• Applied Biological Chemistry
• /
• v.25 no.3
• /
• pp.111-118
• /
• 1982

A closed solar collector drying system by water exchange was evaluated for the drying of ginseng. The thermal efficiency of solar collector, drying efficiency, drying characteristics and product quality were investigated. The drying period was reduced by one-thirds in comparison with typical method. The maximum and minimum thermal efficiency of the solar collector during drying period were 14.42%, and 4.73%, respectively. The drying efficiency of solar collector and control system showed 28.34%, and 13.45%, respectively; net drying efficiency being 14.8%. The drying rate curve of red ginseng showed only falling rate period, and its equation was $Y=50.7023t.^{-0.4138}$ The brown color intensity of red ginseng was higher in solar collector drying system than in typical method, and reductivity by diphenyl picryl hydrazil solution in red ginseng extract showed similar result to brown color intensity.

• Journal of the Korean Chemical Society
• /
• v.16 no.2
• /
• pp.106-116
• /
• 1972

The universality of the pseudo wet bulb temperature has been established in the drying of macroporous inerts, microporous inerts, and microporous swellable materials using water and methyl alcohol as the liquids. The pseudo wet bulb temperature is a new constant temperature intermediate between the wet bulb and dry bulb temperatures of the air during the second falling rate period. This temperature is calculated from consideration of the heat transfer to, and vapor diffusion from, liquid evaporating at the liquid-air boundary. The experimental results agree with that calculated from the equation proposed by Nissan, Bolles and George.

• Proceedings of the Korean Society for Agricultural Machinery Conference
• /
• v.10 no.2
• /
• pp.137-145
• /
• 2005

The effects of air temperature and sample thickness on drying kinetics of strawberry leather were investigated. The mathematical modeling was performed by using three thin-layer dying models. The independent variables were sample thickness (S1 = 1.8, S2 = 2.7, and S3 = 3.6mm) and air temperature (50, 60, 70, and 80$^{\circ}$C). All samples took place in the falling rate period. The values of effective moisture diffusivity, D$_{eff}$ varied from 2.40 to 12.1$^{\times}$10-9m$^{2}$/s depending on drying conditions. The values of activation energy, E$_{a}$ were 35.57, 33.14, and 30.46 KJ/mol for each sample of S1, S2, and S3. The two-term exponential model was found to satisfactorily describe the thin-layer drying kinetics of strawberry leather.

• Korean Journal of Food Science and Technology
• /
• v.10 no.4
• /
• pp.398-403
• /
• 1978

Squid was dried on the fluidized-bed in the drying chamber filled with solid particles which were also fluidized with hot-air, and effects of the fluidized particles, the squid's height from the grid and the drying temperature on the drying rate and quality of the squid were observed The mechanism of moisture transfer during the falling rate period was also derived. 1. Sodium chloride was found to be the most suitable fluidized particles and at an air velocity of 3.8 m/sec, optimal fluidization state of this particle was obtained. 2. Uniform profiles of temperature were obtained at a point 4 cm above the grid and the location of squid on the fluidized-bed observed to be suitable when it was 4 cm above the grid. 3. At an air velocity of 3.8 m/sec and when the location height of the squid on the fluidized-bed was 4 cm, the optimal temperature for the drying time which is required to reduce the moisture from 80.8% to 18-22% was 8.5 hours. 4. Drying data followed the empirical equation of unsteady state diffusion $log\;(\frac{W-We}{Wc-We})=-m{\theta}$ in the region of the moisture contents measured and the drying constant (m) was calculated as $0.32hr^{-1}$. These results suggested that the migration of moisture during the falling rate period is due to a diffusion type mechanism. 5. The short constant rate period was observed in the early stage and thereafter, drying was controlled by the falling rate period, and the time ratio of the fluidized bed drying to the through circulation drying for reducing the squid's moisture contents to the same level at the same drying temperature was 1 : 1.4 6. Comparisons of fluidized-bed dried squid and sun dried squid in sale showed that there was no significant change in qualities such as external appearance and hydrogen ion concentration of dry product.

• Korean Journal of Food Science and Technology
• /
• v.34 no.5
• /
• pp.780-786
• /
• 2002

Optimum condition of the drying process and the changes in aroma components during dehydration were determined for Sarcodon aspratus. The drying curve of mushrooms consisted of short constant rate period followed by long falling rate period. The drying rate increased with increasing drying temperature and air velocity. Results showed that mushrooms dried at $50^{\circ}C$ and air velocity of 1.5 m/sec had the greatest peak area of aroma compound. The aromatic components of the dried mushrooms were 1-octen-3-one, 1-octen-3-ol, 3-octanone, 1-octanol, 2-octen-1-ol, 3-octanol, 3-octanone, 1-octanol, 2-octen-1-ol, and 3-octanol. Peak areas of mushroom alcohol and aromatic compounds of mushrooms including 1-octen-3-ol, 1-octanol, 2-octen-1-ol, 3-octanol decreased significantly, whereas those of 1-octen-3-one and 3-octane increased during the drying period. New unfavorable compounds including butyric acid, propanoic acid, and 3-methyl thiopropanol were formed during the drying period.

