NL1038219A - Arrangement for even distribution of gaseous material in a spatial area. - Google Patents

Description

ARRANGEMENT FOR EVEN DISTRIBUTION OF GASEOUS MATERIAL IN A SPATIAL AREA

The present invention relates to an treatment arrangement for gas or gaseous material such as air, in particular conditioned gas, for use in spatial area’s such as buildings and cabins, in particular spaces for use by organisms such as men, animal and plants, especially but not limited to greenhouses, effecting circulation and/or re-circulation of said air or other gaseous material from the spatial area to be controlled. In case of conditioned air, typically temperature, humidity and, in case of greenhouses, level of Carbon-dioxide (C02) is controlled, without excluding other forms of conditioning or additives.

Such a treatment arrangement is known from the “Priva re-circulation concept” as commercialised by PRIVA AGRO®, and as schematically represented by annexed figure 1. The re-circulation concept is a combination of ventilators to which air hoses are coupled so as to cause movement of the air in the lower area of a greenhouse. The hoses or tubes run in parallel at ground level, mostly below a crop row defined by a substrate gutter, and each serves to distribute conditioned, at least new air, preferably in a dampened manner, to one or more rows of crop. It is conceived to promote quiet movement of air at toe lower parts of a crop, to save on energy costs by bringing relatively warm air of the upper areas down; to dry especially lower parts of crops and so to limit growth of mould; to promote cooling during night time; to improve the micro climate for crops and to activate these and, in general, for temperature and humidity equalisation in toe greenhouse. The known re-circulation arrangement may be devised with a vertically extending air entry duct, either with or without a valve directing thereto, so as to directly take in relatively warm air if so desired.

With air tubes often included below toe crop in a greenhouse, rather than in an upper section of the greenhouse, hall or other building, the air ducts are included in series or parallel below the object to be provided with conditioned gaseous material, which in the known example is the crop. The result is a movement of air below toe object or crop, which latter in a greenhouse is often inducted at some height, typically about 50 cm above floor level. A comparable effective level is true for spatial area's like an office room, where people tend to sit at this height, and where toe important exchange instance of toe organism, the human longs, together with the human skin and head, are situated and accessed above said level. The movement of gas includes a slow vertical movement of air through the spatial area, in particular through the crop in the case of a greenhouse, resulting in equalisation both in vertical and horizontal direction, of temperature and other conditioned gas or air factors between the plants. The airstream in this example of a known treatment system causes a drying effect by which moulds have a lesser chance to germinate.

The tube of the known system causes complications for the otherwise seemingly relatively simple concept and design of re-circulating air, in that without such tube, there would be no guidance and direction for the air to be re-circulated, i.e. activated by the ventilator. On the other hand the tube causes complications due to pressure differences at the beginning and end thereof, and due to temperature change over it’s length by exchange of heat with the local atmosphere of the tube.

By application of the above, known re-circulation concept, the magnitude of heating capacity in a building, e.g. as normally applied in the lower section of a greenhouse, may be reduced. Reason for this is that the ventilators and air ducts partly or wholly take over the functions of causing movement of air, in greenhouses in particular in the lower crop section so as to prevent the occasion of a “dead atmosphere” locally. Secondly, the function of drying the crop is taken over from the heating action as conventionally performed by movement of introduced, ventilated air.

The known circulation system however comes with a disadvantage that the air thus distributed appears to spread unevenly. In a greenhouse a crop ventilated with the known system appears to mature unevenly, which is disadvantageous and quite contrary to the goal of evening various climate parameters of a building, in particular of a greenhouse as in the actual example. In practice, depending of the length of an air duct one or more sections in the crop area to be serviced by a duct appeared where the crop matured at a different stage from other sections. The difference in stage of maturing could be more than a week per crop section. In one example a section near the beginning of the re-circulating duct and near a lateral end of an area to be serviced by a re-circulating duct appeared to develop considerably slower than plants in an end section of the area serviced by such duct.

Where the re-circulation principle involves relatively simple mechanics, the system is yet highly cost effective, both as to promise of energy savings and as to promise of improved crop yield and evenness of development The latter circumstance being of equal or even more importance as crop yield, given logistic complications and costs that may occur in case of spread maturing of plants in a crop to be harvested. It is remarked that where crop yield is mentioned, well-being may as well be interpreted, as for humans or animals in a building or cabine, in which latter cases areas of less comfort may then be experienced.

