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(11) | EP 1 621 841 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Spray device with a non-circular spray pattern |
| (57) The sprayer according to the present invention comprises an upstream nozzle (4) which
emits an inlet jet of a liquid to be sprayed against a conical projection (6) of a
deflector (5). A first fraction of the inlet jet enters the dividing aperture (11) located on the top of the conical projection (6) and is directed against a propeller (13). A second fraction of the upstream jet flows along the external sides of the conical projection (6), is diverted, by means of the base extensions (10) positioned at the base of the conical projection (6), and projected in directions transverse to the inlet jet. The propeller (13) uniformly distributes the first fraction of the inlet jet over a circular area to be sprayed, while the deflector (5) concentrates the second fraction of the inlet jet on one or more zones outside the circular area to be sprayed, thereby obtaining uniform spraying of an overall area, which can, for example, be square in shape. |
Field of the invention
[0001] The present invention relates to a sprayer suitable to spray with a liquid and with predetermined uniformity even a non-circular zone of a predetermined surface; a sprayer of this type can be used, for example, in cooling towers with gas/liquid crossflow.
Prior art
[0002] In crossflow or countercurrent cooling towers, heat exchange is known to be obtained between a gaseous medium and a liquid by spraying the liquid - for example water - in droplet form from above onto a body of grids packed together, and by causing an ascending gas current to flow through these packed grids; some examples of these grids are described in the European patents EP 311 794, EP 503 547, EP 1 152 205, EP 931 239, US2003/0183956A1.
[0003] To increase the efficiency of the cooling tower it is necessary to distribute the liquid to be sprayed in the droplet form as uniformly as possible on the packs of grids; for this purpose the liquid can be sprayed with appropriate sprayers, some examples of which are described in the patents EP 654 649 and US 4 111 366.
[0004] These and other sprayers currently known in the art, characterized by the presence of a propeller or impeller made to rotate by the liquid which is directed against it, are able to distribute said liquid in a relatively uniform way over an area of an essentially circular shape below said nozzle, or to spray an area below also with non-uniform distributions, but in any case obtaining distributions with circular symmetry.
[0005] Therefore, when it is necessary to spray a vast area of cooling grids with several sprayers, the circular areas sprayed must be partly overlapped by adjacent sprayers, or these areas must be approximately tangent in some points; in any case, the total area will be sprayed with less uniformity than the single circular areas sprayed by a single sprayer.
[0006] The object of the present invention is to provide a sprayer with a plurality of which a given area even with a non-circular shape - for example square, rectangular, triangular or polygonal - can be sprayed with greater uniformity compared to prior art sprayers.
Summary of the invention
[0007] According to the present invention, this object is attained with a sprayer suitable to spray a predetermined area with a sprayed liquid, said sprayer comprising:
- circular spraying means suitable to spray, with a sprayed liquid and with a predetermined degree of uniformity, an internal spraying zone substantially circular or rounded in shape;
- peripheral spraying means suitable to spray with the sprayed liquid an external spraying zone positioned around, and at least partly outside of, the internal spraying zone. This sprayer is characterized in that the peripheral spraying means have a deflector suitable to be hit by one or more jets of liquid to be sprayed and to divert and direct at least part of this jet or these jets towards at least part of the external spraying zone so that said at least part of the external spraying zone substantially forms a projection of the internal spraying zone.
[0008] A single sprayer as defined above can spray, relatively uniformly, an area therebelow, even non-circular in shape, such as a square, rectangular, triangular or more generally polygonal area: with a plurality of sprayed areas with these shapes it is possible to cover a larger area with fewer overlapping zones between areas sprayed by two adjacent sprayers, and therefore to spray the total area with greater uniformity. With the same total sprayed surface it is therefore possible to reduce the consumption of sprayed liquid and increase the efficiency of the cooling tower, or of a more general spraying system.
[0009] Further advantages attainable with the present finding will be more apparent to those skilled in the art from the following detailed description of a particular nonlimiting embodiment, with reference to the following figures.
List of the figures
[0010]
Figure 1 schematically shows a perspective view of a sprayer according to a preferred embodiment of the present invention;
Figure 2 schematically shows a side view, partly sectioned, of the sprayer in Figure 1;
Figure 3 schematically shows a view of the propeller of the sprayer in Figure 1 according to the direction of the axis of rotation of said propeller;
Figure 4 schematically shows a top view of the approximately square zone sprayed with the sprayer in Figure 1, with predetermined spraying uniformity.
