CA1120852A

CA1120852A - Apparatus for cooling cooling water

Info

Publication number: CA1120852A
Application number: CA000333224A
Authority: CA
Inventors: Gunter Ernst; Edmund Baer; Dieter Wurz
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-08-04
Filing date: 1979-08-03
Publication date: 1982-03-30
Also published as: DE2930567C2; DE2930567A1; NL7906013A; AU528938B2; BR7905006A; FR2439377B2; ES253365Y; JPS5531297A; CH639189A5; IT1119118B; IT7968612A0; FR2439377A2; BE878058R; AU4958379A; GR69602B; GB2029561A; ES253365U

Abstract

ABSTRACT
There is provided apparatus for cooling cooling water, in which means for trickling water over extended surfaces is provided, the water being in direct contact with coolant air, to achieve wet-cooling as well as indirect transfer of heat through the provision of dry transfer sur-faces contacted by the coolant air. A set of spaced parallel trickler plates are provided, defining ducts for the flow and coolant air, and water trickles down the plates. The water wets one face of each trickler plate and leaves dry a substantial part of the opposite face. Thus wet-cooling takes place on one side of a plate, and dry cooling on the other. The ratio of the height of the trickler plate to the inter-plate spacing is not greater than about 50:1.

Description

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Apparatus for cooling cooling water, especially in cooling towers.

The present invention re1ates to apparatus for cooling cooling water, particularly in a cooling tower which comprises means for causing the water to be cooled partly by trickling over extended surfaces in direct contact with the flow of coolant air, for so-called wet cooling by direct heat transfer to the coolant air and evaporation, and partly by indirect transfer of heat to the coolant air via heat-exchange means having dry heat transfer surfaces directly contacted by the coolant air , for so-called dry cooling of the water.

In conventional wet cooling towers whic ~se trickler plates, the trickler plates are normally orientated with their widths in the vertical direction and cooling water is sprayed o~both faces of the plates and then trickles down.The water is exposed to the coolant air flowing past, usually in the upward direction, on both sides of each trickler plate and is thereby cooled. Because of the direct contact of the~water with the air on both sides of the trickler plates a considerable portion of the cooling water evaporates and is discharged from the cooling tower in the form of vapour cl~ouds. Apart from the loss of water thi~s has undesirable ecological influences. ~ ~

Dry~cooling~towers are known ln which the;cool~lng water is not~directly contacted~;wlth thé coolant~ ai~r, but instead is passed through finned heat~exchange tubes~or the like;exposed to the air. Such~finned tubes are expensi~ve~.~Besides, the cooling performance is much poorer than with wet coo~llng towers~because no~evaporation of water takes place.

An~apparatus lS known which combines the~ advantages of wet- and dry cooling by spraying~the cooling wate~ only on the one faces of trickler plates which~are designed similarly~as the~trickler plates of wet cooling towers (DE-AS 25 32 544, 25 37 887).
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t3S2 With the known apparatus a considerably smaller water surface is exposed directly to the coolant air and consequentlysu~ected to wet cooling. The air flowing along the dry face of each trickler plate effects cooling by heattransfer through the plate generally in the same way as with the dry cooling process.
undesired This reduces on the one hand the generation of vapour clouds and/ecological influ-ences resulting therefrom, whereas on the other hand the expensive finned tubes as used with conventional dry cooling apparatus are replaced by trickler plates as used in conventional wet cooling towers wîth only minor alterations in shape.

It is an as2ect of the present invention to improve an apparatus of the type mentioned with respect to the combined wet - dry-cooling effect.
i According to the present invention an apparatus of the type mentioned comprises at least one set of space~parallel trickler plate~which define/~etbr opposed faces ducts for the passage of flows of coolant air, and means for causing the water to trickle down the trickler plates to be cooled by the air flows. the apparatus being so constructed and arranged that the descending water wets and trickles down one face of each operative trickler plate of the set and leaves dry the whole or a substantial part of~the area of the opposite face of the plate, thereby the water trickling down the "wet" face of the plate is directly cooled by contact with the cooled air flow on that side of the plate and is also cooled by heat transfer through the plate thickness to the coolant air flow in contact with the dry portion of the i'dry" face, each of said ducts being bounded on one of its sides by the "wet" face of the trickler plate and on its opposite side by the oppositely facing "dry" face of an adjacent plate, and the ratio of the height of the trickler plate to the spacing between adjacent trickler plates being no greater than about 50:1.