The present invention solves the above problem, at least strongly improves the result of the known re-circulation system, by providing an exit opening of said ventilation outlet duct enveloped by a ventilation air receiving chamber, said chamber being provided with one or more exit openings for passage of air received in said chamber.

The solution according to the present invention confirmed a hypotheses underlying the invention that ventilation air exited the known systems under an angle that varies with the lengthwise position of the exit opening in the ventilation duct. In this respect it was observed that at exit openings close to the ventilator of the system, the air exited under an acute angle as it were, rather than transversely as near the end of the duct due to pressure and kinematic energy of the air ventilated. Where it was observed that such phenomenon could be solved on the basis of a physical law indicating that pressure is reduced with the second power by decreasing the air speed by increasing the radius of the ventilation tube, it was also observed that in practice space and costs of the system may be limiting to such solution. With the presently conceived solution of a receiving or intermediate chamber, only limited or local increase in diameter is required and at low cost, for a very good effect as to evenness of distribution of air by the system.

It is remarked that the principle of taking out a kinetic or dynamic component of supplied air is explicitly known by Dutch patent publication 6913348. Rather than so/called impulse, alternatively denoted induction ventilation, this arrangement applies so-called displacement ventilation. It hence, in line with the later teaching of EP1464 219 applies a floor of evenly distributed openings for creating an evenly ascending air blanket. Though advantageous, this kind of arrangement is highly expensive. Moreover, the ventilation systems known by these publications, as much as the system known from e.g. US4028847 are not applicable to the presently claimed ventilation arrangement, since they are dependent on structures that are not part of the ventilation arrangement and hence can not be commercialised independent from e g. a building design or a crop support and or logistics arrangement Hence these known systems are in addition difficult to implement at a later stage than at construction, i.e. as after-delivery for existing green houses or improvement thereof.

It is further remarked that above said EP publication indicates the problems of unequal temperature distribution in crop areas and that of space requirement by a ventilation system. It proposes an air supply tube of flexible material of either foil or 'gewebe'. It is remarked that the latter is normally to applied in case a displacement ventilation is desired and is hence in line with the displacement ventilation effect created by the table formed floor of the system. The present invention strives for an easily, afterwards implementable, independent, space minimised and relatively inexpensive ventilation arrangement. This is in accordance with the present invention realised by realising the intermediate chamber or chambers as part of tho tube, at least of the ventilation arrangement, and by producing both the inner tube and the outer tube, i.e. at least the wall material for the chamber or chambers, in a foil like material. The air exit openings of the system, i.e. for entry into the area to be ventilated, are equally distributed over the length of a tube, and are of such diameter that air travels sufficiently far in the area in order to meet air supplied a parallel air supply tube of the arrangement

With the present design, it is in an at hindsight remarkably simple, yet technically and economically favourable manner achieved that a dynamic, i.e. kinematics component of the ventilation air is taken out leaving the ventilation air, i.e. in the receiving chamber with only static pressure as a means of exiting the chamber. In this manner ventilation air will leave a chamber in a uniform manner, i.e. independent of the longitudinal position of the ventilation air exit opening and chamber with respect to the duct. An insight underlying the present invention is that the application of a diamber to the known arrangement, serves to separate two functions thereof, so that the inner air exit openings may be design property for realising an equal distribution of air over the full length thereof. The design of the outer air exit openings serves to determine a desired travel distance. With the separation of functions in two structural parts now, at relatively low cost and without undue effort, an even distribution of air is realised, which takes the form of an evenly developing and maturing crop.

According to the invention, such air receiving chamber may either be devised for a single exit opening of the ventilation duct, but also for two or more of such openings in common. In this respect, a foil attached with room over an exit opening, to the wall of the ventilation duct forms a first embodiment The foil may however also circumscribe the duct wholly or in part so as to form a chamber for two oppositely disposed exit openings of the duct. In the same manner, a chamber conceived according to the invention may be made common to all exit openings by locating the duct in a second duct as it were. Yet another embodiment includes the attachment of a longitudinally extending chamber, e.g. formed through a foil, that is attached to a lateral side of the ventilation duct In this embodiment the chamber forming material, e.g. cloth or foil is sealed at a first rim situated above duct exit openings, and a second one below that. The latter embodiment is not only particularly suited for improving existing ducts, but also for new ones, in that the main construction and manufacturing process in fact may entirely or essentially be maintained.

