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전산유체역학을 이용한 미세조류 배양용 광생물반응기의 정량적 평가 방안
서일환 ( I. -h. Seo ),이인복 ( I. -b Lee ) 한국농공학회 2010 한국농공학회 학술대회초록집 Vol.2010 No.-
Renewable energy has been interested due to the fossil energy depletion and the carbon dioxide reduction. Bio-diesel is one of the most desirable renewable energy because it can alternate the diesel from petroleum directly. However, the bio-diesel using soybean, canola, corn crop, etc. can be confronted with food consumption. Because a microalgae has higher oil lipid contents and rapider growth rates comparing to the earlier raw materials, it can be a good source for bio-diesel production. Because pond production system is limited in distinguishable four seasons and insufficient land availability in Korea, photo-bioreactor (PBR) is a good alternative way to cultivate microalgae by artificially controlling the internal environments such as light, nutrients, temperature, carbon dioxide, and so on. Despite the availability of these PBRs, only few of them can be practically used for mass production. In this study, computational fluid dynamics (CFD) was used to find an optimum bubble-column PBRs for mass cultivation of the microalgae. Multi-phase models including bubble movement, meshes & time step independent tests were used to design the three dimensional CFD model. The model was validated comparing to the field experiments including particle image velocimetry (PIV) tests. Using the validated CFD model, various types of PBRs were compared quantitatively with consideration of a microalgae growth model adaptable for the CFD model. An evaluation method for mixing efficiency in the PBRs was developed by tracing the movement of each particle in the PBRs connected with the growth model according to the light intensity. The results showed that the mixing efficiency and uniformity in the 20 L of plate type PBRs can be enhanced by 73% and 36% respectively when the baffle was installed in order to guide the fluid flow using bubble injection.
돈사의 시설 및 환기구조에 따른 돼지 호흡기성 질병 발생 가능성
서일환 ( Seo I. -h. ),이인복 ( Lee I. -b. ),황현섭 ( Hwang H. -s. ),홍세운 ( Hong S. -w. ),( Jessie P. Bitog ),유재인 ( Yoo J. I. ),권경석 ( Kwon K. -s. ),김용희 ( Kim Y. -h. ) 한국농공학회 2008 한국농공학회 학술대회초록집 Vol.2008 No.-
The typical diseases for pigs in Korea are Porcine epidemic diarrhea (PED), Porcine reproductive and respiratory syndrome (PRRS), Post weaning multi-systemic wasting syndrome (PMWS), and Porcine respiratory disease complex (PRDC). The main factor for the occurrence of these diseases specially the respiratory diseases is the environmental condition particularly ventilation inside the pig house. Considering that Korea has 4 distinct season, the environmental condition in the pig house changes every season. The purpose of this study was to find the relationship between the configuration of the structure and ventilation system of pig houses and the occurrence of pig respiratory disease. The effect of internal airflow distribution to internal disease dispersion in pig house was analyzed. Several field experiments were conducted at several pig farms to understand the environmental control in relation to disease occurrence. To overcome the difficulties of conducting field experiments and obtain internal airflow visualization quantitatively and qualitatively, computational fluid dynamic (CFD). The accuracy of the simulations was preliminarily examined and improvements were made in the model based form the seasonally collected farm data.
