EP0232231B1

EP0232231B1 - Heat exchanger particularly suitable for use for recovery of heat fron wet gases

Info

Publication number: EP0232231B1
Application number: EP87830043A
Authority: EP
Inventors: Armando Orsi
Original assignee: FONDERIE E OFFICINE SAN GIORGIO PRA SpA
Current assignee: FONDERIE E OFFICINE SAN GIORGIO PRA SpA
Priority date: 1986-02-07
Filing date: 1987-02-02
Publication date: 1990-08-08
Also published as: IT1204157B; DE3764101D1; IT8612423A0; GR3001045T3; EP0232231A1; ES2018048B3

Description

The subject-matter of this invention relates to a plate heat exchanger particularly well-suited for the recovery of heat from wet gases comprising the features as indicated in the precharacterizing part of claim 1.
Such a plate heat exchanger is known from FR-A-2 523 287. This heat exchanger discloses impressed plates which are assembled either in the same position or in the opposite position, it being not clear which of the two positions is preferable.
In any case, said specification, does not specify how the sealing gaskets should be positioned, nor which of the various possible solutions is considered best, and for what reasons.
According to Swiss Patent 332971 it is known to place the plates of the plate heat exchanger in such a way that all impressions face into the same direction.
The said Swiss Patent, however, does not provide for a homogeneous sealing of the gasket, as in some case the gaskets are inserted between the impressions facing into the same direction of adjacent plates (see figs. 8 and 9), whereas in other cases the gaskets are not inserted between an impression of a first plate and a plane surface of a second adjacent plate (see figs. 4, 7 and 12).
Consequently, when the gasket is pressed perpendicularly to the plate plane, the transversal expansion of the gasket is not uniform along its entire periphery. The required locking effort is therefore greater than the minimum effort required to obtain an absolutely uniform axial pressure and transversal expansion throughout the gasket periphery.
It is the object of the invention to simplify the gas/liquid heat exchanger such that the plates can be assembled easily and that only a limited number of plates are necessary.
In accordance with the invention, this object is solved by the features in that the metal plates having the two opposing openings are assembled such that the impressions face into the same direction and that the plates are separated alternately by a pair of the round gaskets which surround the openings in one case defining space between the plates for the passage of the wet gases and by the closed perimetrical gasket to form a sealed compartment in the other case.
In its preferred use as a thermal recuperator, the exchanger according to the invention is particularly well-suited for use in boilers for domestic heating purposes; in this case the heat is recovered from the fumes, in the form of sensitive heat and latent heat, at temperature levels at which in traditional boilers it is normally lost.
Each plate is suitable equipped with V shaped grooves, positioned diagonally. According to the invention, the V shaped grooves of one plate are crossed with those of the next plate, so as to favour the turbulence of the fluids which come into contact with these plates.
The invention is more fully described with reference to the accompanying drawings in which:

figure 1 is an exploded view of the exchanger according to the invention, in a preferred form of embodiment;
figure 2 shows a front view, schematic and partial, with some parts omitted, of the exchanger shown in figure 1;
figure 3 shows an enlarged section, on a secant plane parallel to the plane of projection of figure 2, passing through the plane of symmetry of the exchanger and limited to its lower part; for the sake of simplicity only four plates according to the invention are shown in figure 3, as this is the smallest number possible to implement the exchanger, although in practice this number will always comprise a few dozen;
figure 4 is a front view of a plate of the exchanger according to the invention; this front view is projected on a plane perpendicular to the plane of projection of the front view of the whole exchanger as per figure 2.

