FR2658906A1 - Method for cooling a liquid in an atmospheric cooler (cooling tower) and cooler for implementing this method - Google Patents

Abstract

This cooler comprises a trickle device (2) placed at the base of a shaft (chimney) (1), consisting of an upper tank (4) capable of being fed with hot liquid to be cooled, and a lower tank (7) for collecting the cooled liquid flowing dispersed from a perforated base (5) of the upper tank, branch pipes (8, 8a, ...) for diverting a part of the hot liquid from the perforated base (5) of the upper tank (4) to a level situated in the liquid dispersion volume (10), substantially halfway up, between the two tanks, these pipes (8, 8a, ...) being designed to disperse the hot liquid in droplets from this region. This arrangement avoids any risk of freezing of the water in the dispersion volume before it has arrived at the collection tank (7) in particularly cold weather.

Description

 The object of the present invention is. a process for cooling a liquid in an atmospheric reagent, as well as a refrigerant. suitable for the implementation of this process.

 The refrigerant can be, for example, of the type comprising an upper annular basin which can be supplied with hot liquid to cool a lower annular basin placed below the upper basin to collect the cooled liquid flowing in dispersion or in rain, from '' a perforated mowing of the upper basin, the two basins delimiting between them an annular volume of dispersion and trickling of the liquid, crossed by a radially current of substantially horizontal atmospheric air.The draft of the atmospheric air is ensured, either by a fireplace, either by fans arranged in the upper or lower part.

 In the case where the refrigerant includes an atmospheric air draft chimney, the upper distribution network for hot liquid and the collecting basin can also be located entirely inside the chimney.

 Such atmospheric refrigerants are used in all industries requiring an evacuation of calories, in particular in nuclear power plants.

 The liquid to be cooled is then hot water, coming from a condenser, its temperature being for example at 23 C. The upper basin is arranged at a significant height above the lower collection basin, from which the pipes of recovery of cooled water, for example at 10 C, which is reintroduced into the condenser circuit.

 It is known that an important problem which arises in very cold weather is to prevent the freezing of the water which cools at the flow height, for example 19 or 20 meters. Indeed, when the atmospheric temperature drops below a predetermined value, for example -13 ° C, hot water at 23 ° C which falls from the upper basin can freeze locally at the periphery of the runoff volume. It then forms huge blocks of ice which, when melted, fall. and can cause significant damage.

 To solve this problem, we proposed in particular. to equip the upper basin with an overflow pipe starting from the outer periphery of this basin, and the lower end of which opens into the lower part of the volume of water salt, in which is thus injected with hot water (FR-A 2 593 902).

 However, this solution is not satisfactory, so that in very cold weather, ice may nevertheless form locally in the volume of the stream and in the collecting basin. We have also proposed a so-called workaround solution, according to which the hot water is sent, for example at 23 ° C., directly into the lower basin, from which it only emerges when slightly cooled, for example at 20 ° C. instead of 10-C. The reinjection of insufficiently cooled water into the condenser circuit then lowers the efficiency thereof, and causes an increase in the operating costs of the production unit.

 The object of the invention is therefore to propose a satisfactory solution to the problem set out above.

 In accordance with the process referred to in the invention, hot liquid in dispersion is distributed in an area extending on either side of the mid-height between the upper distribution network and the collecting basin inside the liquid runoff volume between them and in the vicinity of the outer periphery of the <iit volume.

 According to an embodiment of this method, in which the distribution network comprises a basin provided with a perforated bottom from which the hot liquid can flow in dispersion, part of the hot liquid is derived from the bottom in an area extending on either side of the mid-hallteur between the two basins and inside the volume of runoff of the liquid, between the latter and. in the vicinity of the outer periphery of said volume.

 Te atmospheric refrigerant. for the implementation of the above process comprises an upper network for distributing a hot liquid to be cooled and a lower basin placed below to collect the cooled liquid; according to the invention, this refrigerant comprises means for distributing the hot liquid in dispersion in an area extending on either side of the mid-height between the upper distribution network and the collecting basin, inside the volume of liquid runoff between them and in the vicinity of the outer periphery of said volume.

