WO2017155409A1

WO2017155409A1 - Air circulation system, greenhouse fitted with such an air circulation system and method for dehumidifying air

Info

Publication number: WO2017155409A1
Application number: PCT/NL2017/050156
Authority: WO
Inventors: Filip Jozef BRONCHART; Raf Michaël Julien DEVIS; Petrus Hubertus Emanuel Maria Malschaert
Original assignee: Maurice Kassenbouw B.V.; Universiteit Gent; Instituut Voor Landbouw- En Visserijonderzoek; Proefstation Voor De Groenteteelt Vzw
Priority date: 2016-03-11
Filing date: 2017-03-13
Publication date: 2017-09-14
Also published as: NL2016422B1

Abstract

An air circulation system for circulating air in an interior, wherein the air circulation system comprises a dehumidification device arranged for dehumidifying air from the air pipe over the length of an air pipe and supplying dehumidified air to the interior. A greenhouse fitted with such an air circulation system. A method for dehumidifying air.

Description

Title: Air circulation system, greenhouse fitted with such an air circulation system and method for dehumidifying air

Description

According to a first aspect, the invention relates to an air circulation system for circulating air in an interior space, wherein the air circulation system comprises an air pipe and a pressure device for forcing air from the interior through the air pipe, wherein the air circulation system is arranged for supplying air from the air pipe in the interior distributed over a length of the air pipe.

The present invention also relates to a greenhouse fitted with an air circulation system according to the first aspect and a method for dehumidifying air.

NL 1037152 discloses an air circulation system for circulating air in an interior space, wherein the air circulation system comprises a vertical air shaft for the condensation therein of the moisture present in the air on a first wall portion formed by a part of the outer wall of the interior. Although the above-described known air circulation system functions well in practice, it can be further improved as regards the dehumidification of air in the interior.

It is an object of the present invention to provide an air circulation system wherein air is dehumidified effectively.

The above object is achieved with the air circulation system according to the present invention in that the air circulation system further comprises a dehumidification device arranged for dehumidifying air from the air pipe distributed over said length of the air pipe and for supplying the dehumidified air to the interior, the dehumidification device comprising:

a dehumidification space extending over said length and being provided with an air inlet and an air outlet for supplying air from the air pipe to the interior via, successively, the air inlet, the dehumidification space and the air outlet using the pressure device, and an air-permeable dehumidification element provided in the dehumidification space, and

a moistening device arranged for moistening the dehumidification element for extracting moisture from air present in the dehumidification space with a hygroscopic salt solution.

The invention is based on the insight that by dehumidifying the air distributed over the length of the air pipe in an effective manner, a desired degree of dehumidification is achieved, wherein undesired temperature variations in the air supplied to the interior are reduced. Because the moist air is forced through the air pipe, no drop in temperature or only a slight drop in temperature occurs in the air pipe, as the heat in the air is present in the form of latent heat. This latent heat is converted into sensible heat over the length of the air pipe in the dehumidification device near the air outlet. When air is dehumidified using a dehumidification element that has been moistened with a hygroscopic salt solution, latent heat is converted into sensible heat that heats the dehumidification element. As a result of the heating of the dehumidification element, the air that flows through the dehumidification element is heated before the air is supplied from the dehumidification space to the interior via the air outlet. By not dehumidifying the air until it is near to the position where the air is supplied to the interior, a situation is prevented in which undesired temperature variations occur in the air supplied to the interior as a result of the dehumidification of the air. In this way a circulation system is provided by means of which air in a greenhouse is effectively dehumidified using a hygroscopic salt solution.

In an advantageous embodiment the dehumidification device comprises a drip tray arranged for catching droplets present in the air dehumidified by the dehumidification element before the air is supplied to the interior via the air outlet in use. The provision of the drip tray prevents or at least strongly reduces any undesirable discharge of moisture with hygroscopic salt from the dehumidification device via the outlet. Hygroscopic salt can be harmful to items that are present in the interior, such as plants, resulting in a reduced crop yield.

It is advantageous if the air pipe extends into a lower part of the interior, wherein the pressure device is arranged for forcing air from a higher part of the interior through the air pipe. This is advantageous for circulating air in the interior in an advantageous manner, wherein the dehumidified air supplied to the lower part of the interior moves to the higher part air of the interior while present in the interior.

