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Title:
FUEL TEMPERATURE CONTROL SYSTEM AND METHOD
Document Type and Number:
WIPO Patent Application WO/2024/099525
Kind Code:
A1
Abstract:
Provided is a fuel temperature control system (100) for a fuel system of a marine vessel. The fuel temperature control system (100) comprises a double-wall plate heat exchanger (300). The double-wall plate heat exchanger comprises: a first side (350a) through which fuel in the fuel system is passable; a second side (350b) through which a heat exchange medium is passable; and a plate pair (321, 322, 323) comprising a pair of opposing plates and a region between the opposing plates. The plate pair (321, 322, 323) fluidically separates and thermally couples the first side and the second side, and the region is fluidically isolated from the first side and the second side.

Inventors:
LØTH CHRISTIAN SKOUDAL (DK)
Application Number:
PCT/DK2023/050264
Publication Date:
May 16, 2024
Filing Date:
November 03, 2023
Export Citation:
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Assignee:
A P MOELLER MÆRSK AS (DK)
International Classes:
B63B17/00; B63B35/00; F28D9/00; F28F3/00
Domestic Patent References:
WO2012053958A12012-04-26
Foreign References:
US20130206359A12013-08-15
CN215810366U2022-02-11
US20150369115A12015-12-24
US20130300007A12013-11-14
Download PDF:
Claims:
CLAIMS

1. A fuel temperature control system for a fuel system of a marine vessel, the fuel temperature control system comprising a double-wall plate heat exchanger, the double-wall plate heat exchanger comprising: a first side through which fuel in the fuel system is passable; a second side through which a heat exchange medium is passable; and a plate pair comprising a pair of opposing plates and a region between the opposing plates, wherein the plate pair fluidically separates and thermally couples the first side and the second side, and the region is fluidically isolated from the first side and the second side.

2. The fuel temperature control system of claim 1 , comprising a heat exchange system comprising the second side, the heat exchange system configured to transfer heat between the fuel and one or more systems of the marine vessel.

3. The fuel temperature control system of claim 1 or claim 2, wherein the region comprises a gap between the opposing plates such that, in the event of a loss of integrity of one of the plates, fuel from the first side or heat exchange medium from the second side is flowable into the gap.

4. A fuel system for a marine vessel, the fuel system comprising the fuel temperature control system of any one of claims 1 to 3, and a fuel supply system configured to supply fuel from a fuel tank to an engine of the marine vessel, the fuel supply system comprising the first side.

5. The fuel system of claim 4, wherein the fuel supply system comprises plural fuel flow paths for passing fuel from one or more fuel storage tanks to one or more engines, and wherein the fuel temperature control system comprises plural double-wall plate heat exchangers comprising respective first sides coupled in respective ones of the plural fuel flow paths, and respective second sides through which the heat exchange medium is passable.

6. The fuel system of claim 5, when dependent on claim 2 or any claim dependent thereon, wherein the heat exchange system comprises the second side of each of the plural double-wall plate heat exchangers.

7. A marine vessel comprising the fuel temperature control system of any one of claims 1 to 3, or the fuel system of any one of claims 4 to 6, the marine vessel comprising an engine room comprising an engine of the marine vessel.

8. The marine vessel of claim 7, wherein the double-wall plate heat exchanger is located external to the engine room.

9. A method of controlling a temperature of fuel in a fuel system of a marine vessel, the fuel system comprising a double-wall plate heat exchanger, the double-wall plate heat exchanger comprising: a first side through which fuel in the fuel system is passable; a second side through which a heat exchange medium is passable; and a plate pair comprising a pair of opposing plates and a region between the opposing plates, wherein the plate pair fluidically separates and thermally couples the first side and the second side, and the region is fluidically isolated from the first side and the second side; the method comprising causing fuel to pass through the first side and causing the heat exchange medium to pass through the second side, so as to cause heat to be transferred between the fuel and the heat exchange medium and thereby control the temperature of the fuel.

10. Use of a double-wall plate heat exchanger in a fuel system for an engine of a marine vessel to transfer heat between a fuel in the fuel system and a heat exchange medium in a heat exchange system of the marine vessel; wherein the double-wall plate heat exchanger comprises: a first side through which fuel in the fuel system is passable; a second side through which a heat exchange medium is passable; and a plate pair comprising a pair of opposing plates and a region between the opposing plates, wherein the plate pair fluidically separates and thermally couples the first side and the second side, and the region is fluidically isolated from the first side and the second side.

Description:
FUEL TEMPERATURE CONTROL SYSTEM AND METHOD

TECHNICAL FIELD

[0001] The present invention relates to fuel temperature control systems for fuel systems of marine vessels, methods of controlling a temperature of fuel in a fuel system of a marine vessel, fuel systems for marine vessels and comprising fuel temperature control systems, and marine vessels comprising fuel systems and/or fuel temperature control systems.

