Plate-type Heat Exchanger

Abstract

A plate-type heat exchanger for fluids, comprising a deck of separate plates with sealing means between adjacent plates which is compressed by two end pieces, each of these end pieces having the form of a short cylindrical shell with a domed end and the compressive forces being applied to the deck of plates by means of an end plate arranged in one of the end pieces and hydraulically movable in the direction of the longitudinal axis of the deck of plates.

Description

This invention relates to an improved plate-type heat exchanger for liquids or gases.

Known plate-type heat exchangers consist of a deck of rectangular or circular plates compressed between two end pieces. The plates are corrugated on the surface and are provided with holes for supplying and withdrawing the fluids to and from the spaces between the plates. The end pieces have the form of flat plates and are provided with connections for the admission and discharge of the heat-exchanging fluids. Between adjacent plates there are arranged sealing means which seal the spaces between the heat-exchange surfaces and the ducts for the fluids when the deck of plates is compressed by means of tie bolts arranged at the periphery of the plates.

A drawback of these plate heat exchangers is that only plates having a relatively small diameter or side length can be used in their construction, because the high compressive forces which must be applied to the deck of plates via the tie bolts for sealing cause bending of the plates, which becomes more and more marked as the diameter or side length of the plates in increased and readily results in leaks.

It is an object of this invention to provide a plate-type heat exchanger in which the compressive forces are distributed over the whole area of the plates as uniformly as possible in order to avoid bending of the individual plates even if the plates are relatively large. Another object of this invention is to provide a plate-type heat exchanger having all connections for the admission and the discharge of the fluids arranged on the stationary end piece in which, even in the case of large plates, the ducts for conveying the fluids from the fixed end piece to the movable end piece and vice versa can be arranged as holes in the plates without risk of leakage.

In accordance with this invention, these objects are achieved by a plate-type heat exchanger incorporating a deck of separate plates with sealing means between adjacent plates which is arranged between a fixed end piece and an end piece detachably connected with the fixed end piece via tie bolts (hereinafter called "detachable end piece"), the connections for the admission and the discharge of the heat-exchange fluids being provided on the fixed end piece and means for reversing the flow of the fluids being provided at the other end of the deck of plates, wherein each of the two end pieces has the form of a short flanged cylindrical shell with a domed end and wherein an end plate is arranged inside the detachable end piece in such a way that it is movable in the manner of a piston in the direction of the longitudinal axis of the heat exchanger, the deck of plates between the end plate and the fixed end piece being capable of being compressed hydraulically by means of the end plate by introducing a pressure fluid between the end plate and the detachable end piece. If the pressure fluid is not one of the heat-exchange fluids, the size of the end plate should be at least equal to that of the plates arranged between the end plate and the fixed end piece. If one of the heat-exchange fluids is used as the pressure medium, the end plate should be larger than the plates arranged between the end plate and the fixed end piece. In order to ensure that the ducts for conveying the heat-exchange fluids from the fixed end piece to the detachable end piece and vice versa can be arranged as openings in the plates, it is advisable for the plates to be circular in shape, the actual heat-transfer surface of each plate being surrounded by four uniformly spaced openings at the periphery of the plate for supplying and withdrawing the heat-exchange fluids to and from the spaces between the heat-transfer surfaces of neighboring plates, the outer edge of each of these openings extending for less than a quarter arc of the circumference of the plate, and each of the four areas situated between two neighboring openings being provided with an aperture, these apertures serving, in pairs, to convey the heat-exchange fluids from the fixed end piece to the detachable end piece and vice versa while bypassing the spaces between the heat-transfer surfaces of the plates.

One embodiment of a plate-type heat exchanger according to the invention will now be described, by way of example, with reference to the accompanying drawing, in which:

FIG. 1 is a schematic longitudinal section of the heat exchanger according to this invention;

FIG. 2 is a plan view of a single plate of the heat exchanger without gaskets;

FIG. 3 is a plan view of a single plate of the heat exchanger with gaskets; and

FIG. 4 is an exploded perspective view of a part of the heat exchanger body .

