EP1144934B1 - Using a rigid, helical element in connection with a heat exchanger tube - Google Patents

Abstract

The invention concerns a tube (2) wherein the rigid helical element (5) projects outside the tube (2), at the intake thereof, to keep away from said intake materials (4) likely to clog the tube (2) intake, carried by the fluid designed to circulate in said tube (2).

Description

The present invention relates to improvements made to heat exchanger tubes to liquids, to prevent clogging inputs of these tubes by suspended materials in the liquid to circulate in the tubes.

Deposits are known to occur in the exchanger tubes from the liquids circulating there and that it is necessary to clean them periodically, to remedy the decline in performance that results from this fouling, after periods of use of several months.

Another type of problem frequently encountered with tubes of heat exchangers comes from the clogging of the entrance of the tubes by materials suspended in the coolant, such as coke particles and various aggregates, from or resulting from their passage through the various pipes of the associated devices. There are also pieces of wood, soft or rigid plastics, and even shells molluscs, when the water used for refrigeration comes from a tank in the open, or a natural source of cooling water, such as than a river.

These materials are driven by liquids and come to press against the inlet of the exchanger tubes, sealing them and seriously affecting heat exchange operations. These disadvantages are particularly common in water coolers and in water condensers, whose performance can be considerably reduced because of the clogging of the tubes, lead to the shutdown of the installation for cleaning.

To overcome these drawbacks, it has already been proposed to at the entrance of the tubes, projecting to scrape the inner surface of the tube during its rotation, in order to to clean this tube continuously.

Finally, WO 81/01839 A discloses an evaporator comprising tubes heated from the outside, for the production of fresh water from salt water. During the use of the evaporator, in order to clean the inside of the tubes, we move inside them helical springs protruding outside these tubes.

This is the problem of clogging the inlet of the exchanger tubes thermals that the present invention is interested in and aims to equip this entry of a simple and inexpensive way, fit not only to retain the detritus driven by the liquid penetrating into these tubes and to avoid that they come to apply against the entrance of these tubes in the closing, but also to provoke upstream of this entry a sufficient turbulence to prevent clogging thereof, while ensuring a homogenization of the temperature of the liquid.

For this purpose, the subject of the invention is the use, in association with a circular heat exchanger tube in which is called to circulate a liquid, a helical rigid element protruding to the outside of this tube at the entrance to it, with a view to maintaining away from this input the materials carried by the liquid and likely to block this entry, the element rigid helical being integral with the end of the associated tube without use of an auxiliary fastener, characterized in that the rigid helical element is supported by its turns deformed elastically against the face internal or the outer face of the tube. We also know from the document US 4,424,065 consistent use in the preamble of claim 1.

This rigid helical element has the effect not only of oppose the entry into the tube of various suspended materials driven by the liquid, but also to cause turbulence of this fluid at the entrance of the tube, thus avoiding that the materials carried can completely block the entrance of the tube. the outside of these, various systems of flanges forming cages intended to retain the materials conveyed by the fluid (see, in particular, US-A-5,509,467, EP-A-132 766, US-A-5,102,537, US-A-2,774,569, US-A-4,590,994, and US-A-1,172,938). The implementation of these devices is however complicated and expensive, as requiring, for example, complex realizations, using complicated and delicate preliminary assemblies. In addition, they cause only insufficient turbulence of the liquid upstream of the inlet of the tubes, so that the materials driven by this liquid can come apply firmly against these devices and cause them clogging.

EP-A-0 219 882 discloses a heat exchanger in vertical channels which flows a gas fluid. In these channels are housed elastic elements such as helical springs or supporting metal wires blades extending radially. These elastic elements protrude at both ends of the tubes and are intended to be vibrated, in order to periodically clean inside the channels, by means of an injection intermittent additional compressed gas. It is not not indicated, in this earlier document, whether the fluid gas flowing normally in the holds may contain materials likely to block the entrance of these. On the other hand, it is specified that under normal use, the elastic elements are not set in motion by the gaseous fluid.

It is also known from EP-A-0 369 851 a method of continuous cleaning of a tube, in particular of a heat exchanger heat, in which a fluid circulates, according to which a helical movable element housed in this tube and hooked to one end of it by a mechanical connection the leaving free to turn on itself along the axis of the tube, is driven in continuous rotation by the fluid. The movable element comprises at least one sharp edge intended

Advantageously, the helical rigid element protrudes upstream from the entrance of the tube at a distance of between about 1 and 10 the outer diameter of the associated tube and, preferably, between 2 and 8 times this diameter.

The rigid helical element could be held in position at the entrance of the tube by hooking means known in the technical, able to keep it inside or outside the tube following the technology of the exchanger but this use of an organ auxiliary fixation is not within the scope of the invention.