Whereas in the known apparatus (DE-AS 25 37 887) alternately dry and wet ducts are formed the oppositely-facing walls of which are both wet or dry, l~Z~)B~Z

each duct of the invention comprises a wet and an oppositely-facing dry face. This contributes to an intense mixing of dry and wet air in the upper portion of each duct such that without an add;tional device, like a fan, an intense mixing of the dry and wet air portions is achieved.
the generation of vapour clouds is thereby held on a minimum and nearly as small as with the mere dry cooling.

The claimed limited ratio of the height of each trickler plate to the distance of the adjacent trickler plate contributes as well to this effect.
If the trickler plates had a too large height as compared with the distance the air could wet as well the dry side of each duct before reaching the outlet of the duct by droplets which are t2ken with the air from the wet side . This would lead to a wet cooling effect at least in the region of the outlet of the duct and would therefore deteriorate the desired effect.
, Preferably the said ratio between the height dimension pf each trickler plate to the distance of the adjacent trickler plate is not greater than 20:1.
, Thesaid ratio, should, however, not be chosen too small in order not to diminish the heat - exchange path in the ducts on a value too small. An appropriate lower limit of the said ratio is 10:1.
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If the upper section of each trickler plate is inclined to the vertical lower portion (DE-AS 25 32 544, 25 37 887), it-may be provided accordin~a further feature;of the invention that the;~projection of the upper portion on a hor120ntal plane covers at least 20X of the distance and at most llOX of the distance to the~adjacent trickler plate. Using conventional spraying devices which;spray the water vertically downwardly, it is surprising that in this contaxt~an arrangement works in the sense of the invention in which said projection does not bridge the distance to the adjacent trickler plate completely but leaves a gap of at most 80% of the said distance open. It would be expected with such an arrangement that the water would simply fall through the gap between the trickler plates without any cooling effect.
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~However, according to the outfindings of the inventors this does not happen.
Instead the downwardly falling water droplets are deviated by the uprising air in such a manner that the droplets contact the wet faces of the trickler plates.

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Preferably the angle of inclination of the upper section of each trickler plate to the vertical is not greater than 45. In practical embodiments the said angle of inclination is situated between 15 and 20.

According to a further advantageous aspect of the invention it i provided that each trickler plate has at its upper end a lip bent to its dry side.
This lip is particularly advantageous in case if the said projection of the upper inclined portion of the trickler plate covers only part of the distance to the adjacent trickler plate.

The said lip catches spray-water which may be sprayed from the oppositely facing wet side on the dry side.

The invention may be carried in practice in various ways, but several specificembodiments will now be described by way of example and with reference to the accompanying diagramatic drawings, in which :

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Figure 1 is a diagrammatic elevation of a conventional natural draught cooling tower with an apparatus embodying the invention installed in the same;
5. Figure 2 shows side-by-side and very diagrammatically two different forms of apparatus embodying the invention;
Figure 3.is a top plan view of a modified form of the apparatus embodying the invention;
: ~o, Figure 4 is a top plan view of an apparatus embodying the invention, principally as shown in Figure 2;
Figure 5 is a sectional view along line V-V.. in f Figure 4 to ~an enIarged scale;' - :
15. Figure 6 is an elevational view as seen in the direction of arrow ~I in Figure 5~;
Figure 7 is a perspective ~iew of another form of the:apparatus embodying the invention;~
: . ~igures 8,:~9~and 1~0~show further modified 20. apparatus embodying the invention with~variable~wet coollng~and ~ ~cooling~proportions;
Figures:11a:~to d show ~our~variants:o~;a spray :device in apparatus~embodying the~inve~ntion;
Fi~gures 12a~nd~b show two~variants of the Z5~ spray device and the trickler units designed aocording ;:to the inventi~on;
' Pigures 13a and b,show two further,variants of the spray device ihn apparatus~embodying the invention;and Figure 14/a~preferred trickler plate design of trickler ~ 30~ plates according to the invention, of which at least details B~ are appliable~in the embodiment ~ shortly described above~
. ~ Figure 1 sbows a natu~al draught cooling tower 1 : of conventional exterior appearance~ A collecting ,, ~

