Moisture Transport Mechanism and Drying Kinetic of Fresh Harvested Red Onion Bulbs under Dehumidified Air

2017 ◽  
Vol 13 (9) ◽  
Author(s):  
Nurul Asiah ◽  
Mohamad Djaeni ◽  
Ching Lik Hii
Keyword(s):  
Relative Humidity ◽  
Storage Time ◽  
Moisture Diffusion ◽  
Moisture Diffusivity ◽  
Transfer Model ◽  
Unsteady State ◽  
Mass Transfer Model ◽  
Drying Time ◽  
Onion Bulbs ◽  
Drying Kinetic

AbstractDrying plays an important role in post-harvest handling of onion for prolonging storage time. This research focuses on the drying studies of red onion bulbs using dehumidified air. The works were carried out by observing the microscopic structure of red onion bulbs layer and followed by developing mass transfer model for moisture diffusion during drying. Moisture diffusivity was estimated from drying experiments conducted at various temperatures (40, 50 and 60 °C) using the unsteady state solutions of Fick’s second law model. The diffusivity values were used to predict the drying kinetics as well as effective drying time for different air relative humidity. Results showed that combination of low relative humidity and low drying temperature significantly improved drying rate and reduced drying time.

scholarly journals Investigation of influence of pre-treatment and low-temperature on drying kinetics, sorption properties, shrinkage and color of brown seaweeds (Saccharina Latissima)

2018 ◽  
Author(s):  
Ignat Tolstorebrov ◽  
Trygve Magne Eikevik ◽  
Inna Petrova ◽  
Yulia Shokina ◽  
Michael Bantle
Keyword(s):  
Relative Humidity ◽  
Salt Content ◽  
Sorption Isotherms ◽  
Moisture Diffusivity ◽  
Drying Kinetics ◽  
Saccharina Latissima ◽  
Diffusivity Coefficient ◽  
High Accumulation ◽  
Drying Time ◽  
Brown Seaweeds

Drying kinetics of Saccharina latissima (raw and blanched) at low temperatures (10.0, 25.0 and 38.0 °C) was studied. The effective moisture diffusivity coefficient varied due to temperature alterations in the range between 1.4 and 4.5 10-10 m2/s for raw and 0.91 and 2.56 10-10 m2/s for blanched seaweeds. Significant changes in structural properties and chemical composition resulted in a much longer drying time of blanched seaweeds, when compared with raw. Drying temperature of 38.0 °C resulted in more brown color, when compared with other samples. Sorption characteristics of dried raw seaweeds depended on salt content and showed high accumulation of moisture at relative humidity of air of 80.0 %. The blanched seaweeds showed linear accumulation of moisture within increasing of relative humidity of drying air from 20.0 to 80.0 %, but high level of hysteresis was determined between sorption and desorption isotherms. The shrinkage development within dewatering of blanched and raw samples was also studied. Keywords: brown seaweeds, drying kinetics, sorption isotherms, color 

scholarly journals DRYING STUDY OF EUCALYTPTUS STAIGERIANA LEAVES BY MONITORING THE HUMIDITY OF THE DRYER DISCHARGE

2005 ◽  
Vol 4 (1) ◽  
Author(s):  
N. P. Braga ◽  
A. Starquit ◽  
M. A. Cremasco ◽  
J. O. Brito
Keyword(s):  
Relative Humidity ◽  
Moisture Content ◽  
Light Phase ◽  
Drying Time ◽  
Humidity Transducer ◽  
Drying Kinetic ◽  
Heavy Phase ◽  
Simultaneous Heat ◽  
Analytical Scale ◽  
Air Humidification

The drying phenomenon can be treated as simultaneous heat and mass transfer in both the light and heavy phases. In the present case, the phenomenon’s evolution is normally observed through the heating of and moisture removal from the heavy phase. On the other hand, while the material is heating, the light phase is cooling and humidifying. The goal of the present work is to present discharge air humidification curves as a function of the drying time for Eucalyptus staigeriana leaves drying experiments. For the air humidification measurements, a dry bulb thermocouple and relative humidity transducer were installed at both the dryer inlet and outlet. The dryer was linked to a data acquisition system, which recorded the dry bulb temperature and the relative humidity with time. These data were later used to calculate the air moisture content at the dryer inlet and outlet. The data obtained by this methodology are compared with the ones from drying kinetic (moisture content removing of the heavy phase along time), acquired by the evolution of wet material weight through the use of an analytical scale.

