Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Patent
1992-02-13
1993-10-19
Dawson, Robert A.
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
210320, 21032175, 210356, B01D 6100, B01D 6128
Patent
active
052542599
DESCRIPTION:
BRIEF SUMMARY
A first aspect of the invention relates to a method and apparatus for effecting transfer of heat or mass to or from a fluid, which is usually a liquid, through a transfer membrane. Such technique is used in blood oxygenators and dialysers, in which case one fluid is blood and the other is oxygen or dialysate. Alternatively such apparatus may be used for filtering, for example components such as plasma from whole blood, or for introducing or removing material into or from a bioreactor.
In practice the efficiency of the transfer across the membrane is limited to the extent to which the total volume of fluid can be brought into close proximity with the membrane. One solution to this problem is disclosed in GB-A-1442754 and EP-A-0111423 and involves passing one fluid with a pulsatile, and preferably reversing, flow, but with a mean flow, through a conduit, a wall of which is provided with a regularly longitudinally repeating array of hollows, such as dimples or transverse furrows, as a result of which vortices are set up in the fluid in the hollows. In practice, the geometry has been such that one vortex has been formed in each hollow. When reversing flow, which is preferred, is used, the vortices, which have all been rotating in the same sense, are shed from the hollows into the mainstream flow and decay when the flow in one direction decelerates, and are reestablished in the hollows, but with rotation in the opposite sense, when the flow has reversed and accelerates in the opposite direction along the conduit. This repeated decay and reversal in the direction of rotation of the vortices is less efficient in mixing the fluid, than if the vortices were maintained continuously.
The production of vortices in a liquid may also be used according to a second aspect to promote thorough mixing of the components of a fluid, for example to promote a chemical reaction between components; or to promote contact between the fluid and a component such as an affinity ligand immobilised on a support.
In accordance with the present invention, in a method utilising vortices in a fluid, the fluid is passed with reversing, but mean, flow through a conduit comprising at least one chamber defined between two side walls, the chamber being provided at its ends spaced along the conduit with a restricted inlet and a restricted outlet, the Reynolds and Strouhal numbers of the fluid system, and the aspect ratio of the length of the chamber to the width of the chamber between the two walls being such that at least three vortices are set up in a standing pattern along the chamber with adjacent vortices rotating in opposite senses about axes perpendicular to the length and width of the chamber and with mainstream flow of the fluid passing along the chamber and sinuously around the vortices alternately between a vortex and different one of the walls, reversal of the flow direction reinforcing the vortices so that each continues to rotate in the same sense but with the sinuous flow now passing around each vortex and the opposite wall.
The inlet and outlet will be at the upstream and downstream ends, respectively, of the chambers as considered in the direction of mean flow, although the nominal outlet will act as an inlet during that part of each flow cycle when the flow is in the reverse direction to the mean flow.
This technique is an extension of the previous technology, in effect by extending the dimensions of the hollows along and across the conduit and providing particular parameters, including the sizes and positions of the restricted inlet and outlet to the chamber, the stroke and frequency of the pump or pumps producing the reversing but mean flow, and the viscosity of the fluid, all of which are in practice determined by selected Reynolds and Strouhal numbers and chamber aspect ratio, so that a virtual standing wave pattern is set up in the chamber with three or more continually rotating vortices. These vortices will oscillate, with adjacent vortices out of phase with one another, to and fro between the opposed walls of the chamber,
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Bellhouse Brian J.
Sobey Ian J.
Dawson Robert A.
Kim Sun Uk
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