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tank 2 for cooled water is arranged on the foundation of cooling tower 1. Supports 3 carrying the cooling tower wall 4 rest on the bottom of collecting tank 2. Inside the cooling tower 5. wall there are provided a drop separator 5, a cooling water distributor 6, and trickler m~tS
generally designated 7. Cooling water which comes, for instance, from a thermal power station and is to be cooled, is introduced into the 10. distributor 6 through a duct 8. The water to be cooled falls down from the trickler units 7 into the collecting tank 2 and, whlle passi~g the trickler units, it is cooled by ambient air penetrating between the supports 3 and ~lowing in 1~. the direction of arrows A. On its way the ambient air heats up so that it adopts a lower density insi4e the cooling ~ower than outside of the same . and therefore ascends. The~air~which~i~s enriched withtevaporated;water~i;s dlscharged from the;~opening 20. ;~at~the crown of oooling tower 1. The cooled wzter is~returned through ~a duct 9 to the thermal power stati~on or the~-like.
Thé trickler~units comprise epaced parallel trickler plates 10 and~ spaced parallel alignmen* pla*es 11 25.~ arranged in parallel above the same, the plates 10 and 11 being orientated with their longitudinal dlrection~in the~horizontal sense and with their widths approximately vertical. The water is sprayed on the alignment plates by the distributor 6 30.~ through nozzles, spray apertures 12 or the like, as ~ .

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may be seen in detail in Fi~ure 2. The alignment plates 11 function to deflect the water issuing in various directions from the spray apertures so that it will fall down vertic~lly from their 5, lower ends and impinge on the upper faces only o~ the upper inclined sections 13 of the trickler plates which are arranged offset below the alignment plates. As a result of this arrangement only one surface of each operative trickler plate, 10, in Figure 2 the right-hand side, is wetted by the wa~er to be cooled, whereas the surface on the ` left hand side as seen in Figure 2 remains dry.
Thus on the right sides of trickler plates 10 the ambient air whioh flows~from below to the top 15. along the trickler~plates is in con~act with the water to be cooled, which trickles down that face only of each plate 10, whereas on the left sides the air contacts the dry~surfaces of the trickler plates~10. The~water~surface di~rectly~exposed 20.~ to the ambient air~thus~is~only~half of~that~exposed in the case of~a~structure with which both sides of;the~triGkler~plates~are~wetted. Consequently the amo::~ of water evaporated~is reduced accordingly so that;the moisture~content~in the vapoUr~cloud 25~ `and~the undesired~ecological influent are reduced.
The only difference between the two variants shown side by side~in ~igure 2 resides in the fact that with the embodiment shown on the left half of the Figure~the alignment;plates also have 30.~; ~inclined upper~ sections~14. This will produce a , ~ . .

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certain combined wet and dry cooling effect also with these plates, although it cannot be prevented with this arrangement that the left surfaces of the alignment plates, as seen in F~igure 5. 2, likewise becomes wetted to a certain extent.
In the embodiment shown on the right-hand half in Figure 2 the alignment plates are completely plane and ~ertically oriented so that cooling water which is discharged through spray apertures 10. 12 wets both sides of the alignment plates 11 equally. However, the lateral offsetting of trickleF plates 10 with respect to the~alignment plates 11 (realized also wqth the left-hand alternative) makes sure that also with the rlght-hand alternative the water drops~only on the right faces of the trickler plates so that their left faces, as seen in Figure 2, remain dry.
Plates 10, 11;may~be made from thin~sheet metal or~plastics so~that a~light-weight, inexpensive 20.~ struoture can~be~realized~.~ The~only additional finish~ing step~as~comparéd~to conventional ver~ical trickler~plates~resides in the~formation of the inclined uppér~sections 1~3 of the trickler plates, and when applicable~the~upper sections 1~4 of the

