• 한국가스학회지
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• 제19권6호
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• pp.28-33
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• 2015

2012년 7월부터 우리나라 천연가스 열량에 대한 기준이 기존의 표준열량제에서 열량범위제로 변경되면서 가정이나 산업체로 공급되는 가스 열량 변화가 가스기기 성능에 미치는 영향을 규명하고자 하는 노력이 이루어지고 있다. 특히 천연가스를 주 연료로 사용하는 열병합 발전용 엔진의 경우 이러한 열량 변화에 의해 엔진 성능 전반에 걸쳐 영향이 있을 것으로 예상된다. 따라서 이번 연구에서는 열량범위제를 고려한 CNG 열량 변화가 디젤-CNG 혼소엔진의 효율 및 연소특성에 미치는 영향에 대해 조사하였다. CNG 모사 연료의 발열량은 $10,400kcal/Nm^3$에서 $9,400kcal/Nm^3$까지 질소 가스를 CNG에 희석하는 방식으로 변경을 하였다. 우선 디젤연료의 분사시기와 혼소율을 80%로 고정한 조건에서 가스연료의 발열량 변화가 엔진 효율 및 출력 변화에 미치는 영향을 살펴보았으며, 열방출율 및 연소압력 등의 변화를 측정하였다. 실험 결과로부터 가스 열량이 낮아질수록 엔진 출력과 효율이 모두 감소함을 알 수 있었으며, 점화지연시간과 연소기간은 가스 열량 감소에 관계없이 일정하게 유지되는 반면 최대연소압력은 낮아짐을 볼 수 있었다.

• 한국유체기계학회 논문집
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• 제15권3호
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• pp.57-63
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• 2012

Effects of coolant pre-cooling and fuel pre-heating on the performance of a combined cycle using a F-class gas turbine were investigated. Coolant pre-cooling results in an increase of power output but a decrease in efficiency. Performance variation due to the fuel pre-heating depends on the location of the heat source for the pre-heating in the bottoming cycle (heat recovery steam generator). It was demonstrated that a careful selection of the heat source location would enhance efficiency with a minimal power penalty. The effect of combining the coolant pre-cooling and fuel pre-heating was also investigated. It was found that a favorable combination would yield power augmentation, while efficiency remains close to the reference value.

• 대한가정학회지
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• 제18권1호
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• pp.41-46
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• 1980

In order to verify to what extent the rancidity of the soybean oil is occurred and how the various metal ions effect on the rancidity-as a result of applying heat to the soybean oil-the followings are obtained through experiments : 1. From analyzing the refractive index of soybean oil, The results are: the specific gravity-0.925 refractive index-1.475, saponification value-190, acetyl value-5.0, iodine value-120, peroxide value-5.0. 2. The degree of expediting rancidity take the following order : $Cu^{++}$/$Fe^{++}$/$Cr^{++}$/$Zn^{++}$/$Ni^{++}$/$Al^{+++}$. 3. The degree of expediting rancidity of $Cu^{++}$and $Fe^{++}$ is showed the abrubt increase of peroxide value in accordance with the increase of densidity. The most abrubt increase of peroxide show when the duration of heating reaches to the range between 20 minutes and 30 minutes. After heating for 60 minutes no definite variation is showed. 4. The degree of rancidity in heating the soybean oil added $Cu^{++}$, Fe and BHA shows the decrease of peroxide value by 2, 3 after adding $Cu^{++}$0.5 ppm. and heating for 30 minutes. As the result of measuring the value of peroxide after adding $Cu^{++}$ by 1.0 ppm and BHA by 0.01% and heating, peroxide shows the decrease by 7.8 when adding anti-oxidant. $Fe^{++}$ as well as $Cu^{++}$ shows that BHA prevents the metal ions from the expedition of rancidity.

• Journal of Biosystems Engineering
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• 제19권3호
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• pp.211-221
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• 1994

In this study, to maximize the solar energy utilization for greenhouse heating during the winter season, solar energy-underground latent heat storage system was constructed, and the thermal performance of the system has been analyzed to obtain the basic data for realization of greenhouse solar heating system. The results are summarized as follows. 1. $Na_2SO_4{\cdot}10H_20$ was selected as a latent heat storage material, its physical properties were stabilized and the phase change temperature was controlled at $13{\sim}15^{\circ}C$. 2. Solar radiation of winter season was the lowest value in December, and Jinju area was the highest and the lowest value was shown in Jeju area. 3. The minimum inner air temperature of greenhouse with latent heat storage system(LHSS) was $7.0{\sim}7.5^{\circ}C$ higher than that of greenhouse without LHSS and was $7.0{\sim}11.2^{\circ}C$ higher than the minimum ambient air temperature. 4. Greenhouse heating effect of latent heat storage system was getting higher according to the increase of solar radiation and was not concerned with the variation of minimum ambient air temperature. 5. The relative humidity of greenhouse with latent heat storage system was varied from 50 to 85%, but that of greenhouse without LHSS was varied from 30 to 93%. 6. The heating cost of greenhouse with solar energy-latent heat storage system was about 24% of that with the kerosene heating system.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.278-283
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• 2003

Analysis has been carried out to investigate the temperature variation and the uniformity of the temperature distribution of the glass panel by infrared radiant heating. Halogen lamps are used to heat the panel and located near the top and bottom of the rectangular chamber. The thermal energy is transfered only by radiation and the radiation exchange occurs only on the solid surfaces and is considered by using the view factor. The results show that the uniformity of the temperature distribution of the panel is improved but the time for heating increases as the wall reflectivity is large. The temperature difference reaches a maximum in the early stage of the heating process and then decreases until it reaches the uniform steady-state value.

