NL2027656B1

NL2027656B1 - Greenhouse having an air treatment unit with perforated air tubes

Info

Publication number: NL2027656B1
Application number: NL2027656A
Authority: NL
Inventors: Adrianus Hendrikus Maria Van Der Sande Johannes; Willem De Rijke Leendert; Vermeulen Pepijn; Van Nieuwenhuijzen Arjan
Original assignee: Belua Beheer B V
Priority date: 2021-02-26
Filing date: 2021-02-26
Publication date: 2022-09-20

Abstract

The invention relates to a greenhouse (21) with a growing section (22) forthe growing of crop, and with an air supply section (23,42). A number of airtubes (25,26,27,28,29,30), extends in a length direction L in the growing section (22) and have a relatively impermeable first segment (26i, 28i‚30i) and a permeable second segment (26p, 28p‚30p). The tubes are arranged in pairs with a ﬁrst tube (26,28,30) having an impermeable first segment (26i, 28i‚30i) and a permeable second segment (26p, 28p‚30p) and a permeable second tube (25,27,29) that extends adjacent the ﬁrst segment (26i, 28i‚30i) ofthe first tube (26,28,30). In this way the air transported through the longertube can be supplied at a relatively high flow rate and is prevented from heating up to undesired levels. The invention also relates to a greenhouse with an external air treatment chamber.

Description

Greenhouse having an air treatment unit with perforated air tubes Technical Field The invention relates to a greenhouse comprising a growing section for the growing of crop with an air supply unit extending in a width direction, a number of air tubes, with an inlet in communication with the air supply unit and extending in a length direction in the growing section, the tubes comprising perforations for blowing air from the air supply unit into the growing section.

The invention also relates to a greenhouse having an air treatment chamber and to an air tube for use in a greenhouse. Background of the invention In greenhouses the sunlight entering the growing section causes a rise in temperature of the interior and results in evaporation of water through the leaves of the crop. In order to remove excess heat and moisture, the greenhouse is ventilated. Ventilation systems are known in which air is blown into the growing section through perforated flexible or rigid tubes. These tubes cause an even air flow at the crop that is situated in beds forming parallel rows in the length direction of the greenhouse. The air blown over the crop comprises freshly admitted outside air that may have been heated, cooled and dehumidified. Suitable flexible tubes having apertures with controlled outflow of air are described in NL2021414 in the name of the applicant. In an air treatment room, recirculated air from the top part of the growing section of the greenhouse is mixed with outside air and is blown back into the perforated air tubes to be evenly distributed along the crop. For optimal growth it is important that the climate at the crop is as constant as possible. Due to the Venturi effect, the air speed in the tubes is limited and should preferably not exceed 10m/s, while the air speed should not drop below a lower threshold value in view of slow moving air heating up. As a result, at the exit of the air tubes the temperature of the slow moving air may become too high. In order to achieve a uniform climate at the crop, the diameter and length of the air tubes are carefully designed, and a maximum length of the air tubes is used. In larger greenhouses, which may have a length of 90m or longer, the length of the growing sections exceeds the maximum length of the air tubes. Summary of the invention It is an object of the present invention to provide a greenhouse of the above mentioned type with a relatively long growing section, along which a uniform climate can be achieved. It is another object of the invention to provide a greenhouse, which may be constructed in an efficient manner and in which the air tubes can be easily placed in fluid communication with the air treatment chamber and can be easily accessed for maintenance. It is also an object of the invention to provide an air tube for use in a greenhouse that is adapted for providing an uniform flow of air along the length of the growing section.

40 Hereto a greenhouse in accordance with the invention is characterized in that at least one of the air tubes comprises a relatively impermeable first segment of a length of at least 0,2 times the length L: of the air tube and a permeable second segment downstream of the first segment, wherein the airflow through the wall of the first segment is substantially lower that the airflow through the wall of the permeable second segment, the tubes being arranged in pairs comprising a first tube having a first 45 segment and a permeable second segment and a permeable second tube that extends adjacent the first segment of the first tube. By providing an air tube having a relatively impermeable upstream segment, the air can be supplied to the downstream segment of this tube at a sufficiently high speed to prevent too much heating up of the 50 air while being transported to the parts of the growing section that are remote from the air supply section. The upstream crop are provided with ventilation air via the parallel permeable air tube that is of shorter length and that extends alongside the relatively impermeable first segment of the long first tube. With the pairs of tubes according to the present invention, it is possible to achieve over a larger length of a greenhouse, for instance of 175 m or longer, a uniform flow of air, and to significantly 55 reduce the temperature of the air at the outflow end of the longer tube.

