FR2745559A1 - METHODS AND APPARATUS FOR DOSING AND EVAPORATING LIQUIDS AND DISPERSING THEM IN LARGE VOLUMES OF FLUIDS - Google Patents

Abstract

The invention relates to a device for delivering a controlled flow rate of less than 2L per day of a liquid, characterized in that it comprises: a closed container containing said liquid, said container being provided with an outlet for the liquid; means for applying to said liquid a force which tends to cause said liquid to exit through said orifice; - means for creating in said container a relative pressure in relation to the outlet of said liquid, said relative pressure opposing the effect of said force on said liquid; and - means capable of creating over at least part of their length a laminar flow to control the inlet flow rate of a gas into said container, whereby the gas inlet flow rate controls the relative pressure and therefore the flow rate liquid outlet. In one embodiment, these devices are arranged in posts provided with fans.

Description

The present invention relates to a device for delivering a liquid with

  a low controlled flow rate and an installation making use of said device The diffusion of perfume in a volume of air is a delicate operation which implies that two operations are carried out, the metering of said perfume and its diffusion in the volume of air to be treated . The perfumes are generally in liquid form. Their diffusion in the atmosphere involves a preliminary phase change by vaporization, the perfume passing from the liquid form to the gaseous form. Two vaporization modes are generally used, vaporization from droplets (Sprays) or vaporization from porous media previously soaked with the liquid to be diffused. This last mode

  Spray is used for continuous-use room diffusers.

  Most continuous-use room diffusers use porous diffusers

  pre impregnated or continuously soaked with a wick or a porous medium.

  In virtually all existing systems, the rate of evaporation is very dependent on temperature. Moreover, the constituents of the perfume or more generally of the product to be evaporated evaporate according to Raoult's law, the most

  volatiles leaving the porous medium proportionally faster than the less volatile ones.

  As a result, the evaporation surface is rapidly depleted of volatile agents and the olfactory sensation decreases over time. It can be said that the evaporation process conditions the flow of evaporated perfume and that the constitution of this perfume is a function of the history it has undergone and of external physical agents such as

  air velocity around the evaporation zone, and its temperature.

  On the contrary, if a known liquid flow rate can be provided, the composition of the evaporated gas is independent of the temperature, the wind and any other characteristic of the receiving medium. In the case of perfumes, it is therefore possible to obtain an olfactory impression, itself controlled, and possibly constant if the liquid flow rate is constant. The present invention relates to a device for dosing a liquid initially contained in a reservoir, said liquid having a tendency to escape from said reservoir under the effect of an external gravity or mechanical force. The tank, possibly divided into two parts by a flexible membrane, can be emptied if it enters a gas that will usually be air. This air flow is controlled by a pressure drop in which the flow is laminar, so that it can be made as low as you want. This laminar pressure drop can be carried out in the form of a capillary tube or a porous medium whose pores are of very small size. The particular provisions relating to the tank and its accessories make it possible to control the flow of liquid that escapes by maintaining almost constant pressure drop on the air, or, equivalently, the difference in

  pressure on either side of said laminar flow pressure drop.

  Furthermore, the invention relates to aerodynamic installations for dispersing the vapors of the liquid thus measured to perform an atmosphere treatment in particular situations. In one version of the invention, the vapors

  from the evaporation of the liquid are convected by means of a fan.

  In another version, one or more dosers are placed in the same chamber consisting of a hollow post, said post being provided with calibrated orifices regularly spaced so that the flow of perfume from this post is driven by the wind and forms a dihedron at a distance from said pole. The association of such poles placed at regular intervals along a line in a plane makes it possible to introduce perfume in a homogeneous manner into the aerodynamic wake of this surface. More generally, a perfume can be uniformly introduced into a moving fluid medium by placing perfume diffusers at regular intervals following the

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  vertical and horizontal directions in a surface that will preferably be a plane

or a cylinder.

