EP0072020B1 - Open condenser - Google Patents

Description

The invention relates to a method for low-noise introduction of large amounts of steam into a flowing liquid for heating it, in which the steam is passed through heat exchange elements of a heat exchanger, in which the liquid, at least at the outlet end of the heat exchange element or elements, is guided essentially axially parallel to the latter is. Furthermore, the invention relates to a device for performing this method with a heat exchanger having heat exchange elements, in which the liquid is guided in the aforementioned manner.

According to DE-A No. 2439562, a method for heating water by means of water vapor is known, in which the water vapor is passed through an open tube bundle, past which the liquid to be heated flows parallel to the axis. The device provided for this purpose is operated or is dimensioned with regard to the length and the diameter of the tubes such that all of the water vapor is completely relaxed and condensed at the end of the tube bundle at the latest.

This method and the heat exchanger provided for it have less noise than devices in which the steam is introduced into the liquid to be heated in the form of many small steam bubbles. Nevertheless, the condensation in the known heat exchanger is still associated with considerable noise pollution. In addition, the control range is naturally limited due to the specified length of the heat exchange tubes. Finally, the construction effort is considerable, because the cooling of the steam inside the heat exchange tubes requires correspondingly large tube lengths.

The invention is therefore based on the object of finding a method of the type mentioned which operates with less noise and has a considerably larger control range with stable operation, and to provide a device for carrying out this method, the outlay in terms of apparatus being comparatively low.

As far as the method is concerned, this object is achieved according to the invention in that the steam and the liquid are exposed to such temperature and flow conditions that the emerging steam in the form of connected, stable steam columns connected to the heat exchange elements into the liquid parallel to the flow reaches in.

A device for carrying out this method is characterized according to the invention in that the heat exchange surface and the openings of the heat exchange element (s) are designed in such a way that the emerging steam in the form of continuous, stable steam columns connected to the heat exchange elements into the liquid parallel to the liquid Flow into it.

In comparison to the prior art, the principle of complete condensation within a tube bundle flowed around by the medium to be heated is deliberately deviated here by introducing the steam in the form of a coherent, stable steam column - but not in the form of small bubbles - parallel to the flow of the medium to be heated. The interface which forms between the steam column and this medium outside the tube bundle thus acts as a heat exchange surface without a partition, the steam column surprisingly dissolving after a certain distance without condensation and thus without making a lot of noise.

With changing operating conditions, the length of the steam column and thus the direct condensation surface follows these changes in a simple manner, without the stability of the steam columns suffering as a result. This results in an excellent control characteristic without the need for moving parts.

Another advantage is that the heat exchange surfaces, for example the tube bundle, can be kept relatively small, since part of the heat exchange surfaces is formed by the interface between the steam column and the medium to be heated. Both direct current and counter-current operation are possible. The disadvantage of countercurrent operation compared to direct current operation, that the condensate admixed has to be cooled with relatively warmer liquid, is offset by the advantage of the larger average temperature difference in countercurrent. If necessary, the advantages or disadvantages predominate can be calculated.

In the case of straight tubes, a particularly high packing density can be achieved, which results in a large ratio of steam exit areas to the cross-sectional area of the flowing liquid. In relation to the cross-section of the apparatus, high values are set for the direct condensation surface between steam and liquid and thus for the condensation performance.

When designing the open capacitor, a wide variety of requirements can be met depending on the material and geometry. The heat exchange elements can be cylindrical or box-shaped. A forced redirection of the liquid flow can be carried out within the bundle. In principle, it is also possible to send the liquid through the heat exchange elements and to guide the steam around the elements; guidance of the steam can thus also be achieved by means of the exchange elements charged with liquid; in this case the steam columns emerge from the jacket area and are surrounded by corresponding liquid columns from the heat exchange elements.

In order to achieve high performance, the steam must be introduced into a flowing liquid. Normally, a pump and corresponding guide elements around the heat exchange elements (often identical to the housing) are required. But it can also be a convection flow should be sufficient. Since the state in which the steam column emerges vertically upwards or downwards is the most stable, a vertical arrangement of the heat exchange elements is preferred. In the case of very long heat exchange elements, support against one another may be necessary in order to prevent the individual elements from hitting or sagging. A screen mesh can also perform this task.

