Heat Exchange Device With Convoluted Heat Transfer Wall

Abstract

A heat exchanger device with a convoluted heat transfer wall to define a first and second set of flow channel defining pockets having oppositely opening mouths. Each set of pocket mouths communicates with a separate fluid inlet and fluid outlet means disposed adjacent opposite ends of the pocket mouths. Sets of continuous ridges fit into the pocket mouths between each fluid inlet and outlet to provide flow channels of unvarying width by preventing transverse movement of the convolutions of the heat transfer wall, as well as to seal the pocket mouths between each fluid inlet and outlet.

Description

BACKGROUND OF THE INVENTION

The growing art of organ perfusion requires compact apparatus for heat exchange between separate fluids, and particularly for heat exchange between blood and a heat transfer fluid. The same heat exchange equipment is also useful for warming or cooling the blood of a patient during surgical operations and the like.

In Transactions--American Society for Artificial Internal Organs, Vol. 6, pp. 360-369, Esmond et al. discloses a disposable stainless steel blood heat exchanger which uses a convoluted heat transfer wall for defining two separate sets of oppositely opening pockets. Each set of pockets forms a multiple path flow conduit for a separate fluid which interleaves with the other multiple path flow conduit, providing abundant surface area for heat exchange in a very small space.

However, certain disadvantages arise with the convoluted heat exchange devices of the prior art. In particular, the individual convolutions of such a convoluted heat transfer wall are quite flexible and springy, and they are easily moved laterally back and forth in the manner of an accordion bellows. The result of this is that the flow channels within the pockets defined by the convolutions may easily vary in thickness, especially when there is a difference in the pressure of the two fluids in the separate flow channels. Hence it is difficult in the prior art devices to keep the flow channels at a desired optimum thickness for the best heat transfer and flow efficiency because of the high flexibility of the convoluted heat transfer wall. Even if support studs are intermittently provided in the pockets in the manner of U.S. Pat. No. 2,953,110, a substantial variation in the thickness of the various flow paths can still take place through accordionlike flexing, as well as through bowing of the walls between the studs when a differential pressure is present in the two flow paths. Differential pressures of up to about 10 p.s.i. are typically used in the devices for heat exchange between blood and another fluid.

Furthermore, in the prior art devices, the blood is free to migrate out of the mouths of the pockets in substantial quantity, passing into low-flow areas adjacent the pocket mouths, where it can stagnate and clot. The presence of such a large amount of clotting blood can result in the relatively rapid spread of blood clotting, and pieces of clotted blood passing downstream along with the fresh blood.

DESCRIPTION OF THE INVENTION

The heat exchange device of this invention utilizes a convoluted heat transfer wall to define first and second sets of oppositely opening pockets, with a separate fluid inlet and fluid outlet disposed adjacent opposite ends of each set of pocket mouths. Sets of continuous sealing ridges are disposed to fit into each pocket mouth between each fluid inlet and outlet. This greatly reduces transverse movement of the convolutions of the heat transfer wall, providing flow channels of unvarying width, even in the presence of the relatively high differential pressures of 10 p.s.i. or more between fluids flowing in the separate sets of pockets. Furthermore, the sealing ridges greatly reduce the migration of fluid, and most importantly blood, out of the main flow path within the pockets into stagnant areas adjacent the mouths of the pockets, thus greatly reducing the possibility of substantial amounts of blood clotting taking place in the heat exchange device.

An added advantage of the device of this invention is that it operates with a constant volume in its flow channels irrespective of moderate changes in pressure in the flow channels. This is important in surgical operations, so that the amount of blood present in the heat exchange system can be readily determined without calculation.

In the drawings,

FIG. 1 is a plan view of the heat exchange device of this invention, showing one manifold thereof.

FIG. 2 is an elevational view of the heat exchange device of this invention, showing both manifolds and a portion of the convoluted heat transfer wall.

FIG. 3 is a vertical sectional view of FIG. 2 showing details of the convoluted heat transfer wall and the general pattern of flow of separate fluids through the heat exchanger device.

FIG. 4 is a bottom plan view as indicated by line 4--4 of FIG. 3 of one manifold used in the device of this invention, showing the internal side of the manifold which presses against and secures convolutions of the heat transfer wall.

FIG. 5 is a transverse section taken along line 5--5 of FIGS. 2 and 3.

Referring to the drawings, a heat exchange device is shown in which a pair of manifolds 10, 12 bracket and sealingly secure convolutions 14 of a heat transfer wall 16. Manifolds 10, 12 can be molded from an elastomeric material, typically silicone rubber or another antithrombogenic material such as suitable formulations of polyurethane or other thermoplastic or cross-linked elastomeric materials.

Each manifold 10, 12 comprises an inlet 18, 18a, and an outlet 20, 20a, as well as a plurality of continuous sealing ridges 22, 22a, to fit into the mouths of oppositely opening pockets 24, 24a defined by convoluted heat transfer wall 16. Ridges 22, 22a provide anchoring to the individual convolutions 14 of heat transfer wall 16, preventing their lateral movement, with the resultant benefits described above. The ridges 22, 22a also are desirably proportioned and sufficiently elastomeric to provide a generally fluidtight seal at the mouth of each of pockets 24, 24a to prevent fluid, and particularly blood, from passing out of the mouths of the pockets into stagnant areas 26, 26a, in which flow through the device is substantially reduced and blood clotting may take place.

