• Asian Journal of Atmospheric Environment
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• v.10 no.2
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• pp.57-66
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• 2016

Wet deposition fluxes of ions at a coastal site in southwestern Japan in the period 1996-2003 were investigated to quantify the respective contributions of cyclone-, stationary front- and typhoon-associated rains. On average, the deposition fluxes of terrigenous-origin ions, nss-$SO_4{^{2-}}$, $NO_3{^-}$, $NH_4{^+}$ and nss-$Ca^{2+}$ were $37.6{\pm}7.3$, $16.3{\pm}4.2$, $19.0{\pm}3.4$ and $9.6{\pm}4.8meq\;m^{-2}yr^{-1}$, and those of $Na^+$ and $Cl^-$, the major ions in sea water, were $97.0{\pm}38.2$ and $115.2{\pm}48.2meq\;m^{-2}yr^{-1}$, respectively. Cyclone-associated rain constituted more than 50% of the fluxes of the terrigenous ions in almost all years. Stationary front-associated rain also contributed significantly, although the contribution was lower than the contribution by Cyclone-associated rain in almost all years. In particular, the wet deposition flux of nitrogen compounds of $NO_3{^-}$ and $NH_4{^+}$, which are important nutrients for micro-bioactivities in sea surface water, was dominated by cyclone-associated rain. Due to the extreme abundance of $Na^+$ and $Cl^-$ in the rainwater of typhoons, the fluxes of $Na^+$ and $Cl^-$ were contributed substantially by typhoons in years with typhoons' passage although cyclones were still the largest contributor to the fluxes. These results indicate the dominance of cyclones in the wet deposition to the East China Sea areas and the necessity to take rain types into account for a more accurate elucidation of the temporal and spatial variation of the wet deposition.

• Particle and aerosol research
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• v.12 no.4
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• pp.115-126
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• 2016

Numerical analysis was done to evaluate the movement of the particles and the fluid inside of the cyclone-bag hybrid dust collector. Flow discharged from the cyclone in the hybrid particle collector has swirl pattern, and it results in the biased flow to the bag filters and deteriorates the collection performance of the bag filter. The current study is to evaluate the effect of the duct lengths and the baffle arrays in the connection duct by the computational methods. Main concerns of the analysis are how to improve the uniformity of the internal flow between the cyclone and the bag filter. Numerical analysis was done to check the particle removal efficiencies of the system with respect to the flow characteristics which is expressed in RMS values of the upward flow inside of the connection duct. The flow pattern inside of the connection duct is evaluated under different the duct lengths and the baffle arrays. In case of the reference geometry the RMS value of inside flow was 56.7%, and the value was decreased to 30.1% by controlling the lengths of duct. The effects of baffle was also evaluated, the RMS value of flow could be decreased 55.2% and so on. But the pressure drop across the baffles becomes high and the system efficiency becomes lower.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.4 no.3
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• pp.217-226
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• 2006

The structural and contamination characteristics of hot cells at KAERI were investigated. The SEM results showed that the size of the hot particulate on the inner surface of the hot cell ranged from 0.2 to $10{\mu}m$. It was found that an inlet flow rate of 15 m/sec was suitable for this developed cyclone with a 49 mm optimum vortex finder length. The results showed that the collection efficiency was about 85% for $3{\mu}m$ particles. The collection efficiency didn't show a sharp increase when the inlet flow rate was faster than 15m/sec. When the temperature of the inlet flow gas was increased, the collection efficiency of the cyclone was slightly decreased. The larger the vortex finder length was, the higher the pressure drop in the cyclone was. The cut size diameter decreased with an increment of the Reynolds number. It was established that the flow in the cyclone was a turbulent flow on the basis of the Reynolds number and this turbulent flow caused a pressure drop in the cyclone. $Stk^{1/2}_{50}$ decreased with increasing values of the Reynolds number and it gradually approached a constant value at a higher value of the Reynolds number Namely, $Stk^{1/2}_{50}$ approached approximately 0.045 between 6000 and 8000 of the Reynolds number.

