Method And A Device For Ventilation And Airborne Decontamination By Mixing Using Blow And Suction Flows Attached By The Coanda Effect

Abstract

A device (101) for airborne decontamination of a room (3) by mixing using a blown jet (19) and a suction flow (21) that are attached by the Coanda effect (C). Vertical trunk means (103) have a bottom suction end (104) and a top blow end (105). Drive means (106) set the air (A) into motion inside and outside the trunk means. An intake nozzle (118) provides a vertical suction surface (Sa) serving to suck in the air (A) as a suction stream (55) parallel to the floor (6) and attached thereto by the Coanda effect (C). A blow nozzle (129) using the surface effect at the ceiling (20) presents a frontal porous blow surface (Ss). It produces a primary jet (19) of air that is attached to the ceiling (20) by the Coanda effect (C). Decontamination means (127) decontaminate the air (A). The effective area (Sae) of the suction surface (Sa) is less than the effective area (Sse) of the blow surface (Ss). This serves to eliminate the “interfering shunt air flow” that is usually associated with attached air blow ventilation systems.

Description

TECHNICAL FIELD OF THE INVENTION

The present invention relates to methods and devices for ventilating and airborne decontamination for the purpose of reducing the quantities of contaminating particles suspended in the air of a room, and of the type operating:

by mixing;

with two Coanda effects;

using a blown primary jet attached to the ceiling; and

a suction flow attached to the floor.

STATE OF THE PRIOR ART

Traditionally, air conditioning methods are technically classified depending on the way in which air is distributed within the treated room. The methods of air conditioning a room can thus be classified as follows:

ventilation by air piston displacement using a one-way flow;

ventilation by air displacement using thermal effect stratification;

ventilation by zone;

ventilation by mixing; and

ventilation by localized jet.

In ventilation vocabulary, a “primary air jet” is air that has previously conditioned (cooled, heated, decontaminated, humidified, dehumidified, . . . ), that is introduced into a room via a blow outlet such as a grille, a perforated panel, a diffusing ceiling, . . . . The term “total air” is used for the mixture between the primary air introduced into the room and the air of the room that is progressively entrained by the primary air and mixed therewith.

In the strategy of ventilation by air piston displacement, also known as one-way flow, or as “laminar flow rooms”, air is moved by a one-way primary air jet occupying the entire section of the room. The entire section of one wall of the room is used, generally the ceiling or sometimes one of the side walls, as a surface for blowing the primary air flow into the room. The air is blown in at a speed that is sufficient to pass through the room in parallel streams heading towards the opposite wall (generally the floor), which is porous so as to act as a suction surface. It is also common practice to take up the air through suction wall grilles installed close to the floor at the bottoms of the walls. Laminar flows operate using the “piston” principle. The primary air flow acts like a syringe to push back the contaminated air which is extracted from the room. “Laminar” flow rooms are used for achieving very low concentrations of contaminants. The air that is removed is taken up by an air treatment unit associated with the building, where it is decontaminated by being filtered and where it is mixed with new air. Thereafter it is blown back into the inside of the room through the flow surface (generally the ceiling) which is fitted with high-efficiency particulate air (HEPA) filters. The flow velocity is substantially uniform over the entire section of the room, reaching a value in the range 0.3 meters per second (m/s) to 0.5 m/s over the entire room that is to be protected. The blow and suction surfaces are situated:

• • either over opposite walls (perforated ceiling and floor);
  • or over perpendicular walls (ceiling with bottom side take-up grilles);
  • but never over the same wall.

The amount of air blown in a laminar flow represents 10 to 100 times the amount of the air blown by a mixing ventilation device with a turbulent flow or a device for moving air by thermal effect stratification. In addition, the entire ceiling needs to be fitted with a wall of HEPA filters. Devices for ventilation by air piston displacement (laminar flow) present:

an investment cost that is an order of magnitude greater; and

an energy cost that is about 10 times greater than that of mixing ventilation devices (turbulent flow rooms) or devices in which air is displaced by thermal effect stratification.

In addition, their structure comprising an entire blow wall (ceiling or wall) makes it impossible for them to be implemented in the form of a mobile system. Ventilation devices using air piston displacement are used solely in decontamination and ultraclean applications and not at all for air conditioning purposes for which they are much too expensive.

In the ventilation strategy making use of air displacement by thermal effect stratification, one or more diffusers of low-temperature air (cool air) are placed on the floor or close to the floor. This method operates by an air density difference within the room. The level of the “new” cool primary air that is introduced via the bottom, and that is denser than ambient air, acts progressively to push up the ambient air (which is warmer and floats on the cool air). The stratification strategy is less expensive than the piston strategy. Its purpose is mainly to ensure that the occupants of the room are at a comfortable temperature. Unfortunately, it is very sensitive to temperature disturbances, and it is not very effective in providing airborne decontamination (in particular of bacteria or fungi). In addition, the diffusers it uses are bulky and require significant infrastructure work at floor level. They cannot be made in the form of a mobile system. Devices for ventilation by displacing air by thermal effect stratification are used essentially in air conditioning applications.

In the zone ventilation strategy, the principle consists in treating certain zones or volumes of the room while the remainder of the room is left without any particular attention. As a general rule, it is accepted that the effectiveness of zone ventilation is better than that of ventilation by mixing in the ventilated zones. However, the low overall dilution of contaminants generally leads to overall decontamination of the room that is ineffective.

In a strategy of ventilation by mixing, air movement is provided mainly by the energy delivered by one or more primary air jets injected into the room. The theoretical objective of the strategy by mixing is to establish uniform conditions for the air inside the room. To do this, the primary air jet(s) injected into the room mix(es) with a large volume of ambient air. This phenomenon is known as “induction”. Ventilation by mixing is generally preferable for achieving better temperature comfort for the occupants. The term “occupation” zone is used to designate that portion of a room in which occupants are usually to be found. It is normally defined as the space extending from a surface that is 50 centimeters (cm) back from walls containing windows, 20 cm back from other walls, and extending up to 180 cm above the floor. The strategy of ventilation by mixing seeks to mix (as completely and as uniformly as possible) the primary air with the air already in the room, so that the impurities and contaminants in the room are not only attenuated by being diluted, but also, traditionally, are distributed uniformly. In the same way, it is desirable for the temperature in the room to be as uniform as possible in order to avoid discomfort for the occupants. Unfortunately, the dimensions of a room of reasonable size and the number of diffusers generally require the primary air jet(s) (cool air) to be injected at a speed that is faster than the speed acceptable for the occupants to be comfortable if they encounter a jet. Methods of ventilation by mixing can technically be subdivided into two sub-types:

ventilation by mixing using a free primary jet; and

ventilation by mixing by using a primary jet that is attached by the Coanda effect.

In methods of ventilation by mixing with a free primary jet, the primary air jet is injected into the room (usually vertically) through a diffuser that is generally situated in the central portion of a wall of the room (usually the ceiling). The primary air jet passes substantially perpendicularly through the envelope of the occupation zone. The movements of air in the room are almost disordered. The air jet reaches the occupants almost directly prior to any significant mixing with the air in the room. This often leads to temperature discomfort for the occupants.

In methods of ventilation by mixing with a primary jet that is attached using the Coanda effect, the primary air jet is injected into the room through a diffuser situated in a lateral region of a wall of the room (generally close to the ceiling), and in a direction that is substantially parallel and tangential to said wall of the room (generally the ceiling). As a result, the primary jet becomes deployed outside the occupation zone between the envelope of the occupation zone and the wall to which the jet is attached. The primary air jet thus travels along a long path and becomes mixed with a large quantity of ambient air prior to reaching the occupation zone. This disposition has the reputation of being thermally more comfortable for the occupants.

Following experiments performed for aeronautical purposes by the Romanian engineer Coanda in 1910, it has been known that when a jet of air is placed close enough to a surface, such as a ceiling for example, the jet of air tends to become attached to the surface and to continue its movement in contact therewith. This phenomenon is known as the Coanda effect or the surface effect. This is due to the fact that a jet of air tends to suck in ambient air in contact therewith in order to mix therewith (diffusion). However in the vicinity of a surface, no ambient air can be sucked in. This leads to a drop in pressure between the flow of air and the surface, thereby tending to cause the air jet to become attached to the surface.

The invention relates to a method of ventilation of the mixing type using a primary jet attached to the ceiling by the Coanda effect with air being extracted via a suction outlet in the form of a suction flow that is attached to the floor, likewise by the Coanda effect. In ventilation of this type, when the dimensions of the room make this possible, the air jet retains its effectiveness and reaches the wall opposite to the wall to which it was blown in, prior to being “diluted”. The total air flow then continues to move downwards along the opposite wall and then returns towards the suction outlet that is close to the floor. This obtains a kind of “envelopment” of the occupation zone by the flow of air going from the blow surface to the suction surface.

The initial experimental data on ventilation methods by mixing with a primary jet attached by the Coanda effect go back to 1939 when Baturin and Hanzhonkov demonstrated the phenomenon of the “reverse flow” deflected by the ceiling and the opposite wall towards the occupation zone. In their analyses of the shapes of the resulting air flow configurations, Baturin and Hanzhonkov concluded that the shapes of the air movements depended on the location of the blow grille (surface) while being influenced little by the configuration of the suction grille (surface) and the suction conditions. Subsequent theoretical work published by Nelson, Steward, Bromleys, and Gunes, gives information about the distribution of temperatures and velocities in the context of ventilation by mixing using an attached primary jet. Other theoretical work undertaken by Linke shows that there exists a maximum length for a room that can be ventilated properly using this principle. He demonstrated in particular that for linear primary jets “attached” to the ceiling, presenting a Reynolds number lying in the range 1,825 to 12,000, the length of the room must not exceed three times its width, if it is to be possible to establish an “enveloping” flow.

When the length of the room lies below this limit (<about 3 times its width), then a flow is obtained that envelops a single zone. A description of this phenomenon is given below with reference to FIG. 2. Such a room is said to be “short”.

Beyond this limit, the room is said to be “long”. The room becomes “partitioned” by the air flow. A first looped movement of air, similar to that obtained in a “short” room is constituted by a total air jet following the ceiling and then coming down vertically through the middle of the occupation zone and returning to the suction surface horizontally in the vicinity of the floor. Other vortexes or “closed” air loops develop between the first loop and the other end of the room, and they penetrate into the inside of the occupation zone. A description of this phenomenon can be seen below with reference to the description of FIG. 3.

Those published theoretical and experimental scientific studies show that:

when no particular conditions are imposed (conditions recommended by the invention concerning mean blow velocities and mean suction velocities are given below);

then, from a certain horizontal distance from the action side wall (the wall with the blow and suction surfaces) at a distance of about one height of the room, there appears a “sloping interfering shunt air flow”.

This “sloping interfering shunt air flow” tends to rise from the floor and pass through the occupation zone following an upward slope going towards the blow outlet. A description of this phenomenon is given below with reference to FIGS. 2 to 3.

