WO1981002683A1

WO1981002683A1 - Tubular channel diffusion device having flow guides therein

Info

Publication number: WO1981002683A1
Application number: PCT/US1981/000113
Authority: WO
Inventors: C Kopp
Original assignee: Baxter Travenol Lab; C Kopp
Priority date: 1980-03-24
Filing date: 1981-01-26
Publication date: 1981-10-01
Also published as: EP0048730A1

Abstract

A diffusion membrane unit (10) comprises a plurality of capillary membrane fluid flow tubes (12). An elongated flow guide member (14) is positioned within the capillary membrane tubes, with the flow guide member defining at least one radial fin (18) positioned longitudinally along the axes of the flow tubes. The radial fin defines a helical relation along its length, whereby fluid passing through the capillary membrane tubes is impelled to flow in a helical path, for increased mixing of the liquid in the capillary membrane tubes.

Description

TABULAR CHANNEL DIFFUSION DEVICE HAVING FLOW GUIDES THEREIN

Capillary fiber dialyzers are available, such as the CP dialyzers sold by the Artificial Organs Division of Baxter Travenol Laboratories, Inc., and various competing dialyzers of similar type.

These dialyzers utilize a large number of capillary fibers to form a flow path for blood in the bores, while the dialysis solution passes along the outside of thefibers. Typically, the diameter of the bore of the capillary fibers may be on the order of 200 microns, to minimize the effects of laminar flow of the liquid within the capillaries, which may reduce the level of dialysis or other diffusion treatment of the blood.

It would be desirable to construct diffusion devices having larger diameter tubular flow paths than 200 microns. However, the effects of laminar flow in significantly larger tubular flow paths can result in the incomplete treatment of the portions of liquid positioned near the central axis of the tubular flow path. In accordance with this invention, a flow guide member is positioned within diffusion membrane tubes, which serves to alter the laminar flow through the fluid flow tubes of the diffusion membrane in such a manner than fluid is impelled outwardly from the vicinity of the center of the membrane fluid flow tube, toward the membrane wall, for complete processing of the liquid passing through the tubular diffusion membrane.

Accordingly, it becomes possible to use tubular, semipermeable membrane having larger inner diameters without significant losses in diffusion efficiency. This, in turn, provides the advantage of easier and cheaper construction of the diffusion devices through a reduction in the number of capillary members that are required, since each capillary member provides a gentle, turbulent swirling flow to the blood passing through it, for high efficiency diffusion treatment, while the blood or other material to be treated can pass through the capillary membrane fluid flow tube of this invention in higher quantities.

Description of the Invention

In accordance with this invention, a diffusion membrane unit may comprise a plurality of capillary membrane fluid flow tubes in which elongated flow guide member means is positioned within the capillary membrane tubes.

The flow guide member means defines at least one radial fin positioned longitudinally along the axes of said flow tubes, with the radial fin defining a helical relation along its length. Accordingly, fluid passing through the capillary membrane tubes is impelled to flow in a helical path. This in turn causes a swirling action within the fluid passing through the tube, for example by Coriolis force eddys, for increased mixing of the liquid, so that the inner portions adjacent the central axis of the membrane tube are impelled outwardly into contact with the walls of the membrane tube, where the diffusion process takes place.

Preferably, a plurality of radial fins are defined by the flow guide member means, with a plurality of radial fins defining a generally constant cross-sectional angular relation to each other. In other words, the radial fins may define in cross section three quiangular fins, spaced 120° from each other, or four equiangular fins spaced 90° from each other, by way of example only.

Accordingly, blood dialyzers and oxygenators, membrane plasmapheresis devices, ultrafiltration devices, and other diffusion type devices may be efficiently made out of relatively large flow tubes, containing the flow guide member means of this invention.

For example, it may be desired to utilize tubes for blood flow for a membrane oxygenator in which the tubes are made of a desirable oxygenation membrane material; for example, a porous hydrophobic material such as polyethylene or polypropylene having pores on the order of 0.1 to 1 micron in diameter. The inr.er diameter of these tubes may be on the order of 500 micrcns, which is normally a large diameter for optimum mixing of blood in its passage through the tube. However, with the flow guide member of this invention, which may be a profiled device coextruded or otherwise formed with the tube, a high diffusion efficiency may be retained. Also, other materials which may be utilized as tubular membrane materials in accordance with this invention are cellulose for a dialysis membrane, or polycarbonate or polyvinyl alcohol material. Silicone rubber or polytetrafluoroethylene may be used as oxygenation membranes or the like. Similarly, known materials may be used for membrane plasmapheresis, ultrafiltration, or other uses as may be desired.

Likewise, the construction of the diffusion device of this invention may be conventional if desired, with the exception of the flow guide member means utilized in accordance with this invention.

Referring to the drawings, Figure 1 is a perspective view, with portions broken away, of a coextruded diffusion membrane unit defining an internal flow path which includes a plurality of spaced parallel tubes, each of the tubes containing an elongated flow guide member means in accordance with this invention.

