EP0437133A1 - Fluid cooling device for cooling tower - Google Patents

Abstract

Fluid-cooling device for a cooling tower of the fan or natural draught type, comprising a set of fluid-dispersers (10), a heat exchange body (1, 9), at a number of superposed levels, through which a stream of atmospheric air and a trickling flow of the fluid to be air-cooled can travel, characterised in that the exchange body (1, 9) is coated in its upper part with a substantially horizontal shield (9) through which water can trickle, with mechanical characteristics which are superior to those of the remainder of the exchange body on which it is removably mounted; this shield (9) forms a wear layer for protecting the underlying levels of the said exchange body. Application to all cooling towers for industrial plant, such as thermal and nuclear power stations. <IMAGE>

Description

The present invention relates to a fluid refrigeration device for atmospheric refrigerant with natural draft or mechanical ventilation.

We know that an atmospheric refrigerant is a heat exchanger which removes a certain amount of heat from a water circuit. This is transmitted to the atmosphere, the water being returned at a lower temperature. Air serves as a cooling fluid using the physical phenomenon of evaporation, the transfer of heat from water to air being effected by convection and by evaporation.

When they are mechanically ventilated, the refrigerants are fitted with one or more fans, either blowers or extractors. In the first case, the air is blown by one or more fans placed at the base of the refrigerant. In the second case, the ventilator (s) cover the refrigerant box, and the air sucked in by the ventilator circulates either horizontally (refrigerant of the "cross-current" type) while the water is distributed from external platforms , or vertically from bottom to top, against the current of the vertically dripping water flow ("counter-current" type refrigerant).

When the refrigerants are natural draft, the air is conveyed by draft effect by means of a tower, the operation of the device can also be cross-current or counter-current.

The heat exchange bodies form large parallelepiped volumes, consisting of several superposed levels of exchange surfaces. These can be formed by assemblies of plastic sheets suitably profiled and arranged substantially vertical, or gratings, grids or slats made of plastic or other material chosen by considering the atmosphere and the quality of the water. The plastic used in both cases can be, for example, polypropylene, PVC, polystyrene.

The hot water is distributed on the upper surface of the exchange body by supply tubes leaving the installation to be cooled, for example a condenser, a temperature exchanger. These supply tubes are equipped with fluid dispersers, constituted by appropriately distributed sprinkling heads.

The hot water trickles through the entire height of the heat exchange body.

FR-A 1489861, US-A 467815, US-A 3346246, EP-A 0264581 and US-A 4317785 describe refrigeration systems in which the exchange bodies include distribution elements at the top such as 40 ( FR-A 1489861). These elements have the function of ensuring a relatively uniform distribution of the fluid in the exchange body, of which they form an integral part and to which they do not provide any particular protection against wear. In addition they are not mounted removable or are difficult to disassemble.

The installation targeted by the invention is therefore a device for trickling the fluid to be cooled, disposed inside a box equipped with one or more fans as indicated above, or more generally of a gas cooling or washing tower. This device is used in all cases where water is sprayed into an air flow.

After a number of years of use, it can be seen that under certain operating conditions, aging appears to degrade the upper part of the exchange body, while the rest of the heat exchange body is relatively well preserved and therefore capable of continuing to fulfill its function with further good durability.

It is assumed that this aging, which is the cause of disorders, results from the repeated shocks of drops of water on the plastic material constituting the exchange body, as well as various physical, mechanical and chemical attacks undergone by the exchange body. In other words, this aging would result from the combined effects of the mechanical and vibratory stresses of the jets of distribution water with the resulting stresses of the thermal gradients. The nature or quality of the water could also be a determining factor.

When this wear of the upper part of the lining constituting the exchange body creates sufficiently troublesome disturbances, it is therefore necessary to replace at least the different levels thus worn. In fact, it generally replaces all of the different levels of the exchange body, which is a long operation and therefore costly in labor.

The object of the invention is therefore to produce a refrigeration device of this type, the service life of which can be considerably increased, with simple mechanical means, and inexpensive to maintain.

According to the invention, the fluid refrigeration device is characterized in that the exchange body is coated, at its upper part, with a substantially horizontal shield through which the water can run off, with mechanical characteristics superior to those of the rest of the exchange body on which it is removably mounted, forming a layer of wear and protection of the underlying levels of said exchange body, and the dispersers are arranged and positioned above the heat exchange body at a height such that these dispersers ensure uniform fluid distribution over said exchange body.