The theoretical work published on the air flow schemes and air velocities in a room implementing a method of ventilation by mixing with an attached primary jet are concerned solely with thermal applications of ventilation. They seek to ensure that the velocities and temperatures in the occupation zone are as agreeable as possible for the occupants. The effect that is generally looked for in the prior art when implementing the method of ventilation by mixing with an attached primary jet is to lengthen the distance followed by the primary jet through the room prior to penetrating into the occupation zone. The person skilled in the art [represented by the community of scientists who have published the above-cited scientific works] has until now not been interested in the means that need to be implemented in order to optimize methods of ventilation by mixing using an attached primary jet for airborne decontamination, i.e. for reducing the quantity of contaminating particles in suspension within a room ventilated in this way. As mentioned above, the person skilled in the art has concentrated essentially on the thermal effects of ventilation and on the thermal comfort of the occupants, such that the “sloping interfering shunt air flow” tending to rise from the floor in a room ventilated by a primary jet attached to the ceiling by the Coanda effect leads to effects that are perceived as being somewhat “beneficial” in that context. For that person skilled in the art, such a “sloping interfering shunt air flow” enhances mixing and thus enhances the effectiveness of thermal ventilation. It will thus be understood that the person skilled in the art has made no attempt to reduce or eliminate the “sloping interfering shunt air flow”, even though its effects are essentially harmful in terms of airborne decontamination. In the usual frame of mind of the person skilled in the art, the problems of airborne contamination are:

either acute and solved by the strategy of ventilation by moving an air piston using a one-way flow, where the main drawback is expense;

or of minor importance and solved by conventional ventilation using mixing with a free primary jet, or by ventilation using mixing with an attached primary jet, with no account being taken of the “sloping interfering shunt air flow” (i.e. the negative consequences thereof are ignored);

or else very small, in which case conventional air purifiers making use of recycling are implemented, leading to decontamination that is not very effective such that the flows of interfering air loaded with contaminating particles coming from the floor and amplified by the presence of the “sloping interfering shunt air flow” are negligible.

The main object of the present invention is to make it possible:

to benefit from the intrinsic advantages recognized of the method of ventilation by an attached primary air jet and in particular the comfort it secures for the occupants and its costs of provision and operation that are lower than those of ventilation by displacement of an air piston in a one-way flow; and

while also being suitable for use in high-level decontamination and “ultraclean” applications.

To do this, the invention seeks to reduce (or eliminate) the effects of contaminated particles that have already settled on the floor being put back into upward motion, as usually occurs in rooms ventilated by mixing using an attached jet. The main object of the invention is thus to propose means for improving the method of ventilation by a primary jet attached to the ceiling by the Coanda effect, that seeks to reduce or eliminate the presence of the “sloping interfering shunt air flow” that has a tendency to rise from the floor. A secondary object of the invention is to propose a novel architecture for a mobile device for decontaminating air that is independent of the structure of the building, the device implementing a method of ventilation by means of an attached primary jet, but without a “sloping interfering shunt air flow”.

Mobile devices for decontaminating air that are independent of the structure of the building:

operate either on a principle of air dilution that is similar to that of rooms in which there is a turbulent flow;

or else act like purifiers, making use of ventilation of the localized jet type.

The remote technological background of the invention includes mobile air decontamination devices that suck air in and blow it out substantially horizontally at substantially the same height. Amongst this class of device, mention can be made of that described in U.S. Pat. No. 6,425,932 to Huehn, Deros, and Bourque. It can clearly be seen that that type of device cannot deliver a primary jet attached to the ceiling or make use of a sucked-in air flow that is attached to the floor.

In the remote technological background there are also mobile devices for decontaminating air that suck in air high up and blow air out low down.

U.S. Pat. No. 5,240,478 to Messina describes a HEPA filter purifier that sucks in air high up and blows it out low down.

U.S. Pat. No. 5,612,001 to Matschke describes a UV lamp purifier that sucks in air high up and blows it out low down.

U.S. Pat. No. 5,656,242 to Morrow and McLean describes a UV lamp purifier with an electrostatic filter that sucks in air high up and blows it out low down.

It will readily be understood that such purifiers sucking in air high up and blowing it out low down do not establish a primary air jet that is attached to the ceiling, and that because they blow air out low down they actively increase the setting up of contaminating interfering air flows coming from the floor.

Also in the remote prior art, there are mobile devices for decontaminating air that suck air in low down and blow it out high up, but too far away from the ceiling to enable the primary air jet to become attached to the ceiling by the Coanda effect.

U.S. Pat. No. 4,900,344 to Lansing describes a filter purifier provided with an intake nozzle of the bottom suction type at floor level and an upper blow nozzle at a low height without any attachment to the ceiling.

U.S. Pat. No. 5,997,619 to Knuth and Carey describes a UV lamp and filter purifier that sucks air in sideways low down and blows it out higher up at a low height, without attachment to the ceiling.

U.S. Pat. No. 6,001,145 to Hammes describes a filter purifier provided with an intake nozzle of the bottom suction type at floor level, and an upper blow nozzle at a low height, without the primary flow becoming attached to the ceiling.

U.S. Pat. No. 5,453,049 to Tillman and Smith describes a triangular section purifier provided with wide bottom suction through a HEPA filter and vertically-directed top delivery through a small opening at low height without the primary flux becoming attached to the ceiling.

U.S. Pat. No. 4,210,429 to Golstein describes a UV lamp and filter purifier with bottom lateral suction and top lateral blowing out at a low height without the primary flow being attached to the ceiling.

Those purifiers are of the type using a localized jet. None of those documents relate to a device that implements a primary air jet that is attached to the ceiling by the Coanda effect, nor does any of them describe means seeking to reduce or eliminate the “sloping interfering shunt air flow” between the floor and the ceiling.

Finally, there are mobile devices for decontaminating air that suck in air low down and blow out air high up close to the ceiling that could theoretically enable the primary air jet to become attached to the ceiling by the Coanda effect.

U.S. Pat. No. 5,290,330 to Tepper, Suchomski, and Mex describes an independent device for decontaminating air that is in the form of a vertical rectangular block with bottom suction and top delivery, both horizontal. Air is decontaminated by cylindrical filter cartridges disposed vertically inside the device. It is specified in that document that suction and delivery are separated vertically so as to ensure that air moves from the ceiling towards the floor. That document does not describe any attaching of an air jet to the ceiling by the Coanda effect nor does it describe any suction flow attached to the floor by the Coanda effect. Nor does that document describe the existence of a “sloping interfering shunt air flow” that tends to rise in a slope from the floor towards the ceiling. That document does not describe any means for avoiding that phenomenon. Finally, it can be seen from its drawings, that the suction and blow grilles are similar and have the same dimensions. As a result, the blow velocity and the suction velocity are substantially equal.

U.S. Pat. No. 5,225,167 to Wetzel describes an independent device for decontaminating air, which device is substantially in the form of a rectangular block, for mounting on the wall of a room and for decontaminating air by using UV lamps and HEPA filters. Air is sucked in through a grille from close to the floor, but nevertheless at a certain distance therefrom. Air is blown out close to the ceiling through a HEPA filter in the form of one-fourth of a cylinder. That document does not describe in any way ensuring that a jet of air is attached to the ceiling by the Coanda effect, nor does it describe a suction flow attached to the floor by the Coanda effect. The blow outlet of the HEPA filter being shaped in the form of one-fourth of a cylinder tends to cause the blown primary jet to slope towards the floor and is unfavorable to it becoming attached to the ceiling by the Coanda effect. The suction inlet which is deliberately placed at a distance from the floor likewise does not seek to facilitate establishing a suction flow that is attached to the floor by the Coanda effect. That document does not describe in any way the existence of a “sloping interfering shunt air flow” that tends to rise from the floor towards the ceiling. That document does not describe any means for avoiding that phenomenon. Finally, from the drawings, it can be seen that the suction and below grilles are of substantially the same dimensions. As a result, the suction and blow velocities are substantially equal.

U.S. Pat. No. 5,616,172 in Tuckerman, Russel, Knuth, and Carey constitutes the prior art that is closest to the invention. It describes a mobile and independent device for decontaminating air, which device is substantially in the form of an elongate rectangular block, and is placed vertically along a wall of a room that is to be treated. Air is decontaminated by UV lamps and HEPA filters. Air is sucked in from the floor via an intake nozzle of the suction type at floor level formed between the bottom of the device and the floor. The blow outlet is placed at the top on the device and blows vertically towards the ceiling. The shape of the device is described as being deliberately elongate in order to increase the distance between the suction grille and the blow grille so as to avoid “short circuits” between them. Fins are also described for placing on the blow grille in order to incline the primary jet that is blown from the top of the device towards the ceiling so that the primary jet is deployed along the ceiling. Although not stated clearly, it can therefore be assumed that the primary jet becomes attached to the ceiling by the Coanda effect. However, that document considers that the only means for avoiding the “shunt effect” between the suction and blow grilles consists in keeping them as far apart from each other as possible. That disposition is indeed necessary. However, as shown by the scientific documents mentioned above, and as shown by the explanations given below, that is not sufficient. Firstly, the document takes no account of the existence of a “sloping interfering shunt air flow” tending to rise from the floor (in the middle of the room) and pass through the occupation zone following a sloping path going upwards towards the blow outlet. That document is concerned only with the direct “shunt” between suction and blowing, which constitutes another problem.

That document therefore does not recommend any means relating:

to the ratio between suction velocity and blow velocity;

or to the ratio between the effective suction surface and the effective blow surface;

for the purpose of reducing and/or eliminating the “sloping interfering shunt air flow” that tends to rise from the middle of the floor towards the ceiling, in spite of the grilles being spaced apart.

The relative dimensions of the effective suction and blow surfaces are not specified. Unfortunately, without taking these particular precautions concerning shapes and flow velocities, the above-mentioned scientific works and the explanations given below demonstrate that the spacing between the blow and suction grilles is not sufficient for eliminating this phenomenon of the “sloping interfering shunt air flow”.

As mentioned above, the person skilled in the art considers that suction inlets are of little importance in the movement of the air and that they have an influence only on their immediate vicinity. It is shown below that the person skilled in the art is wrong on this point. As a result, the prior art has paid little attention to the influence of the shape and the location of suction inlets. It would appear that no scientific study has yet been undertaken on this topic.

It therefore appears that although the method of ventilation by mixing using a blown primary jet attached to the ceiling and a suction flow attached to the floor both by the Coanda effect is known and in widespread use for its thermal qualities in the field of air conditioning, its use is practically non-existent in the field of airborne decontamination because of the “sloping interfering shunt air flow” effect that it generates has not been solved in the prior art and because that effect degrades its decontamination performance.

SUMMARY OF THE INVENTION

The invention relates firstly to a method of ventilating a room by mixing using a blown primary jet attached to the ceiling, and a suction flow attached to the floor, both by the Coanda effect. More specifically, the invention relates to ventilation methods of the type in which a previously treated (heated, cooled, decontaminated, humidified, dehumidified, . . . ) jet of primary air is blown through a blow surface situated in register with a “treatment” side wall, close to the ceiling, and in a blow direction of incidence [average over the blow surface of the mean directions of the portions of the primary jet] oriented towards the ceiling (or parallel thereto) in such a manner as to attach said blown primary jet to the surface of the ceiling by the Coanda effect. Simultaneously, a vitiated air flow is sucked in at a flow rate that is equivalent to that of the primary jet, through a suction surface that is substantially vertical, placed in register with the same treatment side wall, in the vicinity of the floor of the room. In this way, it is ensured that air is sucked in from close to the floor along a suction stream that is substantially horizontal, being parallel and attached to the surface of the floor by the Coanda effect.

