Cooling system for a water-borne vessel

Abstract

A cooling system for a water-borne vessel (1) is disclosed. The system comprises a strut (5) for supporting a propeller shaft (4) of the vessel, the strut (5) comprising a fluid inlet (8), a fluid outlet (9), and a channel (10) inside the strut (5) for transporting fluid between the fluid inlet and fluid outlet, one or more fluid conduits coupling the fluid inlet and outlet to a component to be cooled, and a pump for circulating a fluid through the conduits and said channel.

Claims

1. A cooling system for a water-borne vessel comprising a propeller shaft extending from a bow end at which the propeller shaft is driven by an inboard electric motor to a stern end at which a propeller is fixed to the propeller shaft, the cooling system comprising: a strut in a form of a thermally conducting structure attached to a bottom of a vessel's hull and at the stern end, for supporting the propeller shaft of the vessel, the strut comprising a fluid inlet, a fluid outlet, and a channel or channels within the strut for transporting a fluid between the fluid inlet and fluid outlet, the strut being a cast or machined out of a thermally conductive material, wherein an interior surface of the strut forms the channel or channels, and heat of the fluid in the channel or the channels is dissipated to surrounding water through the thermally conductive material filled between the interior surface of the strut and an exterior surface of the strut; one or more fluid conduits located inside the vessel's hull for coupling the fluid inlet and fluid outlet to the inboard electric motor and/or batteries thereof to be cooled; and a pump for circulating the fluid through the fluid conduits and the channel or channels, wherein cooling of the fluid of the cooling system is provided substantially when the fluid flows through the strut.

2. The cooling system according to claim 1, wherein the strut comprises a bearing for supporting the propeller shaft and for facilitating rotation of the propeller shaft within the strut.

3. The cooling system according to claim 1, wherein the strut is formed substantially of a metal.

4. The cooling system according to claim 3, wherein the metal comprises steel or brass.

5. The vessel comprising the cooling system according to claim 1.

6. The cooling system according to claim 1, wherein the channel or channels have a convoluted shape.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a side view of a stern portion of a water-borne vessel;

(2) FIG. 2 is a perspective view of a heat exchanger according to an embodiment of the invention;

(3) FIG. 3 is a cut-away view of the heat exchanger of FIG. 2; and

(4) FIG. 4 illustrates a cooling system according to an embodiment of the invention.

DETAILED DESCRIPTION

(5) The marine industry is increasingly interested in the use of electric motors to propel vessels. This is due to a number of factors including environmental, performance, and efficiency. One advantage of electric motors is the reduced amount of heat that they produce, meaning that cooling systems can be simplified. In particular only a relatively small heat exchanger may be required. One might consider providing a dedicated component beneath a boat's hull and which has a surface area exposed to the sea water. However, whilst such a component may provide efficient cooling, it adds an extra cost and may also add to the hull's drag factor.

(6) FIG. 1 is a side view of a water-borne vessel 1. The vessel 1 comprises a hull 2, propeller 3. propeller shaft 4. propeller shaft strut 5. and rudder 6. When the vessel is in water, the propeller 3. propeller shaft 4. propeller shaft strut 5 and rudder 6 are below the water line. The propeller shaft 4 is driven to rotate by a motor inside the vessel, and in particular by an inboard electric motor (not shown in the Figure). Rotation of the propeller shaft 4 results in rotation of the propeller 3, and hence propulsion of the vessel 1 through the water. The propeller shaft strut 5 supports the propeller shaft 4 within a bearing such that the shaft is allowed to rotate within the strut 5 but is prevented from flexing and vibrating (to any significant extent) and the propeller 3 prevented from coming into contact with the hull 2.

(7) FIG. 2 is a perspective view a propeller shaft strut 5 according to an embodiment of the invention whilst FIG. 3 is a cut-away view of the same propeller shaft strut 5. In this embodiment the propeller shaft strut 5 is configured to operate also as a heat exchanger 7. The strut 5 comprises a cooling fluid inlet 8. a cooling fluid outlet 9. a cooling channel 10 and a propeller shaft channel 11 into which a bearing is integrated (not shown). The cooling channel 10 allows fluid entering through the cooling fluid inlet 8 to circulate within the propeller shaft strut 5 and out through the cooling fluid outlet 9. The fluid may be water or another suitable liquid. The channel 10 is isolated from the outer surface of the strut 5, to prevent mixing of cooling fluid inside the strut and water outside the strut.

(8) The propeller shaft strut 5 is a highly thermally conducting structure which in use is located below the waterline. For example, the propeller shaft strut 5 may be cast or machined out of bronze or stainless steel. The propeller shaft strut 5 is preferably located in front of the propeller 3 in the direction of motion of the water vessel 1. The temperature of the propeller shaft strut 5 is thus very close to the temperature of the water surrounding the propeller shaft strut 5.

(9) Whilst FIG. 3 illustrates a simple generally U-shaped cooling channel 10, the channel may have a more convoluted shape, such as a zig-zag shape, so as to increase the cooling surface area of the channel that is exposed to coolant. The cooling channel 10 is preferably near the outer surface of the propeller shaft strut 5 so as to enable efficient heat exchange between the cooling fluid and the surrounding water.

(10) Whilst the propeller shaft strut 5 is a relatively small component, and therefore is able to provide only limited cooling capacity, it has been found that this is sufficient for certain efficient electric motors. Moreover, the modified propeller shaft strut 5 can be easily retro-fitted to existing vessels, for by example replacing an existing propeller shaft strut with a modified propeller shaft strut. Furthermore, because the propeller shaft strut 5 is a direct replacement of an existing propeller shaft strut on a vessel, the handling characteristics of the vessel, such as maneuverability and top speed, are not adversely affected to any significant extent.

(11) FIG. 4 illustrates schematically a cooling system 12 incorporating the propeller shaft strut 5 described above. The cooling system comprises the modified propeller shaft strut 5. coolant pump 13 and coolant tubes or pipes 14. The cooling system 12 cools an electric motor 1 5 that heats up in use and requires cooling. The cooling system 12 is shown coupled directly to the electric motor 15 but indirect coupling is also possible. For example, the electric motor may have an internal cooling system with its own heat exchanger in which case the cooling system 12 provides a means for cooling the internal heat exchanger.

(12) In use. the coolant pump 13 circulates cooling fluid around the cooling system 12. Lower temperature cooling fluid flows from the heat exchanger 7, through the coolant pump 13 and to the device 15. The cooling fluid absorbs heat emitted by the device 15 and the higher temperature cooling fluid flows to the heat exchanger 7. The heat exchanger 7 conducts heat away from the cooling fluid, thus reducing the temperature of the cooling fluid before the cooling fluid is fed back towards the device.

(13) In the embodiment shown in FIG. 4, the cooling system is used to cool an electric motor. However the invention may be used to cool any device that requires moderate cooling in operation. For example, batteries and air conditioning components may be cooled by the cooling system.

(14) It will be appreciated by persons skilled in the art that various modifications may be made to the above embodiments without departing from the scope of the present invention.