EP0600451A1 - Heat exchanger - Google Patents

Abstract

The heat exchanger according to the invention has a tube 1 through which the first medium A flows and in which a coil (serpentine coil) 4 is coaxially arranged. A drive shaft 9 which is mounted in bearings 10, 11 at the ends of the tube 1 and can be driven at a variable speed and, as the case may be, with a reversible direction extends along the axis 8 of the tube through the entire tube 1. The drive shaft 9 supports a rotor blade 13 which is of smaller diameter than the inner diameter of the coil 4 and extends essentially over the entire length of the coil 4. The rotor blade 13 is preferably shaped in three dimensions in the manner of a conveyor vane, with the result that in addition to the motion circling around the axis 8 of the tube the medium A is also imparted a direct axial conveying component. Even in the case of a compact design, these features yield a high-capacity (powerful) heat exchanger which can be particularly well adapted to changing operating conditions. <IMAGE>

Description

The invention relates to a heat exchanger as described in the preamble of claim 1.

Such a heat exchanger with a tube and a coil arranged concentrically in this tube is known (AT-B-373 058). The tube is surrounded by a jacket tube, so that three flow paths are formed, a district heating medium flowing through the coil, the central heating water in the tube being heated, while hot water intended for consumption is heated in the jacket tube.

The heat transfer by means of a pipe coil is comparatively effective because the heat exchange takes place through the entire pipe surface of the coil, which is immersed in the medium flowing through the pipe. Performance losses can occur, however, if one of the two media involved in the heat exchange tends to form deposits, as is the case, for example, with the thermal use of various wastewater flowing through the pipe on the outside of the pipe coil.

Furthermore, although the medium flowing through the coil has a comparatively long helical flow path, this does not apply to the other medium flowing essentially axially through the tube. For this reason, a comparatively large pipe length is often required to solve a specific heat transfer task. The long pipe contradicts but the pursuit of compact, yet powerful heat exchangers that are required in the most diverse areas of technology.

Another deficiency of the known heat exchanger is that it is designed for certain operating conditions and has no possibility of adaptation if these conditions change, for example fluctuations with regard to the throughput quantities and / or the temperatures of the media, in particular when the heat supply fluctuates, that should be used by means of the heat exchanger.

It is now known to provide in a heat exchanger consisting of an inner tube and a jacket tube in the inner tube a rotating device with a drive shaft running along the tube axis, which carries a helical wing and protruding radially beyond this, which slide over the inner circumferential surface of the inner ear and here ensure that the boundary layer that interferes with heat transfer is detached (FR-A-1 205 082).

By means of this rotation device, not only is the formation of a boundary layer counteracted, but at the same time the flow path of the medium in question through the inner tube is lengthened by superimposing a movement about the tube axis on the axial flow, so that the medium flows in an approximately helical manner. However, this does not apply to the other medium that flows through the ring channel between the inner tube and the jacket tube. Therefore, there are only limited possibilities in this known design to increase the heat exchanger performance in connection with a compact design. The same applies to the adaptation of the heat exchanger performance to special operating conditions, although a variable rotational speed of the drive shaft is already provided.

Finally, it is also known - likewise in the case of a coil-less heat exchanger comprising an inner tube and a jacket tube - to provide both media with a helical flow path, for which purpose spiral-shaped dividing walls are installed both inside the inner tube and in the annular space between the inner tube and the jacket tube, which unite both media delimit helical flow channel, which if necessary Use of several parallel partitions can also be carried out in multiple courses (DE-A-34 43 085).

In this way, long flow paths can be achieved for both media with a comparatively short overall length, but the reduced overall length also means a reduction in the area through which the heat has to be transmitted. In addition, contamination with deposits or their removal is particularly critical in this solution. Finally, there is also no possibility of adapting the heat exchanger performance to changing circumstances.

The invention has for its object to provide a heat exchanger which brings high heat transfer performance with comparatively small dimensions, is also suitable for use with at least one possibly even very dirty medium and can also be adapted to changing operating conditions.

This object is achieved with a heat exchanger as described in claim 1.

Appropriate refinements and developments of the heat exchanger according to the invention result from the subclaims.