Empirical experiments and computer simulations have been performed by the inventors concerning ventilation systems using mixing by means of a blown primary jet attached to the ceiling and a suction flow attached to the floor, and these have shown that in a closed room, this type of ventilation leads to the appearance of a “sloping interfering shunt air flow” that tends to rise from the floor and pass through the occupation zone following an upward sloping path towards the blow outlet. This phenomenon is well described in the prior art and in the scientific papers cited above, and no solution has previously been found for eliminating it.

In its simplest form, the ventilation method of the invention consists in that in addition, the mean blow velocity (Vs) [average of the velocities of the primary air jet portions over the blow surface] is caused to be less than the mean suction velocity (Va) [average of the velocities of the air flow portions sucked in through the suction surface] [Vs<Va]. The inventors have found, by using computer models and by undertaking airflow measurements on independent devices for airborne decontamination of a room by implementing the method, that the said phenomenon of the “sloping interfering shunt air flow” is greatly attenuated or even eliminated, when the means of the invention are implemented.

BRIEF DESCRIPTION OF THE DRAWINGS AND THE FIGURES

FIG. 1 is a diagrammatic side view showing the phenomenon of aerosols settling and returning to suspension in a non-ventilated room.

FIG. 2 is a diagrammatic side view showing the distribution of air flows in a “short” room that is ventilated (without special precautions) by mixing using a blown primary jet attached to the ceiling and a suction flow attached to the floor (reproduced from Muller).

FIG. 3 is a diagrammatic side view showing the distribution of air flows in a “long” room ventilated (without special precautions) by mixing using a blown primary jet attached to the ceiling and a suction flow attached to the floor (reproduced from Muller).

FIG. 4a is a diagrammatic side view showing the air flow distribution obtained by computer simulation of a ventilation device (of the type shown in FIG. 2) operating in a room ventilated by mixing using a blown primary jet attached to the ceiling and a suction flow attached to the floor, in accordance with the teaching of the invention.

FIG. 4b is a diagrammatic perspective view showing the distribution of air flows obtained by computer stimulation of a ventilation device (of the type shown in FIG. 4a) operating in a room that is ventilated in accordance with the teaching of the invention, and showing in a detail view the effective suction and blow surfaces in the side wall for the FIG. 4a ventilation device in order to compare their relative sizes and also the mean suction and blow velocities.

FIG. 5a is a diagrammatic view of a portion of a moving air stream enabling the advantages implemented by the invention to be explained analytically and enabling the “sloping interference shunt air flow” to be eliminated.

FIG. 5b is a diagram showing the numerical simulation conditions for air flow diagrams obtained for a prototype of the independent device of the invention for airborne decontamination.

FIG. 5c is a table of values showing the results obtained by the numerical simulation calculation as shown in FIG. 5b.

FIG. 5d is a graph illustrating the results obtained as shown in FIG. 5c.

FIG. 6 is a diagrammatic side view of the air flows obtained by computer simulation of an independent decontamination device operating in a room in accordance with the teaching of the invention.

FIGS. 6a and 6b are a section view and a perspective view on a larger scale of the independent decontamination device of the invention.

FIG. 6c is a plan view showing the operation of the FIG. 6d device with a representation of the air flow lines that it generates horizontally.

FIG. 6d is a diagrammatic side view on a larger scale of the intake nozzle of the FIG. 6 independent decontamination device and showing its action on contaminating particles in suspension and particles located at floor level.

FIG. 6e is a diagrammatic perspective view showing the device of the invention together with its suction stream.

FIG. 7 is a diagrammatic side view showing the operating principle and the action on aerosols of a decontamination device operating in a room in accordance with the teaching of the invention.

FIGS. 8a and 8b are a section view and a perspective view of the blow nozzle of the FIG. 6 independent decontamination device and showing its position relative to the ceiling.

FIGS. 8c to 8h are side views showing the influence of adjusting the angle of incidence on the blowing performed by the device of the invention.

FIGS. 9a and 9b are side views showing the importance of a recommended variant of the invention relating to adjusting the suction and blow velocities.

FIG. 10a is a perspective view showing a detail of a second embodiment of the blow nozzle that is preferred in the invention.

FIG. 11 is a perspective view showing a detail of an embodiment of the intake nozzle that is preferred in the invention.

FIG. 12 is a perspective view showing an embodiment of vertical trunk means of reduced thickness that is preferred in the invention.

FIGS. 13a and 13b are perspective views showing an embodiment of vertical trunk means of adjustable height that is preferred in the invention.

FIGS. 14a and 14b are perspective views showing an embodiment of the FIG. 6 device having an auxiliary intake nozzle that is preferred in the invention.

FIGS. 15a and 15b are perspective views showing an embodiment of the FIG. 6 device having an extensible blow nozzle that is preferred in the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a conventional non-ventilated room (3). The ambient air (A) in the room (3) is filled with a multitude of contaminating particles (4) that can be considered as aerosols and that are attracted to the level of the floor (6) by a settling effect (5) under the action of their own weight and gravity. As a result, the contaminating particles (4) moving at a slow vertical settling velocity (5) will accumulate progressively in a fine bottom layer of air that is highly contaminated (Cc) and in contact with the floor (6). If an examination is made of the contaminating particles (4) contained in the room (3), the proportion of contaminating particles (4) present in the form of contaminating aerosols in suspension (4a) contained within the main volume of the room (3) is small, even though extremely dangerous for the occupants (1). Under the effect of gravity, of thermal convection movements coming from the floor (6), and of brownian movement, another proportion of the contaminating particles (4) accumulates in the form of a kind of very dense cloud of accumulated contaminating aerosols (4b) within the fine and highly-contaminated bottom layer of air (Cc). Within this fine and highly-contaminated bottom layer of air (Cc), the concentration of accumulated contaminating aerosols (4b) is asymptotic on coming closer to the floor (6). However the major fraction of contaminating particles (4) present in the room (3) are clinging particles (4c) which, after a long descent under the effect of gravity, cling to the floor (6) by means of Van der Waals' forces coming from interactions between the molecules they contain and the floor (6). The occupation zone (2) is the portion of the room (3) in which the occupants (1) are usually to be found. It is normally defined as the space extending from a surface set back by 50 centimeters (cm) from a wall that includes windows (51) and by 20 cm from other walls (140). It extends up to 180 cm from the floor (6).

When the occupants (1) move about in the room (3), they generate disturbances and turbulence (7) level with the floor (6) producing rising-type disturbance currents (8), that put back into suspension some of the accumulated contaminants (4b) and clinging particles (4c) located at floor level (6) in the bottom portion of the occupation zone (2). A phenomenon similar to that which leads to the development of powerful clouds of the cumulonimbus type in weather systems occurs on a smaller scale in the room (3). Light rays (53) from a light fitting (54) located in the ceiling (20) or coming through the window (51) lead to the floor (6) being heated in non-uniform manner. As a result, strong upward convection movements (57) are generated at floor level, thereby also putting back into suspension large amounts of some of the accumulated contaminating aerosols (4b) and the clinging particles (4c) located on the floor (6). These contaminating aerosols (4b, 4c) rise into the upper portions of the occupation zone (2) so as to reach the mouths of the occupants (1) and the zones (9) in which they breathe. As a result, these contaminating aerosols (4b, 4c) that are put back into suspension by these phenomena increase the concentration of contaminating aerosols (4a) in suspension. They increase the risk of being breathed in by the occupants (1) of the room (3), and consequently they increase the possibility of the occupants (1) suffering biocontamination from airborne biological agents that might develop into various types of disease (Aspergillose, Pneumopathies, . . . ).

The prior art makes widespread use of the method of ventilation by mixing using a blown primary jet (19) attached to the ceiling (20) and a suction flow (21) similarly attached to the floor (6), both by the Coanda effect (C). FIGS. 2 and 3 show how that prior art ventilation method is implemented using a built-in ventilation device (65) built into the building containing the room (3). In the prior art, a primary air jet (19) that has previously been treated by the built-in ventilation system (65) (i.e. heated, cooled, decontaminated, humidified, dehumidified, . . . ) is blown into the room (3) through a wall blow outlet (10) formed in the “treatment” first vertical wall (52) and opening out into the room (3) via a blow surface (Ss) situated in register with the treatment vertical wall (52), close to the ceiling (20). The primary air (19) is directed along a blow direction of incidence (Is) [the average over the blow surface (Ss) of the mean directions of the portions of the blown primary jet (19)] oriented towards the ceiling (20) (or commonly and as shown in FIGS. 2 and 3, parallel to the ceiling), so as to cause said blown primary jet (19) to become attached to the surface of the ceiling (20) by the Coanda effect (C). In parallel, a vitiated air flow (21) is sucked out at a flow rate equivalent to that of the primary jet (19) through a suction outlet (11) formed in the treatment vertical wall (52) and opening out into the room (3) through a substantially vertical suction surface (Sa) situated in register with the same treatment side wall (52), but in the vicinity of the floor (6) of the room (3). This ensures that air (A) is sucked out at the level of the floor (6) via a converging floor-level suction stream (55) that is substantially horizontal, and parallel to the surface of the floor (6), being attached thereto by the Coanda effect (C). The primary air jet (19) travels outside the occupation zone (2) between the envelope (63) of the occupation zone (2) and the surface to which the jet (19) is attached, as constituted by the ceiling (20). As a result, the primary air jet (19) travels along a long path and becomes mixed with a large quantity of ambient air (A) prior to reaching the occupation zone (2). This mixing leads to dilution between the vitiated air and the new air, leading to the air conditioning and the decontamination that is the purpose of the ventilation. This disposition has the reputation of being the most comfortable for the occupants (1) in terms of temperature. The built-in ventilation system (65) includes an external air treatment unit (73) that is generally situated on the roof of the building. The unit shown comprises a combined blow and suction assembly as is used in conventional manner in the field of recycling treatment of air. It comprises one or more fans of centrifugal or other type (67, 71) serving to set the air (A) into motion and to establish the air flow scheme, a heater unit (70), an air filter (69), and a mixer chest (68) for mixing recycled air with new outside air. The air treatment unit (73) is connected to a diffusion duct (72) opening out via the wall-mounted blow outlet (10), thus delivering the previously-treated primary jet (19) through the blow surface (Ss). The suction duct (66) connects the wall-mounting suction inlet (11) to the inlet of the air treatment unit (73) in order to exhaust the sucked-in flow (21) of vitiated and/or contaminated air from the room (3).

