scholarly journals INFRARED DEHYDRATION OF BLANCHED QUINCE SLICES: STUDY ON PROCESS AND MASS TRANSFER CHARACTERISTICS

2021 ◽  
Vol 51 (4) ◽  
pp. 241-247
Author(s):  
Mohsen Beigi
Keyword(s):  
Mass Transfer ◽  
Moisture Diffusion ◽  
Moisture Diffusivity ◽  
Moisture Removal ◽  
Convective Mass Transfer ◽  
External Resistance ◽  
Flow Rates ◽  
Surface Mass ◽  
Mass Evaporation ◽  
Biot Numbers

In the present work, moisture removal characteristics of quince slices in a convective tray dryer were studied. The blanched slices (with thicknesses of 3, 5 and 7 mm) were dried at drying temperatures of 50, 60 and 70 °C and air flow rates of 1, 1.5 and 2 m/s. The analytical model proposed by Dincer and Dost was used to determine the mass transfer parameters. The obtained Biot numbers (0.108‒0.293) revealed that both the internal and external resistance control the moisture diffusion within the samples. The moisture diffusivity and convective mass transfer coefficient were found to be in the ranges of 1.578×10-7‒7.331×10-7 m2/s and 2.040×10-5‒3.507×10-5 m/s, respectively. The activation energies for moisture diffusion and surface mass evaporation were determined to be in the ranges of 17.607 to 48.019 kJ/mol and 5.270 to 27.430 kJ/mol, respectively.

scholarly journals Diffusion of Moisture in a Cigarette Tobacco Column at Room Conditions

2004 ◽  
Vol 21 (1) ◽  
pp. 15-24
Author(s):  
IH Oh ◽  
GR Jheong
Keyword(s):  
Mass Transfer ◽  
Moisture Content ◽  
Mathematical Models ◽  
Moisture Diffusion ◽  
Moisture Diffusivity ◽  
Convective Mass Transfer ◽  
Transfer Coefficients ◽  
Long Term Storage ◽  
Effective Moisture ◽  
Experimental Values

AbstractThe moisture content of cigarettes has a significant impact on the shelf life and the taste of the products as well as various physical properties of cigarettes including loose ends, burning rate, hardness, and pressure drop. To prepare better products it would be helpful to develop proper mathematical models for the simulation of moisture diffusion characteristic dynamics in a cigarette. In this work, four mathematical models have been developed with appropriate assumptions adequate to analyze the dynamics of moisture diffusion in cigarettes. The simulation of the derived models was also carried out in this work. When the theoretical values produced from each model were compared with the corresponding experimental data, it was found that three models (I-II, II, III) can be used to explain the behavior of moisture in cigarettes. Convective mass transfer coefficients and effective moisture diffusivities that fit best were obtained by a regression analysis of the model using the experimental values. The simulation of the models revealed that there is no significant positional dependence of moisture content inside a tobacco column because most of the moisture dries out radially through the cigarette wrapper. The drying rate of moisture in a tobacco column is rarely affected by effective moisture diffusivity, but strongly influenced by convective mass transfer. To prevent quality deterioration of the cigarettes during long-term storage, it is concluded that improvement of the cigarette wrapper and air tightness of the package, which are directly related to the convective mass transfer, is very important.

scholarly journals DRYING OF ZUCCHINI AND CARROT SLICES: INFLUENCE OF TISSUE STRUCTURE ON MASS TRANSFER PARAMETERS

2022 ◽  
Vol 52 (1) ◽  
pp. 49-54
Author(s):  
Farhad Khoshnam
Keyword(s):  
Activation Energy ◽  
Mass Transfer ◽  
Microwave Power ◽  
Moisture Diffusivity ◽  
Tissue Structure ◽  
Moisture Removal ◽  
Average Activation Energy ◽  
Rate Period ◽  
Transfer Parameters

The present work aimed mainly at investigating the influence of tissue structure on dehydration characteristics of zucchini and carrot. Microwave power levels of 100, 350, 550 and 750 W used to dehydrate the samples with thicknesses of 3, 5, 7 and 9 mm. The results showed that moisture removal from the slices occurred in a short accelerating period at the process beginning followed by a falling rate period. The moisture diffusivity increased with both increasing microwave power and the samples thickness where the average values for zucchini and carrot slices changed from 1.17×10-8 to 9.42×10-8 and from 0.73×10-8 to 5.51×10-8 m2 s-1, respectively. The average activation energy for zucchini and carrot slices varied in the range of 1.22–1.68 and 1.57–1.84 W g-1, respectively and decreased with increasing samples thickness.

scholarly journals Kinetika Pengeringan Lapisan Tipis Daun Jati Belanda (Thin Layer Drying Kinetics of Guazuma Ulmifolia Leaves)

2021 ◽  
Vol 8 (2) ◽  
pp. 53-62
Author(s):  
Hendri Syah ◽  
Armansyah Halomoan Tambunan ◽  
Edy Hartulistiyoso ◽  
Lamhot Parulian Manalu
Keyword(s):  
Mass Transfer ◽  
Thin Layer ◽  
Moisture Diffusivity ◽  
Drying Kinetics ◽  
Coefficient Of Determination ◽  
Convective Mass Transfer ◽  
Thin Layer Drying ◽  
Drying Models ◽  
Guazuma Ulmifolia ◽  
Kinetics Of