The first segment of the air tube may comprises a wall of flexible material that is substantially air tight, such a plastic or a woven or nonwoven cloth material. The permeable second tube segment may have an air permeability of between 500 and 30.000 m?hour that may be provided by perforations or apertures or by a uniform distribution of open space in a woven or non-woven material. In an embodiment of a greenhouse according to the invention, each tube is in fluid communication with an air treatment unit at its upstream part, comprising a blower and a heat exchange unit. The air treatment units may be of the twin coil type as described in NL 2025302, that was filed in the name of the applicant.

In an embodiment, the first segment comprises an inner tube having openings and a surrounding substantially air tight outer tube. The double walled tube provides an isolation for the air flowing through the tube to the remote positions of the growing section so that it can be blown onto the crop at a reduced temperature. The inner tube of smaller diameter is provide with apertures so that a layer of air fills the space between the inner permeable tube and the outer air impermeable tube. The slow moving layer of air between the co-axial tubes forms a thermal isolation and reduces heat transfer to the air in the inner tube.

The first, non-perforated segment of the relatively long tube may have a length of between 10 m and 120 m, the second segment having a length between 10 m and 120 m, a diameter of the tubes being between 20 cm and 150 cm.

At least 4 tubes may be arranged side by side in a transverse direction.

The invention may be applied to greenhouses in which daylight can enter and that may have a length of over 100 m, but also to relatively compact climate cells in which only artificial lighting is provided by LEDs.

In an embodiment, the diameter of the first segment of the tube is at least 10% larger than the diameter of the second segment, to provide a reduced air resistance in the first segment.

In an embodiment of a greenhouse according to the invention, a growing section is provided with an end wall extending transversely to the growing section, a number of heat exchange units, each connected to a tube extending in a length direction L that is transversely to the end wall, the lower end of the end wall being situated above the heat exchangers and connected with horizontal supports to an air treatment chamber wall, extends parallel to the outer wall, at a distance thereof, defining an air treatment chamber, the upper end of the air treatment chamber wall being situated below the top of the end wall, angled transverse sections connecting the upper end of the end wall to the top end of the 40 air treatment chamber wall.

The air treatment chamber allows free access to the tubes by passing underneath the greenhouse end wall, that is supported on the outer wall of the air treatment chamber, without interference with the vertical support columns of the end wall. This allows a larger freedom in the design of the dimensions 45 and positions of the air tubes and allows easy access to the heat exchange units an fans for maintenance or repair.

An air opening is provided in the upper part of the end wall, with a movable cover opening towards the air treatment chamber. In the greenhouse according to the invention, the air opening and the movable 50 cover can be of relatively small size, so that action for opening and closing can be effected using a relatively small size motor. As the closing of the movable cover is against the pressure of the recirculated air stream, reduced vibrations and consequently reduced ware of the motor, the connector and driving rack mechanism results when the cover is in a nearly closed state.

55 The air opening is opened by the cover hinging to an open position situated inside air treatment chamber. Hereby a flat insect mesh of simple construction can be employed across the air opening, without the need for pleads or the like or to provide a bellows-like extension as known in the prior art. Insect mesh is needed to prevent fertilizing insects that are employed in the growing section, such as bumble bees, from being sucked into the fans in the air treatment chamber.

60

In an embodiment of a greenhouse according to the invention, the inner wall is at the side of the air treatment chamber provided with heating and cooling ducts extending in the transverse direction. The ducts distribute hot and cold water to the air treatment chamber and provide heating or cooling fluid to other groups of ducts in the growing section.

Brief description of the drawings Some embodiments of a greenhouse and air duct according to the invention will by way of non-limiting example be explained in detail with reference to the accompanying drawings. In the drawings: Figure 1 shows a perspective view of a known greenhouse having an air treatment section and air tubes, Figure 2 shows a schematic top view of a greenhouse with partly perforated air tubes according to the invention, Figure 3a and 3b respectively show a transverse cross-section and a plan view of an embodiment of two concentric air tubes, Figure 4 shows a side view of an air treatment section of an embodiment of a greenhouse according to the invention, and Figures 5a and Sb show a perspective view of an air treatment section from respectively the outside and from the inside of a greenhouse according to the invention.