It is further conceived that the exiting air is to be received in said chamber at least momentarily, i.e. that the air is at least partly not to pass from the ventilation duct directly via the chamber openings towards the space to be serviced. This is accomplished by either having more but smaller exit openings than in the duct part covered, or by having the centre of a chamber exit opening at a different radial location than that of a corresponding duct exit opening.

Further to the meaning of the measure according to the invention: in this way a non uniform distribution of ventilation air over the space to be ventilated by the system is effected, which in practice has proven, in contrast to repeated effect with the known, none-improved ventilation system, to effect a uniform development and maturing of ventilated crop.

It is remarked that the present invention all the more becomes relevant with more elaborated re-circulation systems such as known from the ClimateOptimizer™ system as commercialised by Applicant. Such systems include a valve allowing intake of either one or both of air external and air internal to said space to be ventilated. In this manner either of both of temperature and humidity of the air re-circulated may be influenced by the addition of outside air. The system may include a temperature control device for additionally influencing air temperature to be vented to the duct. It may be evident that with a such, more elaborate re-circulation system, the adverse or positive effects as discussed in the preceding on organic well being in a building will be even greater. A proper manner of supplying ventilated air to the space to be ventilated by the system is therefore all the more of importance. The magnified effect of such elaborated system may in particular become evident from a greenhouse environment, where plants are or crop is continually and without option of change of location, subjected to the ventilation output of the system.

The invention will now, by way of example be further elucidated along a drawing, in which:

Figure 1 represents a schematic, vertical section of the traditional system in the longitudinal direction of a ventilation duct thereof;

Figure 2 is a corresponding view prior art re-circulation system provided with a vertically upwards stretching suction or inlet duct, further provided with an inlet and valve for taking in or mixing with external air;

Figure 3 is a schematic top view of a ventilation system under consideration, illustrating the adverse effect of it’s design;

Figure 4 is a corresponding view and effect illustration of a ventilation system improved according to the invention;

Figures 5 to 10, by a schematic cross sectional view thereof, illustrate various embodiments of a system provided with an air receiving chamber at an air exit opening in the ventilation duct;

Figure 11 provides a longitudinal section of an end part of the ventilation or air supply tube according to an embodiment of the invention;

Figure 12 is a perspective view of an embodiment according to the invention wherein the invented tube may be hung by openings in an radial outward directed extension of the tube;

Figures 13A and 13B illustrate so-called displacement ventilation and impulse or inducement ventilation respectively, which latter is applied by the present invention.

In the figures, corresponding constructive elements are referred to by a single reference sign.

Figure 1 illustrates a first and prior art re-drculation system 1 subject to improvement according to the present invention. It includes a ventilator or ventilator device 2, for blowing ventilation air into a duct 3, and to provide the air or gas to be removed with a pressure. Duct 3 is provided with exit openings 4 and preferably closed at its remote end. Without said duct, the objective of the system, to evenly re-distribute, and in fact virtually also solely to re-distribute would not be reached. The ventilator 2 in this example freely takes in air from the space in which the system is located for operation. The exit openings 4 are in this example located laterally, to provide air to a crop 5 with plants 6 from below, and at mutually pressure dependent distances so as to compensate for uneven amount of gas exit over the length of the tube. The distance between the openings 4 narrows with longitudinal position towards the duct end remote from the ventilator 2 so as to realise exit of even amounts of air over the tube length. The crop 5 in this example is provided in a typical greenhouse situation having gutters 7 for receiving plant roots and for providing water and possibly nutrition to the crop. The system may be provided with a vertically extending duct for taking in air from elevated levels with different relative gas factors, e.g. with a higher or lower temperature, so as to more directly cause an uniform gas factor profile, in particular air temperature profile in the space to be ventilated.

Figure 2 illustrates an elaborated version of the re-circulation system 1 to be improved by the present invention. The elaboration consists in a possibility to treat the air to be re-circulated by mixture with outside air, or to operate the system as a ventilation system only, i.e. to take in outside air only. To this end the system 1, connected to the ventilator 2, is provided with a valve 11 opening to either one or in a controllable ratio to both of an inside air inlet 10 and an outside air inlet 12. The inlet 12 to this end protrudes through an opening in a space delimiting wall 13. The system 1 may be provided with a filter 14 and a temperature control unit 15, in this case a heating or cooling system. It may be evident from the examples of figures 1 and 2 that in principle the ventilation duct may in other or same applications as well be included at any other appropriate level, including upper sections of a building or cabin.