In order to achieve a low-eddy flow at the ends of the heat exchange elements, it is advisable to chamfer the ends. An inner chamfer or outer chamfer is particularly useful for thick-walled pipes.

The largest control range and the greatest steam output can be achieved with vertical installation and steam guidance from top to bottom.

The device can be produced inexpensively from standard pipeline parts; they are also available in stainless steel quality. The tube sheets can be made from standard flanges on NC machines. If necessary, the apparatus can also be inserted into a corresponding piping system without its own housing.

• Fig. einseitig offener Rohrbündelkondensator;
• Fig. 2 einseitig offener Flachkammerkondensator;
• Fig. 3 Dampfanwärmer im Gegenstrombetrieb;
• Fig. 4 Dampfanwärmer im Gleichstrombetrieb;
• Fig. 5 eckiger Flachkammerkondensator;
• Fig. 6 Schnitt durch den oberen Teil des Einsatzes eines Kondensators nach Fig. 5;
• Fig. 7 offener Rohrbündelkondensator in einem Behälter.

The invention is illustrated in the drawing and further described below. Show it:

• Fig. One-sided open tube condenser;
• 2 flat chamber capacitor open on one side;
• Fig. 3 steam heater in counterflow operation;
• Fig. 4 steam heater in DC operation;
• Fig. 5 angular flat chamber capacitor;
• 6 shows a section through the upper part of the use of a capacitor according to FIG. 5;
• Fig. 7 open tube condenser in a container.

The open tube bundle condenser, as is shown schematically in FIG. 1, essentially consists of a plug-in tube bundle 1 which projects into a housing 2. The upper part of the apparatus is very similar to a classic heat exchanger. In the space around the pipes 3, the liquid enters or exits through the connector 4 attached to the side of the housing. The main difference occurs in the lower area of the apparatus. The tubes 3 do not end in a tube sheet 5 as above, but open out freely. Steam is fed through the nozzle 7. If the liquid enters at 4 and exits the nozzle 6, there is direct current operation, it enters at 6 and exits at 4, counter-current operation. Regardless of whether the operation is carried out in cocurrent or countercurrent operation, very stable steam columns 8 can protrude from the tubes 3 into the liquid at low temperature differences between liquid and steam.

Vertical tube bundles 1 are preferred. A particularly compact steam column is obtained when steam is introduced from top to bottom; in the opposite case, the steam column is drawn out longer.

The pipes 3 can run out bluntly; in order to generate as little eddy as possible, it can be advantageous to chamfer the pipes inside or outside.

FIG. 2 shows a tube bundle 1 with a different design. Instead of straight cylindrical tubes as in FIG. 1, flat chambers are present here. In the case of a longer inner tube bundle, it may make sense to use support fabrics to improve the mechanical stability or baffles to divert the flow around the tubes; they are not drawn here. At the end of the tube bundle, however, the flow around the tubes should run largely parallel and with little swirl to the tubes. Since the pressure differences inside and outside the flat chamber are very small, the wall thickness can be very low.

Typical applications are shown in FIGS. 3 and 4. The same features have the same reference numerals in both figures. 3, the steam heater 20 is operated in countercurrent, in FIG. 4 in cocurrent for heating an agitator tank 21. The water 22 in the heating jacket 23 of the agitator tank 21 is circulated through pipes 24 through the centrifugal pump 25 and conveyed through the heater 20. To increase the temperature, the cascade temperature control 26 opens the valve 27 and steam 28 flows into the heater 20. A pressure control 29 keeps the pressure in the system constant by discharging excess condensate (possibly also cooling water) via valve 30. If the product temperature in the agitator tank 21 is to be lowered, the temperature control 26 closes the steam valve 27 and opens the cooling water valve 31.

