• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.193-198
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• 2004

In general, the function of intake structure, whether it be a open channel, a fully wetted tunnel, a sump or a tank is to supply an evenly distributed flow to a pump station. An even distribution of flow, characterized by strong local flow, can result in formation of surface or submerged vortices, and with certain low values of submergence, my introduce air into pun, causing a reduction of capacity and efficiency, an increase in vibration and additional noise. This study investigated experimentally the formation of the vortex to understand the mechanism of vortex formation and to prevent the formation of vortex in the sump model using by the model test and PIV tool. Sump model was manufactured to 1/8 scale with the drawing of W intake pumping station. from the results of model test and PIV, the vortex were occurred the in the whole section. Thus, sump model tests with the anti-vortex device might be considered to prevent the formation of vortex in the sump model.

• Microbiology and Biotechnology Letters
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• v.35 no.3
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• pp.226-230
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• 2007

In order to achieve high-level expression of interferon-${\alpha}1$ (IFN-${\alpha}1$) during fed-batch fermentation of recombinant E. coli, effects of oxygen supply and induction temperature on the expression of recombinant proteins were evaluated. Supplementation of oxygen and its transfer into cells is one of the most important parameters involved in the design and operation of mixing-sparging equipment for bioreactors. Generally, higher oxygen supply stimulates cell growth of aerobic microorganism and consequently the amount of products is increased. In this study, the optimum aeration strategy for the higher production of IFN-${\alpha}1$ during fed-batch fermentation of recombinant E. coli was surveyed. The growth of the cells was also monitored with four different concentrations of dissolved oxygen (DO; limiting, 20%, 35%, 50%) conditions. The DO was controlled by varying aeration rates of air and pure oxygen. Oxygen uptake rate (OUR) and specific oxygen uptake rate (SOUR) were evaluated and compared for the enhanced growth and induction of the cells and IFN-${\alpha}1$, respectively. We confirmed that increased DO by additional oxygen supply, up to 35%, can improve the production of IFN-${\alpha}1$ during the fermentation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.8
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• pp.781-787
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• 2011

We design a four-stage propane-refrigerant centrifugal compressor for an LNG plant. Using a commercial code, we aerodynamically designed the compressor at each design point of the corresponding stages. We estimated the one-dimensional aerodynamic design output and the three-dimensional shape of the impeller flow passage via three-dimensional flow analysis. In particular, we discuss in detail the flow characteristics of the impeller and the vaneless diffuser passages of the fourth-stage compressor in terms of the velocity fields, the pressure, and the entropy distributions of the flow passages. We include the flow effects of the tip clearance flow, because at this stage the rotating speed and total inlet pressure are higher than those at the other compressor stages are. We carried out performance tests of the designed compressor stages using propane as a refrigerant in the LNG cycle. The practical evaluation could lead to design enhancements in the future.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.3
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• pp.288-294
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• 2005

This study was conducted to evaluate the grit removal efficiency of tornado block-type vortex grit separator. Vortex grit separator was manufactured for this study, and it was characterized by the impeller and tornado block installed in separator. Impeller was installed to increase water velocity in the separator and tornado block was installed to increase the grit lifting efficiency. Pilot study was also conducted in A sewage treatment plant (STP) in Gyeonggi province from November 2003 to May 2004 (64 days). Major findings are as follows. 1. Impeller was proven to increase water velocity in the grit separator, especially in low flow rate. This influence will increase separation ratio of organics from grits, preventing those organics from sedimentation. 2. Sand (with 0.2~0.3mm size) removal efficiency was over 98 % and 96 %, at the flow rate of $500m^3/day$ and $750m^3/day$ under the condition that impeller rotation velocity kept at 15 rpm. Originally that grit separator was designed to have the capacity of $500m^3/day$. $750m^3/day$ was tried to investigate the performance of this type of grit separator under overload condition. Stable grit removal was still available to the extent of 150% of designed capacity. 3. It took less than 3 minutes for the grit separator to completely lift out 3 kgs of 0.2-0.3 mm sized, settled sand at the bottom to 2,060 mm high above water surface. But it showed the tendency to spend a little more time on lifting the grit as the grit size and the vertical height of the lift increased. 4. During experimental duration in A STP, it was found that the average amount of inlet grit was about 981 g/day (160~1,685 g/day) under $500m^3/day$ of operation condition, but it varied so severely during the experimental duration. After classification of discharged grit according to its size, grit with 0.3-0.42 mm size was found as largest part of output.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.12
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• pp.192-199
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• 2020