In the heat exchanger according to the invention, a rotating device with a rotor blade is provided which does not move like a scraper over the inner wall of the tube but is arranged at a large radial distance from this inner wall within the coil, that is to say it has a diameter smaller than the inside diameter of the coil. Accordingly, the annular space between the coil and the tube is free of rotating parts. The drive shaft can preferably be driven at a variable speed. A circumferential flow is superimposed on the axial flow through the pipe, which flow can thus be selected and regulated to be stronger or weaker by appropriate control of the drive device.

In this way, several useful effects for heat exchange can be achieved. The circumferential flow not only flushes the coil of solids, it also largely removes the inner circumferential surface of the tube Keep deposits free. As a result of the direct action of the rotor blade only on the central region of the tube volume, in connection with the applied centrifugal force flow, radial mixing is achieved in particular over the flow cross section, which improves the heat exchange through the coil. Furthermore, the medium receives a largely helical flow path due to the circumferential flow superimposed on the axial flow through the pipe, so that there is a comparatively long contact path in relation to the pipe length. For these reasons, it is possible to achieve high-performance heat transfer with a comparatively short or compact design.

A particular advantage is that the heat exchanger can be operated with a medium flowing through the tube, which is comparatively heavily soiled and loaded with substances that tend to adhere. In this context, it must be taken into account that between the coil and the tube there remains a ring cross-section free of the rotor blade, that the contaminants are mainly conveyed into this ring area by the applied centrifugal action, since there is a passage distance between the individual turns of the coil, and that a Correspondingly strong circumferential flow ensures that substances do not stick to the smooth inner circumferential wall of the tube. In conjunction with a comminution device for solids driven by the drive shaft, almost any wastewater can thus be passed through and used for thermal purposes.

With all these advantageous effects, it must be taken into account that, if necessary, they can be reinforced by the rotor blade being rotated faster, that is to say more energy being introduced. Accordingly, not only can a high heat transfer capacity be achieved, but rather it can be adapted to the respective circumstances by operating the heat exchanger accordingly. In the case of critical wastewater, this cleaning effect can additionally be improved by flushing out by adding suitable solids to the wastewater before it enters the pipe, which are thrown by the rotating device both onto the pipe coil and onto the inner circumferential wall of the pipe and thus to remove any buildup to lead.

Another advantage results from the interaction of the rotation device with the coil. Due to the helical course of the pipe coil, the circumferential flow caused by the rotating device is deflected axially (in the conveying direction through the pipe), and more so with increasing rotation. This effect can be used to influence the throughput. The throughput can even be reduced to zero conveying if the rotating device is driven with the appropriate direction of rotation and the required speed.

On the other hand, it is also possible to influence the conveyance through the tube in that the rotor blade is designed as a conveying wing and / or the drive shaft is equipped with a separate conveying wing.

The de-facto switching off of the heat exchanger in the sense of the aforementioned zero delivery is expediently carried out in connection with an overflow weir, for example formed by the upper end of the vertically arranged tube, which is already overcome with a (minimal) delivery effect of the rotor blade or delivery vane, but otherwise prevents flow through the tube.

The advantages of the heat exchanger capacity control described above are obvious. It enables adaptation to changing operating conditions and can be used in particular in the case of a packet-shaped heat exchanger arrangement with several corresponding heat exchangers with tubes through which flow flows in parallel or in series, in which case individual or groups of heat exchangers can then be shut down or switched on.

Obviously, the heat exchanger according to the invention can be controlled on the basis of various control criteria to be observed. For example, an adaptation can be made to the heat supply determined by the inlet and the temperature of the medium flowing through the pipe and / or to the heat or cooling requirement of a consumer who is connected via the other medium. Corresponding circuits are familiar to the person skilled in the art and therefore do not require any special explanation.

Fig. 1 und 2

einen stehend angeordneten Wärmetauscher in einer Grundausführung im Längsschnitt bzw. im Querschnitt;

Fig. 3 und 4

den um eine Zerkleinerungseinrichtung ergänzten Wärmetauscher im Längsschnitt bzw. im Querschnitt;

Fig. 5 und 6

einen Wärmetauscher wie in Figuren 3 und 4, jedoch mit einem gesonderten Förderflügel und mit einem durch ein Mantelrohr gebildeten dritten Strömungskanal im Längsschnitt bzw. im Querschnitt;

Fig. 7 und 8

einen ähnlichen Wärmetauscher mit einem Wellrohr und einem Mantelrohr im Längsschnitt bzw. im Querschnitt und

Fig. 9 und 10

einen Fig. 1 und 2 vergleichbaren Wärmetauscher, jedoch in liegender Anordnung und mit einer Umgehungsleitung.

