Hybrid dry-wet cooling tower

Abstract

The invention is a hybrid dry-wet cooling tower for a hybrid cooling system, the cooling tower comprising a tower shell (10) having a lower edge (11) and an upper edge (12), and a leg arrangement of tower shell legs (13) supporting the tower shell (10) above a ground level, the leg arrangement providing an air intake between the ground level and the lower edge (11) of the tower shell (10). The cooling tower further comprises: - a natural draft dry cooled segment (20) being arranged outside and around said leg arrangement and being supported by support legs (21) above the ground level; - a top covering (23) for closing a circular gap between a top periphery of the dry cooled segment (20) and the lower edge (11) of the tower shell (10), - a wet cooled segment (30) arranged inside of said leg arrangement and having wet cooling cells (31) arranged with a spacing from the leg arrangement; and - a separating cover (40) being a boundary of an air duct space (41) between the air intake and the wet cooling.

Description

[0001] HYBRID DRY-WET COOLING TOWER

[0002] TECHNICAL FIELD

[0003] The invention relates to a hybrid dry-wet cooling tower, preferably for medium to large duties of power plant cooling, which provides significant water savings together with significant reduction of electrical power consumption.

[0004] BACKGROUND ART

[0005] A number of hybrid dry-wet cooling tower solutions have been disclosed in the prior art. The term hybrid in this context means that both dry and wet types of cooling are present. WO 2016 / 174482 A1 discloses a hybrid cooling tower including a tower shell, a wet cooled segment (in other words: wet cooling section) arranged inside the tower shell, and a dry cooled segment (in other words: dry cooling section) arranged outside the tower shell. The wet cooled segment includes wet cooling cells arranged at a distance from the tower shell with fans arranged thereon for inducing upwards humid air exhaust flow. The dry cooled segment is disposed generally above the air intakes for the wet cells and includes air coolers arranged as vertical cooling deltas around the tower shell. The cooling deltas are equipped with louvers for controlling a cooling air inlet. The cooling tower further includes dry fans arranged in at least some of the inlet openings of the tower shell for inducing mechanical draft for the dry cooled segment. This known cooling tower combines both wet and dry cooling methods to efficiently manage temperature, making it versatile for various environmental conditions. The known design features separate segments for wet and dry cooling, allowing for better control of airflow and cooling performance. By using fans and adjustable louvers, the system can optimize cooling based on realtime needs, improving energy efficiency and reducing operational costs.

[0006] A major drawback of the above prior art hybrid cooling tower is that inducing mechanical draft for the dry and wet cooled segments substantially increases electrical power consumption, generates unwanted noise and increases maintenance costs due to the large number of rotating equipment involved in air moving. Another general disadvantage of the prior art hybrid towers is that their arrangement does not support flexible operation primarily or exclusively based on natural draft.

[0007] Apart from WO 2016 / 174482 A1 , in the field of hybrid dry-wet cooling for power plant or industrial applications the prior art also discloses mechanical draft wet cooling cells supplemented by dry air coolers in a common structure with the primary aim to reduce humidity of exhaust air, i.e. to abate plume. These solutions exclusively use fans for inducing air flow through both the wet and dry cooling sections, contributing to significant electrical power consumption, while the water savings realised by the partial use of dry air coolers in the cooling circuit is not significant, it is generally around max. 10%.

[0008] Due to various economic considerations, and perceived constraints of technical characteristics of cooling towers for wet cooling and of cooling towers for dry cooling, tall natural draft cooling towers with dry cooling sections with the aim of water saving were never considered in the prior art in combination and for inducing natural draft air flow through wet cooling cells located internally at a ground level, in order to create a hybrid dry-wet tower with significantly reduced electrical power consumption, noise and maintenance cost.

[0009] DISCLOSURE OF THE INVENTION

[0010] It is an object of the invention to provide a hybrid dry-wet cooling tower which is free of disadvantages of prior art solutions to the greatest possible extent.

[0011] It is a further object of the invention to provide a hybrid dry-wet cooling tower for medium to large duties of power plant cooling, which is characterized by significant water savings together with significant reduction of electrical power consumption, noise, and maintenance costs, with respect to the prior art. The objects of the invention have been achieved by means of the hybrid dry-wet cooling tower according to claim 1 . Preferred embodiments of the invention are defined in the dependent claims.

