FR2713323A1 - Air cooling tower for heat exchangers used in building air conditioning systems - Google Patents

Abstract

The cooling system for a fluid circulating in a finned exchanger by movement of air, caused by a fan (15) driven by a motor (16), has a gallery (9) for spraying water on the exchanger. There is a recovery tray (1) for the sprayed water and an outlet compartment of large section. This outlet compartment communicates with the tray through an opening of large section in the wall of the tray bottom. In the lower part of the compartment is a horizontal outlet pipe. The ratio of the section of the outlet compartment to that of the emptying and recycling pipe is preferably greater than 2 and less than 10. The outlet compartment has a flange in its upper part fixed onto the lower face of the tray bottom. A guidance grille is located in the upper part of the outlet compartment and a filter is located on top of the grille.

Description

 The present invention relates to improvements made to atmospheric air coolers and more particularly to cooling devices or cooling towers using water spray bars on an exchanger (generally finned) in which a fluid to be cooled circulates, which sprinkling of water causes a runoff of water on the external surface of said exchanger, which runoff operates against the current or parallel to the current (co-current) of cooling air.

 The technical field of the invention is that of the manufacture of heat exchangers.

 The general objective of the present invention is to improve the compactness of such cooling devices by reducing their height while improving their operating efficiency and reducing their cost of construction, installation and maintenance.

 Indeed, cooling devices of this type are frequently installed as part of air conditioning or building cooling installations, on terraces of office buildings, residential or industrial buildings, and their height must be limited; moreover, silent operation of these devices is most often required.

 Already known from US Pat. No. 2,752,124 (NOFZIGER) a cooling tower comprising a box containing a tube exchanger and comprising a pipe for spraying the exchanger with water which is recovered in a tank located in part lower of the box, and comprising an air circulation fan; the device described in this document comprises a partition whose lower edge plunges into the water recovered in said tank of said device and which tank is equipped with an overflow pipe and a drain pipe fixed to the bottom of said tank.

 The device described in this document provides a hydraulic valve thanks to said partition between the internal and external parts of the water recovery tank; however the device described in this ~ document comprising ventilation "co-current" with the sprayed water has drawbacks: the arrangement of the components of this device results in a significant height of the cooling tower and a relatively low thermodynamic efficiency.

 Also known from patent application FR92 / 08557 filed on 07/03/92 in the name of the applicant, improvements to trickle cooling towers in which a hydraulic valve causing a large difference in height between the two parts of a tank, separated by a partition immersed in the water of the tank, improves the performance of these devices, with ventilation against the current with respect to the sprayed water spraying the external surface of the exchanger in which the fluid to be cooled circulates.

 Because in the lower part of these devices, one or more water outlets are provided in the spray water collection tank, as shown in Figures 3a and 3b of this application, the outlet pipes arranged laterally (mark 3 figure 3a) or constituted by an elbow fixed in the bottom of the tank (mark 4 figure 3b) have drawbacks: these arrangements entail a significant height of guard (mark hl figures 3a and 3b) necessary in order to avoid aspiration of air by a vortex or vortex phenomenon appearing in the water located in the tank, which vortex phenomenon is due to a high speed of water leaving the tank, and which phenomenon is accentuated during the presence of eddies in the tank water; this air suction phenomenon can cause a malfunction of the water recycling pumps, as well as sound and vibration effects in the pipes and in the devices cooled by the recycled water and can also be the cause of corrosion in the installation; the large headroom required also contributes to a significant height of water in the tank, which increases the height and weight of these cooling devices.

 Furthermore, these arrangements of the outlet pipes complicate the production of a water filtration strainer (allowing the retention of impurities) generally located at the bottom of the tank, and moreover makes the installation of such a device dependent on the 'orientation of the water outlet piping for recycling (ref 11 figure 4), the "overflow" evacuation pip ref 12 fig 4) as well as the drain pipe (ref 13 fig 4); a complex set of piping is thus usually obtained which complicates the installation and maintenance of a tower and increases the cost thereof.