It is of course readily seen that one of the manifolds, the one which does not seal the blood flow path, is not required to perform its pocket mouth sealing function with the same urgency as the manifold sealing the blood flow path, but it is generally convenient to manufacture the two manifolds out of the same material and in the same mold.

Each manifold has outer walls 28, 28a to grip the convolutions of the heat transfer wall for both fluidtight sealing and holding the convolutions in position.

Referring to FIG. 3, a typical flow pattern of two separate fluids in two oppositely facing pockets 24, 24a is shown. One fluid, typically blood, passes into the heat exchange device through fluid inlet 18 and is spread out by plenum 30 to permit blood to flow to every pocket 24 in communication with plenum 30. Blood flow path 32 is shown in which the blood passes into each pocket 24, moves horizontally through the length of each pocket 24, being prevented from passing out of the mouths of each pocket by continuous sealing ridge 22, and then is collected in plenum 34 and passes out of fluid outlet 20.

In similar manner, a second fluid, typically a heat exchange fluid such as saline solution, enters a second fluid inlet 18a, which communicates with each of pockets 24a. Fluid flow path 36 is shown in dotted line, being behind convoluted heat transfer wall 16, with the exception of where a portion of wall 16 is broken away to expose a portion of pocket 24a to direct view. The heat transfer fluid flow path 36 runs in a similar manner through the length of each pocket 24a, and exits through fluid outlet 20a.

Each pocket 24 is in close contact with at least one and usually two pockets 24a. Thus, as the blood passes through pocket 24 and heat exchange fluid through pockets 24a, there is a heat transfer from one fluid to the other through the convoluted wall 16 without any mixing of the two fluids.

Generally, the heat transfer fluid is brought from a large fluid source in which the temperature is externally controlled as desired, and the two fluid flow rates controlled so that the blood has achieved the desired temperature by the time it reaches fluid outlet 20.

The ends of convoluted heat transfer wall 16 are potted with sealant 35 to prevent fluid leakage from the ends of pockets 24, 24a. Such sealant is typically an organosilicon room temperature vulcanizing elastomer of a type which is readily commercially available. The areas between outer lateral walls 28, 28a of each manifold and convoluted heat transfer wall 16 are also potted with linear beads 37 of sealant to prevent fluid leakage. However, a gap is left between sealant beads 37, exposing part of convoluted wall 16 to the exterior, to further reduce the possibility of seepage of fluid from one flow path to the other.

To provide additional anchoring of the convolutions of wall 16, and also to accommodate the receiving and holding of sealant 35, ridge extensions 38 are provided for sealing fit into the ends of the mouths of pockets 24, 24a. Ridge extensions 38 are beveled outwardly as shown in FIG. 3 to receive the sealant. The ridge extensions and sealant 35 firmly seal the ends of manifolds 10, 12 to the ends of wall 16, preventing any undesirable lateral "play" between them, and preventing accidental removal of the manifolds.

The flow of the two fluids through the heat exchanger device of this invention is shown to be countercurrent in nature, which is the preferred technique, but it is contemplated that cocurrent flow can also be used, in which the two fluids flow in the same direction, if desired.

Each inlet 18, 18a and outlet 20, 20a has a flange 40 defined about its end. This permits connection with another flanged tube in order to connect the heat exchange device of this invention with organ perfusion equipment, a heat exchange fluid source, blood conduits, or any other apparatus as desired. Flanges 40 permit the connection to another flanged tube by any connector device desired, such as the device defined in U.S. Pat. No. 3,456,965.

The face of convoluted wall 16 which is intended for contact with blood is typically coated with a thin silicone resin or elastomer coating, to render wall 16 antithrombogenic.

The above disclosure is for illustrative purposes only, and not for purposes of limitation, the invention of this application being defined in the claims below.

Claims

That which is claimed is:

1. A heat exchanger device which defines a heat transfer wall of convoluted shape to define a first set and a second set of flow channel defining pockets, the mouths of the pockets of the first set opening in a direction opposite to the mouths of the pockets of the second set, a fluid inlet and a fluid outlet disposed adjacent opposite ends of the pocket mouths of each of said first and second sets, and sets of continuous sealing ridges fitting into said pocket mouths between each said fluid inlet and outlet to provide flow channels of unvarying width by preventing transverse movement of the convolutions of said heat transfer wall, and to seal said pocket mouths between each said fluid inlet and outlet.

2. The device of claim 1 in which each fluid inlet, fluid outlet, and set of continuous ridges communicating with a single set of pocket mouths are defined by a unitary, elastomeric manifold fitting over each set of pockets.

3. The device of claim 2 in which the ends of said convoluted heat transfer wall are potted with sealant to prevent fluid leakage from the ends of said pockets.

4. The device of claim 3 in which each said manifold has separate ridge extensions at the ends thereof for sealing fit into said pockets, said ridge extensions being beveled outwardly to receive said sealant.

5. The device of claim 4 in which the outer lateral walls of said manifolds are sealed to said convoluted heat transfer wall with beads of sealant which are spaced from each other to expose portions of said heat transfer wall between said sealant beads to the exterior.