Subcooling system

Abstract

A subcooling system for subcooling fuel of a ship transporting liquefied gas, according to the present invention, comprises: a fuel tank storing fuel to be supplied to an engine; a cargo tank storing liquefied gas; a subcooling unit subcooling the liquefied gas; a fuel supply line connected from the fuel tank to the engine and supplying fuel to the engine; a fuel return line branched from the fuel supply line and connected to the fuel tank; and a fuel subcooling heat exchanger disposed on the fuel return line and exchanging heat between the fuel and liquefied gas subcooled by the subcooling unit, wherein the fuel in the fuel subcooling heat exchanger may be subcooled by the subcooled liquefied gas.

Description

Supercooling system

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0132955 filed on September 30, 2024, and all contents disclosed in the document of said Korean Patent Application are incorporated herein as part of this specification.

[0003] Technology field

[0004] The present invention relates to a supercooling system.

[0005] Since liquefying gas reduces its volume, it is stored or transported in a liquefied state to increase storage and transportation efficiency. Gas in this liquefied state is called liquefied gas. The term liquefied gas can be used to encompass all gaseous fuels generally stored in a liquid state, such as liquefied natural gas, liquefied ethane, liquefied ethylene, liquefied petroleum gas, liquefied propane, liquefied butane, liquefied hydrogen, liquefied nitrogen, and ammonia.

[0006] Although storage tanks with excellent insulation performance are used to maintain cryogenic temperatures for liquefied gas, it is impossible to completely block the inflow of heat from the outside, causing the liquefied gas inside the tank to vaporize and generate Boil-Off Gas (BOG). When BOG occurs, the pressure inside the storage tank increases, creating a risk of explosion, and economic losses result because the transportable volume decreases proportionally to the amount of gas that vaporizes.

[0007] As a solution to the problems caused by BOG, there is a method of supercooling the liquefied gas. This cooling system utilizes a cooling cycle that cools the liquefied gas through the circulation of a refrigerant.

[0008] Meanwhile, generally, various engines installed on ships generate power by burning fossil fuels, and the exhaust gases produced during the combustion process contain nitrogen oxides, sulfur oxides, carbon dioxide, and the like. As air pollution caused by pollutants in exhaust gases increases, there is a growing demand for the development of eco-friendly ships that generate power using carbon-free fuels. Accordingly, ships propelled by carbon-free fuels and capable of transporting gases different from carbon-free fuels, such as the aforementioned natural gas, are emerging.

[0009] Since carbon-free fuel must also be stored at low temperatures, a cooling system for carbon-free fuel is essential. However, since a separate cooling system for carbon-free fuel must be provided separately from the transported liquefied gas, there is a need to simplify the cooling systems for carbon-free fuel and liquefied gas.

[0010] Meanwhile, since cryogenic fluid flows through the piping of a supercooling system, the temperature can drop excessively during the heat exchange process, causing freezing and resulting in a phenomenon called clogging, where the pipes become blocked. Since clogging causes a decrease in the overall efficiency of the supercooling system and leads to failure of each component, measures are required to eliminate such clogging from the piping.

[0011] The present invention aims to solve the problems of the prior art as described above by providing a supercooling system capable of efficiently supercooling both fuel and carrier gas.

[0012] In addition, the present invention aims to provide a supercooling system capable of removing clogging when clogging occurs.

[0013] A supercooling system according to one embodiment of the present invention is a supercooling system for supercooling fuel of a ship carrying liquefied gas, comprising: a fuel tank for storing fuel supplied to an engine; a cargo tank for storing liquefied gas; a subcooling unit for supercooling the liquefied gas using a refrigerant; a fuel supply line connected from the fuel tank to the engine to supply fuel to the engine; a fuel recovery line branched from the fuel supply line and connected to the fuel tank; and a fuel supercooling heat exchanger disposed on the fuel recovery line to exchange heat between the refrigerant of the subcooling unit and the fuel, wherein the fuel can be supercooled by the refrigerant in the fuel supercooling heat exchanger.

[0014] In one example, the apparatus further includes a refrigerant transfer line connected to the subcooling unit, through which the refrigerant discharged from the subcooling unit passes through the fuel subcooling heat exchanger and is reintroduced into the subcooling unit; and a refrigerant circulation line through which the refrigerant circulates within the subcooling unit, wherein the refrigerant transfer line may be connected to the refrigerant circulation line.

[0015] In one example, the subcooling unit comprises: a subcooling heat exchanger that exchanges heat between the refrigerant and the liquefied gas; an expander provided in the refrigerant circulation line to expand the refrigerant; and a compressor provided in the refrigerant circulation line to compress the refrigerant, wherein the refrigerant circulation line may include: a first line through which the refrigerant expanded in the expander flows into the compressor via the subcooling heat exchanger; and a second line through which the refrigerant compressed in the compressor flows into the expander via the subcooling heat exchanger.

[0016] In one example, in the subcooling heat exchanger, the refrigerant on the first line can cool both the refrigerant on the second line and the liquefied gas introduced into the subcooling heat exchanger through the liquefied gas subcooling line.

[0017] In one example, the system includes a discharge point where the refrigerant transfer line and the refrigerant circulation line are connected so that the refrigerant is discharged from the refrigerant circulation line to the refrigerant transfer line; and a re-entry point where the refrigerant transfer line and the refrigerant circulation line are connected so that the refrigerant is re-entered from the refrigerant transfer line to the refrigerant circulation line, wherein the discharge point and the re-entry point may be provided inside the subcooling heat exchanger.

[0018] In one example, the discharge point and the re-entry point are provided on the first line, and the discharge point may be provided on the first line between the re-entry point and the expander.

[0019] In one example, the discharge point and the re-entry point are provided on the second line, and the discharge point may be provided on the second line between the re-entry point and the expander.

[0020] In one example, the system may further include a flow control valve provided in the refrigerant transfer line; and a control unit that controls the amount of refrigerant flowing from the refrigerant circulation line to the refrigerant transfer line by controlling the flow control valve.

[0021] In one example, the control unit may further include a temperature sensor for measuring the temperature of the fuel passing through the fuel supercooling heat exchanger, and the control unit may adjust the opening rate of the flow control valve according to the temperature of the fuel measured by the temperature sensor.

[0022] A supercooling system according to one embodiment of the present invention is a supercooling system for supercooling fuel of a ship carrying liquefied gas, comprising: a fuel tank for storing fuel supplied to an engine; a cargo tank for storing liquefied gas; a subcooling unit for supercooling the liquefied gas using a refrigerant; and a fuel supercooling heat exchanger arranged to supercool the fuel using the refrigerant of the subcooling unit and recover it to the fuel tank, wherein the refrigerant may be transferred to the fuel supercooling heat exchanger to supercool the fuel after supercooling the liquefied gas in the subcooling unit, and then recirculated to the subcooling unit.

