• KCI Concrete Journal
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• 제14권1호
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• pp.15-22
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• 2002

Stresses that develop due to differential shrinkage between polymer modified cement mortar (PM) and Portland cement concrete (PCC) in a repaired concrete beam at early ages were investigated. Interface delamination or debonding of the newly cast repair material from the base is often observed in the field when the drying shrinkage of the repair material is relatively large. This study presents results of both experimental and analytical works. In the experimental part of the study, development of the material properties such as compressive strength, elastic modulus, interface bond strength, creep constant, and drying shrinkage was investigated by testing cylinders and beams for a three-week period in a constant-temperature chamber. Development of shrinkage-induced strains in a PM-PCC composite beam was determined. In the analytical part of the study, two analytical solutions were used to compare the experimental results with the analytically predicted values. One analysis method was of an exact type but could not consider the effect of creep. The other analysis method was rather approximate in nature but the creep effect was included. Comparison between the analytical and the experimental results showed that both analytical procedures resulted in stresses that were in fair agreement with the experimentally determined values. It may be important to consider the creep effect to estimate shrinkage-induced stresses at early ages.

• Journal of Biosystems Engineering
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• 제15권3호
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• pp.230-243
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• 1990

This study was conducted to investigate the possibility of application of an infrared drying to drying process for red pepper. The performance of seramic heaters and the variation of temperature and moisture content of red pepper were analyzed during an infrared drying of red peppers. Also, the quality of dried red pepper was analyzed. The following results were obtained from this study. 1. The surface temperature of infrared heaters and the rising time required for steady state were mainly affected by electrical power consumed. 2. The heat energy required for heating red pepper was proposed to be calculated by the equation in terms of enthalpy of air and net heat flux by infrared heater in a drying chamber. The statistical model for net heat flux was developed. 3. The performance of the infrared heater used for heating red pepper was much affected by the distance of radiation, and the difference of temperatures appeared between the radiated surface and the inside of red pepper. 4. Electrical capacity of the infrared heater had a significant effect on the heating of red pepper. However, the effect of shape of heater on heating was not significant. 5. The variation of temperature of red pepper largely appeared in the range of 30 to 60% (db) in moisture content. The temperature of red pepper was almost constant at low moisture content. 6. The temperature of red pepper and heating time had significant effects on the quality for radiant heating. 7. When the electrical capacity of infrared heater and the distance of radiation are carefully designed in a dryer with the insulated drying chamber, infrared drying might be very effective in red pepper drying.

• 한국식품영양과학회지
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• 제20권5호
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• pp.503-508
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• 1991

영암어란의 제조방버은 건조기간이 긴 자연건조법으로 제조조건에 따라서 품질이 다르고 저장중 산화, 변색 및 단백질의 열화가 일어나 품질이 저하하였다. 본연구는 좋은 품질의 영암어란을 제조하기 위한 조건들의 확립을 위하여 품속에 따른 구성아미노산 함량과 산가, 과산화물가, TBA가의 변화로 최적풍속을 찾고 특성곡선을 구하였다. 엄장농도 5%, 바르는 참기름량은 3.0g/day에서 양호한 품질을 유지하기 위한 최적풍속으로 60% RH와 $20^{\circ}C$에서 2m/sec로 확정하였다. 영암어란의 제조에서 전통건조 방법의 건조기간은 20일이었으나 본 실험의 2m/sec 풍속에서 7일로 단축되었으며 이때의 건조특성곡선은 항율건조기가 없었고 감율건조기만 있었다.

• 한국환경과학회지
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• 제30권2호
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• pp.135-143
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• 2021

This study executed evaluation of drying characteristics based on the polymer injection rate (8%, 10% and 12%) and the drying method[NIF(near-infrared ray). According to this study analyzed VS, VS/TS, and calorific value compared with 'the auxiliary fuel standard of the thermoelectric power plant and the combined heat & power plant'. The results are as follows. In the case of NIR, the VS was slightly changed at the early stage of the material preheating period and the constant drying rate period with low moisture evaporation. But VS reduction was shown higher as moisture was dried. In the case of non-digested sludge with high VS content, the VS reduction rate by drying was shown lower than that of digested sludge. As the flocculant injection rate increased, the VS loss due th drying was found to be small. Also, the higher the flocculant injection rate was the longer the drying time. Especially, in the case of the NIR drying equipment, as the moisture content of sewage sludge decreased(moisture content 20~40%), the loss of net VS also showed a tendency to increase sharply. It is shown that the high calorific value according to the drying time of the non-digested sludge was changed from 590 kcaℓ/kg to 3,005 kcaℓ/kg and from 539 kcaℓ/kg to 2,796 kcaℓ/kg.

• Design & Manufacturing
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• 제15권4호
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• pp.32-36
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• 2021

In this study, the cause of the decrease in transmittance of the outer lens among the causes of the decrease in the amount of light in the automobile headlamp was identified, and the improvement method was selected to determine the effect. The causes of defects that lower the transmittance of the outer lens are divided into a moisture problem and a haze problem. The moisture problem is caused by the temperature difference between the inside and the outside of the head lamp, and the haze problem occurs when the heat inside the head lamp evaporates the haze component contained in the plastic material and attaches it to the outer lens. In order to improve the haze problem that occurs in plastic raw materials, the structures of the bulb light source type headlamp and the LED chip light source type headlamp were analyzed. Among them, the housing material of the LED chip light source type headlamp, which is structurally prone to haze gas, was selected as the test target. In the mass-production injection process of the housing, the drying process was selected as a method to minimize haze gas without adding a separate production process. After extracting a sample every drying time at a constant drying temperature, the sample was put into a haze tester and the residual amount of haze gas was measured. As a result, it was confirmed that the residual amount of Haze gas in the material decreased as the drying time increased.