Several exemplary embodiments of the invention are explained in more detail below with the aid of schematic drawings. Show it:

1 and 2

a standing heat exchanger in a basic version in longitudinal section or in cross section;

3 and 4

the heat exchanger supplemented by a comminution device in longitudinal section or in cross section;

5 and 6

a heat exchanger as in Figures 3 and 4, but with a separate conveyor wing and with a third flow channel formed by a casing tube in longitudinal section or in cross section;

7 and 8

a similar heat exchanger with a corrugated tube and a jacket tube in longitudinal section or in cross section and

9 and 10

a Fig. 1 and 2 comparable heat exchanger, but in a horizontal arrangement and with a bypass line.

The heat exchanger according to FIGS. 1 and 2 has a tube 1 (container) with a feed line 2 and a discharge line 3 for a liquid first medium A. A pipe coil 4 with spaced turns 5 and a feed line 6 and a discharge line 7 for a liquid second medium B is arranged concentrically in the pipe 1. As shown, the coil 4 is arranged concentrically in the tube 1 closed at the end.

A drive shaft 9 extends through the tube 1 along the tube axis 8 and is supported in bearings 10 and 11 at the ends of the tube 1. The drive shaft 9 is led upwards out of the upright tube 1 and provided with a rotary drive device 12. This makes it possible to drive the drive shaft 9 with a variable speed and preferably also with a reversible direction of rotation.

The drive shaft 9 carries a rotor blade 13 essentially over its entire length in the region of the pipe coil 4. This is designed as a conveying wing, as indicated in FIG. 1 by the curved course of a peripheral edge, so that the rotor blade 13 does not only hold one of the medium A in the pipe 1 movement around the pipe axis 8 but also a - albeit comparatively small - axial movement through the pipe 1.

The heat exchanger according to Figures 3 and 4 largely corresponds to the above-described design, so that the same reference numerals are used for the same parts and the description is not repeated.

In contrast to the embodiment according to FIGS. 1 and 2, a comminution device 14 is provided in FIGS. 3 and 4, which has a knife 15 (percussion mechanism) fastened under the rotor blade 3 to the drive shaft 9, which cooperates with counter knives 16 and 17, which act on the tube 1 are attached and project radially inward slightly offset axially to the knife 15.

The heat exchanger according to FIGS. 5 and 6 also largely corresponds in its design to the two previously described embodiments, so that again the same reference numerals are provided for the corresponding parts and a renewed description is dispensed with.

The difference compared to the embodiment according to FIGS. 3 and 4 is that instead of a spatially deformed rotor blade 13 in order to achieve the conveying effect, a flat rotor blade 18 is provided which extends in an axial plane and thus does not exert a direct axial conveying effect on the medium A. . For this reason, a separate conveyor wing 19 is provided, which is arranged between the rotor blade 18 and the comminution device 14 and is fixedly connected to the drive shaft 9.

Furthermore, a jacket tube 20, which surrounds the tube 1 at a radial distance, is provided with an inlet 21 and an outlet 22 for a liquid third medium C. In the annular space between the tube 1 and the casing tube 20, a helical partition 23 is arranged, which has a helical shape Flow channel 24 delimits between the tubes 1 and 20 and gives the medium C a helical flow around the tube 1. The medium C also flows in countercurrent to the medium A within the tube 1 as the flow arrows shown illustrate.

According to the representation in Figure 5, the partition 23 is wound with a constant pitch. If the medium C undergoes a progressive change in volume within the jacket tube due to condensation or evaporation, it is advisable to take this into account accordingly by changing the gradient of the partition 23.

Possibly. it is possible, instead of the third medium C, to pass the second medium B flowing through the coil 4 through the jacket tube 20, in which case the flow paths through the coil 4 and through the jacket tube 20 can be connected in parallel or in series.

The heat exchanger according to FIGS. 7 and 8 likewise has three flow paths and its function largely corresponds to that of the embodiment according to FIGS. 5 and 6, but a conveying rotor blade 13 is provided and, accordingly, the separate conveying vane 19 is missing. Likewise, no shredding device 14 is shown.