[0012] The inventive hybrid dry-wet cooling tower enables to establish a dominant dry cooling section that provides the major part of the cooling duty, allowing significant water savings, e.g. 10 to 80 % water use of a wet cooling tower for the same cooling duty, however, also allowing full dry or full wet operation. The inventive hybrid drywet cooling tower also enables a flexible adjustment of the total heat dissipation and its distribution between the wet and dry cooling sections, depending on the given configuration, actual cooling duty and ambient conditions, by specific thermo- hydraulic sizing, including determining the proportions of cooling water flows to the wet and dry cooling sections, selection of the type and size of equipment and heat exchangers of the wet and dry cooling sections, and calculating the rates of air flow for each section.

[0013] The inventive hybrid dry-wet cooling tower preferably uses a tall (preferably min. 100 m and taller, without upper limit) tower shell of sufficient diameter, i.e. a natural draft cooling tower structure, to induce air draft via the dry air coolers of the dry cooling section, thus fully eliminating the electrical power requirement of dry cooling section air moving. The dry cooling section and the wet cooling section are arranged in the same common tall natural draft cooling tower structure.

[0014] With respect to WO2016174482A1 , the invention has the following inventive characteristics to reduce electrical power consumption, noise and maintenance costs:

[0015] - the invention establishes a dominant dry cooling section;

[0016] - fully eliminates electrical power consumption and reduces noise and maintenance cost of the air moving of the dominant dry cooling section by utilizing the natural draft of a tall (preferably min. 100 m and taller, without upper limit) cooling tower;

[0017] - arranges the wet cooling section and the dry cooling section in the same natural draft cooling tower, allowing either full elimination of the electrical power consumption and reduction of noise and maintenance cost of the air moving of the wet cooling section as well in some embodiments, or resulting in significant reduction of the same in other embodiments.

[0018] It must be also noted, that the invention retains all the advantages related to dimensioning and operational flexibility of the technical solution disclosed in WO 2016 / 174482 A1.

[0019] BRIEF DESCIPTION OF THE DRAWINGS

[0020] Preferred embodiments of the invention will be described by way of example with the accompanying drawings, in which

[0021] Fig. 1 is a partly sectioned view of a preferred embodiment of an inventive hybrid dry-wet cooling tower arrangement,

[0022] Fig. 2 is an enlarged sectional view of a part of the embodiment of Fig. 1 ,

[0023] Fig. 3 is a partly sectional plan view of the arrangement of the wet cooling within the embodiment of Fig. 1 ,

[0024] Fig. 4 is an enlarged detail of Fig. 3,

[0025] Fig. 5 is a further preferred embodiment of the hybrid dry-wet cooling tower, in which individual wet cells are applied,

[0026] Fig. 6 is an enlarged sectional view of a part of the embodiment of Fig. 5,

[0027] Fig. 7 is a partly sectional plan view of the arrangement of the wet cooling within the embodiment of Fig. 5, and

[0028] Fig. 8 is an enlarged detail of Fig. 7.

[0029] MODES FOR CARRYING OUT THE INVENTION

[0030] The essence of the innovation is arranging the dry and wet cooling sections of a drywet hybrid cooling system in a tall (preferably min. 100 m and taller, without upper limit) natural draft cooling tower, which is used as primary device for inducing air flow through the dry cooling section, with such dry cooling section preferably dimensioned to be capable of providing significant part of cooling duty (up to 100% depending on actual duty and ambient conditions), thus creating a hybrid dry-wet cooling system realising significant electrical power and water savings compared to the prior art.

[0031] The inventive hybrid dry-wet cooling tower has preferably a round shape, and has a tower shell of either cylindrical or conical or slightly hyperbolic shape. It is intended to operate with high flexibility from point of view of the ratio of dry and wet heat rejection, since the capability of both may spread from 100% to 0% - depending on the ambient conditions, the water availability and price as well as the load conditions.

[0032] The dry air coolers are located outside of the tower structure and located all around it disposed above the ground level on supporting legs. The air coolers are preferably arranged in a so-called ‘delta’ form, being a known erection unit of the dry heat exchangers. Two sides of the triangular shape cooling delta are constituted by air cooler panels, the third one forms an air intake area and is equipped with louvers.

[0033] With regard to the amount of overall water saving and electrical power saving on the wet cooling section, there are two major variants of the invention, depending on the respective configuration of the wet cooling section.

[0034] Accordingly, Figs. 1 to 4 and Figs. 5 to 8 respectively show two preferred embodiments of the inventive hybrid dry-wet cooling tower arrangement. The figures show a hybrid dry-wet cooling tower for a hybrid cooling system, the cooling tower comprising a tower shell 10 having a lower edge 11 and an upper edge 12, and a leg arrangement of tower shell legs 13 supporting the tower shell 10 above the ground level. The leg arrangement provides an air intake between the ground level and the lower edge 11 of the tower shell 10.

