WO2000068618A1

WO2000068618A1 - Steam generator

Info

Publication number: WO2000068618A1
Application number: PCT/BE2000/000051
Authority: WO
Inventors: Marc Michel Alexandre Brodsky
Original assignee: M. Brodsky S.P.R.L.
Priority date: 1999-05-06
Filing date: 2000-05-06
Publication date: 2000-11-16
Also published as: CA2373136A1; EP1177402A1; AU4529000A

Abstract

The invention concerns a steam generator comprising a water tank (24) and at least an ultrasound cell (26) in the tank (24) lower part. The cell is capable, when contacted with water, of forming a column or fountain of drops and droplets (32) above the water surface. An air stream is provided horizontally and selectively passing through said column base thereby driving the droplets towards an outlet for the finest droplets. The tank upper part contains the least fine droplets and is advantageously isolated from the lower part by a plate provided with a perforation allowing through the main jet of the fountain. The water coming from the fountain upper part is recirculated towards the tank (24).

Description

Steam generator

The present invention relates to a steam generator or humidifier, more particularly to ultrasound.

Various types of ultrasonic steam generator are known for producing non-condensing steam in the form of micro-droplets.

These devices consist of one or more ultrasonic cells (transducers vibrating at a frequency of +/- 1.7 MHz) placed at the bottom of a water tank. These cells produce a sort of fountain or mini-geyser from which the micro-droplets escape. The latter are carried away by a vertical air current produced by a fan in a chimney-shaped element.

These devices are however not of good performance and / or produce an unacceptable condensation, the smallest microdroplets (+/- 2 microns) not being well separated from the larger droplets which are able to condense and not to diffuse to evaporate after a few seconds.

These heavier droplets cannot remain in suspension in the air and when they fall they wet the device and the immediate surroundings of the humidifier. To avoid this phenomenon, the height of the chimney can be increased, which increases the size of the appliance. We can also add baffles, which causes condensation in the pipes and reduces the efficiency of the device. In addition, it is necessary to place a chimney above each transducer, which complicates the manufacture of devices comprising a high number of transducers.

According to the present invention, a more efficient device is proposed, which can be more compact and has a better yield.

This object is achieved by making the flow of air adopt a path horizontally crossing the column, more particularly the base of the column, of micro-droplets produced by the ultrasonic cell. This arrangement makes it possible to separate the droplets of larger diameter endowed with a greater kinetic energy and which can rise to a few centimeters, even a few tens of centimeters above the surface of the liquid.

The invention therefore provides a steam generator comprising a water tank and ultrasonic cells at the bottom of said tank, the cells being able, in contact with water, to form a column of drops and droplets above the surface of said water, characterized in that a stream of air selectively crosses the base of said column horizontally, thus carrying the finest droplets towards an outlet opening. The column is located in a chamber closed upwards, for example by a cover element covering the device. According to a preferred embodiment of the invention, the transducers are located at the base of a bell-shaped arrangement, that is to say without vertical outlet.

The air set in motion is brought to the base of said bell because, according to this arrangement, it can only descend along a separating wall descending from the upper face of the enclosure, for example formed by a cover element , wall forming an upwardly closed chamber, or bell, in which the fountains ("geysers") of the transducers produce the drops and droplets.

The separating wall may be integral with the cover and optionally formed in one piece with the latter, for example by molding. It can also be secured to the tank.

The air can only exit by following a horizontal path under the bell and by entraining the finest micro-droplets which do not have the kinetic energy necessary to go up in the bell. The larger droplets remain trapped in the bell and fall back into the tank. The air stream containing exclusively very fine droplets exits through an opening either at the top of the device, possibly screened, placed behind the bell, or through a side opening. The "mist" which leaves the apparatus is not wetting and 1 total evaporation is thus obtained with droplets remaining in suspension. The embodiment with lateral or front outlet is particularly advantageous from the point of view of space.

According to one embodiment, the air is captured by a fan and firstly circulates under the water tank, cooling the electronic elements of the ultrasonic transducers. These electronic elements therefore do not heat the water as in certain embodiments of the prior art.

The fan air inlet can be located under the device, above the device or on one of the side walls. These last two embodiments are preferred if the outlet is lateral.

According to a particularly preferred embodiment, a horizontal wall or plate having a perforation of small diameter is placed above each cell. These perforations are arranged so as to allow the jet of fountains to pass through said plate, the upper part of each fountain therefore being enclosed in an enclosure pe in the shape of a bell, situated above the surface of the water and so above the cells. The perforations will preferably be circular or elliptical. The air flow passes between the water surface and the plate, flush with the water with a minimum of turbulence and efficiently collects the smaller droplets which are preferably there. It can be postulated that these droplets are ejected at a very low speed and are of the order of 1 to 3 microns. An air current is thus provided which crosses the base of said column horizontally and selectively, thus carrying the finest droplets towards an outlet opening. The upper part of the fountain contains the least fine droplets and is advantageously isolated from the lower part by a plate provided with a perforation allowing the main jet of the fountain to pass.