In the case where the rigid helical element comprises a part engaged inside the tube, such a fastening means can be constituted, for example, in a manner known per se, by a rigid member of U-shaped fastener, known as a "pin" in the art, which is disposed to the outside of the tube, with the ends of the branches of the U close together elastically from each other and engaged in the entrance of the tube, while that the wire wound helically is hooked to the base of the U.

According to the invention, however, the rigid helical element is made integral with the end of the tube at the entrance of which it protrudes to the outside without the aid of any auxiliary fastening device, in taking firm support, by its elastically deformed turns, against the inner face of the tube, as described in FR-A-2 611 879 in another application, or against the outer face of this tube.

FR-A-2 611 879 relates, in fact, tubes heat exchanger, in which are arranged in fixed position of obstacles intended to provoke turbulence of the circulating fluid, with a view to improving the thermal exchanges between this fluid and the wall of the tube and to reduce the risk of solid waste deposits on the inner surface of this wall.

A simple way to achieve such obstacles, said "turbulence promoters" or "disruptive flux ", described in FR-A-2 611 879, consists in arranging the inside of circular section tubes, in a fixed position in contact with their inner wall, a wire, for example metallic, helically wound. To maintain position in the tube the wire wound in a helix, a means particularly simple is to use a wire elastically deformable helical profile, the diameter of the turns is normally greater than the diameter inside the tube, to longitudinally stretch this wire for decrease the diameter of its turns, in order to introduce it into the tube, and after having it introduced, to release it so that its turns tend to resume their initial diameter inside the tube, in coming firmly against the inner wall of the latter, without the wire being displaced by the fluid circulated in the tube.

In an advantageous embodiment, the invention therefore proposes to adapt this known technique with a view to obtaining a different result, by having the same way a wire wound helically inside the heat exchanger tube, in the vicinity of the entrance of this tube but with a protruding part outside the tube, in order to oppose the passage of materials carried by the liquid.

The introduction of a piece of wire wound helically inside the end of the tube may however be performed in the manner described in the cited document.

In another embodiment of the invention, derived from the previous one, the rigid helical element can, when the shape of the tubular plate of the heat exchanger, or any other device analogue, makes it possible to have tubes including an outer part of their upstream end is usable, elastically grip this end of the tube along part of its length and protrude into upstream of the tube inlet.

In this embodiment, the rigid helical element has advantageously turns of diameter normally less than outer diameter of the tube and is deformed elastically so as to increase the diameter of certain turns, in order to be able to engage the end of the tube along part of its length, before releasing these turns so that they enclose the tube.

The rigid helical element can, in all these embodiments, be consisting of a simple rigid wire wound helically.

Advantageously, the ratio of the pitch of the helix to the diameter of the turns is between 0.1 and 5.0 and preferably between 0.5 and 3.0.

The rigid helical element can possibly extend according to the entire length of the tube.

Preferably, the diameter of the last turn of the element Rigid helical, located outside the tube, is smaller than the diameter other turns of this element.

The addition to heat exchanger tubes of an organ Helical retaining suspended materials of the type mentioned above represents a derisory cost compared to that of the exchanger and the dismantling of these organs, with a view to their cleaning, is an extremely simple operation.

In all its forms of implementation, the invention makes it possible to very effectively prevent clogging of tube inlets of exchangers by suspended materials likely to become against these entries.

La figure 1 est une coupe schématique d'une boíte d'alimentation en eau, chargée de matériaux en suspension, de tubes constituant un échangeur thermique, équipés d'un fil enroulé en hélice, qui est engagé dans le tube et fait saillie vers l'extérieur à l'entrée de celui-ci ;

La figure 2 est une vue n'entrant pas dans le cadre de l'invention d'un fil enroulé en hélice et accroché à une épingle constituée d'un fil métallique recourbé en U et engagée dans un tube d'échangeur, à l'extérieur duquel le fil fait saillie ;

La figure 3 est une vue schématique illustrant une forme de mise en oeuvre de l'invention, dans laquelle un fil enroulé en hélice, qui enserre la partie externe d'extrémité amont d'un tube, fait saillie à l'extérieur de celui-ci.

The attached schematic drawings (FIG. 1 and FIG. 3) illustrate the two embodiments of the invention which have just been mentioned. On these drawings:

Figure 1 is a schematic section of a water supply box, loaded with suspended materials, tubes constituting a heat exchanger, equipped with a helically wound wire, which is engaged in the tube and protrudes to the outside at the entrance of it;

FIG. 2 is a view not falling within the scope of the invention of a wire wound in a helix and attached to a pin made of a metal wire bent in a U-shape and engaged in a heat exchanger tube; outside of which the thread protrudes;

FIG. 3 is a diagrammatic view illustrating an embodiment of the invention, in which a wire wound in a helix, which encloses the outer end portion of an upstream end of a tube, protrudes outside the tube; this.