새만금 간척 지역의 비산 및 부유 먼지 확산 모니터링 및 예측
황현섭 ( H. -s. Hwang ),이인복 ( I. -b. Lee ),서일환 ( I. -h. Seo ),홍세운 ( S. -w. Hong ),( J. Bitog ),유재인 ( J. -i. Yoo ),권경석 ( K. -s. Kwon ),최지선 ( J. -s. Choi ) 한국농공학회 2009 한국농공학회 학술대회초록집 Vol.2009 No.-
A study on fugitive dust dispersion was conducted in a 40,100ha reclaimed land located at the west coastal part of Korea. The dusts are composed mainly of minerals with high salinity that is very harmful to human’s health such as skin and eye irritations and If frequently inhaled, respiratory disease can occur. More so, the highly concentrated salty dusts can be very harmful to farms located nearby. A computational fluid dynamics (CFD) model was developed to predict the dispersion of fugitive dust from Saemangeum reclaimed land considering the topography of the area. Field experiment is the ideal method to understand real aerodynamic phenomenon. Nevertheless, it is very difficult to find a correlation between weather condition and dust dispersion because of limited measuring points, labor and time. Moreover, the weather condition is always unstable and unpredictable as well as cannot be artificially controlled. To overcome these limitations, CFD simulation was used to quantitatively and qualitatively analyze the dust dispersion phenomenon according to various weather conditions. Great effort has been needed to improve the CFD accuracy with topographical design, mesh structure, particle generation, and computational process by parallel processing technique. Results from this study in 2006, 2007 and 2008 showed that the changes in dust source are highly connected with the changes of dust concentration. The dust concentration shows a decreasing trend in 2008, and it is expected to decrease further as more dust source areas are being covered by plants. The samples analyzed through SEM showed that most dust particles are large in size with irregular dimension. Dust dispersion ranges of CFD result were compared with that of field experiment at the same measuring points for the CFD validity, and the results at stable weather condition were very acceptable with an average error of 6.8%. The vertically dust concentration of the CFD results also became very similar with the general log-profile of fugitive and suspended dust presented by Gillies et al. (2004). The results also showed that the dispersion of the fugitive dust was mainly affected by particle size, wind speed as well as wind direction. On the basis of 10 μm particle size, the diffused distance of fugitive dust resulted in 3,100m with the wind speed of 1.7m/s at 10 m height from the ground while 6,300m with 3.9m/s. Through this study, it was found that the CFD technology can be effectively used to complement the field experiment at studies and more accurate of reliable results can be obtained.
실시간 신호처리를 위한 가변구조 Data Acquisition Buffer의 구조를 갖는 DSP평가용 System.
안동순,서호선,차일환,Ahn D. S.,Seo H. S.,Cha I. W. 한국음향학회 1989 韓國音響學會誌 Vol.8 No.5
일반 DSP들은 새로운 algorithm 및 응용 system의 개발을 위해서 전용 development system 및 simulator가 필수 불가결의 요소이다. 그러나 대부분 development system은 일반화된 내부 구조에 의해 그 유연성에 한계가 존재한다. 본 연구에서는 A/D입력과 D/A출력 data를 저장하는 buffer의 길이를 program에 의해 1 sample 단위부터 최대 2K sample 단위까지 가변할 수 있도록 하고, 이들 buffer도 2중 구조로 하여 연속 신호의 처리가 가능도록 한 DSP평가용 system을 개발하였다. For developing new algorithms or dedicated hardware by using general purpose Digital Signal Processor chip, emulator H/W and simulator S/W are indispensible. But the most of DSP emulators have limitations on H/W flexibility according to their generalized architectures. In this paper, a DSP evaluation system for real time signal processing was developed using TMS 32020. The I/O buffers storing acquisition data of the system were designed to have variable length $(1\sim2048samp1es) &$ sampling frequency $l00\sim8KHz$.
CFD 시뮬레이션을 활용한 미세조류 배양용 버블 칼럼 광생물반응기 설계
유재인 ( J. -i. Yoo ),이인복 ( I. -b. Lee ),황현섭 ( H. -s. Hwang ),서일환 ( I. -h. Seo ),홍세운 ( S. -w. Hong ),( J. Bitog ),권경석 ( K. -s. Kwon ),최지선 ( J. -s. Choi ) 한국농공학회 2009 한국농공학회 학술대회초록집 Vol.2009 No.-
Photobioreactors (PBRs) that houses and cultivates microalgae providing a suitable environment for its growth, such as light, nutrients, CO2,heat, etc. is now getting more popular in the last decade. Among the many types of PBRs, the bubble column type is very attractive because of its simple construction and easy operation. However, despite the availability of these PBRs, only a few of them can be practically used for mass production. Many limitations still holdback their use especially during their scale-up. To enlarge their culture volume and productivity by supplying optimum environmental conditions, various PBR structures and processes for controlling are needed to be compared. In this study, computational fluid dynamics (CFD) was used to design a bubble-column type PBR to economically take the place of field experiments. CFD is a promising technique which can simulate the growth and production of microalgae in the PBR. To study bubble column PBR with CFD, the most important factor is the possibility of realizing bubble. In this study, multi-phase models which are generally used were compared by theoretical approaches and 2D preliminary simulations. As a result, the VOF (Volume of Fluid)model was found to be the most effective to realize the bubble shape and flow inside PBR which is made by bubble injection. Considering the accuracy and economical efficiency, 0.005 sec of time step size was chosen for 2.5 mm mesh size. With these initial conditions, 3-D PBR trial simulation and PIV (Particle Image Velocimetry) validation test were conducted. The verified CFD simulation model will be used as criteria for PBR scale-up research.
