Subsea power module

Abstract

A subsea power module including: a tank having a tank wall provided with an outwardly protruding corrugation, a power device arranged in the tank, a dielectric liquid which fills the tank, for cooling the power device, a pump configured to circulate the dielectric liquid in the tank, wherein the pump has a pump inlet and a pump outlet, a duct arranged in the corrugation such that a chamber is formed between a tip of the corrugation and the duct, wherein the duct has a duct inlet connected to the pump outlet, and wherein the duct is provided with at least one duct outlet opening into the chamber, and a distancing structure configured to space apart an outer surface of the duct facing the tank wall and the tank wall in the corrugation, whereby gaps are formed between the duct and the tank wall in the corrugation, enabling dielectric liquid that has been discharged through the at least one duct outlet into the chamber to be squeezed out from the chamber and the corrugation, and flow towards the pump inlet.

Claims

1. A subsea power module comprising: a tank having a tank wall provided with an outwardly protruding corrugation, a power device arranged in the tank, a dielectric liquid which fills the tank, for cooling the power device, a pump configured to circulate the dielectric liquid in the tank, wherein the pump has a pump inlet and a pump outlet, a duct arranged in the corrugation such that a chamber is formed between a tip of the corrugation and the duct, wherein the duct has a duct inlet connected to the pump outlet, and wherein the duct is provided with at least one duct outlet opening into the chamber, and a distancing structure configured to space apart an outer surface of the duct facing the tank wall and the tank wall in the corrugation, whereby gaps are formed between the duct and the tank wall in the corrugation, enabling dielectric liquid that has been discharged through the at least one duct outlet into the chamber to be forced out by the pump from the chamber and the corrugation, and flow towards the pump inlet.

2. The subsea power module as claimed in claim 1, wherein the distancing structure is a liner arranged between the duct and the tank wall in the corrugation, and wherein the distancing structure has a varying thickness causing the formation of the gaps.

3. The subsea power module as claimed in claim 1, wherein the distancing structure is a mesh.

4. The subsea power module as claimed in claim 3, wherein the mesh is made of wires that cross over, forming cross-over points which define a maximum thickness of the mesh, wherein the gaps are formed between the cross-over points and the duct and/or the tank wall.

5. The subsea power module as claimed in claim 3, wherein the mesh is a metal mesh.

6. The subsea power module as claimed in claim 1, wherein the distancing structure is formed by protrusions provided on the outer surface of the duct.

7. The subsea power module as claimed in claim 6, wherein the protrusions are pins or stubs.

8. The subsea power module of claim 1, comprising an elastic sheet arranged between the duct and the tank wall in the corrugation.

9. The subsea power module of claim 1, wherein the duct has an elastic portion configured to enable adaptation of the shape of the duct to the shape of the corrugation.

10. The subsea power module of claim 1, comprising a clamping structure provided with a resilient member configured to press the duct into the corrugation.

11. The subsea power module of claim 1, comprising a plurality of duct outlets arranged one after the other along the length of the duct in the corrugation.

12. The subsea power module of claim 1, wherein the duct has a longitudinal axis, and wherein the duct has a trapezoidal cross-sectional shape along the longitudinal axis.

13. The subsea power module of claim 1, wherein the duct has a vertical orientation in the tank and the duct inlet is arranged in a top portion of the duct.

14. The subsea power module of claim 1, wherein the power device is a power converter.

15. The subsea power module as claimed in claim 2, wherein the distancing structure is a mesh.

16. The subsea power module as claimed in claim 2, wherein the mesh is a metal mesh.

17. The subsea power module of claim 2, comprising an elastic sheet arranged between the duct and the tank wall in the corrugation.

18. The subsea power module of claim 2, comprising a clamping structure provided with a resilient member configured to press the duct into the corrugation.

19. The subsea power module as claimed in claim 4, wherein the mesh is a metal mesh.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The specific embodiments of the inventive concept will now be described, by way of example, with reference to the accompanying drawings, in which:

(2) FIG. 1 is a schematic perspective view of a subsea power module;

(3) FIG. 2 schematically shows a sectional view of a subsea power module;

(4) FIG. 3 is a schematic perspective view of a duct;

(5) FIG. 4 is a cross-sectional view of an example of a duct arranged in a corrugation;

(6) FIG. 5 schematically shows a mesh;

(7) FIG. 6 is a cross-sectional view of another example of a duct arranged in a corrugation;

(8) FIG. 7 is a cross-sectional view of another example of a duct arranged in a corrugation; and

(9) FIG. 8 is a cross-sectional view of yet another example of a duct arranged in a corrugation.

DETAILED DESCRIPTION

(10) The inventive concept will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplifying embodiments are shown. The inventive concept may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. Like numbers refer to like elements throughout the description.