FIG. 2 shows the air flow scheme (reproduced from Muller) that is obtained in the prior art within a room (3a) that is said to be “short”, having length (L) that is less than about three times its width (l). This leads to a “looped” enveloping flow (B1). It can be seen that in the prior art (when no particular precaution is taken), there appears a “sloping interfering shunt air flow” (Fs) that rises from the floor (6) and crosses through the occupation zone (2) in sloping manner going upwards towards the blow surface (Fs). It will be understood that the “sloping interfering shunt air flow” (Fs) that rises from the floor (6) causes the accumulated and clinging contaminants (4b, 4c) at floor level to be put back into suspension as aerosols, with consequences similar to those described with reference to FIG. 1. On their upward path, these contaminants (4b, 4c) increase the content of aerosol contaminants in suspension (4a) in the ambient air (A) of the room (3). In the prior art, the risk of airborne biocontamination is thus increased in “short rooms” (3a) ventilated by attached jet mixing (19), because of the existence of this “sloping interfering shunt air flow” (Fs).

FIG. 3 shows the air flow scheme (adapted from Muller) obtained in the prior art within a so-called “long” room (3b) of length (L) greater than about three times its width (l). It can be seen that the “long” room (3b) becomes subdivided by air flows into a plurality of air zones (Z1, Z2, Z3, . . . ). A “closed” first loop of air (B1), similar to that obtained in “short” rooms as shown in FIG. 2, is established in the first zone (Z1). It is constituted by a blown primary air jet (19) following the ceiling (20), and it descends down an inclined branch (77) through the occupation zone (2) substantially in the middle portion of the “long” room (3b) prior to returning horizontally in the vicinity of the floor (6) to the suction surface (Sa). In addition to the fact that the “sloping interfering shunt air flow” (Fs) effect rising from the floor (6) is also present, other “closed” lops of air (B2, B3, . . . ) constituting vortices (12a, 12b) develop between the first loop (B1) and the wall (50) situated at the other end of the room (3) in successive zones (Z2, Z3). These “closed” loops of air (B2, B3, . . . ) penetrate through the occupation zone (2). This second phenomenon is due to the fact that because of the great length (L) of the room (3), the primary flow jet (19) separated early from the ceiling (20) in a separation zone (14). Thereafter, the blown primary jet (19) is no longer attached to the ceiling (20) but can be said to be free. This also leads to a succession of velocity induction effects (30a, 30b, . . . ) and leads to the formation of the secondary vortices (12a, 12b) causing the “closed” loops of air (B2, B3, . . . ) to be created in the secondary zones (Z2, Z3, . . . ). The contaminating aerosols (4a) in suspension (4a) situated in the secondary vortex zones (12a, 12b) of the “closed” air loops (B2, B3, . . . ) become trapped and held remote from the blow and suction surfaces (Ss, Sa) of the built-in ventilation and decontamination system (65). The contaminating aerosols (4a) in suspension can nevertheless be transferred between the various “closed” loops of air (B1, B2, B3, . . . ) via interchange zones (17a, 17b) that are present in a steady state when the room (3) is in an equilibrium state. The room (3) is therefore not treated in optimal manner throughout its volume since the decontamination treatment is slowed down when it comes to removing contaminating aerosols (4a) in suspension. In addition, it will be understood that the increasing number of upward movements as a result of the loops of air (B1, B2, B3, . . . ) increases the extent to which the contaminant aerosols (4b, 4c) that have accumulated and are clinging level with the floor (6) are put back into suspension, thereby increasing the risk of the occupants (1) in the occupation zone (2) suffering biocontamination. In order to reduce the risk of biological contamination through the air, it is preferable to implement the ventilation method using mixing by attached jets in “short rooms” (3a).

FIGS. 4a and 4b are diagrams showing the characteristic means implemented by the method of the invention in a “short” room (3a) for the purpose of considerably reducing or even eliminating the “sloping interfering shunt air flow” (Fs) effect shown in FIGS. 2 and 3. The method of the invention implements the general principles shown in FIG. 2 of a ventilation method using mixing by means of a blown primary jet (19) attached to the ceiling (20) and a suction flow (21) attached to the floor (6) by the Coanda effect (C). However, the method of the invention is remarkable by the fact that the mean blow velocity (Vs) [average of the velocities of the portions of the primary air jet through the blow surface (Ss)] is made to be less than the mean suction velocity (Va) [average of the velocities of the portions of air flow sucked in through the suction surface (Sa)] [Vs<Va].

Although simple, these means implemented by the invention nevertheless lead to eliminating the “sloping interfering shunt air flow” (Fs) effect, thus providing considerable advantages in terms of airborne decontamination (not achieved in the prior art), as can be demonstrated analytically, initially with the help of Bernouilli's theorem and with reference to FIG. 5a.

FIG. 5a is a detail view showing a portion of a moving air stream (vf) that is in continuous motion. For simplification purposes, it is assumed that the air (A) is a perfect incompressible fluid subjected solely to gravity forces. Consideration is given to an infinitesimal portion (da) of the moving air in this moving air stream (vf).

The infinitesimal portion (da) of air belonging to the stream (vf) possesses:

variable section (s);

variable velocity (V);

variable length (dx);

mass (dm); and

local pressure (P).

The density (ρ) of the air is assumed to be constant. The acceleration due to gravity is constant and equal to (g).

To a first approximation, the total mechanical energy Et of the infinitesimal portion (da) of air is constituted by the sum:

of its kinetic energy Ec=½dm×V²;

its pressure potential energy
Epr=P×s×dx=P×dm/ρ

and its gravity potential energy Epe=g×z×dm.

To a first approximation, the total mechanical energy Et of the infinitesimal portion (da) of air is conserved all along the moving fluid stream (vf).

Thus, per unit mass of air moving along the entire moving air stream (vf), the following expression can be derived:
V²/2+P/r+g×z=constant
This is an expression of Bernouilli's theorem, and is valid in the absence of any energy losses (which are taken into consideration below) along the entire moving air stream (vf) in the room (3).

With reference to FIG. 2, there follows a demonstration by “the absurd” leading to the need for the means of the invention [i.e. the mean blow velocity (Vs) must be less than the mean suction velocity (Va)] in order to ensure that the “sloping interfering shunt air flow” (Fs) effect is absent from the room (3) shown in FIG. 2.

If there were no “sloping interfering shunt air flow” (Fs) effect, then all of the streams coming from the blow surface (Ss) would join the suction surface (Sa). If consideration is given to the multitude of moving air streams (vf) that go:

from the blow surface (Ss) where the mean blow velocity of the air is (Vs), the blow pressure is (Ps), and where the height is (h);

to the suction surface (Sa) where the mean suction velocity of the air is (Va), the suction pressure is (Pa), and the height (h) is zero;

then all of the streams would be continuous and none of them would split into a plurality of sub-jets along their length. It would be legitimate to apply Bernouilli's theorem thereto in averaged form over the blow surface (Ss) and the suction surface (Sa) leading to:
Vs²/2+Ps/r+g×h=Va²/2+Pa/ρ(average Bernouilli)

It is important to emphasize that it is the very existence of this non-splitting of the streams (vf) that makes it possible to use Bernouilli's theorem in mean averaged form. It is only under such circumstances that it can be assumed that the entire stream (vf) coming from the blow surface (Ss) reaches the suction surface (Sa), and vice versa. This is not true if there is a “sloping interfering shunt air flow” (Fs).

However, it is obvious that because the air is blown into the room (3) through the blow surface (Ss) and is sucked out through the suction surface (Sa), it is necessary for Ps>Pa.

Now assume that Vs>Va. Under such circumstances, it can be seen that the left-hand side of the above-considered equation (averaged Bernouilli) is necessarily greater than the right-hand side of that equation. It must be concluded that the equation obtained from Bernouilli's theorem is not satisfied. This can be expressed as follows:

[no “sloping interfering shunt air flow” (Fs) effect in the room (3)]

AND [Vs>Va]

=>Bernouilli's theorem averaged over the blow and suction surfaces (Ss, Sa) is not satisfied.

The mathematically logical contraposition of the above expression gives:

Bernouilli's theorem is satisfied=>

[the “sloping interfering shunt air flow” (Fs) effect exists in the room (3)]

OR [Vs<Va]

It is thus shown that the means of the invention, i.e. [Vs<Va], is a necessary condition for there to be no “sloping interfering shunt air flow” (Fs) effect in the room (3).

In fact, the true condition is more severe. In the continuous flow of the moving air stream (vf), a fraction of the total mechanical energy is dissipated under the effect of external forces such as friction against the walls of the room (3), and above all because of the effect of induction between the primary air jet (19) and the air (A) in the room (3). Between the two ends of the moving air stream (vf), there is dissipation, giving a friction head loss ΔH. Bernouilli's theorem as applied to the moving air stream (vf) and corrected for the influence of the head loss then becomes:
Vs²/2+Ps/r+g×h=Va²/2+Pa/ρ+ΔH (Bernouilli with Head Losses)

Thus, in the absence of a “sloping interfering shunt air flow” (Fs) in the room (3), it is necessary that:
(Va²−Vs²)/2=(Ps−Pa)/ρ+g×h−ΔH
Va²−Vs²+2×[(Ps−Pa)/ρ+g×h−ΔH]
i.e.:
Va<(Vs²+2×[(Ps−Pa)/ρ+g×h])^1/2
Thus leading to the following condition:
Vs<Va<(Vs²+2×[(Ps−Pa)/ρ+g×h])^1/2

If the mean suction velocity (Va) is less than the blow velocity (Vs), then a “sloping interfering shunt air flow” (Fs) is established and Bernouilli's theorem is no longer applicable in its averaged form. If the mean suction velocity (Va) is greater than the blow velocity (Vs), then the “sloping interfering shunt air flow” (Fs) phenomenon weakens, tending progressively towards zero. The greater the extent to which the mean suction velocity (Va) exceeds the blow velocity (Vs), the greater the development of induction phenomena leading to air mixing with the induced primary jet (19) and to increased head loss ΔH. Above this second limit:
Va>(Vs²+2×[(Ps−Pa)/ρ+g×h)]^1/2
it can be assumed that Coanda effect (C) flow can no longer be established and the movement present is mainly turbulent.

This is naturally a demonstration based on highly simplifying assumptions, but it makes it possible to understand the importance of adjusting the mean suction velocity (Va) relative to the mean blow velocity (Vs), and thus the importance of these nevertheless simple means [Vs<Va] recommended by the invention.

FIG. 4a shows in highly diagrammatic manner the results obtained by the inventors after performing experiments and also making use of computer tool for simulating air flows. This figure shows the air flow scheme for movements of air (A) in a room (3) similar to the room shown in FIG. 2, but in which means of the invention have been implemented relating to the ratio of the blow mean velocity (Vs) to suction mean velocity (Va). These results obtained from air flow simulation calculations and from measurements taken on prototype devices implementing said means show that, when the means recommended by the invention are implemented in the room (3), i.e. when it is ensured that the mean blow velocity (Vs) [average of the velocities of the portions of the primary air jet (19) through the blow surface (Ss)] is less than the mean suction velocity (Va) [average of the velocities of the portions of the suction air flow (21) through the suction surface (Sa)] [Vs<Va], then the “sloping interfering shunt air flow” (Fs) effect of the prior art as shown in FIG. 2 is strongly attenuated (or even eliminated). This “sloping interfering shunt air flow” (Fs) effect is due mainly to the induction forces generated by the blown primary jet (19). By encouraging the induction forces generated by the suction flow (21), which are directed towards the floor (6), to the detriment of the induction forces generated by the blown primary jet (19), the balance of the interactions of these two types of movement makes it possible to keep the suction air flow (21) attached to the floor (6) by the Coanda effect (C). The dilution of the room (3) is closely associated with the air flow rate used, at the outlet from the blow surface (Ss) and at the inlet of the suction surface (Sa). The purpose here is not to improve dilution efficiency (which is close to 100%), but to improve the quality of decontamination. Since the “sloping interfering shunt air flow” (Fs) is eliminated, any rise of contaminating aerosols (4) into the occupation zone (2) due to air-flow phenomena does not occur, and consequently the probability of the occupants (1) suffering biocontamination is reduced insofar as the biocontaminants (4) remain confined mainly in the fine, highly-contaminated bottom layer of air (Cc) and do not come into contact with the zones (9) in which the occupants (1) breathe.