2~ àlignment plates.
~ Figure 3 is~a top plan ~iew of an alternative embodiment~ with~alignment plates 11 and~trickler plates~10 ln crosswise~arrangement.
Figure~s 4, 5,~and 6 show a structural embodiment 30-~ of the arrangemen~principle shown in the right , ~ .
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g half of Figure 2, in which the alignment plates 11 and the trickler plates 10 are arranged in parallel. Figure 4 is a diagrammatic top plan view of the trickler plates 10 alone which are supported 5. or suspended by ~heir la~eral ends 15 on beams 16 of a support structure. The trickler plates 10 which are made of sheet metal are kept at mutual spacings by combs 17 which at the same time serve to support the alignment plates 11 arranged 10. above the same but not sho~m in Figure 4.
This will become apparent from Figures 5 and 6.
The views of ~igures:5 and 6 are to a larger scale and more detailed than Figure 4.
Each of the trickler plates 10 is subdi~ided 15. into a lower vertically-oriented section 18 and an upper inclined section 19 bent with respect to the lower section along the edge 20. At its lateral ~ ends each trickler plate 1~0 is provided with a ::~ pro~ection 21 extending~across sections 18, 19 20.~ ~and having a lower~:horizontal: support surface 22 by~;means of which the~trickler plates are:supported :on~beams 1~6.~Above She~:tri~ckler plates the alignment plàtes:11 are arranged offset in such :manner that their:lower ends~lie above the central 25~ regions of the inclined upper sections 19 of trickler plates:10 as shown; ~n the same manner as the :trickler plates,also the alignment plates:are kept spaced apart by the combs 17 which may be made:
f~om plas~ics. These combs 1:7 are pro~ided along 30. their upper edges -Yith~vertical recesses 23 at the ~. .

llZV852 desired spacings to receive alignment plates 11 and along their loweredges with correspondingly inclined recesses 24 to receive the upper inclined ends of trickler plates 10. The recesses, 5, 23, 24 are offset in the combs in accordance with the desired lateral offsetting of trickler plates 10 with respect to alignment plates 11.
Figures 5 and 6 show an example of the arrangement of the trickler plates. The trickler plate shown 10. at the far right side in Figure 6 is provided with bulges 29 on its left "wet" side. The arrangement of these bulges may be gathered ~rom Figure 5. These bulges 29 serve to diminish~the wet surface because the water flowing down in the recesses between the ; 15. bulges 29 leaves these bulges partly dry. This serves to further reduce the proportion of water evaporated.
Figure 7 shows trickler plates 30 which are of ~undamentally~different design from those shDwn in ; ~ 20.~ Figures 5 and 6. These trickler plates 30 are arranged inclined over their~entire height and have~p~rojectlng~dripping~noses 31 in their upper halves.
Se:veral~such~dripping noses 31 are provided spaced horizontally and àre interconnected by a drop guide 25. means in the form of a bend line 32. This bend line 32 has its highest position between the dripping noses and its~lowest at the dripping noses 31, The~dripping noses 31 are slightly downwardly inclined.
It is obvious that water which may possibly be 30- sprayed on the upper section 33 of the right-hand llZV8~2 surface, as seen in ~igure 7, o~ any plate 30 will coll,ect at the dripping noses 31 and fall down onto the lower section 34 o~ the left surface of the next adjacent plate 30 to the right.
5, The lower sections 35 of the right surfaces which msy be, longer than the upper sections 33 by any desired extent consequently remain completely dry. Therefore the embodiment according to Figure 7 may completely dispense with ~lignment 10. plates such as used with the preceding embodiments.
The inclined trickler plates 30 may be so arranged that they support eaqh other laterally by means of their dripping nos;es.
The embodimen* according to Figure 7 also comprises 15. combs 37 for proper mutual arrangement-of rows of trickler plates 30 arranged above one another.
Figures 8, 9 and 10 show variant embodiments , with which the relationship between wet cooling and dry cooling can be varied.
20. In the case,of the~embodiment shown in Figure 8 aliO~nment plates 11 and~trickler plates 40 , ;are~arranged~in~common~vertical planes. ~The tr~ickler pla~es~40 are~pivotable through an angle a;~-from the position of vertical alignment with the 25.~ alignment plates~lnto an inclined position. The pivoting movement is effected about a fulcrum 41 which lies below the u~per end of each trickler plate 40. ~ -In their extreme pi wted position (angle a) the 30- upper ends of trickler~plates 40 are offse* with . , .
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respect to the lower ends of alignment plates 11. In this case only the left faces of trickler plates 40,' 2S seen in Figure 8, are wetted so that a combined wet cooling and dry cooling effect . is obtained. If, on the other hand, the trickler plates are in vertical position, both sides are wetted so that a pure wet cooling effect is obtained.
In the embodiments of Figures 9 and 10, trickler plates 50 of identical design are used which 10. are similar to those of the embodiment shown in ~igures 4 to 6 each having an inclined upper section ' 51 the upper end 52 of which, however, is vertically orien~ed. In the case of the embodiment accordi~g to Fi~ure 9 the vertical alignment plates 11 ' 15. arranged above~the trickler~plates 50 are designed ~or joint parallel displacement.~ If the alignment plates are located in the positions shown in broken lines directly above~the~upper~ends 52~of the t.rickler plates~50,~both~6ides~of the trickler~
zo~ plates will become~wetted.;~ However, if~the~alignment plates are displaced~'in paral-lel toward~the left into~-~the position~shown~in'~continuous lines, only the~le~t ~side~of'~the~trickler~-plates~50,~as seen in~Figure~9~, wiil~De~wetted.~ Again in~the f rst . ~case the cooling;effect will be purely wet cooling, whereas in the second case a combined wet cooling and~dry cooling~effect is obtained. The consequences are~the same lf the~trickler~plates 50 are arranged for parallel displacèment instead of the alignment 30.~ lates 11.

