EP0012782A1 - Cooling tower - Google Patents

Abstract

1. An atmospheric cooler comprising at least a heat exchanger exchanging heat between at least a fluid, for example water, and a gas, for example the air of the atmosphere, comprising a battery of flexible exchanger tubes substantially parallel to one another and each fixed at each end in a tube plate of a device for distributing and/or collecting said fluid, the latter circulating in the exchanger tubes while the gas passes through the battery transversely relative to said tubes, characterised in that said exchanger tubes (10; 210) are supported only at their two ends and have a length exceeding the distance between said tube plates (11, 15; 115) and said tube plates (11, 15; 115) are so oriented that said exchanger tubes (10; 210) freely hang between said ends, under the effect of their own weight, and have, in a vertical plane, a contour substantially in the shape of a part of a catenary curve.

Description

The invention relates to a heat exchanger between at least one fluid, for example water, and a gas, for example atmospheric air, of the type comprising a battery of flexible exchanger tubes substantially parallel to one another fixed to each of their ends in a tubular plate of a device for distributing and / or collecting said fluid, the latter circulating in the exchanger tubes while the gas crosses the battery transversely with respect to said tubes.

The invention also relates to the application of this heat exchanger to atmospheric refrigerants of the dry type "in which the fluid to be cooled is brought into contact indirectly with atmospheric air via the wall of the tubes of the exchanger , to atmospheric refrigerants of the "mixed" type which comprise both at least one exchanger of the aforementioned type and at least one wet exchange body in which a liquid, which may or may not be the fluid circulating in the tubes of the heat exchanger, is brought into direct contact with atmospheric air, and with atmospheric refrigerants of the "hybrid" type in which the tubes of the exchanger of the aforementioned type are externally wetted by a liquid, which may or may not be the fluid circulating in the exchanger tubes.

The setting in motion of the air in these refrigerants is assumed either by natural draft, assisted or not by fans, or only by blown or suction fans.

There are a number of documents which describe the use of flexible tubes, for example plastic, for the production of heat exchangers.

French Patent No. 73 10 009 describes a heat exchanger made of flexible plastic tubes taking advantage of the possibility of using very large tubes, but which is still designed as a conventional coil of finned metal tubes, c that is to say as a rigid parallelepipedic assembly.

French Patent No. 1,455,991 also describes an exchanger made of plastic tubes. However, the exchanger is rectilinear and of circular section of the type of water-water exchanger and not of fluid-gas exchangers such as those used in atmospheric refrigerants. The flexibility of the tubes is only exploited at the ends of the exchanger to group them compactly for the hydraulic connection. The exchanger is straight and even rigidly contained in a metal sheath.

French patent application No. 76 25 059 describes exchangers with flexible plastic tubes of great lengths arranged horizontally and capable of marrying various contours of refrigerants, or even their periphery. In these exchangers, the tubes are stretched at the level of their spacers where they are eventually forced to bend and form an angle. Thus, the curvilinear contours of refrigerants can be approved by polygonal contours of the exchangers. The flexibility of the tubes is used here to conform the shape of the exchanger to that of the refrigerant, contrary to what is provided in the first two patents mentioned above. However, the very large length of the tubes and the high coefficient of expansion of the plastic of which they are made cause these tubes to undergo significant variations in length which it is necessary to absorb. This therefore results in a complication in the production of the exchangers.

This problem of the expansion of long plastic tubes has been resolved in French patent application No. 77 30 221 by an arrangement in which the battery of tubes is suspended over at least part of its length from a structure. of support by hangers to which are hung bracing devices which, along the battery, join the tubes from distance to distance, the lines being inclined so as to put the tubes under tension. Although very effective, this arrangement is especially intended for exchangers whose tubes are horizontal and also requires the presence of support and suspension equipment.

The object of the invention is to provide a heat exchanger which is of a simpler construction than the known flexible tube exchangers while allowing the flexibility property of the tubes to be used to produce exchangers of very varied configuration.

The invention as characterized in the claims, achieves these goals thanks to the fact that the exchanger tubes are only fixed at their two ends and therefore hang freely between these two points by taking their own position under the effect of their own weight and thanks to their flexibility.