BACKGROUND

[0002] Some marine vessels may be configured to transport volatile and/or flammable substances, such as methanol, in tanks. In various examples, marine vessels may even use such substances as fuel, including various biofuels such as methanol fuel.

SUMMARY

[0003] According to a first aspect of the present invention, provided is a fuel temperature control system for a fuel system of a marine vessel, the fuel temperature control system comprising a double-wall plate heat exchanger, the double-wall plate heat exchanger comprising: a first side through which fuel in the fuel system is passable; a second side through which a heat exchange medium is passable; and a plate pair comprising a pair of opposing plates and a region between the opposing plates, wherein the plate pair fluidically separates and thermally couples the first side and the second side, and the region is fluidically isolated from the first side and the second side.

[0004] In this way, in the event of a loss of integrity of one of the opposing plates, the first and second sides remain fluidically isolated by the other one of the opposing plates. This may reduce a risk of contamination of the heat exchange medium by the fuel, and/or contamination of the fuel with the heat exchange medium, in use.

[0005] By using the double-wall plate heat exchanger, a simplicity of the fuel system may be improved compared, for example, to a system in which a separation between fuel and the heat exchange medium is achieved using an auxiliary heat transfer system, such as a glycol system. [0006] Such auxiliary heat transfer systems may require a first heat exchanger for transferring heat between the fuel system and the auxiliary heat transfer system, and a second heat exchanger for transferring heat between the auxiliary heat transfer system and the heat exchange medium. In other words, the double-wall plate heat exchanger may permit a simpler and/or more direct thermal coupling of the fuel system with a heat exchange medium while achieving improved redundancy.

[0007] Optionally, the fuel temperature control system comprises a heat exchange system comprising the second side, the heat exchange system configured to transfer heat between the fuel and one or more systems of the marine vessel.

[0008] That is, the heat exchange system is configured to comprise the heat exchange medium, in use. The heat exchange medium may be cooling water, or other cooling fluid, passed through the heat exchange system, in use. The double-wall plate heat exchanger may prevent fuel from entering the heat exchange system in the event of a loss of integrity in one of the opposing plates. This may reduce a risk of contamination of the heat exchange system, and the heat exchange medium therein, with fuel from the fuel system. Moreover, heat collected by the heat exchange system may be used to warm the fuel, which may reduce wasted heat energy and improve an efficiency of the fuel temperature control system, and/or of a fuel system and/or marine vessel comprising the fuel temperature control system.

[0009] Optionally, the fuel system comprises a fuel supply system configured to supply fuel from a fuel tank to an engine of the marine vessel. Optionally, the heat exchange system comprises a cooling circuit configured to cool components of an engine of a marine vessel, such as an engine to which the fuel supply system is configured to supply fuel, or any other engine. In this way, a temperature of the fuel that is passed to the engine, in use, may be controlled using a cooling circuit of the marine vessel, particularly a cooling circuit associated with the engine of the marine vessel. Alternatively, or in addition, the heat exchange system may be configured to transfer heat between the fuel and other systems of the marine vessel, such as to take heat from the fuel and provide the heat as part of a hotel load of the marine vessel. Use of the double-wall plate heat exchanger may reduce a likelihood of the fuel in the fuel system mixing with the cooling water in the cooling circuit and subsequently being passed to relatively hot engine components. This may, in turn, improve a safety of the fuel system.

[0010] The cooling system may be configured to supply the heat exchange medium to the second side of the heat exchanger to control a temperature of the fuel flowing through the first side of the heat exchanger to a temperature in the range 25C to 50C, such as in the range 30C to 40C, such as in the range 34C to 38C, such as around 35C, 36C or 37C. For instance, the heat exchange medium may be supplied at a temperature in the range 25C to 50C, such as in the range 30C to 40C, such as in the range 34C to 38C, such as around 35C, 36C or 37C.

[0011 ] Optionally, the region comprises a gap between the opposing plates such that, in the event of a loss of integrity of one of the plates, fuel from the first side or heat exchange medium from the second side is flowable into the gap.

[0012] Optionally, the fuel temperature control system comprises a reservoir in fluidic communication with the gap so that, in the event of a loss of integrity of one of the plates, fluid, such as fuel or heat exchange medium, present in the gap is flowable to the reservoir. Providing such a gap and optional reservoir may allow a leak in the double-wall plate heat exchanger to be detected, such as by detecting the presence of fuel in the gap, and/or in a reservoir to which the gap is fluidically connected. This, in turn, may allow remedial action to be taken to prevent further leakage. The fuel system may comprise a detector, such as a level detector or gas sensor, for detecting the presence of fuel in the reservoir. Optionally, the fuel system comprises a hydrocarbon sensor, such as an oil, methanol, and/or alcohol sensor.

[0013] The double-wall plate heat exchanger may comprise the reservoir. The reservoir may comprise a tray or other container. The tray or container may be open to an atmosphere surrounding the reservoir. Alternatively, the reservoir may be isolated from the atmosphere, such as by the reservoir comprising a hermetically sealed vessel.

