• Journal of Biosystems Engineering
• /
• v.2 no.2
• /
• pp.37-45
• /
• 1977

Solar energy is a potential source of power that offers much promise being used for low-temperature applications like drying farm crops, space heating, and water heating for domestic uses. Already much of it are being used for those purpose in foreign countries. However, very little research has been done to determine the possibility of using the solar energy in Korea. This study was conducted to develop the general prediction equation of the total radiation on a horizontal surface in Daejeon area based on 5 years 91972, Jun.1-1976. Dec.31) meteorological data (bright sunshine hours, average total horizontal radiation), and to obtain experimentally the thermal efficiency of solar air and water collectors, which will be used as a basic data of designing flat-plate solar collector system.In addition to the thermal efficiency of the collectorsthe relationship among those factors affecting it such as weather condition, orientation factor, and tilted angle of collector was analyzed. The results of this study were as follows. 1. The general predicted equation of the total radiation on a horizontal surface in Daejeon area based on bright sunshine hours was developed as $H_{av} =(1.546\frac{n}{N}-0.582)H_o$. Predicting the total radiation on a horizontal surface by the above equation was thought to be possible because to values of 0.882 was smaller than any t values at above 0.05 level on the basis of two tailed test of the difference between the calculated and the recorded values. 2.It was observed that optimum tilt angle of the collector in the summer and the autumn drying season was 13 degrees and 51 degrees respectively, these values could be obtained by adding or substracting approximately 25 degrees from the latitude of this area $(36.3^{\circ}N)$ .The relationship between orientation factor and declination of sun at suitable tilt angle of 33 degrees $(s=0.9\O)$ was shown at Fig.4. 3.The thermal efficiency of solar wdter collector was shown 13.4-51. 6% on Aug. 15 (the minimum radiation recorded) and 43.8 ~537% Aug.20 (the maximum radiation recorded), and 13.8~ 46.6 and 44.3~ 49.7 were shown on each corresponding day. 4.The thermal efficiency of the collectors according to the weather condition was shown a big difference of about 10% between the day of the maximum radiation recorded and the minimum, but the differen of efficiency between the air and the water collector was at most 2 ~ 3%. 5. Even if the efficiency of the solar water collector was a little higher than the solar air collector, for drying farm products, the solar air collector was thought to be more effective because the air heated by collector could be directly used for drying them.

• Food Science and Preservation
• /
• v.22 no.5
• /
• pp.683-689
• /
• 2015

Response surface methodology (RSM) is a statistical procedure frequently used for optimization studies. The purpose of this study was to determine the optimal spray drying condition for manufacturing Sikhye powder using RSM. Independent variables included the additive contents of maltodextrin (MD), inlet temperature, and velocity of sample feed velocity. The dependent variables were water uptake (g), solubility (%) and particle size (${\mu}m$). Regression models describing the changes of water uptake (g), solubility (%) and particle size (${\mu}m$) with respect to the independent variables were statistically significant with coefficients of determination, $R^2$, greater than 0.9. The results indicated that the inlet temperature of the spray dryer was the most important independent variable that affected the water uptake (g), while the additive content of MD and the sample feed velocity had maximum effects on the solubility (%) and particle size (${\mu}m$) of the Sikhye powder, respectively. The optimum final product was expected to have the lowest possible water uptake (g) and particle size (${\mu}m$) but the highest possible solubility (%). In conclusion, the best spray drying conditions were as follows: additive MD content, 22%; inlet temperature, $140^{\circ}C$ ; and spray dryer sample feed velocity, 51 mL/min.