The difference from the embodiment according to FIGS. 5 and 6 is that instead of the smooth tube 1, a corrugated tube 24 is provided, which at the same time replaces the helical partition 23. In this case, the jacket tube 20 lies against the helical outer corrugation line of the corrugated tube 25, so that in turn a helical flow channel 26 is present between the jacket tube 20 and the corrugated tube 25.

The heat exchanger according to FIGS. 9 and 10 largely corresponds to the heat exchanger of FIGS. 1 and 2, which is why the corresponding reference numerals are used again and there is no further description.

The lying arrangement of the tube 1, which is supported on supports 27 and 28 on the ground, differs. The tube 1 is on its upper side with a feed line 29 and a discharge line 30 Mistake. Furthermore, a bypass line 31 is connected to the underside diametrically to the feed line 29, which runs outside the tube 1 and is merged with the discharge line 30 as shown.

In this version, a more or less large portion of the resulting medium A can be led through the bypass line 28, which consequently does not participate in the heat exchange. These proportions can be controlled in the desired manner by means of the variable conveying action of the rotor blade 13 or, if appropriate, also via a separate conveying vane (not shown in FIGS. 9 and 10), possibly even such that the entire medium A flowing through the bypass line 31 and any Heat exchange is prevented. Ventilation can be provided in the overhead discharge line 30, in order to prevent flow through the pipe 1 even when the drive shaft 9 is at a standstill without the flow of the medium A as a whole coming to a standstill.

Claims (15)

Heat exchanger with a tube (1, 25) through which the first medium (A), in particular wastewater, and a tube coil (4) through which the second medium (B) flows, which is arranged coaxially within the tube (1, 25), characterized in that that within the coil (4) a rotating device (9, 13, 18) is arranged, which has a coaxial to the coil (4) drive shaft (9) and at least one rotor blade (13, 18) which the first medium (A) at Flow through the tube (1, 25) gives a circular motion about the tube axis (8). Heat exchanger according to claim 1, characterized in that the direction of rotation of the rotation device (9, 13, 18) corresponds to the winding direction of the coil (4) such that the orbiting first medium (A) due to the slope of the coil windings (5) in the conveying direction through the Pipe (1, 25) is deflected. Heat exchanger according to claim 1 or 2, characterized in that the rotor blade (13) is designed as a conveyor wing. Heat exchanger according to claim 1 or 2, characterized in that the drive shaft (9) carries a conveyor wing (19) in addition to the rotor blade (13, 18). Heat exchanger according to one of claims 1 to 4, characterized in that the drive shaft (9) carries a comminution device (14) in the inflow region of the tube (1). Heat exchanger according to one of claims 1 to 5, characterized in that the drive shaft (9) can be driven at a variable speed and / or direction of rotation. Heat exchanger according to one of claims 1 to 6, characterized in that the tube (1, 25) is surrounded by a jacket tube (20), the annular space between the tube (1, 25) and the jacket tube (20) parallel or in series the second medium (B) flowing through the coil (4) or a third medium (C) flows through. Heat exchanger according to claim 7, characterized in that the annular space between the tube (1, 25) and the jacket tube (20) has at least one helical flow channel (24, 26). Heat exchanger according to Claim 8, characterized in that the tube is a helical corrugated tube (25), on the outer corrugation line of which the jacket tube (20) bears. Heat exchanger according to claim 8, characterized in that the or each helical flow channel (24) is formed by a helical partition (23) between the tube (1) and the jacket tube (20). Heat exchanger according to one of claims 7 to 10, characterized in that a mixing device is assigned to the annular channel between the tube (1, 25) and the jacket tube (20). Heat exchanger according to Claim 11, characterized in that the mixing device is formed by the casing tube (20) which has an elliptical cross section, for example, which deviates from the circular shape. Heat exchanger according to one of claims 1 to 10, characterized in that a bypass line (31) parallel to the pipe (1, 25) is provided for the first medium (A) and the throughput shares through the pipe (1, 25) and through the bypass line (31) can be changed by means of a conveyor (13, 19). Heat exchanger according to one of claims 1 to 13, characterized in that it is combined with at least one further corresponding heat exchanger in a row or parallel arrangement. Heat exchanger according to claim 13 and claim 14 in parallel arrangement, characterized in that the heat exchangers are arranged in a common container which forms the bypass line.

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