Figure 2 is a longitudinal sectional view of a dialyzer using a stack of flow guide members in a housing. Referring to Figure 1, a diffusion membrane unit

10 is shown defining an internal flow path which comprise a plurality of spaced, parallel, tubular flow paths 12 for a fluid material to be treated within the diffusion membrane unit. For example, the diffusion membrane unit may be a cellulose based material, a polycarbonate, or a polyvinyl acetate material capable of extrusion, it if is desired to use the device as a dialyzer. In this instance, the blood can pass through tubes 12, while the entire diffution membrane unit 10 is enclosed in an outer housing 13 as shown in Figure 2 to provide a flow path for dialysis solution to pass across the exterior of diffusion membrane unit 10. The specific construction of the diffusion membrane unit 10 may be similar to that disclosed in the U.S. patent application of Clinton V. Kopp and Dilip Shah filed concurrently herewith and entitled "METHOD OF FORMING DIFFUSION MEMBRANE UNITS".

The device of Figure 1 can be seen to be a single, integral, extruded structure, although other, non-integral structures may be made utilizing the principles of this invention as well. Suitable known oxygenation membranes as well as dialysis membranes may be utilized with this invention.

In accordance with this invention, a flow guide member 1-4 is positioned within each capillary membrane tube 12. As specifically shown in Figure 1, the flow guide members 14 are integrally coextruded with the capillary membrane tubes 12 which, in turn, are coextruded with each other, being joined together by vanes lβ to provide an integral structure.

Each flow guide member.14 defines at least one radial fin 18 positioned longitudinally along the longitudinal axes of flow tubes 12. Specifically, each flow guide member is shown to have four radial fins, defining a generally constant cross-sectional angular relation to each other so that each of the fins 18 are positioned at 90° to their adjacent fins throughout the entire length of the flow guide member.

As shown in Figure 1, the radial fins 18 define a helical relation along their lengths, with the result that fluid passing through the capillary membrane tubes is impelled to correspondingly flow in a helical path 19 between fins 18. The result of this is the previously mentioned increased mixing of the liquid, apparently through fluid eddies caused by Coriolis force, which is generated by the helical rotation of the liquid about the axis 20 of each flow tube 12. Accordingly, as stated above, larger diameter fluid flow tubes 12 may be utilized without a significant loss in diffusion deficiency, resulting in simpler and more effective diffusion devices such as dialyzers and oxygenators for blood, as well as membrane plasmapheresis devices. In other embodiments of this invention, the flow guide member may be separately extruded and then assembled into fluid flow tubes, which, for example, may comprise a pair of plastic sheets which are then sealed together between the flow guide members. This provides the added advantage that the flow guide members may serve as mandrels in accordance with the previously cited patent application of Kopp and Shah, in that the flow guide members may serve to help define the flow paths between the sealable sheets of a diffusion membrane unit. Accordingly, the flow guide members may be laid and spaced in parallel relation on a first sheet, and then overlaid by a second sheet, followed by a sealing step at linear areas between the flow guide members, so that the flow guide members serve both as mandrels for helping to define the flow paths during the sealing step, and are not removed but retained in the diffusion membrane unit, to provide the improved flow characteristics in accordance with this invention.

Referring to Figure 2, a stack of extruded diffusion membrane units as shown in Figure 1 is seen to be encased in a housing 13 defining dialysis solution inlet 22 and outlet 24, adapted to communicate with the dialysis solution compartment 27 inside of housing 13, which communicates with both exterior sides of each diffusion membrane unit 10, for example, by side entry between units 10 adjacent the ends thereof.

Optionally, flow screening 28 or the like may be provided between the membrane units 10 in the stack. This dialyzer, or any other diffusion device constructed along similar lines, may be very easily constructed by simply assembling the various layers of the extruded diffusion membrane units 10, optionally separating them with flow screening 28, to provide a stack of diffusion membrane units for a high capacity dialyzer, oxygenator, or other diffusion device. The dialysis solution flow path may be manifolded in any conventional manner to provide good dialysis solution flow contact across the outer surfaces of fluid flow tubes 12. Preferably, a counter-current flow type dialysis or other diffusion device may be constructed. Blood may enter inlet 30, to pass into tubular flow paths 12 of each diffusion device 10 through potting layer 32, to seal it from the dialysis solution compartment 27 in a manner analogous to current hollow fiber dialyzers. The blood then passes across second potting layer 34, and passes through outlet 36.

The above has been offered for illustrative purposes only, and is not intended to limit the invention of this application, which is as defined in the claims below.

Claims

THAT WHICH IS CLAIMED IS:

1. A diffusion membrane unit comprising a plurality of membrane fluid flow tubes, the improvement comprising: elongated flow guide member means positioned within said membrane tubes, said flow guide member means defining at least one radial fin positioned longitudinally along the longitudinal axes of said flow tubes, said radial fin defining a helical relation along its length, whereby fluid passing through said membrane tubes is impelled to flow in a helical path, for increased mixing of the liquid in said membrane tubes.

2. The diffusion membrane unit of Claim 1 in which a plurality of helical, radial fins are defined by said flow guide member means, said plurality of radial fins defining a generally constant cross-sectional angular relation to each other.

3. The diffusion membrane unit of Claim 2 in which said plurality of membrane tubes comprise a stack of sheets of laterally joined parallel membrane tubes, said sheets of membrane tubes being enclosed in a housing, with a first flow path system permitting the sealed flow of a first fluid through the fluid flow tubes, and a second flow path to permit fluid flow in sealed manner about the exteriors of said fluid flow tubes.