[0014] According to a second aspect of the present invention, provided is a fuel system for a marine vessel, the fuel system comprising the fuel temperature control system of the first aspect, and a fuel supply system configured to supply fuel from a fuel tank to an engine of the marine vessel, the fuel supply system comprising the first side.

[0015] Optionally, where the fuel temperature control system comprises the heat exchange system, the heat exchange system may comprise a cooling circuit that is configured to cool components of the engine of a marine vessel. In this way, a temperature of the fuel that is passed to the engine, in use, may be controlled using a cooling circuit of the marine vessel, particularly a cooling circuit associated with the engine of the marine vessel. Use of the double-wall plate heat exchanger may reduce a likelihood of the fuel in the fuel system mixing with the heat exchange medium in the cooling circuit and subsequently being passed to relatively hot engine components.

This may, in turn, improve a safety of the fuel system.

[0016] Optionally, the fuel system is a methanol fuel system configured to supply fuel from a methanol fuel tank to the engine of the marine vessel. It will be understood that the fuel supply system may comprise various pumps, filters, valves, bypasses, tanks and/or other fuel control and/or fuel conditioning components, as appropriate.

[0017] Optionally, the fuel supply system comprises plural fuel flow paths for passing fuel from one or more fuel storage tanks to one or more engines, and wherein the fuel temperature control system comprises plural double-wall plate heat exchangers comprising respective first sides coupled in respective ones of the plural fuel flow paths, and respective second sides through which the heat exchange medium is passable.

[0018] In this way, the same heat exchange medium may be used to cool and/or heat fuel in plural fuel flow paths. This may allow a temperature of the fuel stored in the fuel storage tank(s), which may not be heat-controlled, to be controlled to a set temperature by a single heat exchange medium, such as cooling water from the cooling circuit of the engine of the marine vessel, where provided. By using a double-wall plate heat exchanger in each fuel flow path, a simplicity of the fuel system may be improved. Moreover, a physical separation of each fuel flow path from other systems of the marine vessel may be improved, thereby improving a safety of the fuel system.

[0019] Optionally, the heat exchange system, where provided, comprises the second side of each of the plural double-wall plate heat exchangers.

[0020] That is, the fuel in each of the fuel flow paths may be cooled and/or heated by the same heat exchange system of the marine vessel. This may improve a simplicity of the fuel system. The heat exchange system may comprise the cooling circuit configured to cool components associated with one or more of the engines of the marine vessel, as discussed above. Such a cooling circuit may be configured to circulate heat exchange medium at a temperature in the range of 25C to 50C, such as in the range 30C to 40C, such as in the range 34C to 38C, such as around 35C, 36C or 37C. This may be particularly beneficial when the fuel is methanol fuel, which may have improved properties when passed to the, or each, engine at a particular temperature, such as at a temperature in the range 25C to 50C, such as in the range 30C to 40C, such as in the range 34C to 38C, such as around 35C, 36C or 37C. It will be appreciated that any other suitable heat exchange system, such as a heat exchange system for transferring heat between the fuel and other systems of the marine vessel, such as to provide heat as part of a hotel load of the marine vessel, may operate under similar parameters.

[0021] It will be appreciated that the fuel system may comprise and/or benefit from any of the optional features and/or advantages ascribed to the first aspect of the present invention.

[0022] A third aspect of the present invention provides a marine vessel comprising the fuel temperature control system of the first aspect, or the fuel system of the second aspect, the marine vessel comprising an engine room comprising an engine of the marine vessel.

[0023] Where provided, the heat exchange system, or at least a part thereof, may be located in the engine room. This may particularly be the case when the heat exchange system comprises a cooling circuit for cooling the engine. In this way, the double-wall plate heat exchanger reduces a risk of fuel, such as methanol fuel, mixing with the heat exchange medium and being passed into the engine room. This may, in turn, reduce a likelihood of methanol fuel being exposed to heat in or around components of the engine, or other heat sources in the engine room, thereby improving a safety of the fuel system and/or the marine vessel.

[0024] Optionally, the double-wall plate heat exchanger is located external to the engine room.

[0025] The double-wall plate heat exchanger may, for instance, be in a fuel preparation room comprising one or more storage tanks for the fuel. By locating the double-wall plate heat exchanger external to the engine room, a leak of fuel, such as methanol fuel, from the doublewall plate heat exchanger may be isolated from heat sources associated with the engine or other components in the engine room. This may improve a safety of the fuel system and/or the marine vessel.

[0026] It will be appreciated that the marine vessel may comprise and/or benefit from any of the optional features and/or advantages ascribed to the first and/or second aspects of the present invention.

