1. Patent Search
  2. Details

AIR DUCT FOR DISTRIBUTING AIR IN A GREENHOUSE

20230309465 · 2023-10-05

    Inventors

    Cpc classification

    International classification

    Abstract

    Air duct for distributing air in a greenhouse, the air duct comprising a hollow main body extending along a longitudinal axis and at least one set of vents, wherein the main body has an outer surface and an inner surface, a first end and a second end at the opposite longitudinal ends of the main body, and a segment disposed between the first end and the second end extending over substantially the entire length of the main body, wherein the cross-sectional area of the main body in this segment decreases towards the second end, wherein the vents belonging to a respective set of vents are distributed at intervals over substantially the entire length of said segment, and wherein at least said segment of the main body is made from plastic.

    Claims

    1-25. (canceled)

    26. An air duct for distributing air in a greenhouse, the air duct comprising a hollow main body extending along a longitudinal axis and at least one set of vents, wherein the main body has an outer surface and an inner surface, a first end and a second end at the opposite longitudinal ends of the main body, and a segment disposed between the first end and the second end, wherein the cross-sectional area of the main body in said segment decreases over the whole length of this segment towards the second end, and wherein the vents belonging to a respective set of vents are distributed at intervals over substantially the entire length (L2) of said segment, wherein at least said segment of the main body comprises plastic.

    27. The air duct according to claim 26, wherein at least said segment of the main body is made of air-impermeable plastic film.

    28. The air duct according to claim 26, wherein the vents of a respective set of vents in said segment are arranged on a geodesic line when the air duct is used as intended.

    29. The air duct according to claim 26, wherein the cross-sectional area (A) of the segment is configured to maintain uniform static pressure along the length of the segment.

    30. The air duct according to claim 29, wherein the cross-sectional area is determined by equation (1): A A L = { ( 1 + fL 2 ⁢ D L ) ⁢ ( x L ) 1 / 2 - fL 2 ⁢ D L ⁢ x L } 2 ( 1 ) and factor f used in equation (1) to calculate the change in cross-sectional area along the segment is additionally based on equation (2): f = 0.25 log ⁡ ( ε / D 3.7 + 5.74 Re 0.9 ) 2 ( 2 ) with f=friction factor, ε=absolute roughness coefficient, D=cross-sectional diameter of the segment, Re=Reynolds number.

    31. The air duct according to claim 26, wherein the vents are equally spaced from one another, wherein the interval (d) between adjacent vents of a respective set of vents is between 5 mm and 100 mm, measured from the respective centers of the vents.

    32. The air duct according to claim 26, wherein the air duct comprises two sets of vents, wherein the two sets are arranged substantially mirror-symmetrical to a median longitudinal plane (P) of the air duct.

    33. The air duct according claim 26, wherein the vents are configured as nozzles protruding from the outer surface of the segment.

    34. The air duct according to claim 33, wherein the nozzles each have a substantially circular air inlet opening with an inlet diameter (d1) at the level of the main body's outer surface, a substantially circular air outlet opening spaced substantially parallel to said air inlet opening and having an outlet diameter (d2), and a perpendicular distance (h) between the air inlet opening and the air outlet opening, wherein the air inlet opening is larger than the air outlet opening and wherein the ratio between the perpendicular distance (h) and the outlet diameter (d2) is between 0.5 and 3.

    35. The air duct according to claim 33, wherein the inner surface of each nozzle comprises a cylindrical region with a substantially constant inner diameter and a transition region in which the inner diameter increases towards the main body, wherein the inner diameter of the cylindrical portion corresponds to the diameter (d2) of the air outlet opening and wherein the radius (r) of said transition region is between 0.05 and 0.5 of the outlet diameter (d2).

    36. The air duct according to claim 33, wherein at least the segment and the nozzles, are formed in one piece.

    37. The air duct according to claim 26, wherein the main body comprises a plurality of segments which are connected to each other end-to-end in a sealed manner or are connectable to each other end-to-end in a sealed manner.

