scholarly journals Study on drying kinetics of summer onion

2015 ◽  
Vol 39 (4) ◽  
pp. 661-673 ◽  
Author(s):  
Md Masud Alam ◽  
Md Nurul Islam ◽  
Md Nazrul Islam
Keyword(s):  
Activation Energy ◽  
Mass Transfer ◽  
Rate Constant ◽  
Variable Temperature ◽  
Air Flow ◽  
Drying Kinetics ◽  
Effect Of Temperature ◽  
Drying Rate ◽  
External Resistance ◽  
Kinetics Of

The present study was concerned with the kinetics of drying of summer onion. Drying was done in a mechanical dryer at constant air flow using blanched and unblanched onion with variable temperature (52, 60 and 680C) and thickness (3, 5 and 7 mm). Drying rate was increased with increase of temperature and decreased with the increase in thickness in blanched and unblanched onion. Blanched onion showed higher drying rate than unblanched onion. Drying rate constant and thickness can be expressed as power low equations. The value of index “n” were found to be 1.277 and 0.845 for onion indicating that the external resistance to mass transfer was highly significant. The effect of temperature on diffusion co-efficient follows an Arrhenius type relationship. The activation energy (Ea) for diffusion of water was found 5.781 Kcal/g-mole for unblanched and 2.46 Kcal/g-mole for blanched onion when onions were dried in mechanical dryer. DOI: http://dx.doi.org/10.3329/bjar.v39i4.22545 Bangladesh J. Agril. Res. 39(4): 661-673, December 2014

Effect of Air Temperature on Convective Drying Assisted by High Power Ultrasound

2006 ◽  
Vol 258-260 ◽  
pp. 563-574 ◽  
Author(s):  
J.V. García-Pérez ◽  
Carmen Rosselló ◽  
J.A. Cárcel ◽  
Susana De la Fuente ◽  
A. Mulet
Keyword(s):  
Mass Transfer ◽  
Air Temperature ◽  
Drying Kinetics ◽  
Drying Rate ◽  
External Resistance ◽  
Experimental Conditions ◽  
Power Ultrasound ◽  
Effective Moisture ◽  
High Power Ultrasound ◽  
Er Model

Drying kinetics of carrot cubes were carried out at 1 m/s air velocity at different air drying temperatures (30, 40, 50, 60 and 70±0.1 °C) (AIR experiments), and also at the same experimental conditions but applying high power ultrasound (US experiments). Two kind of diffusion models were used to simulate the drying kinetics, according to external resistance to mass transfer being considered (ER model) or neglected (NER model) for solving the diffusion equation. Diffusion ER model was solved using a finite difference method. Drying rate increased as air temperature was higher. Ultrasound also increased drying rate at the different temperatures, but the improvement on drying rate decreased at high temperatures, and almost disappeared at 70 °C. Effective moisture diffusivities only showed an Arrhenius type relationship with temperature for AIR experiments. The NER diffusion model was not accurate to simulate the drying kinetics at any experimental conditions tested. However, diffusion ER model provided a high closeness between experimental and calculated drying data (VAR>99.80). Through the parameters identified of the ER diffusion model, effective moisture diffusivity and mass transfer coefficient, the influence of the power ultrasound application on internal and external resistance to mass transfer was shown to be significant (p<0.05).

Effect of Air Velocity and Temperature on the Drying Kinetics of Drumstick Leaves (Moringa Oleifera)

2012 ◽  
Vol 8 (4) ◽  
Author(s):  
Monica Premi ◽  
Harish Sharma ◽  
Ashutosh Upadhyay
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Moringa Oleifera ◽  
Moisture Diffusivity ◽  
Drying Kinetics ◽  
Drying Rate ◽  
Air Velocity ◽  
Drying Time ◽  
Effective Moisture ◽  
Kinetics Of

Abstract The present study examines the effect of air velocity on drying kinetics of the drumstick leaves in a forced convective dryer. The drumstick leaves were dried in the temperature range of 50–800 C, at different air velocity (Dv) of 0.5 and 1.3 m/s. The results indicated that drying temperature and air velocity are the factors in controlling the drying rate. Experimental data obtained for the samples for color, drying rate and drying time proved that air velocity of 1.3 m/s yielded the product superior in terms of both quality and energy efficiency as compared to the samples at 0.5 m/s. Activation energy for drumstick leaves dried with air velocity, 0.5 and 1.3 m/s was 12.50 and 32.74 kJ/mol respectively. The activation energy relates similarly with the effective moisture diffusivity which also increased with increase in air velocity and temperature.

