• Title/Summary/Keyword: Mean velocity

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Development of Biological Filtration Process for Effective Nitrogen Removal in Tertiary Treatment of Sewage (생물막 여과반응기를 이용한 고도질소 제거법의 개발)

  • Jeong, Jin-Woo;Kim, Sung-Won;Tsuno, Hiroshi
    • Journal of Korean Society on Water Environment
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    • v.22 no.2
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    • pp.222-229
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    • 2006
  • The treatment performance and operational parameters of a tertiary wastewater treatment process a biological filtration system were investigated. The biological filtration system consisted of a nitrification filter (Fiter 1) and a polishing filter with anoxic and aerobic parts (Filter 2). SS, T-C-BOD, and T-N in effluent were kept stable at less than 3, 5 mg/L, and 5 mgN/L, respectively, under a HRT in Filter (filter-bed) of 0.37~2.3 h. T-N at the outlet of Filter 2 were about 1~5 mgN/L under the condition of LV of 50~202 m/d. In Filter 2, denitrification was accomplished under LV of 50~168 m/d in a 1 m filter-bed. However, the denitrification capacity reached the maximum when the linear velocity was increased to 202 m/d. Relationship between increase in microorganism and headloss was clearer in Filter 2. As a result, the denitrification rate increased from 1.0~2.3 kgN/($m^3-filter-bed{\cdot}d$) as the headloss increased. The COD removal rate was 6.0~9.6 kgCOD/($m^3-filter-bed{\cdot}d$) when operated with Filters 1 and 2. These results mean that captured bacteria contributed a part of COD consumption and denitrification. The maximum nitrification and denitrification rate was 0.5 and 4 kgN/($m^3-filter-bed{\cdot}d$) in Filter 1 and 2.The ratio of backwashing water to the treated water was about 5~10 %. In Filter 1, wasted sludge in backwashing was only 0.7~5.3 gSS/($m^3$-treated water). In Filter 2, added methanol was converted into sludge and its value was 8.0~24 gSS/($m^3$-treated water). These results proved that this process is both convenient to install as tertiary treatment and cost effective to build and operate.

The Effect of the Materials of an Outer Wall and the Paved Street on Human Thermal Comfort in a Housing Complex in Pohang City (포항시의 집합 주거공간에 있어서 외장재 및 도로 구성재료가 인체 온열 쾌적성에 미치는 영향)

  • Jeong, Chang-Won;Kim, Kyung-Dae;Choi, Young-Sik
    • Journal of the Korean Society of Industry Convergence
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    • v.4 no.3
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    • pp.319-327
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    • 2001
  • The objective of this study is to clarify the effect of thermal radiation environments on human thermal comfort, depending on different canyon types and surface materials on the human thermal comfort in a housing complex in Pohang city, Korea. For this purpose, the operative temperature and new effective temperature were calculated based on the modified mean radiant temperature of canyon models variated by the existence of direct radiation existence, surface materials, and the width and length of the street spaces in a housing complex. These indices for the canyon have been calculated from the meteorological data of Pohang city, which include air temperature, relative humidity, air velocity, global solar radiation and cloud. And the monthly averages of these climate factors measured at noon have been used. The results are as follows: (1) It is revealed that the short-wave radiosity reached the human body is affected by direct solar radiation and surface materials, and the long-wave radiosity by canyon types. (2) The existence of direct solar radiation, the kinds of surface materials and canyon types affect operative temperature($OT_n$) and new effective temperature($ET^*{_n}$). (3) The analysis of the human heat balance in the canyon indicates that the influence of radiation on human body is marc likely to be affected by the existence of direct solar radiation on human model.

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An Experimental Study on the Flow Around a Simplified 2-Dimensional Vehicle-Like body (단순화된 2차원 자동차형 물체주위의 유동에 관한 실험적 연구)

  • 유정열;김사량;강신형;백세진;이택시;김응서
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.13 no.1
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    • pp.178-189
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    • 1989
  • An experimental study has been performed to study the effect of the base slant angle of a 1/10 scale two-dimensional vehicle-like body on its wake flow including the recirculating region, where the simplified shape of the body has been originated from a profile of a domestic passenger car. In the case of a Reynolds number based on the length of the model R=7.96*10$^{5}$ , the surface pressure coefficient, the mean velocity and the turbulent stresses have been measured, while the flow visualization technique using wool tuft has been adopted as well. When the base slant angle of the model is 15.deg., the free stream flowing parallel to the slant is observed to be separated from the lower edge of the slant, thus forming the smallest recirculating region. When the base slant angles are 30.deg. and 45.deg., the free streams are separated from the upper edge of the slant and the sizes of the recirculating zones are observed to be almost the same as when the base slant angle is 0.deg. From these observations, it is conjectured that between the base slant angles of 15.deg. and 30.deg. there exists a critical angle at which the size of the recirculating region becomes minimum and as the slant angle becomes larger than this critical angle the separation line moves along the slant towards the rear edge of the roof. Through the flow visualization technique, the existence of the two counter-rotating bubbles in the recirculating region has been clearly observed and verified.