Thus the mechanical resistance of this wear layer, on which the fluid uniformly distributed by the dispersers falls, is greater than that of the other levels of the heat exchange body, protects the most sensitive part of the latter and therefore increases its duration. of life. Because it is easily removable, it can be replaced after wear at a low cost compared to that of replacing the entire exchange body.

According to one embodiment of the invention, the shield is constituted by a set of panels with a honeycomb structure, the cells of which are delimited by intersecting bands on which the water can flow from top to bottom and drip on the level underlying the exchange body.

Other features and advantages of the invention will appear during the description which follows, given with reference to the accompanying drawings which illustrate two embodiments thereof by way of non-limiting examples.

Figure 1 is a perspective view of a first embodiment of a hot water refrigeration device for an atmospheric refrigerant with mechanical or natural ventilation comprising a coolant heat exchange body equipped with a wear shield according to the invention.

FIG. 2 is a perspective view similar to FIG. 1 of a second embodiment of an exchange body and its wear shield according to the invention.

Figure 3 is an elevational view on an enlarged scale of one of the fluid dispersers shown in Figure 1.

The cooling device shown in FIG. 1 is housed in a box, not shown, and comprises a heat exchange body 1, of generally parallelepiped shape, on the upper surface of which are arranged a series of pipes 2 of hot water distributors, parallel and horizontal. The pipes 2 are fixed to the beams 3 by collars 4, in a manner known per se, and form part of a structure comprising longitudinal members 5 and the beams 3, on which rest sets of panels 6 drop separators. Each pipe 2, placed at a suitable height above the upper surface of the exchange body 1, is provided with a series of fluid dispersers 10 suitably distributed along the pipe. These dispersers 10 are at a suitable height H above the heat exchange body 1, and produced so as to ensure a uniform or almost uniform distribution of the fluid over the upper part of the heat exchange body 1.

The heat exchange body 1 comprises a frame known per se, consisting of a set of vertical lines 7 for supporting several horizontal levels superimposed on grids 8 of suitably profiled plastic. This refrigerant can either be of the so-called "cross-current" type or of the "counter-current" type.

The upper part of the heat exchange body 1 comprises a substantially horizontal shield 9 placed in abutment on the upper surface of the exchange body 1. The shield 9 consists of a set of panels 11, preferably rectangular, dimensioned and placed side by side so as to cover almost all of the upper surface of the body 1, and arranged so that hot water can flow through said panels 11.

In the embodiment of FIG. 1, each panel 11 is constituted by a grid or a grating of an appropriate plastic material, or of aluminum, of the same kind as that of which the individual grids 8 of the body are made up. The grids 11 can be of the same type as the grids 8, or of a different structure, but in all cases they have mechanical, chemical and physical characteristics clearly superior to those of grids 8, therefore a greater longevity. The grids 11 are placed on the grids 8 of the upper level in an easily removable manner, by any means known per se and not shown. The set of grids 11 therefore forms a layer of wear and of protection of the underlying levels of the exchange body 1 against their aging and their degradation under the effect of the various attacks which they undergo over time, in particular repeated shocks of water drops. This protection is exercised in the first place with respect to the upper level of the body 1, placed immediately below the wear shield 9, which is thin (for example 2 cm).

The dispersers 10 of fluid to be cooled, can be produced for example as visible more particularly in FIG. 3, on which is shown a structure similar to that of disperser device described in French patent 1,522,450.

Each disperser 10 thus comprises a stirrup or collar 16 screwed by its upper part onto a nozzle 17, fixed under the pipe 2, a cup 18 carried by the lower end of the collar 16 and the concavity of which faces upwards. that is to say towards the nozzle 17, and an annular deflector 19. The latter is positioned above the cup 18 and fixed to the stirrup 16 so that its central opening, intended to allow the jet of fluid to pass to be cooled coming from the nozzle 17, ie located above the cup 18.

The deflector 19 has a peripheral edge directed downwards, and cut so as to form a succession of slots and teeth 20, as described in French patent 1,522,450, in order to fold down the fluid coming from the cup 18 .

