GRID STRUCTURES FOR STABLE GAS RETENTION UNDER LIQUIDS

Abstract

Device mountable on a surface (10), the device comprising a spacer system (12, 16, 20, 22) and a grid structure (2) which grid structure (2) is attached in spaced relation to the surface (10) by means of the spacer system (12, 16, 20, 22), wherein the distance between the surface (10) and the grid structure (2) is in a range from >0.1 m to <10 mm, wherein the grid structure (2) forms meshes of a mesh size in a range from >0.5 m to <8 mm, and wherein the surface of the grid structure (2) is at least partially amphiphobic. Method of maintaining a gas or air layer on a surface when the surface is immersed in a liquid or water comprising such device, and uses thereof.

Claims

1. A device mountable on a surface (10), the device comprising a spacer system (12, 16, 20, 22) and a grid structure (2) which grid structure (2) is attached in spaced relation to the surface (10) by means of the spacer system (12, 16, 20, 22), wherein the distance between the surface (10) and the grid structure (2) is in a range from 0.1 m to 10 mm, wherein the grid structure (2) forms meshes of a mesh size in a range from 0.5 m to 8 mm, and wherein the surface of the grid structure (2) is at least partially amphiphobic.

2. The device according to claim 1, wherein the grid structure is provided by a perforated plate, a grating, a net, a woven or non-woven mesh, or is formed by woven or non-woven filaments.

3. The device according to claim 1, wherein the distance between the surface (10) and the grid structure (2) is in a range from 1 m to 6 mm.

4. The device according to claim 1, wherein the grid structure (2) forms meshes of a mesh size in a range from 5 m to 2 mm.

5. The device according to claim 1, wherein the spacer system (12, 16, 20, 22) is formed by solitary rodlike bars (12) or wall-like ledges (20, 22), or by a porous layer (16), or the spacer system is a combination thereof.

6. The device according to claim 1, wherein wall-like ledges (20, 22) form compartments (18) on the surface (10).

7. The device according to claim 1, wherein the wall-like ledges (20, 22) comprise through openings (24, 26, 28) to provide an exchange of gas between adjacent compartments (18).

8. The device according to claim 1, wherein the grid structure (2) comprises protrusions (30) on the grid surface.

9. An object comprising a device mountable on a surface (10), the device comprising a spacer system (12, 16, 20, 22) and a grid structure (2) which grid structure (2) is attached in spaced relation to the surface (10) by means of the spacer system (12, 16, 20, 22) according to claim 1.

10. A method of maintaining a gas or air layer on a surface (10) when the surface is immersed in a liquid or water, the method comprising providing a device mountable on a surface (10), the device comprising a spacer system (12, 16, 20, 22) and a grid structure (2) which grid structure (2) is attached in spaced relation to the surface (10) by means of the spacer system (12, 16, 20, 22), wherein the distance between the surface (10) and the grid structure (2) is in a range from 0.1 m to 10 mm, wherein the grid structure (2) forms meshes of a mesh size in a range from 0.5 m to 8 mm, and wherein the surface of the grid structure (2) is at least partially amphiphobic.

11. Use of a device mountable on a surface (10), the device comprising a spacer system (12, 16, 20, 22) and a grid structure (2) which grid structure (2) is attached in spaced relation to the surface (10) by means of the spacer system (12, 16, 20, 22) according to claim 1 for the reduction of flow resistance or friction, for the prevention of biofouling, and/or as a sensor for flow or pressure.

12. The device according to claim 1, wherein the distance between the surface (10) and the grid structure (2) is in a range from 10 m to 2 mm.

13. The device according to claim 1, wherein the grid structure (2) forms meshes of a mesh size in a range from 10 m to 800 m.

Description

[0043] The figures show:

[0044] FIG. 1: a schematical representation of a grid structure with square end slots.

[0045] FIG. 2: a schematical representation of a honeycomb-like grid structure.

[0046] FIG. 3: a schematical representation of a grid structure with a schematical representation of round apertures.

[0047] FIG. 4: a schematical representation of a grid structure with arrow-shaped apertures.

[0048] FIG. 5: a schematical representation of different cross sections of grid filaments.

[0049] FIG. 6: a schematical representation of a top view of a grid structure.

[0050] FIG. 7: a schematical representation of a grid filament.

[0051] FIG. 8: a schematical representation of different spacers on a surface.

