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비압축성 점성류의 칼렌더공정에 대한 유변학적 해석(II)
Hydrodunamic Analysis of Viscous Incomproessible Fluid Flow in Calendering Processes (II)
HWAHAK KONGHAK, August 1981, 19(4), 303-312(10), NONE
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Abstract
고분자가공등의 공정에서 흔히 볼 수 있는 비뉴톤성 유체의 유동현상을 해석하기 위한 연구의 일환으로서 비대칭형칼렌더에서의 viscous heating효과를 고려한 비뉴톤성 유체의 속도, 압력장 및 온도분포의 변화를 수치해석적으로 관찰하였다. 비등온상태의 압력장은 등온상태의 경우에 비하여 약 25 % 정도 감소함을 보이며 특히 이로부터 유입영역이 확장되어 recirculating flow가 일어나는 fluid envelope이 형성됨을 관찰할 수 있었고, 국부적 온도상승이 약 30 ℃에 달하므로 열분해가 쉬운 고분자물질의 가공에 있어 안정성 문제를 고려할 때 회전속도가 빠른 roll을 더 냉각하는 것이 효과적임을 알 수 있었다. 이와 아울러 정상상태의 고점성유체의 수치모사실험에서 야기되는 안정성 문제의 해결에 successive under relation의 차분법이 효과적임을 입증하였다.
A numerical solution has been developed for the steady state partial differential equations which discribe the flow of non-Newtonian fluids into geometrically and kinematically asymmetric calenders with viscous heating effects. The solution technuque combines the equation of motion at the isothermal condition. the asymmetric calenderign system is simplified by use of bicylindrical coordinates wiich establishes uniform size network for each variable. the initial condition is simply that the calender gap is filled completely with certain fluid whose initial temperature is uniformly constant. Viscous heating is shown to drastically change in the velocity and pressure field near the entrance andexit zone. The temperature distribution exhibits two local maxima and a minimum in the direction of flow, an dthe maximum temperature rise is about 30 ℃ near the roll surface. Numerically stability propblem of the steady state equations associated with high viscosity fluid flow is treated and solved by the use of the successive under relaxation method.