The plate is preferably placed essentially horizontally a short distance above the water. It forms for example an enclosure open on the sides or provided with lateral openings allowing the water which gushes or condenses in the enclosure to fall back into the tank without accumulating there. These return paths interfere as little as possible with the air flow and the fountain (s). The plate can be tilted slightly to collect water from one side or the other, towards a lower lateral opening communicating with the main tank. The perforations allowing the upper part of the fountains to pass can have raised edges to prevent any return by these perforations of the water formed in the enclosure and flowing on the upper face of the perforated plate.

It will be understood that the larger drops rise via the perforations made above the cells and are captured in the bell. This device considerably improves the separation between the droplets of a few tens of microns and the microdroplets of 1 to 2 microns. This makes it possible to produce a very dry mist ("non-wetting" humidity) and a very compact device by limiting the distance between the cells and the outlet of the device to a few centimeters and the height to less than 15 cm.

The perforations preferably have a diameter between 8 and 15 mm and the plate is advantageously at a height between 15 and 40 mm, preferably around 30 mm for a length which will be for example 60 mm.

This embodiment is particularly suitable for the production of compact devices, in particular of low height, which can be inserted in air-conditioned enclosures, refrigerated cabinets, ovens, air conditioning and / or heating ducts or in fan coil units.

The invention will be better understood on examining the drawings presented by way of example only in which:

- fig. 1 represents a device according to the prior art,

- fig. 2 schematically shows in section an example of a device proposed by the invention,

- fig. 3 illustrates the path of the air in the device of FIG. 2

- fig. 4 illustrates another embodiment with lateral steam outlet - FIG. 5 illustrates a variant of FIG. 4 where the air inlet of the fan is located on a side face. - figs. 6a to 6d illustrate an example of arrangement of the various elements constituting a device according to the invention

- fig. 7 shows an improved device comprising a perforated horizontal plate.

In fig. 1 illustrates a schematic diagram of an example of a conventional humidifier with a water tank 1 maintained at a constant level, eg at +/- 45 mm in height above the surface of one or more transducers 2 which vibrate each producing a fountain 5 from which escape both fine desirable droplets and larger unwanted drops. The tank is pressurized by a fan 3 and the air can only exit through the chimney 4 causing the passage of very fine droplets in suspension but also a non-negligible part of the largest drops.

Fig. 2 illustrates in section a device according to the invention consisting of several removable parts, slightly disassembled, ie a grid 20, a cover element 21 with an upper opening 22 on which the grid 20 fits and a lower opening 23, a reservoir 24, a separator or deflector plate 25 secured either to the cover or to the reservoir. The bottom of the tank is provided with one or more transducers 26, and an external enclosure 27 supporting the tank, the cover and the grid, and comprising the fan 28 and the electronic elements 29. For example, the transducers or cells 26 associated with generator 29 can operate at 1700 KHz. The cell disc can have a diameter of 17 mm. A NB-595-095 Ultrasonic Humidifier cell from TDK may be suitable.

Fig. 3 illustrates the path of the air in the device according to the invention of FIG. 2, the reservoir 24 being partially filled with water 30. Under the effect of the fan 28, the air enters through an opening 31 in the bottom of the enclosure, passes under part of the reservoir and of the electronic elements, rises along an external face of a side wall of the reservoir to descend between the corresponding external face and an internal wall 25. The deflector or separator 25 imposes on the air flow a subsequent essentially horizontal trajectory above the surface of the water in the area where the transducer (s) 26 cause the formation of one or more columns 32 of micro-droplets. The laminar flow scans only the base of the geysers, which, moreover, in known manner, are slightly inclined, inclination caused by the inclination of the transducers.

Fig. 4 is a perspective view of another embodiment of the invention. The device is shown cut along a plane perpendicular to the walls 47 of the external enclosure. We distinguish the walls 41 of the bowl 44 as well as the water level 43. The air flow represented by a large arrow F carries the micro-droplets towards a wide slot outlet 45. The cylindrical elements 48 are closed towards the top and surround the geysers, and are located above the transducers 42. The fan 49 is placed on the upper face of the external enclosure. Fig. 5 shows an identical variant of the device according to Figure 4. The fan is placed on a side face which allows its positioning in even smaller spaces. The laminar air flow enters by the vacuum cleaner in the enclosure passes above the rim of the water tank, shaves off the water and the base of the geysers by taking away the micro-droplets, returns to the opposite rim of the tank water and leaves the enclosure through a slit.