This arrangement has the advantages of being very simple in construction compared to those of known exchangers, of making it possible to realize very varied configurations of exchangers and, moreover, of solving by its design, without recourse to external means, the problem of thermal expansion of the tubes which, as indicated above, is particularly crucial when using, as is preferably the case in the present invention, tubes made of synthetic material,

• - la Fig. 1 est une vue en élévation latérale et en coupe d'un réfrigérant atmosphérique " sec " à tirage mécanique équipé d'échangeurs de chaleur suivant l'invention ;
• - la Fig. 2 est une vue de dessus, avec arrachement partiel, du réfrigérant de la Fig. 1 ;
• - la Fig. 3 est une vue en élévation avant du réfrigérant de la Fig. 1 ;
• - la Fig. 4 est une vue de détail en perspective d'un dispositif d'entretoisement des tubes des échangeurs du réfrigérant des Fig. 1 à 3 ;
• - la Fig. 5 est une vue analogue à la Fig. 1 d'un réfrigérant atmosphérique "sec " équipé d'un échangeur suivant une variante de réalisation ;
• - la Fig. 6 est une vue analogue à la Fig. 1 d'un réfrigérant atmosphérique "mixte " équipe d'échangeurs semblables à ceux de la Fig. 1 ;
• - la Fig. 7 est une vue de dessus avec arrachement partrel, du réfrigérant de la Fig. 6 ;
• - la Fig. 8 est une vue en coupe de quelques tubes de l'échangeur des Fig. 6 et 7 montrant une variante de dispositif d'entretoisement;
• - la Fig. 9 est une vue analogue à la Fig. 6 montrant un autre type de réfrigérant atmosphérique mixte équipé d'échan- geui s suivant l'invention;
• - la Fig. 10 est une vue de dessus de l'échangeur de la Fig. 9 ;
• - la Fig. 11 est une vue en élévation d'un réfrigérant atmosphérique " sec " à tirage naturel équipé d'un échangeur suivant l'invention ;
• - la Fig. 12 est une vue en coupe suivant la ligne 12-12 de la Fig. 11 ; et
• - la Fig. 13 est une vue analogue à la Fig. 11 montrant une variante de réalisation.

Other characteristics and advantages of the invention will emerge from the description which follows of different embodiments given only by way of examples and illustrated by the appended drawings in which:

• - Fig. 1 is a side elevation view in section of a "dry" atmospheric refrigerant with mechanical draft equipped with heat exchangers according to the invention;
• - Fig. 2 is a top view, partially broken away, of the refrigerant of FIG. 1;
• - Fig. 3 is a front elevational view of the refrigerant of FIG. 1;
• - Fig. 4 is a detailed perspective view of a device for bracing the tubes of the coolant exchangers of FIGS. 1 to 3;
• - Fig. 5 is a view similar to FIG. 1 of a "dry" atmospheric refrigerant equipped with an exchanger according to an alternative embodiment;
• - Fig. 6 is a view similar to FIG. 1 of a "mixed" atmospheric refrigerant fitted with exchangers similar to those of FIG. 1;
• - Fig. 7 is a top view with partial cutaway, of the refrigerant of FIG. 6;
• - Fig. 8 is a sectional view of a few tubes of the exchanger of FIGS. 6 and 7 showing a variant of the bracing device;
• - Fig. 9 is a view similar to FIG. 6 showing another type of mixed atmospheric refrigerant equipped with exchangers according to the invention;
• - Fig. 10 is a top view of the exchanger of FIG. 9;
• - Fig. 11 is an elevational view of a "dry" atmospheric refrigerant with natural draft equipped with an exchanger according to the invention;
• - Fig. 12 is a sectional view along line 12-12 of FIG. 11; and
• - Fig. 13 is a view similar to FIG. 11 showing an alternative embodiment.