scholarly journals Impact of citric acid on the drying characteristics of kiwifruit slices

2020 ◽  
Vol 42 ◽  
pp. e40570
Author(s):  
Ibrahim Doymaz
Keyword(s):  
Regression Analysis ◽  
Citric Acid ◽  
Effective Diffusivity ◽  
Type Equation ◽  
Moisture Diffusion ◽  
Moisture Diffusivity ◽  
Diffusivity Coefficient ◽  
Drying Time ◽  
Drying Temperature ◽  
Drying Behaviour

Kiwifruit slices were dried at four different air drying temperatures of 50, 55, 60 and 70ºC and at 2 m s-1 air velocity by using a cabinet dryer in this study. The drying, rehydration and colour characteristics were significantly influenced by pretreatment and drying temperature. The drying time decreased with the increase in drying temperature. The drying rate curves showed that the entire drying process took place in the falling rate period. Five well-known thin-layer models were evaluated for moisture ratios using nonlinear regression analysis. The results of regression analysis indicated that the Midilli & Kucuk model the best to describe the drying behaviour with the lowest c2 and RMSE values, and highest R2 value. The effective moisture diffusivity of the dried kiwifruit slices was calculated with Fick’s diffusion model, in which their values varied from 4.19×10–10 to 6.99×10-10 m2 s-1 over the mentioned temperature range. The dependence of effective diffusivity coefficient on temperature was expressed by an Arrhenius type equation. The calculated values of the activation energy of moisture diffusion were 10.37 and 19.08 kJ mol-1 for citric acid and control samples, respectively

scholarly journals Ultrasonic-Microwave and Infrared Assisted Convective Drying of Carrot: Drying Kinetic, Quality and Energy Consumption

2020 ◽  
Vol 10 (18) ◽  
pp. 6309
Author(s):  
Yousef Abbaspour-Gilandeh ◽  
Mohammad Kaveh ◽  
Muhammad Aziz
Keyword(s):  
Energy Consumption ◽  
Hybrid Methods ◽  
Specific Energy Consumption ◽  
Moisture Diffusivity ◽  
Color Variation ◽  
Microwave Drying ◽  
Convective Drying ◽  
Drying Time ◽  
Drying Kinetic ◽  
The Us

In this study, the drying time, effective moisture diffusivity (Deff), specific energy consumption (SEC), and quality (color, shrinkage, and rehydration) of the ultrasound-pretreated (US) carrot slices were compared when dried by hot air drying (HD), microwave drying (MWD), infrared drying (INFD), and hybrid methods of MW–HD and INF–HD. Five mathematical models were considered to describe the drying kinetics in the carrots. The results show that US+MW–HD and INFD were the fastest and the slowest drying techniques compared to the HD technique with a 73% and 23% drying time reduction, respectively. The Deff ranged from 7.12 × 10−9 to 2.78 × 10−8 m2/s. The highest and lowest SECs were 297.29 ± 11.21 and 23.75 ± 2.22 MJ/kg which were observed in the HD and US+MWD, respectively. The color variation indices indicated that the best sample in terms of color stability was the one dried by US+MW–HD with the color variation of 11.02 ± 0.27. The lowest and highest shrinkage values were also observed in the samples dried by US+MWD and HD (31.8 ± 1.1% and 62.23 ± 1.77%), respectively. Samples dried by US+MWD and HD possessed the highest and lowest rehydration, respectively. Although the carrot slices dried at a higher pace by US+MW–HD (compared to US+MWD), the shrinkage and SEC of the samples dried by US+MWD were significantly lower than the US+MW–HD (p < 0.05). Therefore, it can be concluded that the application of the US+MWD method can be considered as a proper alternative for drying the carrot slices when compared to the HD, MWD, INFD, and hybrid methods.

scholarly journals A Novel Passive Method for Regulating Both Air Temperature and Relative Humidity of the Microenvironment in Museum Display Cases

Energies ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3768 ◽  
Author(s):  
Meng Yu ◽  
Xuejun Zhang ◽  
Yang Zhao ◽  
Xiaobin Zhang
Keyword(s):  
Relative Humidity ◽  
Phase Change ◽  
Silica Gel ◽  
Air Temperature ◽  
Water Vapor Permeability ◽  
Moisture Diffusivity ◽  
Vapor Permeability ◽  
Transfer Model ◽  
Passive Method ◽  
Museum Display