 The problem is therefore to remedy the various drawbacks mentioned above of the known cooling devices.

 The solution to the problem posed consists in providing a device for cooling a fluid circulating in a finned exchanger cooled by an air circulation caused by a fan driven by a motor, which device comprises a spray bar of said exchanger by means of l , which device comprises at least one container for recovering the sprinkling water, which device comprises an outlet compartment of large cross section, which outlet compartment communicates with said tank through an opening of large cross section, provided in the wall bottom of said tank, which outlet compartment is equipped in the lower part with at least one substantially horizontal outlet pipe, of section much smaller than said section of said outlet compartment.

 In other words, the invention consists in providing a cooling device such as a cooling tower or an atmospheric air cooler, intended to cool a fluid circulating in a finned exchanger cooled by an air circulation caused by a fan driven by a motor, which device comprises a ramp for spraying said exchanger with water, which device comprises at least one tank, preferably in two parts, communicating and partially separated by a partition, which tank allows the recovery of water from 'sprinkling, which device comprises an outlet compartment, for example of circular cylindrical section with a vertical axis, allowing the evacuation of the sprinkling water recovered in said tank, which outlet compartment has a large section, measured substantially according to a plane perpendicular to a vertical axis, which outlet compartment communicates with said tank through an opening of imp section ortante, substantially identical 9 said section of said outlet compartment, which opening is provided in the bottom wall 6, substantially horizontal, of said tank, which outlet compartment is equipped in the lower part with at least one outlet pipe or a nozzle, substantially horizontal, of section much smaller than said section of said outlet compartment, which outlet compartment is preferably equipped with a water outlet pipe for its evacuation and recycling and a substantially drain pipe.

 Advantageously, the ratio of said section of said outlet compartment to said section of the evacuation and recycling pipe and at least equal to 1.5, preferably greater than 2 and less than 10.

 Advantageously, said outlet compartment is provided in its upper part with a flange, for example circular, which flange is fixed on the underside of said bottom of said tank, so that said outlet compartment is easily removable and can be oriented relative to the cooling device.

 Advantageously said device further comprises a guide device such as a grid, located in the upper part of said part compartment.

 Advantageously, said device also comprises a substantially flat strainer and disposed in the upper part of said outlet compartment, preferably disposed above or on a guide grid.

 Advantageously, said device comprises a water evacuation pipe intended to prevent overflow of said tank from said device or "overflow" pipe, which pipe is mechanically connected to said outlet compartment, which pipe has an upper part preferably extending substantially vertically along an axis parallel to the axis of symmetry of said compartment, for example in the vicinity of said axis of vertical symmetry and of revolution.

 Advantageously, said device comprises a grid for guiding the water, which comprises substantially radial blades, that is to say extending in planes perpendicular to the vertical axis of symmetry of said substantially cylindrical outlet compartment.

 Advantageously, said device a guide grid comprising blades situated in substantially vertical planes and perpendicular to each other.

 Advantageously, said outlet compartment is of circular cylindrical section and comprises said water outlet and recycling pipe and said drain pipe arranged substantially radially.

 Advantageously, said outlet compartment is mechanically linked to a drain pipe for said tank by "overflow", which pipe is connected to said drain pipe by means of a drain valve.

 The numerous advantages provided by the invention will be better understood through the following description which refers to the appended drawings, which illustrate without any limiting character, particular embodiments of the invention.

 Figure 1 schematically describes in section through a vertical plane a cooling device of known type in which the air circulation is "co-current" of the spray water, according to the arrows F.

 FIG. 2 shows in section through a substantially vertical plane another type of known cooling tower in which the air circulation takes place according to the arrows F against the flow direction of the spraying water.

 Figures 3a and 3b schematically illustrate known solutions for discharging the water located in the water recovery tank of a cooling device.

 FIG. 4 also illustrates a known type of cooling device and outlets for the water recovered in the tank.

 FIG. 5 schematically illustrates an outlet compartment provided at the lower part of a water recovery tank of a cooling device according to the invention.