Referring to Figs. 1 to 4, we see a "dry" atmospheric refrigerant with mechanical draw of rectangular shape comprising a chamber 1 delimited by two side walls 2 supported by a metal frame 3 on two of the sides of the refrigerant, and by two open faces 4 constituting inlets air on the other two sides of the refrigerant. Chamber 1 is surmounted by a roof 5 in the form of a pyramid trunk which ends in a circular ferrule 6 in which is mounted a fan 7 driven by a motor which has not been shown for the clarity of the drawing.

Inside the chamber 1 are arranged two heat exchangers 8 according to the invention, Each exchanger 8 comprises a battery 9 of flexible tubes 10 made of a synthetic material parallel to each other which are so connected. sealed at their lower part in the opposite tubular plates 11 of a distributing water box 12 for supplying water or other liquid to be cooled which has the shape of a rectangular parallelep and extends over the entire length of the refrigerant equidistant from the two open faces 4 of air inlet and at a certain distance above the ground 14, a pipe 13 for distributing liquid ending in the water box 12. The tubes 10 of each building 9 extend upwards from the water box 12 and are sealed in a watertight manner their upper part in a tubular plate 15 of a respective water box 16 collecting the cooled liquid which is discharged from the boxes- 16 through drainage pipes 17. The collecting water boxes 16 extend parallel to the dispensing water box 12 at the upper part of the chamber 1 where they delimit the upper edge of the inlets d 'air 4, and they are supported like the water-dispenser 12 by the metal frame 3 which has been shown only schematically for clarity of the drawing.

The tubes 10 (Fig. 4) of the exchangers 8 are made of a synthetic material which is both flexible or flexible, resistant to relatively high operating temperatures, in particular with regard to creep, and transmitting relatively well the heat, such as certain organic polymers, for example polybutene or crosslinked polyethylene. The diameter of the tubes is preferably relatively small to allow good heat exchange, for example from 5 to 20 mm, and they are arranged, considering the exchangers 8 in a vertical transverse plane as in FIG. 1, in a series of parallel plies, the number of which may be, for example, from 8 to 40.

The tubes 10 are tightly fixed in the tuoular plates 11 and 15 by suitable tight fixing devices, such devices being described in particular in French patent applications n ° 76 03 581 and 77 04 168 and in French patent n ° 1 425 666.

As can be seen in FIG. 1, tubes 10 hang freely between their fixing points in the tubular plates 11 and 15 and, to prevent them from touching, they are grouped in a number of bundles 18, the tubes of which are joined from distance to distance by bracing devices 19 an exemplary embodiment of which is shown in more detail in FIG. 4. This bracing device 19 consists of a number of strips 20 held tight against each other by means of a frame 21 and which are provided with notches delimiting two by two of the passages for the tubes 10. With regard to this type of bracing device, reference may in particular be made to French patent application No. 76 25 059 which gives a detailed description thereof. Other examples of similar bracing devices are also described in French patents no. 73 10 009, 75 39 240, 75 07 727 m in US patents no. 3, 422, 884 and 4, 036, 289. Thanks with these bracing devices, regular air passages are provided between the tubes which, preferably, are staggered by means of a shift of the adjacent plies with respect to each other, so that these passages force the air to follow a winding path between the tubes.

The tubes 10 have a length greater than the distance separating the tubular plates 11 and 15 so as to have a curved profile in a vertical plane as shown in FIG. 1. However, this Figure is schematic and does not pretend to reproduce exactly the actual curvature of the tubes, this mainly depending on their length. It will also be noted that the tubular plates 11 and 15 must be oriented so that, in the normal position of the tubes, the ends of the latter are oriented substantially perpendicular to the tubular plates of the lower and upper water flasks, which are horizontally offset from each other.

The operation of the refrigerant of FIGS. 1 to 4 is entirely conventional and will therefore not be described in detail. We simply pair that the liquid to be reiroidir, for example water, is brought by pumping means (not shown) to the dispensing water box 12 by the supply line 13, In the water box 12, the liquid is distributed in the tubes 10 of the two exchangers 8 and flows towards the collecting water tanks 16. During its passage through the tubes, the liquid is cooled by atmospheric air which enters the refrigerant through the air inlets 4 and passes through the batteries 9 in the directions indicated by the arrows F in FIG. 1. The air heated and sucked in by the fan 7 is then discharged into the atmosphere through the shell 6.