Referring to FIG. 1 the plate-type heat exchanger illustrated comprises a fixed end piece 10 containing pipe connections 18 for the supply and withdrawal of the heat-exchange fluids, a detachable end piece 11 provided with displacement bodies 17, circular plates 12 arranged between the two end pieces, a fixed end plate 13 located in the end piece 10, an end plate 14 provided with a seal 15 and movably arranged inside the end piece 11, and a plurality of tie bolts 16 which hold the end pieces 10 and 11 together. FIG. 2 shows a circular plate 12 in which the actual heat-transfer surface 25 is surrounded by openings 20, 21, 28 and 29 for the supply and withdrawal of the heat-exchange fluids to and from the spaces between the plates. Since the connections for the admission and discharge of the fluids to and from the heat exchanger are arranged in the fixed end piece 10, ducts must be provided in the heat exchanger for conveying the heat-exchange fluids from the end piece 10 to the other end of the deck of plates and vice versa while bypassing the heat-transfer surfaces 25 of the plates. Therefore, the openings 20, 21, 28 and 29 are arranged in such a way that their outer edges extend for less than a quarter arc of the circumference of the plate. The four areas situated between the said openings are provided with apertures 22 and 23 which, in pairs, serve to convey the heat-exchange fluids from the end piece 10 to the other end of the deck of plates and vice versa while bypassing the heat-transfer surfaces 25 of the plates 12.

FIG. 3 shows the plate 12 according to FIG. 2 with gaskets, which separate the openings 20, 21, 22, 23, 28 and 29 from each other and cause the openings 20 and 28 to communicate with the space above the heat-transfer surface 25. If plates with gaskets placed on them in accordance with FIG. 3 are arranged to form a stack in which adjacent plates are arranged at 90.degree. in relation to each other, a heat exchanger body is formed (an exploded perspective view of which is given in FIG. 4) in which the spaces between neighboring heat-exchange surfaces alternately communicate with the openings 20 and 28 and the openings 21 and 29. For the sake of simplicity, only a limited number of plates 12 and gaskets 24 are shown in FIG. 4. The fixed end piece 10 is followed by the end plate 13, which in turn is followed by alternating gaskets 24 and plates 12, the end of the heat exchanger being formed by the movable end plate 14 and the end piece 11. The paths of the heat-exchange fluids are marked by arrows; the paths of the fluids through the spaces between the heat-exchange surfaces 25 of two neighboring plates 12 are shown by arrows in the plane of the intermediate gasket.

In the embodiment according to FIG. 4, which operates on the countercurrent principle, the fluid 26 enters the heat exchanger through one of the connections 18 and passes through the hole 27 in the fixed end plate 13 into the openings 20. In the plane of the first and every second following gasket 24 part of the fluid 26 is passed through the space between the neighboring plates 12 in the direction of the arrow for heat-exchange. These partial streams leave the spaces via openings 28 and are then collected to form the stream 45 which flows parallel to the stream 26. After the two fluid streams 26 and 45 have reached the end of the deck of plates, they are reversed and then returned to the fixed end plate 13 through the ducts 22, thus bypassing the heat-exchange surfaces 25 of the plates 12; they pass through the holes 30 and 31 and are combined into one stream 26 + 45, which is discharged through one of the connections 18.

The second heat-exchange fluid 32 + 33 enters the heat exchanger through another of the connections 18. It is divided into two partial streams 32 and 33, which are passed through the holes 34 and 35 in the end plate 13 into the ducts 23. When the two streams have reached the space between the last plate 12 and the end plate 14, they are reversed and then returned as stream 36 through the openings 21 to the end piece 10. In the plane of the gasket 24 arranged immediately ahead of the end plate 14 and in the plane of every second of the following gaskets 24 part of the stream 36 is passed in the direction of the arrow through the spaces through which the first heat-exchange liquid 26 does not flow; these partial streams are collected in the openings 29 to form the stream 37 which flows parallel to the stream 36. After passing through the holes 38 and 39 in the end plate 13, the streams 36 and 37 are combined into one stream 36 + 37, which is discharged from the heat exchanger through one of the connections 18.

Sealing of the ducts 22 and 23 and of the openings 20, 21, 28 and 29 is effected by allowing a pressure medium to act upon that side of the movable end plate 14 which faces the end piece 11 so that the end plate is moved toward the fixed end piece 10, thus compressing the deck of plates and gaskets. In the embodiment according to FIG. 4, the streams 26 and 45 of one of the heat-exchange fluids are used as the pressure medium, the end plate 14 having a larger external diameter than the plates 12. For this purpose, the streams 26 and 45 pass through the holes 40, 41, 42 and 43 in the end plate 14 and fill the space between the end plate 14 and the end piece 11. Since a larger area of the end plate 14 is acted upon by fluid on the side facing the end piece 11 than on the other side, a thrust toward the end piece 10 is produced which exerts the necessary sealing force on the gaskets 24. In order to keep the liquid-filled volume of the end piece 11 small, the latter may be provided with displacement bodies 17 forming channels 19 of much smaller fluid capacity. The fixed end piece 10 and the detachable end piece 11 with their domed ends are capable of taking up much higher pressures than the disc-shaped end pieces of conventional heat exchangers.

