EP0449783B1 - Heat exchanger, particularly for ventilation plant - Google Patents

Abstract

The heat exchanger (10) consists of congruent planar elements (16) stacked one upon another at a distance (a) by means of inserted or integral projecting spacers. For the purpose of forming inflow cross-sections (30), these planar elements are cantered twice at right angles in the same direction on the mutually opposite sides, and turned by 90<o> to one another in each case. The cantered limbs (16') embrace the nearest planar element (16). Three of these planar elements (16) form in each case two adjacent flow ducts (34, 36) having flow directions (20, 22) intersecting at right angles. At least on the inlet side (E) of the medium flows (20, 22), the inflow cross-sections (30) are folded in for the most part without changing the external dimensions of the heat exchanger (10). The inflow cross-sections (30) remain unfolded only in the region of the edges (28) extending vertically relative to the planar elements (16). In each case, at least one adjoining planar element (16) is clamped in a sealing fashion in the longitudinal fold (24). <IMAGE>

Description

The invention relates to a heat exchanger, in particular for ventilation systems, consisting of surface elements of identical shape which are stacked at a distance from one another by means of inserted or molded spacers and which are bent twice, in each case rotated by 90 ° relative to one another, to form flow cross sections, and the bent legs encompass the closest surface element, three of these surface elements each forming two adjacent flow channels with flow directions crossing at right angles and being formed into longitudinal folds at least on the inlet sides of the media streams.

Cross-flow heat exchangers are known for the heat transfer between two flow media. If the flow media are vapors or gases, larger exchange surfaces are required due to the significantly lower heat capacity and conductivity, especially with gases compared to liquids. For example, air must compensate for its low thermal conductivity in thin layers between the exchange surfaces if good heat transfer is to be achieved. In addition, a material with a small thermal capacity and high thermal conductivity is advantageous for the exchange surfaces.

The use of known heat exchangers for ventilation systems in industry is impaired by other factors. For example, air supplied to heat exchangers often contains vaporous or solid substances that condense or deposit on the exchange surfaces. The efficiency of the heat exchanger is considerably reduced by an ever increasing insulating coating. Periodic cleaning of the heat exchanger is required, which is very time-consuming and costly for stubborn deposits.

Therefore, cross-flow heat exchangers have been proposed, which consist of foils or thin strips and can be replaced at high cost without great expense.

• Die zweifach rechtwinklig abgekanteten Enden bilden rechteckige Strömungsquerschnitte, die am Einlauf dem einströmenden Medium einen grossen Widerstand entgegensetzen. Sie haben einen hohen zeta-Wert.
• Die bei Transport und Montage exponierten Sichtkanten sind beschädigungsempfindlich.
• Die Abdichtung der sich kreuzenden Medienströme ist mangelhaft.

For example, CH-A5 610 648 describes a heat exchanger which is particularly suitable for ventilation systems and which is stacked up from individual layers which consist of corrugated elements and are separated from one another by partition walls. The manufacture of the heat exchanger is simplified in that the sealing of the individual flow paths, which run alternately crosswise to one another, takes place by ends of the intermediate walls projecting beyond the wavy elements on two opposite sides. The ends encompass the next layer of undulating elements and the subsequent partition. The encompassing ends of the then following one, that is to say the next but one layer of the corrugated elements, are pressed against the adjacent intermediate wall overlapped by them, as a result of which an adequate seal between two adjacent layers of corrugated elements is achieved. In addition to the advantages achieved compared to known embodiments, disadvantages must also be accepted with heat exchangers according to CH-A5 610648:

• The ends, which are bent at two right angles, form rectangular flow cross-sections that provide great resistance to the inflowing medium at the inlet. They have a high zeta value.
• The exposed edges exposed during transport and assembly are sensitive to damage.
• The sealing of the intersecting media flows is poor.

EP-A2 0167993 describes a heat exchanger constructed from plates, which plates are kept at a distance from one another by spacers. The edge sections of two adjacent plates are bent towards one another and closed a double edge section put together. This flanging is folded into a sealing connection, which allows the flow resistance to be reduced. The bent parts of the double edge section lie at least over one part of the width of the fold connection on both sides of the inner part in two layers one above the other. Nothing is said about how the edge area is designed with the offset flanges. The edge areas must therefore be cut out and poured out in accordance with FR-A 2449261 (FIGS. 1 and 3), which is unsatisfactory in particular from an economic and design point of view.

