EP0855568B1 - Fluid distribution network for a cooling tower - Google Patents

Description

The present invention relates to a distribution network of liquid, in particular water, for installation atmospheric refrigerant industrial of the type comprising a set of tubes parallel to each other and substantially horizontal, connected at one end by a collector or liquid supply tank, and equipped with liquid dispersers.

We know that in atmospheric refrigerants, hot water is distributed regularly, over the entire useful surface of the device, by a network of tubes connected to an indoor collector or an open pit. These tubes are fitted with nozzle-dispersers, the function of which is to regulate distributing the flows and spraying the water to be cooled into fine droplets.

q = K S 2 g H

avec q = débit d'eau

S = section de l'ajutage

K = coefficient de striction

g = accélération de la pesanteur

H = charge sur l'ajutage (pression d'eau)

The flow rate of a nozzle is given by the classic expression:

q = KS 2 g H

with q = water flow

S = section of the nozzle

K = necking coefficient

g = acceleration of gravity

H = load on the nozzle (water pressure)

In a standard device, when the flow rate increases, the load necessary increases in proportion to the square of the flow. So if we doubles the flow, the water load is multiplied by four. The tubes of distribution and the nozzles-dispersers are then subjected to strong constraints affecting their durability over time, which can cause rupture of the plastic dispersers of which the nozzles-dispersers. In this event, water jets are obtained, the pressure is four times higher, which gradually deteriorate the body heat exchange located immediately below the nozzles-dispersers.

To limit this risk and also that of water freezing when the air temperature is below 0 ° C, it has already been proposed to double the distribution network by an auxiliary distribution network, which is not supplied only in the event of an overload or overpressure on the first network. However, such an achievement has the disadvantages of making the entire installation particularly expensive, and to operate only in spurts, from predetermined thresholds.

We also know from GB 829 555, to solve a another problem, more specifically to mitigate the reduction in efficiency water cooling towers when their supply rate decreases below nominal flow, water distribution networks comprising substantially horizontal tubes connected to one of their ends to a liquid supply pan around which they extend radiant and which are equipped with liquid dispersers, networks in which a part of the tubes is provided with means for switch off these tubes when the supply flow decreases in below the nominal flow rate in order to maintain the same performance for liquid dispersers remaining in service.

The object of the invention is to provide a distribution network for. liquid arranged to solve the problem without requiring the addition of an additional auxiliary network.

To this end, the invention relates to a liquid distribution network for atmospheric refrigerant, comprising a set of tubes substantially horizontal connected at one of their ends by a collector or liquid supply tank and fitted with liquid, in which part of the tubes is provided with means for put a section of each of the tubes of said part of the tubes practically out of circuit liquid at nominal liquid flow rate, and to use them as soon as a overflow above the nominal flow, the tubes of said set of tubes being parallel, and the ends of the tubes of said set of tubes opposite the tank or collector being connected between them by a pipeline.

Alternatively, the invention relates to a distribution network of liquid for atmospheric refrigerant, comprising a set of tubes substantially horizontal connected at one of their ends by a collector or liquid supply tank and fitted with liquid, in which part of the tubes is provided with means for put a section of each of the tubes of said part of the tubes practically out of circuit liquid at nominal liquid flow rate, and to use them as soon as a overflow above the nominal flow, the tubes of said set of tubes being parallel, and the ends of the tubes of said set of tubes opposite the tank or collector being connected to due to two consecutive tubes or three consecutive tubes of said set of tubes.

So at the nominal liquid delivery rate, it flows essentially in tubes not provided with the aforementioned means, which however allow a small part of the flow to flow through the tubes equipped with said means.

According to one embodiment, in which the network comprises a open pit, the aforementioned means include one end of said tubes bent at the beak and oriented upwards, as well as an arranged nozzle at the base of this bent end; therefore at nominal flow the tube correspondent is supplied with fluid by the nozzle with a very low flow rate, while at a higher flow rate of a predetermined value, it can also be fed through the opening of the angled end.

These arrangements advantageously replace in accordance with the invention the classic "rake" arrangement with tubes connected to their ends only by the tank or the collector, the ends opposites being free. Such a liquid distribution network, in particular hot water, can accept and distribute correctly, gradually, quantities of liquid up to twice the nominal flow rate without increasing the pressures prohibitively.

Other advantages of the invention will become apparent from during the description which follows, made with reference to the accompanying drawings which illustrate several embodiments thereof by way of examples.

Figure 1 is a schematic perspective view of a first embodiment of the liquid distribution network for atmospheric refrigerant according to the invention.