    38. The air duct according to claim 26, wherein the air duct further comprises a hollow enclosing body having an outer surface and an inner surface, the enclosing body enclosing the main body at least partially in the direction of the longitudinal axis of the main body, wherein the main body and the enclosing body are connected to each other via at least some of the nozzles of the main body, wherein the nozzles protruding from the outer surface of the main body are open into vents in the enclosing body and/or extend through vents in the enclosing body and protrude from the outer surface of the enclosing body in such a way that the interior volume of the main body is in fluid communication with the environment via the nozzles.

    39. The air duct according to claim 38, wherein the enclosing body is comprised of plastic.

    40. The air duct according to claim 26, wherein the nozzles are fixed to the enclosing body by means of at least one of a form-locking connection and a joining method.

    41. The air duct according to claim 26, wherein the connection between each of the nozzles and the enclosing body is formed to be gas-tight.

    42. A method for manufacturing an air duct according to claim 26, wherein the method comprises: i) providing a heat-sealable film of thermoplastic material; ii) welding said film to form at least one of a tapered main body having a first end and a second end and a segment of a main body having a first end and a second end, wherein the cross-sectional area (A) of the main body or the segment decreases from the first end to the second end; and iii) creating vents in the film, either before or after step ii).

    43. The method according to claim 42, wherein the vents are configured as nozzles which are created by the following steps: feeding said film to a vacuum roller comprising dimples; sucking said film into the dimples on the roller to form plastic deformations protruding from the side of the film facing the roller, wherein the plastic deformations thus obtained have substantially the shape of the dimples, and wherein the vents in step iii) are created by punching out the bottom of said deformations.

    44. The method according to claim 42, wherein the vents are configured as nozzles which are created by the following steps: providing prefabricated nozzles comprising a substantially circular air inlet opening with inlet diameter (d1), a substantially circular air outlet opening with outlet diameter (d2), wherein the air outlet opening is spaced substantially parallel to said air inlet opening at a perpendicular distance (h), wherein the inlet opening is larger than the air outlet opening and wherein the ratio between the perpendicular distance (h) and the outlet diameter (d2) is between 0.5 and 3; creating a plurality of holes in the film; inserting the nozzles into said holes, with the air outlet opening first, from the film side that is or will become the inner surface of the main body; fixing the nozzles to the film by at least one of a form-locking connection and a joining method, wherein said latching element is pushed onto the respective nozzle from the film side that is or will become the outer surface of the main body.

    45. The method according to claim 42, wherein the vents are configured as nozzles which are created by feeding the film to a forming device for producing plastic deformations in the film, wherein the vents in step iii) are created by punching out the bottom of said deformations.

    46. The method according to claim 45, wherein the film is fed to the forming device folded so that several layers of the film are simultaneously deformed from one side of the folded film.

    47. The method according to claim 43, wherein the method additionally comprises: iv) providing a further heat-sealable film of thermoplastic material; v) forming a hollow enclosing body with said further heat-sealable film of thermoplastic material enclosing the main body at least partially in the direction of the longitudinal axis of the main body; vi) connecting the main body and the enclosing body via at least some of the nozzles of the main body; and vii) creating vents in the enclosing body, the spacing of the vents from one another and the size of the vents in the enclosing body corresponding essentially to the spacing of the nozzles from one another and to the outer diameter of the nozzles at the nozzle outlet opening in the main body, either before or after step vi).

    48. A greenhouse comprising at least one air duct according to claim 26.

    49. A method for distributing air with an air duct according to claim 26 in a greenhouse, the method comprising the steps of: providing conditioned air with at least one of pre-determined humidity and pre-determined temperature at the first end of the air duct; conveying said conditioned air from the first end in the direction of the second end of the air duct, in particular by means of an electrically powered ventilator arranged upstream of the air duct; and supplying said treated air into the growing section of a greenhouse via the vents, whereby the air flow exiting through the vents is essentially the same between all vents.