(11) FIG. 1 shows a perspective view of an example of a subsea power module 1. The subsea power module 1 may for example be a subsea power converter module. The subsea power module 1 may be adapted to withstand a hydrostatic pressure in the range of 10 to 100 or more bar. The subsea power module 1 is configured to be installed on the seabed as part of a subsea electrical infrastructure.

(12) The subsea power module 1 comprises a tank 3. The tank 3 is preferably made of a metal material such as stainless steel. The tank 3 has tank walls 3a. The tank walls 3a may have a thickness that is large enough to withstand the ambient hydrostatic pressure at the seabed. Alternatively, the subsea power module 1 may comprise a pressure compensator such as a bellow. In the latter case, the tank walls 3a can be made thinner than in the former case.

(13) The tank wall 3a is provided with a plurality of corrugations 3b. The corrugations 3b extend outwards from the subsea power module 1. The corrugations 3b are arranged in parallel with each other. The tank 3 has a top 5a formed by a top plate or structure 4 and a bottom 5b formed by a bottom plate or structure 5c. The corrugations 3b extend in a direction from the top 5a towards the bottom 5b. The corrugations 3b hence have a vertical extension when the subsea power module 1 stands on its bottom plate 5c. The corrugations 3b may be straight along their main axis of extension.

(14) Turning now to FIG. 2 a schematic simplified cross-sectional view of subsea power module 1 is shown.

(15) The subsea power module 1 comprises a power device 7. The power device 7 is arranged in the tank 3. The power device may for example be a power converter or a transformer including windings and a magnetic core.

(16) The subsea power module 1 comprises a dielectric liquid 8. The power device 7 is immersed in the dielectric liquid 8. The dielectric liquid 8 fills the tank 3.

(17) The subsea power module 1 comprises a pump 9. The pump 9 is configured to circulate the dielectric liquid 8 in the tank 3 by forced convection. The pump 9 comprises a pump inlet 9a and a pump outlet 9b. The pump inlet 9a is arranged to suck dielectric liquid 8 into the pump 9.

(18) The subsea power module 1 comprises one or more ducts 11. In the following the subsea power module 1 will be exemplified with a plurality of ducts 11 although examples of subsea power modules comprising a single duct are also envisaged.

(19) Each duct 11 has a duct inlet 11a connected to the pump outlet 9b. The ducts 11 are thus configured to be fed with the dielectric liquid 8 from the pump 9 via the pump outlet 9b. The pump 9 is configured to pump the dielectric liquid 8 into the ducts 11 via the duct inlets 11a. The ducts 11 also have one or more duct outlets for discharging the dielectric liquid 8, which will be explained in more detail in the following. In this manner, the power device 7 is cooled by forced convection by the dielectric liquid 8. In the case that only one duct outlet is provided in a duct, it may preferably be arranged midway or substantially midway along the duct, for example in a region of ⅓ to ⅔ of the total length of the duct.

(20) The ducts 11 are arranged in a respective corrugation 3b of the tank wall 3a. The ducts 11 thus extend parallel with the corrugations 3b. The duct inlets 11a are arranged in a top portion of the ducts 11.

(21) The subsea power module 1 may comprise a manifold 13 connected to the pump outlet 9b. The ducts 11 may be connected to the manifold 13. The duct inlets 11a may be connected to the manifold 13 for pumping the dielectric liquid 8 into the ducts 11.

(22) FIG. 3 schematically shows a perspective view of one of the ducts 11. The duct 11 is connected to the manifold 13 via its duct inlet 11a. The exemplified duct 11 is provided with a plurality of duct outlets 11b. The duct outlets 11b are distributed along the length of the duct 11. The duct outlets 11b may be arranged one after the other along a longitudinal axis A of the duct 11. The dielectric fluid 8 that has been pumped into the duct 11 via the duct inlet 11a is discharged from the duct 11 through the duct outlets 11b. The duct 11 is arranged in a corrugation 3b and thus the duct outlets 11b are configured to discharge the dielectric liquid 8 into the corrugation 3b.

(23) FIG. 4 shows a cross-sectional view of a duct 11 arranged in a corrugation 3b. The corrugation 3b may have a generally trapezoidal cross-sectional shape. The duct 11 may have a generally trapezoidal cross-sectional shape. In general, the duct 11 may have a cross-sectional shape corresponding to that of the corrugation 3b.

(24) In cross-section, the corrugation 3b may have a tapering angle α. The corrugation 3b may taper in a direction towards its tip 3c. Preferably, the duct 11 also has a tapering angle α to obtain a snug/tight fit of the duct 11 in the corrugation 3b.

