WO2012025696A1 - Flow plate for an air cooling tower, and air cooling tower comprising same - Google Patents

Abstract

The invention relates to a water flow plate (120) for an air cooling tower, comprising: a top portion (205) at which the water to be cooled arrives; a bottom portion (215) at which the cooled water exits; and an intermediate portion (210) extending, along an inclined plane, from the top portion to the bottom portion, in which the water flows due to the force of gravity and is cooled by partial evaporation, at least one of said portions having ribs (245, 250, 270, 275) on the surface thereof that contacts the water, said ribs being covered by the water, the intermediate portion (210) having rectilinear projections (240) which extend vertically in a flow direction of the water and which are suitable for supporting an identical plate. According to certain embodiments of the invention, the intermediate portion has transverse ribs (245) that are substantially rectilinear and perpendicular to the flow direction of the water.

Description

 FLOW PLATE FOR FRESH AIR TOWER AND FRESH AIR TOWER COMPRISING THE SAME

TECHNICAL FIELD OF THE INVENTION

 The present invention relates to a flow plate for a cooling tower and a cooling tower having it. BACKGROUND OF THE INVENTION

Cooling towers are compact devices for heat exchange between a liquid to be cooled, usually water, and air at ambient outside temperature. The physical process implemented is that of the evaporation of water in the air. As the latent heat of evaporation of water is very high, of the order of 2400 kJ kg ^-1 (at atmospheric pressure and 40 ° C), in comparison with the specific heat capacity (at constant pressure under the conditions normal temperature and pressure), of the order of 4.2 kJ kg ^"1 ° K ^{" 1} , the evaporation of a small proportion of the water is sufficient to cool the rest of the circulating water.

However, it has been known since 1976 that cooling towers can be the source of the vectorization of pathogenic bacteria, including bacteria of the genus Legionella, causing a potentially fatal respiratory disease, legionellosis. This vectorization is carried out by aerosols (a set of water particles in liquid form suspended in the air) that can be inhaled, the size of the water particles of which is between 0.5 and 6 micrometres, ie 0 , 5 to 6 10 ^-6 m.

The means for measuring aerosol size and number are recent and, for some of them, difficult to implement. Different methods exist. The manufacturers use the tracer salt method (consists in injecting a salt into the water of the circuit and seeking its presence in the water recovered by condensation at the exit of the towers, method of the Cooling tower Institute ("CTI"). impulse method or devices using 90 ° diffraction of white light both allow the counting of droplet populations and their size at the exit of the cooling towers, the manufacturers report the training level as a percentage of the flow of circulating water. An air-cooling tower is mainly composed of a water distribution system, a "packing" consisting of air and water contacting surfaces, a ventilation system and a ventilation system. water recovery system.

 Usual or improved devices, as disclosed in US Pat. No. 4,577,992 or WO 99/30096 or WO 94/21366 or WO 2009/054162 or US 2008/0236802 or GB 718929 or WO 93/03320 or US 4847019 or US 3952077 or GB 672244. for the distribution of water on the packing, are sprayers, rotating ramps, overflow systems that pour water on the packing. All these systems have the major defect of being aerosol generators even before the water flows on the packing. In addition, to increase the air-water contact area, certain patents such as US 2,517,639 or US 3,652,066 even aim at increasing the formation of the number of droplets.

 Cooling towers equipped with means for limiting droplet entrainment are known, for example droplet shields as disclosed in US Pat. No. 3,731,461 or United Kingdom Patent No. 2,206,683.

 Typical driving values for these turns are in the range of 0.01% to 0.06%. Once connected to the circulating flow, several tens of liters per hour are emitted in the form of aerosols of a few microns, which represents values of several billion microdroplets per hour. The droplet shields are therefore not effective enough to stop the microdroplets whose size is between 0.5 and six micrometers.

 These cooling towers emit aerosol water circuit, they generate a legionella risk. The treatment of this risk is too often to inject chemicals in an excessive amount. As a result, the risk of chemical pollution of the environment is high.