THE REACTION BETWEEN CYANATE AND HYPOCHLORITE

1956 ◽  
Vol 34 (4) ◽  
pp. 489-501 ◽  
Author(s):  
M. W. Lister
Keyword(s):  
Activation Energy ◽  
Ionic Strength ◽  
Rate Constant ◽  
Hypochlorous Acid ◽  
Effect Of Temperature ◽  
Slow Step ◽  
True Activation Energy ◽  
Rate Of Reaction ◽  
Different Temperatures ◽  
Kinetics Of

The reaction between sodium hypochlorite and potassium cyanate in the presence of sodium hydroxide has been examined. The main products are chloride, and carbonate ions and nitrogen; but, especially if much hypochlorite is present, some nitrate is formed as well. The rate of reaction is proportional to the cyanate and hypochlorite concentrations, but inversely proportional to the hydroxide concentration: the rate constant is 5.45 × 10−4 min.−1 at 65 °C, at an ionic strength of 2.2. The rate constant increases somewhat as the ionic strength rises from 1.7 to 3.5. The effect of temperature makes the apparent activation energy 25 kcal./gm-molecule. The kinetics of the reaction suggest that the slow step is really a reaction of hypochlorous acid and cyanate ions, and possible intermediate products of this reaction are suggested. Allowing for the different extent of hydrolysis of hypochlorite at different temperatures, the true activation energy is found to be 15 kcal./gm-mol., which is consistent with the observed rate of reaction.

scholarly journals Kinetics of Dehydration of Aroids and Developed Dehydrated Aroids Products

2010 ◽  
pp. 19-24
Author(s):  
M Kamruzzaman ◽  
MN Islam
Keyword(s):  
Mass Transfer ◽  
Rate Constant ◽  
Chemical Engineering ◽  
Raw Materials ◽  
Drying Rate ◽  
Chemical Compositions ◽  
Air Velocity ◽  
Transfer Resistance ◽  
Power Law Equation ◽  
Kinetics Of

The study was concerned with the dehydration kinetics of aroids in mechanical dryer at different dryingcondition such as variable air dry bulb temperature and air velocity. Fresh aroids with 3, 5 mm slice and 8mm cube were used as raw materials for drying. The experimental results showed that drying rate constantand thickness can be expressed as power law equation. The exponent of the equation for aroids was 1.15indicating presence of significance external mass transfer resistance. Increasing loading density gavedecreased drying rate constant and when air velocity of dryer was increased, drying rate constant was alsoincreased, as higher air velocity reduces the external resistance to mass transfer and also highertemperature gave faster drying rate. The activation energy of diffusion of water from aroids during dryingas per Arrhenius equation was found to be 5.12 k cal/g-mole. The chemical compositions of fresh and driedaroids were determined and it was observed that all the constituent remained almost constant, only fatdecreased slightly possibly due to oxidation. Organoleptic taste testing showed that “chapatti” preparedfrom aroids powder (aroids powder: wheat flour = 1:4) were adjudged to be the best by the panelists using1-9 hedonic scale and ranked as like moderately securing score 7.3.Journal of Chemical Engineering Vol.ChE 24 2006 19-24

Mass Transfer Parameters and Modeling of Hot Air Drying Kinetics of Dill Leaves

2016 ◽  
Vol 12 (2) ◽  
Author(s):  
Hosain Darvishi ◽  
Zanyar Farhudi ◽  
Nasser Behroozi-Khazaei
Keyword(s):  
Activation Energy ◽  
Mass Transfer ◽  
Moisture Content ◽  
Moisture Diffusivity ◽  
Drying Kinetics ◽  
Transfer Model ◽  
Hot Air ◽  
Drying Behavior ◽  
Kinetics Of ◽  
Best Fit