[0023] A supercooling system according to one embodiment of the present invention is a supercooling system for supercooling fuel of a ship carrying liquefied gas, comprising: a fuel tank for storing fuel supplied to an engine; a cargo tank for storing liquefied gas; a subcooling unit for supercooling the liquefied gas; a fuel supply line connected from the fuel tank to the engine to supply fuel to the engine; a fuel recovery line branched from the fuel supply line and connected to the fuel tank; and a fuel supercooling heat exchanger disposed on the fuel recovery line to heat exchange the liquefied gas supercooled by the subcooling unit with the fuel, wherein in the fuel supercooling heat exchanger, the fuel may be supercooled by the supercooled liquefied gas.

[0024] In one example, it may include a liquefied gas subcooling line that transfers liquefied gas from the cargo tank to the subcooling unit and recovers the liquefied gas supercooled by the subcooling unit to the cargo tank via the fuel subcooling heat exchanger.

[0025] In one example, the liquefied gas subcooling line may further include a bypass line arranged so that a portion of the subcooled liquefied gas bypasses the fuel subcooling heat exchanger.

[0026] In one example, the apparatus may further include a bypass valve provided in the bypass line; and a control unit that controls the amount of liquefied gas bypassing the fuel supercooling heat exchanger through the bypass line by controlling the bypass valve.

[0027] In one example, the control unit may further include a temperature sensor for measuring the temperature of the fuel that has passed through the fuel supercooling heat exchanger, and the control unit may adjust the opening rate of the bypass valve according to the temperature of the fuel measured by the temperature sensor.

[0028] A supercooling system according to one embodiment of the present invention is a supercooling system for supercooling a liquefied gas, comprising: a main heat exchanger for heat exchange between a refrigerant and a liquefied gas; an auxiliary heat exchanger connected in parallel with the main heat exchanger for heat exchange between the refrigerant and the liquefied gas; a refrigerant circulation line through which a refrigerant circulates via the main heat exchanger; a refrigerant auxiliary line branched from the refrigerant circulation line, through which at least a portion of the refrigerant flowing in the refrigerant circulation line passes through the auxiliary heat exchanger and is re-introduced into the refrigerant circulation line; a main supercooling line through which a liquefied gas flows into the main heat exchanger; and an auxiliary supercooling line branched from a branch point of the main supercooling line through which a liquefied gas flows via the auxiliary heat exchanger. It may include a control unit that controls to selectively drive either a first state in which the refrigerant and liquefied gas flow through the main heat exchanger via the refrigerant circulation line and the main subcooling line, or a second state in which the refrigerant and liquefied gas flow through the auxiliary heat exchanger via the refrigerant auxiliary line and the auxiliary subcooling line.

[0029] In one example, the system further includes a front pressure sensor provided on the main supercooling line and positioned at the downstream end of the branch point to measure the pressure at the upstream end of the main heat exchanger; and a downstream pressure sensor provided on the main supercooling line to measure the pressure at the downstream end of the main heat exchanger, and the control unit can switch from the first state to the second state when the pressure difference measured by the front pressure sensor and the downstream pressure sensor exceeds the minimum allowable pressure difference.

[0030] In one example, a first refrigerant valve is provided in the refrigerant circulation line and a second refrigerant valve is provided in the refrigerant auxiliary line, and the control unit can control the first refrigerant valve and the second refrigerant valve to switch from the first state to the second state or from the second state to the first state.

[0031] In one example, the main subcooling line is provided with a first liquefied gas valve positioned downstream of the branch point, and the auxiliary subcooling line is provided with a second liquefied gas valve positioned between the branch point and the auxiliary heat exchanger, and the control unit can control the first liquefied gas valve and the second liquefied gas valve to switch from the first state to the second state or from the second state to the first state.

[0032] In one example, the system further includes an inert gas supply line that supplies an inert gas to the main supercooling line, wherein the inert gas supply line is connected to the main supercooling line at a junction point on the main supercooling line, and the junction point may be provided at the rear end of the branch point.

[0033] In one example, the main subcooling line is provided with a first liquefied gas valve and a third liquefied gas valve positioned between the branch point and the main heat exchanger, and the auxiliary subcooling line is provided with a second liquefied gas valve positioned between the branch point and the auxiliary heat exchanger, and the control unit can control the first liquefied gas valve, the second liquefied gas valve, and the third liquefied gas valve so that inert gas is supplied through the inert gas supply line in the second state.

[0034] In one example, the merging point may be provided between the first liquefied gas valve and the third liquefied gas valve.

[0035] A supercooling system according to one embodiment of the present invention, in a supercooling system for supercooling liquefied gas, may include: a main heat exchanger that exchanges heat between a refrigerant and a liquefied gas; a refrigerant circulation line through which the refrigerant circulates via the main heat exchanger; a main supercooling line through which the liquefied gas flows into the main heat exchanger; a plurality of pumps that pump the liquefied gas so that the liquefied gas flows along the main supercooling line; a front pressure sensor provided on the main supercooling line to measure the pressure at the front end of the main heat exchanger; a rear pressure sensor provided on the main supercooling line to measure the pressure at the rear end of the main heat exchanger; and a control unit that controls the number of pumps driven according to the pressure difference measured by the front pressure sensor and the rear pressure sensor.

[0036] The supercooling system according to the present invention can efficiently supercool both fuel and carrier gas.

[0037] In addition, the supercooling system according to the present invention can remove clogging when clogging occurs.

[0038] FIG. 1 is a drawing illustrating a supercooling system that supercools fuel using a refrigerant according to the present invention.

[0039] FIG. 2 is a drawing illustrating a first embodiment of refrigerant utilization in which the refrigerant transfer line of FIG. 1 is connected to a subcooling unit.

[0040] FIG. 3 is a drawing illustrating a second embodiment of refrigerant utilization in which the refrigerant transfer line of FIG. 1 is connected to a subcooling unit.

[0041] FIG. 4 is a diagram illustrating a supercooling system that supercools fuel using supercooled liquefied gas according to the present invention.

[0042] FIG. 5 is a drawing illustrating a first embodiment of the clogging removal of a supercooling system according to the present invention.

[0043] FIG. 6 is a drawing illustrating a second embodiment of the clogging removal of a supercooling system according to the present invention.

[0044] FIG. 7 is a drawing illustrating a third embodiment of the clogging removal of a supercooling system according to the present invention.