GENERAL DESCRIPTION OF THE INVENTION

The present invention aims to overcome these disadvantages by ensuring not to generate aerosol during air / water contact, to eliminate any risk of water dissemination of the circuit with a reduced manufacturing cost and maintenance (by attempting maintain the energy performance of conventional wet systems). The present invention aims to remedy these drawbacks and, in particular to reduce, or even eliminate the generation of aerosols or aerial microdroplets with a high yield and a reduced cost of manufacture and maintenance.

 The present invention also aims at eliminating the direct water entrainment of the circuit while being close to the energy performance of conventional towers by eliminating the impact of chemical discharges, reducing the visible plume formation, thus the visual nuisances and by preserving the ease of maintenance. The present invention also aims to overcome the disadvantages described above by ensuring not to generate aerosol during air / water contact.

 For this purpose, according to a first aspect, the present invention relates to a water flow plate of a cooling tower, characterized in that it comprises:

 - an upper part where the water to be cooled,

 - a lower part where the cooled water escapes and

 an intermediate portion extending, in an inclined plane, from the upper part to the lower part where the water flows under the effect of the force of gravity and is cooled by partial evaporation,

 at least one of said parts having ribs on its surface in contact with water, said ribs being covered by water,

 the intermediate portion having straight protrusions extending vertically in a direction of flow of water and adapted to support an identical plate.

 Thanks to these provisions, the distribution of the water is optimized on each part which has ribs. The speed of the water, relative to the air, which circulates generally against the current, can be uniform and optimized to avoid the formation of aerosol. The efficiency of the cooling tower can be optimized.

To form a cooling tower, similar flow plates are stacked, the stack constituting a block provided with numerous flow surfaces, at least one water inlet to be cooled and a cooled water outlet. . According to the variants, one or more blocks are superimposed or juxtaposed. This modular design reduces the cost and manufacturing complexity of the cooling tower. Thus, each block constituted by stacking of the flow plates is more rigid and more robust. The water flows parallel to each of the flow plates, without wave and without generating microdroplet.

 According to particular characteristics, the intermediate portion has transverse ribs covered by water.

 With these provisions, the flowing water is distributed uniformly over the entire width of the intermediate portion.

 According to particular features, the transverse ribs are substantially rectilinear and perpendicular to the flow direction of the water.

 The inventors have determined that these provisions are optimal.

 According to particular characteristics, the transverse ribs:

 - are spaced about five millimeters apart

 - have a trapezoidal section whose height is about a millimeter, the small base is about five millimeters and the large base is about six millimeters and a half.

 The inventors have determined that these provisions are optimal.

 According to particular characteristics, the upper part comprises a water inlet flange having ribs covered by water and parallel to the direction of flow of the water.

 According to particular characteristics, the upper part comprises a water distribution casing having ribs covered by water and parallel to the flow of water.

 According to particular features, the lower part has ribs at least partially curvilinear covered by water and parallel to the flow of water.

 According to particular features, the rectilinear protrusions extend vertically in a flow direction of the water and partition said water in separate areas.

 Each of these provisions contributes to the performance of the cooling tower and the reduction of its cost of manufacture and / or maintenance.

 According to particular characteristics, each flow plate is provided

 - above its upper part, a water casing and

- above its lower part, a water recovery sump.

These housings also reduce the risk of generation of microdroplets.

 According to particular features, the flow plate is symmetrical with respect to a vertical plane.

 According to particular characteristics, the flow plate is:

 - die casting,

 - made of a material loaded with reinforced fibers.

 Each flow plate, and therefore their stack, is thus easy to manufacture, lower cost and rigid.

 According to a second aspect, the subject of the present invention is a cooling tower comprising, superimposed, a plurality of water flow plates forming the subject of the present invention, the rectilinear projections of the intermediate portion of a flow plate supporting the immediately top plate in said tower.

 According to particular features, the tower object of the present invention comprises, superimposed, a plurality of water flow plates object of the present invention, the rectilinear protrusions of each plate delimiting zones of air passage between the two plates .

