공기연령 이론 및 전산유체역학 기법을 이용한 환기 효율 분석

권경석 ( K. -s. Kwon ),이인복 ( I. -b,Lee ),황현섭 ( H. -s. Hwang ),홍세운 ( S. -w. Hong ),서일환 ( I. -h. Seo ) 한국농공학회 2010 한국농공학회 학술대회초록집 Vol.2010 No.-

In agricultural buildings, environmental conditions are influenced by the ventilation system. Therefore, understanding of the ventilation process is important to improve the condition of growth environments. Notable researches in the field of building sciences have been using a theory known as "Age of air" to investigate ventilation efficiencies. However, "Age of air" has not yet been applied in agricultural fields. The LMA and LMR concepts based on this theory were used to evaluate the distribution of the fresh air and the potential for eliminating contaminants inside the structure. However the experimental methods for measuring these values have been limited due to a shortage of experimental devices. In addition, laboratory experiments is always laborious, time consuming and expensive. Therefore, in this study, the "Age of air" theory and CFD were both employed. As a basic step, a 3-dimensional chamber with narrow width was designed to accurately implement and verify the "Age of air" theory in the CFD analysis. The inlet was fixed but the outlet was varied in order to find the differences and characteristics of the ventilation efficiencies. The results by the CFD simulation following the developed method were compared with the results of laboratory experiment which was conducted via tracer gas approach. In validating the computation of the LMAs and the LMRs, the results showed that they had a similar tendency of distribution and the average time difference was 39s. Considering the condition of the experimental environments, it could be concluded that the simulation for implementation the "Age of air" was designed reasonably. The results showed that when the ventilation rate was increased, the values of the LMAs and the LMRs were smaller however, comparing the air exchange efficiency; the values had an opposite tendency. It showed that the efficiency of total air exchanges was 0.31 in Case 3-1 and was superior to the other cases. Based on the results of this study, the research could be upgraded to quantitatively determine the overall or local ventilation efficiency in the agricultural facilities such as greenhouses and livestock houses using the "Age of air" theory.

CFD를 활용한 복잡한 지형 내 축산 악취의 확산 예측

홍세운 ( S. -w. Hong ),이인복 ( I. -b. Lee ),황현섭 ( H. -s. Hwang ),서일환 ( I. -h. Seo ),유재인 ( J. -i. Yoo ),( J. P. Bitog ),권경석 ( K. -s. Kwon ),최지선 ( J. -s. Choi ) 한국농공학회 2009 한국농공학회 학술대회초록집 Vol.2009 No.-

Odor is one of the major nuisances in the environment. In most countries, odor annoyance from livestock production is an increasing problem in the community. In order to reduce the odor inconvenience and establish a good relation between livestock industries and the surrounding communities, many studies on the odor dispersion, such as diffusion simulations and field experiments have been investigated. Computational fluid dynamics (CFD) has been effectively and widely used to study this kind of research. CFD considers both various wind conditions as well as topographical conditions to study aerodynamic phenomenon. Therefore, the ultimate objective of the study was to develop an aerodynamic model to predict qualitatively and quantitatively odor diffusion from livestock. During the first year of this 3-year study, various phenomena and factors of odor diffusion from livestock houses were investigated from field experiments. In the second year, mesh models of the study area with a 1.8km radius were built with 5m resolution. Modules for the atmospheric phenomena were also made by user defined functions and linked into a main computing module. The dispersion of odor was predicted by the 3D CFD model and practically agreed to the field measured data. Later, this model will be used to arrange the odor-related conflicts as well as to predict the odor dispersion according to various meteorological conditions.

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.

CFD 기술을 이용한 자연환기식 다연동 온실의 환기 비교 연구

홍세운(Hong S.-W.),이인복(Lee I.-B),윤남규(Yun N.-K),황현섭(Hwang H.-S.),서일환(Seo I.-H),J.P.Bitog,유재인(Yoo J.-I.),권경석(Kwon K.-S.),김용희(Kim Y.-H.) 한국생물환경조절학회 2008 한국생물환경조절학회 학술발표논문집 Vol.17 No.1

BES 기법을 이용한 자연환기식 육계사의 난방에너지 분석

홍세운,이인복,홍희기,서일환,황현섭,유재인,권경석,하태환,김기성,Hong, S.W.,Lee, I.B.,Hong, H.K.,Seo, I.H.,Hwang, H.S.,Bitog, J.P.,Yoo, J.I.,Kwon, K.S.,Ha, T.H.,Kim, K.S. 한국농공학회 2008 한국농공학회논문집 Vol.50 No.1

Most of the broiler houses in Korea have experienced problems on controlling the environmental conditions such as suitability, stability and uniformity of rearing condition inside the broiler house. It is very critical which if not properly controlled, would cause serious stress on the chickens. It is therefore urgent to develop optimum designs of naturally ventilated broiler house which is appropriate to the four seasons of Korea. Field experiment for this matter is very difficult to conduct due to the unpredictable and uncontrollable weather condition. In this study, the heating load of a naturally ventilated broiler house was calculated using TRANSYS 15 BES program while internal climate and thermal condition were computed using Fluent 6.2. The computed resulted of the conventional ventilation system (A) and upgraded ventilation system (B) (Seo et al, 2007) were compared with each other for cold season. The results of the Building Energy Simulation(BES) indicated that the system B, the upgraded ventilation system made 8% lower total heating load and 47% lower at only the broiler zone compared to the conventional broiler house. Considering the entire broiler house, the existence of middle ceiling made the heating energy 11% lower required than without middle ceiling. Accordingly, the system B with middle ceiling was found to save heating energy by 20% in average. This study showed that the BES program can be a very powerful to effectively compute the energy loads of agricultural building while the energy load is very close related to ventilation efficiency.