The inventor has therefore set himself the task of creating a heat exchanger of the type mentioned at the outset, which has a high degree of efficiency with a lower pressure drop and which offers no problems in the edge region, more robust Has visible edges and is economical to manufacture.

The object is achieved according to the characterizing part of claim 1. Special and further developing embodiments of the invention are the subject of dependent claims.

The inventive design of the longitudinal fold in the flow cross-sections with the clamped surface element (s) should not be confused with the formation of the folded edge areas of the heat exchanger, which is the subject of numerous publications.

The difference between the present invention and the known prior art is e.g. can be seen particularly well from FIG. 1 of FR, A, 2317617. The inflow surfaces, which are formed over their entire length (there designated with lamellae 10), oppose the media flow with great resistance, the bent edges are formed everywhere in a simple layer density and are therefore sensitive to mechanical impacts. According to the present application, however, the inflow surfaces, apart from the two outer regions, are folded in to form a longitudinal fold. Obviously, this means a multiple reinforcement against mechanical shocks and a significant reduction in flow resistance.

The areas of the outlet side that are once bent at right angles are also expediently referred to, instead of outflow cross sections; folded; The heat exchanger can therefore be used universally at low additional costs because the inlets and outlets can be interchanged. This diffuser in- and spouts allow extremely low pressure losses because the media can flow in or out in a laminar manner.

Several heat exchangers can be assembled in parallel and / or in series to form larger, more powerful units. In the case of heat exchangers assembled in series, preferably only the inlet and possibly the outlet of the last element have a fold, while the adjacent inner surfaces can remain unfolded.

The inflow cross-section preferably takes place on the inlet side or on the inlet and outlet side in such a way that the longitudinal fold comprises a flap folded inwards. The inlets, together with the adjacent surface element, are reinforced at least five times. This minimizes the risk of damage during transport and installation of heat exchangers.

In the edge regions formed vertically to the surface elements, which are in no way cut out according to the present invention, the flow cross sections always remain unfolded. In practice, the width of the unfolded inflow cross section corresponds at most to twice the distance between the surface elements, and preferably the width of the unfolded inflow cross section corresponds approximately to the distance between the surface elements. This width depends, among other things, on the thickness, hardness and the material of the surface elements used. The edge running vertically to the surface elements must not be kinked or otherwise damaged when folded.

It is entirely possible to fold in more than one flap from an inflow cross-section, but in practice this is usually less favorable than a flap. On the one hand, folding itself is more complicated, on the other hand, the flow resistance remains greater, without any particularly advantageous effects being able to be achieved.

As is evident from the name, the spacers primarily perform a support function which prevents the surface elements from swinging and bending at different pressures of the flow media. The exchange surface is further enlarged by the spacers.

According to a first variant, the spacers are formed from the surface elements, for example as beads, nubs, warts or the like running in the flow direction. The shaping can be carried out using various methods known per se, for example by means of deep drawing.

According to a second variant, the spacers are corrugated strips inserted into the flow channels and open in the flow direction. The functions remain unchanged. All known cross sections of corrugated strips are suitable, for example sinusoidal, sawtooth-like, rectangular or trapezoidal.

The corrugated strips are preferably inserted in at least one longitudinal fold reducing the flow cross section and are tightly clamped there. Thus, a fold with an inwardly folded flap becomes at least six parts, the mechanical stability against damage is further improved. In the case of folds formed on both sides, the corrugated strips are expediently clamped on both sides.

With respect to the longitudinal direction of the wave crests and valleys, the corrugated strips are preferably shortened compared to the surface elements or the external dimensions of the heat exchanger. In other words, the corrugated strips inserted into the heat exchanger do not extend to the folds, but are shortened, for example, by 1 to 3 cm on both sides, they essentially extend over the area of parallel surface elements.

The inserted corrugated strips can be formed in one piece, with continuous wave crests and wave troughs. This embodiment is particularly useful for heavily contaminated flow media.

The performance of the heat exchanger can be improved by staggering the wave crests and troughs one or more times. These dislocations can be varied both in number and in degree of dislocation. The greater the number of dislocations and the higher the degree of dislocation, the higher the performance for a given heat exchanger surface. On the other hand, however, because of the dislocations, the tendency for dirt deposits increases with performance. Depending on the degree of contamination of the flow media, a heat exchanger with appropriate corrugated tape is appropriate.

