Power equipment for use underwater

Abstract: Power equipment for use underwater, e.g. in the form of an electrical sub-station, incorporates heat exchange equipment for dissipation of heat to the surrounding water. The power equipment comprises a pressure vessel (110) having a chamber (111) in which at least one power device (113) is mounted. A further chamber (112) is at least partially filled with a fluid (120), is in heat conductive relationship with the power device and also has a wall (122) in contact with the water surrounding the power equipment. The power device (113) produces heat which is transmitted to the further chamber (112) and is then transmitted to the surrounding water.

Description: This invention is concerned with power equipment for use underwater, e.g. under the sea, such power equipment incorporating at least one power device. In the context the term 'power device' is to be interpreted generally as covering all forms of prime movers, e.g. engines, as well as power transmission devices (e.g. mechanical, electrical, pneumatic, hydraulic), but the invention is particularly applicable to power equipment incorporating a power device in the form of an electrical sub-station incorporating a transformer and its associated control gear. In prior patent document GB-A-1 604 978 a transformer for use underwater is located within a housing that defines a first oil-filled chamber. A second oil-filled chamber is separated from the first chamber by bellows. To accommodate thermal expansion of the oil, pressures between the surrounding water and the first chamber, and also between the chambers, are equalised by egress/ingress of oil/water from/into the second chamber 8. In prior patent document US-A-5 000 252, heat is transferred from a heat source to the environment via an intermediate heat sink comprising the walls of a container. Power equipment incorporating power devices will always produce energy in the form of heat and it is necessary for heat to be removed from the equipment, e.g. by conduction, convection or radiation. At first sight it might appear that for power equipment used underwater there would be no particular cooling problem since the water itself would provide a large heat sink. However, for certain equipment producing relatively large quantities of heat it will be necessary to take special and specific measures to ensure efficient and effective removal of heat from the power equipment into the surrounding water. Moreover, maintenance and repair operations of equipment used underwater is time-consuming and expensive, and there is a need to ensure that such equipment can operate with long maintenance intervals. The aim of the invention is to provide power equipment with an efficient cooling arrangement which will operate in an underwater location and without attention for long periods of time. It is intended that the invention provides power equipment for use when submerged in water, the power equipment comprising an exterior casing enclosing at least one power device of a type which produces heat when in use, the exterior casing being in heat exchange relationship with the at least one power device so as to put the at least one power device into heat exchange relationship with water surrounding the exterior casing when the power equipment is submerged. Accordingly, the invention provides power equipment for use underwater, the power equipment comprising: a first chamber containing at least one power device which produces heat in use, and a second chamber at least partially filled with a fluid, the second chamber being in heat conductive relationship with the power device and also having a wall in contact with the surrounding water when the power equipment is submerged, whereby heat produced by the power device is transmitted to the second chamber and thence transmitted to the surrounding water, characterised in that the first and second chambers both being within a pressure vessel. The fluid in the second chamber may be a liquid, e.g. water. The second chamber may be connected to a volume compensating means to which liquid may flow from the second chamber or vice versa. In a further embodiment the second chamber is only partially filled with liquid and a volume is defined in the second chamber above the liquid; the volume above the liquid may be connected to an evacuation means actuatable to reduce the pressure in said volume. It is also envisaged that the second chamber may be connected by conduit means with a heat exchange arrangement which is disposed adjacent the power device; the first chamber may have a volume containing a further fluid and the heat exchange arrangement may comprise a coaxial-tube arrangement for the flow of said further fluid therethrough. Further the coaxial-tube arrangement may comprise an outer tube extending outwardly from the first chamber and in contact with said surrounding water and an inner tube disposed within the outer tube and terminating at one end within the first chamber near to the power device, said further fluid during use of the power equipment being caused to flow first inside the inner tube and then between the outer and inner tubes. The second chamber may have a domed element whose exterior domed surface provides the wall in contact with the surrounding water for the transfer of heat thereto from the fluid in the second chamber, and the surface of the domed element in contact with the water may be formed with corrugations, vanes or ribs. Movement of the fluid in the power equipment may occur by means of natural circulation and/or by forced circulation. Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a sectional side view through power equipment in accordance with the invention, adapted for use in an underwater, especially an undersea, location; Figures 2-6 show similar side views of modified versions of Figure 1. The equipment will normally be fixedly positioned underwater, and in such a circumstance it could be attached to a structure such as an off-shore drilling rig but it is particularly envisaged that it will be located on the sea-bed. In the embodiment of Figure 1, power equipment comprises a pressure vessel 110 having a chamber 111 incorporating the heat-producing power devices and a chamber 112 at least partially filled with liquid 120, e.g. water, methyl alcohol or a proprietary refrigerant. The chamber 112 has a wall 121, which may be arranged vertically, horizontally or at any angle as required and a dome-shaped element 122 affixed to or integral with the wall 121. The chamber 112 is shown as constituting the right hand end of the pressure vessel - there may be a similar chamber at the left hand end of the vessel. Adjacent to or, at the least, in heat-conducting relationship with the wall 121 there is arranged the heat producing power device(s) 113 of the power equipment which will for example comprise a prime mover, e.g. an engine and/or transmission equipment, e.g. of mechanical, electrical, hydraulic, pneumatic form. The device(s) may, if appropriate, be mounted on to wall 121. Heat from the heat source is conducted through wall 121 to the liquid 120 in chamber 112. The heat is conducted through liquid 120, and will be dissipated into the surrounding water. There will of course be a degree of natural circulation of the liquid within the chamber 112 associated with the heat transfer and it is particularly envisaged that the equipment will operate with natural circulation only. However, the chamber 112 may incorporate a forced circulation means, e.g. a pump or swirler, and a magnetic swirler arrangement may be appropriate since this requires no outside connection. To assist transfer of heat to the surrounding water and to increase the area available for such transfer the domed element 122 may be formed with ribs, vanes or corrugations. Attached to the chamber 112 via a conduit 115 is a compensator 116, e.g. including a bellows; should there be heat-induced expansion of the liquid to a volume greater than that of the chamber 112, liquid may flow to the compensator 116 and, on the other hand, the volume enclosed by bellows 116 constitutes a reservoir of liquid for the chamber 112. The embodiment of Figure 2 differs from that of Figure 1 in that no compensator is provided and it is arranged that the chamber 112 is only partially filled with liquid. In consequence, a volume 130 devoid of liquid is formed at the upper part of the chamber 112 and in taking up heat from the heat source, the liquid is able to boil and form a vapour in volume 130. The vapour will assist in heat transfer to the outside water and the latent heat required to turn the liquid into vapour in the first place will give efficient and effective heat transfer, the vaporised liquid will condense on the surface of the volume of the domed element. The embodiment of Figure 3 effectively constitutes a modification of the embodiment of Figure 2, in which the volume 130 above the heat transfer liquid is connected to an evacuating pump (not shown) which will ensure that the volume 130 is put under very low pressure, (e.g. of the order of 30mm Hg absolute) whereby the temperature at which liquid 120 boils is reduced, where the pressure is 30mm Hg, then water in the chamber will boil at approximately 30°C. The evacuating pump is connected to volume 130 via a line 140 incorporating a valve 141. The embodiment of Figure 4 incorporates the evacuation line 140 of Figure 3 but, in addition, a circulating arrangement 150 is provided whereby liquid from the chamber 112 is circulated through a heat exchanger 160. The heat exchanger 160 will be mounted adjacent to or at least in heat conducting relationship with the heat producing power device 113 and liquid is caused to flow via lines 161, 162 from a lower region of the chamber 111 through the heat exchanger 160 and into the volume 130 at the top of the chamber; in the heat exchanger nucleate boiling will occur because of the low pressure in volume 130. In the embodiment of Figure 5, lines 171, 172 are connected between the chamber 112 and a heat exchanger 170, but the upper line 172 connects with an upper region of the liquid 120 rather than with the reduced pressure volume 130. Figure 6 represents a modification of the Figure 5 embodiment wherein an additional heat exchange arrangement 180 is associated with the heat exchanger 170, the arrangement 180 comprising an inner tube 181 and an outer tube 182 with an annular passage 183 formed therebetween. Both tubes are closed at their upper ends. At its lower end the inner tube 181 is attached to widened flue 184 which is located above and at least partially surrounding the heat exchanger 170. The pressure vessel chamber 111 has a volume for containing a fluid, usually gas (e.g. air, or nitrogen under pressure) and in operation it is heated as it passes over heat exchanger 170 and then passes up the inner tube 181 and down the annular passage 183 to dissipate heat to the surrounding water. One or both tubes 182, 183 may be finned on one or more surfaces to assist heat disposal. Circulation of the air through the tubes may be natural or be forced, e.g. by a fan.