(25) The duct 11 is arranged in the corrugation 3b such that a chamber 14 is formed between the tip 3c of the corrugation 3b. The duct 11 is spaced apart from the tip 3c, i.e. the tip of the inner tank wall 3a in the corrugation 3b. The duct 11 does hence not extend fully into the corrugation 3b. The chamber 14 thus extends in the longitudinal direction of the corrugation 3b along the extension of the duct 11. The duct outlets 11b open into the chamber 14. The dielectric liquid 8 that is discharged from the duct outlets 11b of the duct 11 hence flows into the chamber 14.

(26) The subsea power module 1 comprises a clamping structure 17 including a resilient member 17a. The resilient member 17a is configured to press the duct 11 into the corrugation 3b and maintain the duct 11 in this position. The resilient member 17a may for example be a spring.

(27) The clamping structure 17 may include a plate 17b fixed to the inner tank wall 3a. The resilient member 17a may be arranged between the plate 17b and the duct 11 such that the resilient member 17a can push or press the duct 11 towards the tip 3c of the corrugation 3b.

(28) The subsea power module 1 comprises a distancing structure 15. The distancing structure 15 is configured to space apart an outer surface of the duct 11 facing the inner tank wall 3a, and the inner tank wall 3a of the corrugation 3b such that gaps are formed between the duct 11 and the tank wall 3a. The dielectric liquid 8 that has been discharged from the duct outlets 11b into the chamber 14 is thus able to be squeezed out from the chamber 14 and the corrugation 3b via the gaps. This may be achieved by providing a sufficiently high pressure with the pump 9 to enable the dielectric liquid 8 to escape the chamber 14 and the corrugation 3b through the gaps.

(29) The gaps may for example be provided by a distancing structure 15 in the form of a liner that has varying thickness. The gaps are thus formed between the distancing structure 15 and the duct and/or the inner tank wall 3a.

(30) In the example shown in FIG. 4, the distancing structure 15 is a liner arranged between the duct 11 and the tank wall 3a in the corrugation 3b. The distancing structure 15 may in this case for example be a mesh. The mesh may be made of metal such as stainless steel. Alternatively, the distancing structure may be formed by a plurality of protrusions on the outer surface of the duct, as will be explained with reference to FIG. 8.

(31) In the case the distancing structure 15 is a mesh, the gaps may be formed by cross-over points. FIG. 5 shows an example of a distancing structure 15 in the form of a mesh. The mesh is formed by a plurality of wires 15a and 15b that cross over. Cross-over points 15c, which are the points where the wires 15a and 15b cross each other, are thereby formed. The cross-over points 15c define a maximum thickness of the mesh. Gaps are formed between the cross-over points 15c and the duct 11 and/or between the cross-over points 15c and the inner tank wall 3a in the corrugation 3b. These gaps enable the dielectric liquid 8 to escape from the chamber 14 and the corrugation 3b when a sufficiently high pump pressure is provided by the pump 9.

(32) FIG. 6 shows an example of a subsea power module 1 that comprises an elastic sheet 19 arranged between the distancing structure 15 and the duct 11. The elastic sheet 19 has an elastic thickness depending on the pressure applied onto its main surfaces. A snug/tight fit between the outer surface of the duct 11 and the distancing structure 15, in case it is a liner, or the duct 11 and the inner tank wall 3a may thus be obtained. An essentially uniform size of the gaps may thus be obtained, in accordance with a desired dielectric liquid side heat transfer coefficient h.sub.dielectric-wall.

(33) FIG. 7 shows another example of a duct 11′. The duct 11′ is similar to the previously presented ducts 11. The duct 11′ however has an elastic portion 11c. The elastic portion 11c is configured to make the duct 11′ mechanically flexible. The duct 11′ can thereby adapt its shape to that of the corrugation 3b to obtain a snug/tight fit between the duct 11′ and the inner tank wall 3b and/or with the distancing structure 15 to obtain an essentially uniform size of the gaps. Thus, in case the tapering angle α of the corrugation and the tapering angle of the duct differ, a snug fit may still be obtained.

(34) The elastic portion 11c may for example be a fold or duct corrugation arranged in a side of the duct 11′ that is opposite to the duct outlets 11b.

(35) Deformation of the duct 11′ may thus be obtained as shown by the two facing arrows, to enable adaption of the shape of the duct 11′ to that of the corrugation 3b.

(36) In the example shown in FIG. 7, the clamping structure 17 may be provided with two resilient members 17a, arranged symmetrically on each side of the elastic portion 11c.

(37) FIG. 8 shows another example of a duct 11″. The duct 11″ is similar to the duct 11 but instead of utilising a distancing structure in the form of a liner the distancing structure 15″ is in this case formed by a plurality of protrusions arranged on the outer surface of the duct 11″. The protrusions may for example be pins or studs. The gaps are formed between the protrusions, the outer surface of the duct 11″ and the corrugation 3b.

(38) The inventive concept has mainly been described above with reference to a few examples. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended claims.