Note that in the example shown the side walls 2 stop at a certain distance above the ground 14, and more precisely at the height of the mud-to-enu distributor 12, which saves two air inlets side to improve the penetration of atmospheric air into the refrigerant. However, alternatively; the side walls 2 can extend to the ground 14.

The embodiment of FIG. 5, on which the same reference numbers as in FIGS. 1 to 3 but increased by the number 100 have been used to designate the similar parts, differs from that of FIGS. 1 to 3 by the fact that it includes a soul exchanger 108, the lower water box being eliminated and the tubes of the exchanger 108 extending from one of the superure water tanks 11 61, which constitutes a distributor water cup supplied by a supply line 117a, to the other water tank 11 6b, which constitutes a collecting water tank as in the previous example and is placed at the same height than the water box 116a. The tubes of the exchanger 108 have a length substantially double that of the exchangers 8 and hang freely between the water boxes 116a and 110b with a profile in the shape of a chafnctte. Compared to the example of Figs. 1 to 3, that of FIG. 5 has the advantage of allowing a significant saving of a water box. but it increases the risk of blockage of the tubes by stagnant deposits at their lower points, risks that good quality of the fluid to be cooled as well as a relatively high circulation speed of this fluid can reduce or even avoid .

Figs. 6 and 7 show a mixed refrigerant which differs essentially from the refrigerant of FIGS. 1 to 3 by the fact that it comprises two “wet” exchange bodies with crossed currents 222 each mounted in front of a respective “dry” exchanger 208 so that each flow of atmospheric air passes in series through the exchange body damp 222 and the exchanger 208. The collecting water tanks 216 comprise several discharge pipes 217a instead of only one in the case of the refrigerant of FIGS. 1 to 3, and these conduits 217a function as overflows which pour the liquid having passed through the exchangers 208 into two tanks 223 respectively adjacent to the two water tanks 216. The tanks 223 are provided with dispersing nozzles at their bottom through which the partially cooled liquid in the exchangers 208 is poured over the associated exchange body 222. The wet exchange bodies can be either of the type in which the liquid flows in the form of thin films as described for example in French patents No. 1,140,551 and 2,183,704, or of the splash type as described in US Patent No. 3,751,017. Under each exchange body 222 is placed a basin 224 intended to collect the cooled liquid which flows from the exchange body and which is then evacuated from each basin by an evacuation pipe 225.

Between each wet exchange body 222 and the associated dry exchanger 208 is arranged a drop separator 226. Such drop separators are perfectly conventional and examples are given in particular in GB patents No. 1,347,648, US 3,925 .523, US n ° 3, 804, 389, US n ° 4, 052, 491 French n ° 2 316 570, French n ° 2 331 762 and in patent application DE-OS 2 602 485. These drop separators are necessary not only to reduce the vesicular entrafnemelts of the refrigerant, but also to ensure good efficiency to the dry exchangers from the first layers of tubes, which can soon. when heating the air to constant absolute humidity, therefore decreasing relative humidity, useful effect sought by the dry exchanger in mixed refrigerants in order to reduce the plume, these first layers should therefore not be used to evaporate the liquid water vesicular drive by allowing only the following layers to lower the vapor pressure of the water. Furthermore, in this refrigerant, the side walls 204 extend to the ground due to the presence of the wet exchange bodies in which atmospheric air must circulate in cross currents relative to the liquid,

As shown in more detail in FIG. 8, the device for bracing the tubes of the heat exchangers 208 is different from that of the exchangers 8. This device consists of split rings or disks 227, for example made of plastic, which are mounted on the tubes 210 and whose radial width determines the spacing between the tubes. In addition, the tubes 210 can be joined together by bundles by means of any suitable links (not shown),

In general, any type of appropriate bracing device other than those shown in Figs. 4 and 8, for example prolubian tubes, can be used to maintain the gap between the tubes of the exchanger according to the invention.

The operation of the refrigerant, Figs. 6 and ₇ is the conventional operation of a mixed refrigerant with serial circulation of the liquid to be cooled and atmospheric air and, as is moreover clearly apparent from the above description, it will not be described in more detail .