The dehumidification device is preferably provided with a drainage channel for draining moisture from the dehumidification space. The drainage of moisture using a gutter is advantageous for keeping the relative humidity in the dehumidification space relatively low. The moisture to be drained can be drained from the dehumidification space via the gutter over the length of the dehumidification device, wherein the gutter preferably slopes slightly relative to the horizontal. It is advantageous in this regard to provide the gutter with a drainage opening that can be connected to a moisture circulation system for the reuse of moisture in the moistening device that has been discharged from the dehumidification space.

In one embodiment, the air outlet of the dehumidification device comprises air outlets distributed individually over the length of the air pipe and/or wherein the air inlet of the dehumidification device comprises air inlets distributed individually over the length of the air pipe.

It is advantageous if the dehumidification element comprises a layer of a granular material or a porous material with an open cell structure. Such materials are advantageous for obtaining a relatively large area of the dehumidification element, so that a relatively large dehumidification capacity can be realised.

In an advantageous embodiment, the dehumidification element separates the dehumidification space into a first chamber, into which the air inlet opens, and a second chamber. As a result of the division of the dehumidification device into two chambers using the dehumidification element, all the air to be dehumidified that is forced through the dehumidification space passes through the dehumidification element in use. This is advantageous for obtaining a more effective dehumidification of the air that is supplied to the dehumidification device.

It is advantageous if the moistening device comprises an atomiser which atomises the salt solution in the second chamber and which is arranged for moistening the dehumidification element with the salt solution from above. An atomiser is advantageous for obtaining a good distribution of the salt solution over the upper surface of the dehumidification element.

In one embodiment, the second chamber is provided above the first chamber, wherein the dehumidification element can be moistened by the moistening element from above and wherein the drip tray is provided above the moistening element. This is advantageous for the recirculation of the salt solution in the second chamber as moisture falling from the drip tray can moisten the dehumidification element.

It is advantageous if the dehumidification device is tubular in shape, wherein a wall of the tube surrounds the dehumidification space. A tubular shape is advantageous with a view to providing the dehumidification element and drip tray in a relatively compact manner over the length of the dehumidification device.

It is advantageous if the air pipe connects to the wall of the tube in such a way that the air inlet is located inside the air pipe. In this way it is achieved that the dehumidification device is at least partially accommodated in the air pipe.

In one embodiment of the air circulation system, a bottom wall of the tube forms the drainage channel. This embodiment is advantageous for the drainage of moisture from the dehumidification device in a robust manner using a relatively limited number of elements, wherein each of the air pipes thus has a dehumidification device connected thereto. In a practical embodiment, the drip tray is provided in the wall of the tube, wherein the wall is provided with a drip tray inlet for letting dehumidified air into the drip tray.

It is advantageous in this regard if the drip tray is connected for fluid flow to the drainage channel for draining the moisture from the drip tray.

It is advantageous if the wall is configured to be double-walled at the location of the drip tray, wherein the air dehumidified by the dehumidification element flows through a wall space located in the double- walled wall in use.

It is advantageous if the wall space is divided into a plurality of channels for passing the dehumidified air through the plurality of channels.

In a practical embodiment of the invention according to the first aspect, the air circulation system is for use in a greenhouse for growing plants in an interior of the greenhouse, wherein the air circulation system is arranged for circulating air in the interior and comprises an air pipe and a pressure device for forcing air from a higher part of the interior through the air pipe, wherein the air pipe extends into a lower part of the interior, wherein the air circulation system is arranged for supplying air from the air pipe to the interior distributed over a length of the air pipe, wherein the air circulation system also comprises a dehumidification device arranged for dehumidifying air from the air pipe distributed over this length of the air pipe and supplying the dehumidified air to the interior, likewise distributed over this length, therefore, the dehumidification device comprising:

a dehumidification space extending over said length and being provided with an air inlet and an air outlet for supplying air from the air pipe to the interior via the air inlet, the dehumidification space and the air outlet using the pressure device, and

an air-permeable dehumidification element provided in the dehumidification space, and a moistening device arranged for moistening the dehumidification element for extracting moisture from air present in the dehumidification space with a hygroscopic salt solution,

a drip tray arranged for catching droplets present in the air dehumidified by the dehumidification element before the air is supplied to the interior via the air outlet in use.

The present invention also relates to a greenhouse for growing plants in an interior of the greenhouse, which greenhouse is fitted with an air circulation system according to the first aspect of the present invention, wherein the air circulation system supplies air from the air pipe between or at least along the plants in use. The advantages of such a greenhouse are analogous to the advantages of the air circulation system according to the present invention.