[0027] A fourth aspect of the present invention provides a method of controlling a temperature of fuel in a fuel system of a marine vessel, the fuel system comprising a double-wall plate heat exchanger, the double-wall plate heat exchanger comprising: a first side through which fuel in the fuel system is passable; a second side through which a heat exchange medium is passable; and a plate pair comprising a pair of opposing plates and a region between the opposing plates, wherein the plate pair fluidically separates and thermally couples the first side and the second side, and the region is fluidically isolated from the first side and the second side; the method comprising causing fuel to pass through the first side and causing the heat exchange medium to pass through the second side, so as to cause heat to be transferred between the fuel and the heat exchange medium and thereby control the temperature of the fuel.

[0028] Optionally, the fuel system is a methanol fuel system configured to supply methanol fuel to an engine of the marine vessel. Methanol fuel may provide various benefits over other fuels, such as heavy fuel oil, for engines of marine vessels. For instance, methanol may be more environmentally sustainable, may be more efficient, and may emit less particulate matter than heavy fuel oil. Methanol may, however, be more volatile than heavy fuel oil. By using the doublewall plate heat exchanger, a mixing of the flammable methanol fuel with the heat exchange medium may be reduced, which may in turn improve a safety of the fuel system.

[0029] It will be appreciated that the method may comprise and/or benefit from any of the optional features and/or advantages ascribed to any of the first to third aspects of the present invention.

[0030] A fifth aspect of the present invention provides a use of a double-wall plate heat exchanger in a fuel system for an engine of a marine vessel to transfer heat between a fuel in the fuel system and a heat exchange medium in a heat exchange system of the marine vessel; wherein the double-wall plate heat exchanger comprises: a first side through which fuel in the fuel system is passable; a second side through which a heat exchange medium is passable; and a plate pair comprising a pair of opposing plates and a region between the opposing plates, wherein the plate pair fluidically separates and thermally couples the first side and the second side, and the region is fluidically isolated from the first side and the second side.

[0031] It will be appreciated that the fifth aspect may comprise and/or benefit from any of the optional features and/or advantages ascribed to any of the first to fourth aspects of the present invention.

BRIEF DESCRIPTION OF DRAWINGS

[0032] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0033] Figure 1 shows a schematic diagram of an example marine vessel; [0034] Figure 2 shows a schematic diagram of an example fuel system of the marine vessel shown in Figure 1 , the fuel system comprising a fuel temperature control system;

[0035] Figures 3A and 3B show schematic diagrams of an example heat exchanger of the fuel temperature control system shown in Figure 2; and

[0036] Figure 4 shows an example method of controlling a temperature of fuel in the fuel system shown in Figures 1 and 2.

DETAILED DESCRIPTION

[0037] Figure 1 shows an example marine vessel 1 , which is a container vessel that transports containers 20 containing cargo. The marine vessel comprises an engine room 40 comprising three engines 30a, 30b, 30c (collectively referred to herein using the reference numeral 30) that provide energy to systems of the marine vessel 1 . The marine vessel 1 also comprises a fuel system 10 that supplies fuel, specifically methanol fuel, to the engines 30.

[0038] The fuel system 10 comprises a fuel temperature control system 100 that controls a temperature of the fuel supplied to the engines 30 by the fuel system 10. The fuel temperature control system 100 causes the methanol in the fuel system 10 to be supplied to the engines 30 at a temperature of between 25 C and 50 C. Maintaining the temperature of the methanol fuel in this range reduces a level of condensation, and therefore corrosion, on components of the engines 30 that are in contact with relatively low-temperature methanol fuel, in use. A risk of cavitation of the methanol fuel as it passes through the fuel system 10 and/or the engines 30, which can occur at relatively high temperatures, is also reduced.

[0039] The marine vessel 1 also comprises a cooling system 50, which here is a part of the fuel temperature control system 100, and which passes cooling water to various systems of the marine vessel 1 , including the engines 30. In particular, the cooling system 50 passes cooling water to components of the engines 30 to cool the components of the engines 30. The fuel temperature control system 100 utilises the cooling water in the cooling system 50 to control the temperature of the fuel supplied to the engines 30 by the fuel system 10, as will be described in more detail below. The cooling water is fresh water, which is maintained at a temperature of at (or close to) 36 C by passing the cooling water through a heat exchanger arrangement (not shown) of the cooling system 50. The heat exchanger arrangement comprises a heat exchanger that exchanges heat between the cooling water and seawater, and a temperature regulation valve which is operable to selectively pass the cooling water through the heat exchanger to achieve a desired cooling water temperature.

[0040] Turning now to Figure 2, the fuel system 10 and fuel temperature control system 100 are shown and described in more detail. The fuel system 10 comprises a fuel tank 11 which stores methanol fuel, and a fuel supply system 200 that delivers the methanol fuel from the fuel tank 11 to the three engines 30 of the marine vessel 1 . The engines 30 include a primary engine 30a and first and second auxiliary engines 30b, 30c. The primary engine 30a generates and supplies power to a propulsion system of the marine vessel 1. The auxiliary engines 30b, 30c (and optionally also the primary engine 30a) generate and supply power and/or heat to other systems of the marine vessel 1 , including a hotel load, a cargo load, machinery, the fuel system 10, and the fuel temperature control system 100.