, 1~2V8 The trickler plates 50 shown in Figure 10 have the same design as in the embodime~t shol~n in Figure 9. In this case, however, the alignment ~lates 53 which are located above the upper ends 52 5, of the trickler plates 50 are pivotable from their vertical positions in the direction shown by an angle ~in the anti-clockwise sense, i.e. in a direction toward the left surfaces such that their lower edges will then lie above the inclined positions 51 10. Of the trickler plates 50. In this manner the same effect can be obtained as with the parallel displacemen~ according to Figure 9.
Figures 11 to 13 show di~erent embodimen~
of the spray devices.
15. In Figures 11a to 11d the elongate spray devices are shown abo~e the alignment or trickler plates 62 which are arranged with their widths in vertical direction.Inallof these embodiments ~he spray device~s are~arranged above the alignment 20. ~ or trickler plates~, respectively, and their ongitudinal axes~are horizontA~ and parallel to the alignment or trickler plates. In the case of ;the embodiment shown in Figures 11a and 11b the spray devices ~qm~rise distributor channels 60 with 25. mouthpieces ~ e~3channels 60 being disposed at equal spacings and extending perpendicularly with respect to the plane of the drawing. In the case of Figure 11a the mouthpieces 6~ and ~hus the spraying ~; ~ plane V are inclined by an angle wi~h respect to 30, the vertical. The result thus obtained is the " .

zv~z wetting only ol the right sides, as seen in thedrawing, of the trickler plates or alignment plates 62. An inclination in the upper sections of the plates is not necessary.
5. In the case of ~igure 11b the mouthpieces 63 of the distributor channels 60 are vertically oriented. Below the mouthpieces 63 o~ each channel, however, a water jet deflector 64 is provided in the form of a sheet metal profile 10. having an L-shaped or equivalent cross section.
The deflector serves to deflect the liquid jets issuing from the mouthpieces by an even greater -angle c~ so as to obtain a spraying plane V which is even more inclined with respect to the vertical.
15. ~ Wlth the embodiment shown in Figure 11c a distributor tube 65 is provided which has mouthpieces 66 inclined at an angleC~ relative to the ve~tiçal.
In Figure 11d, on the other hand, the mouthpieces ~67 of a distributor~tube 65areorientatedvertic lly 20. downward~and g~uide their jets onto an~inclined~
deflecting profile~68, ~he~ ef~ect and configuration of;which correspond to those of the water jets deflecting profile 64. ~
Figures 12a and~12b and 1~3a and 13b show examples 25.~of how to vary the~wet oool1ng and dry cooling proportlon. In these embodiments such a variation is obtained by pivoting the spraying plane. In the case of Figures 1~2a and~13a the spray devices comprise distributor tubes 65 with mouthpieces 30.~ 66 attached to the same and inclined at an angle .

