• Journal of Power System Engineering
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• v.21 no.4
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• pp.62-69
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• 2017

Because the moist foods like anchovy were appeared lower quality by hot air that occurred the lipid oxidation, the drying system by using the cold air has been used widely. This study has been carried out on the performance improvement according to arrangement angle of baffle and location of air duct in the cold air dryer. The main parameters in this study are the arrangement angles which are without, $0^{\circ}$, $10^{\circ}$, $20^{\circ}$, $30^{\circ}$ and $40^{\circ}$, and the locations of air duct are without, front, center and back. For this study we have conducted the numerical analysis method using fluent in order to obtain the optimal condition of the drying performance. As the arrangement angle of baffle is increased, the relative humidity is proportionally decreased, the value at $40^{\circ}$ is 42.2% that indicate the reduction of about 4% than without it. After the air duct was installed, the decreased relative humidity is showed within 1%, therefore, the effect of air duct for improving the dry capacity is more large than the arrangement angle of baffle. Finally, we have obtained the optimal conditions that the arrangement angle is $40^{\circ}$ with the air duct for a cold air dryer.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.242-247
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• 2009

The present study has been conducted to reduce the cold air drying rate. According to the cold air drying method, the quality-excellent product could be made and there would be little change of color, taste and smell. As compared with the hot air drying, the cold air drying equipment has the superior dehumidification in a constant drying zone. However, in a falling drying zone that equipment is not energy-efficient because the drying period could be longer by the dehumidificated.

• Journal of Korean Society for Atmospheric Environment
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• v.25 no.6
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• pp.523-538
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• 2009

Recently, there has been a keen demand for real-time automatic monitoring of VOCs not only in Korea but other developed countries. We carried out this study to evaluate and to optimize the performance of a continuous automatic monitoring system for hazardous VOCs (HVOCs) in the ambient atmosphere, using an on-line GC system. The online system normally consisted of a Nafion dryer prior to a cold trap of an automatic thermal desorption apparatus and a GC system equipped with two detectors, i.e. PID and ECD. Preliminary tests conducted to check out any contamination of the system revealed an evidence of significant artifact formation of benzene, and it was found that the Nafion dryer (even brand new one) is the source of the benzene artifact. Thus, all the subsequent experiments in this study was carried out inevitably by removing the Nafion dryer. The on-line GC method was investigated with a variety of QC/QA performance criteria such as repeatability, linearity, lower detection limits, and accuracy. In order to find out the best operating condition for the on-line GC system, three different types (in terms of adsorption strength) of cold trap combinations were tested, i.e. (i) Tenax-TA and Carbopack-B combination (weak and hydrophobic); (ii) Tenax-TA, Carbopack-X and Carboxen-1000 combination (strong and hydrophilic); and (iii) Tenax-TA and Carbopack-X combination (medium and hydrophobic/hydrophilic). The USEPA TO-17 manual method was selected as a reference method to evaluate the performance of the on-line method. A series of experiments revealed that the system performance was superior to others when a cold trap packed with hydrophilic adsorbents (Tenax-TA/Carbopack-X/Carboxen-1000 combination) was used and operated at $25^{\circ}C$. However, the system with a cold trap packed with a combination of Tenax-TA and Carbopack-X is more recommended for field applications since the carboxen-1000 adsorbent is too sensitive to water vapor, and hence the performance of the system might be very unstable to humid samples or during rainy days. Furthermore, the precision and accuracy criteria of the Tenax-TA/ Carbopack-X combination were generally compatible with the triple adsorbents cold trap. The continuous automatic monitoring method is, thus, considered very useful to real-time monitoring to understand the variations of VOCs concentrations in ambient air, as it adopts much simpler procedures in sampling, analysis, and data integration steps than manual monitoring methods. However, it should be noted that there is a high possibility of benzene artifacts formation through the Nafion dryer, which is often installed to remove water vapor in air samples before being adsorbed onto the cold trap. Therefore, if a Nafion dryer is used in any studies of monitoring VOCs, the benzene contamination should be carefully examined before carrying out obtaining the data.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.5
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• pp.547-552
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• 2011