Detailed description
[0011] In the present description the expressions "downstream" and "upstream" refer to the flow of liquid to be sprayed, in the sense that, if a particle of fluid during operation of the nozzle first reaches the element A and then the element B, the element A is said to be upstream of the element B.
[0012] Moreover, in the present description "distribution with circular symmetry" is intended as a distribution, in particular of density of droplets, uniform in the points positioned at the same radial distance from a central point of said distribution.
[0013] The sprayer 1 in Figures 1-3 comprises an upper fixing body 2 which can be connected, by means of the connection 3 - which can for example be a threaded, bayonet or yet another type of connection - to a suitable supply duct of the liquid to be sprayed, such as water or another liquid; a plurality of sprayers 1 can, for example, be disposed over a mass of trickle grids of a cooling tower, to be sprayed with water or another liquid to be sprayed.
[0014] A jet of liquid to be sprayed - jet referred to as "inlet jet" in the following description - is delivered from the nozzle 4 - referred to in the following description as "upstream nozzle 4" - and is directed against the deflector 5, which comprises a conical part 6 projecting in the direction of impact of the upstream jet against the deflector and facing away from said jet, and a flange 7, located at the base of the conical projecting part 6 and having an external perimeter with an approximately square shape in the plane; preferably, although not necessarily, the flange 7 has a slightly convex upper surface - facing towards the upstream nozzle 4 - in the direction of flow of the liquid to be sprayed thereon; said convex shape promotes concentration by the water to be sprayed at the corners of the flange 7 - i.e. in the four external spraying zones ZE in Figure 4, hatched - and uniform distribution of water on said flange 7.
[0015] In the present embodiment, the deflector 5 is fixed with respect to the rest of the structure of the sprayer.
[0016] Two upper supporting arms 8 are coupled at the centre line of two of the sides of the square flange 7, to connect the deflector 5 to the part of the upstream nozzle 4 and of the threaded connection 3; two dividing crests 9 (Figure 1) are provided at the centre line of the other two sides of the square flange 7, suitable to promote diversion of the flow of liquid to be sprayed which, as will be seen in greater detail hereunder, flows on the external surface of the conical part 6, towards the corners 10 of the square flange 7.
[0017] The upper supporting arms 8 have, at least in the area in which they join the deflector 5, flattened cross sections, hydrodynamic in shape and oriented parallel to the direction of flow of the liquid to be sprayed on the conical projection 6 and, just as the crests 9, also provide means to divide the flow ― in the present description also called second flow dividing means - suitable to contribute towards diverting the flow of liquid to be sprayed, which flows on the external surface of the conical part 6, towards the corners 10 of the square flange 7.
[0018] The dividing crests 9 and the flattened coupling zones of the arms 8 on the deflector 5 - i.e. the second flow dividing means 8, 9 - also promote detachment of the water from the surface of the flange 7 and facilitate delivery of the water from the sprayer fragmented in droplets instead of as a jet in sheet form.
[0019] On the top of the conical projection 6 is a hole 11, also called dividing aperture 11, which extends inferiorly, inside the conical projection 6, with a tubular extension 12, or in any case defines a tubular length of duct 12 - in the present description also indicated as "guide duct 12" - the axis of which is substantially parallel to the axis of the inlet jet incident on the deflector 5.
[0020] Positioned under the deflector 5 is a propeller 13, with axis of rotation coaxial with the tubular guide duct 12 and suitable to distribute the liquid with predetermined uniformity over a substantially circular area, which hits said propeller and causes it to rotate.
[0022] The inlet jet, of water or another liquid to be sprayed, is delivered from the upstream nozzle 4 and is incident against the top of the conical projection 6. The dividing aperture 11 is opposite and coaxial with the upstream nozzle 4 and has a smaller inlet section than the outlet section of the upstream nozzle, so that only part of the flow of liquid incident on the deflector ― hereinafter referred to as "first fraction of liquid to be sprayed" - enters the tubular duct 12, while the remaining part - hereinafter referred to as "second fraction of liquid to be sprayed" - flows along the sides of the conical projection 6 and is diverted by the flange 7; for this purpose, the edges 14 of the dividing aperture 11 - in the present description also referred to as dividing crest 14 - preferably have the shape of cutting edges or in any case a tapered hydrodynamic shape, in order to divide the incident flow with greater precision and less turbulence.
[0023] The first fraction of liquid to be sprayed enters the aperture 11 and, after passing through the tubular duct 12, is ejected against the propeller 13, causing it to rotate; among other things, the duct 12 has the function of:
- containing and guiding the flow of liquid to be directed towards the propeller 13, preventing it from dispersion or break-up;
- reducing turbulence inside the jet directed against the propeller 13, compared, for example, to the case of a free jet in the air.