 According to one embodiment of the invention, in which the upper distribution network comprises a basin which can be a] imenté in hot liquid and whose bottom is perforated to allow the flow of hot liquid, by dispersion and runoff in a volume delimited by the two upper and lower basins, this volume being traversed by a radial stream of substantially horizontal atmospheric air, the refrigerant comprises means for diverting a party of the hot liquid from the perforated bottom of the upper basin in an interior zone the volume of runoff of the liquid, close to its outer periphery, and which extends on either side of the mid-height between the two basins, said means being adapted to disperse the hot liquid in rain from this zone .

 Advantageously, p] users bypass lines each provided with water dispersers at their end i nféri etire, are distributed annularly under the upper basin.

 your bottom part of each. pipe can be constituted by one or more circular sectors, each equipped with water dispersers and radially offset in the volume. liquid dispersion.

 If the water dispersers are thus located halfway between the two basins, and the temperature of the hot water supplied to this disperser is 23 C, we see that the water falling in rain from these dispersers can prevent local and global ice formation of water flowing from the upper basin, to an atmospheric air temperature of approximately -1.3 C.

 Alternatively, to prevent any risk of freezing in even colder weather, it is possible to shift in height on either side of the mid-height between the two basins, two end branches of each bypass line, a valve being interposed between the two branches, and being open to supply liquid to the lower branch when the atmospheric temperature drops below a predetermined value, for example -25 C.

 In the various possible embodiments of the invention, the average temperature of the water collected in the collecting basin remains substantially at the desired value.

 The invention will now be described with reference to the accompanying drawings which illustrate several embodiments thereof by way of non-limiting examples.

 Figure 1 is. a dry elevation view of an atmospheric refrigerant equipped with an annular trickling device according to a first embodiment of the invention.

 FIGS. 2A and 2B are simplified partial plan views of two other forms of embodiment of the trickling device according to the invention.

 Figure 3 is an elevational view by simplified rod of a fourth embodiment of the trickling device according to the invention.

 Figure 4 is a schematic view in partial elevation of an alternative embodiment of the embodiment of Fig.l.

 Figure 5 is. a simplified elevation view similar to Fig.l of a refrigerant equipped with a trickling device according to a fifth embodiment of the invention.

 Figure 5A is a detail view of an alternative embodiment of the device of Fig.5.

 Figure 6 is a simplified partial top view of the bypass network of the device of Fig.5.

 We see in Fig.1 an atmospheric refrigerant comprising a chimney 1 of atmospheric air draft of the type used in particular for cooling water in nuclear power plants, surrounded at its base with a sealing ruis device 2.

 The chimney 1 rests in a manner known per se, on a frame 3 of beams, the height of which is substantially equal to that of the annular run-off device 2. In a manner also known per se, the latter comprises an annular upper basin 4 with horizontal bottom perforated 5, supported by a set of gantries 6, and below which is placed on the ground, a lower annular basin 7 for collecting water dispersed in rain from the perforations in the bottom 5.

 The supply of hot liquid to the basin 4 and the evacuation of the cooled liquid collected in the basin 7, are provided in a known manner by a system of pipes not shown.

 In the following due 1. 'exposed we will consider that the liquid to be cooled is water.

 Due to the difference in temperatures between the air outside the chimney 1 and the air inside it, there is a natural draft which draws the atmospheric air outside inside the chimney 1, through of the volume of runoff and dispersion of the water delimited by the two basins 4 and 7. The refrigerant is then said to be of the cross-current type, because the stream of cooling air circulates in a direction substantially perpendicular to that of the stream of water spray to cool.

 The trickling device 2 comprises at least one pipe 8, and preferably several (a second pipe 8.1 diametrically opposite to the pipe 8 being visible in FIG. 1) distributed annularly at regular intervals under the basin 4. These pipes 8, 8.1, ... each open at their upper ends into a perforation in the bottom 5 of the upper pelvis 4, in the vicinity of the inner periphery of said upper pelvis 4. On the other hand, these pipes open at their opposite lower ends, in the vicinity of the outer periphery 9 of the volume 10 of water dispersion, appreciably mid-height between the basins 4 and 7.

 In Fig. 1 the volume of dispersion 10 of the water is. delimited by lines inclined to the vertical, due to the air current F which deport the dispersion of water from the outside to the inside of the base of the chimney 1.