FIG. 4b is a perspective view of the dispositions to be implemented in the room (3) in terms of effective blow surface (Sse) and effective suction surface (Sae) for implementing the means of the invention in a built-in ventilation system (65). The wall-mounted blow and suction openings (10 and 11) used in built-in ventilation systems (65) are generally fitted with blow and suction grilles (60, 61) occupying the blow and suction surfaces (Ss, Sa) and partially obstructing the air flows. These grilles (60, 61) are conventionally constituted by metal plates provided with a multitude of holes, or metal frames (81) having a plurality of directional slats (83) and/or any other means that partially obstruct the corresponding opening (10, 11), while still allowing air to pass through. The effective area (Sse, Sae) of a grille (60, 61) means the surface of the empty space that would have the same mean overall air flow behavior for the pair comprising [fluid velocity (Vs, Va) passing therethrough/pressure (Ps, Pa)]. Commercially-available grilles are generally accompanied by specifications giving their effective areas. Otherwise, effective area can be measured empirically. In FIG. 4b, the blow grille (Ss) is shown together with a representation of the effective blow surface (Sse). The suction grille (Sa) is also shown together with a representation of its effective suction surface (Sae). It can be seen that it is ensured that the effective blow surface (Sa) in the room (3) is greater than the effective suction surface (Sae). This makes it possible to ensure that [Vs<Va]. It can be seen that the blown primary jet (19) coming from the blow surface (Ss) is well attached to the ceiling (20) by the Coanda effect (C). The suction stream (55) at the floor of the sucked air flow (21) is likewise well attached to the floor (6) by the Coanda effect (C). No “sloping interfering shunt air flow” (Fs) is present in the room (3).

FIG. 5b shows the numerical simulation conditions used for air flow diagrams obtained for a prototype of the PLASMAIR™ independent airborne decontamination device (101) operating in application of the invention in a room (3), as a function of different effective blow ratios (RS). The term “blow ratio” (RS) designates the ratio between the effective blow surface (Sse) and the effective suction surface (Sae). Numerical simulations were performed under the following conditions:

room length (L)=4 meters (m);

room width (l)=3 m;

room height (h)=2.5 m; and

air flow rate: Qv=500 cubic meters per hour (m³/h).

The axes (X), (Y), and (Z) and the list of the various points (P=P1, P2, . . . , P8) used in the simulations and located 2 cm above the floor (6) as shown in FIG. 5b. The numerically calculated magnitude (Yvelocity) represents the local numerical mean of the vertical component of the air velocity taken at each of the points (P=P1, P2, . . . , P8) spaced away from the front face (165) of the device (101) by respective distances (d=d1, d2, . . . , d8). This is the mean of the vertical component of the air velocity in a cubic volume made up of nine individual cubic nodes used for simulation purposes and disposed touching one another, each being centered on a respective simulation point P. The device (101) is placed against the middle of the treatment wall (52). An E-K energy model was used to establish air movements on the basis of Navier-Stokes equations. Although the flow conditions under consideration are turbulent, the state of the studied spatial dimension of the movement is much greater than Kolmogorov scales (molecular type description) for the fluid particles, so Navier-Stokes equations do indeed apply. The numerical simulation made use of smoothing of the movements of air molecules. The use of this numerical simulation method has been found reliable in the past, and no counter example is yet known, providing fluid velocities remain below Mach 13. This is clearly the case here. The type of node selected was hexagonal given the simple architecture of the room (3). The room (3) was modeled using a total of 500,000 nodes. This number is much greater than the number 3,000 commonly considered as being sufficient for confirming studies of this type. By the definition of Yvelocity(P) it will be understood that this parameter, which can be positive or negative, is highly representative of rising or falling movements of air (A) in the room (3).

Thus, if Yvelocity(P) is positive, that means that the air velocity in the vicinity of the point (P) situated 2 cm above the floor has a mean component that slopes upwards. Under such circumstances, it can be deduced that there are mainly upward currents from the floor in the vicinity of the point (P). It can be concluded therefrom that it is highly likely that a “sloping interfering shunt air flow” (Fs) starts from said point.

In contrast, if Yvelocity(P) is negative, that means that the air velocity in the vicinity of the point (P) has a mean component that slopes downwards. It can be concluded therefrom that there is little chance of a “sloping interfering shunt air flow” (Fs) starting from the point.

The table of FIG. 5c gives the results obtained by the simulation. In the table, the first column specifies the point (P=P1, P2, . . . , P8) of the simulation. The second column (shaded) relates to circumstances in which the device (101) has been set so that the blow ratio (RS=0.57) [ratio of the blow effective area (Sse) over the suction effective area (Sae)] is less than 1. That is to say the configuration does not lie within the conditions imposed by the invention. These are conditions in which it is probable that an “interfering shunt air flow” (Fs) will form, as predicted by the theoretical analysis given above.

The third column (shaded) corresponds to conditions in which the device (101) is adjusted so that the blow ratio (RS) is equal to 1. This is the limiting configuration for the presence of an “interfering shunt air flow” (Fs) as predicted by the theoretical analysis given above.

The second and third columns are shaded to show more clearly conditions that lie outside the recommendations of the invention.

Finally, the fourth column (not shaded) relates to circumstances in which the device (101) is adjusted so that the blow ratio (RS=1.43) is greater than 1. I.e. these conditions lie within those imposed by the invention.

Under the conditions of column 2 in which (Va=0.57 Vs), i.e. (Va<Vs), it can be seen that the local numerical mean of the vertical component of the air velocity is positive at points (P4 to P7) that are remote from the device (101). This means that there are upward air movements in the portion of the room (3) that is far away from the device (101). It can reasonably be concluded that an “interfering shunt air flow” (Fs) rises from the far portion of the room towards the blow outlet (110). Under such conditions, the use of the device (101) as an airborne decontamination system is highly ineffective because of the presence of rising currents from the floor (6).

Under the conditions of column 3 in which (Va=Vs), it can be likewise be seen that the local numerical mean of the vertical component of the air velocity is positive at points (P5 to P7) that are remote from the device (101). This means, as above, that there are upward movements of air in the portion of the room (3) that is far from the device (101). It can be concluded that an “interfering shunt air flow” (Fs) raises from the far portion of the room (3) heading towards the blow outlet (110). Under such conditions, the use of the device (101) as an airborne decontamination system is likewise highly ineffective because of the presence of upward currents from the floor (6).

In contrast, under the conditions of column 4 in which (Va=1.43 Vs) i.e. (Va>Vs), it can be seen that on the contrary the local numerical mean of the vertical component of the air velocity is always negative at all of the points (P1 to P8). It can be concluded that no “interfering shunt air flow” (Fs) rises in the room (3). Under such conditions, the use of the device (101) as an airborne decontamination system is highly effective because of the absence of upward currents from the floor (6).

The ability of the method of the invention to eliminate the phenomenon of the “sloping interfering shunt air flow” can be seen more clearly from the graph of FIG. 5d. This graph shows for each of the three above-mentioned flow ratios (RS), a plot of the parameter Yvelocity(P) as a function of the positions of the various simulation points (P1, P2, . . . , P8) on the floor (6) in FIG. 5b. It can be seen that for a given blow ratio (RS), the existence of a “sloping interfering shunt air flow” is represented by the Yvelocity curve penetrating into the shaded zone (Yvelocity>0). This numerical demonstration makes it possible to conclude that the conditions recommended by the invention, i.e. (Va>Vs) or, equivalently, effective blow surface (Sse) greater than effective suction surface (Sae), are effective in eliminating the “interfering shunt air flow” (Fs) that has previously been considered as being inevitable by the person skilled in the art.

The principles of the method of the invention making it possible to deal with the defects of the prior art, can advantageously be implemented within the PLASMAIR™ independent airborne decontamination device (101). A mobile independent airborne decontamination device (101) of the invention is shown in FIG. 6, where it is installed in a short room (3a) in order to implement the method of ventilation by mixing using a blown primary jet (19) and a suction flow (21) both attached by the Coanda effect (C). The device (101) comprises vertical trunk means (103) placed vertically. It is designed to be placed substantially parallel and close to a treatment first vertical wall (52) in the short room (3a) to be treated. The trunk means (103) has a bottom first end (104) for suction situated in its bottom portion close to, but spaced apart from, the floor (6) of the short room (3). The trunk means (103) also has a top second end for blowing (105) that is situated higher up. It is designed to be situated in the top portion of the short room (3a) close to, but spaced apart from, the ceiling (20). The device (101) is fitted with means (106) for setting air (A) into motion. These means are disposed inside the vertical trunk means (103). They establish a pressure difference (ΔP=Ps−Pa) between the blow top end (105) and the suction bottom end (104) to enable the air (A) outside the device to be set into motion. They also serve to cause the air (Ac, Ad) inside the trunk means (103) to be set into motion. A surface effect intake nozzle (118) at the floor (6) extends the trunk means (103) from its bottom suction end (104). It is situated facing the floor (6) of the short room (3a). The intake nozzle (118) provides a suction inlet (111) having a suction surface (Sa) close to the floor (6). The suction surface (Sa) has an inlet section (109) that is substantially vertical. This suction surface (Sa) is constituted by an empty annular space, but to show it more clearly it is represented in shaded manner. It is shown in flattened-out and developed form in the bottom right-hand corner of FIG. 6. It acts at the level of the floor (6) to suck in air (A) in a suction stream (55) that is substantially horizontal, parallel to the floor (6) and attached thereto by the Coanda effect (C). The suction stream (55) can be seen in greater detail in FIG. 6e. A surface effect blow nozzle (129) adjacent to the ceiling (20) extends the blow top end (105) of the trunk means (103). It is designed to be situated close to the ceiling (20). In its top portion it provides a blow outlet (110). The blow outlet (110) presents a porous blow surface (Ss) disposed substantially frontally and bearing laterally on the end side edges (119a, 119b, 119c, 119d) of the blow outlet (110). This is shown on a larger scale in the top right corner of FIG. 6. The blow outlet (110) acts through its entire blow surface (Ss) to produce the upwardly [or horizontally] oriented primary air jet (19) so as to reach the ceiling (20) [or so as to be parallel thereto], in order to enable the blown primary jet (19) to become attached to the ceiling (20) by the Coanda effect (C). Decontamination means (127) (operating by filtering and/or destruction) for acting on contaminating particles (4a, 4b, 4c) in the air (A) are situated inside the vertical trunk means (103) between the intake nozzle (118) and the blow nozzle (129). These means subdivide the section (S) of the vertical trunk means (103) internally so as to oblige the contaminated air (Ac) to pass therethrough, between an upstream contaminated zone (113) and a downstream zone (114) in which the air (Ad) is decontaminated, at least in part. The decontamination device (101) is also characterized in that the effective suction surface (Sae) (shown in the bottom right-hand corner) of the suction surface (Sa) of its intake nozzle (118) is less than the effective blow surface (Sse) (shown in the top right-hand corner) of the blow surface (Ss) of the blow outlet (110). In this way, the mean blow velocity (Vs) [average of the air jet velocities over the blow surface (Ss)] is less than the mean suction velocity (Va) [average of the air flow velocities sucked in through the suction surface (Sa)] [Vs<Va].