The blower erosion phenomenon was investigated to develop a long-life blower with a volume flow rate of 10,000 ㎥/min with the required total pressure efficiency of 83% or more. The blower performance and blower erosion were predicted through numerical analysis by computational fluid dynamics(CFD). The conditions used for numerical analysis were an air volume of 16,200 ㎥/min, a rotation speed of 893 rpm, and a temperature of 330℃. The specific gravity, particle size, and amount of the dust was 3.15, 90 ㎛~212 ㎛, and is 265 kg/min, respectively. To examine the effects of a dust deflector on erosion, erosion analysis was performed by comparing the models with and without a dust deflector. Numerical analysis showed that when the dust deflector is installed, the average tended to decrease by 167% in the impeller and 133% in the boss. CFD using the Finne's model for erosion revealed a parallel restitution coefficient of 1 and a perpendicular restitution coefficient of 0.1. The blower performance of case 5 was 691.7 mmAq, and the efficiency was 83.3% when the rotation speed and the air volume flow rate were 880 rpm and 16,200 ㎥/min, respectively.

• Clean Technology
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• v.27 no.1
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• pp.39-46
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• 2021

A road structure washing vehicle equipped with a 4 HP, 80 LPM ultrafine bubble generator was used to clean a tunnel wall and the surface of the surrounding structure, consisting of concrete and tiles, in a heavy traffic area around an apartment complex in the city. Ultrafine bubbles were generated by supplying air at 2 to 3 LPM and using a specially designed nozzle, whereas fine bubbles made by an impeller in a gas-liquid mixing self-priming pump were produced with an average diameter of 165.4 nm and 6.81 × 107 particles mL-1. Using a high pressure washer gun that can perform high-pressure cleaning at 150 bar and 30 LPM, ultrafine bubbles were used to wash dust adsorbed on the surface of the road structures. The experimental analysis was divided into before and after washing. The samples were analyzed by applying ISO 8502-3 to measure surface contamination of dust adsorbed on the surface. Using the transparent tape attached to the surface, the removal rate was calculated by measuring the weight of the dust, and the number of particles was calculated using the gravimetric method and the software, ImageJ. The results of the experiment showed that the number of dust particles adsorbed on the tile wall surface before and after washing were 3,063 ± 218 particles mL-1 and 20 ± 5 particles mL-1, respectively, with weights of 580 ± 82 mg and 13 ± 4 mg. Particles on the surface of the concrete structure before and after washing were 8,105 ± 1,738 particles mL-1 and 39 ± 6 particles mL-1, respectively, with weights of 1,448 ± 190 mg and 118 ± 32 mg.

• Journal of the Korea Organic Resources Recycling Association
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• v.25 no.4
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• pp.41-50
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• 2017