 According to particular features, each flow plate comprises:

 an upper part comprising at least one stackable water inlet piping element with identical elements of other flow plates so that all of these elements jointly constitute a straight tubular inlet water pipe, each said water inlet piping element having at least one water injection aperture on the flow plate,

 a lower part comprising at least one stackable water outlet pipe element with identical elements of other flow plates so that all these elements jointly constitute a straight tubular outlet pipe, each of which water outlet piping element having at least one water collecting opening,

 an inclined intermediate portion extending from the upper part to the lower part and being adapted to guide the injected water, in contact with the air to the lower part,

the stack of elements of each water inlet pipe being hermetic the water, injected into each water inlet pipe flowing by gravity on the intermediate parts of the flow plates to the water outlet piping.

 According to particular characteristics, the water inlet piping elements are, in the stack of the flow plates, nested in a male-female type socket.

 The assembly of the flow plates is thus facilitated and avoids intermediate parts.

 According to particular features, the tower is supplied with water to cool in at least one water inlet piping element of the lowest flow plate of each stack of flow plates, so that the water flows upward in the water inlet piping.

 In embodiments, the stack of elements of each water outlet pipe is hermetic.

 According to particular characteristics, the stack of the elements of each water outlet pipe is hermetic.

 According to particular characteristics, for each flow plate, the upper part has, at at least one of its ends, a lateral extension in which is arranged an opening associated with a flange provided with a seal.

 The hermeticity of the water inlet pipe to be cooled can thus be checked quickly since it is not surrounded by the other parts of the flow plates. In addition, the flange can be used to equalize the flow rates of water on the different flow plates. Finally, the seal increases the hermeticity of this inlet pipe to cool.

 According to particular features, the flange comprises ribs axes parallel to the direction of flow of water, defining the water inlet opening.

 By providing for a correct dimensioning of the flanges, the flow rates of water on the different flow plates are equalized.

 The advantages, aims and particular characteristics of this tower being similar to those of the plate object of the present invention, they are not recalled here.

BRIEF DESCRIPTION OF THE FIGURES

Other advantages, goals and special features of this invention will become apparent from the following description, made for an explanatory and non-limiting purpose, with reference to the accompanying drawings, in which:

 FIG. 1 represents, schematically and in side view, a particular embodiment of a cooling tower,

 FIG. 2 schematically and in plan view, the cooling tower illustrated in FIG. 1,

 FIG. 3 is a diagrammatic side view of a naked flow plate,

 FIG. 4 schematically and in plan view, the flow plate illustrated in FIG. 3;

 FIG. 5 represents, schematically and in perspective, the flow plate illustrated in FIGS. 3 and 4, as well as the additional parts that it carries,

 FIG. 6 schematically represents a detailed view of the flow plate illustrated in FIGS. 3 to 5;

 FIG. 7 schematically represents a water inlet flange of the flow plate illustrated in FIGS. 3 to 6;

 FIG. 8 represents, schematically and in section, the flange illustrated in FIG.

 - Figure 9 shows schematically and in a view from below, a water inlet casing of the flow plate illustrated in Figures 3 to 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

 It is noted that the figures are not to scale and that the outer coating of the tower is not shown.

The cooling tower illustrated in FIGS. 1 and 2 comprises, essentially, an air moving and evacuating part 102, a heat exchange part 104 and a water moving part 106. tower has three similar stages 108, 1 10 and 1 12 each having a stack of water flow plates 120, hot water inlet pipes 130 and cooled water outlet piping ( not shown). In other embodiments, the air-cooling tower comprises more or less three superposed or juxtaposed stages. As illustrated in particular in FIG. 2, the part 1 02 comprises a ventilation turbine 140 sucking air from a sheath 1 1 5, itself connected by connections 1 to the air flows circulating between two plates 120. In the embodiment shown, the circulations of the air and the water are carried out countercurrently, the water inlet connections to be cooled being located on the side of the upper part of each flow plate. 1 20.