Detailed description of the invention Figure 1 shows a known greenhouse 1 with a growing section 2 and an air treatment section 3. The growing section 2 comprises rows of crop 4 extending in the length direction L, wherein the length may be 100m or more. The crop are placed in beds 5 with a growing substrate that are situated over perforated air ducts, or tubes 6 that blow a uniformly distributed amount of warm or cold air upwards along the crop. 50 or more assemblies of beds 5 and air ducts 6 may extend in the transverse direction T of the greenhouse 1.

The air treatment section 3 comprises an inner wall 7 that forms a separation from the growing section 2, with an air opening 8 at the top, that is closed off by a hinging cover 9. Air may be recirculated from the upper part of the growing section 2, as indicated by the arrow 11, into the air treatment section 3, and may be mixed with air 12 that is admitted from the ambient outside of the greenhouse 1 through a permeable pad wall 13. In the air treatment section 3, additional heating and/or dehumidifying modules 15 may be placed for conditioning the air such as to have the desired temperature and humidity. The conditioned air is blown from the air treatment section 3 into the tubes 5 via fans 16. The end wall 18 of the greenhouse 1 at the top part carries the horizontal gutters 19 that support the glass roof panels 20, and may have a height of 4 m or more.

40 Figure 2 shows a schematic top view of the greenhouse 21 according to the invention, wherein the air ducts 25-30 are arranged in pairs 25,26; 27,28;29,30. Each pair comprises a relatively long duct 26,28,30 with a length Li that may substantially correspond to the length of the greenhouse, and may be 150 m or more and a relatively short duct 25,27,29. The short ducts 25,27,29 are permeable to air along substantially their whole length Ls whereas the long ducts each have a first segment 26;, 28;,30; 45 that is substantially impermeable to air and a downstream second segment 26,,28p,30p that is air permeable.

The length of the long ducts Limay range from 20m to 240m and preferably Ls is no longer than 100m. The diameter of the ducts may range from 20 cm to 150 cm. The pairs of ducts 25,26;27,28 and 29,30 are placed side by side in fluid connection with the air treatment chamber 23 and may each be 50 provided with an individual fan, or can be connected to a single common blower.

The ducts 25-30 may be made of rigid tubing or can be formed of flexible cloth material of plastic film material, or woven or nonwoven sheet material that is inflated to a cylindrical shape by the pressure of the transported air. The air permeability of the ducts is achieved by providing holes or perforations 31, 32 in the walls of the ducts or by the air permeability of the material of the walls of the ducts.

Figures 3a and 3b respectively show a cross-sectional view and a plan view of a long duct 26 with a double-walled first segment 286i. An inner tube 35 of air permeable material, for instance by being provided with openings 37, is surrounded by an outer tube 36 of air tight material. The diameter Dy of the permeable inner tube 35 is for instance 90 cm, while the diameter Di of the impermeable outer tube 36 is 100 cm. The space between the tubes 35, 36 contains air that slowly flows in the downstream direction from the air treatment chamber 23 and provides an effective thermal insulation of the air in the first part of the long tubes 26,28,30. Figure 4 shows a greenhouse 40 with a growing section 41 and an air treatment section 42 that is separated from the growing section by a partition wall 45. The wall 45 comprises vertical columns 55 supporting at the top horizontal gutters 48 of a roof structure. The wall 45 is supported on outer vertical columns 51 via horizontal support elements 50 and angled rafters 49. The air ducts 43 and the crop supporting beds 44 extend in the length direction of the greenhouse and extend below the wall 45 into the air treatment section 42. There each duct 43 is connected to a unit 53 comprising a fan and a heat exchange system for heating or cooling of the air that is blown into the ducts 43. Because the air ducts 43 run free from the overhead wall 45, there is more freedom in placing of the tubes side by side at the desired interspacing without interference with the support columns of the wall 45. Also removal of individual heat exchange units 53 is facilitated by easy access. Outside air enters the air treatment section 42 through a permeable padded wall 5. Recirculated air enters into the air treatment section 42 through a window 56 in the wall 45, which window is closed by a cover 57 that hinges into the air treatment section 42 and that is actuated by an electric motor drive

52. The window 56 is covered by a planar insect mesh of a relatively simple design, extending substantially parallel to the wall 45, that prevents pollinating insects such a bumble bees, from entering from the growing section 41 into the air treatment section 42. The closing of the cover 57 by the motor drive 52, against the force of the recirculated air flowing from the growing section 41, reduces undesired vibrations and wear. Figures 5a and 5b show a perspective view of respectively the outside and the inside of the greenhouse 40. The open structure of the wall 45 is formed by vertical columns 55, 55° and horizontal interconnecting bars 62, and supports cooling ducts 60 and heating ducts 61 for heating and cooling of the air in the air treatment section 42.