  To achieve these aims the device for delivering a controlled flow rate of less than 2 liters per day of a liquid is characterized in that it comprises - a closed container containing said liquid, said container being provided with a liquid outlet orifice, means for applying to said liquid a force that tends to cause said liquid to exit through said orifice; means for creating in said container a relative pressure in relation to the outlet of said liquid, said relative pressure opposing the effect of said force on said liquid; and means capable of creating, over at least a portion of their length, a laminar flow whose maximum flow rate is 1 ml / h / Pa for controlling the flow rate of entry of a gas into said container, whereby the flow rate of The gas inlet controls the relative pressure and thus the liquid outlet flow rate. The gas passage section is in all points less than 1 mm 2. She is of

  preferably less than 0.2 mm 2.

  To achieve such a laminar inlet, several methods can be envisaged, among which the following: - The implementation of one or more capillary tubes placed in series or in parallel. - The implementation of long channels resulting from the cooperation between a microgroove spiral shape and a flat surface. this technique is

  known and has, among other things, the subject of the patent 94909146.6 of March 4, 1994.

  - The implementation of porous media. These porous media are currently produced in the form of membranes or massive media consisting of packed or agglomerated particles. They are often used in the industry for their filtration capacity. In this case, the equivalent diameter of the pores of the

  porous medium will always be less than 1 micron.

  Other features and advantages of the present invention will become more apparent

  reading the following description of the principles and several modes of implementation

  of the invention given by way of non-limiting examples. The description refers to

  to the appended figures in which: FIG. 1a illustrates an embodiment of a liquid diffuser in

  which the air flow control is carried out by means of a porous plug.

  FIG. 1b shows the same apparatus in which the air flow control is

  performed by means of a porous membrane.

  - Figure 2a shows a diffuser in which the force for discharging the liquid is given by a spring acting on a bag initially filled with said liquid, the control of the air flow being through a porous membrane. FIG. 2b shows a liquid diffuser in which the force intended to make the liquid escape is given by a spring acting on an initially empty bag which fills up little by little with gas and thus pushes the liquid, the flow control air through a porous membrane. The diffuser is provided with a reservoir in the form of a tube formed between two cooperating parts which makes it possible to avoid a too rapid emptying of the liquid reservoir in case of alternating variations

temperature.

  FIG. 2c represents a diffuser similar to that of FIG. 2b in which the liquid passes through a calibrated laminar pressure drop allowing partial compensation of the influence on the flow of air and therefore of the liquid of the variation of viscosity of the air with the temperature. In this figure, the reservoir containing the liquid is formed of a flexible pouch. FIG. 3 gives a particular embodiment of the gravitational liquid diffusion device in which the main constituents are produced by

  thermoforming from a single sheet of plastic material.

  - Figure 4 shows a constant flow diffuser placed in a tube with holes in which a fan can create a permanent air flow that helps to

  the evaporation of the perfume and allows its injection into the medium to be treated.

  FIG. 5a shows the section of a perforated post into which several constant flow diffusers are introduced, this post being subjected to drafts which

  allow the training of the product broadcast.

  FIGS. 5b and 5c show a top view and a side view of a set of

  poles placed in line in the smelly wake of a sewage treatment plant.

  The set of diffusion holes thus constituted makes it possible to regularly seed said wake, and, by means of the implementation of suitable perfumes, it is thus possible to

mask or reduce odors.

  FIG. 6 shows a motorized device for diffusing a liquid in which the air inlet is controlled by a microporous element in the form of a membrane and in which the liquid outlet is itself controlled by a

  microporous membrane pre-soaked with the liquid to be diffused.

  FIG. 7 shows an assembly in which the microporous air inlet membrane is protected from external dust and from contact with the fingers by a

  second porous membrane of much greater porosity.

  In Figure la is shown a reservoir 3 which contains a liquid 1 covered with an air atmosphere 2. The reservoir is provided with a tube 7 which is immersed in a reservoir 8 containing liquid to the dimension 9. The reservoir is also provided internally with a dip tube 5 whose end is at the dimension 6. The difference in height Ah between the dimension 6 and the dimension 9 makes the pressure at point 6 is lower than the atmospheric pressure of a value equal to: Ap = pgAh This pressure difference is independent of the height of the liquid in the tank above the dimension 6. The tank is, moreover, provided with an air inlet according to the arrow F 1 This air passes through a laminar pressure drop formed of a porous medium 4 whose pore size is such that the air flow, illustrated by the bubbles 11 escaping from the tip 6 of the tube 5, is very small. . The air entering the tank flushes an equivalent amount of liquid. It overflows in the form of drops 12 of the tank 8, spreads in the cup 13, is sucked back by the cellulose wadding 14

  from which it can evaporate.

