• 대한기계학회논문집B
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• 제26권3호
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• pp.491-497
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• 2002

In the present study, a new wood boiler was developed through the performance test. The efficiency of the boiler was obtained up to about 63.7%, which is 67% higher than that of conventional wood boiler, about 38.2%. The structure of the new boiler is more complicated than the conventional boiler. The passage of combustion gas is sufficiently long to exchange heat well with heating water. Therefore, the obtained efficiency is so high, and the temperature of exhaust gas was lower than 200$^{\circ}C$, which is as low as that of light oil boiler. The composition of exhaust gas was measured, and the CO gas concentration was obtained more than 3000 ppm. So, it seems that more study is needed to lower the concentration of CO gas.

• 한국응용과학기술학회지
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• 제33권1호
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• pp.58-66
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• 2016

저온진공건조 조건에 따른 곶감의 건조특성 및 품질적 변화를 분석하였다. 곶감의 건조 특성은 전형적인 항율건조기간과 감율건조기간이 존재함을 확인 할 수 있었다. 진공압력이 높을수록 가열온도가 높을수록 곶감의 당도, 당 함량, 경도 값은 높게 나타났으며 이에 비해 명도 값은 낮게 나타남을 알 수 있었다. 기존 천일 및 열풍건조를 대처할 수 있는 진공건조의 최적 조건은 진공압력이 40~50kPa abs., 가열온도 $30^{\circ}C$, 건조시간은 3~4일 이었다.

• Journal of the Korean Wood Science and Technology
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• 제14권2호
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• pp.36-42
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• 1986

Both the control and heated specimen of oak, hornbean, alder, poplar, red pine and pitch pine among domestic commercial species and taun imported were used for radial and tangential shrinkage and movement that occurred on changing the relative humidity of the atmosphere from 90 percent to 60 percent at $25^{\circ}C$. The results of this study were as follows. 1. The radial and tangential shrinkage of the control and heated hornbean and oak wood, except alder, of high specific gravity showed greater than species with low specific gravity. The ratio of tangential to radial shrinkage was 1.46 for taun to 2.70 for alder. Green volume specific gravity of the heated and soaked specimen of all species except poplar decreased 1.5 to 3.1 percent. Shrinkage of the heated specimen increased more than that of the control specimen, and antishrink efficiency of all timbers except alder had negative value. Shrinkage from green to air dry of treated specimens increased more than case of total shrinkage, and radial shrinkage of those specimen increased greater than tangential shrinkage. 3. The movement of the heating specimen for 120 hours decreased than those of the control and the heating specimen for 240 hours. The movement of heating oak, poplar, red pine and pitch pine (or 240 hours increased rather than those of the control specimen.

• 설비공학논문집
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• 제25권3호
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• pp.168-172
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• 2013

A preliminary performance test of a 30RT 2-stage screw heat pump was carried out in order to develop a high performance large-scale unutilized energy source heat pump system, which will be used for district heating and cooling. In this study, two issues of the system operating control were investigated. The first issue is the mode switching control from 1-stage to 2-stage. A stable 2-stage heating operation is guaranteed, only if the load-side water inlet temperature is over a certain value, where the 1-stage heating operation should be done first from a cold start. The second issue is oil level control. An oil shortage problem in the low stage compressor, which depends on the degree of suction superheat, was solved by a proper oil level control scheme.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.501-505
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• 2006

A preliminary performance test of a 30RT 2-stage screw heat pump was carried out in order to develop a high performance large-scale unutilized energy source heat pump, which will be used in district heating and cooling. Two issues on the system control were investigated in this study, A stable 2-stage heating operation is guaranteed only if the load-side water inlet temperature is over a certain value, to where the 1-stage heating operation should be done first from a cold start. An oil shortage problem in low stage compressor, which depends on the degree of suction superheat, was solved by the proper oil level control scheme.

• 한국항해항만학회지
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• 제35권3호
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• pp.265-270
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• 2011

본 연구는 건물에너지 효율 향상을 위한 목적으로 기상데이터 변화에 따른 건물 냉 난방부하량을 예측하고 결과를 비교 분석한 것으로, 연구 성과는 다음과 같다. 1)기상청에서 입수데이터를 평가툴인 ESP-r에 활용할 수 있도록 항목별 기상데이터를 개발하였다. 표준기상 데이터의 외기온도, 습도, 풍속은 대부분의 경우 기상청데이터 보다 크거나 높았다. 수평면전일사량은 기상청데이터가 높았고, 직달일사량은 겨울철에는 표준기상데이터가, 여름철에는 기상청데이터가 많은 것으로 나타났다. 2)대학교 캠퍼스 내에 신축된 후생복지관을 대상으로 한 시뮬레이션 결과, 최대난방부하의 경우 표준년도, 2006년, 2009년이 비슷한 반면 2007년은 표준년도 대비 81%, 2008년은 96% 수준이었고, 연간난방부하는 2006년, 2008년의 순으로 난방수요가 많았다. 한편, 냉방부하의 경우에는, 상대적으로 최대냉방부하가 큰 2007년, 2009년의 연간 냉방부하보다 최대냉방부하가 가장 적은 2008년의 연간냉방부하가 더 큰 결과를 보였다. 3)냉 난방기기의 상당시간가동률을 평가한 결과, 표준년도의 최대부하대비 상당시간가동률은 2006~2009년이 표준년도에 비해 대부분 가동률이 낮았다.

