Centrifugal analysis of pivoted-rotor systems for capillary pressure measurements
✍ Scribed by Z. Andy Chen; Douglas W. Ruth
- Publisher
- American Institute of Chemical Engineers
- Year
- 1997
- Tongue
- English
- Weight
- 860 KB
- Volume
- 43
- Category
- Article
- ISSN
- 0001-1541
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✦ Synopsis
The fundamental theory on centrifuge determination for capillary pressures was laid by Hassler and Brunner in 1945. Christiansen (1992) and Ayappa et al. (1994) demonstrated the significance of the radial effect. Forbes et al. (1994) reexamined quantitatively the radial effect by using a simplified analytical solution to the double-integral model. More recently Chen and Ruth (1995) developed a three-dimensional model characterizing the whole centrifugation mechanism. They found that gravitational acceleration also plays an important role and is most pronounced at speeds o < 500 rpm, and that this effect leads to inaccurate interpretations of capillary pressure information at high saturation, near the threshold pressure. A remedial approach by means of numerical parameter estimation techniques was discussed recently (Chen and Ruth, 19941, and an experimental attempt by redesigning a pivoted rotor configuration was reported by Pohjoisrinne et al. (1996). This note outlines the result of a theoretical investigation of the pivoting rotor physics to support the experimental study.
Conventional Beckman centrifuges have fixed, horizontal rotors, stretching out from the central axis of rotation. Such a configuration is depicted in Figure 1. The basic equation for describing the centrifugation process is given by Zero-capillary pressure occurs at the two tangent points that are defined by the intersection of the paraboloid of revolution characterized by rOmm and the edge of the outside endface. Details on the horizontal rotor investigation were reported elsewhere (Chen and Ruth, 1995).