[0035] The cooling tower further comprises:

[0036] - a natural draft dry cooled segment 20 being arranged outside and around said leg arrangement and being supported by support legs 21 above the ground level, the dry cooled segment 20 having upright - preferably vertical - air coolers equipped with external first louvers 22 for controlling cooling air inlet to the air coolers, wherein lower ends of the support legs 21 are fixed directly or indirectly to the ground and upper ends of the support legs 21 are fixed directly or indirectly to the air coolers;

[0037] - a top covering 23 for closing a circular gap between a top periphery of the dry cooled segment 20 and the lower edge 11 of the tower shell 10,

[0038] - a wet cooled segment 30 arranged inside of said leg arrangement and having wet cooling cells 31 arranged with a spacing from the leg arrangement and receiving cooling air through the air intake and via second louvers 32; and

[0039] - a separating cover 40 being a boundary of an air duct space 41 between the air intake and the wet cooling, the separating cover 40 having an outer rim and an inner rim and separating ambient air streaming towards the wet cooling from air warmed up by the dry cooled segment 20, wherein the outer rim of the separating cover 40 is arranged at said upper ends of the support legs 21 .

[0040] With regard to the amount of overall water saving, and electrical power saving on the wet cooling section, both of the two major variants of the invention exhibit the same novel and innovative features, in different configurations.

[0041] Figs. 1 to 4 show a preferred embodiment for moderate to high water saving, and maximum electrical power saving.

[0042] The wet cooled segment 30 in this case is a natural draft wet cooled segment 30, the natural draft on which is induced by the tower shell 10, wherein the wet cooling cells 31 are arranged in a centered arrangement with respect to said leg arrangement of tower shell legs 13, and wherein the inner rim of the separating cover 40 is formed along a perimeter of the centered arrangement of the wet cooling cells 31 . Preferably, in said centered arrangement each of the wet cooling cells 31 has a rectangular footprint, and the wet cooling cells 31 are arranged adjacently so as to form a common structural unit, and have a common water basin 34 for collecting water cooled by the wet cooling cells 31. The second louvers 32 are preferably arranged along the perimeter of the centered arrangement of the wet cooling cells 31. In this embodiment, the air movement through the wet cooling section or wet cooled segment 30 is also induced by the same common natural draft cooling tower shell 10. In this variant, the wet cooled segment 30 consists of wet cooling cells 31 arranged in a middle part of the cooling tower, which also has the dry cooled segment 20 comprising the upright dry air coolers arranged externally to the bottom perimeter and above the level of the separating cover 40, which is preferably a horizontal covering of the air supply space of the wet cooled segment 30. The air flows to the natural draft dry cooled segment 20 and to the natural draft wet cooled segment 30 are separated by the separating cover 40 and their air flow rates can be independently controlled by the separate first and second louvers 22, 32 specifically assigned to each section. In this configuration, the capabilities of both the wet and dry sections may feasibly and preferably be dimensioned to serve 100% heat dissipation duty individually, depending on actual duty and ambient conditions.

[0043] The embodiment of Figs. 1 to 4 is characterized by the wet cooled segment 30, which is arranged on the ground level in the middle part of the natural draft cooling tower, and which is dimensioned so that it is preferably capable of providing 100% cooling duty at all ambient conditions, its air flow being induced by the tower shell 10 of the natural draft cooling tower. The wet cooled segment 30 is preferably comprised of multiple similar natural draft wet cooling cells 31 having a rectangular footprint and being arranged adjacently so that they form a common structural unit, centrally located on the ground in the middle part of the cooling tower above their common water basin 34, from which the cooled water is delivered by circulating water pumps to a process to be cooled.

[0044] The cooling airflow enters the wet cooling section horizontally, via the air duct space 41 covered by the separating cover 40 extending from below the dry cooled segment 20 located at the external perimeter of the natural draft cooling tower. The air then passes in the wet cooling cells 31 through wet cooling fills and drift eliminators while mixing with warm water sprayed on the wet fills by sprayers 35. The warm water is delivered to the sprayers 35 via a network of water distributing piping 33 from the process to be cooled by the circulating water pumps. There are adjustable second louvers 32 arranged preferably all around the perimeter of the wet cooling section directly at its air intake, in order to make adjustment of airflow to the wet cooling section between 0 to 100% possible, thus allowing the corresponding adjustment of its heat dissipation duty relative to the heat dissipation duty of the dry cooling section.

