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Leonard D. Tijing,Bock Choon Pak(박복춘),Byung Joon Baek(백병준),Dong Hwan Lee(이동환) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
The present study investigated the mechanism of physical water treatment through particle count analysis of the water sample with and without physical water treatment (PWT) technology. The PWT methods utilized catalytic devices and low-voltage-high-frequency device wherein water continuously recirculated through them. Concentrated hard water at 2,300-2,700 μS/㎝ electrical conductivity was utilized in the study at two different flow rates (i.e., 500 l/h, and 800 l/h). After 66 hours of operation for each test, the results showed that the total number of particles in the PWT-treated cases increased from 165-539% as compared with the no-treatment cases depending on the flow rate used. The present results provided by particle counting support the bulk precipitation hypothesis as the mechanism of PWT and electro-flocculation mechanism with the use of catalytic materials and LVHF technique.
촉매물질을 이용한 수처리 기법의 결정화 화울링의 저감에 관한 연구
김선도(Sun Do Kim),박복춘(Bock Choon Pak),백병준(Byung Joon Baek),김철생(Cheol Sang Kim) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4
The present experimental study aimed to investigate the feasibility of physical water treatment (PWT) devices using catalytic materials to mitigation of crystalization fouling. Two PWT devices having different shape and material were used. The results from microscopic observation and SEM photographs demonstrate that the crystal structure of CaCO₃ is Argonite type without water treatment while Calcite type with water treatment, which clearly shows the feasibility of PWT techinque using catalytic materials to mitigate crystalization fouling. For 500 ppm solution, the fouling resistance decreased up to about 23% due to physical water treatment using catalytic materials. The results also reveal that if two more techniques are used simultaneously the additional effects could be expected.
A novel viscosity measurement using a falling ball viscometer with a high-speed camera
Won Jin Jo(조원진),Bock Choon Pak(박복춘),Young I Cho(조영일) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
This study introduces a new approach to a falling ball viscometer by using a high speed motion camera to measure the viscosity of both Newtonian and non-Newtonian fluids from the velocity-time data. This method involves capturing continuous photographs of the entire falling motion of the ball as the ball accelerates from the rest to the terminal velocity state. Ball’s velocity was determined from the distance traversed by the ball by examining video tape frame by frame using the marked graduations on the surface of the falling ball cylinder. Each frame was pre-set at 0.01. Glycerin 74% was used for Newtonian solution, while aqueous solutions of Polyacrylamide and Carboxymethyl Cellulose were for non-Newtonian solutions. The experimental viscosity data were in good agreements with the results obtained from a rotating Brookfield viscometer.
EQCN을 이용한 금속표면의 바이오화울링 형성에 대한 정량적 고찰
정민영(Yung Min Jung),박복춘(Bock Choon Pak),백병준(Byung Joon Baek),김철생(Cheol Sang Kim) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.10
It is known that biofouling behavior is related to the physicochemical variables such as fluid velocity, solid surface condition, temperature, PH value, oxygen and nutrient concentration. The surface characteristic of reservoir materials is one of the major factors determining the deposition rate of living organisms. The initial biofouling behavior was investigated by measuring the mass of bacterial deposition on the various metal surfaces immersed in the stationary solution and the antibiofouling effect of ultra-violet light was also examined on titanium surface. We used three types of bacteria which can be encountered easily in the water treatment systems such as water tank or heat exchanger. These bacteria were cultured up to maximum contents(over 10 bacteria/ml) and the deposition degrees of the bacteria on the Au, Cu, Ni, Cr, and Ti surfaces were measured using an electrochemical quartz crystal nanobalance(EQCN). Resolution limit obtained for the EQCN was about 0.1 ng. The amounts of Klebsiella aerogenes and Escherichia coli deposited on Au surface used as control group, were remarkably higher than those adhered on the other metal surfaces. However, the mass of the Pseudomonas fluorescens adhered on Ti surface was about 1.1, 1.4, 1.8 and 2.5 times greater than those deposited on Au, Cu, Cr and Ni surfaces respectively. In general, Au and Ti which are known as bioinert materials, showed high bacteria deposition behavior which is closely associated with the initial biofouling formation. The bacteria deposited on the Ti surface were removed gradually by irradiation of ultra-violet light. The antibiofouling effect of Cr, Ni, Cu may be due to the toxic reaction occurring at the interfaces between the solution and the metal surfaces.