Abstract Moisture diffusivity (Dem), mass transfer coefficient (hm), activation energy and drying kinetics of the dill leaves were studied and modeled as a function of temperature (40–70 °C) and moisture content (0.20–5.67 kg water/kg dry matter). Results showed that the Dem and hm significantly depend on the temperature and moisture content (p < 0.05). The average of Dem and hm varied between 4.02 × 10–9 to 9.65 × 10–9 m2/s, and 2.38 × 10–7 to 6.33 × 10–7 m/s, respectively. Activation energy showed a significant dependence on the moisture content and estimated as 16.84 kJ/mol for diffusion model and 28.70 kJ/mol for mass transfer model. Out of the six models considered, the logarithmic model showed the best fit to drying behavior of the dill leaves.

scholarly journals Evaluation of a Moisture Diffusion Model for Analyzing the Convective Drying Kinetics of Lavandula x allardii Leaves

Computation ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 141
Author(s):  
Vasileios Chasiotis ◽  
Dimitrios Tzempelikos ◽  
Andronikos Filios
Keyword(s):  
Diffusion Model ◽  
Moisture Transfer ◽  
Variable Temperature ◽  
Moisture Diffusion ◽  
Drying Kinetics ◽  
Convective Drying ◽  
Water Evaporation ◽  
Drying Rate ◽  
Computationally Efficient ◽  
Kinetics Of

In the present case study, a moisture diffusion model is developed to simulate the drying kinetics of Lavandula x allardii leaves for non-stationary convective drying regimes. Increasing temperature profiles are applied over the drying duration and the influence of temperature advancing rates on the moisture removal and the drying rate is investigated. The model assumes a one-dimensional moisture transfer under transient conditions, which occurs from the leaf center to the surface by liquid diffusion due to the concentration gradient developed by the surface water evaporation caused by the difference of water vapor partial pressure between the drying medium and the leaf surface. A numerical solution of Fick’s 2nd law is obtained by an in-house code using the finite volume method, including shrinkage and a variable temperature-dependent effective moisture diffusion coefficient. The numerical results have been validated against experimental data for selected cases using statistical indices and the predicted dehydration curves presented a good agreement for the higher temperature advancing rates. The examined modeling approach was found stable and can output, in a computationally efficient way, the temporal changes of moisture and drying rate. Thus, the present model could be used for engineering applications involving the design, optimization and development of drying equipment and drying schedules for the examined type of non-stationary drying patterns.

Study on the Drying Mechanism and Dynamics of Palygorskite

2011 ◽  
Vol 422 ◽  
pp. 501-504
Author(s):  
Jiang Quan Ma ◽  
Qing Ling Lu ◽  
Jun Hao Xia ◽  
Xiao Bin Gan ◽  
Chao Yao
Keyword(s):  
Activation Energy ◽  
Environmental Protection ◽  
Drying Kinetics ◽  
Diffusion Activation Energy ◽  
Drying Rate ◽  
Drying Process ◽  
Drying Curves ◽  
Kinetics Of ◽  
Diffusion Activation

Palygorskite had large applications in chemical, environmental protection, medicine processes and so on. However, since the mineral limitations of natural palygorskite, both improving its quality and meeting the need of industry, palygorskite usually needs to be activated before using it. The influences of activation during the drying process were studied, as well as the drying kinetics of the non-activated of palygorskite. The results showed that the drying rate of palygorskite increased at first, and then came to a constant value, and kept that value for some time. After that, drying rate decreased with time going. Compared with drying curves of the non activated palygorskite, the samples made some changes after activation. The drying process of non activated palygorskite could be described as the equation of MR=exp(-ktn). The diffusion activation energy (E) of non activated palygorskite was equal to 17.14kJ•mol-1, former factors of Arrhenius was equal to 4.19×10-5 m2•s-1.