In an advantageous embodiment, the greenhouse is provided with a cultivation gutter for growing plants thereon, wherein the dehumidification device extends under the cultivation gutter and the air outlet is provided near the cultivation gutter. Providing the dehumidification device under the cultivation gutters achieves that the rising dehumidified air from the air outlet will be present near the plants in the interior relatively soon after having exited the air outlet. This prevents the dehumidified air absorbing a relatively large amount of moisture already before it reaches the plants. In general it can be stated that, independently of the presence of a cultivation gutter, the air pipe extends near a floor surface of the greenhouse. Usually the plants are cultivated in a lower part of the interior, so that supplying dehumidified air to the lower part of the interior will be beneficial to the plants to be cultivated.

In one embodiment of the greenhouse, the greenhouse is provided with a plurality of parallel cultivation gutters for growing the plants, wherein the air circulation system comprises a plurality of the air pipes, each arranged beneath and parallel to a respective one of the plurality of cultivation gutters. This is advantageous for supplying air dehumidified by the dehumidification device to a lower part of the interior in a relatively uniform manner over said lower part.

It is advantageous if the cultivation gutter is provided with an insulation element on the side facing the air outlet for reducing the transfer of heat between the cultivation gutter and the air flowing from the air outlet. The provision of an insulation element prevents or at least reduces heating of the cultivation gutter. Preventing heating of the cultivation gutter is advantageous in the cultivation of plants of which the substrate material must remain relatively cool.

It is advantageous if at least two air pipes and pressure devices under a cultivation gutter are provided distributed over the length of the cultivation gutter. This enables a relatively direct exchange of heat between a higher part of the interior and a lower part of the interior because air from the interior can be forced into an air pipe at at least two locations.

According to another aspect, the present invention relates to a method for dehumidifying air in an interior, such as that of a greenhouse, comprising the steps of:

a) forcing air through the air pipe using the pressure device, wherein, successively, air is supplied to the dehumidification space of the dehumidification device via the air inlet, then flows through the dehumidification element and the drip tray to be subsequently discharged to the interior via the air outlet;

b) moistening the dehumidification element with hygroscopic salt solution using the moistening device.

In an advantageous embodiment of the method for dehumidifying air, use is made of an air circulation system according to the first aspect of the present invention.

It is advantageous if the method is used in a greenhouse according to the second aspect of the present invention. In one embodiment of the method for dehumidifying air in an interior of a greenhouse, the greenhouse is provided with a plurality of parallel cultivation gutters for growing plants thereon, wherein the air circulation system comprises a plurality of air pipes, each under and parallel to a respective one of the plurality of cultivation gutters, the method comprising the following steps:

forcing air through the plurality of air pipes using the pressure device, wherein air for each air pipe is supplied to the dehumidification space of the dehumidification device of said respective air pipe via the air inlet, then flows through the dehumidification element and the drip tray to be discharged to the interior of the greenhouse via the air outlet;

moistening the dehumidification element of each air pipe with a hygroscopic salt solution using the moistening device.

The present invention will be now be explained in more detail by means of a description of a preferred embodiment of a greenhouse according to the present invention and a method for dehumidifying air, wherein reference is made to the following schematic figures, in which:

Figure 1 is a three-dimensional view of a preferred embodiment of a part of a greenhouse according to the present invention;

Figure 2 is a cross-sectional view along the line ll-ll in figure 1 ;

Figure 3 is a cross-sectional view along the line Ill-Ill in figure

2;

Figure 4 shows detail A from figure 3.

A greenhouse 1 as shown in figures 1 and 2 comprises a frame of pillars and girders 3 and gutters 4 supported by the pillars. Pointed roofs in the shape of an inverted V are provided between two parallel gutters 4. Exterior walls of the greenhouse 1 are formed by a matrix of glass panels 5 situated next to and above each other, which panels 5 are correctly positioned relative to each other by means of bars 6. The greenhouse 1 to which the invention relates has a length of a few hundred metres and a width of approximately 100 metres.

In the greenhouse 1 an air circulation system 2 is provided, by means of which air can be drawn in at a higher level, i.e. at a height near the girders 3 and gutters 4, and be released back into the interior 50 of the greenhouse 1 at a lower level, i.e. near the floor surface 7 of the greenhouse. The air circulation system 2 thus circulates air in the interior 50 of the greenhouse 1 . To this end the system 2 comprises an air pipe 17 and a pressure device formed by a fan 15. In one embodiment it is conceivable that the air circulation system comprises a pipe system for supplying air, using a fan and a transverse pipe, to air pipes being in communication with the fan.