 Figures 4, 5 show cooling devices by a schematic section in a transverse vertical plane.

 Figures 6a and 6b show preferred embodiments of an outlet compartment according to the invention.

 Figures 7a and 7b show alternative embodiments of an outlet compartment according to the invention.

 FIG. 8 illustrates in section through a transverse vertical plane a particular embodiment of a cooling device according to the invention.

 Referring to Figures 1, 2 and 4 illustrating known embodiments of trickle cooling tower, these devices usually include an electric motor 16 driving by means of a belt a fan 15 sucking the outside air and circulating the air according to the arrows F (FIGS. 1 and 2) is in the same direction as the direction of circulation of the water sprayed by a spraying boom 9, or against the current as shown in FIG. 2.

 These known devices comprise, placed under said spraying boom 9, an exchanger 10, for example a finned tube exchanger. the fluid to be cooled circulating inside the tubes (not shown).

 The lower part of the box or of the structure of these devices constitutes a tank 1 for recovering the water coming from the spray boom 9, which tank 1 can be separated into two parts 1a and 1b as illustrated in FIGS. 1, 2 and 4, thanks to the presence of a partition 7 partially separating said tanks, which allows the arrangement of a hydraulic valve between said compartments of said tank causing a difference in height DH between the water level in each of the two compartments due to the pressure exerted by the fan.

 Said box is provided at the bottom with feet 2 allowing the box to rest on the ground, the total height H of these devices being generally large; in the lower part of the tanks are generally provided, a recycling pipe 11 (Figures 2 and 4), a drain pipe 13 (Figures 1, 2 and 4) fitted with a drain valve 17, and if necessary a line 12 of overflow or overflow to avoid an excessive increase in the level of water in the tank.

 As illustrated in FIGS. 3a and 3b, the evacuation of the water in the tank by a recycling pipe having a substantially horizontal lateral outlet (reference 3 in FIG. 3a) or else via an outlet pipe for recycling water (marked 4 in FIG. 3b) which is bent and linked to the bottom 6 of the tank, causes the appearance of vortices 5 which can cause the aspiration of air in said water recycling pipes 3, 4; to avoid the aspiration of air, it is necessary to provide a significant height of water H1 in the tank causing a height of water H2 relative to the ground also significant due to the vertical size of the outlet pipe ( Figures 3a and 3b).

 According to the invention, in order to remedy the problems of the devices of the prior art, provision is made in the bottom 6 of the tank for collecting the spray water, a large opening 8 allowing said tank to communicate with an outlet compartment 14 of large section (that is to say large in front of the section of the outlet pipes 11 and 13) shown in FIG. 5 in particular.

 With reference to FIGS. 6a, 6b, 7a, 7b, it can be seen that according to a preferred embodiment of an outlet compartment 14 according to the invention, said compartment 14 can be constituted by a substantially cylindrical casing 14a, of vertical axis , for example of circular cross-section, and of large cross-section relative to the cross-section of the recycling 11 and drain 13 pipes.

 Said compartment 14 may further comprise a flange 14b, for example substantially circular, located in the upper part of the compartment and fixed to the upper part of said envelope 14a which flange 14b allows the fixing of said compartment to the wall 6 forming the horizontal bottom of the tank 1 cooling devices.

 Sealing devices, not shown, are of course provided for the connection between said flange 14b and the bottom 6 of said tank, the interior section of said flange and said casing 14a being for example identical to the section of opening 8 provided in said wall 6.

 As shown in Figures 6a and 7a, an anti vortex or anti vortex device, essentially constituted by a grid 19 can be provided in the upper part of said compartment 14, which grid 19 can be equipped with a handle l9a in the upper part (Figure 7a) , allowing the fitting and removal of said grid without dismantling said outlet compartment 14.

 As shown in FIG. 7a, said compartment 14 is limited in the lower part by a bottom 14c which can be located at a distance very close to the ground on which the device rests, said compartment 14 being equipped with said pipes 11, 11a, 13, 13a which are advantageously arranged radially, that is to say along planes perpendicular to the vertical axis of symmetry of said compartment 14 and / or of said cylindrical envelope 14a.