 Each bypass line 8 has a substantially vertical section 8a, which starts from the bottom 5, and a second end section 8b, substantially horizontal, the end of which is practically at the periphery 9 of the runoff volume 10, and which extends radially. The sections 8b are each provided with water dispersers 11, suitably offset radially from the outer periphery 9. In operation, the height of water h in the upper basin 4, located above each pipe 8, is sufficiently important to allow the bypass pipes 8 to provide a sufficiently high flow of hot water to the dispersers 11, this flow being distributed inside the runoff volume 10 by the dispersers 11. Therefore, except at very atmospheric temperature low, the water dispersed in rain from the perforated bottom 5 cannot freeze before arriving at the lower basin 7, thanks to its heating by hot water sprayed from the dispersers 11.

 In the second embodiment shown in FIG. AA, the radial lower branches 8d of the conduits 8 have ends extending over determined circular sectors, provided with dispersers 11 staggered radially. The entire section of the volume 10 can thus be watered by the dispersers 11.

 In the variant of FIG. 2B, the radial branches Sc each carry circular sectors 12, 13 offset radially and provided with water dispersers 11, thus distributed over the entire periphery of the refrigerant 2.

 If the outside temperature does not drop below a predetermined value, for example -13bC hot water at 23 "C sprayed from the bottom 5 and the dispersers 11 can thus be collected at any point at a temperature of about 6'C in the collecting tank 7.

 As a variant, as shown in FIG. 3, it is possible to distribute the hot water in an area extending on either side of the half height H / 2 of the height H of the trickling device 2, in order to prevent any risk of freezing of the water at extremely low temperatures.

 In this fourth embodiment, each bypass pipe 14 has a vertical section 14a connected to the bottom 5 of the upper basin 4, and two branches 14b, 14c substantially horizontal.

The latter extend radially on either side of the mid-height H / 2 at determined heights, and are provided with water dispersers which are staggered radially from the outer periphery 9 of the volume 10. A valve 15 is interposed between the two horizontal branches 14b, 14c.

 When the temperature is not particularly low, the valve 15 can be kept closed, the hot water only flowing through the dispersers 11 of the upper horizontal branch 14b. On the other hand, if the atmospheric temperature drops to an extremely low value, for example -25 ° C., the valve 15 is open, and the hot water is then distributed between the two branches 14b and 14c. The height at which the water is dispersed from the lower branch 14c being less than H / 2, the hot water falling as rain from this branch 14c is mixed with the already cooled water falling from the bottom 5 and the upper branch 14b, which prevents any risk of freezing of all the water falling through the trickling device and then collected in the lower basin 7.

 Fig.4 shows a variant of the device of Fig.1 according to which the peripheral exchange surfaces 16 are interrupted substantially at mid-height, following a radial recess 17, and continue below it by a part peripheral 18 parallel to the upper part 16, inside the volume 10 of liquid runoff.

The pipelines 8.2 comprise horizontal branches 8.3 located at the level of the recess 17, and equipped with water dispersers It staggered radially from the inner end of the recess.

 Thanks to this arrangement, the water falling from the dispersers It cools less, and does not risk freezing on the periphery.

 In the embodiment of Figs 5 and 6, the trickling device 19 is. placed inside the base of the chimney 1. Its upper water distribution network 21 and its lower collection basin 22 can extend annularly as shown (Fig. 6), or occupy tolerates the base of the chimney 1. The runoff system comprises distribution and dispersion pipes 8.4, 8.5, ... constituting the upper assembly 21, and arranged for example in circular sectors of 90 degrees symmetrically with respect to a median radius XX of this sector.

 The pipes 8.4, 8.5, ... are completed by bypass lines such as 8.6 equipped, as well. that the pipes 8.4, 8.5, ... of water dispersers 11. The horizontal lower branches of the pipes 8.6 extend radially in the vicinity of the outer periphery of the runoff volume.

 The water dispersers 11 can be arranged in different ways in the annular zone 23 contiguous to the periphery of the base of the chimney 1, for example according to the provisions of FIGS. 2 or 2B.

 In the variant of FIG. 5A, the heat exchange surfaces have an interruption following a horizontal radial recess 17a compared to the recess 17, at which the water dispersers 11 of the bypass pipes 8.6 are placed, similarly to the arrangement of Fig.4 and with the same advantage.

 The antifreeze bypass lines 8, 8.1; 14, 8.2, 8.6 may alternatively be supplied by at least one pipe independent of the upper distribution networks formed by the assemblies 4, 5 and 21, 11.

