• 한국추진공학회지
• /
• 제2권2호
• /
• pp.99-107
• /
• 1998

ASE120 엔진 연소기에 쓰이는 벤츄리(venturi)형 예혼합기의 혼합성능을 시험 평가하였다. 이 시험에서는 가스연료 대신 찬공기를 주입하고 혼합공기의 온도를 측정함으로 혼합정도를 계산하였다. DOE 기법을 사용하여 시험변수 matrix를 구성하고 시험결과를 분석하여 최적의 변수조합을 가지는 형상을 도출하였다. 선정된 형상에 대하여 확인시험이 수행되었다.

• 설비공학논문집
• /
• 제27권12호
• /
• pp.620-625
• /
• 2015

The summer climate is very hot and humid in Korea. Humidity is an important factor in determining thermal comfort. Recently, research on dehumidification device development has been attempted to save the energy required for operating the dehumidifier. Existing dehumidification systems have disadvantages such as wasting energy to drive the compressor. Meanwhile, dehumidification systems with membranes can dehumidify humid air without increasing the dry bulb temperature. Therefore. they don't have to consume cooling energy. In this paper, the installation conditions for a membrane system were analyzed to improve the shape and optimum performance of the system. The results showed that the distance between elements was the critical system design factor, and that a distance of 20 mm was the optimal condition for the pressure drop and flow characteristics of the internal air flow.

• 한국환경과학회지
• /
• 제27권4호
• /
• pp.251-259
• /
• 2018

This study was conducted to determine the effects of combination of air temperature and soil water content on the growth, physiological disorder rate, and yield of hot peppers. The study was carried out in a typical plastic house (open on one side and with ventilation fans on the other side), which was maintained with gradient air temperature (maximum difference in air temperature: $6^{\circ}C$). The deficit irrigation (DI) treatment commenced 65 days after transplanting. The height of plant and fresh and dry weights of the stem increased at high air temperature (ambient + $6^{\circ}C$, extreme high temperature; EHT). Furthermore, the leaf area decreased significantly with the DI treatment. There were no significant differences in the stem diameter, number of branches, and fresh and dry weights of the leaves among all the treatments. The net photosynthesis rate of the full irrigation (FI) treatment was higher than that of the DI treatment. The photosynthesis rate at ambient air temperature was $19.7{\mu}mol\;CO_2m^{-2}{\cdot}s^{-1}$, the highest among all the treatments; however, the photosynthesis rate of the EHT treatment decreased by 60% ($12.3{\mu}mol\;CO_2m^{-2}{\cdot}s^{-1}$). Additionally, the formation of guard cells in the leaf was abnormal with the EHT treatment, and there was a decrease in translocation efficiency. The effects of air temperature treatment were more pronounced on the physiological disorder rate and yield. The physiological disorder rate of the EHT treatment was the highest under the DI treatment condition. The yield of the AFI (ambient air temperature with full irrigation) treatment was 3,771 kg/10a, the highest among all the treatments; however, the yield of the EHT treatment with DI and FI was 1,282 and 1,327 kg/10a, respectively. These results indicate that growth and physiological disorder rate improved with the EHT treatment; however, there was a decrease in yield. Furthermore, the formation of guard cells was abnormal and malfunctional.

• International Journal of Air-Conditioning and Refrigeration
• /
• 제15권1호
• /
• pp.34-45
• /
• 2007

In order to reduce the compression power and to use the overall energy contained in LNG effectively, a combined cycle is devised and simulated. The combined cycle is composed of two cycles; one is an open cycle of liquid/solid carbon dioxide production cycle utilizing LNG cold energy in $CO_2$ condenser and the other is a closed cycle gas turbine which supplies power to the $CO_2$ cycle, utilizes LNG cold energy for lowering the compressor inlet temperature, and uses the heating value of LNG at the burner. The power consumed for the $CO_2$ cycle is investigated in terms of a solid $CO_2$ production ratio. The present study shows that much reduction in both $CO_2$ compression power (only 35% of the power used in conventional dry ice production cycle) and $CO_2$ condenser pressure could be achieved by utilizing LNG cold energy and that high cycle efficiency (55.3% at maximum power condition) in the gas turbine could be accomplished with the adoption of compressor inlet cooling and regenerator. Exergy analysis shows that irreversibility in the combined cycle increases linearly as a solid $CO_2$ production ratio increases and most of the irreversibility occurs in the condenser and the heat exchanger for compressor inlet cooling. Hence, incoming LNG cold energy to the above components should be used more effectively.