The design of proper agitation system is requisite in biological waste treatment and energy generation plant, which is affected by viscosity, impeller types, and power consumption. In the present work, hydrogen fermentation of food waste was conducted at various operational pHs (4.5~6.5) and substrate concentrations (10~50 g Carbo. COD/L), and the viscosity of fermented broth was analyzed. The $H_2$ yield significantly varied from 0.51 to $1.77mol\;H_2/mol\;hexose_{added}$ depending on the pH value, where the highest performance was achieved at pH 5.5. The viscosity gradually dropped with shear rate increase, indicating a shear thinning property. With the disintegration of carbohydrate, the viscosity dropped after fermentation, but it did not change depending on the operational pH. At the same pH level, the $H_2$ yield was not affected much, ranging $1.40{\sim}1.86mol\;H_2/mol\;hexose_{added}$ at 10~50 g Carbo. COD/L. The zero viscosity and infinite viscosity of fermented broth increased with substrate concentrations, from 10.4 to $346.2mPa{\cdot}s$, and from 1.7 to $5.3mPa{\cdot}s$, respectively. There was little difference in the viscosity value of fermented broth at 10 and 20 g Carbo. COD/L. As a result of designing the agitation intensity based on the experimental results, it is expected that the agitation intensity can be reduced during hydrogen fermentation. The initial and final agitation intensity of 30 g Carbo. COD/L in hydrogen fermentation were 26.0 and 10.0 rpm, respectively. As fermentation went on, the viscosity gradually decreased, indicating that the power consumption for agitation of food waste can be reduced.

• Korean Chemical Engineering Research
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• v.51 no.5
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• pp.609-614
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• 2013

This study investigated the spontaneous combustion behavior of solvent-treated low rank coals. Indonesian lignite (a KBB and SM coal) and sub-bituminous (a Roto coal) were mixed with non-polar 1-methyl naphthalene (1MN) either by mechanical agitation or ultrasonication. The property change associated with 1MN treatment was then analyzed using proximate analysis, calorific value analysis, Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy and moisture re-adsorption test. Susceptibility to spontaneous combustion was evaluated using crossingpoint temperature (CPT) measurement along with gas analysis by GC. A FT-IR profile showed that oxygen functional groups and C-H bonding became weaker when treated by 1 MN. XPS results also indicated a decrease of the oxygen groups (C-O-, C=O and COO-). Increased hydrophobicity was found in the 1MN treated coals during moisture readsorption test. A CPT of the treated coals was ${\sim}20^{\circ}C$ higher than that of the corresponding raw coals and the ultrasonication was more effective way to enhance the stability against spontaneous combustion than the agitation. In the gas analysis less CO and $CO_2$ were emitted from 1MN treated coals, also indicating inhibition of pyrophoric behavior. The surface functional groups participating in the oxidation reaction seemed to be removed by the ultrasonication more effectively than by the simple mechanical agitation.

• Food Science and Preservation
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• v.31 no.3
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• pp.423-432
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• 2024

In this study, a vacuum tumbler with 4 impellers (DVT) was designed and applied for thawing frozen pork (vacuum -60 kPa, jacket 35℃, 1 rpm). Quality characteristics of the thawed pork were compared with those of industrially thawed meat by natural air at room temperature (NAT) and imported vacuum tumbler (IVT). The thawing time for frozen pork (303.36 kg) using DVT (165 min) was much shorter than that of NAT (4,200 min). DVT-thawed pork had lower drip loss (0.85%) than NAT (2.08%). DVT-thawed pork showed a pH of 5.92, a total bacterial count of 1.96±0.02 log CFU/g and no coliforms. Deteriorations in fat (TBARS 0.31±0.01 MDA mg/kg) and protein (VBN 5.67±1.98 mg%) in DVT-thawed pork were significantly lower than those of NAT (p<0.05). DVT-thawed pork had a high water-holding capacity (WHC, 97.5%). The hardness (34.59±0.46 N) and chewiness (188.21±0.17) of cooked DVT-thawed pork were about 5-6 times lower than those of NTA. Microstructure (SEM) showed myofibrillar damage in NAT-thawed pork, whereas dense myofibrillar structure was observed in DVT-thawed pork. DVT was better or similar to IVT in all evaluation parameters. The designed DVT is expected to be used as an efficient thawing method in terms of processing time and yield and to produce thawed meat with high WHC, soft texture, and low spoilage by minimizing tissue damage.