Claims (11)

 1. Method for cooling a liquid in an atmospheric refrigerant (2) comprising an upper distribution network (21, 11; 4, 5) intended to receive hot liquid to be cooled, and a lower basin (7; 22) placed above below to collect the cooled liquid, characterized in that hot liquid dispersed is distributed in an area extending on either side of the mid-height (H / 2) between the upper distribution network and the basin collector inside the liquid runoff volume (10) between them and in the vicinity of the outer periphery of said volume.  2. Method according to claim 1, in which the distribution network comprises a basin (4) provided with a perforated bottom (5) from which the hot liquid can flow in dispersion, charac terized in that it is derived part of the hot liquid from the bottom (5) in an area extending on either side of the mid-height (H / 2) between the two basins and inside the volume (10) of runoff liquid between them and in the vicinity of the outer periphery of said volume.  3. Refrigerant. atmospheric for implementing the method according to one of claims 1 and 2, comprising an upper network (21, 71; 4, 5) for distributing a hot liquid to be cooled and a lower basin (7; 22) placed below to collect the cooled liquid, characterized in that it comprises means (8, 8.1, 11; 8.2, 8.3; 8.6) for distributing the hot liquid in dispersion in an area extending on either side mid-height (H / 2) between the upper distribution network and the collecting basin, inside the runoff volume (10) of the liquid between the latter and in the vicinity of the outer periphery of said volume.  4. Refrigerant according to claim 2, wherein the upper distribution network comprises a basin (4) which can be supplied with hot liquid and the bottom (5) of which is perforated to allow flow. hot liquid, by dispersion and runoff in a volume (10) delimited by the two upper (4) and lower (7) basins, this volume being traversed by a substantially horizontal flow of atmospheric air (F), characterized in that it comprises means (8, 8a, ...) for diverting part of the hot liquid from the perforated bottom (5) of the upper basin (4) in an area inside the volume (10) of runoff of the liquid, adjacent to its outer periphery, and which extends on either side of the mid-height (H / 2) between the two basins, said means being adapted to disperse the hot liquid in rain from this area.  5. Refrigerant according to claim 4, in which the upper (4) and lower (7) basins are annular and. arranged around the base of a chimney (1) for drawing atmospheric air, characterized in that the means for deriving the hot liquid comprise at least one pipe (8, 8a, ...) opening out on the one hand into a perforation in the bottom (5) of the upper basin (4), in the vicinity of the inner periphery of the upper basin, and on the other hand at its opposite end, inside the volume of dispersion (10) of the liquid and in the vicinity from its outer periphery.  6. Refrigerant according to claim 5, characterized in that several bypass lines each provided with liquid dispersers (11) at their lower end (8h, 8c, Ad) are distributed annularly under the upper basin (4).  7. Refrigerant according to one of claims 5 and 6, characterized in that the bypass line (14) comprises a section (14a) connected to the bottom (5) of the upper basin (4) and two substantially horizontal branches (14b , 14c) extending radially on either side of the mid-height (H / 2) between the two basins (4, 7) at determined heights, from which the liquid can be dispersed in rain , and a valve (15) is interposed between the two branches r this valve being open to supply liquid to the lower branch (14c) when the atmospheric temperature drops below a predetermined value.  8. Refrigerant according to one of claims 4 to 6, characterized in that the lower ends (8c, 8d) of the bypass pipes are equipped with water dispersers (11) offset radially (Fig.2A) or carried by circular sectors (12, 13) offset radially (Fig.2B), these dispersers being positioned in the vicinity of the outer periphery of the upper basin.  9. Refrigerant according to claim 3, in which the upper water distribution and dispersion network (21, 11) and the lower basin (22) extend inside the base of a chimney (1) for drawing atmospheric air, characterized in that the means for bypassing the hot liquid comprise conduits (8.6) which unravel on the one hand in the upper water distribution and dispersion network (21), and on the other hand in an area (23) adjacent to the outer peripheral of the runoff volume.  10. Refrigerant according to claim 9, characterized in that the lower ends of the bypass lines (8.6) are provided with water dispersers (11) staggered radially.  11. Refrigerant according to claim 3, characterized in that said means for distributing the hot liquid on either side of the mid-height (H / 2) comprise branch pipes supplied by at least one pipe independent of the networks of upper distribution (4, 5; 21, 11).