• 한국해양공학회지
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• 제27권5호
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• pp.93-98
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• 2013

Fuel gas is an important energy source that is being increasingly used because of the convenience and clean energy provided. Natural gas is supplied to consumers safely through an underground gas-pipe network made of a polyethylene material. In electrofusion, which is one of the joining methods used, copper wire is used as the heating wire. However, it takes a long time for fusion to occur because the electrical resistance of copper is low. In this study, therefore, electrofusion was conducted by replacing the copper heating wire with carbon fiber to reduce the fusion time and improve the production when joining large pipes. Fusion and tensile tests were performed after the electrofusion joint was made in the polyethylene pipe using carbon fiber. The results showed that the fusion time was shorter and the temperature inside the pipe was higher with an increase in the current value. The ultimate tensile strength of specimens was higher than that of virgin polyethylene pipe, except for polyethylene pipes joined using a current of 0.8 A. The best fusion current value was 0.9 or 1.0 A because of the short fusion time and lack of transformation inside the pipe. Thus, it was shown that carbon fiber can be used to replace the copper heating wire.

• 유기물자원화
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• 제13권3호
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• pp.63-70
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• 2005

음식물류폐기물의 직매립 금지로 종량제 봉투에 버려지던 상당량의 음식물류가 제외되면서 도시생활폐기물의 조성은 최근 급변하고 있다. 이에 본 연구에서는 2004년~2005년 2년간 3회에 걸쳐 중소규모의 도시 내 10개 지점에서 배출되는 도시생활폐기물을 발생원에서 수거하여 폐기물의 물리화학적 조성을 조사하고, 이로부터 음식물류폐기물의 직매립 금지조치가 폐기물의 성상변화에 미치는 영향을 정리하였다. 음식물류폐기물의 직매립 금지로 생활폐기물 중의 음식물류의 함량은 2004년도 대비 중량기준으로 약 12% 감소하였으며, 겉보기 밀도도 약 25% 감소하였다. 또한 전체 폐기물 중의 수분함량은 32.3%로 2004년도에 비하여 14.1% 감소하였으며, 폐기물의 저위발열량은 직매립 금지 후 약 32% 증가하여 2991.4 kcal/kg의 값을 나타내었다. 매립폐기물에 의한 매립가스 발생량은 연간 가스발생량 기준으로 최대 5%가 감소되어 매립지에서의 환경오염물질 배출량의 저감효과도 일부 예측되었다.

• 한국환경보건학회지
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• 제22권3호
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• pp.28-36
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• 1996

The objects of this study were to investigate emissions of air pollutant the particles as well as the combustibility of the low grade domestic anthracite coal and imported high-calorific bituminous coal in the fluidized bed coal combustor. The production of air pollution from anthracite-bituminous coal blend combustion in a fluidized bed coal combustor was evaluated. The effects of air velocity and anthracite fraction on the reaching time of steady state condition was also evaluated. We used coal samples the domestic low grade anthracite coal with heating value of 2,010 kcal/kg and the imported high grade bituminous coal with heating value of 6,520 kcal/kg. The experimental results are presented as follows. The time of reaching to steady state was affected by the temperature variation. The steady state time was about 120 minute at 0.3 m/s which was the fastest. It has been found that $O_2$ and $CO_2$ concentration were reached steady state at about 100 minute. As the height of fluidized bed becomes higher, the concentration s of $SO_2$ and $NO_x$ mainly increased. The concentration of freeboard was the highest and emission concentration was diminished. Also, as anthracite fraction increased, the emission of $SO_x$ concentration was increased. But, it has been found that the variation of $NO_x$ concentration with anthracite fraction was negligible and the difference of emission concentration according to air flow rates was negligible, too. It has been found that $O_2$ concentration decreased and $CO_2$ concentration increased as the height of fluidized bed increased. As anthracite fraction increased, the mass of elutriation particles increased, and $CO_2$ concentration decreased. Also, as air velocity increased, $O_2$ concentration decreased and $CO_2$ concentration increased. Regardless-of anthracite fraction and flow rate, the combustible weight percentage in elutriation particles were high in the case of fine particles.

• 한국식품과학회지
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• 제29권4호
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• pp.730-736
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• 1997

저염 동치미 쥬스의 향미특성을 유지하는 가열살균 조건을 찾고자 가열온도와 시간이 총균수와 품질특성에 미치는 영향을 검토하였다. 저염 동치미 쥬스의 제조는 무를 0.5%의 소금용액에 담그어 $20^{\circ}C$에서 발효시켰다. 적당히 발효된 pH 3.8의 동치미 쥬스를 $60{\sim}100^{\circ}C$의 범위에서 $5{\sim}30$분간 가열한 결과 pH와 총산도는 거의 변화가 없었으나 쥬스의 밝기(L값)는 감소하였으며 탁도와 a, b값들은 가열온도와 시간이 증가할수록 약간씩 높아졌다. 총균수는 가열 후 현저히 감소하여 60, $70^{\circ}C$에서 30분씩 가열한 동치미 쥬스는 각각 18, 6 CFU/mL로 감소하였으며 90, $100^{\circ}C$에서 10분간 가열한 후에는 균이 검출되지 않았다. 가열한 동치미 쥬스의 관능적 특성은 $70^{\circ}C$에서 20분간 가열할때까지 크게 변하지 않았으나 그 이상의 조건에서는 익은맛 등의 이취미가 현저히 증가하였다. 가열살균한 동치미 쥬스를 $30^{\circ}C$에서 10일간 저장한 결과 pH, 총산도, 색은 거의 변화가 없었지만 가열하지 않은 동치미는 현저히 변화하였다. 살균한 동치미 쥬스의 저장 중 총균수는 초기 총균수와 거의 같은 수준이었다. 그리하여 동치미 쥬스의 가열살균 조건으로는 쥬스의 특성에 영향을 최소한으로 하고 저장성이 높았던 $60^{\circ}C$에서 30분 또는 $70^{\circ}C$에서 20분간이 적절하였다.