 Each stage 1 08, 1 1 0 and 1 12 comprises a stack of a plurality of water flow plates 1 20, more precisely described with reference to FIGS. 3 to 6. Preferably, tie rods (not shown) are provided. at the corners of the flow plates 120 to stiffen their assembly in one of the stages 1 08, 1 1 0 and 1 1 2. The flow of water is thus carried out in parallel on the upper surfaces of the different plates flow 1 20 in contact with the air flowing between the surface of the water and the lower surface of the flow plate 1 20 immediately above.

 In the cooling tower, the formation of liquid aerosols or microdroplets is eliminated on three successive portions of each water flow plate, or "packing": during the distribution of the water in the upper part of the surface of exchange, during the flow of water on the exchange surface and during the recovery of water at the lower end of the exchange surface. The term "packing" is here taken in its most general sense of solid surface allowing the contact of water and air. And the increase of the exchange duration

 For this purpose, a water film bonded to the surface of the flow plate is created and the thickness and good distribution of the water over the entire surface is controlled. In addition, the flow rate of the water on the exchange surface is controlled so that the height of the ripples that form on this free-border flow is sufficiently low so that the ripples are not clipped by the flow. air. Finally, the film of water is recovered without passing through a flow of air.

 The initial distribution of water on the surface is important not to create aerosols during this distribution. Preferably, it implements a controlled thickness and bonded film overflow on the flow wall.

Once the water film of uniform thickness is distributed over the entire width of the flow plate, the inclination of its intermediate portion, its surface state, its hydrophilic or, on the contrary, hydrophobic properties, determine, in conjunction with the flow of air flowing, the speed of the water on the plate. Indeed, the water circulates by the effect of the force of gravity and its movement is uniformly accelerated by the gravity. This acceleration is controlled to limit the increase in the speed of water on the surface which causes the formation of wavelets.

 The inventors have determined that air speeds up to ten meters per second can be used.

 In the illustrated embodiment, the flow plates 120 are identical, symmetrical with respect to a vertical plane and superimposed within each of the three stages 108, 1 10 and 1 12.

 Typically, stages 108, 110 and 112 have identical dimensions and each have a number of water flow plates 120 between sixty and one hundred.

 The stages 108, 1 10 and 1 12 are separated by a few centimeters from each other. In the spaces between two stages are positioned parallelepipedal parts 145 which serve both to support the flow plates of the upper stage and, by a lateral surface, to the inlet or outlet of water, respectively by a water inlet pipe 130 or by a water outlet pipe (not shown).

 As illustrated in FIGS. 3 to 6, each water flow plate 120 comprises:

 a horizontal upper portion 205 comprising a water inlet piping element 235 having a lateral water injection opening on the flow plate 120,

 a horizontal bottom portion 215 comprising two elements 220 and 225 of water outlet piping, each said water outlet piping element having a water collecting opening,

 an inclined intermediate portion 210, typically at four degrees relative to the horizontal, extending from the upper part 205 to the lower part 215 and being adapted to guide the injected water, in contact with the air, up to at the bottom 215.

In the example shown, the upper 205, intermediate 210 and lower 215 portions are in the general form of rectangles having an identical dimension. The upper portion 205 has two lateral extensions or "ears" 230 and 235 forming elements of water inlet piping (in the described embodiment, only the elements 235 actually serve the water inlet and are provided, for this purpose, flanges 255 shown in Figures 5, 7 and 8). In the example shown, the elements 230 and 235 of water inlet piping are each in a square shape within which is arranged a circular opening adapted and to be traversed by water to cool , preferably in an upward movement.

 The lower portion 215 has two lateral extensions or "ears" 220 and 225 forming elements of water outlet piping. The two elements 220 and 225 of water outlet piping are each in a rectangular shape within which is arranged a rectangular opening with rounded corners suitable for discharging the cooled water flowing to the lower part 215.

 Alternatively, the upper portion 205 has two water inlet piping members and / or the lower portion 215 has a single water outlet piping element.

 The stack of the flow plates 120 form hermetic water inlet and outlet pipes so that the water, injected into each water inlet pipe, flows by gravity onto the intermediate portions 210 of the pipes. flow plates 120 up to the water outlet pipes.