FIGS. 6a to 6d illustrate a configuration of the elements of a device according to the invention with three cells in which the fan 49 is located on a side wall of the enclosure 47. FIG. 6a is a rear perspective view, FIG. 6b a top view, FIG. 6c a side view and FIG. 6d a rear view. In FIG. 6b, one can distinguish the filling solenoid valve 60, the cells (transducers) 42, the level control 64 and the lateral outlet opening 45 (slightly oblique with respect to the vertical). Fig. 6c is a side view showing inter alia the water tank 44 and the generator 29. In FIG. 6d, a further distinction is made between the water inlet 61, the 48VAC socket with fuse and a switch 63.

Fig. 7 schematically represents a device comprising a horizontal plate 70 comprising two openings at 71. This plate thus forms an enclosure 72 (shown separately in perspective) open laterally and disposed above the surface of the water so that it contains the upper part of the two fountains 32. The water formed inside The enclosure can return to the main tank 73 via the two open sides (arrow A), without disturbing the fountains 32 and the air flow 74.

Fig. 8 corresponds to the device of FIG. 3 in which the principle illustrated in FIG. 7. The deflector 25 becomes one of the walls of the enclosure 72 and forms the latter with the plate 70, an angle iron 76 and the cover element 21.

Finally, the advantages of the configuration proposed by the invention will be appreciated more on examining the data given below:

Devices containing two transducers (nebulizers): efficiency without separator with separator improvement experience 1 96 cl / h 104 cl / h 8%

2 96 cl / h 108 cl / h 8% 3 88 cl / h 96 cl / h 9%

Devices containing three transducers (nebulizers) efficiency without separator with separator improvement of experience 1 1 1 11 155 ccll // hh 1 14 400 ccll // hh 27%

2,110 cl / h 145 cl / h 31%

The following table relates to a variant where the device has a horizontal plate of 60 mm extending above the water level and comprising two 12 mm perforations above two cells. For three experiments, we compare yields and quality steam depending on the distance between the plate and the water level. Test A is carried out with a standard device without a perforated horizontal plate.

Bl B2 B3 B4

cl / h 104 82 110 106 30 cl / h 118 88 114 110 32 cl / h 122 80 115 109

height 25 35 30 20

(mm)

result wet dry wet dry dry

The B3 test (H = 30 mm) reveals the best performance: for a slightly lower yield, a completely dry vapor is produced. The drop in yield is explained by the fact that no more large drops having a high weight are released.

Claims

ι. Steam generator comprising a water tank or an aqueous solution and at least one ultrasonic cell at the bottom of said tank, the cell being able, in contact with water, to form a column or fountain of drops and droplets at the above the surface of said water, characterized in that a stream of air passes horizontally through the base of said column, thus carrying the finest droplets towards an outlet opening.

2. Generator according to claim 1, characterized in that the column is located in a closed space at the top.

3. Generator according to any one of the preceding claims, characterized in that the air current descends along an external face of a deflecting wall present in said space, before passing horizontally through the base of the column.

4. Generator according to any one of the preceding claims, characterized in that the column or columns of drops and droplets pass through a wall, the upper part of the column or columns thus being enclosed in an enclosure comprising lateral openings to allow water forming there to join the reservoir.

5. Generator according to claim 4 wherein the wall is essentially horizontal.

6. Generator according to claim 4 wherein the wall is inclined.

7. Generator according to any one of the preceding claims, characterized in that the air stream cools the electronic components located under the water tank beforehand.

8. Generator according to any one of the preceding claims, in which the fan, and therefore the air inlet, is located on a lateral face of the enclosure.

9. Generator according to any one of claims 1 to 5 wherein the fan, and therefore the air inlet, is located on the upper face of the enclosure.

ιo. Generator according to any of claims 1 to 9 wherein the vapor outlet opening is located on a side face.

11. Generator according to any one of claims 1 to 10 in which the air stream consists of a single, unitary flow.

12. Generator according to any one of the preceding claims, characterized in that the water comprises ingredients to diffuse with the droplets.

13. Steam generator comprising a water tank and at least one ultrasonic cell at the bottom of said tank, the cell being able, in contact with water, to form a column or fountain of drops and droplets above the surface of said water, characterized in that a means is provided for isolating the upper part of the fountains, the resulting water being recycled into the tank.

14. Steam generator comprising a liquid reservoir, optionally comprising ingredients to be diffused, and at least one ultrasonic cell at the bottom of said reservoir, the cell being able, in contact with the liquid, to form a column or fountain of drops and droplets above the surface of said liquid, characterized in that a means is provided for selectively entraining by a gas flow the droplets located at the lower part of the fountains.

15. Generator according to the preceding claim characterized in that the liquid is water.

16. Generator according to the preceding claim characterized in that the gas flow is an air stream.

17. Generator according to claim 1, characterized in that the upper part of the column is located in a cylinder closed upwards.

18. Generator according to claim 3 characterized in that the wall is opposite a lateral opening.

19. A method of generating water vapor with droplets of dimension less than four microns characterized in that water is subjected to an ultrasonic vibration to produce a fountain of droplets, the droplets being at the bottom of the fountain being selectively harvested and disseminated.