GB2251660A - Pumping and heat exchange system - Google Patents

Abstract

A pumping system wherein liquid is required to be heated to a certain temperature and supplied as a pulsed flow of variable stroke volume and frequency. The pumping system is of special use for pumping blood in heart assist systems. A second liquid is used for the heat exchange and for imparting the pulsed flow. Chambers (13, 23) and a heat exchanger (16) therebetween are filled with the second liquid which is warmed by a heating element (24). Pulses are applied to the second liquid by a liquid column (28) acting via a membrane (26) to cause flow to-and-fro between the chambers (13, 23) under the control of valves (18, 22). The second liquid entering and leaving the chamber (23) acts on a second membrane (14), the movement of the latter pumping the first liquid around a circuit (12, 29-36) including the heat exchanger (16). <IMAGE>

Description

PIJMPING AND HEAT EXCHANGE SYSTEM FIELD OF THE INVENTION: The invention relates to a pump Eor establishing a pulsed flow of liquid, where the volume per stroke, frequency and other parameters can be varied at will. The pumping system of the invention corn prises, according to a preferred embodiment, heat exchange means, for heating one of the two liquids flowing through the pump, to a predetermined temperature.

The pumping systen is of value for any use where a pulsed liquid flow at a predetermined frequency and temperature is required. It is of special use for in heart assist systems where it is required to maintain a pulsed flow of blood, of predeLermined volume per stroke, and where such blood is to undergo heat exchange to bring it tfi a predetermined temperature by heat exchange means contained in the system.

SUMMARY OF THE INVENTION: The invention relates to a system for establishing a pulsed flow of a certain liquid, provided preferably with means for 8 predetermined warming of the liquid to a given temperature. The system comprises a pulsating pump and a two-part split meandering path tube heat exchanger, The flow of this liquid is a pulsed manner is generated by means of a closed hydraulic circuit of another liquid, which has the addltionsl function of serving as heat source for the liquid circulating between the meandering tubes of the heat exchanger. The two liquid flows have an equal flow rate and stroke volume, and means are provided for adjusting the flow rate and heating to the volume of liquid per stroke and the frequency of each cycle.More parti cularly the system comprises a number of lnterconnected chambers, the arrangement being such that the first chamber is connected by a movable partition from another vessel which contains actuating means for a rhythmic movement of the partition said first chamber being connected with a chamber housing the split meandering tube heat exchanger via an inlet port leading to the one half of the heat exchanger, and connected to the other half of the heat exchanger via a conduit terminating in a one-way valve. The said chamber, housing the heat exchanger, is separated from another chamber by 8 partition, where the first part of the bent exchanger is connected to said further chamber via a one-way valve, and where a conduit leads from said further chamber to the second half of the heat exchanger.

Said uppermost chamber described above is connected with a pump head via a flexible membrane, and the actuation of the membrane, causes a corresponding flow of liquid through the pump head. This pump head is connected via a one way valve to the chamber of the heat exchangers, where this liquid (preferably blood) circulates via the narrow interspaces, which liquid leaves via an exit port generally diagonally opposite the entry port, from where it circulates via a heart assist device or similar system, which is not part of the invention, to be returned to the entry port of the pump head.

Thus, there are established two separate synchronized pulsed flows, of two liquids, at identical volume per stroke. In the lowereost chamber there is generally provided a thermostated heater which heats the heat-exchange liquid to a desired teznperature.

One of the features of the novel pumpiheat exchange system is the closed circuit flow of the heat exchange liquid, and the actuation of the pulsed flow by movable par tit ions, such as pistons or two flexible membranes coupled and synchronized through a liquid volume between them. In a heart-assist device generally both liquids, heat exchange medium and blood, flow through closed circuits.

When the lower membrane is moved up and down, the volume in the chamber bordering the other side of the membrane changes its volume according to the driven volume of the hydraulic fluid. This chamber is provided with one-way valves, connected with pipes, and thus the second liquid, generally blood, is subjected to a pulsed flow. Heat exchange takes place in a one-pass flow through this chamber.

When used with heart assist systems, some of the preferred parameters are about as follows: the water is heated in its container to 400C, and this is the hottest temperature reached by the tubular heat exchanger through which this water circalates; the other liquid, blood, enters at about 324C and 1 eaves the heatexchange chamber at a temperature not exceeding about 38to; The water pumped by the piston circulates also through the "shelland-tube" heat exchanger; The water flows through the tubes which are preferably in a vertical position in the said chamber, while the blood flows around these in a diagonal direction from entrance port to exit port, via narrow spaces between heat exchange tubes.

According to a preferred embodiment, for use with heart assist systems, a pumping frequency of about 90 per minute is used, with each stroke output being of the order of about 30-50 milliliters.

The velocity of intake and outflow need not be identical, and if desired, can be varied at will.

The spatial position of the entire system is of no significance.

The invention is illustrated by way of example with reference to the enclosed schematical drawing, not according to scale, which is a longitudinal partial section through a pumping system of the present invention.

The pulsating flow heat-exchange system according to a preferred embodiment of the invention comprises in combination an elongated chamber 11, an upper vessel 12 which is the pumping head, and a lower vessel 13, which upper vessel 12 is separated from chamber 23 by membrane 14, and from chamber 11 by partition 19, whereas the chamber 11 is separated from lower vessel 13 by partition 15, do fining a lower vessel 13. Inside chamber 11 there is provided a multi-tube heat exchanger 16 with tubes defining a meandering circuit which consists of a leEt-hand part 17 connected via valve 18 with vessel L3, and tube 27 to the interior Of 23. The right hand side 20 of the tubular heat exchanger 16 is connected via inlet port 21 to lower vessel 13 and via one-way valve 22 to upper compartment 23. Inside lower vessel 13 there is provided a heating element 24 provided with a thermostat 25, and this heats liquid A circulat:ing from this vessel via chamber ll, compartment 23, and back.