Drying process, corresponding to a final process in the area of food engineering, requires a lot of heat energy. Thus, the energy efficiency is very important for dryers. Since the energy efficiency of heat pump dryers is much higher compared to that of electric dryers or other types of dryers, most of large-capacity dryers are adopting heat pump. In this study, shapes, positions and number of air-circulating fans, guide vanes, air inlet, outlet and top separator were varied for optimization of the flow of a large-capacity heat pump dryer. In addition, fans were modelled with performance curves and porous media were assumed for foods and heat exchangers. The simulation results were applied to the 12-ton dryer and the velocity distributions were experimentally examined. Finally, uniform drying in time was successfully accomplished through frozen pepper experiment.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.6
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• pp.1007-1013
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• 2003

As environmental restriction kas continuously become more strict, machining technology has emphasized on development of environment-friendly technology. In cutting technology, it has been well recognized that cutting fluids might have undesirable effects on workers health and working environment. In this study, compressed cold air was used as a replacement for conventional cutting fluids. The cooling effect on cutting tool was analyzed using the finite element method and the computational fluid dynamics. This study focused on the temperature simulation of cutting tool by real flow analysis of cold air. The maximum flow rate and the minimum temperature of compressed cold air are 300ι/min and -30$^{\circ}C$ respectively. To compare the simulation and experimental results, inner temperature of the cutting tool was measured with the thermocouple embedded in the insert. The results show that the analysis of cutting temperature using FEM and CFD is resonable, and the replacement of cutting fluid with cold air is available.

• Journal of Korean Society for Atmospheric Environment
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• v.27 no.6
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• pp.734-745
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• 2011

In this article, we reviewed the monitoring status of hazardous VOC in ambinet air in Korea and some developed countries such as USA, Japan, and UK. In many countries, two types of VOC monitoring stations are being operated, i.e., for hazardous VOC and photochemical VOC. Each country has different target VOC but all includes benzene. Korea, Japan, and UK have a national ambient air quality standard for benzene, but no national standard has been established in the USA. For sampling of the hazardous VOC, the adsorbent method is adopted in Korea and UK, while the canister method is used in the USA. Both of adsorbent and canister methods are used in Japan. USA and UK have only non-automatic method to measure the hazardous VOC, and the individual samples are being sent to their national laboratories for integrated analysis. On the other hand, Korea and Japan have automatic and nonautomatic methods to measure the hazardous VOC. Local governments or regional environmental agencies in Korea and Japan have the authorization for the sampling and analysis of VOC. According to a field study to evaluate the performance of automatic VOC monitoring system, controlling the moisture in the air sample was identified as the most important problem. However, careful attention must be given to using a moisture removing device such as Nafyon dryer, because of unexpected artifacts formation. In order to have reliable data, it is highly recommended not only to use internal standards, but to use appropriate hydrophobic adsorbents as a cold trap in any automatic on-line VOC monitoring system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.5
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• pp.208-215
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• 2016

This study was conducted to improve the performance of low-temperature vacuum dryer by applying desiccant to cold trap. Performance evaluation was carried out using several desiccants. The amounts of absorption and diffusivity were measured based on analytic model. Results of desiccant performance evaluation revealed that silica-gel had the most excellent performance for conditions of low-temperature vacuum drying process. Silica-gel was applied to cold trap for evaluating the drying performance. The experiment results showed that the drying time was extended as the thickness of sample was increased due to increased heat and mass transfer resistance of drying sample. In addition, as heating plate temperature was increased, drying time was decreased due to increased evaporation pressure of drying sample. Furthermore, drying time with desiccant was decreased approximately 20% than that without desiccant.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.10a
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• pp.24-29
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• 2003

Deep sea water has cold temperature, abundant nutrients and minerals, and good water quality that is pathogen-free and stable. Compared with surface water, deep sea water contains more nutrition salt, such as nitrogen and phosphor. Moreover, if has the good balance of minerals. Because of the ability of the spray drying process to produce a free-flowing power considering of spherical particles with a well-defined size distribution and the rapid drying times for heat-sensitive material, spray drying is attractive for a wide range of applications spray drying is a unique unit operation in which powders are produced from a liquid feed in a single processing step. Key component of the process are atomizer, spray chamber. Design of spray chamber should be based on the atomizer type, the production rate, and the particle size required. Because of the complex processes taking place during spray drying, traditional design method are based on pilot-plant tests and empirical scale-up rules. Modern technique such as CFD have a role to play in design and troubleshooting.

