• 동력기계공학회지
• /
• 제22권1호
• /
• pp.79-86
• /
• 2018

Many countries have conducted extensive studies for biomass co-firing to enhance the durability of reactor on high-temperature corrosion. However, due to the complicated mechanisms of biomass co-firing, there have been limitations in accurately determining the current state of corrosion and predicting the potential risk of corrosion of power plant. In order to solve this issue, this study introduced Lab-scale corrosion system to analyze the corrosion characteristics of the A213 T91 material under the biomass co-firing conditions. The corrosion status of the samples was characterized using SEM/EDS analysis and mass loss measurement according to various biomass co-firing conditions such as corrosion temperature, $SO_2$ concentration, and corrosion time. As a result, the corrosion severity of A213 T91 material was gradually increased with the increase of $SO_2$ concentration in the reactor. When $SO_2$ concentration was changed from 0 ppm to 500 ppm, both corrosion severity and oxide layer thickness were proportionally increased by 15% and 130%, respectively. The minimum corrosion was observed when the corrosion temperature was $450^{\circ}C$. As the temperature was increased up to $650^{\circ}C$, the faster corrosion behavior of A213 T91 was observed. A213 T91 was observed to be more severely corroded by the effect of chlorine, resulting in faster corrosion rate and thicker oxide layer. Interestingly, corrosion resistance of A213 T91 tended to gradually decrease rather than increases as the oxide layer was formed. The results of this study is expected to provide necessary research data on boiler corrosion in biomass co-firing power plants.

• Journal of Biosystems Engineering
• /
• 제32권4호
• /
• pp.247-255
• /
• 2007

During the winter season in Korea, the relative humidity of greenhouse at night often exceeds 90% because air temperature inside the greenhouse is usually controlled using a heater with all of windows closed to minimize heat loss, thereby requiring the use of a dehumidifier that can maintain optimum humidity levels of $70{\sim}80%$ to provide a good growth condition of crops. Also, such a high humid condition can cause the development of a pest, such as insects, fungi or diseases. However, the use of most conventional dehumidifiers for low temperature dehumidification is limited because their performance is degraded due to frost accumulation on the evaporator coil. This study was carried out to develop a refrigeratory-based dehumidifier suitable for low temperature dehumidification in greenhouse cultivation. The developed dehumidifier consists of a condenser and an evaporator installed separately so that relative and absolute humidity levels can be reduced when air passed through the condenser and evaporator, respectively. The prototype dehumidifier showed a dehumidification capacity of $5{\sim}7kg/h$ when air with a temperature of $15{\sim}25^{\circ}C$ and a relative humidity of $70{\sim}95%$ came into the dehumidifier. Under the condition that either temperature or relative humidity was fixed, the amount of condensed water was proportional to the levels of both temperature and relative humidity.

• 한국화재소방학회논문지
• /
• 제33권2호
• /
• pp.39-46
• /
• 2019

화재환경에서 열유속 측정을 위해 사용되는 판형 열유속계의 측정 오차 및 소형화를 통한 공간 해상도 개선에 관한 실험적 연구가 수행되었다. 주요 결과로서, Plate의 뒷면에 설치되는 단열재의 두께 및 밀도 변화에 따른 측정값 분석을 통해, 판형 열유속계의 측면으로의 열손실이 측정오차에 큰 영향을 줄 수 있음이 확인되었다. 또한 기존 10 cm 크기의 정사각형 형상을 기준으로 소형화를 통해 3 cm 크기의 판형 열유속계도 충분히 정확한 열유속 측정이 가능함을 확인하였다. 본 연구결과는 화재환경에서 보다 정확한 국소 위치의 열유속 측정을 위해 유용하게 활용될 것으로 기대된다.

• Tribology and Lubricants
• /
• 제35권2호
• /
• pp.99-105
• /
• 2019

This study presents an experimental investigation of the wear and oxidation of the bristles of a brush seal in a super-heated steam environment. We construct a model reflecting normal force and radial interference to predict the amount of wear. To monitor the volume loss of the bristle induced by the swirl phenomenon of the rotor, we measure the clearance between the rotor and the brush seal by using a non-contact 3-D device. We calculate the area by using the area-wise measurement method. Considering the obvious brush seal wear variables, we use two disks with different roughness($Ra=0.1{\mu}m$ and $100{\mu}m$) to determine the effect of roughness on wear. Considering an actual steam turbine, we utilize a steam generator and super-heater to generate a working fluid (0.95MPa, 523.15K) that has high kinetic energy. We observe the abrasion of the bristles in the hot steam environment through a scanning electron microscope image. This study also conducted energy dispersive X-ray (EDX) analysis for a qualitative evaluation of local chemistry. The results indicate that the wear and elimination of bristles occur on the disk with high roughness, and the weight increases due to oxidation. Furthermore these results, reveal that the bristle oxidation is accelerated more under super-heated steam conditions than under conditions without steam.