The pressure medium to be introduced between the end plate 14 and the end piece 11 may be a fluid other than the heat-exchange fluids (hereinafter called "extraneous pressure medium"), which would have to be introduced into the end piece 11 through a pipe connection (not shown in FIG. 4). When the extraneous pressure medium is under a higher pressure than the heat-exchange fluids, the end plate 14 may have the same external diameter as the plates 12. When an extraneous pressure medium is used, reversing the flow of one of the heat-exchange fluids can only be carried out in the end piece 11 by providing in the latter fluidtight ducts for the purpose (not shown in FIG. 4). In any case, the end plate 14 is so arranged in the end piece 11 that it is axially movable, the joint between the end plate 14 and the end piece 11 being sealed by a gasket 15. The flanges of the end pieces 10 and 11 are connected by tie bolts 16 (cf. FIG. 1), which pass through holes 44 in the flanges.

During operation of the heat exchanger, the end plate 14 is mechanically stressed only by the pressure difference existing between the heat-exchange fluids, on the one hand, and the extraneous pressure medium in the end piece 11, on the other; when one of the heat-exchange fluids is used as the pressure medium, part of the end plate 14 is not stressed at all. The end plate 14 therefore need not be very thick and can be made from a material which need not satisfy any particular requirements regarding strength. When shutdowns are necessary, the pressure on the end plate 14 and the gaskets between the plates 12 can be released in a very simple manner by draining the pressure medium from the end piece 11, which favorably affects the life of the gasket. The compressive forces required for sealing the deck of plates are uniformly distributed over the whole diameter of the latter by the end plate 14 movably arranged in the end piece 11 so that when large compressive forces are applied or when plates of large diameter are used there is no risk of the plates being deformed and leaks occurring, as may easily be the case with conventional heat exchangers in which large compressive forces are applied to the edges of the plates by means of tie bolts. The tie bolts 16 shown in the drawing (FIG. 1) serve merely to firmly connect the two end pieces 10 and 11 with each other but not to apply the compressive forces to the plates 12.

In some cases it may be advantageous for the end plate 13 to be arranged in the end piece 10 in such a way that it is axially movable, as is the end plate 14 in the end piece 11.

Claims

I claim:

1. A plate-type heat exchanger for liquids or gases comprising a deck of individual, heat exchange plates and interposed gasket means, a first, domed, end member at one end of said deck, a second, domed, end member at the other end of said deck, conduit means for introduction and discharge of heat-exchange fluids on said first domed member into and from said heat exchanger, an end plate interposed between said deck and said second, end member with its peripheral edge slidably disposed inside said second, end member for pistonlike movement of said end plate in the direction of the longitudinal axis of said heat exchanger, aligned apertures in said heat-exchange plates, said gasket means being interposed between contiguous plates and defining, with respective aligned apertures, a plurality of longitudinally extending passages for flow of fluids axially through said heat exchanger, means in said second, domed, end member for communicating pairs of passages to reverse fluid flow from one passage and return it through another passage, and means providing a substantially pressure tight seal between said end plate and said second, domed end member whereby fluid pressure in the latter member moves said end plate toward said deck to compress said deck.

2. A plate-type heat exchanger as claimed in claim 1 wherein the dome portion of said second member contains displacement bodies which reduce the fluid capacity of said domed portion.

3. A plate-type heat exchanger as claimed in claim 1 wherein said heat-exchange plates are circular plates with said apertures comprising four symmetrically arranged openings near the periphery of each heat-exchange plate for supplying and withdrawing the heat-exchange fluids to and from the spaces between the heat-transfer surfaces of neighboring plates, the outer edge of each of these openings extending for less than a quarter arc of the circumference of each plate, and each of the four areas situated between two adjacent openings are provided with an aperture, these apertures serving, in pairs, to convey the heat-exchange fluids from the fixed end piece to the detachable end piece and vice versa while bypassing the spaces between the heat-transfer surfaces of the plates.

4. A plate-type heat exchanger as claimed in claim 1 wherein said plates are circular plates, the external diameter of said end plate being greater than the external diameters of said heat-exchange plates.

5. A plate-type heat exchanger as claimed in claim 1 wherein said plates are circular plates, the external diameter of said end plate being at least equal to the external diameters of said heat-exchange plates, and means for providing in said second, domed, end member a fluid pressure greater than the fluid pressure of said heat-exchange fluids.