AN ANTI-FOULING TREATED HEAT EXCHANGER AND METHOD FOR PRODUCING AN ANTI-FOULING TREATED HEAT EXCHANGER

Abstract

An anti-fouling coated heat exchanger in which the anti-fouling coating is a non- continuous silicon oxide film, and a method of making an anti-fouling coated heat exchanger in which the anti-fouling coating is a continuous or discontinuous silicon oxide film which can be formed with high smoothness on the internal surfaces of a closed heat exchanger.

Claims

1. An anti-fouling treated closed heat exchanger comprising a closed heat exchanger comprising a metal surface which is brought into contact with a heat exchange fluid in use, on which surface is formed a non-continuous coating of silicon oxide which at least partially levels the surface microtopography of the metal surface.

2. A-The anti-fouling treated closed heat exchanger according to claim 1, wherein the leveling of the surface microtopography by the silicon oxide coating results in a surface roughness of lower than 90% of that of the uncoated metal surface.

3. A-The anti-fouling treated closed heat exchanger according to claim 1 wherein the thickness of the silicon oxide coating is below 1 .Math.m.

4. A-The anti-fouling treated closed heat exchanger according to claim 1, wherein the ratio of Si:O in the silicon oxide coating is between 1.5 and 2.

5. A-The anti-fouling treated closed heat exchanger according to claim 1, wherein the proportion of the surface area of the metal surface which is covered by the non-continuous coating of silicon oxide is at least 70% and is less than 100% .

6. The anti-fouling treated closed heat exchanger according to claim 1, wherein the surface roughness Ra of the non-continuous silicon oxide film is at most 100 nm measured over a 5 micron distance.

7. A-The anti-fouling treated closed heat exchanger according to claim 1, wherein the metal surface is a steel surface.

8-10. (canceled)

11. A-The anti-fouling treated closed heat exchanger according to claim 40, wherein the heat exchanger further comprises a self-assembled monolayer of covalently bonded PEG on the silicon oxide coating.

12. (canceled)

13. The anti-fouling treated closed heat exchanger according to claim 40, wherein the heat exchanger further comprises a self-assembled monolayer of 1H,1H,2H,2H-perfluorodecyltrichlorosilane (FDTS) on the silicon oxide coating.

14-30. (canceled)

31. The anti-fouling treated closed heat exchanger according to claim 4, wherein the ratio of Si:O in the silicon oxide coating is between 1.6 and 1.9.

32. The anti-fouling treated closed heat exchanger according to claim 31, wherein the ratio of Si:O in the silicon oxide coating is between 1.7 and 1.8.

33. The anti-fouling treated closed heat exchanger according to claim 5, wherein the proportion of the surface area of the metal surface which is covered by the non-continuous coating of silicon oxide is at least 80% and less than 98%.

34. The anti-fouling treated closed heat exchanger according to claim 33, wherein the proportion of the surface area of the metal surface which is covered by the non-continuous coating of silicon oxide is at least 90% and less than 95%.

35. The anti-fouling treated closed heat exchanger according to claim 3 wherein the thickness of the silicon oxide coating is below 0.5 .Math.m.

36. The anti-fouling treated closed heat exchanger according to claim 35 where the thickness of the silicon oxide coating is below 0.1 .Math.m.

37. The anti-fouling treated closed heat exchanger according to claim 2, wherein the leveling of the surface microtopography by the silicon oxide coating results in a surface roughness of lower than 50% of that of the uncoated metal surface.

38. The anti-fouling treated closed heat exchanger according to claim 37, wherein the leveling of the surface microtopography by the silicon oxide coating results in a surface roughness of lower than 20% of that of the uncoated metal surface.

39. The anti-fouling treated closed heat exchanger according to claim 38, wherein the leveling of the surface microtopography by the silicon oxide coating results in a surface roughness of lower than 5% of that of the uncoated metal surface.

40. The anti-fouling treated closed heat exchanger according to claim 1, wherein the surface adhesion strength of mineral scaling from a calcium-based salt to the surface is reduced by at least 50%, wherein the surface adhesion strength of an asphaltene to the surface is reduced by at least 50% compared with the uncoated metal surface, wherein the surface adhesion strength of a biofilm to the surface is reduced by at least 50% compared with the uncoated metal surface, or wherein the surface adhesion strength of a solidified salt in a molten salt melt to the surface is reduced by at least 50% compared with the uncoated metal surface.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0110] The part and method according to the invention will now be described in more detail with regard to the accompanying figures. The figures show one way of implementing the present invention and is not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

[0111] FIG. 1a shows a schematic drawing of a cross-section of an initial surface.

[0112] FIG. 1b shows a schematic drawing of a cross-section of a surface (11) where a coating layer (12) has been formed, using the described method. FIG. 1c shows a schematic drawing of a cross-section of a surface of a brazed heat exchanger, where the brazing material (13) partially covers the initial surface, and the silicon oxide coating, covers the initial surface and the brazing material.

