EP0386131B1 - Countercurrent heat-exchanger - Google Patents

Abstract

PCT No. PCT/EP88/01095 Sec. 371 Date Jun. 6, 1990 Sec. 102(e) Date Jun. 6, 1990 PCT Filed Dec. 1, 1988 PCT Pub. No. WO89/05432 PCT Pub. Date Jun. 15, 1989.A counterflow plate-type heat exchanger has heat exchange areas which are arranged at an oblique angle relative to the stack direction. This arrangement enables channels to be formed having a smaller width for the passage of fluid than the distance between the plates in the stack direction. As a result, a high rate of heat exchange can be obtained. Corresponding inflow and outflow channels are arranged on opposite lateral sides of the stack. This provides for fluid flow through the stack from one side to the other in a manner such that the entire heat exchange area is contacted by fluid. The channels narrow in the inflow direction and widen in the outflow direction in order to provide optimum flow conditions in the exchanger.

Description

The invention relates to a countercurrent heat exchanger with exchange surfaces consisting of sheets, which are arranged between inlet channels narrowing in the inlet direction and outlet channels widening in the outlet direction.

With heat exchangers, also with countercurrent heat exchangers, the problem arises that heat exchange takes place only in the vicinity of the surfaces of the heat exchanger. For this reason, heat exchange takes place only within a relatively small range, namely within the boundary layer thickness. The medium which has been cooled or heated in this way then mixes with the medium which has not been cooled or has not been heated. Since this mixing process is irreversible, the overall efficiency deterioration is significant. Because of the usual relatively large distances between the heat exchanger surfaces, the heat exchangers are then also of considerable size, which in turn leads to stability problems when the heat exchangers are to be used at high pressures.

A known heat exchanger, in which the distances between the heat exchanger surfaces are relatively small (US-A-4 042 018) is made from folded zigzag sheets. This heat exchanger is relatively complicated and has the disadvantage that the fluids do not sweep over the exchange surfaces uniformly, but instead Search for the shortest route (dashed arrows on the left in FIG. 1 of the document) so that no optimal heat exchange takes place.

The object of the invention is to provide a simple heat exchanger that is very effective.

The solution according to the invention is that the sheets are arranged in stacks of individual sheets, that the exchange surfaces are arranged obliquely to the stacking direction and that two adjacent sheets on both sides of the stack include channels that alternate on the one side drain channels and inlet channels and on the on the other side form the corresponding inlet channels and outlet channels.

Since the heat exchanger is made from stacks of individual sheets, it can be assembled from these individual sheets in various forms as required. Since the exchange surfaces are arranged obliquely to the stacking direction, the channels here have a smaller width than the distance between the sheets in the stacking direction. This gives you better heat exchange. Since the inlet and outlet channels are arranged on opposite sides of the stack, the fluids flow completely through the stack from one side to the other, so that the entire heat exchanger surfaces are covered. Since the channels narrow in the inflow direction or expand in the outflow direction, optimal flow conditions are obtained. In the rear part of the channels, where there is little flow, these channels can be smaller than in the front part, where larger amounts of fluid flow.

In order to obtain the same flow resistances everywhere, the inlet and outlet channels on one side have a largest cross section, which is equal to the flow cross section of the channels between the exchange surfaces, the channels on the opposite side narrowing to the cross section zero.

The production is particularly efficient if the heat exchanger consists of the same, but alternately composed, plates. It is therefore only necessary to produce a press for one type of sheet, which is then assembled alternately to form the heat exchanger.

In an advantageous embodiment, the channels between the exchange surfaces have a V-shaped cross section when viewed in the inflow or outflow direction. In this case, an inlet channel and the corresponding outlet channel lie opposite one another on opposite sides of the heat exchanger.

If the exchange surfaces are corrugated, the heat exchanger area is increased on the one hand. If the corrugations still touch each other, the sheets are supported against each other, which also allows the size to be reduced and thinner sheets to be selected.

If the sheets are not stacked in a straight line but are circular, a circular heat exchanger is obtained in which the media can be supplied and removed by radial fans in a particularly simple manner.

The sheets can be welded together, soldered, in particular hard-soldered.