Provided under the cultivation gutter 18 are furthermore dehumidification devices 20 for returning dehumidified air to the greenhouse 1 at desired locations. To this end the dehumidification devices 20 are provided with air outlets 19 at these desired locations, through which the dehumidified air can flow back into the interior 50 of the greenhouse 1 . Both the pipes 17 and the dehumidification devices 20 are closed, each at the location of their downstream end, i.e. the end remote from the fan 15.

Figure 3 is a cross-sectional view along the line Ill-Ill in figure 2, it shows a cross-section of an air pipe 1 7, a dehumidification device 20 and a cultivation gutter 18, which are components of the air circulation system 2 of the greenhouse 1 . The cultivation gutter 18 is provided with an insulation element 38 at the bottom side.

The dehumidification device 20 extends in the longitudinal direction A and partially through a pipe interior 24 of the air pipe 17. As a result of the dehumidification device 20 being at least partially accommodated in the pipe interior 24, the reduction of the amount of space available for cultivating crops in the interior 50 of the greenhouse 1 is relatively limited. The wall of the air pipe 17 is connected to the dehumidification device 20, wherein the pipe interior 24 of the air pipe 17 is connected for fluid flow to a dehumidification space 26 of the dehumidification device 20 via the air inlet 28. The dehumidification space 26 extends over the length of the dehumidification device 20. The dehumidification device 20 is provided with an air outlet 19. The air outlet 19 is separated from a second chamber 40 by a drip tray 42. The drip tray 42 extends in such a way that air in the second chamber 40 can only be discharged from the dehumidification device 20 through the air outlet 19 via the drip tray 42. The drip tray 42 is provided in the wall 30 of the tube. The wall 30 is configured to be double-walled at the location of a drip tray 42. The double-walled wall has an inner wall 30a and an outer wall 30b. The inner wall 30a and the outer wall 30b define a wall space 43. When the dehumidification device 20 is in use, the air that has been dehumidified by the dehumidification element 48 flows through the wall space 43 in use. The wall 30 is provided with a drip tray inlet opening 31 on the side facing the second chamber 40 for letting in dehumidified air from the second chamber 40 into the drip tray 42. The wall space 43 is divided into a plurality of channels that are formed by ribs extending between the inner wall 30a and the outer wall 30b. The channels extend substantially parallel to each other between the drip tray inlet opening 31 and the outlet 1 9. The second chamber 40 is located above a dehumidification element 48 that connects to the wall 30 encircling the dehumidification space 26. A recirculation organ 35 is provided on the part of the wall 30 between the dehumidification element 48 and the drip tray inlet opening 31 . In use, the recirculation organ 35 effects an advantageous flow at the location of the drip tray inlet opening 31 for discharging dehumidified air from the second chamber 40.

The dehumidification element 48 may be made up of known materials that have a relatively large surface area, such as, for example, a layer of granules or a porous material with an open cell structure. On the side of the dehumidification element 48 remote from the second chamber 40 a first chamber 44 of the dehumidification space 26 is provided, into which the air inlet 28 opens. In the second chamber 40 a moistening device configured as an atomiser 32 is provided. The atomiser 32 is arranged for atomising a hygroscopic salt solution 34 on the surface of the dehumidification element 48 in the second chamber 40 in use. The atomiser 32 is connected to a supplying device (not shown) for the hygroscopic salt solution 34 to be atomised. A drainage channel 46 is formed on the bottom side of a first chamber 44. In one embodiment, the drainage channel 46 can be connected, via a connection not shown, to the supplying device for the reuse of moisture in the moistening device that has been discharged from the dehumidification device 20. The drainage channel 46 is connected for fluid flow to the wall space 43 for the drainage of moisture from the drip tray 42.

The dehumidification device 20 is provided with a fastening element 23 on the wall 30 for attaching the air pipe 17 to the dehumidification device 20. In one embodiment, the fastening element is provided with openings for the provision therein of fastening means for attaching the dehumidification device to a cultivation gutter.