Periodic movement of diaphragm (membrane) 26 separating liquid column 28 creates a flow of the heated liquid A through the tubes of the heat exchanger. w As a result there takes place a simultaneous periodic movement of upper membrane 14 which results in a flow Of tfle second liquid, B, through the pump head, i.e. upper vessel 12. When the membrane 14 moves upwards, valve 22 opens and valve 18 closes, and warm liquid flows through inlet 21 into the meandering tubes 20 and through valve 22 into the upper reservoir 23.

When membrane 26 moves downwards, valve 22 closes and valve 18 opens, and as a result the warn liquid flows through inlet 27 Into the curved pipes 17, through valve .18 into lower vessel 13, and as a result dividing membrane 14 moves downwards.

the periodic movement of the dividing diaphragm 14 Inside the head pump 12, and the one-way valves 29 and30 generates a one-way pulsating flow of liquid B in the following manner; When the dividing diaphragm 14 moves upwards, valve 29 closes and valve.3# opens, liquid B is pushed from the pump head 12 through valve 39 and pipe 30 into the heat exchanger through inlet 321, Inside the heat exchanger compartment 11, liquid B flows over the outer surface of the warm pipes 17 and 20, absorbs heat, flows out through outlet 31 and Is pushed through pipe-344nto the system 35.When the dividing diaphragm 14 moves downwards, valve 29 opens and valve 30closes, liquid B is sucked from the system 35through the suction pipe 36 and the one-way valve 29.

As described above, there are two separate flow cycles which are generated by a single source. Liquid A fulfills two roles: a) a hydraulic liquid which generates the pump 12, and b) warm liquid to reach the desired temperature of liquid B.

The preheated hydraulic liquid A, which generates the pinnp head 12 serves at the same time as the heat source for the heat exchanger which heats the flowing fluid B propelled by the pump head 12.

The two flows are synchronized in such a way that the greater the stroke volume and flow rate, the greater amount of heat is exchanged.

Owing to the noncompressible property of liquid A, the periodic controlled movement of disphragm 26 is transferred precisely to the dividing diaphragm 14. Thus the supply of liquid B to the system 35 is controlled precisely by control of the movement source.

Claims (10)

1. A system for producing 8 pulsed flow of a liquid A at a predetermined rate, stroke volume and temperature, which includes a pulsating pump and a two-part split meandering path tube heat exchanger, where the flow of a llquid"Al is generated by a closed hydraulic circuit of a liquid B#', which serves at the same time as the heat source for the heat exchanger, where the two flows (of liquids "A" and "B", have equal rates and stroke volume and the amount of exchanged heat is automatically related to the flow rate.

2. A system according to claim 1, for producing e pulsed flow of a liquid A at predetermiend stroke volume, while warming tlle liquid by heat exchange by means of liquid ss circulating through a two-part split meandering path tube heat exchanger, which system comprises in combination means for the upward and downward motion of a partition , a lower chamber in contact with this partition, separated from a further chamber above it by another partition which houses a two-unit split tubular meandering path heat exchanger, an upper chamber above said heat-exchanger compartment, separated by a partition, in contact via a movable partition with a pump head for pumping liquid A, the tube forming half the heat exchanger being connected with the lower chamber by an inlet port for liquid B, and the upper end of the tube being connected with the upper chamber via a one-way valve, the second half of the split heat exchanger tube being connected with the upper compartment by an inlet port, the lower end of the tube terminating in a one-way valve leading to the lower chamber, movement of the lower partition resulting in a corresponding movement of the hydraulically connected upper partition, thus pumping 8 certain volute of liquid B, warmed by heating means in the lower chamber, into the upper compartment, and at a downward stroke causing the liquid to flow though the other half of the heat exchanger to the lower compartment, movement of the upper movable partition pumping a volume of liquid A identical with the moved volume of liquid B, through the upper pump and through the heatexchange compartment where it is warmed by contact with the heat exchanger and from there to the user.

3. A system according to claim 1 or 2 where liquid A is a hydraulic fluid, water, or saline.

4. A system according to claims 1 to 3, where liquid B is blood or a blood substitute.

5. Asystem according to any of claims 1 to 4, where liquid R is brougt from an initial temperature of about 32 C to about 38 C.

6. A system according to any of claims 1 to 5, where the user subsystem is a heart assist device.

7. A system according to any of claims 1 to 6, where means are provided for individually adjusting the upwards and the downward strokes of the liquid column.

8. A system according to any of claims 1 to 7, where the materials which are in contact with liquid B are compatible with blood.

9. A system according to any of claims 1 to 8, in portable form

10. A heat-exchange pulsed pumping system for pumping a liquid in a predetermined pulsed manner and for bringing this liquid to a desired temperature, comprising one closed circuit of this first liquid contacting the exterior of a tubular heat: exchanger and circulating through a heart assist device; another liquid, A, circu- lating in a closed circuit through two parts of such heat exchanger; after suitable heating; a reciprocating piston actuating said first liquid A via 8 flexible membrane and via said heat exhanger, actuating in a synchronous manner a second membrane, which actuates a pulsed flow of second liquid B via a heart assist system after warming up by contact with said heat system.