The heat exchanger is advantageously covered with a pressure-resistant and heat-insulating layer. If it is arranged in a pressure-tight and pressure-resistant housing, the interior of which has the pressure of the flowing media, the heat exchanger can also be used at very high pressures of these media. It is only necessary to ensure through a small hole or the like that a little of the media under high pressure can get from the heat exchanger into the pressure vessel, so that pressure equalization takes place here. The high operating pressures then no longer need from the thin sheets, but only have to be absorbed by the pressure-resistant container.

• Fig. 1 im Querschnitt das Prinzip der Wirkungsweise eines konventionellen Wärmetauschers;
• Fig. 2 im Querschnitt das Prinzip der Wirkungsweise des erfindungsgemäßen Wärmetauschers;
• Fig. 3 eine besondere Art der Ausbildung der Wärmetauscherflächen;
• Fig. 4 eine Ausführungform des erfindungsgemäßen Wärmetauschers im Querschnitt entlang der Linie E-E von Fig. 5;
• Fig. 5 den Wärmetauscher der Fig. 4 im Querschnitt entlang der Linie A-A;
• Fig. 6 den Wärmetauscher der Fig. 4 und 5 in Draufsicht;
• Fig. 7 in einem Schnitt entlang der Linie B-B der Fig. 8 den funktionsfertigen Wärmetauscher;
• Fig. 8 den Wärmetauscher der Fig. 7 im Schnitt entlang der Linie C-C;
• Fig. 9 eine andere Ausführungsform des Wärmetauschers im Schnitt entlang der Linie F-F von Fig. 10;
• Fig. 10 den Wärmetauscher der Fig. 9 im Schnitt entlang der Linie D-D;
• Fig. 11 eine weitere Ausführungsform des Wärmetauschers in radialem Querschnitt entlang der Linie G-G von Fig. 12; und
• Fig. 12 einen Radialschnitt des Wärmetauschers der Fig. 10.

The invention is described below with reference to advantageous embodiments with reference to the accompanying drawings. Show it:

• Figure 1 in cross section the principle of operation of a conventional heat exchanger.
• 2 shows in cross section the principle of operation of the heat exchanger according to the invention;
• 3 shows a special type of design of the heat exchanger surfaces;
• FIG. 4 shows an embodiment of the heat exchanger according to the invention in cross section along the line EE from FIG. 5;
• Fig. 5 shows the heat exchanger of Figure 4 in cross section along the line AA.
• Fig. 6 shows the heat exchanger of Figures 4 and 5 in plan view.
• Fig. 7 in a section along the line BB of Figure 8, the functional heat exchanger.
• Fig. 8 shows the heat exchanger of Figure 7 in section along the line CC.
• 9 shows another embodiment of the heat exchanger in section along the line FF from FIG. 10;
• Fig. 10 shows the heat exchanger of Figure 9 in section along the line DD.
• 11 shows a further embodiment of the heat exchanger in radial cross section along the line GG of FIG. 12; and
• 12 is a radial section of the heat exchanger of FIG. 10th

1 shows a conventional heat exchanger, between the walls 1 of which two media 2 and 3 move in the direction of arrows 4 and 5 in counterflow. The medium 2 has an original temperature T₂, the medium 3 has one original temperature T₃. The temperature profiles in the radial direction are indicated in the figure by a curve 6. As can be seen, the temperature initially maintains the original value over most of the width a of the channels. A temperature exchange only takes place within the relatively small boundary layer with the width s. Then the cooled or warmed edge areas must first be mixed by the flow with the central areas of the flow, so that they only participate indirectly in the heat exchange, as a result of which the efficiency is reduced.

These problems no longer occur in the embodiment according to the invention according to FIG. 2. All parts of the flowing media participate directly in the heat exchange, since the width a of the flow channels is not significantly larger than the boundary layer thickness S.

If, according to FIG. 3, which shows the flow channels in plan view, not parallel walls 1 are used, but walls 1 which have a wave shape, the heat exchange surface is thereby increased. Since the corrugations e.g. touch at lines 7, the arrangement is very stable even when using thin sheets. The flow channels 8 are limited laterally; In this way, a large flow channel is broken down into several smaller ones.

In the embodiment of FIGS. 4 to 6, the heat exchanger consists of a stack of sheets 1 which are essentially V-shaped. The legs of the V are relatively close together, so that the width of the flow channels 8 is very small here. At the ends of the legs of the V there are angled sheet metal areas which delimit the inlet channels 9 and the outlet channels 10. Here, in the middle of the heat exchanger in the cutting plane EE, one above the other always an inlet channel 9 and an outlet channel 10. 5, these channels taper to the thickness zero, so that only inflow channels are open from the right in the illustration in FIG. 5, while only outflow channels 10 are open to the left.