With reference to FIG. 6, it can be seen that the device (101) enables the previously treated blown primary jet (19) to be attached to the surface of the ceiling (20). Thereafter, the blown primary jet (19) is subjected at the opposite end of the short room (3a) to separation (14), thus enabling said primary jet (19) to flow along the opposite wall (50). Finally, the blown primary jet (19) is caused to return to the floor (6) where it becomes attached by the Coanda effect (C) so as to be taken up in the continuity of the suction flow (21) attached to the floor (6).

With reference to FIGS. 6a and 6b, there can be seen in greater detail the inside and outside elements of the independent airborne decontamination device (101). The vertical trunk means (103) is contained within an outer casing (126) of the device (101). While the device (101) is in operation, the contaminated air (Ac) coming from the room (3) passes through the surface effect intake nozzle (118) at the floor (6), extending the suction bottom end (104) of the trunk means (103) where it faces the floor (6). Suction pressure (Pa) exists therein. Thereafter, the contaminated air (Ac) passes through a coarse pre-filter (120) where it is cleaned of its bulky airborne elements (131) that could spoil the proper operation of the device (101). The contaminated air (Ac) then passes inside a noise attenuation system (122) serving to avoid noise propagating through the air or through solids. This system is constituted by a plurality of parallel baffles (107, 108) situated in two groups on either side of the air drive means (106) so as to avoid noise propagating in air or in solids. The air drive means (106) are preferably constituted by a centrifugal type fan. Thereafter, the contaminated air (Ac) is constrained to pass through the decontamination means (127) where it is decontaminated, at least in part. The decontaminated air (Ac) reaches the blow top end (105) and is then released through the blow outlet (110). This decontaminated air (Ac) leaves the device (101) through the blow outlet (110) where there exists a blow pressure (Ps). The active means of the device (101) can be put into action or stopped using an on/off system (124). The device (101) is fitted with four wheels (125) secured to its bottom end. As a result the device (101) is mobile. It can easily be moved from one room (3) to another by being taken through the door. A system (123) for adjusting the volume flow rate through the device enables the flow rate to be matched to decontamination requirements and to the size of the room (3).

With reference to FIG. 6c, it can be seen that the combined action of the previously treated blown primary jet (19) attached by the Coanda effect (C) and of the suction flow (21) attached to the floor likewise by the Coanda effect (C) enables the entire occupation zone (2) of the short room (3a) to be covered. With reference to FIG. 3, it can be seen that the mobile independent airborne decontamination device (101) installed in a short room (3a) and set to operate in accordance with the invention makes it possible to ventilate the room (3a) by mixing using a blown primary jet (19) and a suction flow (21) both attached by means of the Coanda effect (C), while also avoiding the “sloping interfering shunt air flow” (Fs) phenomenon, as explained above.

With reference to FIG. 6d, it can be seen that the device (101) of the invention makes it possible in the vicinity of the floor (6) to suck in all of the contaminating aerosols in suspension (4a) and all of the accumulated contaminating aerosols (4b, 4c) situated in the immediate vicinity of the floor (6) in the fine highly-contaminated bottom layer of air (Cc), and to do so progressively as the aerosols settle (the phenomenon described with reference to FIG. 1). This is performed by means of the suction stream (21) attached to the floor (6).

The contaminating aerosols (4a, 4b) situated close to the suction flow (21) and included in the suction steam (55) are continuously directed by the suction induction effect (Ias) towards the suction flow (21) that is attached to the floor (6) in order to be removed via the suction inlet (111) and subjected to the decontamination process.

The device (101) of the invention thus achieves a reduction in the quantity of contaminating particles (4b, 4c) that settle by evacuating the particles continuously.

Consequently, the floor (6) becomes dirtied much more slowly and consequently the room (3) requires cleaning less frequently.

There is also a very significant reduction in the effects whereby contaminating particles that have settled (4b, 4c) are put back into upward movement (as a result of convective effects or of turbulence, . . . applied to said particles).

Furthermore, the effect whereby settled contaminating particles in suspension or that have accumulated (4b, 4c) rise, usually because of the existence of the “sloping interfering shunt air flow” (Fs) phenomenon is practically eliminated.

FIG. 7 is a diagram showing the overall decontamination effect of a mobile independent airborne decontamination device (101) installed in a short room (3a) and adjusted to operate within the invention. It can be seen that this decontamination takes place in different ways on contaminating particles (4) located:

in the top portion (Cs) of the room;

in the bottom portion (Ci) of the room; and

in the middle portion (Cm) of the room.

The blown primary jet (19) and the suction flow (21) both attached by the Coanda effect (C) cover the entire occupation zone (2) of the short room (3a). All of the contaminating particles (4) present in the air (A) in the short room (3a) are subjected to the decontamination process.

In the top portion of the room (Cs), the contaminating particles (4) in the form of contaminating aerosols in suspension (4a) are sucked continuously upwards by the blow induction effect (Iss) towards the ceiling (20) into the blown primary jet (19). Thereafter they are taken vertically along the opposite wall (50) prior to being entrained in the sucked-in air flow (21).

In the middle portion (Cm), the contaminating particles (4) are essentially those that come from emission associated with the occupants in the occupation zone (2). They are at a very low concentration. In addition, they are continuously entrained towards the bottom portion of the room (Ci) by the gravity settling effect (5).

Finally, in the bottom portion of the room (Ci), the contaminating particles (4) in the form of contaminating aerosols in suspension (4a) are continuously sucked downwards by the suction induction effect (Ias) towards the floor (6) into the sucked-in air flow (21).

The absence of the “sloping interfering shunt air flow” (Fs), together with the bottom suction induction effect (Ias) caused by the primary suction flow (21) avoids accumulated contaminating aerosols (4b) and clinging particles (4c) coming from the fine highly-contaminated bottom layer of air (Cc) rising into the higher portions of the room (Cs, Cm).

As a result, the contaminating particles (4) in each portion of the room (Cs, Cm, Ci) are quickly evacuated into the sucked-in air flow (21) prior to penetrating into the device (101) for elimination under the conditions described with reference to FIG. 6d. Real decontamination tests performed using a PLASMAIR™ independent airborne decontamination device (101) have shown its effectiveness in decontaminating a room (3) with performance that comes close to that of a laminar flow but for a cost that is only one-tenth.

A first advantageous embodiment recommended by the invention for the independent airborne decontamination device (101) is shown with reference to FIGS. 6d, 6e, and 8b. In this variant, the intake nozzle (118) is of the suction type at the floor (6), i.e. the suction inlet (111) presents a bottom first suction wall (132) that is almost in contact with the floor (6) or that is constituted by the floor (6) itself, as shown in FIG. 6d. The suction inlet (111) possesses a top second suction wall (133) in the form of a substantially horizontal lip formed by a portion (134) of the base (137) of the intake nozzle (118). This ensures that the vertical suction surface (Sav) is free and constituted by the annular open vertical surface (136) between the base (137) of the intake nozzle (118) and the floor (6). This ensures that air is sucked in at floor level in the form of a stream (55) that is attached to the floor, coming from a planar sector (138) that tapers towards the suction coming from all three other walls (50, 140, 144) of the short room (3a) remote from the treatment vertical wall (52). In addition, the suction vertical surface (Sav) of the intake nozzle (118) of the suction type at the floor (6) is unobstructed. As a result, it presents a developed surface equal to its effective suction surface (Sae) as shown in the bottom right-hand corner of FIG. 8b. It can be seen that the effective suction surface (Sae) is less than the effective blow surface (Sse) at the blow surface (Ss) of the blow outlet (110) (as shown in the top right corner of FIG. 8b). The characteristic disposition of this first variant makes it possible simultaneously to improve the floor effect with respect to suction and thus the fine bottom layer (Cc) of highly contaminated air, while also making it possible to limit the “sloping interfering shunt air flow” (Fs) effect.

A second advantageous embodiment recommended by the invention for an independent airborne decontamination device (101) is shown with reference to FIGS. 8a to 8d. In FIGS. 8a to 8b, it can be seen that the blow top edge (130) is situated at a distance from the floor (Ds) that is greater than 170 cm. This distance is for a room having a standard ceiling height of about 250 cm. Complying with this distance (Ds) ensures that the air flow scheme as described with reference to FIG. 6 does indeed take place. In FIGS. 8c and 8d, it can be seen that the porous flow surface (Ss) of the blow outlet (110) is provided with means (163) for directing the blown air streams (164) constituting the blown primary jet (19) and mechanically controlled by means of a lever (167). The flow-directing means (163) enable the blow angle of incidence (αs) from the blow outlet (110) to be adjusted [average over the blow surface (Ss) of the angles of the blown air streams (164) of the blown primary jet (19) relative to the horizontal plane (H)], so as to ensure that this angle lies substantially in the range 20° to 70°. FIGS. 8e and 8f show the importance of this second disposition recommended by the invention. Each of these figures is a side view of a device (101) placed in a short room (3a) presenting the same characteristics as described with reference to FIG. 5b. Numerical simulation has been used to study the influence of adjusting the blow angle of incidence (αs) of the blow nozzle (110). FIG. 8e corresponds to αs =20°. FIG. 8f corresponds to αs=70°. It can be seen that in the recommended adjustment range (20°<αs<70°), providing the other dispositions of the invention are satisfied, then the “sloping interfering shunt air flow” (Fs) phenomenon is avoided. FIG. 8g corresponds to αs<20°. FIG. 8h corresponds to αs>70°. It can be seen that outside the recommended adjustment range (20°<αs<70°), even when the other dispositions of the invention are established, the “sloping interfering shunt air flow” (Fs) phenomenon appears. When αs>70°, a multi-zoning (Z1, Z2) phenomenon occurs together with the formation of a plurality of air loops (B1, B2) as described for “long” rooms with reference to FIG. 3, and a “sloping interfering shunt air flow” (Fs) appears. When αs<20°, only a “sloping interfering shunt air flow” (Fs) is seen to appear.