 In one example, the intermediate portion 210 has a square shape, two of the edges of the square extending along two axes parallel to a direction of water flow.

 As illustrated in Figure 6, the intermediate portion 210 has ribs 245, preferably transverse, that is to say they extend perpendicular to the maximum slope and therefore to the flow of water and rectilinear. These ribs 245 preferably have a trapezoidal cut of height of about one millimeter, a small base of a length of about five millimeters and an angle of the sides of about 45 °, so that the large base measures about 6.5 millimeters. The space between two ribs is about five millimeters.

 It is noted that there are no transverse ribs on the first centimeters at the top and bottom of the intermediate portion 210, which makes it possible not to generate aerosol in these sensitive areas.

In the example, the lower part 215 of the flow plate 120 has, on its upper surface, curvilinear ribs 250 and rectilinear in the direction of flow of water, these ribs guiding the water to the pipe elements 220 and 225.

 As illustrated in FIG. 5, several additional pieces are associated with each water flow plate 120:

 the pipe element 235 comprises a flange 255 provided with a seal 260,

the upper part 205 is surmounted by a casing 280 and

 the lower part 215 is surmounted by a casing 265.

 Each casing 265 and 280 has bores intended to be traversed by fastening means (not shown) for fixing the casing to the flow plate 120. In a variant, the casings 265 and 280 are glued, screwed or clipped to the plate flow 120.

 The flange 255 illustrated in FIGS. 7 and 8 has a generally circular shape and a rectangular lateral opening provided with ribs 270 extending parallel to the flow of water. The spaces between the ribs 270 have an increasing width in the direction of flow of water and deviate from the upper plane of the upper portion 205 so that the water flows substantially uniformly at the outlet of the flange 255 .

 Thanks to the profile of the flange 255, illustrated in FIG. 8, the water inlet piping elements are, in the stack of the flow plates 120, hermetically fitted in a male-female interlock and allow the uniform distribution of the water flow between the different plates 120.

 The flanges 255 make it possible to equalize the flows between the different superimposed flow plates.

 As illustrated in Figure 9, the housing 280 has ribs 275 parallel to the direction of flow of water. In a preferred example, the length of housing 280 is 1.2 meters and the number of ribs 275 is forty-five. Each rib

275 has a width of 2 millimeters and the gap between two ribs is 26.5 millimeters.

 Each flow plate 120 has a protruding contour and intermediate projections 240 forming a support for the immediately superior flow plate 120 in the stack. The distance between the flow plates 120 and therefore the height of the intermediate projections 240 is of the order of fifteen millimeters.

In the example, each pipe element has tapered lugs hollow extending perpendicularly on either side of the flow plate 120, so that the stack of the flow plates 120 is facilitated.

 In one example, each flow plate 120 is molded under pressure and made of a material loaded with reinforced fibers, for example of the polyester type.

 The cooling tower is fed by a pump (not shown) injecting the liquid to be cooled into the water inlet pipe element 130 of the lowest flow plate 120 of each stack of flow plates 120. so that the water circulates upward in the water inlet piping.

 The other elements of the water setting portion 106 are known to those skilled in the art and are therefore not recalled here.

 If it were necessary to carry out a curative cleaning, for example following an accidental scaling deposit, it is planned to be able to circulate a chemical product in closed loop in the air-cooling tower. This possibility of working in closed circuit makes it possible to process only the reduced volume of the tower, that is to say the sum of the volume of liquid in the water tank, the volume of liquid in the modules and the volume of liquid in the supply piping of the modules. Practically the closed loop will be achieved by temporarily integrating a pump to feed the water tank (containing the cleaning product), the module via a specific flange on the supply pipe. The delivery container of the cleaning product will be used, after the operation, to collect the volume of used liquid drained by the pump.