  In a particular application, the height Ah is equal to 40 mm, the height of the tank in its maximum diameter zone is 60 mm and the diameter is also 60 mm. The pressure drop of the porous medium is characterized by an air flow rate equal to 0.012 microliter per minute at 70 000 Pa. With such an apparatus, the flow of liquid escaping from the reservoir is approximately 100 milliliters per month.

  well suited to the dosage of perfumes.

  FIG. 1b represents the same application in which the porous medium block 4 is replaced by a membrane 15 whose pressure drop is also characterized by an air flow equal to 0.012 microliter per minute under a pressure difference of

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  000 Pa. More generally, the air flow is less than 1 milliliter per hour under

  a pressure difference of 1 Pa and preferably less than 1 liter per month.

  These provisions make it easy to obtain a liquid flow rate of less than 2 liters / day. In the case of producing perfume diffusers, the laminar pressure loss will preferably be adapted to control a liquid outlet flow rate.

less than 20 ml / day.

  In other embodiments, the porous pressure drop may be replaced by a long and small diameter pipe, for example by a capillary tube of 120 micrometers in diameter and 5 m in length or any other

  obstruction seat of laminar flows of the same coefficients of loss of load.

  In particular, it is possible to use capillary tubes of very small diameter, such as those developed by the Dupont de Nemours Company for the treatment of water by

reverse osmosis.

  FIG. 2a shows a fluid dosing apparatus formed from the following elements, a reservoir in two parts 201 and 202 sealed together, a flexible pouch 203 containing the diffusion liquid 204, a plate 205 pressed by a spring 206 which presses the flexible bag 203 and tends to escape the liquid, a porous membrane 208 which limits the air intake. At the start of the apparatus the pocket is pierced by the tip 210 of the part 211 which is an integral part of the part 209 which in all the tank. The liquid therefore tends to release under the effect of the pressure due to the spring, but its flow is limited by the flow of air passing through the membrane 208. The liquid exiting the flexible bag enters the spiral channel 212 formed between the bottom of the part 209 is the cover of the reservoir 202, then in the helical channel 213 formed between the part 209 and the constituent part 201 of the reservoir, then reaches the cellulose wadding 214 that it soaks before evaporating in the atmosphere. The role of the spiral channel and helicoidal channel whose length is very large is to compensate for changes in temperature. As the temperature increases, the air in the reservoir tends to expand and thus push the liquid out of the pocket. In the absence of a channel, during successive increases and decreases in temperature, air would enter the pocket that would empty much faster than expected. The channel acts as a buffer and avoids this annoying phenomenon. In a situation where the channel is full of liquid, the dilation of the air forces the liquid to come out and to moisten the wadding. When the temperature decreases, the air retracts and the liquid in the channel tends to flow back to the reservoir. The volume of the channel must be greater than the variation of air volume. The channel thus acts as a buffer tank and prevents the return of air to the tank and its emptying too fast. An example of sizing can be as follows: The tank has a diameter of 50 mm and a height of 20 min. The steel spring is optimized so that it has 11 turns, its free length is 300 mm, its outside diameter 30 mmin and its wire diameter of 1 min. He presses the plate 205 with a nearly constant force of 20 N over its entire useful stroke. The pressure drop of the membrane will be characterized by a flow rate of 0.005 microliters / min under a pressure difference of 70 000 Pa. Under these conditions, the liquid contained in the pocket will flow in one month. The tubular reservoir formed of the spiral and the helix will, for its part, have a total length of 1.5 m and its section will be a square of 2 mm, so that its volume is 6 cm3. This makes it possible to compensate for temperature variations of

   C in the range of ordinary temperatures.