A study on heat transfer enhancement using straight and twisted internal fin inserts
Leonard D. Tijing,Bock Choon Pak(박복춘),Byung Joon Baek(백병준),Young I. Cho(조영일) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
The present study investigated the effect of internal aluminum fins with a star shape cross section on the heat transfer enhancement and pressure drop in a counterflow heat exchanger. A concentric tube heat exchanger was used with water as the working fluid. The heat transfer rate increased by 12-51% over the plain tube value, depending on the internal fin configuration used. However, the pressure drop also increased substantially by an average of 286-338%. The results showed that a straight fin configuration is good enough to produce a heat transfer increase in a counterflow heat exchanger. Twisted fin configurations did not further increase the heat transfer rate.
원형 핀튜브 열교환기의 공기측 압력강하 및 열전달 특성에 관한 실험
심왕희(Wang Hee Shim),박복춘(Bock Choon Pak),이동환(Dong Hwan Lee) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
The purpose of this study is to investigate the pressure drop and heat transfer characteristics of air side at the cross flow multi-pass heat exchanger with circular external fin tubes. Two different heat exchangers having wavy circular finned tubes (WCFT) and straight circular finned tubes (SCFT) were used in the experiments. The results shows that the air-side heat transfer and the pressure drop increased with increasing air velocity as expected. However, significant finding was that heat transfer performance of the WCFT was higher than that of the SCFT by 15-20% while the pressure drop of WCFT was higher than that of the SCFT by 10~15%. This implies that use of wavy circular finned tubes could reduce the size of heat exchanger.
Pressure drop and heat transfer characteristics of star-shaped internal finned tubes in cross flow
Yong Shin(신용),Carlo Granaderos(칼로 그라나데로스),Bock Choon Pak(박복춘),Byung Joon Baek(백병준) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
This paper investigated the compound effect of aluminum star-shaped internal fin inserts together with straight and wavy external fins of the heat transfer enhancement and pressure drop in a cross flow heat exchanger. The internal fin inserts had straight and twisted configurations. The tests were carried out using distilled water and 50% aqueous solution of glycerin at the hot-side and air at the cold side. The results indicated that the inner tube convective heat transfer coefficients increased by 16%~143% but with corresponding pressure drop of 633%~682% depending on the mass flow rate, air velocity, and configurations of both internal and external fins. The straight star-shaped internal fin insert with any external fin configuration show the best heat transfer performance.
MOCVD 반응로내 GaN 성장에 미치는 입구형상의 영향
윤성규(Sung Kyu Yun),백병준(Byung Joon Baek),박복춘(Bock Choon Pak) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11
Numerical calculation has been performed to investigate the effect of inlet configuration on the<br/> growth rate of GaN layer on the heated susceptor. The conventional single inlet, where the gas is<br/> mixed by force in the inlet, is compared with separated flow inlet. Two-parallel gas flow H2 and<br/> NH3<br/> are separated by a plate with finite length which are also parallel to the susceptor. The effect<br/> of separated plate length, carrier gas and flow rate of each precursor on the mixing of reactant<br/> gases and growth rate were investigated. Furthermore the three dimensional model is employed to<br/> predict the transverse variation of growth rate.
고품질 질화물 반도체 박막 성장을 위한 반응로 구조 및 열적 조건에 관한 연구
김진택(Jin Taek Kim),백병준(Byung Joon Baek),박복춘(Bock Choon Pak),Cheul Ro Lee 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.10
Numerical calculation has been performed to investigate the transport phenomena in the horizontal reactor which has two different gas inlets for MOCVD(metalorganic chemical vapor deposition). The full elliptic governing equations for continuity, momentum, energy and chemical species are solved by using the commercial code FLUENT. It is investigated how thermal characteristics, reactor geometry, and the operating parameters affect flow fields, mass fraction of each reactants. The numerical simulations demonstrate that flow rate of each species, inlet geometry of the reactor, and its distance from the susceptor as well as the inclination of upper wall of reactor can be used effectively to optimize reactor performance. The commonly used idealized boundary conditions are also investigated to predict flow phenomena in the actual deposition system.
趙秉守,白秉峻,朴福春 全北大學校 1996 論文集 Vol.41 No.-
An electronic circuit board was simulated by protrusions, which was heated by thin stainless foil attached on the surface, in a vertical channel. Natural and forced convection experiments were carried out in order to investigate the effects of channel spacing, gap between protrusions and number of rows of protrusion. In natural convection, the optimum channel spacing was found to be approximately 30mm regardless of the protrusion gap. For optimum channel spacing the heat transfer coefficients were converged to an asymptotic value after fourth row. The heat transfer coefficient for each row approaches to constant values for protrusion gaps larger than 10 mm. An experimental correlation has been suggested by using a modified Rayleigh number, based on the dimensionless characteristic length(G/L). In forced convection, the heat transfer coefficients were not merged to an asymptote until the fifth row and increased as channel spacing at the constant Reynolds number decreases.