[0045] Alternatively, the air intake second louvers 32 of the wet cooled segment 30 may be arranged at the external perimeter of the natural draft cooling tower, but this solution necessitates additional radial vertical separating walls in the air duct space 41 to allow for sectionalising of the wet section on the cooling water side.

[0046] The dry air coolers of the dry cooled segment 20 are arranged preferably vertically around the external perimeter of the natural draft cooling tower, more specifically of the leg arrangement of tower shell legs 13, at a sufficient height to allow ample cross section for the air duct space 41 located below the dry air coolers to ensure sufficient airflow to the wet cooled segment 30. The dry cooled segment 20 is preferably dimensioned so that it is capable of providing 100% cooling duty (depending on actual duty and ambient conditions), with its airflow induced by the natural draft cooling tower shell 10. The cooling airflow enters the dry air coolers horizontally, above the separating cover 40 and below the top covering 23 underneath the lower edge 11 of the tower shell 10, which is supported by the tower shell legs 13 of sufficient height to ensure sufficient airflow to both the wet and the dry cooling sections. After passing the dry air coolers, which are preferably water-to-air heat exchangers, the cooling air becomes less humid due to its temperature increase caused by the heat exchange, turns upwards and exits the cooling tower at the top, together with the humid air from the wet cooled segment 30, both induced by the natural draft of the common cooling tower shell 10. The warm water is delivered to the dry air coolers via a network of water distributing piping 24 from the process to be cooled by the circulating water pumps. The cold water from the dry air coolers is collected by a network of water collecting piping 25 and is delivered by the circulating pumps to the process to be cooled. The adjustable first louvers 22 are arranged preferably all around the perimeter of the dry cooled segment 20 directly at its air intake, in order to make adjustment of airflow to the dry cooled segment 20 between 0 to 100% possible, thus allowing the corresponding adjustment of its heat dissipation duty relative to the heat dissipation duty of the wet cooled segment 30.

[0047] For reasons of operational flexibility and optimal maintenance planning, both the wet cooled segment 30 and the dry cooled segment 20 are preferably further sectionalised on the cooling water side and on the air side.

[0048] Figs. 5 to 8 show a preferred embodiment for maximum water saving and moderate to high electrical power saving.

[0049] In this embodiment the wet cooled segment 30 comprises separate wet cooling cells 31 arranged in a circular arrangement. Each of the wet cooling cells 31 has a top fan 37 for inducing upwards humid air exhaust flow, and each of the wet cooling cells 31 is connected to a separate air duct space 41 section. Each air duct space 41 section is limited from above by a respective separating cover 40 and from two sides by respective separating side covers 50. Preferably, the second louvers 32 are arranged externally to the support legs 21 . Each of the wet cooling cells 31 has preferably a separate water basin 34 for collecting water cooled by the wet cooling cell 31 , or alternatively the wet cooling cells 31 may share a ring-shaped common water basin 34.

[0050] Thus, in this embodiment the wet cooling section is composed of wet cooling cells 31 with their draft assisted by axial top fans 37 arranged within and along the leg arrangement of the tower shell 10. Again, the dry cooling section consists of upright dry air coolers arranged externally to a bottom perimeter and above the air duct space 41 sections, which are encased by horizontal separating covers 40 and vertical side covers 50. The air flows to the natural draft dry cooled segment 20 and to the induced draft wet cooled segment 30 are separated by the horizontal separating covers 40 and the vertical side covers 50 and their air flow rates can be independently controlled by the separate first and second louvers 22, 32 specifically assigned to each section. In this configuration, the capability of the dry cooled segment 20 may feasibly and preferably dimensioned to serve 100% heat dissipation duty, depending on actual duty and ambient conditions, while the wet cooled segment 30 is primarily dimensioned to serve only partial heat dissipation duty at most ambient conditions. However, depending on actual duty and ambient conditions, it may also serve 100% cooling duty as well.