Determination of EMC and Unit Loading of Rainfall Runoff from Forestry-Crops Field (산림과 밭 지역 강우 유출수의 EMC 및 원단위 산정)

  • Won, Chul-hee;Choi, Yong-hun;Seo, Ji-yeon;Kim, Ki-cheol;Shin, Min-hwan;Choi, Joong-dae
    • Journal of Korean Society on Water Environment
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    • v.25 no.4
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    • pp.615-623
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    • 2009
  • The research of the determination of event mean concentration (EMC) was focussed combined sewer overflows and highway runoff in korea. But those of non-urban areas are few. In this study, EMC and unit loading on land use types in Nogok watershed were estimated by runoff loading of non-point source (NPS) on non-urban area. Two monitoring sites were equipped with an automatic velocity meter, flow meter, and water sampler. Monitoring was conducted at two monitering site during the rainy season. The results show that the EMC ranges in forest land use are 1.3~2.6 mg/L for BOD, 2.0~16.1 mg/L for SS, 0.1~2.1 mg/L for TN, and 0.12~0.49 mg/L for TP. The unit loading of NPS in this study was difficult to compare directly with that used conventionally because of the difference of field investigation. In near future, it needs to conduct more systematic and long-term research about NPS within the watershed. The results of this research can be used to estimate the total pollution load management system (TPLMS) program in korea.

Simultaneous Removal of NOx/SOx by Catalyst-loaded Cordierite Porous Filter (촉매 담지 코디어라이트 다공성 필터의 NOx/SOx 동시제거에 대한 연구)

  • Lee, Shi-Hee;Chung, Koo-Chun;Kim, Jee-Woong;Shin, Min-Chul;Lee, Hee-Soo
    • Analytical Science and Technology
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    • v.15 no.3
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    • pp.256-262
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    • 2002
  • After porous filters were manufactured using cordierite powder whose mean paricle size was 200${\mu}m$, they were loaded with catalysts such as $V_2O_5$, CuO and $LaCoO_3$ by vacuum impregnation method. And the NOx/SOx simultaneous removal efficiency was measured by passing NO and $SO_2$ through catalyst-loaded ceramic filters. The cordierite porous filters had the apparent porosity of 61.6%, the compressive strength of 12.3 MPa and the pressure drop of 147 pa at the face velocity of 5 cm/sec. According to the analysis of NO/$SO_2$ simultaneous removal efficiency, perovskite $LaCoO_3$ catalyst was the most efficient for the simultaneous NO and $SO_2$ removal. The $LaCoO_3$ catalyst-loaded filter could remove more than 90% for NO and more than 80% for $SO_2$.

The Characteristics of Elutriation with Gaussian Particle Size Distributions in a gas-solid fluidized bed (기-고 유동층에서 Gaussian 분포 입자군의 표준편차에 따른 유출 특성)

  • Jang, Hyun-Tae;Cha, Wang-Seog
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.10 no.11
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    • pp.3274-3279
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    • 2009
  • The elutriation characteristics of particle size distribution were investigated in a gas-solid fluidized bed. Experiments were carried out with the mulit-sized particles of Gaussian distributions. The elutriation rate constant obtained from the experiment was correlated with the standard deviation of particle size and the dimensionless group of the velocity ratio. The standard deviation of pressure fluctuation, mean pressure, major frequency and power spectrum density function were calculated by pressure fluctuation properties. Size distribution of elutriated particles and pressure fluctuations were measured for the particle size distribution of particle system depended largrly on the size distribution. Characteristics of fluidization and elutriation were greatly influenced by the particle size distribution and these characteristics could be interpreted with pressure fluctuation properties.

