농축현탁계의 점도

서문호,이기준 한국화학공학회 1975 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.13 No.2

複數粒子 懸濁系에 관한 統計力學的 硏究의 一環으로서 dynamical state의 configuration에 대한 model로 hexagonal lattice system을 잡고, 粒子의 濃度와 系의 粘度函數와의 關係를 규명하였다. 이 model system에서 任意의 代表粒子는 8個의 最近接 周圍粒子를 가지며 最高濃度는 60.4%로서 이들은 random packing의 實際 system과 近似하다. 本 model을 使用하여 統計力學的으로 計算된 粘度函數는 이미 硏究된 simple cubic model에 비하여 實測値들과 보다 좋은 一致를 보였다. 以上의 硏究에서 粒子의 configuration을 考慮한 mode이 濃縮 懸濁系의 流動變形特性을 計算하는데 效果的임을 確認하였다. The viscosity of suspensions of rigid spheres is obtained using the model system of hexagonal lattice configuration by means of statistical mechanics. The number of nearest neighbors of a representative sphere in this arrangement is eight which is quite close to the measured coordination number of about seven to eight for randomly packed spheres. The maximum attainable concentration of the system is 60.4 percent which is comparable with that obtained for the real system of random packing. The viscosity-concentration relationship calculated from the present model is compared with that of earlier work for simple cubic arrangement and found to be in better agreement with the compilations of experimental data of Rutgers and Thomas. It is known from the above analysis that a model dealing with particle configurations is essential to predict the rheological properties of concentrated suspensions.

다공성 매질내 유체의 대류열전달에 관한 실험 및 이론적 연구

서문호,이재욱,신안식 한국화학공학회 1985 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.23 No.5

다공성 매질내 유체의 자연대류에 관한 제반 현상을 Rayleigh수의 변화에 따라 포괄적으로 연구하기 위하여 실험을 수행하고, 이 결과를 이론적으로 해석하기 위하여 수치모사를 행하였다. 실험장치는 염료를 이용한 유동가시화(flow visualization)실험을 위하여 얇은 유리상자를 제작하고, 유리구슬과 증류수를 채워 다공층을 구성하였으며, 상하면의 온도차를 변화시켜 자연대류를 유도하였다. 수치모사에서는 유동가시화를 위한 유리상자형 실험장치의 전후면에서의 열손실을 고려하기 위하여 핀(fin)이론을 도입, 수식화하고, 이차원 자연대류에 대한 유동 및 온도분포에 관한 미분방정식들을 유도한 다음 유한차분법으로 해를 구하였다. 상기 연구의 결과 온도분포와 열플럭스에 대한 지식뿐만 아니라 다양한 유동셀의 변화를 유동가시화로 관찰할 수 있었으며, 실험 및 이론적 해석의 결과들은 상호 정성 및 정량적 비교가 가능하였다. The phenomena of natural convection in a fluid-saturated porous medium were studied experimentally for a wide range of Rayleigh number. The experiments were carried out in a rectangular glass tank of very small width to facilitate flow visualization. Mixtures of glass beads and distilled water were used as a porous bed. The bed was heated from below and cooled from above, and the flow was visualized by photographing dye streaks. A theoretical analysis was also included to simulated the experimental results. In the analysis the thin rectangular box was thought of a fin losing heat to the surroundings in order to examine the effect of lateral heat losses. The experimental results contain both quantitative information on the temperature fields and flow visualizations on the various convective flow patterns. The convective flow behavior of the numerical simulation was qualitatively identical to that of the experiment.

고분자 복합재료의 반응성형공정에 관한 수치모사 연구 ( Numerical Simulation on Reaction Molding Processes of Polymer Composites )

서문호,O. Pironneau,김하진 대한전자공학회 1989 특정연구 결과 발표회 논문집 Vol.- No.-

報漏閣 自擊漏 硏究(IV) : 更點機構

서문호,한영호,남문현 건국대학교 산업기술연구원 2006 건국기술연구논문지 Vol.31 No.-

The most distinctive feature of Jagyeongnoo is its simple and secure mechanisms devised for automatic audio-visual time announcing system. The Veritable Records Sejong Sillok suggested that special emphasis had been put upon signaling subdivided night-watches with mechanical logic operator. In this paper, the details of the night-watch signalling mechanism was described at full length. Through the recent reconstruction of the whole system of Jagyeongnoo which has been missing for several hundred years, the authors could discover the real ingenuity of Jang Yeong-sil displayed on the first Korean mechanical clockwork.