[0045] Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that in assigning reference numerals to the components of each drawing, the same components are given the same reference numeral whenever possible, even if they are shown in different drawings. Furthermore, in describing the embodiments of the present invention, if it is determined that a detailed description of related known components or functions would hinder understanding of the embodiments of the present invention, such detailed description is omitted.

[0046] In addition, terms such as first, second, A, B, (a), (b), etc., may be used when describing the components of the embodiments of the present invention. These terms are intended merely to distinguish the components from other components, and the essence, order, or sequence of the components is not limited by these terms. Where it is stated that a component is "connected," "combined," or "joined" to another component, it should be understood that the component may be directly connected or joined to the other component, but that another component may also be "connected," "combined," or "joined" between each component.

[0047] In this specification, the front-back, left-right, and up-down directions are referred to for convenience of explanation and may be directions orthogonal to one another. However, these directions are determined relatively, and the term "up-down direction" does not necessarily mean a vertical direction.

[0048]

[0049] <Examples of Refrigerant Utilization>

[0050] FIG. 1 is a drawing illustrating a supercooling system (1) that supercools fuel using a refrigerant according to the present invention. FIG. 2 is a drawing illustrating a first embodiment of refrigerant utilization in which the refrigerant transfer line (L3) of FIG. 1 is connected to a subcooling unit (300). FIG. 3 is a drawing illustrating a second embodiment of refrigerant utilization in which the refrigerant transfer line (L3) of FIG. 1 is connected to a subcooling unit (300).

[0051] Hereinafter, a supercooling system (1) according to the present invention will be described with reference to FIGS. 1 to 3.

[0052] The supercooling system (1) according to the present invention can be applied to a vessel carrying liquefied gas, and can supercool both the fuel and the transported liquefied gas. At this time, the fuel and the liquefied gas may be provided as different types. In this embodiment, the fuel is a carbon-free fuel and the liquefied gas is Liquefied Natural Gas (LNG) as one example. However, the concept of the present invention is not limited thereto. In particular, the fuel can be understood as a concept that includes not only carbon-free fuel but also any fuel that can be supercooled by the refrigerant of the present system. In addition, the liquefied gas may also be provided as a liquefied gas other than liquefied natural gas.

[0053] Referring to FIG. 1, the subcooling system (1) may include a fuel tank (110), a cargo tank (120), an engine (210, 220), a subcooling unit (300), a fuel subcooling heat exchanger (410), a temperature sensor (510), a flow control valve (520), and a control unit (not shown). Additionally, as lines connecting the components constituting the subcooling system (1), a fuel supply line (L11), a fuel recovery line (L12), a liquefied gas subcooling line (L2), a refrigerant transfer line (L3), and a refrigerant circulation line (L4) may be provided. In this specification, the connection of two lines means that the two lines are connected so that a liquid or gas can be transferred from one line to the other.

[0054] The fuel tank (110) can store fuel supplied to the engine (210, 220). As described above, carbon-free fuel can be stored in the fuel tank (110). This carbon-free fuel can also be stored in a liquefied state and can have a temperature of about minus 35°C.

[0055] The cargo tank (120) can store liquefied gas to be transported to a ship. Although the cargo tank (120) is depicted as one in FIG. 1, the cargo tank (120) may be provided in multiple numbers. If the cargo tank (120) is provided in multiple numbers, the multiple cargo tanks (120) may each be connected to a subcooling unit (300) for supercooling the liquefied gas stored inside.

[0056] Fuel stored in the fuel tank (110) can be pumped by a fuel pump (111) provided inside the fuel tank (110) and supplied to the engine (210, 220) along the fuel supply line (L11). The engine (210, 220) includes a main engine (210) and a power generation engine (220), the main engine (210) receives fuel to generate propulsion for the ship, and the power generation engine (220) receives fuel to produce electricity required for the ship.

[0057] A fuel supply line (L11) may be connected from a fuel tank (110) to an engine (210, 220) to supply fuel to the engine (210, 220). A fuel supply heat exchanger (230) and a fuel supply pump (240) are provided on the fuel supply line (L11) to adjust the fuel supplied from the fuel tank (110) to the temperature and pressure required by the engine (210, 220). If the fuel is a carbon-free fuel, the fuel may be supplied to the engine (210, 220) at a temperature and pressure of approximately 35°C and 20 bar.

[0058] A fuel recovery line (L12) connected to a fuel supply line (L11) can be branched from the fuel supply line (L11) and connected to a fuel tank (110). By doing so, some of the fuel flowing along the fuel supply line (L11) can be transferred to the fuel recovery line (L12) and recovered into the fuel tank (110). At this time, a fuel subcooling heat exchanger (410) can be placed on the fuel recovery line (L12), and the fuel on the fuel recovery line (L12) can be subcooled by a refrigerant in the fuel subcooling heat exchanger (410). Thus, the branched fuel can be subcooled by passing through the fuel subcooling heat exchanger (410) and stored again in the fuel tank (110).

[0059] The liquefied gas stored in the cargo tank (120) can be pumped by a cargo pump (121) provided inside the cargo tank (120) and returned to the cargo tank (120) via the liquefied gas subcooling line (L2) and through the subcooling unit (300). The liquefied gas can be subcooled by a refrigerant in the subcooling heat exchanger (310) provided in the subcooling unit (300). Thus, the liquefied gas can be subcooled by passing through the subcooling heat exchanger (310) and stored again in the cargo tank (120).

[0060] The subcooling unit (300) subcools liquefied gas using a refrigerant and may include a subcooling heat exchanger (310) that exchanges heat between the refrigerant and the liquefied gas, a compressor (320) that compresses the refrigerant, an expander (330) that expands the refrigerant, and a pressure reducing valve (340) that reduces the pressure of the refrigerant. The subcooling heat exchanger (310), compressor (320), expander (330), and pressure reducing valve (340) may be provided on a refrigerant circulation line (L4) described later and configured so that the refrigerant flows through them.

[0061] Specifically, the refrigerant may flow in a refrigerant circulation line (L4) within the subcooling unit (300). The refrigerant circulation line (L4) refers to a path through which the refrigerant circulates in sequence through the compressor (320), the subcooling heat exchanger (310), the expander (330), and the pressure reducing valve (340). At this time, the refrigerant circulation line (L4) may include a first line (L41) through which the refrigerant expanded in the expander (330) flows into the compressor (320) via the subcooling heat exchanger (310), and a second line (L42) through which the refrigerant compressed in the compressor (320) flows into the expander (330) via the subcooling heat exchanger (310).