• Wind and Structures
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• v.19 no.5
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• pp.467-480
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• 2014

The estimation of wind speed values used in codes and standards is an integral part of the wind load evaluation process. In a number of codes and standards, wind speeds outside of tropical cyclone prone regions are estimated using a single probability distribution developed from observed wind speed data, with no distinction made between the types of causal wind hazard (e.g., thunderstorm). Non-tropical cyclone wind hazards (i.e., thunderstorm, non-thunderstorm) have been shown to possess different probability distributions and estimation of non-tropical cyclone wind speeds based on a single probability distribution has been shown to underestimate wind speeds. Current treatment of non-tropical cyclone wind hazards in worldwide codes and standards is touched upon in this work. Meteorological data is available at a considerable number of United States (U.S.) stations that have information on wind speed as well as the type of causal wind hazard. In this paper, probability distributions are fit to distinct storm types (i.e., thunderstorm and non-thunderstorm) and the results of these distributions are compared to fitting a single probability distribution to all data regardless of storm type (i.e., co-mingled). Distributions fitted to data separated by storm type and co-mingled data will also be compared to a derived (i.e., "mixed") probability distribution considering multiple storm types independently. This paper will analyze two extreme value distributions (e.g., Gumbel, generalized Pareto). It is shown that mixed probability distribution, on average, is a more conservative measure for extreme wind speed estimation. Using a mixed distribution is especially conservative in situations where a given wind speed value for either storm type has a similar probability of occurrence, and/or when a less frequent storm type produces the highest overall wind speeds. U.S. areas prone to multiple non-tropical cyclone wind hazards are identified.

• Particle and aerosol research
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• v.5 no.2
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• pp.37-43
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• 2009

Particulate matter (PM) is one of the major indoor air pollutants especially in the subway station in Korea. In order to remove PM in the subway station, several kinds of PM removal system such as roll-filter, auto-washable air filter, demister, and electrostatic precipitator are used in the air handling unit (AHU) of subway stations. However, those systems are prone to operation and maintenance problems since the filter-regeneration unit consisting of electrical or water jet parts might malfunction due to the high load of particulates unless the filter medium is periodically replaced. In this study, the use of axial-flow cyclone was proposed for particulate filter unit in the AHU for its low operation and maintenance cost. Novel shape of axial-flow cyclone was designed by using computational fluid dynamics (CFD). The shape of vortex vane was optimized in terms of pressure drop and tangential velocity. In addition, CFD analysis was validated experimentally through the pressure drop measurement of mock-up model. We found that pressure drop and tangential velocity of fluid through the axia-flow cyclone was significantly affected by the rotating degree of vortex vane and the numerical prediction of pressure drop agreed well with experimental measurement.

• Journal of Environmental Science International
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• v.16 no.11
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• pp.1225-1230
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• 2007

The emissions characteristics of particulate matters(PM) according to the types of wastes from industrial waste incinerator of 800 kg/hr treatment capacity were investigated. For this study, the incinerate waste are as follows; waste resin, waste wood, waste urethane, waste gunny, and waste paper. The particulate samples were collected to be emitted in stack and air pollution control(both cyclone and bag filter). In stack, the concentrations of PM were in the range of 2.61 to $26.51 mg/Sm^3$ and the major chemical species were C, Si, Cl, K, Na, Ca in all the wastes. In cyclone fly ash, the mean content of heavy metal were in the order of Fe > Zn > Pb > Cu > Mn > Cr > Ni > Cd > As > Hg and the heavy metal content of waste resin were Zn 34,197.5 mg/kg, Fe 27,587.6 mg/kg, Pb 6,055.8 mg/kg, respectively. In bag filter fly ash, the mean content of heavy metal were in the order of Zn > Pb > Fe > Cu > Mn > Cd > Cr > Ni > As > Hg and the heavy metal content of waste wood were Pb 36,405.2 mg/kg, Fe 15,762.9 mg/kg, Cu 9,989.5 mg/kg, Cd 2,230.1 mg/kg, respectively. Comparing the heavy metal content of both cyclone and bag filter, in cyclone, the Cr, Fe, Ni content were higher than in bag filter and the Cd, Cu, Hg content were lower than in bag filter.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2008.11a
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• pp.262-267
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• 2008