We will refer first to Figure 1, which represents a box 1 water supply tube 2 circular section of a heat exchanger thermal, this box being itself supplied with water by a conduit 3.

According to the invention, when the water is loaded with materials in suspension various 4, who may come to press against the entrance tubes 2 by compromising the water supply of these tubes, overcomes this disadvantage by engaging in the tubes 2, at the entrance to less of these, a wire 5, for example metallic, wound helically, which protrudes outside the tube in box 1 and keeps the suspended solids 4 away from the tube inlet.

As indicated above, the helical turn formed by the wire 5a preferably a diameter at rest higher to the inner diameter of the associated tube and is elastically deformable.

It is thus possible, in a manner known per se, to stretch longitudinally the wire wound helically, to reduce the diameter of the turns and thus be able to introduce it partially into the tube corresponding, then releasing it so that the turns tend to return to their original form, coming to apply firmly against the inner wall of the tube and thereby become integral.

The helically wound wire 5, which protrudes outside the tube 2, can occupy only a short length of it, in the vicinity of its entrance, or extend inside this tube following a major part of its length, if at the same time it serves as a promoter of turbulence.

In the realization of Figure 2, which does not fall within the scope of the invention, there is a wire 6 wound helically, which is housed at the entrance of a heat exchanger tube 7 and protrudes outside thereof. This thread is not necessarily pressed against the inner wall of the tube, but is held in position in this one by a pin formed by a U-shaped curved wire, both of which branches can be brought closer elastically to one another for be engaged in the tube 7, while the base of the U, to which is simply hanging one end of the wire 6 helically wound, done protruding outside the tube.

Figure 3 shows another form of implementation of the invention wherein the yarn 10 wound helically encircles the upstream end of tube 11 and heat exchanger 10 protrudes to beyond the inlet of this tube.

The helical coils normally have a diameter less than the outer diameter of the tube, as shown by the portion 10 has projecting, and some of them have been elastically deformed to increase its diameter so as to engage the end y of the tube, to be then released, in order to grip the tube.

In all these embodiments, the parts of the helically wrapped wire 5 which protrude the outside of the tubes 2, at the entrance of these, maintain a very effective way away from these inputs the various materials in suspension that can to convey the liquid needed to feed these tubes, while causing a strong turbulence of this liquid.

This is illustrated by the Comparative Example which will now be described in detail.

EXAMPLE

In this example, we propose to compare the circulation, under specified pressures, of pure water and of water laden with suspended material, feeding heat exchanger tubes, of a conventional type or conforming to the invention.

These tubes have a length of 6 m and a diameter internal 15 mm.

(1) Un fil métallique enroulé en hélice de manière à former un élément rigide hélicoïdal du type spire hélicoïdale, présentant au repos les caractéristiques suivantes :

• diamètre du fil : 1,5 mm,
• pas des spires : 12 mm,
• diamètre extérieur de l'hélice : 16 mm,
• longueur de l'élément rigide hélicoïdal : 100 mm, dont 50 mm engagés dans les tubes à l'entrée de ceux-ci et 50 mm faisant saillie à l'extérieur des tubes.

(2) Un fil métallique enroulé en hélice de manière à former un élément rigide hélicoïdal de type spire hélicoïdale, dont une extrémité est accrochée à la base d'une épingle en forme de U dont les branches sont engagées à force, en les déformant élastiquement, dans le tube à l'entrée de celui-ci.

Two variants of tubes were made by engaging in the tubes above:

(1) A helically wound wire so as to form a helicoidal spiral rigid element having at rest the following characteristics:

• wire diameter: 1.5 mm,
• not turns: 12 mm,
• outside diameter of the propeller: 16 mm,
• length of the helical rigid element: 100 mm, of which 50 mm engaged in the tubes at the inlet thereof and 50 mm protruding outside the tubes.

(2) A helically wound wire so as to form a helical spiral-type helical rigid element, one end of which is attached to the base of a U-shaped pin whose limbs are forcibly engaged, deforming them elastically , in the tube at the entrance of it.

• diamètre du fil : 1,5 mm,
• pas des spires : 12 mm,
• diamètre extérieur de l'hélice : 14 mm,
• longueur de l'élément rigide hélicoïdal : 100 mm, dont 50 mm engagé à l'intérieur des tubes et 50 mm en saillie à l'extérieur de ceux-ci.