[0062] Specifically, the refrigerant can be expanded in the expander (330) to lower its temperature to approximately minus 160°C, and then pass through the pressure reducing valve to lower its temperature to approximately minus 175°C before flowing into the subcooling heat exchanger (310). In the subcooling heat exchanger (310), the refrigerant on the first line (L41) can cool both the refrigerant on the second line (L42) and the liquefied gas that has flowed into the subcooling heat exchanger (310) through the liquefied gas subcooling line (L2). The refrigerant that has cooled the liquefied gas can exit the subcooling heat exchanger (310) and flow into the compressor (320). Additionally, the refrigerant can be compressed in the compressor (320) and flow into the subcooling heat exchanger (310) with its temperature raised to approximately 40°C. As described above, the refrigerant flowing into the subcooling heat exchanger (310) along the second line (L42) can be cooled by the refrigerant on the first line (L41). The refrigerant can be utilized for the supercooling of liquefied gas by circulating along the above path and controlling the temperature.

[0063] In order to utilize the refrigerant on the refrigerant circulation line (L4) for fuel subcooling, a portion of the refrigerant may be transferred to the fuel subcooling heat exchanger (410) through the refrigerant transfer line (L3). The refrigerant transfer line (L3) may be connected to the subcooling unit (300) so that the refrigerant discharged from the subcooling unit (300) may be recirculated to the subcooling unit (300) via the fuel subcooling heat exchanger (410).

[0064] Specifically, the refrigerant transfer line (L3) can be connected to the refrigerant circulation line (L4), thereby allowing at least a portion of the refrigerant flowing along the refrigerant circulation line (L4) to flow into the refrigerant transfer line (L3). Such connection between the refrigerant transfer line (L3) and the refrigerant circulation line (L4) will be described later with reference to the first embodiment of refrigerant utilization according to FIG. 2 and the second embodiment of refrigerant utilization according to FIG. 3.

[0065] The fuel subcooling heat exchanger (410) can subcool the fuel by exchanging heat between the fuel delivered through the fuel recovery line (L12) and the refrigerant delivered through the refrigerant delivery line (L3). To this end, the fuel subcooling heat exchanger (410) can be placed on the fuel recovery line (L12) and the refrigerant delivery line (L3).

[0066] Meanwhile, the fuel recovery line (L12) may be equipped with a temperature sensor (510) positioned downstream of the fuel subcooling heat exchanger (410), and the refrigerant transfer line (L3) may be equipped with a flow control valve (520) positioned upstream of the fuel subcooling heat exchanger (410). The temperature sensor (510) can measure the temperature of the fuel that has passed through the fuel subcooling heat exchanger (410).

[0067] The control unit can control the amount of refrigerant flowing from the refrigerant circulation line (L4) to the refrigerant transfer line (L3) by controlling the flow control valve (520). Specifically, the control unit can control the opening rate of the flow control valve (520) according to the temperature of the fuel measured by the temperature sensor (510). As described above, by controlling the amount of refrigerant flowing into the fuel subcooling heat exchanger (410), the fuel can be subcooled to an appropriate temperature. If the fuel is a carbon-free fuel, the fuel can be subcooled to a temperature of approximately minus 40°C.

[0068] Below, each embodiment regarding the method of connecting the refrigerant transfer line (L3) and the refrigerant circulation line (L4) is described.

[0069] <First Example of Refrigerant Utilization>

[0070] Referring to FIG. 2, the refrigerant transfer line (L3) can be connected to the refrigerant circulation line (L4) at either the first line (L41) or the second line (L42). Specifically, the refrigerant transfer line (L3) can be connected to the refrigerant circulation line (L4) at the discharge point (P1) and the re-inflow point (P2) provided on the refrigerant circulation line (L4) inside the subcooling heat exchanger (310).

[0071] The discharge point (P1) is the point where the refrigerant transfer line (L3) and the refrigerant circulation line (L4) are connected so that the refrigerant is discharged from the refrigerant circulation line (L4) to the refrigerant transfer line (L3), and the re-inflow point (P2) is the point where the refrigerant transfer line (L3) and the refrigerant circulation line (L4) are connected so that the refrigerant is re-inflow from the refrigerant transfer line (L3) to the refrigerant circulation line (L4).

[0072] For convenience of explanation, the refrigerant flowing along the first line (L41) with its temperature lowered by the expansion valve (330) and the pressure reducing valve (340) is referred to as the low-temperature refrigerant, and the refrigerant flowing along the second line (L42) with its temperature raised by the compressor (320) is referred to as the high-temperature refrigerant. However, the terms low temperature and high temperature here should be understood as relative expressions to distinguish between the refrigerant on the first line (L41) and the refrigerant on the second line (L42).

[0073] In the first embodiment of the refrigerant utilization shown in FIG. 2, a discharge point (P1) and a re-inflow point (P2) may be provided on the first line (L41). At this time, the discharge point (P1) may be provided on the first line (L41) between the re-inflow point (P2) and the expander (330).

[0074] In the first embodiment of the refrigerant utilization, a discharge point (P1) and a re-inflow point (P2) are provided on the first line (L41), and the discharge point (P1) is provided upstream of the re-inflow point (P2), so that a refrigerant with a relatively low temperature is discharged at the discharge point (P1), and a refrigerant with a relatively high temperature can be re-inflowed at the re-inflow point (P2) downstream of the discharge point (P1) after passing through the fuel subcooling heat exchanger (410).

[0075] Specifically, the refrigerant whose temperature has been lowered by passing through the expander (330) and the pressure reducing valve (340) can be introduced into the subcooling heat exchanger (310) through the first line (L41). The low-temperature refrigerant flows along the first line (L41) within the subcooling heat exchanger (310), and a portion of it can be introduced into the refrigerant transfer line (L3). The low-temperature refrigerant can be transferred to the fuel subcooling heat exchanger (410) through the refrigerant transfer line (L3) and used to subcool the fuel.

[0076] Additionally, the refrigerant whose temperature has been raised again after passing through the fuel subcooling heat exchanger (410) can be combined with the refrigerant flowing along the first line (L41) in the first line (L41) inside the subcooling heat exchanger (310). At this time, the refrigerant can be combined at the re-entry point (P2) located downstream of the discharge point (P1). The combined refrigerant flows into the compressor (320) along the first line (L41) and is compressed, and can then flow through the subcooling heat exchanger (310), the expansion valve (330), and the pressure reducing valve (340).

[0077] The refrigerant can subcool the liquefied gas in the subcooling heat exchanger (310) by this flow, then be transferred to the fuel subcooling heat exchanger (410) to subcool the fuel, and then be reintroduced into the subcooling unit (300).