Figs. 9 and 10 represent another type of "mixed" refrigerant in which the liquid to be cooled also circulates in series in the "dry" exchanger and in the "wet" meis exchanger where the two exchangers are traversed by air flows parallels which only mix after crossing the two interchanges. geurs. In these figures, the same reference numbers have been used as in the preceding figures to designate the analogous parts but by assigning them the figure of hundreds 3 instead of the figure of hundreds 2 and the figure of hundreds 1 in the examples of FIGS. 6 and 7 on the one hand, and from FIG. 5 on the other hand.

The liquid supply to the exchangers 308 is carried out from above by means of the pipes 317 which are connected to the upper water boxes 316 by a series of parallel elbows 317 ′. The partially cooled liquid in each of the two exchangers 308, which are arranged on each side of the refrigerant above the dry exchanger 322, is collected in the lower water boxes 312 which distribute it to food tanks. respective mentatiou 323 themselves supplying the distribution network 328 of the countercurrent wet exchange body 322.

The operation of the refrigerant of FIGS. 9 and 10 is similar to that of mixed refrigerants with parallel air flows. It will simply be noted that, as a variant, the circulation of the liquid in the dry exchangers 308 and wet 322 could be done in parallel instead of occurring in series and that by garlic their refrigerant, instead of being rectangular in shape, was hard in a circular shape. Fig, 9 remains valid in this case but is affixed to represent a single upper water box 316 of circular shape and a single lower water tank 312 also of circular farm,

Figs. 11 and 12 show the application to a hyperbolic type cooling tower with natural draft of the pendant tube exchanger according to the invention, The tower comprises an eoque 429 in thin beten veil and a network 430 of beams in the form of spider supporting the hull by means of a circular lintel beam 431 to define a peripheral air inlet 404.

At the circular level 431 is located the upper supply water tank 416, which is continuous or consists of a succession of short rectilinear elements aligned circularly, supplying the battery 409 with flexible plastic tubes whose lower ends are connected to the lower circular bofte-à-cau 412, the overall diameter of which is less than that of the water bofte 416.

This difference between these diameters results in a difference between the tube spacings: at the bottom water box, the spacing in the tangential direction is smaller. This can possibly be compensated, having regard to the passage of air, by an increase in the spacing in the radial direction, or even by the splitting of plies, of tubes in a staggered arrangement.

Anyway, the diameters of the current towers at the lintels being very large, of the order of 100 to 200 m, the difference in the overall diameters of the lower and upper water tanks (accentuated in the drawing, for more of clarity) is relatively weak, of the order of modest meters to about twenty meters at most, and does not pose difficult problems relating to the variation of spacing of the tubes.

Finally, FIG. 13 also shows a hyperbolic type cooling tower with natural draft, but where the battery 509 of plastic tubes takes a centrifugal direction from the lintel 531, owing to the fact that the lower water box 512 has a diameter greater than that of the bottom edge of air inlet opening 504.

At the water tank 512, the slightly larger spacing of the tubes compared to that existing at the upper water box 516 can be taken advantage of to compensate for the tendency to decrease air flow. between the lintel and the ground since, in fact, the air pressure losses on passing through the exchanger increase from top to bottom if the radial pitch of the exchanger is constant.

In the example of Figs. 11 and 12 as in that of FIG. 13, the battery 409 or 509 consists of several layers of tubes, each defining a surface of revolution of curvilinear profile.

Of course, many modifications can be made to the embodiments described above without departing from the scope of the invention. Thus, for example, the internal fluid of the dry exchangers of mixed wet-dry refrigerants, such as those shown in FIGS. 6 to 10, could be different from that of wet exchangers. Advantageously for the reduction of the plume of the wet section, it could be a fluid at a substantially higher temperature. The fluid supply circuits (fluid for the dry exchanger; water or aqueous solution for the wet exchanger) would then be entirely separate.