The dispersers 10 are placed above the grids 11 of the shield 9 at a height H, (defined as the distance between the lower generatrices of the pipes 2 and the grids 11), determined so that the distribution of the fluid on the grids 11 is practically uniform, as shown in the drawings of the aforementioned French patent. The height H can advantageously be approximately 700mm, the height h of the dispersers 10 themselves being possibly 170mm approximately.

After wear, for example after a minimum period of five years, all of the panels 11 can be replaced without difficulty, leaving in place the entire body 1 located below this shield 9. The shield 9 can be removed relatively quickly, intervention times are compatible with normal unit maintenance shutdowns. Thanks to the shield 9, the body 1 does not undergo any significant wear, including at its upper level, even after a long period of service.

The wear shield 9 participates in the heat exchange between the hot water and the cooling air, and can be installed whatever the type or origin of the lining constituting the superimposed levels, constituted by the grids 8 .

The lifetime of the heat exchange body 1 devoid of the wear layer 9, which is for example ten years, can be doubled thanks to the wear layer 9, of which only replacement becomes necessary. after several years.

Fig. 2 illustrates a second embodiment of the exchange body 12 and its wear shield 13. This refrigerant is of the counter-current type, and the rest of its structure is similar to that shown in FIG. 1.

The heat exchange body 12 is constituted by several superposed levels, each of which is formed by a set of sheets or films 14 of plastic material such as polypropylene, PVC, suitably profiled in a manner known per se. The removable wear layer formed by the shield 13 is formed by a set of panels 15 according to the same principle as those with a honeycomb structure. The cells 15a are delimited, in a manner known per se by interlaced bands, preferably made of plastic material such as polypropylene, on which the water can flow from top to bottom and drip on the upper level of the exchange body. 12. Each panel 15 rests horizontally on the upper level of the body 12 and is optionally removably attached thereto, by any suitable means known in self and not shown.

The pipes 2 are here provided with dispersers 21 consisting of sprinklers of a shape different from the dispersers 10, but operating according to the same principle, arranged in a known manner and also placed at a height H above the shield 13 in order to ensure on the latter a practically uniform distribution of fluid.

As in the previous case, the panels 15 are specially made so as to have a mechanical, physical and chemical resistance greater than that of the levels of the heat exchange body 12. The advantages and technical effects of the shield 13 are similar to those of the shield 9. When they have undergone a certain wear, only their replacement becomes necessary, excluding that of the different levels of the exchange body 12. It will be noted that the wear layers can be placed on old surfaces of 'exchange.

The distributor pipes 2 can be replaced either by gutters or by a perforated platform. Finally, the panels 15 can replace the grids 11, but not the reverse.

Claims (5)

Fluid refrigeration device for atmospheric refrigerant of the natural draft or mechanical ventilation type, comprising a set of dispersers (10, 21) of the fluid to be cooled by air, a heat exchange body (1, 12), placed below the dispersers and at several superimposed levels, through which a stream of atmospheric air and a trickle flow of the fluid to be cooled by air can circulate, characterized in that the exchange body (1, 12) is coated at its upper part with a shield (9, 13) substantially horizontal through which the water can flow, with mechanical characteristics superior to those of the rest of the exchange body on which it is removably mounted, forming a wear and protection layer for the levels below said exchange body, and the dispersers (10, 21) are arranged and positioned above the heat exchange body (1, 12) at a height (H ) as these disperses urs ensure uniform fluid distribution over said exchange body. Device according to claim 1, characterized in that the shield (13) is constituted by a set of panels (15) with a honeycomb structure, the cells (15a) of which are delimited by interlaced bands on which the water can run off from above at the bottom and drip on the upper level of the exchange body (12), these panels (15) resting horizontally on the upper level of the exchange body. Device according to claim 1, characterized in that the shield (9) consists of a set of grids (11) through which the water can flow vertically and drip on the upper level of the exchange body (1), these panels resting horizontally on the upper level of the exchange body. Device according to any one of Claims 1 to 3, characterized in that the shield (9, 13) is optionally fixed to the upper surface of the exchange body (1, 12) in an easily removable manner by suitable means. Device according to any one of Claims 1 to 4, characterized in that the fluid dispersers (10) each comprise a cup (18) whose concavity faces upwards, and an annular deflector (19) positioned above from this cup, this deflector being hollowed out in its central part to let pass a jet of incident fluid and adapted at its periphery to fold down the fluid coming from the cup.

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