A third advantageous embodiment recommended by the invention of the independent airborne decontamination device (101) is shown with reference to FIG. 9b. The effective blow surface (Sse) of the blow outlet (110) is at least 20% greater than the effective suction surface (Sae) of the intake nozzle (118). In addition, the volume flow rate (Qv) of the air drive means (106) is adjusted in such a manner that the mean blow velocity (Vs) [average of the speeds of the outlet jets through the porous blow surface (Ss)] is greater than 0.79 m/s [Vs>0.79 m/s]. With these dispositions, the mean suction velocity (Va) [average of the air flow velocities sucked in through the suction surface at the intake of the suction porous surface] is at least 20% greater than the mean blow velocity (Vs), (Va>1.2×Vs). When these particular dispositions of the invention are satisfied, then the “sloping interfering shunt air flow” (Fs) phenomenon is avoided.

In contrast, FIG. 9a is a diagram corresponding to the results that are obtained by numerical simulation for Vs<0.79 m/s and Va<1.2×Vs. It can be seen that during numerical simulation, when lying outside the threshold values recommended above, both a multi-zoning (Z1, Z2) phenomenon with a plurality of air loops (B1, B2) arises as described for “long” rooms with reference to FIG. 3, together with the appearance of a “sloping interfering shunt air flow” (Fs). The characteristic disposition of this third variant also makes it possible to limit the “sloping interfering shunt air flow” (Fs) effect.

A second preferred embodiment recommended by the invention of the independent airborne decontamination device (101) is shown with reference to FIG. 10a. In this second embodiment, the blow nozzle (129) having the porous blow surface (Ss) is made wider than the mean width of the vertical trunk means (103). This widening is measured perpendicularly to the vertical plane of symmetry (PV) of the device (101), extending perpendicularly to its front portion (165). It is measured parallel to the treatment first vertical wall (52). Thus, the porous blow surface (Ss) is larger, thereby increasing the blow ratio (RS) for a suction effective area (Sae) that remains unchanged. The blow velocity (Vs) is thus greatly decreased relative to the suction velocity (Va). The reduction in the “sloping interfering shunt air flow” effect is increased thereby.

A particular implementation of this second preferred embodiment is described with reference to FIGS. 15a and 15b. The blow nozzle (129) includes means (157) for widening its lateral dimensions. These means are constituted by at least one [and preferably two as shown in FIGS. 15a and 15b] porous flexible cylindrical blow portions (159) disposed on either side of the top portion of the trunk means (103). They are placed perpendicularly to the vertical plane of symmetry (PV) of the device (101). These porous flexible cylindrical blow portions (159) droop down vertically when the air drive means (106) are not active, as shown in FIG. 15a. However, they deploy horizontally under the effect of the pressure (Ps) when the air drive means (106) are active, as shown in FIG. 15b. They thus provide a moving blow surface (Ss) that is substantially horizontal in the deployed position (161).

The porous flexible cylindrical blow portions (159) can be made in the form of glove fingers using a reinforced woven textile material. The textile material of the glove finger is covered in a protective adhesive strip extending along a generator line thereof. Then a sealing covering is applied to the outside of the glove finger (e.g. of the oil cloth type). Thereafter, the adhesive protective strip is withdrawn. As a result, the major fraction of the glove finger is covered in a sealing material that is impermeable to air. However a longitudinal surface in each porous flexible cylindrical blow portion (159) is free of the sealing material along a generator line so as to allow air to pass through. As a result, a porous surface (Spa) is formed over a fraction of the surface of the glove finger, said fraction occupying a generator line. The remaining surface (SE) over the other fraction is airtight. This provides a blow surface (Ss) that allows a blown primary jet (19) to be issued along the generator line, i.e. parallel to the ceiling (20) when the porous flexible cylindrical blow portions (159) are deployed. Advantageously, it is possible to use a telescopic stiffener (170) having one end placed inside the porous flexible cylindrical blow portion (159) and having its other end secured to the vertical trunk means (103). The telescopic stiffener means (170) serve to increase the extent to which each porous flexible cylindrical blow portion (159) can project when deployed (161). The telescopic stiffener means (170) is preferably deployed by the pressure inside the device (101). It can be collapsed by means of a spring.

This provides a device (101) that is relatively narrow when inactive. It can easily be passed through a door. In contrast, when in the active position, the blow surface (Ss) can deploy over a width that is substantially equal to the width of the room (3). As a result a blow flow is provided that covers the room (3), being deployed over its entire width. This leads to decontamination that is much more effective.

A third preferred embodiment recommended by the invention of the independent airborne decontamination device (101) is shown with reference to FIG. 10b. The porous blow surface (Ss) comprises a front blow surface (Ssf) extended sideways by two side blow surfaces (Sslg and Ssld) formed in the side walls of the blow nozzle (135) for being placed facing the side walls (140, 144) of the room (3). This disposition makes it possible to increase the effective blow surface (Sse) and to treat the side zones of the room (3) that are situated along the side walls (140, 144) more effectively. This also contributes to better elimination of the “sloping interfering shunt air flow” (Fs) effect.

A fourth preferred embodiment recommended by the invention of the independent airborne decontamination device (101) is shown with reference to FIG. 11. The intake nozzle (118) of the suction type at the floor has a top wall (139) that is wider than the mean width of the vertical trunk means (103) that it extends downwards. This widening is measured perpendicularly to the vertical plane of symmetry (PV) of the device (101) perpendicular to its front portion (165). The side walls (141) to the intake nozzle (118) are thus further apart.

A fifth preferred embodiment recommended by the invention of the independent airborne decontamination device (101) is shown with reference to FIGS. 10a, 10b, 12, 13a, and 13b. The intake nozzle (118) has a tulip-shaped flared bottom portion (143) placed facing the floor (6). Numerical simulation has also shown that this disposition contributes to better elimination of the “sloping interfering shunt air flow” (Fs) effect.

A sixth preferred embodiment recommended by the invention of the independent airborne decontamination device (101) is shown with reference to FIG. 12. The mean section of the vertical trunk means (103) has a longitudinal extent (DL) (size) taken in the plane of symmetry (PV) of the device (101) that is smaller than the longitudinal extent (DLS) of the intake nozzle (118). These two extents are measured parallel to the vertical plane of symmetry (PV) of the device perpendicularly to its front portion (165).

A seventh preferred embodiment recommended by the invention of the independent airborne decontamination device (101) is shown with reference to FIGS. 13a and 13b. The vertical trunk means (103) includes a trunk portion (147) that is adjustable in length. This adjustable trunk portion (147) can be constituted in particular by a bellows (149). Such a disposition enables the height of the porous flow surface (Ss) to be adapted as a function of the height (h) of the room (3). As a result, the device (101) can be used in rooms (3) of various architectures, thereby ensuring that the primary jet (19) is attached to the ceiling (20) by the Coanda effect, by being lengthened (152) as shown in FIG. 13b. Shortening the portion (147) of the duct that is adjustable in height enables the device (101) to pass through a door of the room (3) while the device is in its retracted mode (151), as shown in FIG. 13a.

An eighth preferred embodiment recommended by the invention of the independent airborne decontamination device (101) is shown with reference to FIGS. 14a and 14b. The device (101) has an auxiliary intake nozzle (155) formed in the front portion of the trunk means (103). The auxiliary intake nozzle (155) is situated about halfway up (about 1 meter from the floor). The auxiliary intake nozzle (155) opens out into the trunk means (103) upstream from the means (127) for eliminating contaminated particles, i.e. into said contaminated upstream zone (Ac). This disposition enables air decontamination to be performed in the vicinity of the auxiliary intake nozzle (155). An occupant (2) carrying contaminated particles (4) releases contaminated aerosols (4a) in suspension. When hospitalized, this occupant is positioned in substantially horizontal manner in a bed and the occupant's breathing passages are situated at a height of approximately 1 m. By means of the auxiliary intake nozzle (155), the use of this preferred embodiment makes it possible to treat directly any emissions of contaminated aerosols (4a) in suspension that are emitted by the occupant in the zone (Cm) as shown in FIG. 7.

OBJECTS AND ADVANTAGES OF THE INVENTION

The main object and advantage of the invention is to attenuate or even eliminate the “interfering shunt air flow” phenomenon that is considered in the prior art as being necessarily associated with using a ventilation method by mixing using a blown primary jet attached to the ceiling and a suction flow attached to the floor by the Coanda effect.

A second advantage of the invention is to reduce the effects of putting contaminated particles that have settled in a room back into upward movement.

A third advantage of the invention is to suck in aerosols in suspension and aerosols accumulated in the highly contaminated fine layer of air situated close to the floor progressively as they settle.

A fourth advantage of the invention is to reduce the quantity of contaminated particles clinging to the floor, and consequently to reduce the cleaning requirements of the room.

A fifth advantage of the invention is to reduce the concentration of contaminating aerosols in suspension in the occupation zone of the room as occupied by its occupants.

A sixth advantage of the invention is to reduce the occurrence of diseases due to biological contamination of airborne origin in a room.

A seventh advantage of the invention is to provide a ventilation system using attached jet mixing that presents performance close to the performance of a lamellar flow in terms of decontaminating a room, and to do so at a cost that is smaller by about one order of magnitude.

An eighth advantage of the invention is to provide an airborne decontamination system that provides a high degree of cleanliness and that is mobile.

A ninth advantage of the invention is to make it possible to bring means quickly into premises that are not so equipped for combating the occurrence of biological contamination. This is equally applicable to medical applications in the home, to combating epidemics, to providing civil protection, to producing pharmaceuticals and/or foodstuffs, . . . .

A tenth advantage of the invention is to provide a mobile device that is well adapted to capturing and removing airborne contaminating particles close to the floor and to avoiding putting them back into suspension. This is of particular concern to subjects who are hypersensitive (allergies).

An eleventh advantage of the invention is to increase the speed at which a room is ventilated by mixing is decontaminated.

INDUSTRIAL APPLICATIONS OF THE INVENTION

The invention makes it possible at reduced cost to optimize the process of decontaminating a room and of removing the airborne contaminating particles therein. The invention thus possesses industrial applications in any type of closed structure that requires air to be decontaminated. In non-exhaustive manner, this can apply to: health, food industry, research, transport, animal husbandry, pharmacy, schools, . . . .

A particularly suitable application lies in airborne decontamination of health premises for protecting patients and staff in a hospital environment against the risk of cross-contamination. This relates to providing protection in hospitals against risks of contagion of the SRAS (severe acute respiratory syndrome) type . . . .

Another application lies to temporarily combating certain consequences of conventional ventilation in professional, public, and domestic premises leading to risks of infection by airborne contaminants conveyed by an air conditioning system. This relates to local protection in a room of a ventilated building against problems of allergy and/or cross-contamination (sick building syndrome) due to the building being air conditioned.

Mention can be made of an application to transporting passengers by sea or by air.

Mention can also be made of an application to industries that present a local biological risk associated with the production of a contaminating agent. This can apply in the pharmaceutical industry and in the food industry. It also relates to microbiological research laboratories.

Another application applies to protecting high density livestock (chickens, pigs, . . . ) in order to maintain good health, in particular in farms where intrusions are limited (for selective breeding).

Another application lies in civil protection in the event of a biological terrorist attack.

A more widespread application lies in limiting risks of transmission between clients and/or staff in cafeterias and restaurants.

Another application lies in preventing the risks of epidemics in nurseries, schools, and premises of small size but containing large numbers of people.

Finally, an application lies in protecting staff and visitors in the offices of dentists, vets, . . . .