The objectives of this study were to determine a suitable thin layer drying model to describe the drying kinetics of Guazuma ulmifolia leaves and determine the mass transfer parameters of Guazuma ulmifolia leaves. The drying of Guazuma ulmifolia leaves was conducted in a laboratory scale dryer with various temperature (40oC, 50oC, and 60oC) and relative humidity (30%, 40%, 50% and 60%). Five drying models, namely, Newton, Henderson and Pabis, Page, Midilli-Kucuk, and Verma et al. were fitted to the drying data. The drying curve of guazuma leaves did not show a constant drying period during the drying period. The models suitability were compared base on coefficient of determination (R2), root square mean errors (RSME), and reduced mean square of deviation (X2). It was found that, among the models evaluated, the Midilli and Kucuk model is the best to describe the drying kinetics of Guazuma ulmifolia leaves. The effective moisture diffusivity was found to be in the range of 10-13 – 10-12 m2/s and the convective mass transfer coefficient was in the range of 10-9 – 10-10 m/s. The activation energy value was found to be 89.21 kJ/mol.

Experimental Study of Natural Convective Mass Transfer from Downward Pointing Conical Surfaces in Porous Media

2007 ◽  
Vol 10 (3) ◽  
pp. 277-286 ◽  
Author(s):  
Martin J. Garland ◽  
S. U. Rahman ◽  
K. A. Mahgoub ◽  
Ahmad Nafees
Keyword(s):  
Mass Transfer ◽  
Experimental Study ◽  
Porous Media ◽  
Convective Mass Transfer ◽  
Conical Surfaces

The effect of two-phase flow regime on hydrodynamics and mass transfer in a horizontal-tube gas-liquid reactor

1985 ◽  
Vol 50 (3) ◽  
pp. 745-757 ◽  
Author(s):  
Andreas Zahn ◽  
Lothar Ebner ◽  
Kurt Winkler ◽  
Jan Kratochvíl ◽  
Jindřich Zahradník
Keyword(s):  
Mass Transfer ◽  
Pressure Drop ◽  
Flow Regime ◽  
Liquid Flow ◽  
Horizontal Tube ◽  
Liquid Holdup ◽  
Two Phase ◽  
Flow Rates ◽  
Type Relation ◽  
Good Agreement

The effect of two-phase flow regime on decisive hydrodynamic and mass transfer characteristics of horizontal-tube gas-liquid reactors (pressure drop, liquid holdup, kLaL) was determined in a cocurrent-flow experimental unit of the length 4.15 m and diameter 0.05 m with air-water system. An adjustable-height weir was installed in the separation chamber at the reactor outlet to simulate the effect of internal baffles on reactor hydrodynamics. Flow regime maps were developed in the whole range of experimental gas and liquid flow rates both for the weirless arrangement and for the weir height 0.05 m, the former being in good agreement with flow-pattern boundaries presented by Mandhane. In the whole range of experi-mental conditions pressure drop data could be well correlated as a function of gas and liquid flow rates by an empirical exponential-type relation with specific sets of coefficients obtained for individual flow regimes from experimental data. Good agreement was observed between values of pressure drop obtained for weirless arrangement and data calculated from the Lockhart-Martinelli correlation while the contribution of weir to the overall pressure drop was well described by a relation proposed for the pressure loss in closed-end tubes. In the region of negligible weir influence values of liquid holdup were again succesfully correlated by the Lockhart-Martinelli relation while the dependence of liquid holdup data on gas and liquid flow rates obtained under conditions of significant weir effect (i.e. at low flow rates of both phases) could be well described by an empirical exponential-type relation. Results of preliminary kLaL measurements confirmed the decisive effect of the rate of energy dissipation on the intensity of interfacial mass transfer in gas-liquid dispersions.

Free Convective Mass Transfer at Isosceles Triangular Surfaces of Varying Inclination

2003 ◽  
Vol 68 (11) ◽  
pp. 2080-2092 ◽  
Author(s):  
Martin Keppert ◽  
Josef Krýsa ◽  
Anthony A. Wragg
Keyword(s):  
Mass Transfer ◽  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Mass Transfer Process ◽  
Sulfate Solution ◽  
Convective Mass Transfer ◽  
Varying Length ◽  
Inclined Surface ◽  
Vertical Case ◽  
Limiting Diffusion Current

The limiting diffusion current technique was used for investigation of free convective mass transfer at down-pointing up-facing isosceles triangular surfaces of varying length and inclination. As the mass transfer process, copper deposition from acidified copper(II) sulfate solution was used. It was found that the mass transfer rate increases with inclination from the vertical to the horizontal position and decreases with length of inclined surface. Correlation equations for 7 angles from 0 to 90° were found. The exponent in the ShL-RaL correlation ranged from 0.247 for the vertical case, indicating laminar flow, to 0.32 for inclinations of 60 to 90°, indicating mixed or turbulent flow. The general correlation ShL = 0.358(RaL sin θ)0.30 for the RaL sin θ range from 7 × 106 to 2 × 1011 and inclination range from 15 to 90° was obtained.

Convective mass transfer around a dissolving bubble

2017 ◽  
Vol 2 (11) ◽  
Author(s):  
Jerome Duplat ◽  
Mathieu Grandemange ◽  
Cedric Poulain
Keyword(s):  
Mass Transfer ◽  
Convective Mass Transfer
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