  In general, in order to obtain a flow rate of the regular liquid, preferably, the average diameter of the plate is at least equal to the useful stroke of the spring. Of

  more preferably, this ratio is greater than two.

  Figure 2b shows another embodiment of a motorized liquid diffuser by means of a spring. The liquid 225 is contained in a reservoir formed of two welded pieces 222 and 223. A flexible and deformable pouch 220 is placed in this reservoir 220 containing a spring 221 which tends to open it. Air is introduced so

  controlled through a porous membrane 235 and seat of a laminar flow.

  The volume of air 224 tends to increase and expels the liquid 225 contained in the tank. The startup of the system is done in this example by destroying a

  seal 227 by means of the tip 228 of the part 226 which surrounds the reservoir.

  As in the previous example, the liquid escapes through the clearance 234 existing between the piece 226 and the piece 223 of the tank, then in the propeller 229 machined in the piece 223 which forms with the piece 226 a long duct and of small section. The liquid then escapes through the opening 230 and wets the wadding 233 which is held between the parts 226 and 232, the latter being perforated to allow evaporation of the liquid. It will be noted that with this design, it is possible to envisage using a flexible reservoir instead of the assembly formed of the pieces 222 and

223.

  FIG. 2c shows another embodiment of a motorized perfume diffuser by means of a spring 251, in which the liquid is contained in a flexible pouch 254. We find some of the elements of the previous figure, the flexible pouch 250 which contains the air coming from the atmosphere through the porous membrane 253, the spring which makes it possible to put the pouch 250 in depression. Under the effect of that

  depression, the bag 250 absorbs air through the membrane 253 and inflates.

  The liquid contained in the pocket 255 is thus ejected little by little as the bag 250 is inflated. The liquid bag 255 is itself provided in this example with a porous membrane 256 through which the ejected liquid passes, this membrane generating a pressure drop. It is well known that the viscosity of the liquids decreases with temperature and, on the contrary, that of the gases increases with said temperature. The pressure losses of the two porous membranes 253 and 256 placed respectively on the air flow and the water flow can be adjusted so that the liquid flow is almost independent of the temperature in a temperature range. given. These two membranes are the seat of laminar flows characterized in that the pressure losses they generate are proportional to the flow rates of the fluids passing through them and coefficients k1 and k2 characteristic of their geometry. The calculation making it possible to define the relative value of these pressure drop coefficients for a given temperature range and a given liquid-gas torque is easily realized by those skilled in the art. At the outlet of the porous membrane 256, the liquid soaks the wadding 257 and evaporates through orifices pierced in the container 258. This container can

  possibly be carried out by thermoforming.

  FIG. 3 gives an embodiment of the gravity liquid diffuser in which the constituent parts are produced by thermoforming, which makes it possible to lower the production costs dramatically. The apparatus is essentially made from two thermoformed plastic plates, the plate 301 which is the most worked in the example and the plate 302 which is substantially flat. These two plates are welded together along the weld line 315. The reservoir is

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  303 which contains the diffusion liquid 304 surmounted by the atmosphere 305. This reservoir is provided with an extension tube 306 which communicates with the temperature compensating tank 308 through the pipe 307. The level 309 in the reservoir in normal operation is established so that the liquid overflows through the opening 309 to create drops 314, said drops falling gravitarily on the porous medium 310 which absorbs and allows the evaporation of the liquid. The air is introduced through the porous membrane 311, passes through the tube 316 which opens into the reservoir 303 through the tube 312 near its bottom. Said air enters this reservoir 303 in the form of bubbles 313. There is therefore a mechanism exactly identical to that illustrated in FIG. 1. The reservoir 308 makes it possible to compensate for temperature variations and to avoid inadvertent re-entry of air into the chamber. 303 tank under the effect of temperature changes causing the expansion or narrowing of the air volume 305. The characteristic dimensions of a device of this type can be similar to those of the device described in Figure 1. Only change the embodiments, the principle described in FIG.

  very significant gains on the cost price.