[0041] The fuel supply system 200 comprises a primary fuel flow path 201 along which fuel flows, in use, from the fuel tank 11 to the primary engine 30a, and an auxiliary fuel flow path 202, along which fuel flows, in use, from the fuel tank 1 1 to the first and second auxiliary engines 30b, 30c. The fuel supply system 200 comprises a deaeration tank 250 in the primary fuel flow path 201 , a first primary pump 210 that pumps the fuel along the primary fuel flow path 201 from the fuel tank 11 to the deaeration tank 250, and a second primary pump 220 that pumps the fuel along the primary fuel flow path 201 from the deaeration tank 250 to the primary engine 30a. The deaeration tank 250 removes oxygen and other dissolved gases from the methanol before it is passed to the primary engine 30a. The fuel supply system 200 also comprises an auxiliary pump 230 that pumps the fuel along the auxiliary fuel flow path 202 from the fuel tank 1 1 to the first and second auxiliary engines 30b, 30c. There is no deaeration tank provided in the auxiliary fuel flow path, although one could be provided in alternative examples. The primary and auxiliary flow paths 201 , 202 are selectively isolated from the fuel tank by respective primary and auxiliary tank isolator valves 201 a, 202a. The first and second primary pumps 210, 220, and the auxiliary pump 230, are centrifugal pumps.

[0042] The fuel temperature control system 100 comprises a first primary heat exchanger 300a, a second primary heat exchanger 300b, and an auxiliary heat exchanger 300c. The fuel temperature control system 100 also comprises a primary cooling water circuit 101 and an auxiliary cooling water circuit 102. The primary cooling water circuit 101 circulates cooling water from the cooling system 50 through each of the first and second primary heat exchangers 300a, 300b and back to the cooling system 50. The auxiliary cooling water circuit 102 is fluidically connected in a parallel fluid arrangement with the primary cooling water circuit 101 , and circulates cooling water from the cooling system 50 through the auxiliary heat exchanger 300c and back to the cooling system 50. A cooling water pump 105, which is a conventional (centrifugal) hydraulic pump, pumps the cooling water from the cooling water circuit 50 through each of the primary and auxiliary cooling water circuits 101 , 102.

[0043] The first primary heat exchanger 300a comprises a first primary fuel side 301 a fluidically coupled between first primary pump 210 and the deaerating tank 250, and a first primary cooling water side 302a fluidically coupled in the primary cooling water circuit 101 . The first primary heat exchanger 300a exchanges heat between fuel in the first primary fuel side 301 a and cooling water in the first primary cooling water side 302a, in use. In this way, the first primary heat exchanger 300a controls a temperature of the fuel passed from the fuel tank 1 1 to the deaerating tank 250 in the primary fuel flow path 201 .

[0044] The second primary heat exchanger 300b comprises a second primary fuel side 301 b fluidically coupled between the deaerating tank 250 and the primary engine 30a, and a second primary cooling water side 302b fluidically coupled in the primary cooling water circuit 101 , downstream of the cooling system 50 and upstream of the first primary cooling water side 302a of the first primary heat exchanger 300a. The second primary heat exchanger 300b exchanges heat between fuel in the second primary fuel side 301 b and cooling water in the second primary cooling water side 302b, in use. In this way, the second primary heat exchanger 300b controls a temperature of fuel passed from the deaerating tank 250 to the primary engine 30a in the primary fuel flow path 201.

[0045] The auxiliary heat exchanger 300c comprises an auxiliary fuel side 301 c fluidically coupled between the auxiliary pump 230 and the first and second auxiliary engines 30b, 30c, and an auxiliary cooling water side 302c fluidically coupled in the auxiliary cooling water circuit 102. The auxiliary heat exchanger 300c exchanges heat between fuel in the auxiliary fuel side 301c and cooling water in the auxiliary cooling water side 302c, in use. In this way, the auxiliary heat exchanger 300c controls a temperature of fuel passed from the auxiliary pump 230 to the first and second auxiliary engines 30b, 30c.

[0046] The first and second primary pumps 210, 220 and the auxiliary pump 230 are fixed-speed pumps, which pump fuel through the fuel supply system 200 at a constant flow rate. The fuel supply system 200 comprises a first primary bypass 211 fluidically connecting a point downstream of the first primary fuel side 301 a of the first primary heat exchanger 300a and a point upstream of the first primary pump 210. The first primary bypass 211 comprises a first primary bypass valve 212, which is a pressure regulating valve that is operable to control a flow of fuel through the first primary bypass 211. In this way, a pressure of fuel provided to the deaerating tank 250 can be controlled, at least in part by operating the first primary bypass valve 212 to divert some, or all, of the fuel pumped by the first primary pump 210 through the first primary bypass 211 and back through the first primary pump 210 and the first primary heat exchanger 300a. The first primary bypass valve 211 controls the pressure of the fuel passed to the deaerating tank 250 based on a fuel consumption by the primary engine 30a and characteristics of the first and/or the second primary pump 210, 220. Operating the first primary bypass valve 21 1 also causes at least some the fuel pumped by the first primary pump 210 to be passed through the first primary heat exchanger 300a multiple times, which can advantageously increase an amount of heat exchanged between the fuel in the primary fuel flow path 201 and the cooling water in the primary cooling water circuit 101.