[0052] FIG. 9: a schematical representation of a device comprising a spacer system and a grid structure which is attached in spaced relation to a surface by the spacer system according to an embodiment of the invention.

[0053] FIG. 10: a schematical representation of a device comprising a spacer system and a grid structure which is attached in spaced relation to a surface by the spacer system according to another embodiment.

[0054] FIG. 11: a schematical representation of a device comprising a spacer system and a grid structure which is attached in spaced relation to the surface by wall-like spacers according to a further embodiment.

[0055] FIG. 12: a schematical representation of a device comprising a spacer system and a grid structure which is attached in spaced relation to the surface by wall-like spacers providing a compartmentation according to a further embodiment.

[0056] FIG. 13: a schematical representation of a surface comprising a grid structure with wall-like spacers providing hexagonal compartments on the surface.

[0057] FIG. 14: a schematical representation of a surface comprising a grid structure with wall-like spacers providing arrow-like compartments on the surface.

[0058] FIG. 15: a schematical representation of a compartimentized surface comprising a grid structure which is attached in spaced relation to the surface by spacer bars providing compartments according to a further embodiment.

[0059] FIG. 16: a schematical representation of a compartment having rectangular through openings in the wall-like spacers.

[0060] FIG. 17: a schematical representation of a compartment having triangular through openings in the wall-like spacers.

[0061] FIG. 18: a schematical representation of a compartment having circular holes in the wall-like spacers.

[0062] FIG. 19: a schematical representation of a surface with several compartments, each interconnected via through openings.

[0063] FIG. 20: a schematical representation of a surface with several compartments, each compartment being interconnected with one further compartment.

[0064] FIG. 21: a schematical representation of a surface with several compartments, wherein aligned compartments are interconnected.

[0065] FIG. 22: a schematical representation of a top view of a compartment of a surface with a grid structure having mesh openings of varying size.

[0066] FIG. 23: a schematical representation of a cross section of a compartment according to a further embodiment.

[0067] FIG. 24: a schematical representation of a surface comprising spacers according to a further embodiment.

[0068] FIG. 25: a schematical representation of a grid structure comprising protrusions on the grid surface.

[0069] FIG. 26: a schematical representation of a grid structure comprising protrusions on junctions of the grid structure.

[0070] FIGS. 1 to 4 schematically show different grid structures 2, wherein FIG. 1 shows a grid structure 2 having square end slots, and FIG. 2 a honeycomb-like grid structure 2. FIG. 3 shows a grid structure 2 with round apertures. Such a grid structure can be provided by a perforated metal plate. The grid structure 2 shown in FIG. 4 has arrow-shaped apertures.

[0071] FIG. 5 shows a schematical representation of different cross sections of filaments 4 which can form a grid structure. The filaments 4 in the shown embodiments have round, oval, hexagonal, triangular or square cross sections.

[0072] FIG. 6 shows a schematical representation of a top view of a hydrophobic grid structure 2, wherein the nodes 6 of the grid provide a hydrophilic area. FIG. 7 shows a schematical representation of a grid filament 4 that comprises a hydrophilic area 8. The hydrophilic area 8 in this embodiment is provided on the top surface of the grid which will contact the fluid when a surface equipped with a grid formed from such grid filaments 4 comprising a hydrophilic area 8 is immersed in a fluid.

[0073] FIG. 8 shows a schematical representation of different spacers 12 on the surface 10 of an object. The spacers 12 have a rod-shaped, conical or ball-shaped form, or are rodlike with a starlike base.

[0074] FIG. 9 shows a schematical representation of an object 14 able to maintain a gas layer on the surface. According to the shown embodiment, on the surface 10 is mounted a device comprising a grid structure 2, which is attached to the surface 10 in spaced relation by spacers 12. A gas layer is held between the grid 2 and the surface 10. FIG. 10 shows a schematical representation of an object 14 able to maintain a gas layer on the surface. According to the shown embodiment, on the surface 10 is mounted a device comprising a grid structure 2 which is attached in spaced relation to the surface 10 by a spacer system formed by a porous layer 16. The gas, particularly air, is held between the grid 2 and the surface 10 in the porous layer 16.