[0051] Accordingly, here the wet cooled segment 30 consists of several individual wet cooling cells 31 arranged on the ground level around the inner perimeter of the leg arrangement of the common natural draft cooling tower shell 10. The wet cooled segment 30 is primarily dimensioned so that it is capable of providing partial cooling duty only at most ambient conditions, thus contributing to significant water savings, however, depending on actual duty and ambient conditions, it may serve 100% cooling duty as well. This wet cooled segment 30 is preferably comprised of multiple similar individual wet cooling cells 31 of a rectangular footprint which are arranged on the ground level preferably equidistantly along the inner perimeter of the leg arrangement of the tower shell legs 13, with a spacing from the leg arrangement towards the center of the cooling tower. Preferably each wet cooling cell 31 has its separate water basin 34 from which the cooled water is delivered by circulating water pumps 36 of each wet cooling cell 31 to the process to be cooled. Alternatively - especially in case of a high number of wet cooling cells 31 in the same configuration - their water basin 34 may take the form of a common ring, and multiple wet cooling cells 31 may be served by one circulating water pump 36, also depending on water side sectionalisation.

[0052] The cooling airflow enters the wet cooling cells 31 horizontally, via the air duct space 41 sections, each covered by a respective separating cover 40 and vertical side covers 50 extending from below the dry cooled segment located at the external perimeter of the natural draft cooling tower. The air then passes in the wet cooling cells 31 through wet cooling fills and drift eliminators while mixing with the warm water sprayed on the wet fills by sprayers 35. The warm water is delivered to the sprayers 35 via a network of water distributing piping 33 from the process to be cooled by the circulating water pumps. As the wet cooling cells 31 are placed inside the leg arrangement of the tall natural draft cooling tower shell 10, which has significant natural draft, this arrangement allows additional electrical power saving on the mechanical draft, because only a portion of the total draft of the wet cooling cells 31 shall be provided for by the axial top fans 37. There are adjustable second louvers 32 at the air intakes of the air duct spaces 41 leading to the wet cooling cells 31 , arranged preferably at the external perimeter of the natural draft cooling tower, in order to make adjustment of airflow to the wet cooled segment 30 between 0 to 100% possible, thus allowing the corresponding adjustment of its heat dissipation duty relative to the heat dissipation duty of the dry cooled segment 20.

[0053] The dry cooled segment 20 can be formed and dimensioned as in the first embodiment, so that it is preferably capable of providing 100% cooling duty, depending on actual duty and ambient conditions, with its airflow induced by the natural draft cooling tower shell 10.

[0054] Again, for reasons of operational flexibility and optimal maintenance planning, both the wet cooled segment 30 and the dry cooled segment 20 are preferably further sectionalised on the cooling water side and on the air side.

[0055] In particular embodiments, the upper edge 12 of the tower shell 10 is at least 100 m, preferably at least 120 m, more preferably at least 140 m above the ground level. These height dimensions ensure a dominant and effective natural draft air flow.

[0056] Preferably, each of the dry cooled segment 20 and the wet cooled segment 30 is dimensioned to be able to provide a total required heat dissipation alone, and wherein air flow rates on the dry cooled segment 20 and on the wet cooled segment 30 are independently controllable by means of the first louvers 22 and of the second louvers 32.

[0057] The structural and arrangement configurations presented for both above variants can serve any hybrid dry-wet cooling system with regard to the cycle connection, irrespective of its specific type - e.g. whether the wet and dry cooling sections are connected in series or they constitute parallel or separate circuits on the cooling water side. The flexibility of the invention is manifested both in the possibilities it provides for design optimisation of a planned hybrid dry-wet cooling tower, and for optimal operation of an already executed hybrid dry-wet cooling tower.

[0058] With regard to design optimisation, the total nominal cooling capability of such a hybrid dry-wet cooling tower and relative proportions of the nominal cooling capabilities of the dry and wet cooling sections can be tailor-made easily to best match any given set of foreseen economic, environmental and operational variables (e.g. material, water prices, electricity prices, climatical conditions, operation schedule etc.) by proper selection of

[0059] - dry air cooler type, thermal, hydraulic and air side characteristics, dimensions and quantities;

[0060] - wet cooling fill, sprayer, drift eliminator type, thermal, hydraulic and air side characteristics, dimensions and quantities;

[0061] - natural draft cooling tower shell dimensions, i.e. total height, height of shell support legs, throat and bottom diameter;

[0062] - circuitry of the cooling water side (i.e. type of water side connection between dry and wet cooling sections), dimensions of respective cooling water distributing and collecting piping;

[0063] - type and characteristics of air intake louvers of both the dry and wet cooling sections;

[0064] - type and characteristics of circulating water pumps and flow regulating elements; and by performing thermo-hydraulic sizing, including determining the proportions of cooling water flows to the wet and dry cooling sections, calculating the rates of air flow for each section, and thus ultimately the total heat dissipation and its distribution between the wet and dry cooling sections, and calculating the corresponding water consumption and electrical power consumption.