• Journal of the Korean Ceramic Society
• /
• v.16 no.2
• /
• pp.89-98
• /
• 1979

In order to prepare ferroxplana ZnY $(Ba_2Zn_2Fe_{12}O_{22})$, which would be useful for GHz-band communication, the optimum coprecipitation condition of 1 $BaCl_{2-1} Zn(NO_3)_2-6FeCl_3$ in $NaOH-Na_2CO_3$ solution was investigated by use of a new apparatus invented in our laboratory. By freeze-drying and calcining the coprecitated hydroxide-carbonate, the very reactive powder was obtained, from which the synthesis process of ZnY and the other related crystals were investigated by means of X-ray diffraction. In results, it was found that the reactive powder containing ZnY as the major component can be prepared by this method, which may be used in manufacturing the various magnetic cores for the microwave communication.

• Journal of the Korean Ceramic Society
• /
• v.17 no.3
• /
• pp.121-128
• /
• 1980

In order to obtain the fundamental data for the preparation of ferroxplana $Zn_2Y(Ba_2Zn_2Fe_{12}O_{22})$, which is useful for GHz-band communication, the optimum coprecipitation condition of $Zn(NO_3)_2-6FeCl_3$ in $NH_4OH$ solution and the formation process of the hexagonal ferrite were investigated. By the hot-petroleum-drying and calcining the coprecipitated hydroxide mixture $Zn(OH)_2 +Ba(OH)_2+ 6Fe(OH)_3$, the fine and uniform powder was obtained , whose phase composition and microstructure were studied by X.R.D. and electron microscope. In results, it was found that $Zn_2Y$, BaM and $Zn_2W$ were the representative phases in calcined specimens whose activation energies of crystal growth were about 3, 8, 2.5, $5.4{\times}10^4$ J/mole , respectively. The sintered specimens would be appreciated as useful magnetic cores for the high frequency communication.

• Proceedings of the Korean Society of Dyers and Finishers Conference
• /
• 2010.03a
• /
• pp.205-206
• /
• 2010

This Study executed the newly developed warp knitted fabrics for the end of living textile materials and investigated the dyeing behavior with the change of drying temperature. There were also analysis of yarn properties in the process of dyeing and finishing. Above all, we examined the influence of touch and softness according to processes. So we can expect the optimum yarn and condition for the better textile goods.

• International Journal of Industrial Entomology and Biomaterials
• /
• v.22 no.1
• /
• pp.5-10
• /
• 2011

The effect of sample handling condition on the rheological measurement of regenerated silk fibroin formic acid solution using parallel plate geometry was investigated. In case of loading method, the loading by pouring sample solution resulted in the best reproducibility of rheological measurement. Loading with spoon showed a high variance of viscosity value at low shear rate region ($0.01{\sim}1sec^{-1}$) while loading with syringe exhibited a low reproducibility of viscosity at high shear region ($1{\sim}100sec^{-1}$) with a disappearance of shear thinning phenomenon. It was revealed that the sample loading with small extra amount lead to the most reproducible result. The sample loading with the exact amount for the measuring plate resulted in a lack of reproducibility of high shear viscosity, while the loading with large extra volume produced a limited consistency of low shear viscosity. It was turned out that 3 min. of waiting time before measurement was the optimum condition for reliable result. When the waiting time was less than 1 min., the low shear viscosity was obtained with a lack of consistency. On the other hand, the sample solution started drying when the waiting time increased up to 5 min.

• Food Science and Preservation
• /
• v.24 no.4
• /
• pp.505-509
• /
• 2017

Water vapor adsorption kinetics of vacuum-dried jujube powder were investigated in temperature and relative humidity ranges of 10 to $40^{\circ}C$ and 32 to 75%, respectively. Water vapor was initially adsorbed rapidly and then reached equilibrium condition slowly. Reaction rate constant for water vapor adsorption of vacuum-dried jujube powder increased with an increase in temperature. The temperature dependency of water activity followed the Clausius-Clapeyron equation. The net isosteric heat of sorption increased with an increase in water activity. Good straight lines were obtained with plotting of $1/(m-m_0)$ vs. 1/t. It was found that water vapor adsorption kinetics of vacuum-dried jujube powder was accurately described by a simple empirical model, and temperature dependency of the reaction rate constant followed the Arrhenius-type equation. The activation energy ranged from 50.90 to 56.00 kJ/mol depending on relative humidity. Arrhenius kinetic parameters ($E_a$ and $k_0$) for water vapor adsorption by vacuum-dried jujube powder showed an effect between the parameters with the isokinetic temperature of 302.51 K. The information on water vapor adsorption kinetics of vacuum-dried jujube powder can be used to establish the optimum condition for storage and processing of jujube.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.11
• /
• pp.5628-5636
• /
• 2012

