WO1998023905A1 - Device for reducing air pressure supplied by an air conditioning plant - Google Patents

Abstract

The invention concerns a device for reducing air pressure coming from an air conditioning plant for supplying an installation, comprising from upstream to downstream an upstream channel (1), a converging element (3) and a downstream channel (5). This device is characterised in that the ratio of the outlet diameter (d) of the converging element (3) over the diameter (D') of the downstream channel (5) is approximately between 0.25 and 0.70, the downstream channel (5) being closed in its upstream part, so as to generate in the downstream channel (5) an internal peripheral induced flux.

Description

 DEVICE FOR REDUCING THE PRESSURE OF THE AIR SUPPLIED BY AN AIR CONDITIONING UNIT

The present invention relates to improvements to the air conditioning batteries used in air conditioning and aeraulic heating installations, in particular those comprising numerous batteries, and more particularly relates to a device making it possible to reduce, to a large proportion, the pressure of the air at a given point in a distribution pipe.

The present invention is more particularly applicable to installations ensuring the air conditioning of large buildings comprising a large number of premises to be treated. Usually these rooms do not all have the same air conditioning needs, for example due to the needs specific to their function or their situation within the building in which they are located, which implies that they require thermal power for their air conditioning. more or less important.

Generally the air conditioning of the various premises is ensured from a centralized ventilation system which is capable of supplying a certain flow of air at a given pressure and at a given temperature. As this system is unique for the entire installation, it is therefore not satisfactory to directly supply each of the premises, and the air delivered must therefore undergo a treatment which depends on the specificity of each room.

However, it turns out that in certain parts of the installation, the pressure is too high for the air treatment operations that it is desired to carry out, and it is therefore essential to drop this air pressure. prior to the specific treatment mentioned.

Of course, in the prior art, devices are known which are capable of subjecting an incident air flow to such a pressure drop. In particular, expansion boxes are used for this purpose which consist of a metal casing inside which a circular or rectangular flap pivots about an axis. The rotation of this flap can be controlled manually or automatically by a mechanism which controls the air flow or the upstream pressure. It is known, however, that these expansion boxes have multiple drawbacks and in particular that they are of considerable cost and size, that they are complicated to implement and that they usually generate high noise, so that we are forced to add soundproofing means to them, which further increases their cost and size. In addition, these expansion boxes seriously disturb the distribution of the air streams, so that the pressure drop thus obtained generates significant turbulence and sometimes even pressure instabilities.

It is also known that such a pressure drop can be obtained by means of a simple flap which is arranged in the air distribution pipe. If such a device undoubtedly has the advantage of simplicity, however, besides the fact that it is the source of strong noise disturbances, it also does not solve the problem of respecting the flow of the air streams. There are also known, in particular from application WO 92/17740, installations which use induction means, comprising a convergent element, in which a proportion of air sucked in from the outside by induction. It has been found in such installations, that the flow of external air sucked in at the periphery of a pipe, had the effect of forming a periphery of the latter a flow of air at low speed, which had the effect of isolating the wall of the central air flow channel which flows at high speed, thus allowing a noisy flow.

The Applicant has found that, when the outside air inlet orifice was closed, nonetheless, by an induction phenomenon (here called "internal induction"), vortices were created at low speed at the periphery. of the wall of the pipe which have the effect, as previously, of preserving this pipe against the high-speed flow of the central air flow, which reduces noise in significant proportions. It has thus been established that such a device provides its effects when a convergent element is used, the ratio of the outlet diameter to the diameter of the downstream pipe being between approximately 0.25 and 0.70.

The object of the present invention is therefore to propose a means which makes it possible to absorb significant overpressures without appreciable increase in noise, without appreciable increase in volume and while respecting the profile of the air streams.

The present invention thus relates to a device reducing the pressure of the air coming from an air conditioning unit which is intended to supply an installation, and which comprises from upstream to downstream, an upstream pipe, a converging element and a downstream pipe, characterized in that the ratio of the outlet diameter of the converging element to the diameter of the downstream pipe is between approximately 0.25 and 0.70, the downstream pipe being closed in its upstream part, so as to create a peripheral internal induction flow in the downstream pipe.

In one embodiment of the invention, the device comprises, upstream of the converging element, means for rectifying the air streams. Preferably, the downstream pipeline is aligned with the pipeline upstream, and has a length at least equal to four times its diameter, this length being greater the greater the desired pressure drop.

In a preferred embodiment of the invention, the convergent element consists of a frustoconical element comprising fixing means on the one hand, on the upstream pipe and on the other hand, on the downstream pipe. The frustoconical element can of course be removable. In a variant of this embodiment, the half-angle at the top of the frustoconical element is between 15 ° and 40 ° and is preferably equal to 21 ° ± 2 °.

Preferably, the diameter of the downstream pipe will be at least equal to 3/4 of the diameter of the upstream pipe and at most equal to 1.5 times this.

An embodiment of the present invention will be described below, by way of non-limiting example, with reference to the appended drawing in which:

Figure 1 is a schematic view in longitudinal section of a first embodiment of one invention.

Figure 2 is a schematic view in longitudinal section of a second embodiment of the invention ¹ . Figure 3 is a schematic view in longitudinal section of a third embodiment of one invention.