• 한국식품과학회지
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• 제21권3호
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• pp.425-429
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• 1989

고추의 건조 중 중요한 품질요소인 carotenoid 파괴 및 비효소적 갈변의 kinetics를 건조 중 품질측정을 이용한 dynamic test에 의하여 평균 수분함량과 온도의 함수관계를 결정하였다. 1차반응으로 가정된 carotenoid 파괴 속도상수는 고온 고수분에서 높았으며 수분의존성에 있어서 건조중간의 어떤 수분함량에서 최소치를 보여주고 있었다. 온도의존성에 있어서 활성화 에너지는 7.7-27.4kcal/mol로 나타났고 수분함량이 높을수록 높았다. 0차반응으로 분석된 비호소적 갈변은 온도와 수분함량이 높을수록 쉽게 일어났으며 활성화에너지는 7.5-20.2kcal/mol로서 수분함량이 높을수록 높았다.

• 한국수산과학회지
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• 제21권1호
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• pp.16-20
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• 1988

다시마의 건조와 수축특성을 알기위한 기초자료를 얻고자 건조중인 다시마의 건조 및 수축특성에 미치는 채취부위, 공기의 온도, 상대습도 및 풍속의 영향에 관하여 실험한 결과를 요약하면 다음과 같다. 1) 다시마의 열풍건조과정은 항률건조 기간이 없이 바로 감률건조기가 나타났으며 이것은 다시 감률건조 1단계 및 2단계로 구분되었다. 2) 두께가 얇은 선단부가 기부보다 수축이 더 많이 되었으며 공기의 온도 $50^{\circ}C$, 상대습도 $30\%$, 유속 0.4m/s의 일정한 건조 조건하에서 다시마의 선단부, 중간부 및 기부를 120분까지 건조하였을 경우 수축율은 각각 $57.5\%,\;54.0\%,\;42.7\%$이었다. 3) 상대습도가 낮은것은 높은것에 비해 건조속도 및 수축속도는 빨랐으나 함수률 $20\%$까지 건조하였을 경우 수축율은 오히려 상대습도가 높은것이 증가하였다.

• 한국농공학회지
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• 제17권1호
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• pp.3677-3684
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• 1975

A newly devised dryer with heated air for the farm products, especially suited for high water content materials such as red pepper, Beer ground, each Vegetables, and Low water content materials such as Rough rice was tested for its thermal efficiency and drying mechanism, and the optimum conditions for each sample were established. In order to improve the present rural situation of drying farm products which entirely dependent upon natural solar radiation, a study upon an economic multi-parpose dryer was conducted. A series of drying tests were run first with red pepper which is one of the important cash crop in Korean farm. And successive series of tests were also run with such proaucts as garlic, sweet potatoes, green onion, radish, Beer ground and Rough rice. The results from the above experiment in drying system with heat dryer can be summarized as follows. 1. Drying duration could be shortened by the tempering effect in high water content crop such as red pepper and beer ground. 2. The color changes occured in around 20% water content in red pepper. The degree of color change was heavily affected by high temperature and short drying duration. 3. The drying condition of red pepper was most favourable at the temperature of 85$^{\circ}C$ in early stage and 80$^{\circ}C$ in middle stage and 75$^{\circ}C$ at the final stage, and with the air rate of 0.81㎥/sec and with sample amount of 200kg. 4. The drying condition of Rough rice(I.R.667) was most favourable at the templature of 40$^{\circ}C$ in early stage and 35$^{\circ}C$ in middle stage and final stage and with the air rate of 0.2㎥/sec and with sample amount of 75kg. 5. In order to prevent the color change of red pepper and to assure high efficiency in drying mechanism, it was necessary to lower the temperature as the time passes in drying process. 6. For vege tables, the drying rate were short in early stage and there was also tempering effect. However, for garlics, Constant drying rates through the early and final stages were observed and there were no tempering effects. 7. The drying condition or capability were as follows; Sample drying temp($^{\circ}C$) amount of material(kg) drying time(hr) Red pepper 85 200 9 Garlic 85 150 7 Sweet potato 85 200 6 Green Onion 85 200 4 Carrot 85 200 4 Radish 90 250 4 Rough rice(I.R.667) 35 75 4 Beer ground 90 320 3 Considering the above result of experiments, if this kind of dryers were distributed Korean farm and the optimun process were practiced in rural area, it would certainly help them improving the qualites of their product preventing their undue losses, and thus assuring an increase of Korean farm income and promotion of their living standards.

• 한국농공학회논문집
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• 제54권1호
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• pp.83-91
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• 2012

In this study, the compressive strength characteristics of lime-cement-soil mixtures, composed of lime, soil, and a small amount of cement, were investigated by performing the unconfined compression tests, the freezing and thawing tests, the wetting and drying tests and the permeability tests. The specimens were made by mixing soils with cement and lime. The cement contents were 0, 6, 8 and 10 %, and the lime contents were 2, 4, 5, 10, 15 and 20 % in weight. Each specimen was cured at constant temperature in a humidity room for 3, 7 and 28 days. The compressive strength characteristics of the lime-cement-soil mixtures were then investigated using the unconfined compression tests, freezing and thawing tests and the wetting and drying tests. Based on the test results, a discussion was made on the applicability of the lime-cement-soil mixtures as a construction material.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.236-241
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• 2009

After analyzing the characteristics of the cooling dryer, the mixed cooling dryer was developed by adding the desiccant dryer which supplement the cooling dryer's demerits. Also, the hybrid desiccant cooling dryer was developed to use effectively the exhaust heat energy of the cooling dryer. It could make a more that 20 percent reduction in energy compared with the mixed desiccant cooling dryer. It has become essential to supply this equipment and search the suitable drying product.