With the heating described, noise generation when introducing steam into liquid is practically avoided, since it is possible with these apparatuses to suppress the otherwise usual bubble formation with inevitable cavitation. By cooling the steam in the heat exchange elements, the steam speed is considerably reduced, or at the beginning of a heating process only condensate emerges from the pipe ends anyway. But even if the steam has not yet condensed inside the tube and steam columns 8 extend into the liquid, a stable, stationary state is formed without cavitation impacts. For these reasons, the tubes 3 of the tube bundle 2 should have high heat conduction; Plastic pipes, which have occasionally been proposed for noise reduction, would be less suitable. Straight, equally long pipes have proven their worth best. A heater, as shown in Fig. 1, was equipped with, for example, 132 stainless steel tubes; the wall thickness of a tube was 1 mm, the diameter 6 mm and the length 800 mm. The housing, also made of stainless steel, had a nominal width of 100. With such a heater, a 10 m3 agitator tank was heated by means of pressurized water heating circuits by introducing 400 kg of water vapor / h. The water circulation was around 25 m ³ / h, the water temperature before steam introduction 25 ° C, the maxi times allowed water circulation temperature was 130 ° C, the water pressure at the entrance to the heater 4.2 bar, the steam pressure 5 bar. The noise level during operation was 70 dBA. It was not measurably increased by the introduction of steam. On the other hand, with a steam jet of a conventional design and roughly comparable output, a noise level of 98 dBA is measured at the beginning of the heating process and a noise level of 80 dBA is still measured at the end of the heating process. Another advantage of the heater according to the invention is the relatively low pressure drop on the liquid side and the very large steam control ratio. In the heater described above, the pressure loss without steam input was less than 0.1 bar; with conventional warmers it is 0.6 bar. According to the manufacturer, the permissible steam control ratio is 1: 7, in special versions up to 1:60. In the case described above, the steam input varied between 0 and 400 kg / h; the steam control ratio is practically infinite. Via an enlarged valve, steam input of 1200 kg / h was achieved without the noise increasing. The upper limit of performance has not yet been reached.

Another form of the device according to the invention is shown in FIGS. 5 and 6. This is a flat chamber bundle 40, similar to that in Fig. 2, in a rectangular housing 41. The steam enters laterally through the flange 42 and the liquid flows through the housing 41 in cocurrent from top 43 to bottom 44 or in countercurrent from 44 after 43.

Details of the heat exchange elements are shown in section in Fig. 6. The steam enters the cage 45 at the flange 42; this has the function of carrying the flat chamber heat exchanger elements 46 and of ensuring the steam distribution. Rings 44 are installed within the flat chambers 46, which are intended to prevent the flat chambers from being pressed together, but to allow steam to pass through. Rings 48 are in turn to ensure a minimum distance between the flat chambers 46 between the flat chambers 46. Knobs 49 on the outside of the flat chambers also have the same function. In addition, these knobs 49 still serve to improve the heat transfer. The flat chambers and the rings are pressed together with the yoke 50.

According to FIG. 7, a tube condenser can also be operated for heating without forced circulation. Cooler liquid is drawn in through the openings 61 at the bottom of the housing 62, into which the heat exchange elements 63 open at the top extend, by steam injection via the flange 60. There is a convection flow. Here, too, stable steam columns can be formed, which extend upwards into the liquid from the heat exchange elements 63. In order to avoid the formation of eddies, which could tear bubbles out of the steam columns, steam and liquid flows should always be routed in parallel near the ends of the heat exchange elements. The steam should flow into the liquid as vertically as possible. In the case of a horizontal steam column, the end of the column is bent upward due to the lower vapor density, steam bubbles being torn out of the columns and being able to cavitate, at least in the case of large steam outputs and thus long steam columns.

Claims (3)

1. Method for the low-noise introduction of large quantities of steam into a flowing liquid in order to heat the latter, wherein the steam is conducted through heat exchange elements of a heat exchanger wherein the liquid at least at the outlet end of the heat exchange element or elements is conducted substantially axially parallel to said element or elements, characterised in that the steam and the liquid are subjected to such temperature and flow conditions that the issuing steam extends into the liquid parallel to the flow and in the form of coherent stable columns of steam extending downstream from the heat exchange elements.

2. Apparatus for carrying out the method according to Claim 1, with a heat exchanger which has heat exchange elements and in which the liquid at least at the outlet end of the heat exchange element or elements is conducted substantially axially parallel to the said element or elements, characterised in that the heat exchange surface and the openings of the heat exchange element or elements (3, 46, 63) are so constructed that the issuing steam extends into the liquid parallel to the flow and in the form of coherent stable columns of steam (8) extending downstream from the heat exchange elements (3, 46, 63).

3. Apparatus according to Claim 2, characterised in that the steam columns (8) extend vertically into the liquid.

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