• Journal of Environmental Health Sciences
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• v.21 no.4
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• pp.37-43
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• 1995

The course of biodegradation of anionic surfactants, Linear Alkylbenzene Sulfonates(LAS), Sodium Lauryl Ethoxylate Sulfonate(SLES), and Sodium Lauryl Sulfonates(SLS), which are mainly used to make detergents and shampoo, was investigated. The degree of biodegradation was studied as a function of concentration, volumetric flow rate, and temperature in Naktong River. MethyleneBlue Active Substances(MBAS), Total Dissolved Organic Carbon(TOC), and Chemical Oxygen Demand(COD) were measured to evaluate the degree of biodegradation. The degree of biodegradation of LAS was highly dependent upon the concentration and was increased as the concentration was decreased and that of SLES and SLS was almost constant at the concentration of less than 200 ppm, but was much increased as the volumetric flow rate was increased or the temperature was increased.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.6
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• pp.631-637
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• 2013

The characteristics of involute gear pump with eccentric gap between gear tip and housing have been studied in terms of volumetric flow rate and/or flow efficiency. The analysis has been done with FLUENT/R-13 employing with k-e model for the turbulent flow under the given conditions of rotational velocity, gap distance and outlet pressure. The effect of parameters continues to be shown for the eccentric gear as same as for the concentric gear such that the volumetric flow rate (volumetric efficiency) increases as the increases of rotational velocity and decrease of gap distance and of outlet pressure. In the meantime, the shape of pressure build-up appears to be exponentially increase as gap distance decreases at upstream position. The pressure is rapidly developing in the upstream and remains almost constant thereafter in the downstream of circumferential flow path. This typical characteristics becomes more profound as eccentricity increases. The pump performance for the eccentric gear pump with minimum gap distance shows better than its concentric counterpart. However, it shows not for the concentric pump with minimum gap distance. Therefore, the gap reduction due to eccentricity may be positive for pump performance.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.157-164
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• 2008

The temperature-entropy diagram of water or vapor displays graphically the thermophysical properties, so it is very conveniently used in various thermal systems. On general T-s chart of water, there are temperature, pressure, quality, specific volume, specific enthalpy, specific entropy. However, various state and process values besides above properties can be plotted on T-s diagram. In this study, we developed the software drawing twenty six kinds of properties, that is temperature, pressure, quality, specific volume, specific internal energy, specific enthalpy, specific entropy, specific exergy, exergy ratio, density, isobaric specific heat, isochoric specific heat, ratio of specific heat, coefficient of viscosity, kinematic coefficient of viscosity, thermal conductivity, prandtl number, ion product, static dielectric constant, isentropic exponent, velocity of sound, joule-thomson coefficient, pressure coefficient, volumetric coefficient of expansion, isentropic compressibility, and isothermal compressibility. Also, this software can analyze and print the system values of mass flow rate, volume flow rate, internal energy flow rate, enthalpy flow rate, entropy flow rate, exergy flow rate, heat flow rate, power output, power efficiency, and reversible work. Additionally, this software support the functions such as MS-Power Point.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.1
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• pp.61-69
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• 2015

The objective of this study is to experimentally investigate the mixed flow behaviors and oxygen transfer characteristics of a vertical orifice ejector. The experimental apparatus consisted of an electric motor-pump, an orifice ejector, a circulation water tank, an air compressor, a high speed camera unit and control or measurement accessories. The mass ratio was calculated using the measured primary flow rate and suction air flow rate with experimental parameters. The visualization images of vertically injected mixed jet issuing from the orifice ejector were qualitatively analyzed. The volumetric oxygen transfer coefficient was calculated using the measured dissolved oxygen concentration. At a constant primary flow rate, the mass ratio and oxygen transfer coefficient increase with the air pressure of compressor. At a constant air pressure of the compressor, the mass ratio decreases and the oxygen transfer coefficient increases as the primary flow rate increases. The residence time and dispersion of fine air bubbles and the penetration of mixed flow were found to be important parameters for the oxygen transfer rate owing to the contact area and time of two phases.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.6 no.1
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• pp.47-53
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• 1994

Cycle simulation of the air-conditioner was carried out using a number of candidate alternatives to R22;R32/R125/R134a(30/10/60, by mass percent), R32/R125/R134a(10/70/20), R32/R134a(25/75), R32/R134a(30/70), R32/R125(60/40), R290(propane) and R134a. In this study, we considered only the basic parts of the air-conditioner such as the compressor, the evaporator, the condenser and the capillary tube, for the purpose of analysis. The performance characteristics of alternatives considered here were examined by comparing with the case using R22 at the constant volumetric flow rate condition. The results of our analysis revealed that the use of refrigerant mixtures, R32/R134a(30/70) and R32/R125/R134a(30/10/60), was appropriate for the alternatives to R22 in view of the cooling capacity and the COP. For the case of using R134a and R290, the COP was observed to increase under the same volumetric flow rate condition, but the cooling capacity was substantially decreased. Therefore the use of R134a and R290 should be accompanied with increasing considerably the size of compressor in order to maintain the same cooling capacity of R22.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.11
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• pp.143-151
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• 1996

Structural reaction injection molding을 이용한 복합재료의 제품 셩형을 위한 모델링 전략을 설명하였다. 사용된 모델은 두 평행한 원판형 mold에 있는 불 균일한 온도조건의 fiber preform을 통과하는 reactive srsin의 방사형 유동을 시뮬레이션 한다. 이러한 모델은 중요한 작동인자와 공정인자(주입온도, mold의 온도, 유량, cavity의 두께와 섬유의 조밀도)등이 유동속도, 변화(monomer, radical, inhibitor) 및 온도분포 등에 미치는 영향을 예견한다. 열전달과 질량전달 및 화학반응을 고려하여 모델을 개발하였다. 중요한 공정인자를 평가하기 위한 효울적인 공정창( process window)을 제공하는데 본 연구의 목적을 두었다. 2차원적인 Lagrangian 방식에 1차원적인 유동과 제한적인 2차원 열전달을 가정하여 모델을 유도하였고, 방정식은 implicit difference scheme에 의해 전개하였다. 이 모델은 Gonzalez-Romero의 실험 결과와 비교함에 의해 확인되었고, 실험결과가 잘 일치함을 보였다.