 In the embodiment shown in FIG. 6a, an overflow pipe 12 is provided which is mechanically connected to said compartment 14, and which comprises an upper part 12a open at its end through which water can penetrate when the level in the tank exceeds the end of said pipe 12a, which pipe therefore comprises a substantially rectilinear upper part extending vertically, passing through said grid 19, forming an elbow and crossing the wall of said compartment 14 to come in its lower part 12b to join in a lost water pipe 18, the outlet of a valve 17 provided on the drain pipe 13, the whole forming a compact assembly capable of being disassembled and being oriented relative to the bottom 6 of the tank of said tower cooling.

 As shown in FIGS. 6b and 7b, said grid 19 may comprise substantially vertical blades 191 and 192 situated in planes perpendicular to each other and may, as shown in FIG. 7b, radial blades 193, said blades 191, 192.

193 allowing the guiding of the water leaving said tank of said tower, and thus preventing the formation of vortices.

 In the particular embodiment shown in FIG. 8, said tower is installed in a box 23 containing all of the components of said tower, which box 23 has a lower sheet 6 forming the bottom of the runoff recovery tank equipped with 'An outlet device 14 according to the invention comprising said grid 19 and said water outlets 11, 13 and 12 in the embodiment shown in this figure, the pipe 21 for the supply of spray water and / or the inlet pipe for the fluid to be cooled in the exchanger is located on the same side as said fan driven by said motor 16, the assembly being located inside said box 23; an opening 24 is provided in a wall 22 of said box 23, the section of which is such that the speed V1 of the air entering said box through said opening 24 is such that its ratio to the speed V2 of the air leaving said turn is between 0.8 and 1.2 in order to limit the flow noises and also to avoid possible recycling of the air by suction by the fan of a part of the air leaving through the upper zone of the cooling tower.

Claims (10)

 1. Device for cooling a fluid circulating in a finned exchanger (10) cooled by an air circulation caused by a fan (15) driven by a motor (16), which device comprises a spraying boom (9) of said water exchanger, which device comprises at least one tank (1) for recovering spray water, which device comprises an outlet section (14) of large section, which outlet compartment communicates with said tank by an opening (8) of large section provided in the wall (6) of the bottom of said tank, which outlet compartment is equipped in the lower part with at least one outlet pipe, substantially horizontal, of section much less than said section of said outlet compartment.  2. Device according to claim 1 wherein the ratio of said section of said outlet compartment to the section of the pipe (11) for evacuation and recycling and at least equal to 1.5, preferably greater than 2 and less than 10.  3. Device according to any one of claims 1 to 2 wherein said outlet compartment is provided in its upper part with a flange (14b), fixed on the underside of said bottom (6) of said tank (1).  4. Device according to any one of claims 1 to 3 further comprising a guide device (19) such as a grid, located in the upper part of said outlet compartment (14).  5. Device according to any one of claims 1 to 4 further comprising a strainer (20) substantially planar and disposed in the upper part of said outlet compartment. preferably disposed above a guide grid (19).  6. Device according to any one of claims 1 to 5 comprising a pipe (12) of "overflow", mechanically connected to said outlet compartment (14).  7. Device according to any one of claims 1 to 6 comprising a grid (19) for guiding the water which comprises blades (193) substantially radial.  8. Device according to any one of claims 1 to 7 comprising a grid (9) for guiding comprising blades (191, 192) located in vertical planes substantially perpendicular to each other.  9. Device according to any one of claims 1 to 8 wherein said outlet compartment (14) is of circular cylindrical section and comprises said pipe (11) for output and recycling of water and said pipe (13) for emptying arranged substantially radially.  10. Device according to any one of claims 1 to 9 wherein said outlet compartment is mechanically linked to a pipe (12) for evacuating said tank by "overflow", which pipe (12) is connected to a pipe ( 13) drain via a drain valve (17).