At least the inside of the fold can be filled with an adhesive or putty. This increases the tightness of the heat exchanger, its stability and the mechanical resistance of the edges. On the other hand, however, increased work and material costs have to be accepted, which can increase the production costs to a noticeable extent.

The outside of the inlaid fold can also be filled and coated with an adhesive or putty, which further enhances the advantages mentioned in the previous paragraph.

The surface elements and also the corrugated strips preferably consist of a 0.05-0.25 mm thick metal strip, for example strip steel, a hard aluminum alloy, brass or copper. Of course, the metallic surface elements can be coated with a thin protective layer, which, however, conducts heat well and should have a low heat capacity. The surface elements can for example painted or coated with an oxide layer in the case of aluminum.

In principle, surface elements and corrugated strips made of a plastic are also suitable, but because of the relatively low thermal conductivity, they are less suitable than the corresponding metallic components.

• der stossempfindliche Bereich ist durch Um- und Einlegen mehrfach verstärkt (fünf- bis siebenfach)
• Strömungsgünstiger Ein- und Auslauf
• niedriger Druckverlust
• hohe Leistung
• keine oder geringe Verschmutzung
• auch bei Kondensation horizontal verwendbar.

In summary, the advantages of the present invention are that the heat exchanger has the following properties:

• the shock-sensitive area is reinforced several times by repositioning and inserting (five to seven times)
• Streamlined inlet and outlet
• low pressure drop
• high performance
• little or no pollution
• Can also be used horizontally for condensation.

The heat exchanger is preferably designed for a maximum pressure difference of 1 m water column (10,000 Pa, 0.1 bar).

• Fig. 1   eine aufgeschnittene perspektivische Ansicht eines Wärmetauschers,
• Fig. 2   die Vergrösserung eines endständigen Falzes im Bereich II von Fig. 1,
• Fig. 3   eine Ansicht im Bereich einer Kante,
• Fig. 4   eine Variante eines Falzes, und
• Fig. 5   eine perspektivische Teilansicht eines Wellbandes mit Versetzungen.

The invention is explained in more detail with reference to the exemplary embodiments shown in the drawing, which are also the subject of dependent claims. They show schematically:

• 1 is a cutaway perspective view of a heat exchanger,
• 2 shows the enlargement of a terminal fold in area II of FIG. 1,
• 3 is a view in the area of an edge,
• Fig. 4 shows a variant of a fold, and
• Fig. 5 is a partial perspective view of a corrugated tape with dislocations.

The heat exchanger 10 shown in FIG. 1 is arranged in an open housing with two covers 12 and four edge-covering angle profiles 14. The lids bent in a U-shape in the edge area and the angle profiles 14 give the heat exchanger protection against deformation and mechanical damage and allow the heat exchanger to be fastened to a support and / or the heat exchangers to be connected to one another in parallel or in series.

The actual heat exchanger 10 consists of surface elements 16 stacked one on top of the other, which form the partitions or partitions. These surface elements consist in the present case of hard aluminum strips with a thickness of 0.1 mm, which are folded twice on two opposite sides and form a folded leg 16 '(Fig. 4). With regard to the stacking to form crosswise flow spaces, reference is also made to the already mentioned CH-A5 610 648.

Corrugated strips 18 are inserted between the surface elements 16, which support the surface elements 16 and improve the heat exchange. The corrugated strips 18 are inserted alternately through 90 ° into the flow channels 34, 36. For example, air shown by an arrow can emit heat to air flowing in flow direction 22 shown by another arrow when flowing in flow direction 20 through heat exchanger 10. This cross-flow heat exchanger has large exchange surfaces, formed from the surface elements 16 and the corrugated strips 18.

On the inlet sides E of the heat exchanger 10, the originally flat inflow cross sections in the visible area are compressed by folding into a longitudinal fold 24, as a result of which a diffuser inlet is formed. This does not change the outer dimensions of the heat exchanger.

In Fig. 2 the longitudinal fold 24 is shown greatly enlarged. The part of the surface element 16 which was originally folded and forms the flow cross-section 30 (FIG. 3) is designed as a flap 26 which is folded inwards. An adjacent surface element 16 and a corrugated strip 18 are clamped between this tab and the outer parts of the surface element 16. The longitudinal fold 24 formed in this way is designed as a sixfold layer, which means solid protection against mechanical damage.

