Plate Heat Exchanger

Abstract

Heat exchange is effected through a thin plate strip having transversely extending folds which provide it with a sinuous shape, thereby forming channels extending transversely of the strip on both sides thereof for passage of the two heat exchange media, respectively. The first set of channels (those on one side of the strip) are sealed at their opposite ends, each of these channels having opposing walls which are joined together along the opposite lateral edge portions of the strip so as to form alternate folds of the strip into a continuous line along each of these lateral edge portions. The strip is sealingly and releasably connected to a surrounding casing along these continuous lines and at the opposite end portions of the strip; and when the latter is removed from the casing, the other side of the strip defining the second set of channels can be made accessible for cleaning or inspection by separating the opposing side walls of these channels like the leaves in a book.

Description

The present invention relates to a heat exchanger having a heat transferring element in the form of a thin plate strip of a uniform width, which is provided with deep transverse folds or tucks forming transverse channels on both sides of the strip for the media to be treated in the heat exchanger.

It is an object of the invention to provide a compact light-weight heat exchanger of the above-noted kind, wherein one of the two heat exchanging surfaces of the heat transferring element is accessible for inspection and/or manual cleaning.

A further object of the invention is to provide a heat exchanger of this kind, wherein the total length of fixed seals, such as welding joints or the like, is a minimum.

It is another object of the invention to provide a heat exchanger of this kind, wherein all fixed seals, such as welding joints or the like, are accessible for inspection and/or repair.

Still another object of the invention is to provide a heat exchanger of this kind which is inexpensive and simple to produce.

These objects are fulfilled by a heat exchanger according to the present invention, wherein the channels on one side of said strip are sealed at their ends (i.e., at the opposite lateral edges of the strip), as by welding, the opposing side walls of each of these channels being joined together at the lateral edges of the strip in a way such that a continuous line is formed at each of these edges by those folds of the strip which partly define the channels on the other side of the strip. The heat transferring element is sealingly connected with a surrounding casing along the said continuous lines and at the ends of the strip; and the heat transferring element is releasable from the casing so that one side of the strip will be accessible for cleaning or inspection by separation of the side walls of the channels on this side of the strip like the leaves in a book, without the need of breaking the end seals of the channels on the other side of the strip.

In a preferred embodiment of the invention, a flange is fixed by welding or the like to each of the strip edges along the respective continuous lines, these flanges forming together with the end portions of the strip a closed sealing flange, by means of which the strip is fastened between separable parts of the surrounding casing. The present invention is further described below with reference to the accompanying drawings, in which:

FIG. 1 is a sectional view of one embodiment of the new heat exchanger;

FIG. 2 is a sectional view on the line II--II in FIG. 1;

FIG. 3 is a perspective view of part of a heat transferring element of the exchanger, showing the element in one stage of its manufacture, and

FIG. 4 is a perspective view of part of such an element in a finished condition.

The heat exchanger shown in FIG. 1 comprises a casing having two parts 1 and 2, and a heat transferring element 3 arranged in this casing. The element 3 consists of a folded plate strip, the shape of which can be clearly seen in FIGS. 2 and 3, the latter showing the strip when only partially folded. As can be seen from FIG. 2, the strip 3 is provided with a series of transverse folds 12 spaced along the length of the strip to give it a sinuous shape, thereby forming a first set of channels 5 on one side of the strip and a second set 4 on the other side of the strip. These channels extend in parallel relation to each other, the channels 4 being open to the left and the channels 5 being open to the right as viewed in FIGS. 1 and 2. Each channel of the first set 5 (i.e., opening to the right) is closed at its opposite ends, that is, along the opposite lateral edge portions 3x and 3y of the strip 3. As shown particularly in FIG. 4, this closing of each channels 5 at its ends is effected by deforming the strip 3 so that opposing walls of the channel 5 converge and abut each other at the two edge portions 3x and 3y, as indicated at 14. These abutting portions 14 of the opposing walls may be welded together so as to seal the opposite ends of channels 5 along the respective lateral edge portions 3x and 3y of the strip.

As will be observed from FIG. 2, alternate folds 12 of the strip 3 (i.e., the folds at the right in FIG. 2) partly define the second set of channels 4 which open to the left. Because of the above-mentioned deformation of the strip to provide the abutments at 14 (FIG. 4), these alternate folds 12 form a continuous line at each of the opposite lateral edges 3x and 3y of the strip. Welded to such lateral edges along these continuous lines are flanges 3a and 3b, respectively (FIG. 4). The flanges 3a and 3b form with the opposite end portions 3c and 3d of the strip (FIG. 2) a closed sealing flange by means of which the heat transferring element 3 is releasably connected to the surrounding casing. As shown in FIGS. 1 and 2, this sealing flange 3a - 3d is clamped between the separable parts 1 and 2 of the casing, it being understood that these parts can be released from each other in any suitable manner.