[0024] The rotating propeller 13 distributes part of the liquid supplied to the sprayer 1 with a predetermined distribution uniformity on an area with a square surface - hatched line L1 in Figure 4 - positioned below said sprayer 1.
[0025] The tubular duct 12 has the function of containing, maintaining compact and guiding the flow of the first fraction of liquid to be sprayed, in order to direct it more efficaciously against the propeller 13.
[0026] The second fraction of liquid to be sprayed, after having flowed on the external surface of the conical projection 6, reaches the flange 7 and is thrust by the second dividing means 8, 9 towards the four zones of the corners of the square flange 7, in the following description also referred to as "base extensions 10"; in this way the four base extensions 10 concentrate the flow of sprayed liquid delivered from the flange 7 at the four corners and along the diagonals of said flange 7, giving rise to four projections of the area below sprayed by the sprayer - i.e. in the aforesaid four external spraying zones ZE in Figure 4 - at the corners of the square or rectangular area to be sprayed. In Figure 4 the dash-dot lines L2 indicate the perimeter of the square area to be sprayed, and the continuous wavy line L3 schematically indicates the boundaries of the zone effectively sprayed by the sprayer in Figure 1 with predetermined degree of uniformity.
[0027] In this way it is possible to obtain relatively uniform distributions of liquid to be sprayed, even with a non-circular shape or circular symmetry; in the present embodiment, the deflector 5 is suitable to spray with predetermined uniformity an area with an approximately square shape - line L3 in Figure 4 - although other embodiments not shown can also spray, with predetermined uniformity, areas of other shapes, such as rectangular, triangular, rhombic, polygonal, star-shaped; sprayed areas with similar shapes can be juxtaposed or partly overlapped with one another, arranging a plurality of sprayers according to the present invention according to a suitable network, in order to spray a wider area - for example the entire filling of a cooling tower - with greater uniformity than obtained by overlapping the circular sprayed areas obtained with prior art sprayers.
[0028] Another important advantage of the sprayer 1 described hereinbefore lies in the fact that the shape and dimensions of the area sprayed with substantial uniformity by the sprayer 1 remains substantially unvaried -approximately square in the example in Figures 1-4 - irrespective of variations in the supply pressure in the interval from 40 to 120 cm of the head of water: in fact, in a prior art sprayer, in which a propeller or impeller sprays water on a substantially circular spraying area, by increasing the head of water the diameter of the spraying area also increases. Instead, in the example of sprayer in Figures 1-3 it has been found that this substantially does not happen, or happens to a much lesser extent, and it is believed that the rotating propeller 13 creates pneumatic depression which tends to close the umbrella-like jet of the water propagating from the flange 7, compensating the increased divarication of said umbrella-like jet caused by an increased supply pressure of the water.
[0029] Preferably, the outlet section of the upstream nozzle 4 and the dividing aperture 11 are opposite and coaxial with each other and - as in the present embodiment, in which both have a circular section - the outlet section of the of the upstream nozzle 4 is approximately 1.3 times greater than the through section of the dividing aperture 11; in other preferred embodiments, the ratio between the outlet section D1 of the upstream nozzle 4 and the through section D2 (Figure 2) of the dividing aperture 11 can vary from 1.2 times to 1.4 times.
[0030] The sprayers described hereinbefore are susceptible to numerous modifications and variations without departing from the scope of the present invention: for example, the propeller 13 can be replace with other types of rotors or revolving bodies made to rotate by the jet of liquid which hits them, or by other types of appropriate circular spraying means, suitable to spray with the sprayed liquid and with a predetermined degree of uniformity, a circular or rounded internal spraying zone; the deflector 5 can be replaced by other peripheral spraying means suitable to spray with water or another sprayed liquid an external spraying zone located around and at least partly external to the aforesaid internal spraying zone; or the deflector 5 can also be hit by several inlet jets, also coming from a plurality of upstream nozzles; the deflector 5 can also be devoid of projecting parts 10, but be suitable to divert and direct the fraction of fluid which flows on the external surface of a conical projection 6 towards one or more spraying areas, on a surface to be sprayed, external to a circular or rounded internal spraying area, in any case giving rise to square, triangular, polygonal or star-shaped sprayed areas. The dividing crest 14 and the upstream nozzle 4 can be replaced by other flow dividing means, suitable to divide the flow of liquid to be sprayed which enters the sprayer in a first and a second fraction, the first fraction sent towards the circular spraying means, the second fraction sent towards the deflector 5.