농축현탁계의 점도 : 두 가지 구형입자로 구성된 단순입방모형 Bimodal Simple Cubic Model

서문호,이기준,이재욱 한국화학공학회 1977 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.15 No.1

두가지의 크기가 다른 경질구형입자가 同一한 數密度로 分散되어 있는 bimodal系의 단순입방모형을 設定하였다. 이 모형에서 使用한 粒度比는 0.05∼1.0이며 最高濃度는 粒度比의 函數로서 그 比가 0.5인 경우 69.81%가 된다 均一分散系에서의 粘度에 비하여 bimodal系에서의 粒度比가 감소할수록 系의 粘度가 현저하게 감소하며, 그 比가 0.1에서 系의 粘度는 최저값을 갖는다. 또 상대입자농도에 대한 상대점도는 粒度比가 0.414 즉 작은 입자 지름이 square pore path effective diameter에 접근할수록 최고값에 접근했는바, 이는 문헌상의 실험적 관찰과도 부합된다. 동일한 농도의 경우, 두 가지 다른 크기의 粒子가 섞여 있는 分散系가 均一分分散系에 比해서 보다 작은 粒度値를 보여준다는 사실이 以上과 같이 流體力學的 理論에 의거해서 처음으로 해석되었다. The bimodal system of simple cubic particle configuration was studied as an extension of the earlier works. In this model two different size rigid spheres were arranged alteranatively. The diameter radio of the two particles ranged from 0.05 to 1.0 and the total particle concentration by volume ranged from 52.4 to 79.2 percent. It was theoretically shown that the relative viscosity of the model system decreased, in comparison to the unimodal systems, as the particle size ratio decreased at a given concentration, whereas the change relative viscosity was insignificant below the limiting size ratio of about one tenth and the viscosity of the bimodal system was almost equivalent to that of the unimodal system above the size ratio of about eight tenth. These facts were in good agreement with the experimental data reported in the literature.

직물구조가 신합섬직물의 역학적 특성에 미치는 영향(I)-직물밀도 및 감량가공이 전단특성에 미치는 영향-

서문호,Seo, Moon-Hwo 한국섬유공학회 1994 한국섬유공학회지 Vol.31 No.12

A new theoretical fabric shear model has been presented and a quantitative study has been conducted on the shear properties of polyethylene(terephthalate) (PET) fabrics of four different fabric densities and five different weight reduction. The fabric shear properties were measured with KES-F handle measurement system. From the theoretical and experimerntal studies. following results can be summarized : 1) The fabric shear behavior is strongly dependent on the fabric density and free volume available for the constituent yarns and their filament. 2) Shear hysteresis at the small shear angle(2HG) is dependent more on the yarn tensile properties than on the fabric structure. 3) Shear hysteresis at the shear angle, 5$^{\circ}$(2HGS) is dependent more on the interaction between two crossing yarns which is directly related on the fabric structure than on the yarn tensile properties.

사출성형 고분자물질의 공동충전현상에 관한 유변학적 해석

서문호,이기준,정광식 한국화학공학회 1989 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.27 No.4

고분자물질 용융체가 4각 공동에 하단 입구로부터 진입하는 충전단계에서 자유표면이 전진 이동하는 현상이 수치모사의 기법으로 해석되었다. 수치해석을 위하여 전진이동표면을 다루는 MAC법과 운동방정식을 유한차분화하는 DuFort-Frankel법이 사용되었고, 유체의 점탄성 거동을 조사하기 위하여 Leonov모델을 도입하였으며 Carreau의 점성유체모델의 결과와 비교하였다. 연구의 대상 시료는 저밀도 폴리에틸렌을 선정하여 시간변화에 따른 충전현상을 모사하였다. 고분자물질이 진입하는 과정에서 Gv수와 Ws수가 작은 경우에 jet 흐름 현상이 관찰되는 바 이는 점성력보다는 중력의 역할이 크게 작용하여 전체적인 유동형태가 Fr수보다는 Gv수의 함수임을 보여준다. 또한 전진표면의 거동과 속도에 대한 수치모사의 결과가 실측치와 잘 일치됨을 보여준다. Numerical simulation of free surface flow phenomena is presented for the system where a polymeric melt flows into a vertical rectangular cavity which has an inlet gate. The numerical technique combines a modified version of marker and cell method with DuFort-Frankel finite difference approximation to the equations of motion. The Leonov model is introduced for the viscoelastic fluid and compared with the Carreau model analysis for inelastic fluid. The low density polyethylene is used as sample material and the free surface profiles of the flow are simulated with time. The jet-like behavior in the flow front of the polymeric melt appears when both the Gravity number and the Weissenberg number are small. The ratio of gravitational to viscous force plays prevailing role than the elastic force itself. Thus the overall flow pattern is mainly a function of the Gravity number than the Froude number as speculated. The numerical predictions of surface profiles and the velocities of the advancing front are in good agreement with the experimental data.