As can be seen from FIG. 1, the part 1 of the casing has an inlet 6 and an outlet 7 for one heat exchanging medium. Since the channels 5 are closed at their ends, this medium will flow only into the channels 4, through which it will flow from the inlet 6 to the outlet 7. The part 2 of the casing forms an inlet 8 and an outlet 9 for a second heat exchanging medium, which inlet and outlet open into chambers 10 and 11, respectively. These chambers in turn communicate with all of the channels 5, since the latter are open to the right (FIG. 2). As can be seen from FIG. 1, channels 5 are covered at the right along the main part of their length by a wall 2a which is a part of the casing.

By separating the parts 1 and 2 of the casing, it is possible to have access to the heat transferring element 3. The channels 4, open to the left with reference to FIGS. 1 and 2, are then accessible for thorough cleaning by separating the respective channel walls like the leaves in a book. That is, the opposing walls of each channel 5, being joined together at the ends of the channel (FIG. 4), may be considered as a book leaf; and with the casing part 1 removed, the alternate folds 12 at the right (FIGS. 2 and 4) serve more or less as hinges which permit turning of the "leaves" so that the "book" can be opened to expose the opposing walls of each channel 4 for such cleaning.

In FIG. 3, a fragment of the heat transferring element 3 is shown. This element consists of a thin, flexible plate strip provided with folds 12 and corrugated so that it has ridges 13 on both sides. The strip is uniformly corrugated along the whole of its length, having breaks only in the areas 12 where it is to be folded. The ridges 13 of the strip 3 may be formed in many different ways. The main thing is that they cross and abut each other in the channels 4 and 5 formed on each side of the strip when it is folded. In principle, the strip could be provided with ridges extending only in one and the same direction and forming an angle with the folds of the strip. When the strip is folded, these ridges will automatically cross each other in the channels then formed. For manufacturing reasons, however, the ridges are preferably formed so that they extend symmetrically relative to the longitudinal center line of the strip.

Since the heat exchanging medium entering through the inlet 8 (with the construction according to FIG. 1) must flow into and out of the channels 5 in the transverse direction of the latter, certain problems may arise in achieving a proper distribution of the medium across the heat exchanging surface. If the channels 5 are very short, much more of the heat exchanging medium will flow, per unit of time, near the wall 2a than deeper in the channels 5, which will result in that the stream parts close to the wall 2a being less heated (or cooled) than the stream parts flowing deeper in the channels.

Included in FIG. 4 is a schematic showing of how to solve this problem. Dotted lines illustrate the paths taken by two stream parts A1 and A2 in flowing through one channel 5. By forming the corrugations in the strip or element 3 so that the ridges form a smaller angle with the longitudinal direction of the channel 5 along the path of the stream part A1 than along the path of the stream part A2, as shown at 13a and 13b, respectively, it is possible to arrange for a greater through-flow resistance for the stream part A2 than for the stream part A1. In this way, it is possible to achieve a proper distribution of the medium flowing in the channels 5. It should be noted, however, that the stream parts B1 and B2 of the second heat exchanging medium, flowing through the channels 4, will also be influenced by such a formation of the heat exchanging surfaces. The degree of increased through-flow resistance which is to be provided for the stream part A2 thus must be a compromise and be determined from case to case.

An alternative way of varying the through-flow resistance for the heat exchanging media is to make a smaller number of ridges 13 on one part of the heat exchanging surfaces than on another part of the same.

Claims

I claim:

1. In a plate heat exchanger, the combination of a heat transferring element in the form of a thin plate strip of uniform width having opposite end portions and also having transversely extending folds spaced longitudinally along the strip and providing the strip with a generally sinuous shape, thereby forming channels extending transversely of the strip on both sides thereof for passage of respective media to be treated in the heat exchanger, said channels including a first set located on one side of the strip and sealed at their opposite ends along opposite lateral edge portions of the strip, the channels also including a second set located on the other side of the strip and partly defined by alternate ones of said folds, each channel of said first set having opposing walls which are joined together at said lateral edge portions of the strip to spread opposite ends of said alternate folds into a continuous line along each of said edge portions, a flange secured to and extending from said strip element along each of said continuous lines, a casing surrounding said heat transferring element, and releasable means sealingly connecting said element with the casing along said flanges and at said opposite end portions of the strip, whereby upon release of said element from the casing said other side of the strip is accessible for cleaning or inspection by separating opposing walls of the channels of said second set like the leaves in a book, while maintaining the channels of said first set sealed at their said opposite ends.

2. A combination according to claim 1, in which each channel of said second set is open at its opposite ends along said opposite lateral edge portions of the strip, each said alternate fold forming a fulcrum about which adjacent pairs of said opposing walls are swingable away from each other.