The domestic construction market started to expand steadily since 1970s. The building market which utilizes a sandwich panel with advantages of economical construction expenses and convenient construction has grown rapidly in recent years. However, the companies which specialize in constructing sandwich panels are relatively small or medium size, compared with other construction companies. As a result, studies on the improvement of productivity have not been conducted sufficiently. In this study, the construction sites of sandwich panel are investigated, and the work processes by each team are analyzed. Additionally, the productivity and the construction cost of each construction team are analyzed by constructing a model using the Web-Cyclone. It is expected that the results of this study can be applied to estimate the productivity and the construction cost of a sandwich panel construction that is appropriate for the on-site characteristics of small and medium sized construction companies in Korea. Also, similar processes can be simulated based on the modeling constructed in this study.

• Particle and aerosol research
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• v.15 no.4
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• pp.139-148
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• 2019

This study was performed for the application of a high-speed centrifugal cyclone to shale gas mining process. This device uses the centrifugal force to control particles similar to typical cyclones, and the disk located inside the cyclone is forced to rotate using a motor. The pressure difference occurred during the rotating of disk. Hence, inflow rate was generated without a blower fan. In addition, flow rate increased with elevating rpm of motor. The installing the disk in multiple stages on the inner rotor increased the instantaneous disk outlet flow. Hence, the control efficiency of oil particle increased from 1.05% to 31.2%. By modifying the structure of the disk so that the air flow to the opposite direction of the cyclone, the control efficiency of oil particles increased to 81.5%. By increasing the capacity of the motor and the size of the disk, the flow rate was increased to 2.5 ㎥/min because the rpm of motor and pressure difference increased. As rpm of motor increased, the cut-off diameter (d_pc) became smaller. Unlike the Lapple's equation, d_pc was inversely proportional to the effective number of rotations (N_e). The control efficiency was maintained even if the concentration of oil particles increased, for this reason, the higher the oil concentration, the more particles were accumulated and controlled.

• Atmosphere
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• v.23 no.1
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• pp.1-11
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• 2013

The angular momentum transport of an idealized axisymmetric vortex in the developing stage was investigated using the Weather Research and Forecast (WRF) model. The balanced axisymmetric vortex was constructed based on an empirical function for tangential wind, and the temperature, geopotential, and surface pressure were obtained from the balanced equation. The numerical simulation was carried out for 6 days on the f-plane with the Sea Surface Temperature (SST) set as constant. The weak vortex at initial time was intensified with time, and reached the strength of tropical cyclone in a couple of days. The Absolute Angular Momentum (AAM) was transported along with the secondary circulation of the vortex. Total AAM integrated over a cylinder of radius of 2000 km decreased with simulation time, but total kinetic energy increased rapidly. From the budget analysis, it was found that the surface friction is mainly responsible for the decrease of total AAM. Also, contribution of the surface friction to the AAM loss was about 90% while that of horizontal advection was as small as 8%. The trajectory of neutral numerical tracers following the secondary circulation was presented for the Lagrangian viewpoint of the transports of absolute angular momentum. From the analysis using the trajectory of tracers it was found that the air parcel was under the influence of the surface friction continuously until it leaves the boundary layer near the core. Then the air parcel with reduced amount of angular momentum compared to its original amount was transported from boundary layer to upper level of the vortex and contributed to form the anti-cyclone. These results suggest that the tropical cyclone loses angular momentum as it develops, which is due to the dissipation of angular momentum by the surface friction.

• Clean Technology
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• v.20 no.3
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• pp.263-268
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• 2014

Using the CFD method, the pressure drop in 6 cyclone dust collectors of different shape were calculated. And the results were compared with results of the conventional theories. Equations of Shepherd and Lapple (1939, 1940), First (1950), Alexander (1949), Stairmand (1949), Barth (1956) were used in the theoretical calculation. In CFD calculations, we used standard k-epsilon model for analysis of turbulent flow, fluid is $25^{\circ}C$ air, the velocity at inlet is 10 m/s and the temperature is $25^{\circ}C$. In CFD analysis results, the pressure distributions along the flow showed similar patterns in different cyclone shapes. But the pressure drop distributions estimated on the conventional theories had big difference in different cyclone shapes. Only First's theory and CFD analysis showed similar results.