딸기 고설재배시설에서의 이산화탄소 농도 유지를 위한 방풍막 설치 효과
김용희(Y.-H. Kim),이인복(I.-B. Lee),전창후(Changhoo Chun),황현섭(H.-S. Hwang),홍세운(S.-W. Hong),서일환(I.-H. Seo),유재인(J.-I. Yoo),J.P. Bitog,권경석(K.-S. Kwon) (사)한국생물환경조절학회 2009 생물환경조절학회지 Vol.18 No.1
딸기 재배용 온실 내 재배 벤치에서 생산량을 높이기 위하여 벤치 주위에서 이산화탄소를 공급하는 경우 환기 등에 의한 풍속으로 인하여 작물 주변의 적정 가스 농도가 유지되지 못하는 현상이 발생한다. 본 연구에서는 이산화탄소를 보존시키고자 벤치 주변에 방풍막을 설치하는 방안에 대하여 분석하였다. 온실 내 벤치와 방풍막을 2차원 CFD 시뮬레이션으로 모델링하고 온실 내 공기의 풍속과 이산화탄소의 공급을 구현하여 보존되는 이산화탄소의 농도 분포를 살펴보았다. 또한 이를 통하여 설계한 온실의 환경조건에서의 적정한 방풍막 설치 높이를 제안하고자 하였다. 시뮬레이션에서 구현한 온실 내 풍속조건은 0.5, 1.0, 1.5 ㎧ 이고, 방풍막의 높이는 미설치, 0.15, 0.30 m이고, 각 조건에서의 이산화탄소 농도를 측정하였다. 설계상의 편의와 시뮬레이션의 간소화를 위하여 벤치위의 작물은 없는 것으로 가정하였다. 일반적인 온실 내의 풍속 조건은 1.0 ㎧로, 시뮬레이션 결과 이 때 벤치 위에서의 평균 이산화탄소 농도는 방풍막 미설치 시 420 ppm, 방풍막 설치 높이 0.15 m일 때 580 ppm, 0.30 m일 때 653 ppm으로 나타났다. 딸기의 최대 생산량을 위한 적정 생육 이산화탄소 농도가 600~800 ppm 정도인 것을 고려하여, 이와 같은 환경조건에서의 방풍막의 설치 높이는 0.30 m가 적당할 것으로 판단하였으나 이산화탄소 공급조건, 직물의 배치 등의 조건 변화에 따른 상황에서의 연구가 추가적으로 수행되어야 할 것이다. 이처럼 방풍막의 설치가 온실 내에 시비한 이산화탄소를 직물 주변에 머무르게 하는 효과가 상당함을 알 수 있었으며, 설계한 환경조건에서 작물별로 적정한 수준의 이산화탄소량이 공급되고 있는지를 판단하기 위하여 CFD 기술이 이용될 수가 있음을 보였다. The influence of windbreak to minimize the ventilation velocity near the plant canopy of a greenhouse strawberry was thoroughly investigated using computational fluid dynamics (CFD) technology. Windbreaks were constructed surrounding the plant canopy to control ventilation and maintain the concentration of the supplied CO₂ from the soil surface close to the strawberry plants. The influence of no windbreak, 0.15 m and 0.30 m height windbreaks with varied air velocity of 0.5, 1.0 and 1.5 ㎧ were simulated in the study. The concentrations of supplied CO₂ within the plant canopy of were measured. To simplify the model, plants were not included in the final model. Considering 1.0 ㎧ wind velocity which is the normal wind velocity of greenhouses, the concentrations of CO₂ were approximately 420, 580 and 653 ppm (1×10?? ㎏/㎥) for no windbreak, 0.15 and 0.30 m windbreak height, respectively. Considering that the maximum concentration of CO₂ for the strawberry plants was around 600-800 ppm, the 0.30 m windbreak height is highly recommended. This study revealed that the windbreak was very effective in preserving CO₂ gas within the plant canopy. More so, the study also proved that the CFD technique can be used to determine the concentration of CO₂ within the plant canopy for the plants consumption at any designed condition. For an in-depth application of this study, the plants as well as the different conditions for CO₂ utilization, etc. should be considered.