Figures 2 and 3 are schematic elevational views similar to Figure 1 illustrating its mode of operation.

Figure 4 is a mid-sectional mid-elevation view partial of the collecting tank of a distribution network of the sky tank type open, as well as a corresponding embodiment of the means of deactivation of certain tubes in this network.

Figure 5 is a schematic top view of the network of distribution according to the embodiment of FIG. 4.

Figure 6 is a partial elevational view of a second form for producing means for switching off a tube of a network of the type with collector.

Figure 7 is a schematic top view of the network of distribution corresponding to figure 6.

Figures 8 and 9 are schematic plan views of two other possible embodiments of the distribution network according to the invention.

The distribution network shown in Figures 1 to 3 is intended for the distribution of liquid, in particular hot water, for refrigerants atmospheres used in certain industrial installations.

This network includes a set of tubes 1, 2, 3, 4, 5 ... mutually parallel and substantially horizontal, connected to one of their ends by a manifold or tank 6 for liquid supply. Tubes 1, 2 ... are equipped with "nozzle-dispersers" or more simply "dispersers" 7 of liquid, for example of the shower head type.

A part of the tubes 1 .... 5 ..., for example one in two, is provided means 8 schematically represented, making it possible to put a section of each of the tubes correspondents 2, 4 ... practically out of liquid circuit when the latter is supplied at nominal flow rate, only the other tubes 1, 3, 5 ... not fitted with means 8, then being supplied. Means 8, including modes of realization will be described below, are arranged to allow the supply in cash only if these sections are exceeded a determined flow threshold above the nominal flow.

The ends of the tubes 1, 2, 3, 4, 5 ... opposite the tank or collector 6 are connected together by a pipe 9.

During normal operation, at nominal liquid flow, the height of liquid in tank 6 (or pressure in manifold 6) is less than a height H. Each tube 1, 3, 5 ... is supplied normally in liquid while the tubes 2, 4 ... equipped with the means 8 are supplied only through a member of the means 8 ensuring a flow restriction. The small amount of corresponding liquid which flows in the tubes 2, 4 ... enables the dispersers 7 to be supplied only on an ED section (Figures 1 and 2) while the other tubes such as 1, are powered normally. Therefore, the amount of liquid received in these tubes (arrow F figure 1) allows to feed not only the entire length corresponding AB of tube 1 ... but also the connecting part BC between the tubes 1, 2 etc and the sections such as CD of tubes 2 .... equipped with the means 8, as indicated by the arrows.

As the liquid flow increases, the height of the liquid in the tank 6 (or the pressure in the manifold 6) becomes greater than the height H. The tubes 2, 4 ... can then be supplied by means 8 which come into action, which allows a much greater flow in the tubes 2, 4 ... for supplying ED 'sections of greater length at ED. Correlatively the corresponding tube 1, 3 ... feeds a section ABCD 'smaller than the initial section ABCD (Figures 2 and 3).

Such a liquid distribution network can accept and distribute suitably water flows much higher than the nominal flow, and this in using the same single network, without an auxiliary network.

FIG. 4 shows a first embodiment possible of the aforementioned means 8, suitable for a network of the collecting tank type 11 in the open. In this network part of the tubes, for example one on two or one in three, has bent ends 12 in the shape of a beak and oriented upwards, the elbow being substantially at right angles and extending over a height H. A nozzle 13 constituted by a hole of weak diameter is provided at the base of the angled end 12 and opens into the corresponding horizontal tube 2, 4 ...

At nominal flow rate (level N1 of the liquid in tank 11), the tube correspondent 2 (4 ...) is supplied with liquid at a low flow rate, through the nozzle 13, the other tubes, devoid of the spouts 12, being supplied with liquid at nominal flow. On the other hand when the flow rate increases so that the level in tank 11 reached and exceeds that of the upper end of the elbow or spout 12 (maximum level N2), the liquid enters the elbow 12 and pours into tube 2 (4 ...). This can increase the flow up to approximately twice the nominal flow rate, without causing excess pressure troublesome in the network, so without risking a deterioration of dispersers 7.

Alternatively, the constriction at the base of the spouts 12 can be achieved by several nozzles such as 13, or with holes, or slots or bevels. This or these nozzles can also be fitted with rings adjustment (not shown).

Alternatively also the upper opening of the spouts 12 can be bevelled as shown in dashed lines referenced 14.

The distribution network corresponding to the embodiment of Figure 4 is shown in Figure 5.