Display cases are widely utilized in museums to build an appropriate microenvironment for artifacts. In this study, a novel passive method is utilized to regulate both the temperature and relative humidity simultaneously of the microenvironment in museum display cases by proposing the concept of composite temperature and humidity control materials (CTHCM), which can be fabricated by combining both phase change material (PCM) and silica gel. The PCM is helpful to reduce the range of air temperature changes caused by melting or solidification processes, while the silica gel is helpful to reduce the range of relative humidity changes caused by adsorption or desorption processes. In this study, a coupled heat and mass transfer model is established to analyze the temperature-regulating and humidity-regulating performance of CTHCM using the software COMSOL Multiphysics. The influences of thermodynamic parameters of materials on temperature-regulating and humidity-regulating performance are also analyzed numerically. Results show that CTHCM is able to regulate the air temperature and relative humidity of the microenvironment in museum display cases effectively. It performs well in temperature-regulating as the phase change latent heat increases, and performs well in humidity-regulating as the water vapor permeability or moisture diffusivity increases.

High humidity air-impingement blanching (HHAIB) improves drying characteristics and quality of ground-cover chrysanthemum heads

2020 ◽  
Vol 16 (12) ◽  
Author(s):  
Jian-Wu Dai ◽  
Jie Wang ◽  
Sheng-Lin Yang ◽  
Meng-Da Wen ◽  
Peng-Fei Yin ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Ground Cover ◽  
Control Group ◽  
Total Flavonoids ◽  
High Humidity ◽  
Drying Time ◽  
Drying Kinetic ◽  
Air Impingement ◽  
Total Flavonoids Content

AbstractEffects of high humidity air-impingement blanching (HHAIB) temperature, relative humidity over a range of application time and drying temperature on air-impingement drying kinetics, colour attributes, browning index, blanching weight loss and total flavonoids content of chrysanthemum heads were studied. HHAIB could shorten the drying time of chrysanthemum heads significantly (p < 0.05) by up to 52% compared to the control group without blanching. Meanwhile blanching humidity has a greater influence on drying kinetic than other blanching parameters. Deff values of samples declined first and rose later with the growth of blanching humidity, while increased continuously with the growth of blanching temperature. The highest growth of total flavonoids content can be up to 21.6% under the HHAIB blanching conditions (110 °C of blanching temperature, 45% of relative humidity, 150 s of blanching time) in comparison with the control group. Lightness of all blanched samples was lower than the control group, and redness and total colour difference under different blanching conditions showed significant differences compared to the control group, while no obvious variation was observed in terms of yellowness values.

scholarly journals Effects of sonication and freezing on the color, mechanical and thermophysical properties of osmo-microwave-vacuum dried cranberries

2020 ◽  
Author(s):  
Izabela Anna Staniszewska ◽  
Szymon Staszyński ◽  
Magdalena Zielińska
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Diffusivity ◽  
Moisture Diffusion ◽  
Moisture Diffusivity ◽  
Microwave Drying ◽  
Vacuum Drying ◽  
Volumetric Heat Capacity ◽  
Drying Time ◽  
Microwave Vacuum Drying

The aim of study was to determine the effects of sonication (S), convective freezing (F), convective freezing preceded by sonication (SF) as well as cryogenic freezing (N) on the osmo-microwave-vacuum drying kinetics, energy usage and properties of dried cranberries such as moisture content, moisture diffusion, water activity, density, porosity, thermal conductivity, thermal diffusivity, volumetric heat capacity, lightness, redness, yellowness, total differences in color, saturation and hue, hardness, cohesiveness, springiness, and chewiness. Osmo-microwave-vacuum drying of cranberries took from 13.5 to 16.0 min. All initial treatments increased the moisture diffusivity and thus reduced the drying time. The most energy effective method was osmo-microwave-vacuum drying preceded by sonication (S) of fruits. Osmo-microwave-drying of cranberries subjected to convective freezing preceded by sonication (SF) resulted in the highest lightness (32.5 ± 0.5), redness (33.9 ± 0.7), and yellowness (11.3 ± 0.5) of fruits, as well as the lowest cohesion (the lowest resistant to stress associated with manufacturing, packaging, storage, and delivery). The lowest hardness, i.e. 12.3 ± 0.4 N and the highest cohesiveness and springiness, i.e. 0.38 ± 0.02 and 0.74 ± 0.03 of dried fruits, were noted for berries subjected to initial cryogenic freezing (N). Cryogenic freezing (N) combined with osmo-microwave-vacuum drying resulted in the largest color changes of fruits and the highest thermal conductivity. Sonicated and convectively frozen (SF) fruits were characterized by the highest thermal diffusivity. Sonication (S), convective freezing (F) and their combination (SF) significantly reduced the volumetric heat capacity of cranberry fruits.