[0047] In a similar way, the fuel supply system 200 comprises a second primary bypass 221 fluidically connecting a point downstream of the second primary fuel side 301 b of the second primary heat exchanger 300b to a point upstream of the second primary pump 220, and specifically to the deaerating tank 250. The second primary bypass 221 comprises a second primary bypass valve 222, which is a pressure regulating valve that is operable to control a flow of fuel through the second primary bypass 221. In this way, a pressure of fuel provided to the primary engine 30a from the deaerating tank 250 can be controlled at least in part by operating the second primary bypass valve 222 to divert some, or all, of the fuel pumped by the second primary pump 220 through the second primary bypass 221 and back through the deaerating tank 250, the second primary pump 220 and the second primary heat exchanger 300b. The second primary bypass valve 221 controls the pressure of the fuel passed to the primary engine 30a from the deaerating tank 250 based on a fuel consumption by the primary engine 30a and characteristics of the first and/or second primary pump 210, 220. Operating the second primary bypass valve 221 also causes at least some of the fuel from the deaeration tank 250 to be passed through the second primary heat exchanger 300b multiple times. This may result in a gradual increase or decrease in a temperature of fuel present in the deaerating tank 250, in use. In particular, the temperature of the fuel in the deaerating tank 250 increases if the methanol fuel in the deaerating tank 250 is at a lower temperature than the cooling water in the primary cooling water circuit 101 . The temperature of the fuel in the deaerating tank 250 instead decreases if the fuel in the deaerating tank 250 is at a higher temperature than the cooling water in the cooling water circuit 101 . [0048] The fuel supply system 200 also comprises an auxiliary bypass 231 fluidically connecting a point downstream of the auxiliary fuel side 301 c of the auxiliary heat exchanger 300c to a point upstream of the auxiliary pump 230. The auxiliary bypass 231 comprises an auxiliary bypass valve 232, which is a pressure regulating valve that is operable to control a flow of fuel through the auxiliary bypass 231 . In this way, a pressure of fuel provided to the auxiliary engines 30b, 30c from the auxiliary pump 230 can be controlled at least in part by operating the auxiliary bypass valve 232 to divert some, or all, of the fuel pumped by the auxiliary pump 230 through the auxiliary bypass 231 and back through the auxiliary pump 230 and the auxiliary heat exchanger 300c multiple times. The auxiliary bypass valve 231 controls the pressure of the fuel passed to the first and second auxiliary engines 30b, 30c based on a fuel consumption by the first and/or second auxiliary engine 30b, 30c and characteristics of the auxiliary pump 230. Operating the auxiliary bypass 231 can advantageously increase an amount of heat exchanged between the fuel in the auxiliary fuel flow path 202 and the cooling water in the auxiliary cooling water circuit 102.

[0049] The fuel system 10 also comprises a primary engine valve 240a, which is a variable flow control valvethat is operable to control a flow rate of fuel to the primary engine 30a from the fuel supply system 200, and specifically from the primary fuel flow path 201 . The fuel system 10 also comprises first and a second auxiliary engine valves 240b, 240c, which are respective variable flow control valves that are operable to control a flow rate of fuel to the respective first and second auxiliary engines 30b, 30c from the fuel supply system 200, and specifically from the auxiliary fuel flow path 202. It will be appreciated that the primary engine valve 240a can be closed and the second primary bypass valve 222 can be opened when the second primary pump 220 is operated. This will cause fuel from the deaeration tank 250 to pass through the first primary heat exchanger 300b and back to the deaeration tank 250, but not to the primary engine 30a. This would cause a temperature of the fuel in the deaeration tank 250 to gradually change, which could be beneficial if the fuel system 10 and/or primary engine 30a have been idle for a period of time, such as when the marine vessel 1 is docked. In particular, the temperature of the fuel in the deaerating tank 250 increases if the methanol fuel in the deaerating tank 250 is at a lower temperature than the cooling water in the primary cooling water circuit 101 . The temperature of the fuel in the deaerating tank 250 instead decreases if the fuel in the deaerating tank 250 is at a higher temperature than the cooling water in the cooling water circuit 101