Figure 3, along a situation in a greenhouse illustrates a problem of tihe known recirculation system. It was found that with this system, at least temperature, however also C02 and air humidity tended to be spread uneven over the length of the space to be served by the system. It appeared that temperature Tr1 to the right side of the duct, and TH to the left side of the duct as taken in the direction of air ventilated in the duct 3, would be lower than that of Tr2 and TI2 at the lengthwise centre of the space, which temperature in turn would be lower than that of Tr3 and TI3 near the end of the building, at least space to be re/circulated. Especially, in the areas Al and Ar near and generally laterally the ventilator 2, the crop appeared to develop relatively slow. It was concluded that by a high air speed in the beginning of the tube 3, the dynamic pressure of the ventilation air would be very high, so that ventilation air would tend to leave openings 4 of the duct under an acute angle, only gradually becoming a desired transversely oriented direction of exit of the openings 4. This observed phenomenon was interpreted to cause pressure differences in the system surrounding space, which in turn would cause differences in temperature and concentration of C02. in turn such pressure differences are perceived to be the cause for probable air movement is the space to be ventilated in a disadvantageous manner, causing said low temperature areas Al and Ar.

Figure 4 illustrates the effect and one possible embodiment of a solution in accordance with the present invention. In this respect, the ventilation air supply duct 3 is provided with an at least partially surrounding air receiving chamber 16. The chamber 16 is in this example realised by a wall 17 entirely surrounding the duct 3. The wall is generally composed of the same material as that of the duct, generally a foil or foil like material known per se. The air receiving chamber 16 is provided with exit openings or ports 18. These are included in a manner so as at least not to entirely directly let the air of an exit 4 of the duct 3 pass such port 18. One measure of at least largely accomplishing the latter is, as indicated schematically, at to have the openings included lengthwise interlaced. In accordance with another measure, which is either simultaneously or alternatively applied, the ports 18 are either included at higher or lower level than that of the exit openings of the duct, in particular to have the ports 18 included at a radial different position relative to the core of the duct 3. In the same manner according to a third measure the ports are composed of a plurality of openings that are each smaller than that of an exit opening 3 in the duct. It may be taken from the illustration that with the principle measure in accordance with the present invention, a so called dynamic pressure or pressure component as apparently exists in the part of tube that is closest to ventilator 2, is transferred into a static pressure, allowing the gas to be ventilated in a uniform manner, transverse to a port 18 in a receiving chamber or duct 16.

The figures 5 to 10 illustrate some of a plurality of possible embodiments in accordance with the present invention. Where the embodiments illustrated are all of the kind “tube in tube” created chamber, the invention also encompasses all variations of the kind “patched” chambers, e.g as in figure 10. According to the latter, a piece of foil or other tube wall material, is attached to the tube exterior in a manner leaving sufficient room around one or more exit openings for creating an air receiving chamber. Where a plurality of openings 3 is covered, this may be lengthwise of the duct 3,extending over part of whole of it’s length, but may also be cross-wise, e.g. semi-circular as taken in cross section, however covering both of two laterally opposite exit ports 3. In an embodiment of the same kind a chamber may also be formed to cover only one exit opening at a time. In any embodiment only part rather than all of the exit openings may be covered, thereby improving the duct by covering only those exit openings with clearly problematic type of exit of gas. It is further remarked that in case of "tube in tube” embodiments of the proposed improvement, the indicated embodiments are schematic as to their diameter in that in practice the inner tube will mostly be of a diameter, at least cross section of a magnitude close to that of the outer tube, certainly significantly larger than half of the latter.

Figure 5 illustrates a simple “tube in tube’ concept in the sense that inner tube 3 is not supported within outer tube 17, i.e. is within outer tube 17, freely supported by a floor of the building to be ventilated. In this respect a ventilation system according to tine invention may alternatively be supported by a hanging support 19 as in figure 6, allowing the inner tube 3 to be hung a certain level, e.g. centralised within outer tube 17. The support 19 may be extended upwards outside the outer tube to also form of hook-element for supporting the tube in a hanging manner.

Figures 7 and 8 illustrate embodiments composed of a single piece of foil as taken in cross section. In figure 7 the foil, although another staring point on the outside may as well be chosen, starts at the vertical internal connection of the duct foil, to pass inwardly down and to the left to pass circularly to said vertically extending connection again, forming the inner duct 3, to subsequently form the outer duct 17 by folding to the right hand side first, to circularly pass around the inner tube 3, to connect again to the first end of the foil. Support elements 19 may be applied in a manner corresponding to that of figure 6, preferably included between the two vertically extending foil parts.

