십자형 막분리 공정에서 전처리 응집공정의 적용성 평가

정철우,손희종,배상대 한국수처리학회 2008 한국수처리학회지 Vol.16 No.1

The objectives of this research are to evaluate the performance of a combined process coagulation-cross flow UF (Ultrafiltration) system for water treatment, and find out the design parameters of the combined process for water treatment and the effect of cross flow velocity, pressure, organic concentration and to find out the optimum conditions of the combined process for water treatment. For cross flow system, the permeate flux increased with increasing cross flow velocity, but remained constant beyond a certain value. When coagulation was applied for the pretreatment of UF, cross flow velocity did not affect the permeate flux. Applying coagulation process before cross-flow UF also significantly improved the permeate flux regardless of membrane materials.

횡류팬 유로최적화를 위한 수치실험

전용두,이종수 공주대학교 생산기술연구소 2002 論文集 Vol.10 No.-

Cross flow fan system is widely used for various applications, especially for the air-moving device of heaters, air-conditioners, and air-curtains. Although there are efforts for the optimization of cross-flow fan flow path with different methods of approach, it is still being investigated by many researchers through experimentally and/or theoretically, because the flow pattern of the cross flow fan is not stereotyped. This paper presents some results from numerical experiments for optimization of the flow path through a cross-flow fan to be applied to indoor wall-mounted room heater. Two dimensional analysis has been applied to a specific fan system including inlet and diffuser outlet. Flow characteristics are presented and discussed for two different flow path at three different operating conditions represented by rotational speed(800, 1,000, 1,200 rpm) of the fan. According to the simulated results for the specific fan system under consideration, it could be found that the flow pattern resembles each other at different rotational speed (to say from 800 rpm to 1,200 rpm) for a fixed flow path, while the secondary flows mostly absorbs the speed effects. By changing the flow path significant increase in volume flow rate is estimated upto 2.65 at the same rotational speed. According to the present experience, fan flow path design can be performed more efficiently by incorporating this type of numerical experiments combined with the model tests.

An Experimental Study for Noise Reduction of the Cross-Flow Fan of the Room Air-Conditioners

Koo, Hyoung-Mo The Society of Air-Conditioning and Refrigerating 2000 International Journal Of Air-Conditioning and Refr Vol.8 No.2

Present study explains some experimental results on the aerodynamic noise of the cross-flow fan usually installed in the indoor unit of the room air-conditioners and provides a simple reduction method of radiating sound to decrease the total noise level. The spectra of the noise of the cross-flow fan were analyzed by the spectral decomposition method to characterize the generated sound. The unsteady fluctuating flow field was also measured using the I-type hot-wire probe. Comparing the spectral characteristics of the sound and the flow velocity, a useful noise reduction method was proposed, which bounds the region with a fence where the flow fluctuations were noticeably changed in the same fashion as the source spectral distribution functions vary. To validate the proposed method for reducing noise generated by the cross-flow fan, the sound pressure levels of the cross-flow fan system were compared with and without the bounding fence for various flow rates.

Mechanism analysis on fluidelastic instability of tube bundles in considering of cross-flow effects

Jiang Lai,Lei Sun,Lixia Gao,Pengzhou Li 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.1

Fluidelastic instability is a key issue in steam generator tube bundles subjected in cross-flow. With a lowflow velocity, a large amplitude vibration of the tube observed by many researchers. However, themechanism of this vibration is seldom analyzed. In this paper, the mechanism of cross-flow effects onfluidelastic instability of tube bundles was investigated. Analysis reveals that when the system reachesthe critical state, there would be two forms, with two critical velocities, and thus two expressions for thecritical velocities were obtained. Fluidelastic instability experiment and numerical analysis were conductedto obtain the critical velocity. And, if system damping is small, with increases of the flow velocity,the stability behavior of tube array changes. At a certain flow velocity, the stability of tube array reachesthe first critical state, a dynamic bifurcation occurs. The tube array returns to a stable state with continuesto increase the flow velocity. At another certain flow velocity, the stability of tube array reachesthe second critical state, another dynamic bifurcation occurs. However, if system damping is big, there isonly one critical state with increases the flow velocity. Compared the results of experiments to numericalanalysis, it shows a good agreement.