[0050] It will be appreciated from the foregoing discussion that the cooling system 50 is used to cool components of the engines 30 located in the engine room 40, and also to control a temperature of the fuel that is passed to the engines 30 via the fuel system 10. Methanol is low flashpoint fuel that is flammable at ambient conditions typically present on the marine vessel 1 . The first and second primary heat exchangers 300a, 300b and the auxiliary heat exchanger 300c are double-wall plate heat exchangers, which provide an additional barrier to further separate the fuel in the fuel supply system 200 and cooling water in the cooling system 100. This can avoid, or reduce a risk of, leaked methanol fuel from the fuel system 10 entering the cooling system 50 and being passed towards the engines 30 and/or the engine room 40, thereby keeping the leaked methanol fuel away from any ignition sources and improving a safety of the fuel system 10. Moreover, the first and second primary heat exchangers 300a, 300b and the auxiliary heat exchanger 300c are each located external to the engine room 40, specifically in a fuel preparation room comprising the various pumps, tanks and valves of the fuel supply system 200 described above. This further reduces a risk of leaked methanol from the fuel supply system 200, such as from any of the pumps, tanks, valves, and/or heat exchangers described above, from entering the engine room 40.

[0051] An example schematic construction of such a double-wall plate heat exchanger, here referred to with the common reference numeral 300, is shown in Figures 3A and 3B. The doublewall plate heat exchanger 300 comprises first, second, third and fourth fluid channels 310a, 310b, 310c, 31 Od. The first and third fluid channels 310a, 310c pass fluid from a first inlet (not shown) of the double-wall plate heat exchanger 300 to a first outlet (not shown) of the double-wall plate heat exchanger 300. The second and fourth fluid channels 310b, 31 Od pass fluid from a second inlet (not shown) of the double-wall plate heat exchanger to a second outlet (not shown) of the double-wall plate heat exchanger 300, in a direction opposite to the fluid flowing through the first and third fluid channels 310a, 310c. The double-wall plate heat exchanger 300 comprises a first side 350a comprising the first and third fluid channels 310a, 310c, and a second side 350b comprising the second and fourth fluid channels 310b, 31 Od. It will be appreciated that the first side 350a corresponds to the respective first and second primary fuel sides 301 a, 301 b of the first primary heat exchanger 300a and the auxiliary fuel side 301 c of the auxiliary heat exchanger 300c. Similarly, the second side 350b corresponds to the respective first and second primary cooling water sides 302a, 302b of the first primary heat exchanger 300a and the auxiliary cooling water side 302c of the auxiliary heat exchanger 300c.

[0052] The double-wall plate heat exchanger 300 comprises a first end plate 320a forming an outer wall of the first channel 310a and a second end plate 320b forming an outer wall of the fourth channel 31 Od. The double-wall plate heat exchanger 300 also comprises a first plate pair 321 fluidically separating and thermally coupling the first channel 310a and the second channel 310b, a second plate pair 322 fluidically separating and thermally coupling the second channel 310b and the third channel 310c, and a third plate pair 323 fluidically separating and thermally coupling the third channel 310c and the fourth channel 31 Od. The first plate pair 321 comprises a first left plate 321 a, an opposing first right plate 321 b, and a first gap 331 between the first left plate 321 a and the first right plate 321 b. Similarly, the second plate pair 322 comprises a second left plate 322a, an opposing second right plate 322b, and a second gap 332 between the second left plate 332a and the second right plate 332b. The third plate pair 323 comprises a third left plate 323a, an opposing third right plate 323b, and a third gap 333 between the third left plate 323a and the third right plate 323b. The first, second and third gaps 331 , 332, 333 are each fluidically isolated from the first side 350a and the second side 350b. The double-wall plate heat exchanger 300 also comprises a drip tray 340, which is open to an atmosphere surrounding the drip tray 340. The drip tray 340 is in fluidic communication with each of the first, second and third gaps 331 , 332, 333, specifically by being located beneath the first, second and third gaps 331 , 332, 333. In this way, any fluid present in any of the first, second and third gaps 331 , 332, 333 can fall into the drip tray 340 under the action of gravity.

[0053] An example of a loss of integrity of the double-wall plate heat exchanger 300 is shown in Figure 3B. Specifically, the double-wall plate heat exchanger 300 comprises a rupture 370 in the second left plate 322a. In this case, the fluid flowing in the second channel 310b passes through the rupture 370, into and through the second gap 332, and drips from the second gap 332 into the drip tray 340. Since the second gap 332 is fluidically isolated from the third channel 310c (by the second right plate 322b), there is no mixing of methanol fuel flowing in the first side 350a (specifically in the second fluid channel 31 Ob), with cooling water flowing in the second side 350b (specifically in the third fluid channel 310c). By allowing the fuel to pass through the second gap 332 and into the drip tray 340, a presence of methanol fuel in the drip tray 340, and therefore a leak in the double-wall plate heat exchanger 300, can be detected. This may allow remedial action to be taken, such as to replace the double-wall plate heat exchanger 300. Specifically, the doublewall plate heat exchanger 300 of the present example comprises a gas sensor 360 located in proximity to the drip tray 340. The gas sensor 360 can sense the presence of methanol in the drip tray 340, as the methanol is volatile and will evaporate at ambient conditions in an atmosphere surrounding the drip tray 340.