Study on the Drying Mechanism and Dynamics of Palygorskite

2013 ◽  
Vol 706-708 ◽  
pp. 456-459
Author(s):  
Shi Long Wang ◽  
Li Na Wang
Keyword(s):  
Activation Energy ◽  
Environmental Protection ◽  
Drying Kinetics ◽  
Diffusion Activation Energy ◽  
Drying Rate ◽  
Drying Process ◽  
Drying Curves ◽  
Kinetics Of ◽  
Diffusion Activation

Palygorskite had large applications in chemical, environmental protection, medicine processes and so on. However, since the mineral limitations of natural palygorskite, both improving its quality and meeting the need of industry, palygorskite usually needs to be activated before using it. The influences of activation during the drying process were studied, as well as the drying kinetics of the non-activated of palygorskite. The results showed that the drying rate of palygorskite increased at first，and then came to a constant value, and kept that value for some time. After that, drying rate decreased with time going. Compared with drying curves of the non activated palygorskite, the samples made some changes after activation. The drying process of non activated palygorskite could be described as the equation of MR=exp(-ktn).The diffusion activation energy (E) of non activated palygorskite was equal to 17.14kJ.mol-1, former factors of Arrhenius was equal to 4.19×10-5 m2.s-1.

Drying Kinetics of Malaysian Paddy (Group D Particles) in Spouted Bed Dryer

2006 ◽  
Vol 2 (3) ◽  
Author(s):  
Pin Pin Ng ◽  
Chung Lim Law ◽  
Siti Masrinda Tasirin
Keyword(s):  
Draft Tube ◽  
Air Flow ◽  
Drying Kinetics ◽  
Drying Rate ◽  
Spouted Bed ◽  
Bed Height ◽  
Internal Structures ◽  
Drying Curves ◽  
Group D ◽  
Kinetics Of

Spouted bed is suitable for drying of coarse particles which are Group D of Geldart’s particle classification. Malaysian grown paddy was used as a Group D sample in a lab-scale spouted bed dryer. Drying was carried out in two different internal structures of the dryer, namely with or without the installation of a draft tube, and at several drying temperatures, air flow rates as well as bed heights. Spouted bed drying kinetics of paddy presented in drying curves showed only induction and falling rate periods, without constant drying rate period. The highest drying rate was achieved when paddy was dried without draft tube at low bed height, high drying temperature and air flow rate.

scholarly journals Drying Kinetics of Noni Seeds

2019 ◽  
Vol 11 (5) ◽  
pp. 250 ◽  
Author(s):  
Wellytton Darci Quequeto ◽  
Osvaldo Resende ◽  
Patrícia Cardoso Silva ◽  
Fábio Adriano Santos e Silva ◽  
Lígia Campos de Moura Silva
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Diffusion Coefficient ◽  
Moisture Content ◽  
Mathematical Models ◽  
Effective Diffusion Coefficient ◽  
Effective Diffusion ◽  
Information Criterion ◽  
Drying Kinetics ◽  
Kinetics Of

Noni seeds have been used for years as an important medicinal source, with wide use in the pharmaceutical and food industry. Drying is a fundamental process in the post-harvest stages, where it enables the safe storage of the product. Therefore, the present study aimed to fit different mathematical models to experimental data of drying kinetics of noni seeds, determine the effective diffusion coefficient and obtain the activation energy for the process during drying under different conditions of air temperature. The experiment used noni seeds with initial moisture content of 0.46 (decimal, d.b.) and dehydrated up to equilibrium moisture content. Drying was conducted under different controlled conditions of temperature, 40; 50; 60; 70 and 80 &ordm;C and relative humidity, 24.4; 16.0; 9.9; 5.7 and 3.3%, respectively. Eleven mathematical models were fitted to the experimental data. The parameters to evaluate the fitting of the mathematical models were mean relative error (P), mean estimated error (SE), coefficient of determination (R2), Chi-square test (c2), Akaike Information Criterion (AIC) and Schwarz&rsquo;s Bayesian Information Criterion (BIC). Considering the fitting criteria, the model Two Terms was selected to describe the drying kinetics of noni seeds. Effective diffusion coefficient ranged from 8.70 to 23.71 &times; 10-10 m2 s-1 and its relationship with drying temperature can be described by the Arrhenius equation. The activation energy for noni seeds drying was 24.20 kJ mol-1 for the studied temperature range.

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