Claims

1. Water drainage plate (120) of a cooling tower, characterized in that it comprises:  - an upper part (205) where the water to be cooled,  - a lower part (215) where the cooled water escapes and  an intermediate portion (210) extending, in an inclined plane, from the upper part to the lower part where the water flows under the effect of the force of gravity and is cooled by partial evaporation,  at least one of said portions having ribs (245, 250, 270, 275) on its surface in contact with water, said ribs being covered by water, the intermediate portion (210) having straight projections (240) extending vertically in a direction of flow of water and adapted to support an identical plate.  2. Plate (120) according to claim 1, wherein the intermediate portion (210) has transverse ribs (245) covered by water.  3. Plate (120) according to claim 2, wherein the transverse ribs (245) are substantially rectilinear and perpendicular to the direction of flow of water.  The plate (120) according to any one of claims 2 or 3, wherein the transverse ribs (245):  - are spaced about five millimeters apart  - have a trapezoidal section whose height is about a millimeter, the small base is about five millimeters and the large base is about six millimeters and a half.  Plate (120) according to any one of claims 1 to 4, wherein the upper portion (205) comprises a water inlet flange (255) having ribs (270) covered by water and parallel in the sense of flow of water. The plate (120) according to any one of claims 1 to 5, wherein the upper portion (205) comprises a water distribution casing (280) having ribs (275) covered by water and parallel to the flow of the water.  7. Plate (120) according to any one of claims 1 to 6, wherein the lower portion (215) comprises ribs (250) at least partially curvilinear covered by water and parallel to the flow of water .  A plate (120) according to any one of claims 1 to 7, wherein the straight projections (240) extend vertically in a direction of flow of water and partition said water in separate areas.  9. Plate (120) according to any one of claims 1 to 8, which is provided  - above its upper part (205), a housing (280) for water distribution and  - above its lower part (215), a housing (265) for water recovery.  10. Plate (120) according to any one of claims 1 to 9, which is symmetrical with respect to a vertical plane.  1 1. Plate (120) according to any one of claims 1 to 10, which is: - die casting,  - made of a material loaded with reinforced fibers.  12. Cooling tower comprising, superimposed, a plurality of plates (120) of water flow according to any one of claims 1 to 1 1, the rectilinear projections (240) of the intermediate portion of a flow plate supporting the immediately superior plate in said tower.  13. The tower of claim 12, comprising, superimposed, a plurality of plates (120) of water flow according to claim 8, the rectilinear projections (240) of each plate defining air passage zones between the two. plates.  14. Cooling tower according to one of claims 12 or 13, wherein each flow plate comprises: an upper part (205) comprising at least one stackable water inlet piping element (235, 255) with identical elements of other flow plates so that all of these elements together constitute tubular piping; straight water inlet, each said water inlet piping element having at least one opening (270) for injecting water onto the flow plate, - a lower part (215) comprising at least one stacking water outlet pipe element (220, 225) with identical elements of other flow plates so that all of these elements together constitute straight tubular piping water outlet, each said water outlet pipe element having at least one water collecting opening,  an inclined intermediate portion (210) extending from the upper part to the lower part and being adapted to guide the injected water, in contact with the air to the lower part, the stack of elements of each water inlet pipe being airtight water, injected into each water inlet pipe flowing by gravity on the intermediate parts of the flow plates to the piping of water outlet.  The tower of claim 14, wherein the water inlet piping members (235, 255) are, in the stack of flow plates, nested in a male-female socket.  16. Tower according to any one of claims 14 or 15, which is supplied with water to be cooled in at least one water inlet pipe element. (235, 255) of the lowest flow plate (120) of each stack (108, 1 10, 1 12) flow plates, so that water flows upward into the water inlet piping.  Tower according to any one of claims 14 to 16, wherein the stack of the elements of each water outlet pipe (220, 225) is hermetic.  Tower according to any one of claims 12 to 17, wherein, for each outlet plate (120), the upper part has, at at least one of its ends, a lateral extension (235) in which is arranged an opening associated with a flange (255) provided with a seal (260).  19. A lathe according to claim 18, wherein the flange (255) comprises ribs (270) with axes parallel to the direction of flow of water, defining the water inlet opening.