Claims: Power equipment for use underwater, the power equipment comprising: a first chamber (111) containing at least one power device (113) which produces heat in use, and a second chamber (112) at least partially filled with a fluid (120), the second chamber being in heat conductive relationship with the power device and also having a wall (122) in contact with the surrounding water when the power equipment is submerged, whereby heat produced by the power device (113) is transmitted to the second chamber (112) and thence transmitted to the surrounding water, characterised in that : the first and second chambers (111, 112) are both within a pressure vessel (110). Power equipment as claimed in Claim 1, wherein the fluid in the second chamber (112) is a liquid. Power equipment as claimed in Claim 2, wherein the liquid is water. Power equipment as claimed in Claim 2 or Claim 3, wherein the second chamber (112) is connected to a volume compensating means (116) to which liquid may flow from the second chamber or vice versa. Power equipment as claimed in Claim 2 or Claim 3, wherein the second chamber (112) is only partially filled with liquid (120) and a volume (130) is defined in the second chamber above the liquid. Power equipment as claimed in Claim 5, wherein the volume (130) above the liquid is connected (140, 141) to an evacuation means actuatable to reduce the pressure in said volume. Power equipment as claimed in any one of Claims 1 to 4, wherein the second chamber (112) is connected by conduit means (162) with a heat exchange arrangement (160) which is disposed adjacent the power device (113). Power equipment as claimed in Claim 7, wherein the first chamber (111) has a volume containing a further fluid and the heat exchange arrangement (170, 180) comprises a coaxial-tube arrangement (181, 182) for the flow of said further fluid therethrough . Power equipment as claimed in Claim 8, wherein the coaxial-tube arrangement (181, 182) comprises an outer tube (182) extending outwardly from the first chamber (111) and in contact with said surrounding water and an inner tube (181) disposed within the outer tube (182) and terminating at one end within the first chamber (111) near to the power device (113), said further fluid during use of the power equipment being caused to flow first inside the inner tube and then between the outer and inner tubes. Power equipment as claimed in any one of Claims 1 to 9, wherein the second chamber (112) has a domed element (122) whose exterior domed surface provides the wall in contact with the surrounding water for the transfer of heat thereto from the fluid (120) in the second chamber. Power equipment as claimed in Claim 10, wherein the surface of the domed element (122) in contact with the water is formed with corrugations, vanes or ribs. Power equipment as claimed in any of Claims 1-11, wherein movement of the fluid in the power equipment occurs by means of natural circulation and/or by forced circulation.

Inventors: BAYNES GRAHAM TOLHURST, RODWELL CHRISTOPHER, BAYNES, GRAHAM TOLHURST, RODWELL, CHRISTOPHER
Applicants: ALSTOM UK LTD, ALSTOM UK LIMITED
Application year: 1997
Main classification: F28F9
IPC codes: H01F27