With specific reference to figure 1, the heat exchanger according to the invention is formed by a series of adjacent plates 10 made by pressing thin metal sheeting. The exchanger is also equipped with two very thick and stiff end-plates 20.
The series of pressed metal plates 10 and two end-plates 20 is held together by four stay-bolts 24 which pass through corresponding holes 13 and 23 made respectively in the printed metal plates 10 and in the two end-plates 20.
Each printed metal plate 10 has an approximately rectangular shape, and near to its two short sides it has two large holes 11 and 12, which serve as openings for the passage of the water to be heated. Each of the two end plates 20 is fitted with one further hole only, numbered respectively 21 and 22, located in positions corresponding to holes 11 and 12 respectively of the pressed metal plates 10.
Each printed metal plate 10 has a continuous impression, with a practically V shaped transverse cross-section, which surrounds uninterruptedly both the two holes 11 and 12 and the outer contour of the plates 10. This impression is therefore formed by a pair of circular impressions 31 surrounding the two holes 11 and 12 and two elongated impressions 32 which join said two circular impressions 31.
The impression gives rise to a rib on one face of the plate, and to a corresponding groove on the other face: the impression is of course obtained by pressing.
In assembling the series of pressed metal plates 10, the impressions are all made to face in the same direction, as shown in figure 3, so that the impressions of adjacent plates fit partly into one another. The impressions 31 are made so that circular gaskets 41 fit into them, gaskets which create between the openings 11 and 12, the headers through which the water to be heated passes.
These circular gaskets 41 are alternately positioned between pairs of adjacent plates 10: that is to say between the first and second, between the third and fourth, between the fifth and sixth plates and so on. More closed gaskets 42 occupy the impressions 32 and the outer edge of the impressions 31, following approximately the contours of the plates 10.
These gaskets 42 are alternated with the gaskets 41 and are therefore positioned between the second and third, between the fourth and fifth plates and so on, as shown in figures 1 and 3.
Between the pairs of plates separated from one another by means of the circular gaskets 41 a meatus 51 is thus created, in which a current of fumes to be cooled can pass.
On the other hand, the water passing through the openings 11 and 12 is free to circulate between the pairs of plates 10 separated instead by the perimetrical gaskets 42.
There is therefore a cross-flow of the primary fluid consisting of the fumes to be cooled and the secondary fluid consisting of the water to be heated.
In order to increase the turbulence of the flow of the two fluids coming into contact with the surfaces of the plates 10, these have on them parallel diagonal impressions having a substantially triangular shape, identified by number 14.
These diagonal impressions or folds 14 are suitably inclined by about 45° as compared to the plane of symmetry of the exchanger and these impressions lie in opposite directions on contiguous plates, as shown in figure 1.
In order to achieve a condition of even compression for the whole development of the perimetrical gaskets 42, it is necessary to insert spacers in the meatus 51 in which the current of fumes to be cooled passes.
As a rule these spacers are not necessary in the meatus 52 sealed by the perimetrical gaskets 42 and in which the water to be heated circulated.
These spacers may be made in different ways. According to the form of embodiment illustrated in figure 1, same may consist of thin metal wires 53 bent into coils.
According to the form of embodiment illustrated in figure 3, these spacers may consist of transverse impressions 54, positioned alternately on the plates 10.
The above descriptions and illustrations provide a practical and efficient condenser, particularly simple to build and assemble.

Claims

1. Plate heat exchanger for the recovery of heat from wet gases formed by a series of pressed metal plates (10) suitably spaced and secured together by means of stay-bolts (24) between two stiff end plates, (20), these metal plates (10) having opposing openings (11, 12) surrounded by a corresponding closed impression (31), two side impressions (32) which follow the side perimeter of these plates (10) and which end into said two closed impressions (31), the plates (10) being spaced apart and sealed to form compartments by two different closed gaskets (41, 42) one circular gasket (41) which fits into the impressions (31) which surround the openings (11, 12) and one perimetrical gasket (42) which can be positioned into the composite closed perimetrical impression (31,32) formed by said two side (32) impressions and by a portion of said two closed impressions (31), characterized in that the metal plates (10) having the two opposing openings (11, 12) are assembled such that the impressions (31, 32) face into the same direction and that the plates (10) are separated alternately by a pair of the round gaskets (41) which surround the openings (11, 12) in one case defining a space between the plates (10) for the passage of the wet gases and by the close perimetrical gasket (42) to form a sealed compartment in the other case.

2. Heat exchanger, according to the preceding claim, characterized in that it has diagonal impressions or folds (54), which are positioned in opposite directions in each pair of contiguous plates (10).