The helically wound wire has at rest the following characteristics:

• wire diameter: 1.5 mm,
• not turns: 12 mm,
• outside diameter of the helix: 14 mm,
• length of the rigid helical element: 100 mm, of which 50 mm engaged inside the tubes and 50 mm protruding outside thereof.

• diamètre du fil métallique dont elle est constituée : 2 mm,
• longueur des branches du U a partir de la base : 40 mm,
• écartement des branches du U : 20 mm,
• longueur des branches engagée dans les tubes à partir de l'entrée de ceux-ci : 10 mm.

The characteristics of the U-shaped pin are at rest as follows:

• diameter of the wire of which it is made: 2 mm,
• length of U branches from the base: 40 mm,
• distance of the branches of the U: 20 mm,
• length of the branches engaged in the tubes from the entrance of these: 10 mm.

• 10 fragments de films de matière plastique sensiblement rectangulaires, dont les dimensions, en centimètres, sont comprises entre 4 à 5 x 10 à 15
• 13 morceaux de bois provenant d'un cageot à fruits, de dimensions (en centimètres) : 4 à 5 x 2 x 0,15
• 10 moitiés de coquilles de moules.

In these tubes are circulated under a relative pressure of 400.10 ² Pa (400 millibars) and 550.10 ² Pa (550 millibars) pure water and water containing various suspended materials, which are the following (for a volume of a total of water of 2 m ³ ):

• 10 fragments of substantially rectangular plastic films, whose dimensions, in centimeters, are between 4 to 5 x 10 to 15
• 13 pieces of wood from a fruit crate, dimensions (in centimeters): 4 to 5 x 2 x 0.15
• 10 halves of mussel shells.

The flow rates obtained at the various pressures are recorded with the usual tubes and with the tubes according to the invention.

The results obtained are collated in the following Table. Pressure Flow (m ³ / h) Usual tubes Usual tubes Tubes equipped with a spiral coil according to the invention Tubes equipped with a helical turn and a U-shaped pin Clean water Water + suspended matter Water + suspended matter Water + suspended matter 400.10 ² Pa 13.0 10.2 12.1 12.1 550: 10 Pa ² 15.1 11.3 13.9 14.2

These results show that equipped tubes a wire wound helically and protruding outside the tube, either alone or combination with a pin, hold in a very effective the various materials transported by the water that them feeds. Indeed, the flow of this water, under two different pressures, remains relatively close to the flow of pure water feeding clean tubes under the same pressure, while the flow of the tubes fed with water loaded with various materials, in the absence of the means according to the invention, falls considerably.

Claims (9)

1. Use, in association with a heat exchanger tube (2, 11) of circular cross-section in which a liquid is intended to circulate, of a rigid helicoidal member (5, 10) projecting outwards from said tube at the inlet thereof, with the aim of keeping the materials carried by the liquid and capable of blocking said inlet away from said inlet, the rigid helicoidal member (5, 10) being integral with the end of the associated tube (2, 11) without using auxiliary fixing means, characterised in that the rigid helicoidal member (5, 10) gains purchase against the internal or external face of the tube (2, 11) via its resiliently deformed turns.
2. Use according to claim 1, characterised in that the rigid helicoidal member (5, 6, 10) projects upstream from the inlet of the tube by a distance of between approx. 1 and 10 times the external diameter of the associated tube and, preferably, between 2 and 8 times said diameter.
3. Use according to either of claims 1 and 2, characterised in that the rigid helicoidal member (5) is composed of turns of a diameter which is normally greater than the internal diameter of the associated tube (2), gaining firm purchase by resilience against the internal wall thereof.
4. Use according to either of claims 1 and 2, characterised in that the rigid helicoidal member (10) resiliently grips the outer part of the end of the associated tube (11) for part of the length thereof.
5. Use according to claim 4, characterised in that the turns of the rigid helicoidal member (10) have a diameter which is normally less than the external diameter of the associated tube (11), those turns which grip the tube having been deformed resiliently to allow the tube to be inserted therein.
6. Use according to any one of the preceding claims, characterised in that the helicoidal member (5, 10) is made from a rigid wire wound so as to form a helix.
7. Use according to any one of the preceding claims, characterised in that the ratio of the helix pitch of the rigid helicoidal member (5, 10) to the diameter of the turns is between 0.1 and 5 and, preferably, between 0.5 and 3.0.
8. Use according to any one of the preceding claims, characterised in that the diameter of the final turn of the rigid helicoidal member, located outside the tube, is less than the helix diameter of said member.
9. Use according to any one of the preceding claims, characterised in that the rigid helicoidal member (5, 10) extends over the entire length of the associated tube (2, 11).

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