• Journal of Nutrition and Health
• /
• 제32권6호
• /
• pp.637-643
• /
• 1999

The effects of yam(Dioscorea) on lowering cholesterol level and its mechanism were investigated. The concentrations of plasma and liver lipids, and the excretions of fecal neutral sterol and bile acid were measured in male Sprague-Dawley rats. Five Groups of 8 rats were fed hypercholesterolemic diet(1% cholesterol, 10% lard ; control), hypercholesterolemic diet plus 15% or 30% dried yam powder prepared by either hot-air(15HY, 30HY) or freeze dry(15FY, 30FY) for 4wk. Plasma total lipid, total cholesterol and cholesterol level was also significantly lower(28%, p<0.05), buy HMG-CoA reductase activity was higher in 30FY(230%, p<0.05) than in control. Although no significant differences in fecal neutral sterols were observed among groups, the yam-fed rats apparently had less bacterial degradation of cholesterol as indicated by a significantly greater of fecal cholesterol to coprostanol than in controls. Total fecal bile acids were significantly greater in rats fed yam(15HY : 5 folds, 15FY ; 12,30HY ; 12, 20FY ; 22) than in controls. The ratio of secondary to primary bile acids was almost 8 times lower in 30FY than in control. These data indicate that yam lowers cholesterol both in plasma and in liver through increasing fecal bile acid excretion as well as HMG-CoA reductase activity. Freeze-dried yam, which possesses viscosity, was more effective in cholesterol-lowering action than hot-air dried one.

• Journal of the Korean Wood Science and Technology
• /
• 제34권1호
• /
• pp.7-14
• /
• 2006

국산 소나무 간벌재를 이용한 수심 정각새(단면치수 $150{\times}150mm$)의 안전하고 신속한 건조를 위하여 열풍건조와 마이크로파건조중 수심 정각새의 함수율 분포와 그 변이를 3차원적으로 탐색하였다. 실험결과 마이크로파건조를 통하여 72시간 이내에 함수율 10% 미만까지 건조가 가능하였고 표면할열 발생도 최소화할 수 있었다. 건조 중 함수율 분포는 마이크로파건조의 경우 초기함수율 분포에 영향을 크게 받았다. 그러나 열기건조의 경우 초기함수율 분포가 건조초기에만 영향을 미치는 것으로 나타났다.

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2008년도 하계학술발표대회 논문집
• /
• pp.761-768
• /
• 2008

This paper presents the results of a laboratory study on the thermal conductivity of sand(silica, quartzite, limestone, sandstone, granite and masonry sand)-water mixtures used in ground heat exchanger backfilling materials. Nearly 260 tests were performed in a thermal conductivity measuring system to characterize the relationships between the thermal conductivity of mixtures and the water content. The experimental results show that the thermal conductivity of mixtures increases with increasing dry density and with increasing water content. The most widely used empirical prediction models for thermal conductivity of soils were found inappropriate to estimate the thermal conductivity of unsaturated sand-water mixtures. An improved model using a exponential relationship to compute the thermal conductivity of dry sands and empirical relationship to assess the normalized thermal conductivity of unsaturated sand-water mixtures is presented.

