• 한국가스학회지
• /
• 제25권5호
• /
• pp.11-18
• /
• 2021

수소는 동일한 공연비(AF ratio, Air-to-fuel ratio)에서 가솔린에 비해 점화에너지가 현격히 낮기 때문에, 희박한 혼합기 조건에서도 안정적으로 연소할 수 있는 장점을 가지고 있어 연소를 기반으로하는 내연기관에도 적용이 가능하다. 그러나 일부 연소조건에서 역화(Back-fire) 혹은 조기 점화(Pre-ignition)와 같은 이상 연소가 발생하기 쉬운 문제를 가지고 있다. 따라서 본 연구에서는 엔진의 흡기(Intake gas mixture)를 구성하는 신기(Fresh air)와 수소 연료를 각각 냉각하여 공급함으로써, 역화를 최소화하여 최고 출력을 향상하는 연구를 진행하였다. 2.4 L급 전기점화(SI, Spark-ignition)엔진이 사용되었으며 수소는 포트분사 방식(PFI, Port Fuel Injection)으로 공급하였다. 신기의 온도는 터보차저가 장착된 상황에서 인터쿨러(Intercooler)를 이용하여 제어하였으며, 수소의 냉각은 칠러의 냉매와 열교환기를 통하여 직접 냉각 후 공급하였다. 그 결과 신기의 온도를 10~20 ℃가량 냉각시킬 경우 최고출력이 약 6.5~8.6 % 가량 향상되는 것을 확인할 수 있었으며, 수소를 -6 ℃까지 냉각하여 공급할 경우 마찬가지로 약 7.7 % 가량의 최고 출력을 향상할 수 있었다.

• Korean Chemical Engineering Research
• /
• 제52권5호
• /
• pp.574-580
• /
• 2014

이산화탄소($CO_2$) 포집 및 지중저장을 위한 $CO_2$ 수송선용 저장탱크는 액체 $CO_2$와 직접적으로 접촉할 경우 발생할 수 있는 물리적/열적 탱크 손상을 방지하기 위해 화물 선적 단계 이전에 예냉과정을 거쳐야 한다. 본 연구에서는 예냉을 위해 주입되는 저온 $CO_2$ 기체의 탱크 유입량을 계산하기 위해 $CO_2$ 저장탱크 예냉과정의 수학적 모델 식을 제안하였다. 또한 비례-적분(proportional-integral: PI) 제어를 통해 공정을 제어하는 동적 모사 결과를 제시하였다. 이 때 제어 변수를 탱크 내 온도 또는 압력으로 선정한 두 가지 사례를 모사하였으며 그러한 결정이 $CO_2$ 저장탱크의 예냉과정에 미치는 영향을 해석하였다. 결과적으로 예냉과정의 PI제어에는 탱크 내 온도를 제어하는 것보다 압력을 제어하는 우회적인 방식을 택할 때 수학적 모델의 비선형성과 특이점 발생으로 인한 불안정성을 피할 수 있으므로 더 안정된 결과가 도출됨을 보였다.

• 한국식품저장유통학회지
• /
• 제15권6호
• /
• pp.847-851
• /
• 2008

본 연구에서는 농산물 수집용으로 사용되는 팔레트 빈의 활용도를 높일 수 있도록 팔레트 빈의 구조를 차압통풍 예냉과 저온저장에 적용할 수 있도록 개선하였다. 감자, 양파, 감귤에 대한 팔레트 빈 밑면의 통기공 개공율에 따른 송풍저항을 측정하였으며, 팔레트 빈과 차압통풍식 냉각장치를 제작하였다. 감자, 양파, 감귤의 개공율, 퇴적높이, 송풍량 변화의 실험자료를 회귀식으로 나타내었으며, 비교적 높은 결정계수를 얻을 수 있었다. 감자, 양파, 감귤의 팔레트빈을 이용한 차압통풍 예냉시 냉각속도 및 저온저장시 냉각균일도(표준편차)를 시험한 결과, 냉각속도는 각각 $0.8^{\circ}C/hr$ ($21.7{\rightarrow}10^{\circ}C$, 14.5시간), $0.4^{\circ}C/hr$($15.4{\rightarrow}20^{\circ}C$, 32.2시간), $0.7^{\circ}C/hr$($13.7{\rightarrow}1^{\circ}C$, 18.8시간)로 나타났으며, 저온저장시 각 빈별 표준편차는 각각 $0.12^{\circ}C$, $0.12^{\circ}C$, $0.17^{\circ}C$로 나타났다.