• 한국가금학회지
• /
• 제42권1호
• /
• pp.9-13
• /
• 2015

본 연구는 가열처리와 온도가 구운 계란의 품질에 미치는 영향을 구명하고자 수행하였다. 구운 계란은 80, 90, 100, 105 및 $110^{\circ}C$ 의 온도에서 시간을 달리하여 5, 6, 7 및 8시간 동안 상업용 가열기(OF-22, JEIO TECH, Korea)를 이용하여 제조하였다. 가열감량은 최종 $110^{\circ}C$에서 가열된 8시간 처리구가 최종 $105^{\circ}C$에서 가열된 처리구들에 비해 유의적으로 (p<0.05) 높게 나타났다. 난백의 pH는 가열시간이 가장 짧은 5시간 처리구가 다른 처리구에 비해 유의적으로(p<0.05) 높게 나타났다. 난황의 pH는 모든 처리구 사이에 유의적인 차이가 없는 것으로 나타났다. 가열온도와 가열시간에 따른 구운 계란의 경도와 응집성은 처리구간 유의적인 차이가 없는 것으로 나타났다. 최종 $110^{\circ}C$에서 가열된 8시간 처리구의 백색도 값은 최종 $105^{\circ}C$에서 가열된 처리구들에 비해 유의적으로(p<0.05) 낮고, 적색도와 황색도의 값은 유의적으로(p<0.05) 높게 나타났다. 난백 및 난황의 수분 함량은 가열시간 증가와 함께 감소하는 경향을 나타내었다. 이상의 결과를 종합해 볼 때 구운 계란의 제조를 위한 적합한 시간은 8시간이며, 최종 온도는 $105^{\circ}C$에서 5시간 이상 또는 $110^{\circ}C$에서 2시간 이상 가열하는 것이 적절한 것으로 사료된다.

• 한국수산과학회지
• /
• 제17권5호
• /
• pp.361-367
• /
• 1984

In previous paper(Lee et al., 1984), preparation formula and processing conditions of the fish meat (mackerel) paste using dielectric heating were described, that included the proper shape and size of product and the conditions of dielectric heating, hot air dehydration, and heating with electric heater to yield the minimum expansion and case hardening during heating and to controll the final rater activity of 0.86 to 0.83 accompanying with a complete reduction of viable cells and good texture. In present study, changes in VBN, pH, total plate count, water activity, texture, the loss of available lysine, color indexes, TBA value, and the content of TI were determined to assess the quality stability and shelf-life of the product during the storage for 35 days at $5^{\circ}C\;and\;25^{\circ}C$, respectively. And the effect of vacuum sealing and hot water treatment before storage on the storage stability of product was also mentioned. As the product was vacuum packed in K-flex film bag, heat treated in boiling water for 6 minutes, and stored, water activity was maintained 0.86 to 0.84 for 35 days regardless of storage temperature, and the increase of total plate count was negligible in case of $5^{\circ}C$ storage while tended to gain slightly after 25 days at $25^{\circ}C$ storage. Changes in VBN was also minimum with an increase of 1.5 mg/100g at $5^{\circ}C$ and 7.0mg/100g at $25^{\circ}C$, but in case of unpacked sample, it was 24.5mg/100g at $5^{\circ}C$ and 42.4 mg/100g at $25^{\circ}C$ even after 7 days. In textural property hardness tended to increase after 28 days and folding test score was down to A or B from AA grade. The loss of available lysine was $7.5\%\;at\;5^{\circ}C$ and $17.0\%\;at\;25^{\circ}C$ but brown color was not deeply developed as the color index score indicated. TBA value was not increased at $5^{\circ}C$ while it tended to increase rapidly after 30 days at $25^{\circ}C$. Changes in TI content was not obvious except that it showed a tendency of increase at the end of storage as well as in the change of lysine and TBA value. It is concluded from the results that the quality of the product, pasteurized and water activity controlled by dielectric heating, and vacuum packed in K-flex film would be stable for more than 35 days at $5^{\circ}C$ and at least 25 days even at room temperature.