• 설비공학논문집
• /
• 제27권9호
• /
• pp.475-483
• /
• 2015

In Korea, a typically hot and humid summer means that air-conditioners consume a large quantity of electricity; accordingly, the simultaneous usage of an indirect evaporative cooler may reduce the sensible-heat level and save the amount of electricity that is consumed. In this study, the heat-transfer and pressure-drop characteristics of an indirect evaporative cooler made of paper/plastic film were investigated under both dry and wet conditions; for the purpose of comparison, an indirect evaporative cooler made of plastic film was also tested. Our results show that the indirect evaporative efficiencies under a wet condition are greater than those under a dry condition, and the efficiencies of the paper/plastic sample (109% to 138%) are greater than those (67% to 89%) of the plastic sample; in addition, the wet-surface, indirect evaporative efficiencies of the paper/plastic sample are 32% to 36% greater than those of the plastic sample. Further, the wet-surface pressure drops of the paper/plastic sample are 13% to 23% larger than those of the plastic sample, and this might have been caused by the surface roughness of the samples. A rigorous heat-transfer analysis revealed that, for the plastic sample, 30% to 37% of the wet channels remained dry, whereas all of the channels were wet for the paper/plastic sample.

• Current Research on Agriculture and Life Sciences
• /
• 제1권
• /
• pp.151-158
• /
• 1983

마늘의 저장성(貯藏性) 향상(向上)을 위한 기초자료(基礎資料)를 얻기위해 난지계(暖地系)인 남해재래(南海在來)와 한지계(寒地系)인 달성재래(達成在來)를 각각(各各) 시기별(時期別)로 수확직후(收穫直後) 구(球)의 기부(基部)로부터 줄기길이를 7cm 및 25cm로 남긴 후 열풍건조기(熱風乾燥機)에서 $40^{\circ}C$로 1일(日) 12시간(時間)씩 4일간(日間) 건조(乾燥)한 후 중량감소율(重量減少率)을 관행건조(慣行乾燥)와 비교(比較)하고 저장중(貯藏中) 발근(發根), 맹아(萌芽) 및 부패정도(腐敗程度)를 조사(調査)한 결과(結果)는 다음과 같다. 열풍건조(熱風乾燥) 4일후(日後)의 중량감소율(重量減少率)은 남해재래(南海在來)의 7cm 구(球)에서는 관행건조(慣行乾燥) 13일(日)의 효과(效果)가 있었으며 25cm 구(球)에서는 14일(日)의 효과(效果)가 있었다. 달성재래(達成在來)는 7cm 처리(處理)의 4일간(日間) 열풍건조(熱風乾燥) 효과(效果)는 조기수확(早期收穫), 적기수확(適期收穫), 만기수확별(晩期收穫別)로 관행건조일수(慣行乾燥日數)에 각각(各各) 22일(日), 18일(日), 16(日)의 효과(效果)가 있었으며 25cm처리(處理)의 4일간(日間) 열풍건조(熱風乾燥) 효과(效果)는 조기수확(早期收穫), 적기수확(適期收穫), 만기수확별(晩期收穫別)로 각각(各各) 관행건조(慣行乾燥)의 18일(日), 16일(日), 14일(日)의 효과(效果)가 있었다. 저장초기(貯藏初期)의 사경(砂耕)에 의한 발근(發根), 맹아(萌芽)는 열풍건조구(熱風乾燥區)가 관행건조구(慣行乾燥區)에 비하여 지연(遲延)되는 경향(傾向)을 보였다. 저장후기(貯藏後期)의 인편상태(鱗片狀態)는 열풍건조(熱風乾燥)가 관행건조(慣行乾燥)에 비해 식용가능(食用可能)한 인편수(鱗片數)가 많았으며 부패인편수(腐敗鱗片數)는 적었다.

• 설비공학논문집
• /
• 제29권1호
• /
• pp.15-20
• /
• 2017

The summer climate is very hot and humid in Korea. The humidity is an important factor in determining thermal comfort. Recently, the research for dehumidification device development has been attempted to save energy that is required for the operation of the current dehumidifiers on the market. Existing dehumidification systems have disadvantages such as wasting energy to drive a compressor. Meanwhile, dehumidification systems with membranes can dehumidify humid air without increasing the dry bulb temperature so it doesn't have to consume cooling energy. In this paper, the cooling energy savings was studied when a dehumidification system was applied in a model building instead of a chiller. The sensible heat load was almost the same result, but the latent heat load was decreased by 38.9% and the total heat load was decreased by 8.5%. As a result, electric energy used to drive the compressor in a chiller was saved by applying a membrane air-conditioning system instead.