In the greenhouse 1 , air can be dehumidified in the following way. A fan 15 is used to force air from the higher part of the interior 50 of the greenhouse 1 into the air pipe 17. The air forced into the air pipe 17 is supplied to the dehumidification space 26 of the dehumidification device 20 via the air inlet 28. The air supplied to the dehumidification space 26 flows through the dehumidification element 48 and the drip tray 42 and is discharged into the interior 50 of the greenhouse 1 via the air outlet 19. The dehumidification element 48 is moistened with the hygroscopic salt solution by the atomiser 32. In use, moisture is extracted from the air to be dehumidified in the second chamber 40 and the hygroscopic salt solution 34 on the surface of the dehumidification element 48. Moisture that passes through the dehumidification element 48 to the first chamber 44 drops into the drainage channel 46. Any droplets of moisture carried along by the dehumidified air in the second chamber 40 are caught by the drip tray 42 and fall from the drip tray 42 into the drainage channel 46. As heat is released when moisture from the air to be dehumidified is condensed, the dehumidification element 48 heats up. As a result of the dehumidification element 48 heating up, the air is heated as it passes the dehumidification element 48.

Claims

1 . An air circulation system for circulating air in an interior space, wherein the air circulation system comprises an air pipe and a pressure device for forcing air from the interior through the air pipe, wherein the air circulation system is arranged for supplying air from the air pipe in the interior distributed over a length of the air pipe, characterised in that the air circulation system further comprises a dehumidification device arranged for dehumidifying air from the air pipe distributed over said length of the air pipe and for supplying the dehumidified air to the interior, the dehumidification device comprising:

a dehumidification space extending over said length and being provided with an air inlet and an air outlet for supplying air from the air pipe to the interior via, successively, the air inlet, the dehumidification space and the air outlet using the pressure device, and

an air-permeable dehumidification element provided in the dehumidification space, and

2. An air circulation system according to claim 1 , wherein the dehumidification device comprises a drip tray arranged for catching droplets present in the air dehumidified by the dehumidification element before the air is supplied to the interior via the air outlet in use.

3. An air circulation system according to claim 1 or 2, wherein the air pipe extends into a lower part of the interior, wherein the pressure device is arranged for forcing air from a higher part of the interior through the air pipe.

4. An air circulation system according to any one of the preceding claims, wherein the dehumidification device is provided with a drainage channel for draining moisture from the dehumidification space.

5. An air circulation system according to any one of the preceding claims, wherein the air outlet of the dehumidification device comprises air outlets distributed individually over the length of the air pipe and/or wherein the air inlet of the dehumidification device comprises air inlets distributed individually over the length of the air pipe.

6. An air circulation system according to any one of the preceding claims, wherein the dehumidification element comprises a layer of a granular material or a porous material with an open cell structure.

7. An air circulation system according to any one of the preceding claims, wherein the dehumidification element separates the dehumidification space into a first chamber, into which the air inlet opens, and a second chamber.

8. An air circulation system according to claim 7, wherein the moistening device comprises an atomiser which atomises the salt solution in the second chamber and which is arranged for moistening the dehumidification element with the salt solution from above.

9. An air circulation system according to any one of the preceding claims, wherein the dehumidification device is tubular in shape, wherein a wall of the tube surrounds the dehumidification space.

10. An air circulation system according to 9, wherein the air pipe connects to the wall of the tube in such a way that the air inlet is located inside the air pipe.

1 1 . An air circulation system according to claim 9 and according to claim 4 or a claim dependent thereon, wherein a bottom wall of the tube forms the drainage channel.

12. An air circulation system according to claim 2 and according to claim 9, wherein the drip tray is provided in the wall of the tube, wherein the wall is provided with a drip tray inlet for letting dehumidified air into the drip tray.

13. An air circulation system according to claim 12 and according to claim 4, wherein the drip tray is connected for fluid flow to the drainage channel for draining the moisture from the drip tray.

14. A greenhouse for growing a crop in an interior of the greenhouse, provided with an air circulation system according to any one of the preceding claims, wherein the air circulation system supplies air from the air pipe between or at least along the plants in use.

15. A greenhouse according to claim 14, comprising a cultivation gutter for growing plants thereon, wherein the dehumidification device extends under the cultivation gutter and wherein the air outlet is provided near the cultivation gutter.

16. A greenhouse according to claim 14, comprising a plurality of parallel cultivation gutters for growing the crop thereon, wherein the air circulation system comprises a plurality of the air pipes, each arranged beneath and parallel to a respective one of the plurality of cultivation gutters.

17. A greenhouse according to any one of claims 14 - 16, wherein the cultivation gutter is provided with an insulation element on the side facing the air outlet for reducing the transfer of heat between the cultivation gutter and the air flowing from the air outlet.

18. A method for dehumidifying air in an interior space, for example of a greenhouse, comprising the steps of:

19. A method according to claim 18 using an air circulation system according to any one of claims 1 - 13.

20. A method according to claim 19 for use in a greenhouse according to any one of claims 14- 17.