Claims

Conclusions

1. Greenhouse (21,40) comprising a cultivation section (22,41) for growing crops, with an air supply section (23,42) extending in a width direction T, a number of air pipes 5 (25,26,27,28 ,29,30;43) extending in a longitudinal direction L into the breeding section (22,41) with their inlets in fluid communication with the air supply section (23,42), the tubes including openings (31,32,37) for blowing air from the air supply section (23,42) into the breeding section (22,41), characterized in that at least one of the air tubes (26,28,30) has a relatively impermeable first segment (26;, 28,30 ) of a length of at least 0.2 times the length Li of the air tube (26, 28, 30) and a permeable second segment (26;p, 28,,30p) downstream of the first segment (26; 28;, 30;), wherein the airflow through the wall of the first segment (26, 28;,30;) is significantly lower than the airflow through the wall of the transmissive second segment (26, 285,30p), the tubes being at brought in pairs (25,26;27,28; 29,30), each pair comprising: a first tube (26,28,30) having a first segment (26,28;,30) and a transmissive second segment {26,;,28,,30p), and a transmissive second tube (25,27,29) extending adjacent the first segment (26,28;,30) of the first tube ({28,28,30).

A greenhouse (21,40) according to claim 1, wherein the first segment (26; 28,30) comprises a wall of flexible material that is substantially airtight.

Greenhouse (21,40) according to claim 1 or 2, wherein the permeable second pipe segment (261,28,,30;) has an air permeability of between 500 and 30,000 m 2 /hour.

Greenhouse (21,40) according to any one of the preceding claims, wherein each tube (25,26,27,28,29,30;43) is in fluid communication with an air treatment unit (53) at its upstream part comprising a fan and a heat exchange unit.

A greenhouse (21,40) according to any one of the preceding claims, wherein the first segment (26, 28,305) comprises an inner tube (35) having openings (37) and a surrounding substantially airtight outer tube (36).

Greenhouse (21,40) according to one of the preceding claims, wherein the first segment (26, 28,30) has a length Ls of between 10 m and 120 m, the second segment (26, 28,,30p) has a length between 10 m and 120 m, the length of the second tube (25,27,29) corresponds to the length Ls of the first segment (26, 28,30), and a diameter Dy of the tubes between 20 cm and is 150 cm.

7. Greenhouse (21,40) according to one of the preceding claims, comprising at least 50 tubes 40 arranged side by side in a width direction T.

Greenhouse (21, 40) according to one of the preceding claims, wherein the diameter Di of the first segment (26, 28:,30;) is at least 10% larger than the diameter Dy of the second segment (265, 28p). ,30p).

9. Greenhouse (40) comprising a growing section (41) with an end wall (45) extending transversely to the growing section (41), a number of heat exchange units (53, 53), each of which is connected to a pipe (43, 43') extending in a longitudinal direction L transverse to the end wall (45), the lower end of the end wall being located above the heat exchange units (53,53'}, and connected by horizontal beams (50,50) to an air handling chamber wall (51, 517) extending parallel to the end wall (45) at a distance therefrom defining an air handling chamber (42), the upper end of the air handling chamber wall (51, 51) being located below the upper portion of the end wall (45), with oblique transverse sections (49,49) connecting the top of the end wall (45) to the upper part of the air handling chamber wall (51,51).

A greenhouse (40) according to claim 9, wherein an air opening (56) is provided in the upper part of the end wall (45), with a movable cover (57) opening towards the air treatment chamber (42).

A greenhouse according to claim 9 or 10, wherein the end wall (45) located on the side of the air treatment chamber (42) is provided with heating and cooling ducts (61,62) extending in the transverse direction.

12. Tube (25,26,27,28,29,30;43), for use in a greenhouse, made of rigid or flexible material and comprising a first segment (28, 28:,30;) of a length of at least at least 10 m which is substantially airtight and a second segment (26, 285,30p) with an air permeability greater than the air permeability of the first segment.

A tube (25,26,27,28,29,30;43) according to claim 12, wherein the first segment (28, 28;,30;) has an inner tube (35), which has openings (37), and a surrounding substantially airtight outer tube (36}.