For this reason, the one medium can be introduced on one end face at the end of one leg of the V and can be withdrawn on the same end face at the end of the other leg of the V. The same applies to the other medium. The flow pattern is shown in plan view in FIG. 6.

7 and 8, the heat exchanger of FIGS. 4 to 6 is shown, in which the individual channels 9 and 10 are still provided with connecting pieces 11. The heat exchanger 12 itself is surrounded by a heat and pressure-resistant insulating compound 13, which is enclosed by a pressure-resistant housing 14. Through pressure compensation holes, the interior of the pressure housing 14 communicates with the flowing media, so that only very low pressure is present on the relatively thin sheets 1 of the heat exchanger 12 even in cases where both media have very high, but approximately the same pressures.

In the embodiment of FIGS. 9 and 10, the actual heat exchanger surfaces are not angled, but straight. Apart from this, the conditions are otherwise essentially the same as in the embodiment of FIGS. 4 to 8, so that a detailed explanation can be dispensed with. Here too, the inflow channels 9 and outflow channels 10 alternate with one another in the cross-sectional area F and narrow toward the ends, so that a medium flows in or out at one of the four ends.

11 and 12, essentially the sheets of the embodiment of FIGS. 9 and 10 are used, which, however, are no longer stacked in a straight line but rather in a circle. This creates the flow conditions as indicated in FIG. 12. One medium can be fed to the inner ring of inlet channels 9 from the left and be withdrawn on the same side of the outer ring of outlet channels 10 '. The other medium is introduced from the outside right through the feed channels 9 'and radially removed from the inside of the channels 10. In this embodiment, radial fans can be used very conveniently for conveying the media. In the embodiment of FIGS. 11 and 12, a pressure-resistant insulation 11 and a pressure-resistant housing 14 are again provided.

The plates 1 of the heat exchangers are expediently welded or soldered to one another at the end faces at which the media enter or exit, since here one of the channels narrows to zero width, so the corresponding plates lie directly on top of one another. In this way, a very stable basic structure is obtained, in which only the remaining end faces then have to be soldered or otherwise closed, but this is also easy to achieve because of the corrugations.

Claims (10)

1. A countercurrent heat exchanger with exchange surfaces which comprise plates (1) and which are disposed between inlet passages (9, 9′) narrowing in the inlet direction and outlet passages (10, 10′) widening in the outlet direction, characterised in that the plates (1) are disposed in stacks of individual plates, in that the exchange surfaces are disposed at an inclination to the stack direction and in that on either side of the stack each two adjacent plates (1) enclose passages which alternately on one side form outlet passages (10, 10′) and inlet passages (9, 9′) and on the other side each form the corresponding inlet passages (9, 9′) and outlet passages (10, 10′).

2. A heat exchanger according to Claim 1, characterised in that, on one side, the inlet and outlet passages (9, 9′, 10, 10′) are of maximum cross-section, which is equal to the flow cross-section of the passages (8) between the exhange surfaces, and narrow to a zero cross-section on the opposite side.

3. A heat exchanger according to Claim 2, characterised in that it comprises like plates (1) but which are alternately assembled with different alignment.

4. A heat exchanger according to any one of Claims 1 to 3, characterised in that the passages between the exchange surfaces are of V-shaped cross-section, viewed in the inlet and outlet direction.

5. A heat exchanger according to any one of Claims 1 to 4, characterised in that the exchange surfaces are undulatory.

6. A heat exchanger according to any one of Claims 1 to 5, characterised in that the stacking is circular.

7. A heat exchanger according to any one of Claims 1 to 6, characterised in that the plates (1) are welded to one another.

8. A heat exchanger according to any one of Claims 1 to 6, characterised in that the plates (1) are soldered to one another.

9. A heat exchanger according to any one of Claims 1 to 8, characterised in that it is surrounded by a pressure-resistant and heat-insulating insulation layer (13).

10. A heat exchanger according to any one of Claims 1 to 9, characterised in that it is disposed in a pressure-tight and pressure-resistant housing (14), the interior of which is at the pressure of the flowing media.

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