[0065] With regard to optimal operation of such a hybrid dry-wet cooling tower, the actual total cooling capability and relative proportions of the actual cooling capabilities of the dry and wet cooling sections, and thus the actual water consumption and electrical power consumption can be adjusted to best match any given set of actual economic, environmental and operational variables (e.g. actual water prices, electricity prices, climatical conditions, operation schedule) by

[0066] - independent adjustment of the airflows of the wet and dry cooling sections by the corresponding adjustment of the air intake louvers of each section; - independent adjustment of the cooling water flows of the wet and dry cooling sections;

[0067] - shutting down parts of the wet or the dry cooling sections, as allowed by sectionalising by design; and

[0068] - shutting down either the wet or the dry cooling section entirely.

[0069] The invention is not limited to the preferred embodiments described in details above, but further variants, combinations, modifications and developments are possible within the scope determined by the claims.

Claims

CLAIMS1. A hybrid dry-wet cooling tower for a hybrid cooling system, the cooling tower comprising a tower shell (10) having a lower edge (11 ) and an upper edge (12), and a leg arrangement of tower shell legs (13) supporting the tower shell (10) above a ground level, the leg arrangement providing an air intake between the ground level and the lower edge (11 ) of the tower shell (10), characterized in that the cooling tower further comprises:- a natural draft dry cooled segment (20) being arranged outside and around said leg arrangement and being supported by support legs (21 ) above the ground level, the dry cooled segment (20) having upright air coolers equipped with external first louvers (22) for controlling cooling air inlet to the air coolers, wherein lower ends of the support legs (21 ) are fixed to the ground and upper ends of the support legs (21 ) are fixed to the air coolers;- a top covering (23) for closing a circular gap between a top periphery of the dry cooled segment (20) and the lower edge (11 ) of the tower shell (10),- a wet cooled segment (30) arranged inside of said leg arrangement and having wet cooling cells (31 ) arranged with a spacing from the leg arrangement and receiving cooling air through the air intake and via second louvers (32); and- a separating cover (40) being a boundary of an air duct space (41 ) between the air intake and the wet cooling, the separating cover (40) having an outer rim and an inner rim and separating ambient air streaming towards the wet cooling from air warmed up by the dry cooled segment (20), wherein the outer rim of the separating cover (40) is arranged at said upper ends of the support legs (21 ).

2. The cooling tower according to claim 1 , wherein the wet cooled segment (30) is a natural draft wet cooled segment (30), the natural draft on which is induced by the tower shell (10), wherein the wet cooling cells (31 ) are arranged in a centered arrangement with respect to said leg arrangement of tower shell legs (13), and wherein the inner rim of the separating cover (40) is formed along a perimeter of the centered arrangement of the wet cooling cells (31 ).

3. The cooling tower according to claim 2, wherein in said centered arrangement each of the wet cooling cells (31 ) has a rectangular footprint, and the wet cooling cells (31 ) are arranged adjacently so as to form a common structural unit, and have a common water basin (34) for collecting water cooled by the wet cooling cells (31 ).

4. The cooling tower according to claim 3, wherein the second louvers (32) are arranged along the perimeter of the centered arrangement of the wet cooling cells (31 ).

5. The cooling tower according to claim 1 , wherein the wet cooled segment (30) comprises separate wet cooling cells (31 ) arranged in a circular arrangement, each of the wet cooling cells (31 ) having a top fan (37) for inducing upwards humid air exhaust flow, and each of the wet cooling cells (31 ) being connected to a separate air duct space (41 ) section, each air duct space (41 ) section being limited from above by a respective separating cover (40) and from two sides by respective separating side covers (50).

6. The cooling tower according to claim 5, wherein the second louvers (32) are arranged externally to the support legs (21 ).

7. The cooling tower according to claim 5, wherein each of the wet cooling cells (31 ) has a water basin (34) for collecting water cooled by the wet cooling cell (31 ), or the wet cooling cells (31 ) share a ring-shaped common water basin (34).

8. The cooling tower according to claim 1 , wherein the upper edge (12) of the tower shell (10) is at least 100 m, preferably at least 120 m, more preferably at least 140 m above the ground level.

9. The cooling tower according to claim 1 , wherein each of the dry cooled segment (20) and the wet cooled segment (30) is dimensioned to be able to provide a total required heat dissipation alone, and wherein air flow rates on the dry cooledsegment (20) and on the wet cooled segment (30) are independently controllable by means of the first louvers (22) and of the second louvers (32).