The scope of the invention should be considered with respect to the following claims and legal equivalents thereof, rather than from the examples given above.

Claims

1-16. (canceled)

17. A method of ventilating a room (3) by mixing, using a blown primary jet (19) attached to the ceiling (20), and a suction flow (21) attached to the floor (6), both by the Coanda effect (C), the method being of the type comprising:

a) blowing a primary jet of air (19) that has previously been treated into the room (3); i) through a blow surface (Ss) situated in register with a treatment side wall (52) in the vicinity of the ceiling (20); and ii) in a blow direction of incidence (Is) oriented towards the ceiling (20) in such a manner as to cause said blown primary jet (19) to become attached to the surface of the ceiling (20) by the Coanda effect (C); and then

b) sucking in a vitiated suction air flow (21) at a flow rate equivalent to that of the primary jet (19): i) through a substantially suction surface (Sa) situated in register with the same treatment side wall (52) in the vicinity of the floor (6) of the room (3); and ii) ensuring that a suction stream of air (A) is sucked-in in the vicinity of the floor (6), which stream (55) is: substantially horizontal; and parallel to the surface of the floor (6);

the ventilation method being characterized further, in combination:

c) firstly, by ensuring that the mean blow velocity (Vs) is less than the mean suction velocity (Va); and

d) secondly, by the vitiated sucked-in air flow (21) being sucked in through a suction surface (Sa) presenting a bottom suction wall (132) in physical contact with the floor (6) of the room (3), such that the suction stream (55) of sucked-in air (A) is attached to the surface of the floor (6) by the Coanda effect (C) in register with and facing the suction surface (Sa).

18. An independent airborne decontamination device (101) for a room (3) for ventilating by mixing using a blown primary jet (19) and a suction flow (21) both attached by the Coanda effect (C), the device (101) being of the type comprising:

a) vertical trunk means (103) disposed vertically, said trunk means (103) comprising: i) a suction bottom first end (104) situated in the bottom portion thereof close to and separated from the floor (6) of the room (3); and ii) a blow top second end (105) situated higher up to be situated in the top portion of the room (3) close to and spaced apart from the ceiling (20);

b) drive means (106) for setting the air (A) into motion, the drive means being disposed inside the vertical trunk means (103) and establishing a positive pressure (ΔP) between the blow top end (105) and the suction bottom end (104) so as to enable air to move inside and outside the trunk means (103);

c) a surface effect intake nozzle (118) at the floor (6) extending the suction bottom end (104) of the trunk means (103) where it faces the floor (6) of the room (3), while leaving a suction opening (111) in the vicinity of the floor (6), the opening: i) presenting a suction surface (Sa) of substantially vertical inlet suction; and ii) providing suction of the air (A) in a suction stream (55) at the level of the floor (6), the stream being: substantially horizontal; and parallel to the floor (6);

d) a surface effect blow nozzle (129) at the ceiling (20) extending the blow top end (105) of the trunk means (103) and forming a blow outlet (110) at its top portion, the outlet: i) presenting a porous blow surface (Ss) disposed substantially frontally bearing laterally against the extreme side edges (119a, 119b, 119c, 119d) of the blow outlet (110); and ii) producing a primary jet (19) of air through the entire blow surface (Ss), the jet being oriented upwards or horizontally, in order to enable the blown primary jet (19) to be attached to the ceiling (20) by the Coanda effect (C); and

e) decontamination means (127) for decontaminating contaminating particles in the air (A) (by filtering and/or destroying them), the decontamination means: i) being situated inside the vertical trunk means (103) between the intake nozzle (118) and the blow nozzle (129); and ii) internally partitioning the vertical trunk means (103) across its section (S) so as to constrain the contaminated air (Ac) to pass therethrough between a contaminated upstream zone (113) and a downstream zone (114) in which the air (Ad) is decontaminated at least in part;

the decontamination device (O1) being characterized in that further, in combination:

f) firstly, its intake nozzle (118) is of the suction type at the floor (6), i.e. having a suction inlet (111) that: i) possesses a bottom, first suction wall (132) that is formed by the floor (6) itself; ii) and possesses a top, second suction wall (133) formed by a portion (134) of the base (137) of the intake nozzle (118); iii) such that its vertical suction surface (Sa) is free and constituted by an annular open vertical surface portion (136) formed between the base (137) of the intake nozzle (118) and the floor (6), and serves to suck in air at the level of the floor (6) in a stream (55) that is attached to the floor (6) by the Coanda effect, and coming from a plane sector (138) tapering towards the suction and coming from the other three walls (50, 144, 140) of the room (3) opposite from the treatment wall (52); and

g) secondly, the vertical suction surface (Sav) of the suction intake nozzle (118) at the floor (3) is less than the effective blow surface (Sse) of the blow surface (Ss) of the blow outlet (110), so that the mean blow velocity (Vs) is less than the mean suction velocity (Va).

19. An independent device (101) according to claim 18 for airborne decontamination of a room (3) for ventilating by mixing using a blown primary jet (19) and a suction flow (21) both attached by the Coanda effect (C), the device (101) being characterized in that further, in combination:

a) the top edge (142) of the porous blow surface (Ss) is situated at a distance (Ds) above the floor of more than 170 cm; and

b) the porous blow surface (Ss) of the blow nozzle (110) is provided with mechanically adjustable director means (163) for directing the blown air streams (164) making up the blown primary jet (19), to cause the blow angle of incidence (αs) from the blow nozzle (129) to lie in the range 20° to 70° relative to the horizontal plane (H).

20. An independent device (101) according to claim 18 for airborne decontamination of a room (3) for ventilating by mixing using a blown primary jet (19) and a suction stream (21) both attached by the Coanda effect (C), the device (101) being characterized in that further, in combination:

a) firstly, the effective area (Sse) of the blow surface of its blow nozzle (129) and its air drive means (106) are dimensioned in such a manner that the mean blow velocity (Vs) of the blow nozzle (129) is greater than 0.79 m/s; and

b) secondly, the effective area (Sse) of the blow surface of its blow outlet (110) is at least 20% greater than the effective area (Sae) of the suction surface of its intake nozzle (118), in such a manner that the mean suction velocity (Va) is at least 20% greater than the mean blow velocity (Vs).

21. An independent device (101) according to claim 18 for airborne decontamination of a room (3) for ventilating by mixing using a blown primary jet (19) and a suction stream (21) both attached by the Coanda effect (C), the device (101) being characterized in that further, said blow nozzle (129) against which said porous blow surface (Ss) bears is wider than the mean width of the vertical trunk means (103) that it extends upwards.

22. An independent device (101) according to claim 18 for airborne decontamination of a room (3) for ventilating by mixing using a blown primary jet (19) and a suction stream (21) both attached by the Coanda effect (C), the device (101) being characterized in that further, the porous blow surface (Ss) has a front blow surface (Ssf) extended laterally by lateral blow surfaces (Sslg and Ssld) formed on the side walls (135) of the blow nozzle (129) placed facing the side walls (140, 144) of the room (3).

23. An independent device (101) according to claim 18 for airborne decontamination of a room (3) for ventilating by mixing using a blown primary jet (19) and a suction stream (21) both attached by the Coanda effect (C), the device (101) being characterized in that further, the intake nozzle (118) is enlarged at its top wall (139) to be wider than the mean width of the vertical trunk means (103) that it extends downwards.

24. An independent device (101) according to claim 18 for airborne decontamination of a room (3) for ventilating by mixing using a blown primary jet (19) and a suction stream (21) both attached by the Coanda effect (C), the device (101) being characterized in that further, the intake nozzle (118) includes a tulip-shaped flare bottom portion (143) placed in register with the floor (6).

25. An independent device (101) according to claim 18 for airborne decontamination of a room (3) for ventilating by mixing using a blown primary jet (19) and a suction stream (21) both attached by the Coanda effect (C), the device (101) being characterized in that further, the mean section of its vertical trunk means (103) has a longitudinal extent (DL) (bulk) in the plane of symmetry (PV) of the device (101) that is less than the longitudinal extent (DLS) of the intake nozzle (118).

26. An independent device (101) according to claim 18 for airborne decontamination of a room (3) for ventilating by mixing using a blown primary jet (19) and a suction stream (21) both attached by the Coanda effect (C), the device (101) being characterized in that further, it includes an auxiliary intake nozzle (155):

a) arranged in the front portion of the trunk means (103);

b) about halfway up (about 1 meter from the floor (6)); and

c) opening out into the trunk means (103) into said upstream contaminated zone (Ac) upstream from the means (127) for eliminating contaminating particles.

27. An independent device (O1) according to claim 18 for airborne decontamination of a room (3) for ventilating by mixing using a blown primary jet (19) and a suction stream (21) both attached by the Coanda effect (C), the device (101) being characterized in that further, its vertical trunk means (103) includes a trunk portion (147) that is adjustable in length (in particular by means of a bellows (149)) to enable the height of the porous blow surface (Ss) to be adapted as a function of the height (h) of the room (3), so that the primary jet (19) attaches to the ceiling (20) by the Coanda effect (C), while still enabling the device (101) to pass through a door of the room (3).

28. An independent device (101) according to claim 18 for airborne decontamination of a room (3) for ventilating by mixing using a blown primary jet (19) and a suction stream (21) both attached by the Coanda effect (C), the device (101) being characterized in that further, its blow nozzle (129) includes means (157) for enlarging its lateral dimensions enabling its blow surface (Ss) to be extended laterally.

29. An independent device (101) according to claim 28 for airborne decontamination of a room (3) for ventilating by mixing using a blown primary jet (19) and a suction stream (21) both attached by the Coanda effect (C), the device (101) being characterized in that further, its blow nozzle (129) includes means (157) for enlarging its lateral dimensions constituted by at least one (and preferably two) porous flexible cylindrical blow portions (159),

a) disposed laterally relative to the trunk means (103) at the top portion thereof (105), perpendicularly to the vertical plane of symmetry (PV) of the device (101); and

b) deployable under the effect of the pressure (Ps) so as to provide a mobile flow surface (Ss) that is substantially horizontal in the deployed position (161).

30. An independent device (101) according to claim 29 for airborne decontamination of a room (3) for ventilating by mixing using a blown primary jet (19) and a suction stream (21) both attached by the Coanda effect (C), the device (101) being characterized in that further, said porous flexible cylindrical blow portion (159) comprises:

a) a porous surface (Spa) over a fraction of its surface for forming a blow surface (Ss) and enabling a blown primary jet (21) to be emitted; and

b) a leakproof surface (SE) over another fraction of its surface.

31. An independent device (101) according to claim 29 for airborne decontamination of a room (3) for ventilating by mixing using a blown primary jet (19) and a suction stream (21) both attached by the Coanda effect (C), the device (101) being characterized in that further, it includes at least one telescopic stiffening means (170) having one end placed inside the porous flexible cylindrical blow portion (159) and having its other end secured to the vertical trunk means (103).

32. An independent device (101) according to claim 31 for airborne decontamination of a room (3) for ventilating by mixing using a blown primary jet (19) and a suction stream (21) both attached by the Coanda effect (C), the device (101) being characterized in that further, the deployment of said telescopic stiffener means (170) is performed by the pressure inside the device (101).