축산 악취의 확산 예측을 위한 전산유체역학 모델의 개발

홍세운 ( Hong S. -w. ),이인복 ( Lee I. -b. ),황현섭 ( Hwang H. -s. ),( Jessie P. Bitog ),서일환 ( Yoo J. -i. ),유재인,권경석 ( Kwon K. -s. ),김용희 ( Kim Y. -h. ) 한국농공학회 2008 한국농공학회 학술대회초록집 Vol.2008 No.-

Odor is one of the major nuisances in the environment. In most countries, odor annoyance from livestock production is an increasing problem in the community. In order to reduce the odor inconvenience and establish a good relation between livestock industries and the surrounding communities, many studies on the odor dispersion, such as diffusion simulations and field experiments have been investigated. Computational Fluid Dynamics (CFD) has been effectively and widely used to study this kind of research. CFD considers both various wind conditions as well as topographical conditions to study aerodynamic phenomenon. Therefore, the ultimate objective of the study was to develop an aerodynamic model to predict qualitatively and quantitatively odor diffusion from livestock. In this study, various phenomena and factors of odor diffusion from livestock houses were investigated from field experiments during the first year of this 3-years study. Later, those data will be also used to verify the CFD accuracy as well as to develop 3-dimensional CFD model.

버블 칼럼 광생물반응기의 내부 유동분석을 위한 전산유체역학 시뮬레이션 모델의 이용

유재인,이인복,황현섭,홍세운,서일환,권경석,김용희,Yoo, J.I.,Lee, I.B.,Hwang, H.S.,Hong, S.W.,Seo, I.H.,Bitog, J.P.,Kwon, K.S.,Kim, Y.H. 한국농공학회 2009 한국농공학회논문집 Vol.51 No.5

Photobioreactor (PBR) 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 the culture volume and productivity while supplying optimum environmental conditions, various PBR structures and process control are needed to be investigated. In this study, computational fluid dynamics (CFD) was economically used to design a bubble-column type PBR taking 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 to realize bubbles were compared by theoretical approaches and comparing in a 2D simulation. As a result, the VOF (volume of fluid) model was found to be the most effective model to realize the bubbles shape as well as the flow inside PBR which may be induced by bubble injection. Considering the accuracy and economical efficiency, 0.005 second time step size was chosen for 2.5 mm mesh size. These results will be used as criteria for scale-up in the PBR simulation.

새만금 지역 간척지 및 인근 농경지에서의 비산 및 부유먼지의 지역별, 시기별 모니터링

황현섭,이인복,신명호,이광야,홍세운,서일환,유재인,권경석,김용희,Hwang, H.S.,Lee, I.B.,Shin, M.H.,Lee, G.Y.,Hong, S.W.,Seo, I.H.,Yoo, J.I.,Bitog, J.P.,Kwon, K.W.,Kim, Y.H. 한국농공학회 2009 한국농공학회논문집 Vol.51 No.5

A study on fugitive dusts was conducted at Saemangeum reclaimed land and the neighboring farm located at the west coast of Korea. After the area was completely reclaimed in 2006, halophyte plants and several windbreak systems were installed. The distributions of suspended dust particle was regularly measured through field experiment. The size of dust source area was also analyzed periodically and then it was determined to be in the following order: Buan > Gimje > Gunsan. The suspended dust which were dispersed to the neighboring areas were significantly affected by the size of the soil particles, wind velocity and wind direction. The results of Big Spring Number Eight (BSNE) experiments also showed that the concentration of the fugitive dust generated from the reclaimed land was reduced remarkably by the presence of halophyte plants. Recently, in 2008, the measured dust concentration rate was decreased by an average of 30.6%. The average dust concentration is expected to decrease further as more areas are being covered by halophyte plants.

축산 악취의 확산 모델 개발을 위한 현장 실험

홍세운,이인복,황현섭,서일환,권혁진,유재인,권경석,하태환,김용희,Hong, S.W.,Lee, I.B.,Hwang, H.S.,Seo, I.H.,Kwon, H.J.,Bitog, J.P.,Yoo, J.I.,Kwon, K.S.,Ha, T.H.,Kim, Y.H. 한국농공학회 2008 한국농공학회논문집 Vol.50 No.4

Odor is one of the major nuisances in the environment. In most countries, odor annoyance from livestock production is an increasing problem in community. In order to reduce the odor inconvenience and establish a good relation between livestock industries and the surrounding communities, many studies, such as diffusion simulations and field experiments, on the odor dispersion and its reduction have been investigated. These studies need to accompany the aerodynamic approach, as a main mechanism of diffusion phenomenon, and computational fluid dynamics(CFD) can be effectively used to study this kind of research. CFD considers both various wind conditions as well as topographical conditions to study aerodynamic phenomenon. Therefore the ultimate objective of the study was to develop an aerodynamic model to predict qualitatively and quantitatively odor diffusion from livestock. In this study, as the first step of this study, various phenomena and factors of odor diffusion from livestock houses were investigated through field experiments in 2007. Later, those data will be also used to verify the CFD accuracy as well as to develop 3-dimensional CFD model.

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.