[0078] <Second Example of Refrigerant Utilization>

[0079] In the second embodiment of refrigerant utilization illustrated in FIG. 3, the discharge point (P1) and the re-inflow point (P2) may be provided on the second line (L42). At this time, the discharge point (P1) may be provided on the second line (L42) between the re-inflow point (P2) and the expander (330). The second embodiment of refrigerant utilization differs from the first embodiment of refrigerant utilization, in that the discharge point (P1) and the re-inflow point (P2) are provided on the first line (L41), in that the discharge point (P1) and the re-inflow point (P2) are provided on the second line (L42).

[0080] In the second embodiment of the refrigerant utilization, a discharge point (P1) and a re-inflow point (P2) are provided on the second line (L42), and the discharge point (P1) is provided at a downstream end of the re-inflow point (P2), so that the refrigerant with a relatively lower temperature is discharged at the discharge point (P1), and the refrigerant with a relatively higher temperature can be re-inflowed at the re-inflow point (P2) upstream of the discharge point (P1) after passing through the fuel subcooling heat exchanger (410).

[0081] Specifically, the refrigerant whose temperature has been raised by passing through the compressor (320) can be introduced into the subcooling heat exchanger (310) through the second line (L42). As the high-temperature refrigerant flows along the second line (L42) within the subcooling heat exchanger (310), it can be cooled by the low-temperature refrigerant on the first line (L41). Thus, the temperature of the high-temperature refrigerant can gradually decrease along the flow direction of the second line (L42). A portion of the high-temperature refrigerant, whose temperature has been relatively lowered by the cooling process, can be introduced into the refrigerant transfer line (L3) at the discharge point (P1). The refrigerant can be transferred to the fuel subcooling heat exchanger (410) through the refrigerant transfer line (L3) and used to subcool the fuel.

[0082] Additionally, the refrigerant whose temperature has been raised again after passing through the fuel subcooling heat exchanger (410) can be combined with the refrigerant flowing along the second line (L42) inside the subcooling heat exchanger (310). At this time, the refrigerant can be combined at a re-entry point (P2) located upstream of the discharge point (P1). Specifically, the re-entry point (P2) can be determined by considering the temperature of the refrigerant flowing along the second line (L42). The combined refrigerant flows into the expansion valve (330) along the second line (L42) and is expanded, and can then flow through the pressure reducing valve (340), the subcooling heat exchanger (310), and the compressor (320).

[0083] The refrigerant can subcool the liquefied gas in the subcooling heat exchanger (310) by this flow, then be transferred to the fuel subcooling heat exchanger (410) to subcool the fuel, and then be reintroduced into the subcooling unit (300).

[0084] The supercooling system (1) according to the present invention is efficient because it can supercool both fuel and liquefied gas with a single refrigerant through the configuration and arrangement of the configurations described above. In addition, since there is no need to provide separate supercooling systems for fuel and liquefied gas, space can be utilized more efficiently in environments with spatial constraints, such as ships. Furthermore, there is an advantage that the temperature at which the fuel is supercooled can be controlled by adjusting the flow rate of the refrigerant.

[0085]

[0086] <Example of Utilization of Supercooled Liquefied Gas>

[0087] FIG. 4 is a drawing illustrating a supercooling system (2) that supercools fuel using supercooled liquefied gas according to the present invention.

[0088] Hereinafter, with reference to FIG. 4, a supercooling system (2) according to the present invention will be described. However, since the supercooling system (2) according to FIG. 4 differs from the supercooling system (1) according to FIG. 1 to FIG. 3 in the configuration related to the fuel supercooling heat exchanger (420) for supercooling the fuel, the differences will be described mainly, and for identical parts, the description and reference numerals of the embodiments of FIG. 1 to FIG. 3 described above will be used.

[0089] The supercooling system (2) according to the present invention can be applied to a vessel carrying liquefied gas, and can supercool both the fuel and the liquefied gas being transported. At this time, the fuel may be a carbon-free fuel, and the liquefied gas may be liquefied natural gas. However, the concept of the present invention is not limited thereto, and, as with the refrigerant utilization example of FIG. 1, the fuel may be understood as a concept that includes not only carbon-free fuel but also any fuel that can be supercooled by the supercooled liquefied gas. In addition, the liquefied gas may also be provided as a liquefied gas other than liquefied natural gas.

[0090] Referring to FIG. 4, the supercooling system (2) may include a fuel tank (110), a cargo tank (120), an engine (210, 220), a subcooling unit (300), a fuel supercooling heat exchanger (420), a temperature sensor (510), a bypass valve (530), and a control unit (not shown). Additionally, as lines connecting the components constituting the supercooling system (2), a fuel supply line (L13), a fuel recovery line (L14), a liquefied gas supercooling line (L21), and a bypass line (L22) may be provided.

[0091] The fuel tank (110) can store fuel supplied to the engine (210, 220), and the cargo tank (120) can store liquefied gas to be transported to the ship.

[0092] Fuel stored in the fuel tank (110) can be pumped by a fuel pump (111) provided inside the fuel tank (110) and supplied to the engine (210, 220) along the fuel supply line (L13). The fuel supply line (L13) can be connected from the fuel tank (110) to the engine (210, 220) and configured to supply fuel to the engine (210, 220). A fuel supply system (250) can be provided on the fuel supply line (L13), and the temperature and pressure of the engine can be controlled in the fuel supply system.

[0093] A fuel recovery line (L14) connected to a fuel supply line (L13) can be branched from the fuel supply line (L13) and connected to a fuel tank (110). By doing so, some of the fuel flowing along the fuel supply line (L13) can be transferred to the fuel recovery line (L14) and recovered into the fuel tank (110). At this time, a fuel subcooling heat exchanger (420) can be placed on the fuel recovery line (L14), and the fuel on the fuel recovery line (L14) can be subcooled in the fuel subcooling heat exchanger (420). Thus, the branched fuel can be subcooled by passing through the fuel subcooling heat exchanger (420) and stored again in the fuel tank (110).

[0094] The liquefied gas subcooling line (L21) can be configured to transfer liquefied gas from the cargo tank (120) to the subcooling unit (300) and to recover the liquefied gas subcooled by the subcooling unit (300) to the cargo tank (120) via the fuel subcooling heat exchanger (420). The liquefied gas stored in the cargo tank (120) can be pumped by a cargo pump (121) provided inside the cargo tank (120) and stored back in the cargo tank (120) via the subcooling unit (300) along the liquefied gas subcooling line (L21).

[0095] The subcooling unit (300) can subcool liquefied gas using a refrigerant. At this time, the refrigerant can circulate within the subcooling unit (300) through a compressor, a heat exchanger, an expander, a pressure reducing valve, etc., and the refrigerant can be utilized for subcooling liquefied gas by controlling its temperature through the circulating flow. However, the subcooling unit (300) is not limited to having such a configuration and can be understood as a concept that includes any system capable of cooling liquefied gas.