    50. Use of an air duct according to claim 26 for distributing air in a greenhouse.

    Description

    [0087] Embodiments of the invention are further described in more detail with reference to the accompanying figures, wherein like reference signs are used to refer to the same or corresponding elements. The different views and illustrations of the embodiments shown in the figures are schematic illustrations of idealized embodiments of the invention and provided by way of example only. As such, embodiments of the invention should not be construed as limited to the particular shapes of the regions illustrated herein but are to include deviations in shapes.

    [0088] FIG. 1a: Schematic illustration of an air duct according to the invention in non-operational mode;

    [0089] FIG. 1b: Schematic illustration of an air duct according to the invention in operational mode;

    [0090] FIG. 2: Schematic illustration of a longitudinal section of a nozzle for an air duct according to the invention;

    [0091] FIG. 3: Illustration of nozzles on an air duct according to the invention;

    [0092] FIG. 4a: Embodiment of an air duct according to the invention comprising a suspension top part and one set of nozzles on each side of the air duct's main body;

    [0093] FIG. 4b: Cross section of an embodiment of an air duct comprising nozzles on each side of the air duct's main body;

    [0094] FIG. 5: Schematic illustration of a longitudinal section of a nozzle comprising retaining elements and a latching element for an air duct according to the invention;

    [0095] FIG. 6: Schematic illustration of an embodiment of an air duct comprising a fin;

    [0096] FIG. 7: Schematic illustration of a cross section of a multilayer air duct according to the invention;

    [0097] FIG. 8a Schematic illustration of an embodiment of a convection between a nozzle and the enclosing body in a multilayer air duct according to the invention;

    [0098] FIG. 8b Schematic illustration of another embodiment of a connection between a nozzle and the enclosing body in a multilayer air duct according to the invention.

    [0099] FIG. 1a shows a schematised computer design of the air duct (10) according to the invention with one set of nozzles (20) extending radially from the outer surface of the main body (11). The cross-sectional area (A) of the main body (11) tapers from the first end (14), i.e. the inlet opening of the conduit, towards its longitudinally opposite second end (15). The air duct (10) comprises three segments (17, 17′) which are connected end-to-end with a common longitudinal axis (X). In FIG. 1a, the air duct (10) is portrayed in non-operational phase, i.e. when conditioned air does not flow out of the nozzles (20).

    [0100] FIG. 1b shows the same schematic version of the air duct (10) portrayed in FIG. 1a but this time in operation, i.e. with air leaving the air duct through the nozzles (20), as indicated by the arrows. The individual segments (17, 17′) are each configured to form an extended segment with decreasing cross-sectional area towards the second end (15), and the second end (15) is formed as a closed end wall so that a substantially identical outflow pressure of all individual flows of the conditioned air from the nozzles (20) is generated, as illustrated by the same length and thickness of the arrows.

    [0101] FIG. 2 illustrates a longitudinal section of a nozzle (20) used in an embodiment of the air duct (10) disclosed herein. In this example, the nozzle (20) is integrally connected to the tapered segment (17) of the air duct's main body (11), i.e. the nozzle (20) and the main body (11) are made from one piece of material. The nozzle (20) comprises a cylindrical region (24) and a transition region (25) adjacent thereto. The cylindrical region (24) features a constant diameter corresponding to the outlet diameter (d2), i.e. the diameter of the air outlet opening (22) of the nozzle (20), whereas the cross-sectional area of the nozzle (20) increases in the transition region (25) towards the tapered segment (17) of the main body (11). The air inlet diameter (d1) of the nozzle's air inlet opening (21) is measured at the end of the radius (r). The nozzle (20) further comprises an inner surface (23) which, in this embodiment, is identical to the inner surface (13) of the main body (11). The cross-sections corresponding to the substantially circular air outlet opening (22) and the substantially circular air inlet opening (21) are spaced parallel to each other at a distance h, wherein said distance corresponds to the length of the nozzle (20) or the sum of the lengths of the cylindrical region (24) and the transition region (25), respectively.