The edge 28 shown in FIG. 3 and extending vertically to the surface elements 16 is essentially formed by the surface elements 16 stacked on top of one another once at right angles. These surfaces form the flow cross-sections 30, which can be seen partly from the front and partly in section. The height of the inflow cross sections 30, corresponding to the distance between the surface elements 16, is denoted by a, the unfolded width of which is denoted by b. In the present example, a and b are approximately the same size. The inlet between the longitudinal folds 24 has been significantly enlarged.

3 also shows that no special measures have to be taken in the area of the edge 28, in particular this edge area does not have to be removed and replaced by a sealing compound.

Dashed lines indicate a surface element 16 rotated by 90 °, which likewise comprises a fold 24.

4 shows a further variant of a fold 24 with a flap 26 folded inwards. The folded and folded surface element 16 is supported by a sawtooth-shaped corrugated strip 18 which is fastened in the fold 24 in a sealing manner by means of a cement compound. An adjacent surface element 16N is inserted into the fold on the same side of the flap 26.

On the other side of the tab 26 of the rectangular, inwardly folded leg 16 'of the not shown, other adjacent surface element is folded. A sevenfold fold 24 is thus formed.

With regard to the leg 16 'of a surface element 16 which is folded inwards, FIG. 2 differs in that it is trapezoidal there and is not guided into the fold 24.

The hardening putty 32 is also inserted into the fold 24 from the outside. It has no sealing function, but forms an additional strengthening and further improved protection of the fold 24 against external mechanical influences.

The corrugated strip 18 partially shown in FIG. 5 has lateral dislocations which have a length L. As a result, turbulence is increasingly generated on both sides of the corrugated strip 18 of a trapezoidal basic structure, which increases the efficiency of the heat exchanger.

With a large L, the efficiency of the heat exchanger is less high, but dirt deposits are largely prevented. In the case of a small L with dislocations formed at short intervals, the high turbulence generated results in very high efficiency.

Claims (10)

1. Heat exchanger, in particular for ventilation systems, of uniformly shaped planar elements (16) stacked at intervals (a) to each other by means of inserted or moulded spacers, where the said planar elements are folded twice in each case at 900 to each other on opposite sides to form flow contact profiles (30), and the folded legs (16′) grip the adjacent planar element (16), where in each case three of these planar elements (16) form two adjacent flow channels (34, 36) with flow directions (20, 22) crossing each other at right angles and at least on the inlet side (E) of the media flows are formed into longitudinal folds (24),
   characterised in that
   the planar elements (16) are folded twice in the same direction, the flow profiles (30) are folded in to the longitudinal folds on the outer area which remains flat, where the said folds extend to the inlet side (E) of the media flows, where in each case the adjacent folded planar element (16) is firmly clamped to seal in the longitudinal fold (24).
2. Heat exchanger according to Claim 1, characterised in that the longitudinal folds (24) comprise a tab (26) turned to the inside and formed from the flow profiles (30).
3. Heat exchanger according to Claim 1 or 2, characterised in that the flow profiles (30), starting from the edges (28), remain folded to a width (b) which corresponds at most to twice the interval (a) and preferably approximately to the interval (a) of the planar elements (16).
4. Heat exchanger according to any of Claims 1 to 3, characterised in that it is incorporated in a housing open on the inlet (E) and outlet sides with two covers (12) and angle profiles (14) covering the flow profiles unfolded in the area of the edges (28).
5. Heat exchanger according to any of Claims 1 to 4, characterised in that the spacers are formed by beads, knobs, projections or similar running in the direction of flow (20, 22) and formed from the planar elements (16).
6. Heat exchanger according to any of Claims 1 or 4, characterised in that the spacers are open corrugated strips (18) inserted in the flow channels (34, 36) and running in the direction of flow (20, 22).
7. Heat exchanger according to claim 6, characterised in that the corrugated strips (18) are retained in the longitudinal folds (24) and shortened preferably at both ends in the longitudinal direction of the wave peaks and troughs opposite the planar elements (16).
8. Heat exchanger according to Claim 6 or 7, characterised in that the corrugated strips (18) are preferably offset at short intervals (L).
9. Heat exchanger according to any of Claims 1 to 8, characterised in that the folded leg (16′) of the planar element (16) is formed at right angles and folded into the longitudinal folds (24) or is cut and not folded in a trapezium shape.
10. Heat exchanger according to any of Claims 1 to 9, characterised in that the longitudinal folds (24) are filled with an adhesive or mastic (32) at least on the inside.

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