The design according figure 8 also departs from a single sheet of foil that is made circular by connecting the edges of the foil. Part of the foil is folded inwards to form a inner tube 3 near the upper side of an outer tube, while maintaining an outwardly protruding rim 20. This rim illustrated along perspective view of figure 12, and used for sealing the tubes and for suspension of the tubes to a ceiling in a building or a structure such as for supporting plants as in a greenhouse. To this end the rim is preferably provided with support eyes 21. The tube in tube design has the additional advantage of thermally isolating as it were the inner tube, which supports evenness of distribution of heat or cold.

The embodiment according to figure 9 also departs from the concept of integrating a tube support, in particular support eyes in the tube design, more in particular to realise such support, either or not with support eyes, in the foil material. In this case, rather than departing from a single sheet of foil, two tubes, tube Ta and tube Tb, are applied, each forming a “chamber”, and together forming an inner tube. These tubes Ta and Tb may each either be manufactured from a single sheet of foil, or may be produced as circular, i.e. with endless material as taken in cross section.

Figure 10 illustrates yet another, in itself relatively simple to accomplish embodiment in accordance with the invention, particularly suited to improve already installed ventilating systems. In this embodiment, a gas receiving chamber is realised by means of a patch, i.e. in the form of a piece of foil curved over a gas exit opening 4, and attached to the duct 3 around said opening. The chamber may in accordance with preference as well be formed by an elongated sheet of foil, extending over part or whole of the duct 3, i.e. over a plurality of exit openings 4. In the present example such patches are included at opposed sides of the main duct, so as to form ear-like parts thereof.

Figure 11 illustrates an end part of the tube, in accordance with an embodiment wherein tho inner tube, apart from being provided with one or more gas exit openings, is designed closed. In the depicted embodiment the inner tube is made to end directly in the space to be ventilated. In the known embodiment this end of the ventilation duct 3 is designed to be closed, not in the last place because it often may end near a wall part or a walk way. It is, especially in the context of the present new system, however preferred, now that it has been recognised that a dynamic pressure component of ventilated gas is to be controlled towards a gas with static pressure component only, and since also a very satisfying solution has been found to realise this new insight, to still have at least some dynamic pressure component in the ventilator air duct 3. To this end the closed end of the inner tube 3, is in the present design provided with one or more exit openings. These exit openings may, but not necessarily always, be provided with one or more own or common gas exit diambers. In a construction according to the present invention, especially with the measure according to present figure 11, the gas exit openings 4 may be favourably be distributed equidistant rattier than a pressure dependent distribution of mutual distance over the length of the tube as was common in the known ventilation outlet duct

Figure 12 is a perspective schematic view of a tube according to the invention, in an embodiment provided with an integrated support part, in particular a rim 20 made of tube forming material, more in particular a rim provided with support eyes 21. The support eyes 21 may e.g. conveniently be applied for connection with fixed or intermediate hook-elements. It is remarked that such kind of rim, with openings or not may in accordance with yet a further elaboration of the present invention be inducted as a separately formed part, preferably of the same kind of material as the ventilating duct 3, glued or attached otherwise to toe tube for the purpose of supporting toe same. Such part comprises a material sheet extending longitudinally over part or whole of the ventilating duct, and provided with a central fold for forming the rim and lateral flaps for gluing or other attachment to toe ventilating tube 3. Espedally for toe particular application of the system in a greenhouse, a gas outlet tube may be provided with more that one rim 20, e.g. two, so as to secure these rims to lateral sides of a crop support such as gutter 7.

Figure 13A is known from 'luchtbehandelingstechniek 3', 1997, published by Intechnium, The Netherlands, and illustrates the known per se principle of displacement ventilation, as e.g. also known from the Rehva Guidesbook 1, a Dutch abstract of which is mentioned in ISSO-info nr. 26 of 2004. On page 8 of toe latter the advantage of energy efficiency of this type of ventilation is explained by a phenomenon of temperature layering, so that 'air of a higher temperature may be introduced at maintained cooling capacity'. For creating a so-called air blanket, a very large number of regularly distributed, small openings is desired. Figure 13B illustrates the so-called impulse or inducing ventilation which has in too present application been applied. Since in practice toe ventilation tubes are to be included at a pre/defined mutual distance, toe air released by the ventilation tube according to toe present invention is to move over a lateral distance of about the pitch between the tubes of a typical ventilation arrangement. The distance over which it travels is determined by the diameter of the air exit opening. The effect of this type of ventilation is turbulence, caused by a kernel of exiting air, indicated by the tapering conus shape in fig. 13B, decreasing in speed which is taken over by the surrounding, otherwise still standing air. The turbulence effect continues as a wide spreading conus, also indicated in the figure, and determines the mutual distance between the air exit openings of the tube, in casu of the chamber or chambers thereof.

