Patent GB-1442754-A (GB)
Title: Apparatus for and method of effecting heat or mass transfer berween fluids
IPC: B01D65/08
Filed: 1973-03-29
Abstract: 1442754 Heat/mass transfer through membranes; oxygenation/dialysis of blood NATIONAL RESEARCH DEVELOPMENT CORP 19 June 1973 [28 June 1972 29 March 1973] 30288/72 and 15117/73 Heading B1X [Also in Division A5] Transfer of heat or mass between two fluids through a membrane, as applied for example to the oxygenation or dialysis of blood, is effected by means of apparatus which comprises a conduit at least partly defined by the membrane, a transverse dimension of the conduit varying, either inherently or in response to fluid pressure therein, in a regular repeating manner along the length of the conduit to provide a multiplicity of hollows in the membrane, and means communicating with the conduit for passing fluid, for example blood, through the conduit in pulsatile flow whereby rotatory fluid flow arises in the hollows. The membrane, which may be tubular, for example circular in cross-section, or at least predominantly planar, may be metallic membrane when intended for heat transfer, or may be made of silicone elastomer or polyester when intended for transfer of oxygen to or of carbon dioxide from blood or of cellulosic material or polyester when a haemodialysis membrane. The hollows may be in the form of dimples, which preferably have curved bases and conveniently are hemispherical, or in the form of furrows which extend ,across the membrane transverse, for example normal, to the general direction of fluid flow in the conduit. The means for passing fluid through the conduit in pulsatile flow may comprise at least one pump having a. chamber formed by flexible wall portions and means for deforming the wall portions to expel fluid within the chamber therefrom. The apparatus may comprise means whereby fluid passing through the conduit in pulsatile flow is pulsed in a reciprocatory manner, which means may be operable so that the backward movement of the fluid is at least half of the forward movement of the and may comprise a pump adjustable to operate at 50-180 oscillations per minute. Figures 1 and 2 illustrate apparatus which is suitable for use in the oxygenation of blood and which comprises a stack 1 of plates 2, each plate consisting of two silicone elastomer membranes 3 separated by a corrugated stainless steel sheet 4 and supported on ridges 5 thereof, thereby to define furrows 6 in the membranes and channels 7 for flow of oxygen, and being fabricated by applying silicon rubber adhesive to the ridges of the sheet when stretched, laying a membrane upon each surface of the stretched sheet, for example in one operation, and allowing the sheet to relax. The corrugated sheet alternatively may be rigid and formed, for example, from plastics material by extrusion, pressing or moulding. Sealed near and parallel to opposing edges of the unsupported surface of each membrane, for example by pressure and preferably also by adhesive are pairs of stainless steel strips 8 whereby adjacent plates are spaced one from another and membrane envelopes are formed by adjacent membranes of different plates, which adjacent membranes may be sealed one to another at the edges thereof. The stack is provided with a distribution chamber 9 for supplying oxygen to the channels. The spaces bounded by the membranes and the strips communicate, at a blood inlet end of the stack, with a forward flow pump 10 which communicates with a first non-return valve (not shown) and, at a blood outlet end of the stack, with a return flow pump 11 which communicates with a second non-return valve (not shown) communicating in turn with a further pump (not shown) communicating in turn with a third non-return valve (not shown). Each of the forward flow pump and the return flow pump, which pumps are identical, comprises a generally pyramidal outer casing 12 the apex of which is provided, as the case may be, with a blood inlet port 13 or a blood outlet port 14 communicating with the interior 15 of the casing in which are located four inflatable sacs 16 each having three edges which are sealed to the casing, the interior of each sac communicating via tubing 17 and 18 with a system (not shown) for supplying air under pressure to the sac and for venting the sac to atmosphere. The further pump may be a tubular pump, for example of the type generally disclosed in Specification 1268049, see Figure 3 (not shown). Each of the non-return valves may be a tricuspid valve, for example of the type generally disclosed in Specification 1315844, modified in that the suture ring is replaced by connection flanges located at each end of the valve. Reference is made to a simplified construction in which the forwad flow pump, the return flow pump, the first non- return valve and the second non-return valve are omitted, to a construction comprising a single blood flow channel bounded by a silicone elastomer membrane envelope and to a construction comprising three blood flow channels. Figure 4 (not shown) relates to a tubular membrane (for use in oxygenation and dialysis of blood) having a circular cross-section and hollows in the form of circumferential furrows defined and spaced by circumferential restrictons along the length of the membrane and Figure 5 (not shown) relates to a membrane assembly (for use in oxygenation of blood) comprising a circumferentially-furrowed inner tubular membrane supported on annular discs provided on the outside of an inner tubular member connected via struts to an outer tubular member on the inside of which is located a circumferentially-furrowed outer tubular membrane. Reference also is made, in respect of a construction containing a haemodialysis membrane common to a conduit for dialysis liquid, to the provision of means for pulsating dialysis liquid passing through the conduit, whereby vortex formation is induced therein, and to the provision in the conduit of an elongate helical element, for example a strip twisted about its longitudinal axis, whereby dialysing liquid passing through the conduit is constrained to follow a helical path through the conduit.