[0096] The fuel subcooling heat exchanger (420) is for subcooling the fuel and can be provided on the fuel recovery line (L14) and the liquefied gas subcooling line (L21) downstream of the subcooling unit (300). The fuel subcooling heat exchanger (420) can exchange heat between the fuel delivered through the fuel recovery line (L14) and the liquefied gas subcooled by the subcooling unit (300) delivered through the liquefied gas subcooling line (L21). In the fuel subcooling heat exchanger (420), the fuel can be subcooled by the subcooled liquefied gas.

[0097] Meanwhile, in the liquefied gas subcooling line (L21), a bypass line (L22) may be provided to allow a portion of the subcooled liquefied gas to bypass the fuel subcooling heat exchanger (420). At this time, a bypass valve (530) may be provided in the bypass line (L22), and the control unit may control the amount of liquefied gas bypassing the fuel subcooling heat exchanger (420) through the bypass line (L22) by controlling the bypass valve (530).

[0098] Additionally, the fuel recovery line (L14) may be equipped with a temperature sensor (510) positioned downstream of the fuel subcooling heat exchanger (420). The temperature sensor (510) can measure the temperature of the fuel that has passed through the fuel subcooling heat exchanger (420).

[0099] The control unit can adjust the opening rate of the bypass valve (530) according to the temperature of the fuel measured by the temperature sensor (510). As described above, the amount of liquefied gas bypassing the fuel subcooling heat exchanger (420) is adjusted according to the opening rate of the bypass valve (530), and accordingly, the amount of liquefied gas passing through the fuel subcooling heat exchanger (420) can also be adjusted. By adjusting the amount of subcooled liquefied gas flowing into the fuel subcooling heat exchanger (420), the fuel can be subcooled to an appropriate temperature.

[0100] The supercooling system (2) according to the present invention is efficient because it can supercool fuel with supercooled liquefied gas through the configuration and arrangement of the configurations described above. Accordingly, since there is no need to provide separate supercooling systems for fuel and liquefied gas, space can be utilized more efficiently in environments with spatial constraints, such as ships. In addition, there is an advantage that the temperature at which the fuel is supercooled can be controlled by adjusting the flow rate of the supercooled liquefied gas introduced into the fuel supercooling heat exchanger (420) for supercooling the fuel.

[0101]

[0102] <Example of Clogging Removal>

[0103] FIG. 5 is a drawing illustrating a first embodiment of clogging removal of a supercooling system (3) according to the present invention. FIG. 6 is a drawing illustrating a second embodiment of clogging removal of a supercooling system (3') according to the present invention. FIG. 7 is a drawing illustrating a third embodiment of clogging removal of a supercooling system (3'') according to the present invention.

[0104] Hereinafter, a supercooling system (3, 3', 3'') according to the present invention will be described with reference to FIGS. 5 to 7. The supercooling system (3, 3', 3'') according to the present invention relates to a supercooling system in which, when clogging occurs due to cryogenic liquefied gas, the supercooling of the liquefied gas can be continuously performed without stopping the operation of the system while removing the clogging. In this embodiment, the liquefied gas is described as liquefied natural gas as one example. However, the concept of the present invention is not limited thereto.

[0105] Each embodiment according to the method of removing clogging is illustrated in FIGS. 5 to 7. A first embodiment of clogging removal is described with reference to FIG. 5, a second embodiment of clogging removal is described with reference to FIG. 6, and a third embodiment of clogging removal is described with reference to FIG. 7.

[0106] <First Example of Clogging Removal>

[0107] Referring to FIG. 5, a supercooling system (3) according to the first embodiment of clogging removal includes a main heat exchanger (311) and an auxiliary heat exchanger (312) for heat-exchanging between a refrigerant and a liquefied gas, and a control unit (not shown) for controlling the flow path of the refrigerant and the liquefied gas. Additionally, a refrigerant circulation line (L4) and a refrigerant auxiliary line (L5) through which the refrigerant flows, and a main supercooling line (L6) and an auxiliary supercooling line (L7) through which the liquefied gas flows may be provided.

[0108] In this embodiment, the main heat exchanger (311) and the auxiliary heat exchanger (312) are arranged in parallel, and when clogging occurs in the main subcooling line (L6), the refrigerant and liquefied gas flowing through the main heat exchanger (311) are flowed to the auxiliary heat exchanger (312), thereby allowing the liquefied gas to be subcooled in the auxiliary heat exchanger (312). Additionally, when the clogging is removed, the refrigerant and liquefied gas are flowed back to the main heat exchanger (311), thereby allowing the liquefied gas to be subcooled in the main heat exchanger (311).

[0109] In the following, the state in which the refrigerant and liquefied gas flow through the main heat exchanger (311) via the refrigerant circulation line (L4) and the main subcooling line (L6) is referred to as the first state. On the other hand, the state in which the refrigerant and liquefied gas flow through the auxiliary heat exchanger (312) via the refrigerant auxiliary line (L5) and the auxiliary subcooling line (L7) is referred to as the second state.

[0110] The main heat exchanger (311) can exchange heat between the refrigerant flowing along the refrigerant circulation line (L4) in the first state and the liquefied gas flowing along the main subcooling line (L6), and thus the liquefied gas can be subcooled by the refrigerant.

[0111] The auxiliary heat exchanger (312) can heat exchange the refrigerant flowing along the auxiliary refrigerant line (L5) in the second state with the liquefied gas flowing along the auxiliary subcooling line (L7), and thus the liquefied gas can be subcooled by the refrigerant.

[0112] The refrigerant circulation line (L4) may be configured so that the refrigerant circulates through the main heat exchanger (311). Specifically, the refrigerant passes through the compressor (320), the main heat exchanger (311), the expansion unit (330), and the main heat exchanger (311) in sequence, and then flows back into the compressor (320), circulating along the refrigerant circulation line (L4) in this manner. At this time, the refrigerant circulation line (L4) may include a first line (L41) through which the refrigerant expanded in the expansion unit (330) flows into the compressor (320) via the main heat exchanger (311), and a second line (L42) through which the refrigerant compressed in the compressor (320) flows into the expansion unit (330) via the main heat exchanger (311).

[0113] The refrigerant auxiliary line (L5) may be branched off from the refrigerant circulation line (L4) so ​​that at least a portion of the refrigerant flowing through the refrigerant circulation line (L4) passes through the auxiliary heat exchanger (312) and then flows back into the refrigerant circulation line (L4). Specifically, the refrigerant auxiliary line (L5) may be branched off from the refrigerant circulation line (L4) at the first line (L41) and may be connected to the refrigerant circulation line (L4) at the discharge point (P3) and the re-entry point (P4) provided in the first line (L41).

