽  
Ionic Conductivity ◽  
Structural Changes ◽  
Glass Network ◽  
Phosphate Glasses ◽  
Melt Quenching ◽  
Calculated Activation Energy ◽  
Quenching Method ◽  
Increasing Temperature ◽  
Calculated Activation

The new glassesof glass system x Li 2 O-50 V 2 O 5 -(50-x) P 2 O 5 were prepared by using conventional melt quenching method. The densities of these glasses have been measured by Archimedes method and corresponding molar volumes have also been calculated. The conductivity of these glasses was measured as a function of temperature and composition. The variations of conductivity versus temperature follow Arrehenius type relationship. Conductivity decreases with increasing Li 2 O content and increase with increasing temperature. The calculated activation energy decreases up to 15mol% of Li 2 O, it increases from 15mol% to 30 mol% of Li 2 O and again it suddenly drops at 40 mol% of Li 2 O. This may be due to structural changes in glass network and these glasses exhibit both electronic and ionic conductivity.

Kinetics Study on Burning Performance of Polyurethane Foam

2012 ◽  
Vol 174-177 ◽  
pp. 429-432 ◽  
Author(s):  
Yan Min Zheng ◽  
Jun Hui Zhang ◽  
Zhao Gui Su
Keyword(s):  
Activation Energy ◽  
Thermal Analysis ◽  
Heat Flux ◽  
Polyurethane Foam ◽  
Chemical Reaction ◽  
Kinetics Study ◽  
Response Characteristics ◽  
Result Show ◽  
Calculated Activation Energy ◽  
Calculated Activation

This article uses the thermal analysis to study the kinetics characteristics of Polyurethane foam. The partially oxidized and non oxidized materials were used to study the variation of reaction of the smoldering, and the mechanism of function and activation energy of two substances was obtained. The result show that the oxygenolysis of the non oxidized Polyurethane foam belongs to the second-level chemical reaction, while the oxygenolysis of partially oxidized belongs to the first-level chemical reaction; the oxidization reaction of Polyurethane foam is a process which have lots of reaction steps to mutual promote as well as connection with each steps ; Through the smoldering experiment verify that the response characteristics of the two substances under the same heat flux to a certain extent, and the results agree well with the calculated activation energy.

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