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나노유체 : 비정상열선법 나노유체 열전도도 측정 시 자연대류효과 제거법
구준모 ( June Mo Koo ),한기수 ( Ki Soo Han ),( Clement Kleinstreuer ) 한국액체미립화학회 2012 한국액체미립화학회 학술강연회 논문집 Vol.2012 No.-
Significant deviations between published results have been reported when measuring the effective thermal conductivity of nanofluids with the transient hot-wire method (THWM). This may be attributed to a poor selection of the temperature data range, which should meet the following conditions. The start time should be chosen after the conductive heat flux delay time, while the end time should be selected before a crossover point when natural convection becomes significant. Furthermore, the data range should be large enough not to be affected by the local oscillation of the data estimates. Proper selection of the temperature data range depends also on both the fluid type, e.g., water or EG, and the base temperature. As the most suitable temperature data range cannot be predetermined before taking measurements, it is recommended that temperature history data are carefully investigated for each data acquisition cycle. Although the nanofluid viscosity increases slightly and the thermal expansion coefficient decreases significantly, natural convection has a significant impact on THWM-accuracy when measuring thermal mixture properties. This may be the result of local motion of nanoparticles invoking natural convection early on. Considering an EG-based 1.06 vol.% ZnO nanofluid, he thermal conductivity was measured to increase by 5.4%.
요인배치법과 라틴방격법을 통한 건물 냉난방 부하 예측의 정확도 비교연구
최연희(Youn Hee Choi),구준모(June Mo Koo),송두삼(Doo Sam Song) 대한설비공학회 2020 대한설비공학회 학술발표대회논문집 Vol.2020 No.6
본 연구의 본래 목적은 건물의 냉/난방 부하의 최적 예측의 정확도 향상에 있다. 따라서 본 연구에서는 일반적으로 많이 활용되는 실험계획법의 디자인 방법의 모델 정립 특성, 정확도 비교, 요인별 영향도 분석을 통해 요인배치법의 한계를 정의한다. 요인배치법과 비교하여 라틴방격법의 경우, 보다 정확한 건물의 냉난방 부하, 계산의 경제성과 더불어 모델의 비선형적인 특성을 고려할 수 있는 것을 분석할 수 있었다. 이는 실제 조건에서 인자들의 수준이 요인배치법과 같은 상한, 하한 레벨에 해당되기 보다 세밀하고 복잡한 조건에 해당한다. 시뮬레이션 및 분석을 통한 연구결과, 요인배치법의 경우, 실제 냉난방부하의 예측 및 샘플링수에 대한 오차의 의존성이 높다. 반면에 라틴방격법을 통한 연간 냉난방 부하의 예측의 정확도 및 비선형적인 요소의 고려는 요인배치법에 비해 월등한 것으로 나타났다. 따라서 실제 부하의 예측 등 건물 분야에서 라틴방격법의 활용이 보다 적합할 것으로 보인다.
김영준(Young Jun Kim),이종연(Jong Yeon Lee),구준모(June mo Koo),강용태(Yong Tae Kang) 대한설비공학회 2010 설비공학 논문집 Vol.22 No.4
The objectives of this study are to analyze the possibility of the landfill gas recycling for the middle and small scale landfills where the recycling facilities are not installed in Korea. It was found that the power generation plants by landfill gas were installed in domestic 15 landfills and the gas engine generation was adopted in 14 places. As the result of economic analysis, the landfill gas recycling is found to be available in 12 places and CERs of 153,693 tCO2e can be secured per year. Through the reduction of the air pollutants and VOCs, the social benefits of 730 million won accrue per year. Also, the power production of 18.8 GWh will substitute the crude oil imports of 4,048 TOE and the revenue of 2.49 billion won is expected to power trading. It is also found that the power generation plants by landfill gas will give the social benefits such as the reduction of the environmental problems and the substitution effect of crude oil imports.
혼 타입 초음파 분산기 팁 발생입자 특성 및 나노유체 물성에의 영향
강치훈(Chi-Hoon Kang),강용태(Yong-Tae Kang),구준모(June-Mo Koo) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
The horn type ultrasonic homogenizer is used in the nanofluid dispersion process owing to its high power density delivered to the fluid causing cavitation effects. However, it is found that the horn tip made of titanium-vanadium-alumina alloy comes off from the body and entrains into nanofluids, which could affect the thermal properties of nanofluids. From the SEM/EDX analysis, it is found that the entrained particle is mainly composed of titanium. The amount of entrained particles is found to increase with the sonication power and duration. The post-sonication size of the entrained particles ranges mainly 300-400㎚ under the 20% of the maximum power condition, and 100-200㎚ at the maximum power condition. Particles grow in size with time to precipate to the bottom. In this study, the characteristics of the entrained particles are identified and the effects of the entrained particles on the thermal properties of nanofluids are investigated.