• Korean Journal of Medicinal Crop Science
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• v.25 no.2
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• pp.89-94
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• 2017

Background: The purpose of improving the quality of oriental medicinal herbs is to contribute to the improvement of the income of farm. The present study investigated the effect of reasonable drying methods, different storage conditions and packageing materials on quality and stability of Scutellaria baicalensis Georgi and for developing GAP (good agricultural practice) guide book. Methods and Results: Three methods of drying Scutellaria baicalensis roots produced over two years were used to estimate loss rate owing to drying, storage, and packaging. The methods of drying were categorized into natural drying (36 - 60 h by sunshine), drying with heat dryer (2 - 10 h), or drying with gas bulk dryer (2 - 10 h). After cleaning, and initial drying for a few days under controlled temperature conditions, the second phase of drying was carried out at 35, 45 and $55^{\circ}C$. Changes in hunter color values and quality under the two studied storage treatments (at $20^{\circ}C$ indoors and at $4^{\circ}C$ in a refigerator) were evaluated. Storage period for 60, 120, and 180 days in three packaging materials, PE (polyethylene package), PP (polypropylene gunnysack), and WP (watertight packing paper) were studied. Conclusions: Initial cleaning, reasonable gas drying and hot air drying, and drying in an oven at 35 and $45^{\circ}C$ after cutting the roots resulted in the lowest loss rates in S. Baicalensis root. Hunter color valuse indicated that stroage of dry roots at room temperature was better than PP packaging, and that cold stroage was better than PE packaging for long-term stability.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.6
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• pp.427-446
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• 2008

A review on the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2006 has been accomplished. Focus has been put on current status of research in the aspect of heating, cooling, ventilation, sanitation and building environments. The conclusions are as follows. (1) The research trends of fluid engineering have been surveyed as groups of general fluid flow, fluid machinery and piping, etc. New research topics include micro heat exchanger and siphon cooling device using nano-fluid. Traditional CFD and flow visualization methods were still popular and widely used in research and development. Studies about diffusers and compressors were performed in fluid machinery. Characteristics of flow and heat transfer and piping optimization were studied in piping systems. (2) The papers on heat transfer have been categorized into heat transfer characteristics, heat exchangers, heat pipes, and two-phase heat transfer. The topics on heat transfer characteristics in general include thermal transport in a cryo-chamber, a LCD panel, a dryer, and heat generating electronics. Heat exchangers investigated include pin-tube type, plate type, ventilation air-to-air type, and heat transfer enhancing tubes. The research on a reversible loop heat pipe, the influence of NCG charging mass on heat transport capacity, and the chilling start-up characteristics in a heat pipe were reported. In two-phase heat transfer area, the studies on frost growth, ice slurry formation and liquid spray cooling were presented. The studies on the boiling of R-290 and the application of carbon nanotubes to enhance boiling were noticeable in this research area. (3) Many studies on refrigeration and air conditioning systems were presented on the practical issues of the performance and reliability enhancement. The air conditioning system with multi indoor units caught attention in several research works. The issues on the refrigerant charge and the control algorithm were treated. The systems with alternative refrigerants were also studied. Carbon dioxide, hydrocarbons and their mixtures were considered and the heat transfer correlations were proposed. (4) Due to high oil prices, energy consumption have been attentioned in mechanical building systems. Research works have been reviewed in this field by grouping into the research on heat and cold sources, air conditioning and cleaning research, ventilation and fire research including tunnel ventilation, and piping system research. The papers involve the promotion of efficient or effective use of energy, which helps to save energy and results in reduced environmental pollution and operating cost. (5) Studies on indoor air quality took a great portion in the field of building environments. Various other subjects such as indoor thermal comfort were also investigated through computer simulation, case study, and field experiment. Studies on energy include not only optimization study and economic analysis of building equipments but also usability of renewable energy in geothermal and solar systems.