  Preferably, the volume of the tank 8 is less than 20% of the volume of the container 2 and the volume of the tank 308, below the pouring hole 309 is less than% of the volume of the container 303. More preferably, the ratio is less than at 10%. In addition, the area of the cross section (or horizontal) of the outlet tube 7 or 306,

  307, is less than 1 / 5th of the area of the horizontal section of the container 2 or 303.

  In order to improve the diffusion of the gases resulting from the vaporization of the liquids in the atmosphere 400 to be treated, it is desirable to use them in such a way that

  mixing between said gases and the medium to be treated is as intimate as possible.

  Figure 4 gives an example of an apparatus for improving the homogeneity of said mixture. A constant-flow liquid diffuser 401 is used which moistens a wadding 402 from which the liquid evaporates. Said diffuser 401 is placed in a tube 403 pierced with openings 404 and 405 respectively allowing the entry and exit of the air coming from the atmosphere 400. This gas inlet and outlet

  is provided by a fan 408 which creates an air flow according to the arrows F1, F2 and F3.

  In certain applications requiring the implementation of higher rates, it will be possible to set up a plurality of diffusers in the same tube. FIG. 5 gives an example of implementation of diffusers 501 for injecting vapors in an atmosphere 503 into movement according arrows F1 characterized in that the diffusers are placed in hollow posts 500, shown in Figure 5a, placed in a regular manner in the wake of the medium, usually smelly, to be treated. Thus, a real wall of odors is set up which allows an intimate mixture of the smelly wake, of which the turbulent puffs 505 have an external limit 506, with the wakes 507 coming from the orifices 502 pierced in the posts. All these wakes join at 508, a position from which it is certain that any volume of malodorous gas has been mixed with the process gas. However, practically, the mixture does not become sufficiently homogeneous at a distance twice that existing between the first point of junction of the wakes from the poles and the pole surface itself. If this is the characteristic angle of the opening of the plumes and I the distance between two posts, this minimal distance L is equal to:

L = 4 I tg-

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  Other arrangements of the perfume emitters can be considered, but the solution of using poles is particularly interesting because it allows to put the odor diffusers away from the weather by using a

simple and modular structure.

  Microporous membranes are known which are used to filter liquids or gases. these membranes are shaped to pass a sufficient flow of fluid while retaining the impurities of said fluid. These membranes are, for example, pierced by heavy ions accelerated by a high energy cyclotron. This patented "cyclopore" process marketed by the company Whatmann allows a fairly fine control of pore diameters, their length and their surface density. These membranes are marketed by this company to serve for fine filtrations and separations. In general, separation and filtration specialists seek to

  increase the pore density to obtain the highest possible specific flow rate.

  According to the invention, the aim is to adjust the number of pores for a given surface or to adjust the surfaces to obtain, in both cases, a given number of pores whose total flow is governed by a laminar flow law or quasi-laminar, the flow of fluid being almost proportional to the pressure difference on either side of the membrane. Advantageously, the microporous membrane is attached to the body of the

device by welding or gluing.

  According to the invention, it has been demonstrated that these microporous filters could be defined to constitute the element of laminar pressure loss that can be used in the flow rate control devices according to the invention. More precisely, these microporous membranes for controlling an air flow q under a pressure difference Dp will have pore diameters D and pore lengths L, the total number of pores being n. The quantities n, D and L will be calculated using the following formula, in which m is the dynamic viscosity of the fluid: 7cD4 q = nap! 2D 128glL This type of porous medium will be particularly well adapted to the control of the flows

pure fluids.

  For example, to control an air flow rate of 100 ml per month at a pressure of 400 Pa, it will be possible to use a membrane having 2 107 orifices of 0.1 micron in diameter and of a length equal to 12 microns, the thickness of the standard cyclopore membrane. Actual membranes have some dispersion of pore diameters. Moreover, because of the very small size of the pores used, the formulas to be applied may be slightly different from the previous one, which should only be considered as a base

pre-dimensioning.