The invention, apart from the preceding, relates to all details in the figures, for as far as immediately and equivocally deducible by a person skilled in the art, to all details provided in the following set of claims.

Claims (19)

Ventilation device comprising a plurality of ventilation outlet ducts, for ventilating a structural space such as a building, cabin or part thereof, in particular for ventilating a greenhouse, which comprises an inlet for gas or gas-like material such as circulate air in said space, connected to a fan for supplying ventilation gas to a ventilation outlet tube which is provided with a wall of foil-like material, which extends in the spatial area to be ventilated, and is provided with a plurality of outlet openings each of which is smaller in cross-section than that of the ventilation outlet tube, and which air is supplied to the space to be ventilated via a gas receiving chamber which in turn is provided with exit openings to the space to be ventilated, characterized in that the chamber is part forms of the ventilation device, and is provided with a wall of foil-like material, which is against or against the tube is fitted. Device as claimed in claim 1, characterized in that a gas receiving chamber, then gas receiving chambers, is arranged exclusively over a first part of the ventilation outlet duct. 3. Device as claimed in claim 1, characterized in that an exit opening in the ventilation duct is provided with a separate gas receiving chamber. Device as claimed in claim 1 or 2, characterized in that the gas receiving chamber is formed by a cloth part which is received around and over said outlet opening. 5. Device as claimed in any of the foregoing claims, characterized in that a gas receiving chamber is common to at least two exit openings in the ventilation duct. Device as claimed in any of the foregoing claims, characterized in that the chamber is formed by a construction in which the ventilation duct is accommodated in a completely surrounding gas receiving duct. Device as claimed in any of the foregoing claims, characterized in that the chamber is formed by a longitudinally extending chamber wall, fixed to one or more side (s) of the tube and covering at least a plurality of outlet openings of the tube per side. Device as claimed in any of the foregoing claims, characterized in that the total surface area of the opening in the chamber is larger than that of a related exit opening in the ventilation duct. Device as claimed in any of the foregoing claims, characterized in that the chamber comprises, per exit opening in the ventilation duct, a corresponding opening which is received at a radial position with respect to the axis of the duct, which radial position is different from that from the exit opening in the tube. Device as claimed in any of the foregoing claims, characterized in that at least for a part of the ventilation duct, a chamber per exit opening in the ventilation duct, comprises a corresponding opening which is accommodated at longitudinally shifted position with respect to this exit opening. Device according to the preceding claim, characterized in that the sleeve and the chamber, taken in cross-section, are formed from a single part of foil material. 12. Device as claimed in any of the foregoing claims, characterized in that said ventilation duct is embodied by two tubes which are mutually connected at opposite locations, each tube being received in order to form a chamber or one or more room parts, the two pipes with mutually facing sides form an inner ventilation duct. Device as claimed in any of the foregoing claims, characterized in that an axially closed end of the ventilation duct is provided with one or more exit openings. Device as claimed in claim 12, wherein the one or more exit openings are all, jointly or individually, surrounded by a gas exit chamber. Device as claimed in any of the foregoing claims, wherein the gas outlet openings in the chamber or rooms are included, and in the ventilation outlet duct are not equidistant. Device as claimed in any of the foregoing claims, characterized in that the system further comprises one or more devices for conditioning at least one of the humidity, temperature, amount of carbon dioxide and odor of the gas to be ventilated. Device as claimed in any of the foregoing preceding claims, wherein the diameter of an inner sleeve corresponds substantially to that of an outer sleeve. A device according to any of the preceding preceding claims, wherein the radius of the inner sleeve is included in the range of 20-25 cm and the radius of the outer sleeve in the range of 1 to 10 cm larger than the radius of the inner sleeve . A building provided with a device according to any one of the preceding claims, characterized in that the building is a greenhouse, and that the ventilation outlet tube provided with a room is accommodated at or below a rooting part of plants.