다공성 매질내 유체의 자연대류에 관한 연구

서문호 한국화학공학회 1982 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.20 No.5

다공성 매질내에서 일어날 수 있는 유체의 다양한 자연대류 열전달 방식들을 결정하고, 이들의 특성을 조사하기 위하여 바닥이 가열되며 투수성 상층면을 가지는 상자를 모델로 광범위한 수치실험을 수행하였다. 유체의 유동과 전열현상을 모사한 Darcy-Boussinesq 식의 해를 유한차분법으로 구하였는 바 Poisson형의 압력식은 직접해법으로 해를 구하여 수치적인 잡음을 제거하였고, 에너지식은 중심차분법이나 upwind 차분법의 단점을 보완시킨 power-law weighted upwind차분법으로 풀어 오차확산을 방지하였다. 본 연구에서는 일정한 Rayleight 수에서도 여러가지의 정상상태 자연대류 및 진동성 대류유동이 셀(cell)수에 따라 가능함을 확인하였고, 정상상태의 다중셀 유동이 시작되는 임계 Rayleigh 수와 비정상상태의 진동성 대류가 시작되는 이차 임계 Rayleight 수를 2∼5중셀 대류방식에 대하여 각각 결정하였으며, Nusselt수를 Rayleight수와 셀의 수에 따라 계산함으로써 전열속도가 최대가 되는 최적 대류열전달 방식을 결정할 수 있었다. In order to examine the characteristics of the various types of convection that can occur in a fluid-saturated porous material, numerical experiments are carried out for a permeable-top box heated from below. A cyclic reduction method is applied for solving Poisson-type pressure equation to avoid false flow fields due to the iterative numerical noise and a modified upwind scheme is utilized to overcome diffusional truncation errors in solving energy equation of parabolic type. The main results of the present study are as follows. The conditions leading to onset of multicellular steady convections, second critical Rayleigh numbers above which fluctuating unsteady convections exist, variations of Nusselt number with Rayleigh number, and the effective convection patterns which maximize the heat transport are determined as functions of convective cell-number. In summary, the results show that the various types of convection are possible for a given Rayleigh number and box geometry depending on the initial conditions.

연신비가 Nylon 6의 밀도 및 수분율에 미치는 영향

서문호,조정호,김상용,Seo, Mun-Ho,Jo, Jeong-Ho,Kim, Sang-Yong 한국섬유공학회 1975 한국섬유공학회지 Vol.12 No.4

Experimental studies on the density and moisture regain of nylon 6 fibers with varying draw ratios and draw temperatures have been carried out. Relationships among fiber densities, moisture regains, draw temperatures and draw ratios, and various combinations of these properties are analyzed. Results from these analyses are as follows: 1) The density of nylon 6 fibers increases with the moisture regain at the early stage of absorption and decreases after a certain value. 2) fiber density increases rapidly with the increase of draw ratio up to about 2 and after it increasing rate becomes small. 3) As the draw ratios and draw tempertures become higher, peak points of the curves of moisture regains and densities move toward the higher density and the lower regains. 4) the structure of nylon 6 fiber is unstable at draw ratios between 1∼2. 5) Mechanisms of change of the structure and mechanical properties of nylon 6 fibers due to drawing and temperature are different.

연신비와 열고정온도가 Nylon 6섬유의 열응력 및 손실 Tangent에 미치는 영향

서문호,조규수,김상용,Seo, Mun-Ho,Jo, Gyu-Su,Kim, Sang-Yong 한국섬유공학회 1979 한국섬유공학회지 Vol.16 No.4

Investigation was made on the thermal stress and loss tangent of nylon 6 fibers oriented at different draw ratios and heat set at different temperatures and the following results were obtained. 1. Thermal stress of nylon 6 fibers can be divided into two components, one is contributed from the amorphous regions, and the other from the crystalline regions. 2. Thermal stress of nylon 6 fibers contributed from the crystalline regions tends to increase with draw ratio irrespective of heat setting temperature. 3. Thermal stress contributed from the amorphous regions decreases with heat setting temperature. 4. Max. loss tangent decreases with the increase of draw ratio and increases with heat setting temperature, while max. loss tangent temperature increases with draw ratio and decreases with heat setting temperature. 5. Max. loss tangent and its temperature are linearly correlated with negative slope.