In the second embodiment, illustrated in Figures 6 and 7, the distribution network is of the closed tubular collector type 15. The means 8 liquid shutdown include, for each of the tubes concerned, for example one tube (2, 4, 10) out of two a tubular stock 16 arranged in an inverted U between the associated tube 2 (4 ...) and the manifold 15, and connected to them. Lacrosse 16 is completed at its base by a constriction 17 connecting the ends of the stick between them as well as tube 2 (4 ...) and manifold 15.

At nominal flow, the liquid pressure in the manifold 15 is not not sufficient for this liquid to pass through the butt 16. A small fraction this liquid therefore flows through the throttles 17 in the tubes 2 (4 ...), while the other tubes 1, 3, 5 are normally supplied. When the pressure in manifold 15 exceeds a predetermined value, corresponding at the height H of FIGS. 1 and 4, the liquid enters the butt 16 that it crosses, to then flow into the corresponding tube 2, 4 ... This butt system 16 and nozzle 17 therefore allows, like the device of the figure 4, to cope with an increase in the network supply speed up to approximately double the nominal flow, without repercussion annoying on the network.

In the variant embodiment illustrated in FIG. 8, the tubes 1, 2 ... are connected two by two by their ends opposite the collector or feed spout 6: are connected together by a pipe 16 the ends of tubes 1, 2, then tubes 3 and 4, 5 and 10 ..., every other tube each of these pairs being able to be provided with the means described above of liquid shutdown.

In the embodiment of Figure 9, the ends of the tubes are connected three by three: thus are connected to each other by a pipe 17 the ends of the tubes 1, 2, 3, then the tubes 2, 3, 4 etc, one at less of these groups of three tubes being provided with the aforementioned means of setting out of the liquid circuit.

In addition to the advantages mentioned above, the invention presents that of ensuring correct operation of the refrigerant (distribution of liquid) on a regular basis according to the variations in flow, and not so "brutal" as soon as a predetermined water level is reached (or a value predetermined water overpressure), as in the case of the realization known previously mentioned auxiliary network doubling the network main.

Claims (6)

1. Fluid distribution network for a cooling tower comprising an assembly of more or less horizontal pipes (1, 2, 3 etc.) connected at one of their ends by a fluid feed manifold or tank (6) and fitted with fluid sprayers (7), whereby some of the pipes (2, 4 etc.) are provided with means (8) for putting a section of each of the pipes in the said number of pipes practically out of the fluid circuit at the nominal fluid delivery (N1), and for using them as soon as an overdelivery above the nominal delivery appears, the pipes in the said assembly of pipes being parallel and the ends of the pipes (1, 2 etc.) of the said assembly of pipes opposite the tank or manifold (6) being connected to each other by a duct 9.
2. Fluid distribution network for a cooling tower, comprising an assembly of more or less horizontal pipes (1, 2, 3 etc.) connected at one of their ends by a fluid supply manifold or tank (6) and fitted with fluid sprayers (7), whereby some of the pipes (2, 4 etc.) are provided with means (8) for putting a section of each of the pipes in the said number of pipes practically out of the fluid circuit at the nominal delivery (N1), and for using them as soon as an overdelivery above the nominal delivery appears, the pipes in the said assembly of pipes being parallel and the ends of the pipes (1, 2 etc.) of the said assembly of pipes opposite the tank or manifold (6) being connected at the rate of two consecutive pipes (1-2, 3-4 etc.) or three consecutive pipes (1-2-3, 4-5-10 etc.) of the said assembly of pipes.
3. Network according to any one of the Claims 1 and 2, characterised in that the tank is an open tank (11) and the said means comprise an end of the said pipes (2, 4 etc.) of the said number of pipes bent in the form of a spout (12) and directed upwards, as well as a nozzle (13) arranged at the base of this bent end so that, at nominal delivery (N1), the relevant pipe of the said number of pipes is supplied with fluid by the nozzle and so that, at a higher delivery, it can also be supplied through the opening in the bent end as soon as this overdelivery (N2) is sufficient.
4. Network according to Claim 3, characterised in that the bent end is bevelled (14).
5. Network according to any one of the Claims 1 and 2, characterised in that the manifold is a closed tubular manifold (15) and the said means comprise a tubular crosshead (16) arranged as an inverted U bctween the pipe (2, 4 etc.) of the said number of pipes and the manifold and connected to them, as well as a throttle (17) connecting the ends of the crosshead at the level of this pipe and of the manifold.
6. Network according to Claim 5, characterised in that the pipes (2, 4 etc.) of the said number of the pipes fitted with the said crossheads (16) for putting fluid out of the circuit at the nominal level and the other pipes (1, 3 etc.) of the said assembly of pipes are superimposed, the pipes provided with the crossheads being arranged in the lower plane.

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