    [0102] FIG. 3 shows a more detailed illustration of nozzles (20) connected to the outer surface (12) of the main body (11) of an air duct (10) according to the invention. The inside of each nozzle (20) comprises a cylindrical region (24) with a constant diameter corresponding to the outlet diameter (d2) of the air outlet opening (22) and a transition region (25) facing the main body (11) or a segment (17) thereof. In the transition region (25), the inner diameter of the nozzle (20) increases towards the main body (11) with a radius (r) to reach inlet diameter (d1) at the level of the main body's inner surface (13). Hence, the cross-sectional area of the air inlet opening (21) is larger than the cross-sectional area of the air outlet opening (22), wherein the imaginary planes corresponding to both openings (21, 22) are spaced parallel to each other at a distance h. The nozzle (20) may further comprise angled sections for fixing on the outer surface (12) of the main body (11), e.g. by gluing or welding.

    [0103] FIG. 4a shows an embodiment of an air duct (10) according to the invention. A cross-sectional view of the air duct (10) of FIG. 4a is shown in FIG. 4b. In this embodiment, the air duct (10) has a main body (11), the cross-sectional area of which decreases from the first end (14) to the second end (15), i.e. the closing end wall, in order to counteract the pressure loss of the supplied conditioned air which would otherwise happen along the direction of air flow through the main body (11) of the air duct (10). In this example, the tapered segment (17) extends over the entire length of the main body (11). Furthermore, the main body (11) is composed of a tapering bottom part (40) and a top part (30) with substantially constant cross-section along the longitudinal axis (X) of the air duct (10). Multiple middle parts (50) comprising nozzles (20) are arranged between the top part (30) and the bottom part (40) to form two sets of nozzles (20), one on each side of the median longitudinal plane (P) of the air duct (10) running through the longitudinal axis (X) of the air duct (10) vertically. The nozzles (20) of the respective sets of nozzles are arranged side by side with a certain regular distance (d) and in one row along substantially the entire length of the main body (11). Each nozzle (20) comprises an air inlet opening (21) and an air outlet opening (22) in fluid communication through which the air being conveyed in the main body (11) can exit into the greenhouse. The top part (30) may comprise means for mounting the air duct (10) to the underside of a plant table and/or means for suspending the air duct (10) from a suitable installation. The portrayed main body (11) of the air duct (10) can be created by connecting the top part (30), the middle parts (50) and the bottom part (40) by any known manner, for example by gluing or welding. The top part (30) is made of a rectangular plastic plate, e.g. made by extrusion of a thermoplastic polymer, and is adapted for the connection with the lower part of the worktable on which cultivated crops are placed. By way of example, bolts and rivets may be used to mound the air duct (10) to the underside of a plant table. However, the top part (30) may alternatively be connected to the ceiling of the greenhouse right above the cultivated crops or to horizontal hanging equipment in the greenhouse.

    [0104] FIG. 5 illustrates a longitudinal section of a nozzle (20) comprising retaining elements (27) and a latching element (26) for use in an embodiment of the air duct (10) disclosed herein. In this embodiment, the nozzle (20) is inserted into holes in the main body (11) from the inside of the main body (11), i.e. the nozzle (20) is pre-fabricated and attached to the main body (11) after its production. Similar to the nozzle described in FIG. 2, the nozzle (20) of FIG. 5 comprises a cylindrical region (24) and a transition region (25) adjacent thereto. The cylindrical region (24) features a constant diameter corresponding to the outlet diameter (d2), i.e. the diameter of the air outlet opening (22) of the nozzle (20), whereas the cross-sectional area of the nozzle (20) increases in the transition region (25). The air inlet diameter (d1) of the nozzle's air inlet opening (21) is measured at the end of the radius (r). The size of the holes in the main body (11) is smaller than the inlet diameter (d1) of the nozzles (20). Preferably, the insertion of the nozzles (20) through the main body (11) can be facilitated by choosing the size of the holes such that the holes are larger than the outlet diameter (d2) of the nozzles (20) and smaller than the inlet diameter (d1) of the nozzles (20). After insertion, the nozzles (20) are fixed to the main body (11) by means of a form-locking connection. In this embodiment, the nozzle (20) is attached to the main body (11) with a snap lock convection using retaining elements (27) and a latching element (26). In the present example, the latching element (26) is formed as a ring that can only be pushed onto the nozzle (20) in one direction, i.e. from the side of the air outlet opening (22). The retaining elements (27) are designed as barbed hooks that prevent the ring from sliding off the nozzle (20) and the nozzles (20) from falling off the main body (11).