The setting in motion of the air of the refrigerants concerned can take place either by fans, sucking or blowing air through the exchangers, or by a natural draft chimney, assisted or not by fans. The wet exchange bodies can be of all known types, particularly against the current, or with cross currents, of the skin-peeling or splash type, or combined, The wet and dry exchangers can be mounted in parallel or in series in the air flow and, in the latter case, the dry exchanger can be upstream or downstream of the wet exchanger in this air flow.

The exchanger according to the invention could also be designed, no longer only as a dry exchanger, but as a hydribe exchanger as described in the Earopean patent application 11 ° 78 400 144. 8.

Changes could still be made to the water boxes. In fact, the direction of feeding, from bottom to top or from top to bottom as the case may be, could be reversed with respect to what has been described or represented in the various exemplary embodiments. Another modification would consist in making multi-pass batteries by partitioning the water boxes longitudinally or transversely. If the number of passes is even, the same water box can then serve as a dispenser device and a liquid collecting device. Such multiple-pass water boxes are described in particular in US Pat. No. 2,143,157, while the utility model DE 70 08 998 derives from a plastic water box. It should be noted that other materials than plastic can be used for the production of water tanks.

Claims (12)

1 - Heat exchanger between at least one fluid, for example water, and a gas, For example atmospheric air, comprising a battery of substantially parallel flexible exchanger tubes fixed to each of their ends in a tubular plate of a device for distributing and / or collecting said fluid, the latter circulating in the exchanger tubes while the gas crosses the battery transversely with respect to said tubes, characterized in that said exchanger tubes (10; 210) are only supported their two ends and have a length greater than the distance separating said tubular plates (11, 15; 115) so as to hang freely between said ends under the effect of their own weight and present. ter a curved profile in a vertical plane. 2 - Exchanger according to claim 1, characterized in that, as known per se, said distributor and / or collector devices (12,16; 116a, 116b; 212, 216; 312, 316) have a rectilinear shape and in that said battery (8; 108; 208; 308) consists of several parallel plies of tubes. 3 - Exchanger according to claim 2, caraaterial in that the two distributor and / or collector devices (12, 16 212, 216; 312, 316) between which extend the exchanger tubes are arranged at different heights and are offset horizontally relative to each other. 4 - Exchanger according to claim 2, characterized in that the two distributor and / or collector devices (116a 116b) between which the exchanger tubes extend are arranged at the same hzutor and the battery tubes (108) s 'extend following a chain-shaped curve between said devices. ^{5 -} Exchanger snivant the claim 1 1, characterized in that the said devices distributeffr and / or collector (412,416; 512, 516) between which extend the exchanger tubes have a circular shape and have a different diameter. 6 - Exchanger according to bwendication 5, characterized in that the battery (409; ₅₀₉ ) is made up of several layers of tubes each defining a surface of revolution of curvilinear profile, 7 - exchanger suisant any one of claims ¹ to 6, characterized in that lestlites tubular plates are oriented substantially perpendicular to the adjacent ends of the exchanger tubes. 8 - Exchanger according to any one of claims 1 to 7, characterized in that the exchanger tubs are now spaced from each other by bracing devices provided from distance to distance the tang of said tubes. 9 - Atmospheric refrigerant, characterized in that it comprises at least one heat exchanger according to any one of claims 1 to 8. 10 - Refrigerant according to claim 9 when it depends on claim 3, characterized in that it comprises two heat exchangers (8: 208) containing a common lower distributor device (12; 212.) Extending in the middle of the refrigerant and the tubes of which diverge from said common distributor device towards two rusraective upper plector devices (16; 216), 11 - Refrigerant according to reendication 10, charac- ^terized in that, as known per s _o i, it comprises two heat exchange body type "wet" (222) disposed chaeun upstream of a respective heat exchanger fiur relation to meaning of atmospheric air flow in the refrigerant. 12 - Atmospheric refrigerant according to claim 9 when it depends on claim 5, said regenerant being of the type comprising a natural draft tower of circular section provided at its base with a peripheral air inlet, characterized in that one of the distributor and / or collector devices (416; 516) of the heat exchanger extends along the upper edge of the air inlet opening (404; 504) of the refrigerant and. the other distributor and / or collector device (412; 512) is offset radially relative to the lower edge of said air inlet opening.

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