  For example, to ensure an air flow rate of 100 ml per month under a pressure difference of 400 Pa at 20 ° C., a porous membrane comprising 7 million channels 0.1 micron in diameter and with a length of 12 microns corresponding to the thickness of the membrane. Such a membrane is achievable by the cyclopore process which provides 600 million channels per cm2 as standard. We

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  would obtain an equivalent result with a membrane comprising 700 channels 1 micron in diameter and 12 microns in length. This same flow would pass in a channel 5 microns in diameter and 12 microns in length or in a Picoflow of a

  length of 5 m and an equivalent diameter of 120 microns.

  It can therefore be claimed that, in all cases, the porous media used in microdosing processes have pores with a diameter of less than 10 microns and

  whose number is between 100 and 1,000,000,000.

  It is impossible to pass liquid with a small pressure difference in very small pores because of the combined effects of wettability and surface tension. It is necessary to pre-wet the porous medium before using a pressure drop of this type to pass a liquid through a membrane

  whose two faces are in contact with the liquid.

  It is therefore necessary to give the means in an application of diffusion of liquid through such a membrane: - to wet the porous medium, to extract the gas contained in the reservoir in contact with the membrane, not to create gas parasitic during storage and use of degassing under the effect of temperature differences for example, - to maintain liquid in contact with both sides of the membrane during the

storage and use.

  The wetting of the porous medium would ideally be carried out after placing the membrane, for example by forcing the liquid to pass through it, because the welding or bonding with the membrane support could be of poor quality if the membrane is soaked. In FIG. 6, the essential elements of FIG. 2c relating to the spring-powered diffuser, the envelope formed of the welded parts 652 and 658, the air pocket 650, the liquid pocket 654 and the spring 651 are shown. air inlet porous membrane 653 is made of cyclopore material or equivalent welded to the air pocket 650. A porous membrane pre-soaked with liquid is also welded to a plate 660 itself welded to the pocket 654, so that that the liquid is forced to pass through this membrane to leave the pocket 254. On the other side of the membrane 656 relative to the pocket, there is arranged a small pocket of liquid 658 for keeping the membrane 656 always wet. The diffuser is started by piercing the pocket 658 by means of the tip 659. The liquid contained in the pocket 658 can then flow and wetting the diffusion wadding 657. The respective pressure losses of the two membranes are calculated in such a way that the flow rate is constant over a wide temperature range by compensating for viscosity variations, the viscosity of the gas

  increasing with temperature while that of the liquid decreases.

  Preferably, the liquid filling is carried out with a pre-degassed liquid or, at least, a liquid whose total pressure of dissolved gas is always lower than the atmospheric pressure whatever the temperature to which it is subjected. The operation

  Degassing is a known operation in chemical engineering and will not be described here.

  FIG. 7 shows a mounting of the microporous membrane 701 by welding on a wall 702. This microporous membrane is protected on one side by a second porous membrane 703 against dust, liquids and greases coming from contact with the fingers. Moreover, on the other side of the microporous membrane, a second hydrophobic membrane 704 has been arranged to protect it from possible liquid returns. this latter provision applies in

  particularly gravity liquid diffusers.

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Claims (24)