[0114] The discharge point (P3) is the point where the refrigerant circulation line (L4) and the refrigerant auxiliary line (L5) are connected so that the refrigerant is discharged from the refrigerant circulation line (L4) to the refrigerant auxiliary line (L5) and flows into the auxiliary heat exchanger (312). The re-inflow point (P4) is the point where the refrigerant circulation line (L4) and the refrigerant auxiliary line (L5) are connected so that the refrigerant is re-inflow from the refrigerant auxiliary line (L5) to the refrigerant circulation line (L4).

[0115] The discharge point (P3) can be provided upstream of the re-entry point (P4), thereby allowing a refrigerant with a relatively lower temperature to be discharged at the discharge point (P3), and the refrigerant with a relatively higher temperature to be re-entered into the refrigerant circulation line (L4) at the re-entry point (P4) downstream of the discharge point (P3). In this way, the refrigerant that is re-entered into the refrigerant circulation line (L4) after the liquefied gas on the auxiliary subcooling line (L7) is subcooled in the auxiliary heat exchanger (312) can again pass through the compressor (320) and the expander (330) on the refrigerant circulation line (L4).

[0116] The main subcooling line (L6) can be configured to allow liquefied gas to flow into the main heat exchanger (311). The main subcooling line (L6) connects a storage tank (not shown) in which liquefied gas is stored with the main heat exchanger (311) to transfer liquefied gas from the storage tank to the main heat exchanger (311) and recover the liquefied gas subcooled in the main heat exchanger (311) to the storage tank.

[0117] The auxiliary subcooling line (L7) may be branched off from one branch point (P5) of the main subcooling line (L6) so that the liquefied gas flows through the auxiliary heat exchanger (312). At this time, the auxiliary subcooling line (L7) may be connected to the storage tank so that the liquefied gas subcooled in the auxiliary heat exchanger (312) is recovered to the storage tank.

[0118] The control unit can control the flow of refrigerant and liquefied gas so that the subcooling system (3) is selectively driven into either a first state or a second state. Specifically, the control unit can drive the subcooling system (3) in a first state where the liquefied gas is subcooled in the main heat exchanger (311), and if it is determined that clogging has occurred, drive the subcooling system (3) in a second state where the liquefied gas is subcooled in the auxiliary heat exchanger (312). Additionally, if it is determined that the clogging has been removed, the control unit can drive the subcooling system (3) back into the first state.

[0119] In order to determine the occurrence of clogging and the removal of clogging, a front pressure sensor (540) and a rear pressure sensor (550) may be provided. The front pressure sensor (540) and the rear pressure sensor (550) are provided on the main supercooling line (L6) to measure the pressure at the front and rear of the main heat exchanger (311).

[0120] Specifically, the upstream pressure sensor (540) can be positioned between the branch point (P5) and the main heat exchanger (311) and can measure the pressure at the upstream end of the main heat exchanger (311). At this time, by positioning the upstream pressure sensor (540) at the downstream end of the branch point, it is possible to determine whether the clogging of the main subcooling line (L6) has been removed in the second state in which the liquefied gas flows into the auxiliary subcooling line (L7). The downstream pressure sensor (550) can be positioned at the downstream end of the main heat exchanger (311) and can measure the pressure at the downstream end of the main heat exchanger (311).

[0121] The control unit can determine whether clogging has occurred in the main supercooling line (L6) through the pressure difference measured by the front pressure sensor (540) and the rear pressure sensor (550). That is, if the pressure difference is greater than a certain amount, it can be determined that clogging has occurred, and if the pressure difference is less than a certain amount, it can be determined that clogging has not occurred.

[0122] Specifically, the control unit can switch from the first state to the second state if the pressure difference measured by the front pressure sensor (540) and the rear pressure sensor (550) exceeds the minimum allowable pressure difference.

[0123] To switch from a first state to a second state or from a second state to a first state, multiple valves may be provided in each line.

[0124] A first refrigerant valve (341) may be provided in the refrigerant circulation line (L4), and a second refrigerant valve (342) may be provided in the refrigerant auxiliary line (L5). The first refrigerant valve (341) may be positioned between the discharge point (P3) and the re-inflow point (P4). Two second refrigerant valves (342) may be provided and positioned at the front and rear ends of the auxiliary heat exchanger (312).

[0125] In the first state, the first refrigerant valve (341) may be opened so that the refrigerant circulates along the refrigerant circulation line (L4), and the second refrigerant valve (342) may be closed so that the refrigerant does not flow into the auxiliary heat exchanger (312) through the refrigerant auxiliary line (L5). On the other hand, in the second state, the first refrigerant valve (341) may be closed and the second refrigerant valve (342) may be opened so that the refrigerant is transferred from the refrigerant circulation line (L4) to the refrigerant auxiliary line (L5) and flows into the auxiliary heat exchanger (312). The control unit may control the first refrigerant valve (341) and the second refrigerant valve (342) to switch from the first state to the second state or from the second state to the first state as described above.

[0126] Meanwhile, a first liquefied gas valve (344) may be provided in the main subcooling line (L6), and a second liquefied gas valve (345) may be provided in the auxiliary subcooling line (L7). The first liquefied gas valve (344) may be provided at the rear end of the branch point (P5) and positioned between the branch point (P5) and the main heat exchanger (311). The second liquefied gas valve (345) may be positioned between the branch point (P5) and the auxiliary heat exchanger (312).

[0127] In the first state, the first liquefied gas valve (344) may be opened and the second liquefied gas valve (345) may be closed so that the liquefied gas flows into the main heat exchanger (311) along the main subcooling line (L6) but not into the auxiliary heat exchanger (312). On the other hand, in the second state, the first liquefied gas valve (344) may be closed and the second liquefied gas valve (345) may be opened so that the liquefied gas does not flow into the main heat exchanger (311) along the main subcooling line (L6) but flows into the auxiliary heat exchanger (312) along the auxiliary subcooling line (L7). The control unit may control the first liquefied gas valve (344) and the second liquefied gas valve (345) to switch from the first state to the second state or from the second state to the first state as described above.