[0075] FIG. 11 shows a schematical representation of another embodiment of an object 14 able to maintain a gas layer on the surface. On the surface 10 is mounted a device comprising a grid 2 which is kept in spaced relation to the surface 10 by wall-like spacers 20. In the schematical representation of the embodiment of an object 14 which is able to maintain a gas layer on the surface as shown in FIG. 12, the grid 2 is supported in spaced relation to the surface by wall-like spacers 22 which form compartments 18 on the surface. As a result the gas layer held between the grid 2 and the surface 10 also is divided into separate gas volumes.

[0076] FIGS. 13 and 14 schematically show embodiments of a surface 10 on which is mounted a device comprising a grid structure with wall-like spacers 22, which provide oblong, hexagonal compartments 18 as shown in FIG. 13 or arrow-like compartments 18 as shown in FIG. 14 on the surface 10.

[0077] FIG. 15 shows a schematical embodiment of an object 14 that is able to maintain a gas layer on the surface. The surface is compartimentized and comprises several compartments 18 each comprising a separate gas volume. The grid 2 is supported by the wall-like spacers 22 and the spacers 12.

[0078] FIGS. 16, 17 and 18 show schematical representations of a compartments comprising through openings in the wall-like spacers 22. The FIG. 16 shows rectangular through openings 24, the FIG. 17 triangular through openings 26, and the FIG. 18 shows round holes 28 in the wall-like spacers 22. The through openings 24, 26 and 28 allow for a conjunction of the gas layer, but the construction will separate the compartments upon pressure.

[0079] FIGS. 19, 20 and 21 show schematical representations of an object 14 that is able to maintain a gas layer with several compartments 18, which are interconnected. In the FIG. 19 each of the compartments are interconnected via through openings 24. In FIG. 20 each compartment is interconnected with one adjacent compartment. One of the wall-like spacers 22 of each compartment comprises an through openings 24. In FIG. 21 the compartments aligned in a row are interconnected via through openings 24 in the wall-like spacers 22.

[0080] FIG. 22 shows a schematical representation of a top view of a compartment of a surface that is able to maintain a gas layer. The grid structure 2 is supported by the wall-like spacers 22. The mesh openings are of varying size, wherein the mesh opening is smaller at the left of the compartment. Such variations in the mesh openings can compensate for variations in the in the mechanical stress such as drag acting on the compartment.

[0081] FIG. 23 shows a schematical representation of a cross section of a compartment. The grid structure 2 is supported by the wall-like spacers 22 on the surface 10. The filaments 4 forming the grid structure 2 show varying cross sections. Such varying cross sections of the filaments can compensate for variations in the in the mechanical stress such as drag acting on the grid structure 2.

[0082] FIG. 24 shows a schematical representation of a surface 10 comprising spacers 12 suitable to support a grid structure, which is not shown, according to a further embodiment. The distance between the spacers 12 varies. The spacers 12 also vary in the dimensions of the spacers. Such variations in the distance and dimensions of the spacers also allow for a compensation of variations in the in the mechanical stress such as drag acting on the grid structure.

[0083] FIG. 25 shows a schematical representation of a grid structure 2, wherein the grid structure 2 comprises protrusions 30 on the grid surface. The protrusions 30 are provided in regular distance from each other. Such protrusions allow for providing an enlarged gas or air layer on the surface extending to the tips of the protrusions.

[0084] FIG. 26 shows a schematical representation of a grid structure 2, wherein the grid structure 2 comprises hydrophilic protrusions 30 on junctions of the grid structure 2. The hydrophilic protrusions 30 are provided on the top surface of the grid, which will contact the fluid when a surface equipped with the grid is immersed in a fluid. Such hydrophilic protrusions 30 may provide for a pinning effect and stabilize the gas-liquid-interphase.

EXAMPLE 1

[0085] A Teflon grid having a mesh size of 0.1 mm and a steel net having a mesh size of 1 mm were fixed on plastic containers with a rectangular cross section having external dimensions of 25254 mm.sup.3, and dimensions of a recess of 22222 mm.sup.3. The grids and containers were hydrophobized with Tegotop 210 (Evonik) and immersed in water. The containers were able to retain a gas film on the surface for several weeks under water.

EXAMPLE 2

[0086] The effect of different dimension of openings in grid structured on the stability of gas films was determined. For this, round, hexagonal and rectangular opening of a minimal hole diameter of 300 m to a major hole diameter of 8 mm were used.