In Figure 1 there is shown a pipe 1 for supplying air to a room, or upstream pipe, which is to do this in communication with a central pressurized air supply, not shown in the drawing. This power station delivers air at a pressure P and it is desired to supply this same air at a pressure P 1 lower than the pressure P to a facility located downstream. Given the use for which this air is intended, namely the heating or air conditioning of occupied premises, it is imperative that the installation is silent operation. The supply line 1 has a diameter D and opens into a converging element 3 formed by a truncated cone of height h, the outlet diameter of which is d. The supply line 1 may include fins, not shown in the drawing, intended to straighten the air streams arriving in the line. The convergent element 3 flows into a cylindrical pipe 5, or downstream pipe, which is aligned with the upstream pipe 1 and which has a diameter D 'greater than the diameter D thereof. The upstream end of the pipe 5 is closed by a sealing collar 7 in order to avoid any phenomenon of suction of outside air by induction. Furthermore, the ratio between the outlet diameter d of the converging element 3 and the diameter D ′ of the downstream pipe 5 is between 0.25 and 0.70.

Under these conditions, when the pipe 1 is supplied with air, a dart 4 is created at the outlet orifice of the convergent element 3 which extends over a length 1_ inside the downstream pipe. 5. There is thus created, at the outlet of the nozzle of the converging element 3, a phenomenon of induction suction. As any external air supply is made impossible by the upstream closure of the pipe 5, this suction phenomenon creates around the dart 4 a vortex zone 13 which isolates the walls of the pipe 5 from the central dart 4 and which makes the device according to the invention particularly silent. It can be seen that downstream of the central dart 4, at a distance l> l from the converging element 3, the pressure which exists in the pipe 5 is situated at a value PI lower by a value ΔP than the upstream pressure P delivered by the central unit, and which depends in particular on the dimensional characteristics of the components. The length 1J_ of the downstream part of the pipe will thus be given a value that is all the greater the more the pressure drop ΔP is desired to be greater. The

pressure drop ΔP can be between about 50 Pa and 400 Pa. The Applicant has found that the diameter D ′ of the downstream pipe 5 could be substantially equal to that of the upstream pipe 1. This form of implementation is particularly advantageous in that it is of a particularly easy embodiment in terms of functional.

By way of example, from a supply center supplying air under a pressure P of 300 Pa, a device according to the invention is supplied by a pipe whose diameter D is equal to 25 cm and which led into a converging element 3 formed of a truncated cone of height h equal to 13.7 cm whose outlet diameter d was 14 cm. The converging element 3 flowed in a downstream pipe 5 with a diameter D 'of 32 cm, so that the ratio d / D' was at 0.44. The pressure PI which existed in this pipe 5, downstream of the dart 4 was measured, and its value was close to 100 Pa. The device according to the invention was thus able to drop the pressure by a value ΔP d 'about 200 Pa. The noise produced was then measured.

To do this, the device according to the invention was compared with a pressure reducing device according to the prior art, constituted in this case by an expansion box. With a sound level meter, the level of noise produced in a room with an attenuation of 10 dB was noted and a noise emission with an intensity of 40 dB (A) for the non-soundproof expansion box and a noise intensity of 35 dB (A) for the device according to the invention, which represents a noise reduction of more than 50 %. The pressure drop produced by the device was therefore carried out in a particularly silent manner in comparison with the devices of the prior art.

There are shown in Table I below five other examples of implementation of the invention which show that a significant reduction in noise is obtained under very diverse operating conditions.

TABLE I

Dans une variante de mise en oeuvre l'élément convergent 3 peut être constitué d'un élément formé d'une base cylindrique et d'une partie tronconique dont le sommet définit un orifice de sortie de diamètre d. Le diamètre interne de la base est légèrement supérieur au diamètre externe D de la conduite amont de façon qu'elle s'emmanche à force sur celle-ci. De même la conduite avale aura un diamètre D' légèrement supérieur à celui du diamètre externe de la base de l'élément tronconique de façon à pouvoir s'emboîter sur celui-ci.

In an alternative embodiment, the converging element 3 can consist of an element formed by a cylindrical base and a frustoconical part, the top of which defines an outlet orifice of diameter d. The internal diameter of the base is slightly greater than the external diameter D of the upstream pipe so that it is force fitted onto it. Likewise, the downstream pipe will have a diameter D ′ slightly greater than that of the external diameter of the base of the frustoconical element so as to be able to fit onto it.

This mode of implementation is particularly advantageous in that it allows in a simple manner for a user to choose, as a function of the desired pressure reduction, the appropriate converging element from a collection of converging elements of different characteristics.

Claims

1.- Device reducing the air pressure from an air conditioning unit which is intended to supply an installation, and which comprises from upstream to downstream, an upstream pipe (1), a converging element (3) and a downstream pipe (5) characterized in that the ratio of the outlet diameter (d) of the converging element (3) to the diameter (D ') of the downstream pipe (5) is between approximately 0 , 25 and 0.70, the downstream pipe (5) being closed in its upstream part, so as to create in the downstream pipe (5) a peripheral internal induction flow. 2.- Device according to claim 1 characterized in that it comprises, upstream of the converging element (3), rectifying means of the air streams. 3.- Device according to one of the preceding claims characterized in that the downstream pipe (5) is aligned with the upstream pipe (1), and has a length at least equal to four times its diameter (D '), this length (1') being all the greater as the desired pressure drop (ΔP ) is important. 4.- Device according to one of the preceding claims characterized in that the converging element consists of a frustoconical element (3). 5.- Device according to claim 4 characterized in that the converging element (3) comprises fixing means on the one hand, on the upstream pipe (1) and on the other hand, on the downstream pipe (5). - 6.- Device according to one of claims 4 or 5 characterized in that the frustoconical element (3) is removable. 7.- Device according to one of claims 4 to 6 characterized in that the half-angle at the top of the frustoconical element (3) is between 15 ° and 40 ° and is preferably equal to 21 ° ± 2 ° . 8.- Device according to one of the preceding claims characterized in that the diameter (D ') of the downstream pipe (5) is at least equal to 3/4 of the diameter (D) of the upstream pipe (1) and at plus 1.5 times this.