• 동력기계공학회지
• /
• 제7권4호
• /
• pp.25-30
• /
• 2003

Hydrocyclone has been widely used for the solid-Liquid separation in many industrial sites because of its comparatively preferable applications that can be applied to wide-range panicle sizes. If seawater with impurities flows through pumps or heat exchanger, it might cause an decrease in efficiency of cooling system. In this paper, we have suggested solid methods of separating impurities from seawater in the cooling system by using a Hydrocyclone. The effects of design factors as solid concentration, cyclone inlet pressure, flow rate and diameter of underflow on the seperating performance of the Hydrocyclone were investigated. The results from the study are summarized as follows: 1) In proportion to the increase of solid concentration, the efficiency of solid-liquid separation is improved. 2) According as the cyclone inlet pressure increases the efficiency of separation is improved. Conclusively, this research suggested that the Hydrocyclone will be used as a pre-treatment system of cooling water in ships, and eventually prevent unexpected accidents in engine systems.

• 한국분무공학회지
• /
• 제17권2호
• /
• pp.64-70
• /
• 2012

Water mist fire suppression systems which use relatively small droplets of water with high injection pressure are increasingly being used in wider applications because of its greater efficiency, low flooding damage and low toxicity. However, the performance of the system significantly relies on the water mist characteristics and it requires better understanding of fire suppression mechanism of water mist. In the present study, computational fluid dynamics simulations were carried out to investigate cooling performance of water mist in heated chamber. The gas phase was prepared with natural convection heat transfer model for incompressible ideal case and then the effects of water mist injection characteristics on cooling capabilities were investigated upon the basis of the pre-determined temperature field. For the simulation of water mist behavior, Lagrangian discrete phase model was employed by using a commercial code, FLUENT. Smaller droplet sizes, greater injection angles and higher flow rates provided relatively higher cooling performance.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
• /
• pp.563-564
• /
• 2006

The effect of different cooling rate on the structure and mechanical properties of Fe-3%Mn-(Cr)-(Mo)-0.3%C steels is described. Pre-alloyed Astaloy CrM and CrL, ferromanganese and graphite were used as the starting powders. Following pressing in a rigid die, compacts were sintered at $1120^{\circ}C$ and $1250^{\circ}C$ in $H_2/N_2$ atmospheres and cooled with cooling rates $1.4^{\circ}C/min$ and $6.5^{\circ}C/min$. Convective cooled specimens were subsequently tempered at $200^{\circ}C$ for 60 and 240 minutes.

• Journal of Advanced Marine Engineering and Technology
• /
• 제11권1호
• /
• pp.53-62
• /
• 1987

The Performance of Pre-combustion Chamber Diesel Engine mainly depends upon the compression, combustion and Expansion Processes. The analysis of varying tendency of the work factors for crank angles during these processes, which are consisted of 5 items such as exothermic energy, flow work, work in nozzle part, kinetic energy and cooling energy, are considered important as basic elements for effective combustion and performance improvement. In this paper, varying tendencies of the theoretical factors are investigated with pressure data through experiments. By the results, the trends of work factors are presented as basic data for comparing the influencing effects on work.

• 신재생에너지
• /
• 제2권2호
• /
• pp.9-15
• /
• 2006

The application of photovoltaics into building as integrated building components has been paid more attention worldwide. Photovoltaics or solar electric modules are solid state devices, directly converting solar radiation into electricity; the process does not require fuel and any moving parts, and produce no pollutants. And the prefab building method is very effective because the pre- manufactured building components is simply assembled to making up buildings in the construction fields especially the sandwich panel. So, the purpose of this research is to integrated prefab building materials depending on the cooling type of PV modules. It is concluded that the prediction of BIPV system's performance should be based on the more accurate PV module temperature. From the basis of these results on the correlation of temperature and irradiation were obtained.

• 한국초전도ㆍ저온공학회논문지
• /
• 제3권2호
• /
• pp.5-9
• /
• 2001

For the development of a small-sized superconducting magnetic energy storage($\mu$SMES) system we designed, fabricated and tested a model coil consisting of five coils with different features. e.g. winding tensions. bore diameters and materials. cooling channels. The results show that even in the highly pre-stressed small coil the quench currents of the coils are degraded to about 70% of their coils critical current. The quench currents of the coils with natrow cooling channels are two times as high as that of the coil without spacers. The test results also indicate that the usual training effect depends on the winding tensions of the coils according to materials of the bobbin.

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2009년도 하계학술발표대회 논문집
• /
• pp.248-253
• /
• 2009

For the energy's effective utilization, the mixed humidifier has been developed and popularized by combining the cooling dehumidifier with the desiccant humidifier properly. This has contributed in many ways to the industry. Hybrid Desiccant Dehumidifier that would be shown in this study could be indispensible in site due to the reduced equipment, with more than 50% reduction in energy.