CLAIMS.   Device for delivering a controlled flow rate of less than 2 liters per day of a liquid, characterized in that it comprises: - a closed container containing said liquid, said container being provided with a liquid outlet orifice; means for applying to said liquid a force that tends to cause said liquid to exit through said orifice; means for creating in said container a relative pressure in relation to the outlet of said liquid, said relative pressure opposing the effect of said force on said liquid; and means capable of creating, over at least a part of their length, a laminar flow whose maximum flow coefficient is 1 ml / h / Pa for controlling the flow rate of entry of a gas into said container, whereby the gas inlet flow rate controls the relative pressure and therefore the output flow liquid.   2. Device according to claim 1, characterized in that said container is constituted by a rigid and sealed wall having a bottom, said outlet orifice being provided in said bottom so that the force applied to the liquid is the gravity and in that that the gas inlet control means is a microporous material element with a pore diameter of less than 1 micron, one side of which is in communication with a gas source and another face of which is in communication with the interior of the container , said microporous material creating said laminar flow of gas between said source and said   container, said gas being substantially insoluble in said liquid.   3. Device according to claim 2, characterized in that the second face of the microporous element is extended by a gas inlet pipe of which   the open end opens into said container near its bottom.   4. Device according to claim 3, characterized in that said outlet port is extended by an outlet pipe opening into a reservoir, the assembly consisting of the container, the outlet pipe and the reservoir forming a siphon, said reservoir being provided with a side wall provided with an outlet hole forming a weir, said outlet hole being arranged at a lower dimension than from the bottom of the container.   5. Device according to claim 4, characterized in that said outlet tubing has a cross section less than 1 / 5th of the mean horizontal section of said container. 6. Device according to claim 5, characterized in that said reservoir has a volume disposed below said outlet hole less than 20% of the volume of said container.   7. Device according to any one of claims 4 to 6 characterized in that   the walls of said container, said outlet pipe, said tank and said gas inlet pipe are constituted by sheets of plastics material of the form of the present invention, which are preformed to define said volumes and fixed between them, the element   microporous being fixed in an orifice of said leaves.   8. Device according to claim 7, characterized in that said gas inlet pipe is constituted by a volume in a wall of which said microporous element is fixed and by a pipe element connecting said volume to said   container near its bottom.   9. Device according to any one of claims 7 and 8, characterized in that   said sheets of material are weldable and thermoformable.   10. Device according to claim 1 characterized in that the liquid is contained in a deformable pocket on which a mechanical spring is supported by means of a plate, said pocket being disposed in said container, so that the liquid tends to to escape, the flow of liquid can be made only if the gas enters the tank to compensate for the liquid outlet. 11. Device according to claim 1 characterized in that the liquid is contained in said reservoir, the spring being placed in a deformable sealed pouch surrounded by the liquid, so that said pocket tends to open and fill with gas at through the loss of pressure, the deformation of   said pocket forcing the liquid to escape from said reservoir containing it.   12. Device according to any one of claims 10 and 11 characterized in that   that the liquid outlet takes place through a long tube that fills and empties under the effect of increases and decreases in ambient temperature, so that the buffer capacity thus constituted prevents a too rapid emptying of the liquid tank by air intake during the cooling sequences, thus avoiding an excessively rapid emptying of the liquid contained in said tank.   13. Device according to any one of claims 10 to 12 characterized in that   that the liquid outlet is effected through a calibrated laminar pressure loss intended to compensate for the variations in flow rate resulting from temperature variations by adjusting the laminar pressure loss on the gas and the laminar pressure loss on the liquid. such that the viscous effects due to the increase of the viscosity of the liquid and the decrease of the viscosity of the gas with the temperature within a temperature range fixed at advance.   14. Device according to claim 10 characterized in that the ratio between the equivalent diameter of said plate and the spring stroke is at least equal to 1.   15. Device according to any one of claims 10 to 14 characterized in that   that the means capable of creating a laminar flow comprise an element   with a microporous structure with a pore diameter less than 1 micron. I 1 2745559   16. Application of the device for delivering a liquid flow according to one of   any of claims I to 15 to the realization of a plant of   liquid diffusion, characterized in that said installation comprises: - a vertical hollow pole whose wall is pierced with a plurality) of orifices; and a plurality of liquid delivery devices according to one of   any of claims 1 to 15 disposed within said post to different levels.   17. Application according to claim 16, characterized in that said installation   further comprises fan means disposed in said post.   18. Application according to claim 17, characterized in that said installation   comprises a plurality of posts arranged in mesh.   19. Application of the liquid delivery device according to any one of   claims I to 15 to the realization of a liquid diffusion installation   characterized in that said installation comprises - a plurality of liquid delivery devices according to one   any of claims 1 to 15, and - Fan means.   20. Device according to any one of claims 2 to 9 and characterized in   that said microporous element is a thin membrane.   21. Device according to claim 20 characterized in that said membrane is in PET.   22. Device according to any one of claims 20 and 21 characterized in that   that the thickness of said membrane is less than 50 microns.   23. Device according to any one of claims 20 to 22 characterized in that   that the pore diameter is less than 10 microns.   24. Device according to any one of claims 20 to 23 characterized in that   that the number of pores in said membrane is between 100 and 1 billion.