1. Sprayer suitable to spray a predetermined area with a sprayed liquid, said sprayer
comprising:
the peripheral spraying means (5, 6, 9, 10) comprise a deflector (5) suitable to be hit by one or more jets of liquid to be sprayed and to divert and direct at least part of this jet or these jets towards at least part of the external spraying zone so that said at least part of the external spraying zone substantially forms a projection of the internal spraying zone.
- circular spraying means (12, 13) suitable to spray, with the sprayed liquid and with a predetermined degree of uniformity, an internal spraying zone (L1) with a substantially circular or rounded shape;
- peripheral spraying means (5, 6, 9, 10) suitable to spray with the sprayed liquid an external spraying zone located around and at least partly externally the internal spraying zone (L1), characterized in that
the peripheral spraying means (5, 6, 9, 10) comprise a deflector (5) suitable to be hit by one or more jets of liquid to be sprayed and to divert and direct at least part of this jet or these jets towards at least part of the external spraying zone so that said at least part of the external spraying zone substantially forms a projection of the internal spraying zone.
2. Sprayer as claimed in claim 1, characterized in that it comprises first flow dividing means (11, 14) suitable to divide the flow of liquid
to be sprayed entering said sprayer (1) into at least a first and a second fraction,
where at least the first fraction is sent to the circular spraying means (12, 13)
and at least the second fraction of the liquid to be sprayed is sent towards the deflector
(5) to be sprayed on the at least one external spraying zone (ZE).
3. Sprayer as claimed in claim 2, characterized in that the first dividing means (11, 14) comprise
- at least one dividing crest (14) provided on the deflector and
- at least one upstream nozzle (4) suitable to emit an inlet jet, of liquid to be sprayed, against the at least one dividing crest (14) in order to divide the inlet jet at least into said first and second fraction.
4. Sprayer as claimed in claim 2 or 3, characterized in that the first dividing means (11) comprise
- a dividing aperture (11, 14) provided on the deflector (5) and
- at least one upstream nozzle (4) suitable to emit an inlet jet of liquid to be sprayed against the dividing aperture (11) so that said first fraction of liquid to be sprayed enters therein, but the second fraction does not.
5. Sprayer as claimed in claim 4, characterized in that the at least one upstream nozzle (4) and the dividing aperture (11) are substantially
opposite and the outlet cross section of the at least one upstream nozzle (4) is substantially
approximately 1.2 to approximately 1.4 times greater than the cross section of the
dividing aperture (11).
6. Sprayer (1) as claimed in claim 3 and/or 4, characterized in that the deflector (5) comprises a projecting part (6) which extends in the direction
of incidence of the inlet jet, where said dividing aperture (11) and/or said dividing
crest (14) are disposed on the top or near the top of the projecting part (6).
7. Sprayer as claimed in one or more of claims 2 to 6, characterized in that the deflector (5) comprises, downstream of the first dividing means (11, 14), at
least a base extension (10) which extends transverse to the direction of incidence
of the upstream jet and is suitable to divert at least part of said second fraction
of liquid to be sprayed in order to project it transverse to the direction of the
upstream jet and towards at least one of said external spraying zones (ZE) located
around and at least partly outside the internal spraying zone (L1).
8. Sprayer as claimed in one or more of claims 2 to 7, characterized in that the deflector (5) comprises a flange (7) located at and around the base of the projecting
part (6), said flange (7) being suitable to divert at least part of the upstream jet
in order to release it transverse to the direction of incidence of said upstream jet
against the deflector (5), and towards at least part of the external spraying zone
(ZE) located around and at least partly external to the internal spraying zone.
9. Sprayer as claimed in claim 8, characterized in that the perimeter of the plane of the flange (7) has a substantially square or rectangular
shape.
10. Sprayer as claimed in one or more of claims 7 to 9, characterized in that at least in proximity of and/or at the base of the projecting part (6) the deflector
(5) comprises second dividing means (8. 9) suitable to promote diversion, towards
at least one of the base extensions (10), of the second fraction of liquid to be sprayed.
11. Sprayer as claimed in one or more of claims 1 to 10, characterized in that the circular spraying means (12, 13) comprise a rotor (13) suitable to be made to
rotate by a jet of liquid to be sprayed which hits it and by rotating is suitable
to sprinkle the liquid to be sprayed.
12. Sprayer as claimed in claim 11, characterized in that the deflector (5) comprises a guide duct (12) located downstream of the dividing
aperture (11) and suitable to contain and guide the first fraction of liquid to be
sprayed against the rotor (13), in order to increase the output of the propeller (13).