Estimation of FDS Prediction Performance on the Operation of Water-Mist (미세물분무 작동에 대한 FDS 예측 성능 평가)

  • Ko, Gwon Hyun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.15 no.8
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    • pp.4809-4814
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    • 2014
  • The aim of the present study was to estimate the prediction performance of a FDS (Fire Dynamic Simulator) to simulate the fire behaviors and suppression characteristics by operating a water-mist. Rosin-Rammler/log-normal distribution function was used to determine the initial droplet distribution of water-mist and the effects of its model constant were considered. In addition, the simulation models were validated by a comparison of the predicted fire suppression characteristics with water-mist injection pressures to the previous experiments, and the thermal flow behaviors and gaseous concentration variations were analyzed. The results showed that water-mists with the same mean diameter were affected by the characteristics of the droplet size distribution, which have different size and velocity distributions at the downstream location. The fire simulations conducted in this study determine the initial droplet size distribution tuned to the base of the spray characteristics measured by previous experiments. The simulation results showed good agreement with the previous measurements for temperature variations and fire suppression characteristics. In addition, it was confirmed that the FDS simulation with a water-mist operation supplies useful details on estimations of the thermal flow fields and gaseous concentration under water mist operation conditions.

Helical Instability Wave Excitation of Swirling Jets (스월제트에 관한 헬리컬 불안정파 자극)

  • Lee, Won-Joong;Taghavi, Ray-R.
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.33 no.1
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    • pp.48-53
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    • 2005
  • The purpose of this investigation is to explore the possibility of using artificial mechanical means for excitation of shear layers with application in swirling jet mixing enhancement. For this purpose, a mechanical excitation device was designed and fabricated. The major system components consist of two subsonic nozzles, one swirl generator, and the excitation device. The experiments were carried out at various helical excitation modes; i.e., m=+0, m=$\pm$1, m=$\pm$2, m=$\pm$3, and m=$\pm$4. Axial mean velocity measurements were made with plane and helical wave excitation using a hot-wire anemometer. The results are compared with the baseline (plane-wave excitation) at various helical modes. The acquired data is presented in 3-D mesh plots and 2-D contour plots. It was observed that new device was effective in excitation of the helical instability waves and resulting in mixing enhancement of the swirling jet.

The Production of TiCl4 from Titaniferrous Magnetite Slag by the Chlorination in a Fluidized Bed Reactor (함티탄자철광 Slag의 유동층 염소화에 의한 TiCl4의 제조)

  • Song, Ki-Young;Lee, Sang-Soon;Lee, Chul-Tae
    • Applied Chemistry for Engineering
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    • v.4 no.1
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    • pp.64-74
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    • 1993
  • The chlorination of the titanium slag from titaniferrous magnetite by the arc-smelting in a fluidized bed reactor was investigated to produce $TiCl_4$ from domestic titaniferrous magnetite. The optimum conditions are as follows : reaction temperature; $950^{\circ}C$, reaction time; 90min, $Cl_2$ gas velocity; 3cm/sec, and petroleum coke-to-titanium slag weight ratio; 0.18. Also the mean diameter of titanium slag and petroleum coke was $44.6{\mu}m$ and $67.9{\mu}m$ respectively. Under these conditions 97.07% of Ti component in the titanium slag was chlorinated and the purity of $TiCl_4$ from this chlorination was 96.2%.

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Evaluation of the maneuverability of a real ship with flap rudder (Flap rudder를 이용한 조종성능 평가)

  • AHN, Jang-Young;KIM, Kwang-il;KIM, Min-Son;LEE, Chang-Heon
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.56 no.2
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    • pp.172-182
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    • 2020
  • In order to offer specific information needed to assist in operation of a ship with same type rudder through evaluating the maneuverability of training ship A-Ra with flapped rudder, sea trials based full scale for turning test, zig-zag test with rudder angle 10° and 20°, and spiral test at service condition were carried out on starboard and port sides around Jeju Island according to the standards of maneuverability of IMO. As a result, the angular velocity of port turn was higher than that of starboard turn. Therefore, the size of turning circle was longer on the starboard side. In addition, variation of the transfer due to various factors was more stable than those of the others. In the Z-test results, the mean of 1st and 2nd overshoot angles were 9.8°, 6.3° and 15.3°, 9.2° respectively when the port and starboard was 10°; the 1st overshoot angle were 18°, 13.7° when using 20°. Her maneuverability index T' and K' can be easily determined by using a computer with the data obtained from Z-test where K' and T' are dimensionless constants representing turning ability and responsiveness to the helm, respectively. In the Z-test under flap rudder angle 10°, the obtained K' value covered the range of 2.37-2.87 and T' was 1.74-3.45. Under the flap rudder angle 20°, K' and T' value showed 1.43-1.63, 1.0-1.73, respectively. In the spiral test, the loop width was unstable at +0.3° and -0.5°-0.9° around the midship of flap rudder. As a result, course stability was comparatively good. From the sea trial results, training ship ARA met the present criterion in the standards of maneuverability of IMO.