• Food Science and Biotechnology
• /
• v.16 no.5
• /
• pp.771-777
• /
• 2007

Sliced and whole root of rehmannia were dehydrated in a laboratory dryer at 40, 60, 80, and $100^{\circ}C$ to evaluate the kinetic parameters for dehydration of rehmannia. The drying curves of both samples were characterized by a falling-rate drying period only. Sliced rehmannia dried 1.1 to 3.1 times faster than whole root of rehmannia depending on drying temperature. Equilibrium moisture content (EMC) of rehmannia samples at the drying temperature tested were 0.069-0.078 g water/g dry solid, which was coincided with the monolayer moisture content (0.06 and 0.07 g water/g dry solid) evaluated from desorption isotherms using GAB (Guggenheim-Anderson-de Boer) model. A logarithmic model for thin layer drying was applied to evaluate the drying time to reach EMC ($t_{EMC}$) and drying constant (k). The effect of temperature on $1/t_{EMC}$ and k was described by the Arrhenius model with activation energy values of 32.56 and 47.14 kJ/mol determined using the former parameter, and 34.27 and 38.26 kJ/mol determined using the latter parameter for sliced and whole root of rehmannia, respectively.

• Journal of Biosystems Engineering
• /
• v.33 no.5
• /
• pp.296-302
• /
• 2008

The effective moisture diffusivity and its dependence on drying temperature during drying of rapeseed were experimentally investigated. The data were recorded from thin layer drying experiments at nine different combinations of drying air temperatures of 40, 50, and $60^{\circ}C$ and the relative humidities of 30, 45, and 60%. The moisture diffusion equation was analyzed using stepwise multiple regression analysis. Effective moisture diffusivities were calculated based on the moisture diffusion equation for a spherical shape using Fick's second law. The effective diffusivities during the drying of rapeseed were $l.72{\times}10^{-11}$, $2.41{\times}10^{-11}$ and $3.31{\times}10^{-11}\;m^2{\cdot}s^{-1}$ at 40, 50 and $60^{\circ}C$, respectively. The activation energy for moisture diffusion during drying was $28.47\;kJ{\cdot}mol^{-1}$. The dependence of moisture diffusivity on temperature was described by an Arrhenius-type equation. Drying occurred in the falling rate period and the internal moisture diffusion phenomenon is the governing physical mechanism of the moisture movement in the particles.

• Resources Recycling
• /
• v.6 no.1
• /
• pp.40-46
• /
• 1997

Sludgc d~sposal has been a major challenge in the wastewater treatment. Drying is operation which is separated fromsewage sludge to solid and liquid by heating. Drying needs to pretreatment process for effective "thation, incinerationand dispaal The objective of this work was to the drying dewatered sewage sludge by microwave heating, and tocompare the experimental rcsults with thcorctical rcsults. Microwave drylng is fast and has a high efficiency. In thepresent \ark, an unsteady state analysis of one dunensional drying, with microwave heating, is carried out. In drying ratecurve, moisture movement at falling rate period occured by dfision. A good agreement was abtamed between the modcland the experimental results using the slab sample of 0.2cm thickness. 0.2cm thickness.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.16 no.3
• /
• pp.181-189
• /
• 1983

A study on the qualify changes of fish meat during drying and storage has been carried out with filefish meat. Filefish meat was dried in a forced air dryer at 40 and $55\%$ for 20 hours with an air velocity of 0.4 m/sec under different conditions of relative air humidities in the range of 10 to $50\%$. The dried fish meat was stored at $30^{\circ}C$ in chambers with constant relative humidities controlled by the use of conditioned air stream passing through the saturated salt solutions. The qualify of filefish meat was evaluated with the brown color densities developed by lipid oxidation and Maillard reaction. Changes of viable cell count during drying and storage were also discussed. The predominant reaction for the brown color developed during the study period was the lipid oxidation. The lipid oxidation rate during drying at constant temperature was appreciably affected by water activities at the drying surfaces of filefish meat during the falling drying rate period. The lipid oxidation rate was the slowest under the condition of the relative air humidity of around $30\%$. In samples stored at water activity of 0.33, the lipid oxidation rate was retarded remarkably in comparison with the samples with lower or higher water activities. The addition of $1\%$ table salt, $1.5\%$ D-sorbitol and $6\%$ sucrose slightly lowered the water activity with the slowest lipid oxidation rate. Such additives resulted the increase of the water soluble brown color densities, which seemed due to the increase of mobility of the water soluble substances by the result of the increase of equilibrium water content. Microflora of the samples immediately after drying consisted of ca. $30\%$ of coccus types, ca. $65\%$ of rod types and ca. $5\%$ of molds and yeasts. During the storage of the samples with a water activity of 0.76, the ratio of the coccus types to the total microflora was increased remarkably while that of the Gram negative non-spore rod types was decreased. The ratios of the Gram positive rod types, molds and yeasts during the storage were nearly constant.

• Korean Journal of Food Science and Technology
• /
• v.11 no.4
• /
• pp.264-272
• /
• 1979

The flat-plate and tubular soar collectors were designed and constructed for drying the rough rice, and the performance of the collectors and drying effect were investigated when rough rice was packed in grain bin connected to collectors. Average-monthly radiation on a horizontal surface based on bright sunshine in Daejeon area during 1978 was the highest as $16,814\;KJ/m^2{\cdot}day$ in May and the lowest as $4,254\;KJ/m^2{\cdot}day$ in December, and significane was not recognized between the calculated and recorded values. The thermal effciency of collectors were increased as radiation increased during drying period and the average thermal effciency of flat-plate and tubular collectors in 11 to 12 o'clock a.m were 28.12 and 16.75%, respectively. The average inlet temperature of grain bin at 12 o'clock was shown as 20.02 at control 40.5 at grain bin connected to tubular collector and $55.1^{\circ}C$ at grain bin connected to flat-plate collector. In 25 cm rough rice depth in grain bin, tim taken for drying from initial moisture content at 27.4 to decrease upto 17.0% (14.5 % on wet basis) were 32 in control, 18 in grain bin connected to tubular collector and 11 hrs to flat-plate collector, and grain depth influenced drying rate remarkably. In the view point of drying characteristics, drying pattern showed initially falling-rate to constant-rate period finally.