Effective drying method of sewage sludge is researched in this study. To dry the sludge, chain crusher flash dryer was adopted to remove moisture content in the cell which is mostly responsible for the sludge moisture content. And Pilot plant experiment was conducted in real life sewage treatment plant to study effect and characteristics of operating conditions. Operating variables include sludge feeding rate, rotational speed of chain, process temperature and feed moisture content. As rotational speed of chain increased, product yield of sludge increased, and the performance of the testing system increased. And, as process temperature increased, the sludge drying efficiency increased. It is found that optimum feed moisture content is at 60% which shows the maximum sludge product yield and about 10 moisture content(%) of sludge product. Sludge feed rate showed optimal value, and when the sludge feed rate is exceeded, sludge product yield did not increased but the amount of residue increased. Pilot plant experiment results are as follow. The optimal condition for the rotational speed of chain 1600rpm(max. speed), final sludge discharge temperature $80^{\circ}C$, feed moisture content 60%, and feed rate 60kg/h. When the plant was operated at the optimal conditions, the final product showed fairly good results such as sludge product yield 85.5%, moisture content 11.0% and sludge drying efficiency 81.7%.

• Resources Recycling
• /
• v.30 no.1
• /
• pp.60-65
• /
• 2021

The recycling of titanium turning scraps requires the removal of cutting oil and other contaminants remaining on the surface. In this study, an experiment was conducted in which titanium scraps were cleaned by a combination of ultrasonic immersion-steam cleaning and subsequent drying at high temperature. To determine the removal mechanism of cutting oil, the contact angle between titanium surface and cutting oil was measured. The result confirmed the optimum condition of the immersion solution of the titanium turning scraps. In the case of immersion cleaning of Na4P2O7 aqueous solution, the degree of carbon removed in the cutting oil was the highest at 50℃, and it was confirmed that the carbon content obtained from the combination of steam cleaning and ultrasonic immersion-steam cleaning was lower than that from steam cleaning after ultrasonic immersion. The oxidation and decomposition behaviors of cutting oil were investigated using Thermogravimetric analysis (TGA) and the result was applied in the high temperature drying process. From the results of the high temperature drying tests, it was concluded that 200℃ is the optimal drying temperature.

• Food Engineering Progress
• /
• v.14 no.2
• /
• pp.112-117
• /
• 2010

Black ginger, obtained from steaming and drying process, provides the various functional properties. This study was performed to investigate the optimum processing conditions for black ginger with high content of biologically active substance such as anti-oxidations. Optimum processing conditions such as temperature and time for black ginger was determined by response surface methodology (RSM) with manufacturing process and functionality. The optimum steaming condition was determined 6 hours at 93.2$^{\circ}C$, and 82.7 mg/L DPPH scavenging activities was obtained at this condition. The black ginger drink was made with black ginger extracts, Japanese apricot, and honey. Interaction effects of these ingredients were investigated by modified distance based on design and analyzed by linear, nonlinear regression model, and RSM. The optimization of mixture ratio was made by statistical modeling using DPPH scavenging activities and sensory properties which are the important target constraints in drink. Total flavonoids showed a linear canonical form, while preference and antiradical activity showed a nonlinear canonical form indicating the higher interaction among mixtures. The response trace plot revealed that antiradical activity, sensory properties and total flavonoids were quite sensitive to the drink blending. The optimum formulation of the drink was set at 14.2% of black ginger extracts, 5% of Japanese apricot, and 10.8% honey.