• Journal of computational fluids engineering
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• v.20 no.3
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• pp.35-40
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• 2015

Centrifugal pumps consume considerable amounts of energy in various industrial applications. Therefore, improving the efficiency of pumps machine is a crucial challenge in industrial world. This paper presents numerical investigation of flow characteristics in volutes of centrifugal pumps in order to compare the energy consumption. A wide range of volumetric flow rate has been investigated for each case. The standard k-${\varepsilon}$ is adopted as the turbulence model. The impeller rotation is simulated employing the Multi Reference Frames(MRF) method. First, two different conventional design methods, i.e., the constant angular momentum(CAM) and the constant mean velocity (CMV) are studied and compared to a baseline volute model. The CAM volute profile is a logarithmic spiral. The CMV volute profile shape is an Archimedes spiral curve. The modified volute models show lower head value than baseline volute model, but in case of efficiency graph, CAM curve has higher values than others. Finally for this part, CAM curve is selected to be used in the simulation of different cross-section shape. Two different types of cross-section are generated. One is a simple rectangular shape, and the other one is fan shape. In terms of different cross-section shape, simple rectangular geometry generated higher head and efficiency. Overall, simulation results showed that the volute designed using constant angular momentum(CAM) method has higher characteristic performances than one by CMV volute.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.25 no.4
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• pp.301-306
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• 1992

In order to determine the optimal conditions for the process of acetic acid fermentation, the kinetics of Acetobacter aceti fermentation in submerged batch cultures were studied at different agitation speeds and air flow rates. The maximum cell concentration was noted after about 48 hr fermentation and the time course of Acetobactey aceti fermentation showed a distinct feature of growth-associated product formation. At agitation speeds 700, 500, and 300 rpm fixed on air flow rate 1 v/v/M, specific grow rates were $3.97\times10^{-2},\;3.82\times10^{-2},\;and\;2.04\times10^{-2\} \;hr^{-1}$, saturation constants were 61.4, 64.6, and 69.4mg/ml. and volumetric oxygen transfer coefficients were 0.9337, 0.4468, and 0.1701 $min^{-1},$ respectively. At air flow rates 1.25, 1.00, and 0.75 v/v/M fixed on agitation speed 500 rpm, specific growth rates were $3.90\times10^{-2},\;3.82\times10^{-2},\;and\;2.37\times10^{-2}\;hr^{-1}$, saturation constants were 63.4, 64.6, and 64.9 mg/ml, and volumetric oxygen transfer coefficient were 0.4923, 0.4468, and 0.3509 $min^{-1},$ respectively.

• Journal of environmental and Sanitary engineering
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• v.13 no.1
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• pp.91-103
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• 1998

Design data for COD and nitrogen removal from wastewater were collected from Pilot's Multi-stage Bio-reactor. Hyraulic conditions and pollutant loadings were varied in order to optimize the biological and operational parameters. Pilot's experimental results summarize as followings. 1. T-N removal efficiency in the organic volumetric loading 0.2 kgCOD/m$^{3}$·d was obtained as maxium of 85% at internal recycle ratio 2.5 and in more ratio than this it was decreased. Organic removal efficiency was about 91% under the overall experimental conditions and not influenced by recycle ratio.. 2. Nitrification reaction was shown as maxium in the SCOD$_{cr}$/NH$^{+}$-N ratio of 6.5 and in more ratio than this it was decreased. Denitrification rate was the maxium as 85% in more than 7.5 of SCOD$_{cr}$/NO$_{x}$-N ratio and in the ratio over this ratio it becomes constant. 3. By utilizing an applied new model of Stover-Kincannon from Monod's kinetic model, concentration of T-N in the effluent according to flow quanity in the influent was estimated as 8.74 and -67.5 respectively. The formula for estimating T-N concentration of effluent was obtained like this: N$_e$=N$_0$(1- $\frac{8.74}{(QN$_0$/A)-67.05}$)

• International Journal of Automotive Technology
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• v.8 no.2
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• pp.165-177
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• 2007

Predictions of diesel particulate filtration are typically made by modeling of a particle collection, and providing particle trapping levels in terms of a pressure drop. In the present study, a series of single channel diesel particulate filter (DPF) experiments are conducted, the pressure traces are inversely analyzed and essential filtration parameters are deducted for model closure. A DPF filtration model is formulated with a non-linear description of soot cake regression. Dependence of soot cake porosity, packing density, permeability, and soot density in filter walls on convective-diffusive particle transportation is examined. Sensitivity analysis was conducted on model parameters, relevant to the mode of transition. Soot cake porosity and soot packing density show low degrees of dispersion with respect to the Peclet number and have asymptotes at 0.97 and $70\;kg/m^3$, respectively, at high Peclet number. Soot density in the filter wall, which is inversely proportional to filter wall Peclet number, controls the filtration mode transition but exerts no influence on termination pressure drop. The percolation constant greatly alters the extent of pressure drop, but is insensitive to volumetric flow rate or temperature of exhaust gas at fixed operation mode.