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with respec~ to the vertical, as is the case in Figure 11c. The angle of inclination ~ of the spraying plane V may be changed to an angleo~/of a new spraying plane V' merely by lowering the cooling 5. water inlet pressure.
In the case of the embodiments shown in Figures 12b and 13b the distributor tubes 65 having mouthpieces 66 are each mechanically pivoted about a horizontal`.axis which coincides with the axis A of the distributor tu~e, so as to obtain a dif erent angle of inclination of the spraying plane. :
With the embodiments according to Figures 12a and ?2b trickler plates 10 are used which have 15. upper inclined sections such as are shown, for instance, in Figures 2 to 6. In these cases consequently the spray devices as well as the trickler plates are of a desi~n which promotes the~one-sided wetting of the trickler plates 10.
20. : A~simpler plate arranBement is shown in Figure 13 in which either the:trickler plates themselves ;; or~the:alignment plates 62 are vertically oriented along their entire~widths.

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'112()1~32 Fig. 14 shows a preferred embodiment of the trickIer plates as it may be used in the arrangements according to figs. 1 to 6 and 12a, 12b. Details of the trickler plate design as shown in fig. 14 may advantageously as S well be used in the remaining embodiments.
According to fig. 14 which shows only two trickler plates of a set of trickler plates each trickler plate comprises an elongated lower section 70 and an upper section 72 inclined to the vertical at an angle ~ .
Angle d should not be greater than 45 and preferably is arranged between 12 and 20. In the embodiment as shown the angle ~ is 16,5. The ratio of the helght h of the trickler plates to the horizontal distance or spac-ing d therebetween is not greater than about 50:1 and preferably not greater than about 20:1 and not less than 10:1.
In the embodiment as shown the ratio h/d is about 20:1.
The spacing e on a horizontal plane represents the "overhang" of the inclined upper section 72 of each trickler plate and covers at least 20% and at mos,t 110%
of the distance d between adjacent trickler plates.
In the embodiment shown the spacing e of the inclined section 72 covers about 75~ of the distance d.
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Keeping in mind~that no droplets of water should fall~through the gap d-e between~ad,;a-c nt trickler plates but,all~the water should come in con~act with the wet side o~the~ trickler plates (the left side of each trickler pl~ate in~fig. 14), it is surprising that, according to the observations of the inventors, the inclined portion of adjacent trickler plates need not fully overlap or cover the spacing d but may leave a gap d-e of up to 80~

r, ~ i 1iZ~8S2 of the spacing d uncovered. The inventors found out that even with such an extremely large gap d-e all water droplets will come into contact with the wet side of the trickler plates. This phenomenon may be explained by the flow effects 5. of the uprising air streams which will deflect the falling water droplets out of their vertical path onto the wet sides of the trickler plates ~the left faces in fig. 14).

Prefervably the upper ends of the upper portions 72 of the 0- trick'ler plates may be bent downwardly to form lips 74 extending to the wet sides of the adjacent trickler plates.
These lips 74 ensure that water spr ayed upon the bent - upper~ portions 72 is not sprayed~as well to the~oppositely-facing dry sides~of~the trickler~plates but is captured 5- by the lips 74~so~that the~ dry sides (the right-hand sides of,the trickler~plates in fig. 1;4) are~prevented from being ; wetted by sprayLng~water.~ ~his'spraying water drops vertically down from the Lips~74 and is~deflected by the ,~ uprioi~ air stream~to the wet sldes of the trlckler plates.