[0113] FIGS. 2a and 2b show schematic drawings of a cross-section of an initial surface (21) where the surface roughness (24) has been lowered through the deposition of the coating layer (22), such as silicon oxide, using the described method to yield a lower final surface roughness (25). In FIG. 2a, the coating layer (22) is a continuous layer, in that all of the initial surface (21) is coated. However, in FIG. 2b, the coating layer (22) is discontinuous (non-continuous), as the voids in the initial surface (21) are partially filled, thus reducing the initial surface roughness (24) to the lower value (25), corresponding to the initial surface roughness (24) minus the layer thickness (26) of layer (22).

[0114] FIG. 3 shows a schematic drawing of a heat exchanger (31) comprising internal areas to be anti-fouling treated. A liquid precursor (34) is pumped into the heat exchanger, with a certain pumping speed (33). Inside the heat exchanger, the level of the liquid precursor changes with a certain linear velocity (32), in relation to the interior wall of the heat exchanger.

[0115] FIG. 4 shows a schematic drawing of a heat exchanger (41), where a gas (42) is pumped through the heat exchanger at a certain velocity.

[0116] FIG. 5a shows a schematic drawing of the liquid precursor as it forms on the surface (51) of the heat exchanger during the draining process, with an initial thickness (52). FIG. 5b shows the thickness (53) of the solidified (non-liquid) precursor layer after the solvent has evaporated. The evaporation rate is defined as the change in coating layer thickness over time.

DETAILED DESCRIPTION OF AN EMBODIMENT

Example 1

[0117] In an example, a closed heat exchanger was filled with a liquid ceramic precursor, where the solvent was 5:1 hexamethyldisiloxane:octamethyltrisiloxane, and the solid content of HSQ was 5 wt%. The liquid precursor was drained from the heat exchanger using a phase compensation peristaltic pump, with a pumping speed so that the linear velocity of the draining speed was 1 mm/s. When drained, the heat exchanger was flushed with a stream of air, at a flow of 1 liter/min, for 60 seconds. The heat exchanger was then cured at 700° C. for 2 hours in a nitrogen atmosphere.

[0118] A non-continuous smooth (uniform) film with an average thickness of 200 nm was formed on all inside surfaces of the heat exchanger.

Example 2

[0119] In an example, a closed heat exchanger was filled with a liquid ceramic precursor, where the solvent was MIBK, and the solid content of HSQ was 10 wt%. The liquid precursor was drained from the heat exchanger using a phase compensation peristaltic pump, with a pumping speed so that the linear velocity of the draining speed was 10 mm/s. When drained, the heat exchanger was flushed with a stream of air, at a flow of 1 liter/min, for 60 seconds. The heat exchanger was then cured at 700° C. for 2 hours in an argon atmosphere.

[0120] A non-continuous smooth (uniform) film with an average thickness of 500 nm was formed on all inside surfaces of the heat exchanger.

Example 3

[0121] In an example, a closed heat exchanger was filled with a liquid ceramic precursor, where the solvent was 2:1 hexamethyldisiloxane:octamethyltrisiloxane, and the solid content of HSQ was 20 wt%. The liquid precursor was drained from the heat exchanger using a phase compensation peristaltic pump, with a pumping speed so that the linear velocity of the draining speed was 1 mm/s. When drained, the heat exchanger was flushed with a stream of air, at a flow of 0.5 liter/min, for 30 seconds. The heat exchanger was then cured at 1000° C. for 2 hours in vacuum. A non-continuous smooth (uniform) film with an average thickness of 1000 nm was formed on all inside surfaces of the heat exchanger.

Example 4

[0122] In an example, a copper brazed heat exchanger is filled with a liquid ceramic precursor, where the solvent is 2:1 hexamethyldisiloxane:octamethyltrisiloxane, and the solid content of HSQ is 15 wt%. The liquid precursor is drained from the heat exchanger using a phase compensation peristaltic pump, with a pumping speed so that the coating speed is 1 mm/s. The heat exchanger is then cured at 700° C. for 2 hours in a nitrogen atmosphere.

[0123] A non-continuous smooth (uniform) film with an average thickness of 1000 nm is formed on all inside surfaces of the heat exchanger.

Comparative Example 1

[0124] In a comparative example, a copper brazed heat exchanger was filled with a liquid ceramic precursor, where the solvent was 1:3 hexamethyldisiloxane:octamethyltrisiloxane, and the solid content of HSQ was 20 wt%. The liquid precursor was drained from the heat exchanger using a phase compensation peristaltic pump, with a pumping speed so that the coating speed was 1 mm/s. The heat exchanger was then cured at 700° C. for 2 hours in a nitrogen atmosphere.

[0125] A non-uniform silica film had formed mainly around the brazing points. Around the brazing points the thickness of the silica layer was up to 2 .Math.m. On other surfaces inside the heat exchanger, the thickness was below 100 nm. This is attributed to the concentration of the reactive silicon oxide precursor (liquid ceramic precursor) in the coating solution used. The surface energy of the solution at this concentration is believed not to allow the solution to form a highly smooth coating in the vicinity of the brazing points.

[0126] Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms “comprising” or “comprises” do not exclude other possible elements or steps. Also, the mentioning of references such as “a” or “an” etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.

[0127] All patents and non-patent references cited in the present application are also hereby incorporated by reference in their entirety.