Transient simultaneous heat and mass transfer model to estimate drying time in a wetted fur of a cow

2020 ◽  
Vol 195 ◽  
pp. 116-135
Author(s):  
Elizabeth Chen ◽  
Vinod Narayanan ◽  
Theresa Pistochini ◽  
Erfan Rasouli
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Transfer Model ◽  
Mass Transfer Model ◽  
Drying Time ◽  
Simultaneous Heat

Moisture diffusivity and response time in fine forest fuels

1990 ◽  
Vol 20 (3) ◽  
pp. 315-325 ◽  
Author(s):  
Hal E. Anderson
Keyword(s):  
Relative Humidity ◽  
Response Time ◽  
Response Times ◽  
Volume Ratio ◽  
Moisture Diffusion ◽  
The United States ◽  
Moisture Diffusivity ◽  
Fire Danger ◽  
Forest Fuels ◽  
Fine Fuels

Fine forest fuels, such as grasses, hardwood leaves, and conifer needles, vary greatly in response times and mean moisture diffusion coefficients when exposed to desorption and adsorption conditions. Results are reported for tests made with recently dead and weathered dead fine forest fuels and small woody samples. Test conditions were 26.7 °C (80°F) with changes in relative humidity from 90 to 20% and back, in an environmental chamber. Moisture diffusivities of fine forest fuels were found to be smaller than diffusivities of woody samples. The diffusivities of the foliage and grass fuels tested ranged from near 1.0 × 10−10 to 1.0 × 10−8 cm2/s, whereas the woody fuels ranged from 1.5 × 10−7 to3.0 × 10−5 cm2/s. Weathered fine fuels had faster response times and higher diffusivities than recently cast materials. Adsorption response times were longer and diffusivities lower than for fuels in desorption. Response times of various recently dead fine fuels ranged from 0.2 to 37 h and weathered fuels from 0.5 to 10 h. Therefore, specific fuel types need to be tested to assign more precise response times. Under the drying conditions of 26.7 °C and 20% relative humidity, fine forest fuels had lower diffusivities and longer response times than anticipated in the United States National Fire Danger Rating System. As a result, predicted fire danger during or after a weather change may be overestimated because fuels are responding more slowly than anticipated. Equations are presented for making first estimates of response time and (or) diffusivity if certain physical properties are known: surface area-to-volume ratio, packing ratio, and bed depth.

scholarly journals DRYING STUDY OF EUCALYTPTUS STAIGERIANA LEAVES BY MONITORING THE HUMIDITY OF THE DRYER DISCHARGE

2005 ◽  
Vol 4 (1) ◽  
pp. 13
Author(s):  
N. P. Braga ◽  
A. Starquit ◽  
M. A. Cremasco ◽  
J. O. Brito
Keyword(s):  
Relative Humidity ◽  
Moisture Content ◽  
Light Phase ◽  
Drying Time ◽  
Humidity Transducer ◽  
Drying Kinetic ◽  
Heavy Phase ◽  
Simultaneous Heat ◽  
Analytical Scale ◽  
Air Humidification

The drying phenomenon can be treated as simultaneous heat and mass transfer in both the light and heavy phases. In the present case, the phenomenon’s evolution is normally observed through the heating of and moisture removal from the heavy phase. On the other hand, while the material is heating, the light phase is cooling and humidifying. The goal of the present work is to present discharge air humidification curves as a function of the drying time for Eucalyptus staigeriana leaves drying experiments. For the air humidification measurements, a dry bulb thermocouple and relative humidity transducer were installed at both the dryer inlet and outlet. The dryer was linked to a data acquisition system, which recorded the dry bulb temperature and the relative humidity with time. These data were later used to calculate the air moisture content at the dryer inlet and outlet. The data obtained by this methodology are compared with the ones from drying kinetic (moisture content removing of the heavy phase along time), acquired by the evolution of wet material weight through the use of an analytical scale.

Sign in / Sign up

Export Citation Format

Share Document