[0087] Twelve different grid structures were used: metal perforated plates with round openings of different sizes (1.5-8 mm) (JAERA GmbH & Co. KG; Dillinger Fabrik gelochter Bleche GmbH) and metal perforated plates with hexagonal apertures of two sizes (2 mm and 6 mm), an epoxy replica (TOOLCRAFT Epoxyharz L; Conrad Electronic SE) of five of these perforated plates (Rv 1.5/2.5; Rv 2/3; Rv 3/4; SkL 2/2.5), two woven wire cloths (agar Scientific), a plastic web screen (Tesa insect stop, tesa SE) and two Teflon webs (ETFE Screen, 20 mesh and 50 mesh; TED PELLA, INC.). Table 1 summarizes the dimensions of the apertures of the perforated plates, Table 2 summarizes the dimensions of the mesh size of the webs and the woven wire web.

TABLE-US-00001 TABLE 1 dimensions of the apertures of the perforated plates from metal and epoxy resin hole diameter center distance indication perforation [mm] [mm] Rv 1.5/2.5 round, staggered 1.5 2.5 Rv 2/3 round, staggered 2 3 Rv 3/4 round, staggered 3 4 Rv 6/8 round, staggered 6 8 Rv 8/12 round, staggered 8 12 SkL 2/2.5 hexagonal 2 2.5 SkL 6/6.7 hexagonal 6 6.7

TABLE-US-00002 TABLE 2 mesh size of the webs and woven wire cloth indication mesh size [mm] wire web, fine ca. 0.35 wire web, coarse 0.6 Teflon grid, fine 0.3 Teflon grid, coarse 0.9 plastic web screen 1.2

[0088] Experiments were performed using each of the grid structures on two different types of samples with chambers of two different sizes: a square chamber having an edge length of 12 mm and a depth of 2 mm, and a smaller hexagonal chamber having a diameter of 7 mm and a depth of 4 mm. The grids were fixed on the respective samples (9 chambers below the grid in case of the square chambers, 7 chambers below the grid in case of the hexagonal chambers) with glue and hydrophobized with Tegotop 210 (Evonik). Afterwards the samples equipped with the different grids were immersed into water to a depth of 20 mm and fixed by using putty (plastic-fermit Installationskitt, fermit GmbH).

[0089] After two weeks the samples were cautiously removed from the water. Using indicator paper the bottom of the chambers was examined in view of moisture to determine if a water ingress had occurred. For the samples with the bigger chambers of an edge length of 12 mm, nine pieces of indicator paper were used (one in each chamber), the smaller chambers were sampled using seven papers (one in each chamber).

[0090] Regarding the grids fixed on the 12 mm-chambers, using the fine Teflon grid with a mesh size of 0.3 mm it was seen that six out of nine test sites remained dry, representing the best result achieved. Also the fine wire web with a mesh size of 0.35 mm showed a stable gas film on the bottom surface. Regarding the grids fixed on the 7 mm-chambers, the fine Teflon grid with a mesh size of 0.3 mm showed that all seven test sides remained dry, while for the coarse Teflon grid with a mesh size of 0.9 mm only one test side was moist. Also for the perforated plate Rv 1.5/2.5 all seven test sides remained dry. This shows that a stable gas film was kept using all structures and mesh sizes.

[0091] The test run was repeated using similar conditions. In the second run, regarding the grids fixed on the 12 mm-chambers, the fine Teflon grid and the fine wire web again showed best results. Also the plastic web screen (1.2 mm), the coarse Teflon grid and the perforated metal plate Rv 2/3 showed good results. The bottom of the chambers under the fine and the coarse wire webs remained dry over the test period.

[0092] Regarding the grids fixed on the 7 mm-chambers, only the perforated metal plates Rv 3/4 and Rv 2/2.5 showed occasional moist test sites. It is assumed that these were caused by a flawed coating of the grids.

[0093] The results of the first and second test run show that the grid structures except the biggest grids Rv 6/8 and Rv 8/12 provided a stable gas film for the test period of two weeks. The fine Teflon grid with a mesh size of 0.3 mm showed the best test results. Generally it was seen that the smaller and deeper chamber (7 mm) provided better results compared with the 12 mm-chamber. However, all the tested grids except the biggest grids Rv 6/8 and Rv 8/12 and chambers were able to stable keep a gas layer on the surface when immersed into water over two weeks.