음식물 침출수를 처리하는 막결합 고온혐기성 소화시스템에서 교차여과와 막간압력이 파울링에 미치는 영향

Youngo Kim,Dukwoo Jun,Seongkyu Yoon,Chunghee Chang,Jaeho Bae,Kwansun Yoo,Jeonghwan Kim 한국막학회 2011 멤브레인 Vol.21 No.4

음식물 폐기물 침출수를 처리하는 분리막 결합 고온 혐기성소화공정(생물학적 반응조) (Anaeorobic Membrane Bioreactor, AnMBR)의 파일럿 운전에서 분리막의 교차여과 속도와 막간압력이 파울링에 미치는 영향을 관찰하였다. 연구 결과 정압여과 하에서 교차여과 속도가 증가할수록 파울링의 속도는 현격히 감소되었다. 그러나 이와 같은 영향은 낮은 막간압력에서 더욱 효과적이었다. 막간압력이 증가할수록 여과대상 물질의 압축성으로 인해 투과성이 상대적으로 낮은 파울링층(혹은 케익층)이 분리막 표면에 형성된 것에 기인된 듯하다. 여과대상 시료의 입도분석을 해 본 결과 입자크기는 약 10~100mum 범위에서 분포하였고 이에 따라 브라운확산에 의한 역수송보다 분리막 표면에서 교차여과에 의해 발생하는 전단력이 입자의 역수송에 더욱 기여하고 있음을 예측할 수 있었으며 이는 AnMBR의 연속운전을 통해 재확인할 수 있었다. 운전 후 막 부검을 실시한 결과 유기 및 무기 파울링이 모두 관찰되었으나 어느 것이 지배적인 파울링 기작을 나타내는지는 앞으로 더욱 연구가 필요하다. 무기 파울링의 경우 대부분 분리막 표면에서 스케일링 형성이 지배적이었으며, 따라서 분리막의 공극 막힘에 주로 기여하는 작은 콜로이드성 유기물질의 경우 분리막 표면에서 전단력에 의한 역수송 효과는 그다지 크지 않을 것으로 사료된다. The effect of cross-flow velocity and transmembrane pressure (TMP) on membrane fouling was observed from pilot-scale operation of thermophilic anaerobic membrane bioreactor (AnMBR) treating food waste leachate. It was found that fouling rate was reduced significantly as cross-flow velocity increased at constant TMP mode of operation while this effectiveness was more pronounced at lower TMP. Higher TMP resulted in less permeable fouling layer possibly due to compressibility of foulant material on membrane surface. Particle sizes of membrane concentrate ranged from 10 to 100mum, implying that shear-induced diffusion enhance back transport of these particle sizes away from the membrane effectively. From the continuous operation of AnMBR, it was confirmed that shear rate played an important role in the reduction of membrane fouling. Membrane autopsy works at the end of operation of AnMBR showed clearly that both organic and inorganic fouling were significant on membrane surface. Surface shear by cross-flow velocity was expected to be less effective to remove irreversible fouling which can be mainly caused by the adsorption of organic colloidal materials into membrane pores.

분체 밀도와 속도를 이용한 유량검출기의 개발

김재현(Jae-Hyeon Gim),황건호(Keon-Ho Hwang),이용식(Yong-Sik Lee),정성원(Sung-Won Jeong) 한국조명·전기설비학회 2009 조명·전기설비학회논문지 Vol.23 No.5

본 논문은 발전소 보일러 및 제철소 고로의 미분탄 연소방식에 적용이 가능한 유량계 개발에 관한 연구로서 분체의 밀도와 속도로 미분탄의 유량을 측정하는 시스템을 개발하였다. 관에 흐르는 미분탄의 밀도는 관의 표면에 전극을 설치하여 기준극과 측정극사이의 커패시터를 이용하여 측정한다. 속도는 일정 거리에 두 개의 전극을 설치하고 이 전극으로부터 두 개의 파형을 교차 상관관계 알고리즘을 이용하여 계산하였다. 분체의 유량을 측정된 밀도와 속도에 의하여 계산한다. 이 시스템에 설치된 로드셀에 의한 데이터와 개발한 유량 측정 시스템의 데이터를 비교하여 신뢰성을 확인하였다. In this paper, we describe a flow meter system for pulverized coal developed for the pulverizer-burner system of a boiler or blast furnace, which uses the density and the velocity of the granule flow. The granule flow density is measured by a sensor that detects the capacitance from the electrode on the surface of the piping system. The velocity of granule flow can be calculated using the distance between two pairs of built-in sensors in the flow direction, the time obtained from the sampling cycle using the correlation method between two waveforms of the sensors. The flow rate is calculated from the density and velocity of the granule flow. The reliability and accuracy of the flow meter system has been verified by comparing the data with the weight measured from a load-cell.