    [0105] FIG. 6 illustrates an embodiment of an air duct comprising a fin (60) for suspending the air duct (10). In this embodiment, the air duct (10) comprises a main body (11) with a first end (14) and a second end (15) which extends along a longitudinal axis (X). Here, the length of the vent or nozzle containing segment (L2) corresponds to the overall length of the main body (L1). Hence, the main body (11) has a substantially circular cross-section which decreases from the first end (A1) to the second end (A2). Multiple nozzles (20) are arranged in one row along the main body (11), wherein the nozzles (20) are evenly spaced at intervals (d). In the main body (11) further comprises a fin (60) for suspending the air duct (10). The fin (60) extends in longitudinal direction (X) of the main duct (11) and comprises a plurality of reinforced apertures (61) which are disposed along the fin (60). The fin (60) and the main body (11) are formed in one piece.

    [0106] FIG. 7 shows a cross section of a multilayer air duct as disclosed herein. The air duct comprises a hollow enclosing body (71) with an outer surface (72) and an inner surface (73). In the present example, the enclosing body (71) encloses the main body (11) over substantially the entire length of the main body, i.e. from the first end to the second end of the main body, and tapers like the main body (11) such that a gap (18) is formed between the inner surface (73) of the enclosing body (71) and the outer surface (12) of the main body (11). In the present example, the nozzles (20, 20′) protruding from the outer surface (12) of the main body (11) extend through vents (74, 74′) in the enclosing body (71) and protrude from the outer surface (72) of the enclosing body (71). The interior volume of the main body (11) is in fluid communication with the environment (100) via the nozzles (20, 20′).

    [0107] FIG. 8a shows a more detailed schematic illustration of an embodiment of connection between a nozzle (20) and the enclosing body (71) in a multilayer air duct (10) as disclosed herein and in a longitudinal section along the dashed line B-B in FIG. 7. In the embodiment shown in FIG. 8a, both the main body (11) and the enclosing body (71) are made from a substantially air-impermeable plastic film, e.g. a polyethylene film. The nozzles (20) are inserted through vents in the main body (11) and fixed to the main body (11) by means of a snap lock connection consisting of a ring acting as latching element (26), which ring is brought into effective connection with a barb acting as retaining element (27) for the latching element (26). Similarly, the nozzles (20) are inserted through vents (74) in the enclosing body (71). The diameter (d3) of the vents (74) in the enclosing body (71) corresponds approximately to the outer diameter of the nozzles (20) or is slightly larger in order to facilitate the insertion of the nozzles (20) through the respective openings (74) in the enclosing body (71). The nozzles (20) are then fixed to the enclosing body (71) by means of a snap lock connection consisting of a second ring acting as latching element (28) and a second barb acting as retaining element (29), the barb being arranged on the nozzle (20). Of course, it is also conceivable that the nozzles (20) protrude from the outer surface (72) of the enclosing body (71) and that the enclosing body (71) is connected to the nozzles (20) in some other way, in particular by bonding or welding.