• 한국식품조리과학회지
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• 제6권2호
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• pp.67-76
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• 1990

To observe the propability as the frying oil and oxidative stability of red pepper seed oil, some physico-chemical tests of the oil were examined during 21 days storage period at 5$^{\circ}C$, 15$^{\circ}C$ and 30$^{\circ}C$, and AOM value determined and after heating the oil at 180${\pm}$5$^{\circ}C$ for 40 hours with or without antioxidants. The analysis storage stability of red pepper seed oil showed that the quality of storage group at 5$^{\circ}C$ was almost as good as fresh oil, and the storage group at 30$^{\circ}C$ showed certain degree of rancidity. Change of physico-chemical characteristic during storage were so small so that storage stability of red pepper seed oil was found to be good. AOM stability of red pepper seed oil was 7 hours which is lower than other vegetable oil, but the degree of stability grew greatly after adding phenolic antioxidants, such on TBHQ or PG. As for the chemical change after heating continuously for 40 hours, acid value, peroxide value and refractive index increased, but iodine value decreased as the heating processed. The fatty acid composition also showed the remarkable reduction of linoleic acid. The addition of antioxidants resulted in the delay of oxidation, the degree of which was greater in TBHQ than in PG.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
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• pp.115-118
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• 2014

Since 1st July 2012, the our Goverment and KOGAS have been adopting a calorific value range system from the standard calorific value system. Domestic power plant companies and KOGAS have asked GT manufacture about the effects of the reduction of the calorific value. We received GT manufacture's answer to the question on April 12.2011. Gas components of some GT models were limited to no more than 9% of the C2+ content. Now some of GTs remain under debating whether effects on variation of gas heating or not.

• 한국가스학회지
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• 제20권6호
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• pp.43-49
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• 2016

전 세계적인 천연가스 저열량화 추세에 따라 우리나라 천연가스 열량 기준이 기존의 표준 열량제에서 보다 유연한 열량범위제로 개선되었다. 이 같은 변화는 가정이나 산업체 전반에 걸쳐 가스기기 성능에 직접적인 영향을 미치기 때문에 이를 규명하고자 하는 연구가 필요하다. 특히 열병합 발전용 엔진으로 사용되는 디젤-CNG 혼소엔진의 경우 도시가스를 주 연료로 사용하기 때문에 발열량 변화는 발전 사업자의 수익성 확보와 연관되는 중요한 사안이다. 따라서 본 연구에서는 열량범위제 내에서 허용하는 CNG 발열량 변화가 디젤-CNG 혼소엔진의 배기특성에 주는 영향에 대해 조사하였다. 도시가스 발열량 변화를 모사하기 위해 열량 범위 상한선인 $10,400kcal/Nm^3$의 CNG 연료에 질소를 희석시켜 발열량을 $10,400kcal/Nm^3$에서 $9,400kcal/Nm^3$까지 변경하였다. 혼소율 80% 조건에서 디젤 연료 분사 시기는 16 CAD BTDC, 분사압력은 110 MPa로 고정하고 엔진회전수 및 토크는 1800 rpm/500 Nm으로 설정하여 시험을 수행하였다. 엔진시험 결과 발열량이 감소할수록 불완전연소가 증가하여 THC, $CH_4$ 및 CO 배출량은 증가하는 반면 NOx 배출량은 감소함을 확인하였다. 그리고 이 같은 결과를 바탕으로 배기 특성 변화에 대해 대응할 수 있는 방안에 대해 고찰하였다.

• 한국연소학회지
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• 제15권3호
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• pp.40-47
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• 2010

Calorific value of mixed gas, like liquefied natural gas (LNG), is strongly depends on its compositions which are affected by the mining place and producing time. The variation in calorific value have an direct influence on the combustion characteristics and performances of boiler, burner, vehicle, power plants etc. Thus, developing experimental method to measure exact calorific value is becoming an issue in the related industrial fields. Flame calorimeter is developed to get calorific value at the dynamic equilibrium state using electric substitution method. Refrigerant-11 carries heat from combustor and/or heater to the Peltier elements which pumped it out to the cooling water. It is found out that error in the measured calorific value of methane is 2.86% compared with the theoretical one. Developed design technique and the experimental data will be applied to design the national standard gas calorific value measuring apparatus.

• 한국대기환경학회지
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• 제19권3호
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• pp.285-296
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• 2003

The measurement of the radiation energy, trunk temperature, leaf area index (LAI), air temperature, vapor pres-sure, and precipitation has been conducted under a mixed forest at Kwangneung Arboretum during the period of 2001. Characteristics of the diurnal and seasonal variation of the radiative energy were investigated. The aerodynamic roughness length was determined as about 1.6 m and the mean albedo was about 0.1 The downward short-wave radiation was linearly correlated with the net radiation and its correlation coefficient was about 0.96. From this linear relation, the heating coefficient was calculated and its annual mean value was about 0.21 The albedo and heating coefficient was varied with season, surface characteristics, and meteorological conditions. The diurnal and seasonal variations of radiation energy were discussed in terms of the surface characteristics and meteorological conditions. In the daytime, during clear skies, net radiation was dominated by the shortwave radiation. In presence of clouds and fog, the radiation energy was diminished. At night, the net radiation was entirely dominated due to the net longwave radiation. There was no distinct diurnal variation in net radiation flux during the overcast or rainy days. The net radiation was strongest in spring and weakest in winter. The seasonal development in leaf area was also reflected in a strong seasonal pattern of the radiation energy balance. The timing, duration, and maximum leaf area and trunk temperature were found to be an important control on radiation energy budget. The trunk temperature was either equal or warmer than air temperature during most of the growing season because the canopy could absorb a substantial amount of sunlight. After autumn (after the middle of October), the trunk temperature was consistently cooler than air temperature.