[0054] It will be appreciated that Figures 3A and 3B are illustrative only, and that any number of fluid channels 31 Oa, 310b, 31 Oc, 31 Od and/or plate pairs 321 , 322, 323 may be provided in other examples. In alternative examples, the drip tray 340 may be any other suitable reservoir. Moreover, the gas sensor 360 may alternatively, or in addition, comprise a level sensor, or any other suitable sensor, which detects the presence of liquid methanol and/or cooling water in the drip tray 340. For instance, the gas sensor 360 may instead, or in addition, comprise a hydrocarbon sensor, such as an oil, methanol, and/or alcohol sensor. In other examples, there is no gap between the opposing plates in the first, second and third plate pairs 321 , 322, 323. That is, the opposing plates of respective plate pairs may contact each other. In this way, the doublewall separation between the first and second sides 350a, 350b of the double-wall plate heat exchanger 300 may be achieved, but in such a case methanol fuel (and/or cooling fluid) may not be able to leak out of the double-wall plate heat exchanger 300 in the event of a loss of integrity of one of the plates 321 a, 321 b, 322a, 322b, 323a, 323b. Nevertheless, in such an example, contamination of the cooling water in the second side 350b with methanol fuel in the first side 350a can still be avoided.

[0055] Turning now to Figure 4, shown is a method 400 of controlling a temperature of fuel in the fuel system 10 of the marine vessel 1. The method 400 comprises causing 410 fuel to pass through any one or more of the first primary fuel side 301 a of the first primary heat exchanger 300a, the second primary fuel side 301 b of the second primary heat exchanger 300b, and the auxiliary fuel side 301 c of the auxiliary heat exchanger 300c. This is by the method 400 comprising causing 415 operation of the respective first primary pump 210, second primary pump 220 and/or auxiliary pump 230. The method also comprises causing 420 cooling water to pass through the respective cooling water side 302a, 302b, 302c of the heat exchanger(s) through which the fuel is caused to pass. This is by the method 400 comprising causing 425 operation of the cooling water pump 105.

[0056] Example embodiments of the present invention have been discussed, with particular reference to the examples illustrated; however, it will be appreciated that variations and modifications may be made without departing from the scope of the invention as defined by the appended claims.

[0057] For instance, while the marine vessel 1 is described as a container vessel for transporting containers 20 containing cargo, in other examples the marine vessel 1 may be any other suitable marine vessel, such as a chemical tanker or a tugboat. Moreover, while the fuel system 10 comprises two fuel pumps 210, 220 and heat exchangers 300a, 300b in the primary fuel flow path 201 , and only one fuel pump 230 and one heat exchanger 300c in the auxiliary fuel flow path 202, there may instead be any other number of pumps and/or heat exchangers in either of the primary and auxiliary fuel flow paths 201 , 202. Similarly, there may be any number of fuel flow paths 201 , 202, engines 30, and/or cooling circuits 101 , 102 in other examples. For instance, the fuel system 10 may comprise a single cooling circuit 101 that passes fuel from the cooling system 50 to each of the first and second primary heat exchangers 300a, 300b and the auxiliary heat exchanger 300c (and/or any other heat exchanger) in a series fluid arrangement. Alternatively, each heat exchanger of the fuel system 10 may be located in a respective parallel circuit.

[0058] While the cooling system 50 is described as being a part of the fuel temperature control system 100, in other examples the cooling system 50 is separate to the fuel temperature control system 100, but provides cooling water to the fuel temperature control system 50. The cooling water may be passed around the first and second cooling water circuits 101 , 102 in any suitable direction, such as by changing a direction and/or location of the cooling water pump 105. In various examples, a fluid other than water can be received from the cooling system 50 and passed through the primary and secondary cooling water circuits 101 , 102. Such a fluid may be glycol, or seawater. In some examples, the deaeration tank 250 may be omitted, and/or a deaeration tank may be provided in the auxiliary fuel flow path 202.

[0059] Furthermore, the fuel system 10 may comprise other components not shown in the Figures, such as filters for filtering the fuel and/or sensors, such as pressure sensors, temperature sensors, composition sensors, and/or fuel flow sensors. It will also be appreciated that the various valves in the fuel system 10 may be omitted or replaced by any other suitable valves or flow control arrangements as applicable. For instance, any of the first and second primary bypass valves 212, 222 and the auxiliary bypass valve 232 may be replaced by three-way flow control valves for diverting flow through the respective bypasses 21 1 , 221 , 231. The first and second primary pumps 210, 220 and the auxiliary pump 230 are centrifugal pumps, but in other examples may be any other suitable type of pump.

[0060] It will be appreciated that variations in the number and/or presence of the above-described components of the fuel system 10 may be dependent on the type and/or quantity of engines 30 to which the fuel system 10 is to supply fuel. Other alternatives and modifications within the scope of the appended claims will be appreciated by the skilled person.