Fluidelastic instability of a curved tube array in single phase cross flow

이강희,강흥석,홍두호,김종인 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.3

Experimental study on the fluidelastic instability (FEI) of a curved tube bundle in single phase downward cross flow is investigated for the design qualification and analysis input preparation of helical coiled steam generator tubing. A 6x9 normal square curved tube array with equal and different vertical/horizontal pitch-to-diameter ratio was under-tested up to 6 m/s in term of gap flow velocity to measure the critical velocity for FEI. The critical velocity for FEI was measured at the turning point from the vibration amplitude plot along the gap flow velocity. Our test results were compared with straight tube results and published data in the design guideline. The applicability of the current design guidelines to a curved tube bundle is also assessed. We found that introducing frequency difference in a curved tube array increases the critical velocity for fluidelastic instability

Modeling of permeate flux and mass transfer resistances in the reclamation of molasses wastewater by a novel gas-sparged nanofiltration

Tejal Manish Patel,Kaushik Nath 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.10

A semi-empirical model has been applied to predict the permeate flux and mass transfer resistances duringthe cross flow nanofiltration of molasses wastewater in flat-sheet module. The model includes laminar flow regimeas well as flow in presence of gas sparging at two different gas velocities. Membrane hydraulic resistance (Rm), osmoticpressure resistance (Rosm) and the concentration polarization resistance (Rcp) were considered in series. The concentra-tion polarization resistance was correlated to the operating conditions, namely, the feed concentration, the trans-mem-brane pressure difference and the cross flow velocity for a selected range of experiments. There was an appreciablereduction of concentration polarization resistance Rcpsparin presence of gas sparging. Both the concentration polarizationresistance Rcplamand osmotic pressure resistance Rosm decreased with cross-flow velocity, but increased with feed con-centration and the operating pressure. Experimental and theoretical permeate flux values as a function of cross flowvelocity for both the cases, in the presence and absence of gas sparging, were also compared.

CFD해석에 의한 마이크로 횡류수차의 속도와 압력 분포

임재익(Jae ik Lim),최영도(Young do Choi),최민선(Min seon Choi),김유택(You taek Kim),이영호(Young ho Lee) 한국유체기계학회 2007 유체기계 연구개발 발표회 논문집 Vol.- No.-

The renewable energy is necessary to develop as a countermeasure of greenhouse effect. Among the renewable energy resources, small hydropower generates few CO₂ and energy density of the small hydropower is relatively higher than that of the other renewable energy resources. Recently, development of hydroelectric power system in our country is mainly focused on the improvement of performance of the turbine-generator and also, standardization of the turbine is very important. Because of the structural feature of cross-flow turbine, standardization of the turbine is easy. The purpose of this study is to examine the optimum configuration of main variables to further optimize the cross-flow hydraulic turbine structure and to improve the performance. The turbine has been proved that the output power varies by the turbine design factors such as nozzle shape, runner blade angle and the number of the runner blade.

2 상 횡 유동장에 놓인 관군의 유체탄성불안정성

심우건(Woo Gun Sim),박미연(Mi Yeon Park) 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.2

Experiments have been performed to investigate fluid-elastic instability of tube bundles, subjected to twophase cross flow. Fluid-elastic is the most important vibration excitation mechanism for heat exchanger tube bundles subjected to the cross flow. The test section consists of cantilevered flexible cylinder(s) and rigid cylinders of normal square array. From a practical design point of view, fluid-elastic instability may be expressed simply in terms of dimensionless flow velocity and dimensionless mass-damping parameter. For dynamic instability of cylinder rows, added mass, damping and the threshold flow velocity are evaluated. The Fluid-elastic instability coefficient is calculated and then compared to existing results given for tube bundles in normal square array.