압력구멍 오차

김광웅

Korean Journal of Rheology, Vol.1, No.1, 5-11, November, 1989

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압력구멍 오차

Pressure-Hole Error

김광웅

초록

슬릿트나 관형의 흐름에서 유체의 유변학적 성질을 측정하기 위해서는 벽면에서의 압력구배(pressure gradient)를 알아야 한다. 벽면에서의 압력측정은, 특히 관형의 경우 압력구멍(pressure-hole)의 존재가 불가피하다. 압력구멍에 의한 오차에 대한 이론적인 고찰이 있었지만, 사용된 몇 가지 가정이 실험적인 관찰과 일치하지 않아 이들 이론에 대한 강한 의문을 제기하고 한다. 한편 실험적인 결과는 묽은 고분자 용액인 경우 측정압력에 대한 상대적인 압력구멍 오차가 무시할 수 없을 정도로 크다. 압력구멍 오차는 압력구멍의 크기, Reynolds수(점성) 및 Weissenberg수(탄성)의 함수로 나타나고 있다. 그러나 농도가 비교적 높은 고분자 용액이나 용융체는 상대적으로 무시할 수 있을 정도의 압력구멍 오차를 나타낸다.

To measure rheological properties in slit and capillary flows, it is essential to measure exactly the pressure gradient at the wall. Pressure measurement at the wall, particularly in capillary geometry, requires pressure-hole to connect between flow channel and pressure transducer. On the error caused by the pressure-hole, there have been some theoretical derivations with several unproved and questionable assumptions. In fact, experimental results exhibited these assumptions were not true. Further, the experiment showed that the dilute polymer solution gave relatively significant pressure-hole error. The pressure-hole error is varied with pressure-hole size, Reynolds number (viscous property), and Weissenberg number (elastic property). However, the relative pressure-hole error is negligibly small for concentrated polymer solutions and polymer melts.

[References]

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Han CD, "Rheology in Polymer Processing," Academic Press, New York (1976)
Kaye A, Lodge AS, Vale DG, Rheol. Acta, 7, 368 (1968)
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Pritchard WG, Rheol. Acta, 7, 200 (1970)
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Baird DG, J. Appl. Polym. Sci., 20, 3155 (1976)
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Han CD, Yoo HJ, J. Rheol., 24, 55 (1980)

[1] Bagley EB, J. Appl. Phys., 28, 624 (1957)

[2] Han CD, "Rheology in Polymer Processing," Academic Press, New York (1976)

[3] Kaye A, Lodge AS, Vale DG, Rheol. Acta, 7, 368 (1968)

[4] Broadbent JM, Kaye A, Lodge AS, Vale DG, Nature, 217, 55 (1968)

[5] Boadbent JM, Lodge AS, Rheol. Acta, 10, 557 (1971)

[6] Pritchard WG, Rheol. Acta, 7, 200 (1970)

[7] Brindley G, Broadbent JM, Rheol. Acta, 12, 48 (1973)

[8] Tanner RI, Pipkin AC, Trans. Soc. Rheol., 13, 471 (1969)

[9] Kearseley EA, Trans. Soc. Rheol., 17, 617 (1973)

[10] Han CD, AIChE J., 18, 116 (1972)

[11] Han CD, Kim KU, Trans. Soc. Rheol., 17, 151 (1973)

[12] Novotny EJ, Eckert RF, Trans. Soc. Rheol., 17, 227 (1973)

[13] Higashitani K, Lodge AS, Trans. Soc. Rheol., 19, 307 (1975)

[14] Baird DG, J. Appl. Polym. Sci., 20, 3155 (1976)

[15] Higashitani K, Pritchard WG, Trans. Soc. Rheol., 16, 687 (1972)

[16] Mooney M, J. Rheol., 2, 210 (1931)

[17] Rabinowitsch B, J. Phys. Chem., A145, 1 (1929)

[18] Han CD, Yoo HJ, J. Rheol., 24, 55 (1980)