pp#~ the trickler~plates~as shown~1n~fig.~14 and h ~ as~described abo~ve~ may~be used~ unchanged~ 1n~the~arrange-ments,~according~to~fig.~1~to 6 ~and~fig.~12a,~12b. P'refer~ab}y ~ the~above~de w r'ibed~ratios"~h:d~and/or the~above~described ,"';~ 25~ ips~`7~4~may as~well~be~applied~in the embodiments according to,~fLgs~ 7~to-~10~and~11a~to 11d as well~as in figs. 13a and It~is~within ~the~scope of the invention`to provide a plurality 30~ of~sets of trickler plates in a defined vertical arrangement.
In~ th1s~case only the~;uppermoot set or sets of th`e trickler plates are des1gned for~a comblned wet-dry cooling as deocrlbed.
; In practical embodiments for use in natural - draught cooling towers~the~trickler plates may have heights h varying between 200 and 2000 mm.

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Claims

CLAIMS:

1. Apparatus for cooling cooling water, particularly in a cooling tower, which comprises means for causing the water to be cooled partly by trickling over extended surfaces in direct contact with the flow of coolant air, for so-called wet-cooling by direct heat transfer to the coolant air and evaporation, and partly by in-direct transfer of heat to the coolant air via heat exchange means having dry transfer surfaces directly contacted by the coolant air, for so-called dry cooling of the water, which comprises at least one set of spaced parallel trickler plates which define between their opposed faces ducts for the passage of flows of coolant air and means for causing the water to trickle down the trickler plates to be cooled by the air flows, the apparatus being so constructed and arranged that the descending water wets and trickles down one face of each operative trickler plate of the set and leaves dry the whole or a substantial part of the area of the opposite face of the plate, thereby the water trickling down the "wet" face of the plate is directly cooled by contact with the cooled air flow on that side of the plate and is also cooled by heat transfer through the plate thickness to the coolant air flow in contact with the dry portion of the "dry" face, each of the said ducts being bounded on one of its sides by the "wet" face of the trickler plate and on its opposite side by the oppositely facing "dry"
face of an adjacent plate, and the ratio of the height of the trickler plate to the spacing between adjacent trickler plates being no greater than about 50:1.

2. Apparatus as claimed in claim 1 in which the said ratio is not greater than 20:1.

3. Apparatus as claimed in claim 1 in which the said ratio is not less than 10:1.

4. Apparatus as claimed in claim 1, claim 2 or claim 3, in which the upper section is inclined to the vertical lower section and the projection of the upper section on a horizontal plane covers at least 20% of the horizontal spacing of the vertical section between the two adjacent trickler plates.

5. Apparatus as claimed in claim 1, claim 2 or claim 3, in which the upper section is inclined to the vertical lower section and the projection of the upper section on a horizontal plane covers at least 20% and at most 110% of the horizontal spacing of the vertical section between the two adjacent trickler plates.

6. Apparatus as claimed in claim 1, claim 2 or claim 3, in which the upper section is inclined to the vertical lower section and the projection of the upper section on a horizontal plane covers at least 20% of the horizontal spacing of the vertical section between the two adjacent trickler plates, and in which the angle of inclination of the upper section of each trickler plate to the vertical is not greater than 45°.

7. Apparatus as claimed in claim 1, claim 2 or claim 3, in which the upper section is inclined to the vertical lower section and the projection of the upper section on a horizontal plane covers at least 20% of the horizontal spacing of the vertical section between the two adjacent trickler plates, and in which the angle of inclination of the upper section of each trickler plate lies between 15° and 20°.

8. Apparatus as claimed in claim 1, claim 2 or claim 3, in which each trickler plate has at the upper end of the upper section a lip bent downwardly to its "dry" face.

9. Apparatus as claimed in claim 1, claim 2 or claim 3 in which a plurality of sets of trickler plates is provided in a defined vertical arrangement and in which only the uppermost set or sets of trickler plates are designed-for-combined-wet-dry-cooling.

10. Apparatus as claimed in claim 1, claim 2 or claim 3, in which the horizontal distance between adjacent trickler plates is substantially constant over substantially the entire height of the trickler plates and the ducts formed between adjacent trickler plates being free of sharp deflections.