    [0108] FIG. 8b illustrates another embodiment of a connection between a nozzle (20) and the enclosing body (71) in a multilayer air duct (10) as disclosed herein, wherein the nozzles (20) protruding from the outer surface (12) of the main body (11) open into vents (74) in the enclosing body (71). In this embodiment, the enclosing body (71) is attached to the end of the nozzle (20) facing away from the main body (11), in particular by gluing or welding. Of course, it is also conceivable that the main body (11) and the nozzles (20) are made in one piece and that the enclosing body (71) is subsequently attached to the nozzle outlet opening. The vents (74) may be prefabricated and correspond substantially to the outer diameter of the nozzles (20), or they may be produced after the enclosing body (71) has been attached to the nozzles (20), for example by punching or piercing the enclosing body (71) at the desired locations.

    [0109] The operation of the air duct (10) is as follows: Conditioned air, i.e. air having a pre-determined air humidity and/or temperature, is supplied to the first end (14) of the main body (11), for example by means of a ventilator powered by an electric motor (not portrayed). The conditioned air is conveyed by the ventilator through the main body (11) in the direction of the second end (15) of the main body (11). Given the narrowing diameter of the main body (11), the conditioned air flows through all nozzles (20) under similar pressure which ensures identical cultivation conditions for all crops placed in the cultivation space of the greenhouse, regardless of the distance of individual crops from the first end (14) of the air duct (10).

    [0110] In general, the main body (11) can have any cross section. However, from a production perspective, circular, elliptical, square or rectangular cross-sections are feasible and circular cross-sections are preferred. The nozzles' (20) air outlet diameter (d2) is preferably comprised between 1 cm and 5 cm and the total sectional area of all the nozzles (20) is bigger than or equal to the output sectional area of the ventilator driving the conditioned air in the air duct (10). The nozzles (20) may be manufactured from any suitable material, including plastic or metal. The conduit is manufactured from plastic, particularly form gas-tight plastic film. Self-supporting stability of the conduit is particularly important when the air duct (10) is not suspended but rather placed on the ground. For this reason, the main body (11) may be fitted with form-retaining elements (not shown) which will prevent the collapse of the main body (11) when not in use, for example by stretching the main body (11) or pressing against the interior surface (12) of the main body (11).

    [0111] In the following, the technical effect of the present invention shall be further illustrated by two concrete examples of application, without limiting the invention to the values given in the examples:

    EXAMPLE 1

    [0112] Air ventilation into the cultivation space of a 16 meter long greenhouse was performed using a 15 meter long experimental air duct suspended by its suspension part under an equally long worktable full of tomato nursery plants. The cross-section of the first end of the air duct was 0.63 m.sup.2, and the cross-section at the closed second end wall was 0.35 m.sup.2. At each lateral side of the main body, a number of simple holes, each having a cross-section surface of 3.14 cm.sup.2, was cut from the main body. The regular distance between these holes was 20 cm. Air with a relative humidity of 80% was blown in the first end of the air duct using an electrically powered ventilator. The level of humidity and temperature of the cultivation space was measured using LUTRON HT-3009 LUTRON HT-3009 hygrometers placed in 1 meter distances among the tomato plants. The electricity consumption was recorded over one hour of operating the air duct.

    EXAMPLE 2

    According to the Invention

    [0113] Air ventilation into the cultivation space of a 16 meter long greenhouse was performed identically as in the above example 1 using a 15 meter long experimental air duct suspended under an equally long worktable full of tomato nursery plants and under identical air ventilation conditions. Contrary to the previous example 1, the simple holes of the air duct were equipped with nozzles as described herein having a circular cross-section at the air inlet opening of 3.14 cm.sup.2 and a length of 3 cm. The cross-section at the vent was slightly smaller compared to the cross-section at the air inlet opening. During one-hour operation of the ventilator and under identically humid air ventilation into the cultivation space of the greenhouse on the level of tomato nursery plants (measured in the same manner as in example 1), savings of 52% of electricity consumed by the electric motor of the ventilator was achieved in comparison to example 1.