[0128] The supercooling system (3) according to the present invention can move the refrigerant and liquefied gas flowing through the main heat exchanger (311) to the auxiliary heat exchanger (312) so that supercooling of the liquefied gas occurs in the auxiliary heat exchanger (312) when clogging occurs. Accordingly, supercooling of the liquefied gas can be achieved in the auxiliary heat exchanger (312). As a result, the liquefied gas does not flow in the main supercooling line (L6) where clogging occurred, and clogging can be removed as the temperature gradually rises. Alternatively, clogging can be removed by a separate clogging removal operation (e.g., supplying an inert gas). In this way, since supercooling of the liquefied gas occurs in the auxiliary heat exchanger (312) while clogging is being removed, there is an advantage that supercooling of the liquefied gas can be continuously achieved.

[0129] <Second Example of Clogging Removal>

[0130] FIG. 6 is a drawing of a supercooling system (3') according to a second embodiment of clogging removal. The second embodiment of clogging removal shown in FIG. 6 differs from the first embodiment of clogging removal shown in FIG. 5 in that an inert gas supply line (L8) is additionally provided. Therefore, the description will focus on these differences, and for identical parts, the description and reference numerals of the first embodiment of clogging removal described above will be used.

[0131] A supercooling system (3') according to the second embodiment of clogging removal includes a main heat exchanger (311) and an auxiliary heat exchanger (312) for heat-exchanging between a refrigerant and a liquefied gas, and a control unit (not shown) for controlling the flow paths of the refrigerant and the liquefied gas. Additionally, a refrigerant circulation line (L4) and a refrigerant auxiliary line (L5) through which the refrigerant flows, and a main supercooling line (L6) and an auxiliary supercooling line (L7) through which the liquefied gas flows may be provided. Additionally, an inert gas supply line (L8) for supplying an inert gas to the main supercooling line (L6) may be provided. The inert gas may be nitrogen gas.

[0132] In this embodiment, the main heat exchanger (311) and the auxiliary heat exchanger (312) are arranged in parallel, and when clogging occurs in the main subcooling line (L6), the refrigerant and liquefied gas flowing through the main heat exchanger (311) are flowed to the auxiliary heat exchanger (312), thereby allowing the liquefied gas to be subcooled in the auxiliary heat exchanger (312). Additionally, when the clogging is removed, the refrigerant and liquefied gas are flowed back to the main heat exchanger (311), thereby allowing the liquefied gas to be subcooled in the main heat exchanger (311).

[0133] The control unit can control the flow of refrigerant and liquefied gas so that the subcooling system (3) is selectively driven into either a first state or a second state. Specifically, the control unit can drive the subcooling system (3) in a first state where the liquefied gas is subcooled in the main heat exchanger (311), and if it is determined that clogging has occurred, drive the subcooling system (3) in a second state where the liquefied gas is subcooled in the auxiliary heat exchanger (312). Additionally, if it is determined that the clogging has been removed, the control unit can drive the subcooling system (3) back into the first state.

[0134] Although not shown in the drawing, pressure sensors may be provided at the upstream and downstream ends of the main heat exchanger (311) on the main supercooling line (L6) to determine whether clogging has occurred and whether clogging has been removed, and whether clogging has occurred can be determined through the pressure difference measured by the pressure sensors at the upstream and downstream ends. However, the concept of the present invention is not limited thereto, and whether clogging has occurred may also be determined through a separate configuration other than pressure sensors.

[0135] Meanwhile, in the second state, inert gas can be supplied to the main supercooling line (L6) through the inert gas supply line (L8). To this end, the inert gas supply line (L8) can be connected to the main supercooling line (L6) at a junction point (P6) on the main supercooling line (L6). At this time, the junction point (P6) can be provided at the downstream end of the branch point (P5).

[0136] A first refrigerant valve (341) may be provided in the refrigerant circulation line (L4), and a second refrigerant valve (342) may be provided in the refrigerant auxiliary line (L5). In the first state, the first refrigerant valve (341) may be opened and the second refrigerant valve (342) may be closed. Conversely, in the second state, the first refrigerant valve (341) may be closed and the second refrigerant valve (342) may be opened. The control unit may control the first refrigerant valve (341) and the second refrigerant valve (342) to switch from the first state to the second state or from the second state to the first state.

[0137] In the main subcooling line (L6), a first liquefied gas valve (344) and a third liquefied gas valve (346) are provided between the branch point (P5) and the main heat exchanger (311), and in the auxiliary subcooling line (L7), a second liquefied gas valve (345) is provided between the branch point (P5) and the auxiliary heat exchanger (312). At this time, the second liquefied gas valve may be provided between the branch point (P5) and the junction point (P6).

[0138] In the first state, the first liquefied gas valve (344) and the third liquefied gas valve (346) are opened and the second liquefied gas valve (345) can be closed so that the liquefied gas flows into the main heat exchanger (311) along the main subcooling line (L6) but not into the auxiliary heat exchanger (312). On the other hand, in the second state, the third liquefied gas valve (346) can be closed and the second liquefied gas valve (345) can be opened so that the liquefied gas does not flow into the main heat exchanger (311) along the main subcooling line (L6) but flows into the auxiliary heat exchanger (312) along the auxiliary subcooling line (L7).

[0139] Additionally, in the second state, the first liquefied gas valve (344) may be opened so that inert gas can be supplied through the inert gas supply line (L8). A junction point (P6) is provided between the first liquefied gas valve (344) and the third liquefied gas valve (346), and in the second state, the first liquefied gas valve (344) is opened and the third liquefied gas valve (346) is closed, thereby preventing the inert gas from flowing into the auxiliary supercooling line (L7). That is, in the second state, the inert gas flows into the main supercooling line (L6) downstream of the junction point (P6), and clogging on the main supercooling line (L6) can be removed by the inert gas.

[0140] The control unit can control the first liquefied gas valve (344), the second liquefied gas valve (345), and the third liquefied gas valve (346) to switch from the first state to the second state or from the second state to the first state as described above. Additionally, the control unit can control the first liquefied gas valve (344), the second liquefied gas valve (345), and the third liquefied gas valve (346) so that inert gas is supplied through the inert gas supply line (L8) in the second state.

[0141] The supercooling system (3') according to the present invention can flow the refrigerant and liquefied gas flowing through the main heat exchanger (311) to the auxiliary heat exchanger (312) so that supercooling of the liquefied gas occurs in the auxiliary heat exchanger (312) when clogging occurs. Accordingly, supercooling of the liquefied gas can be achieved in the auxiliary heat exchanger (312). In addition, while supercooling of the liquefied gas is taking place in the auxiliary heat exchanger (312), clogging can be removed more quickly by supplying an inert gas to remove clogging. As such, since supercooling of the liquefied gas is taking place in the auxiliary heat exchanger (312) while clogging is being removed, there is an advantage that supercooling of the liquefied gas can be achieved continuously.

[0142] <Third Example of Clogging Removal>

[0143] FIG. 7 is a drawing of a supercooling system (3'') according to a third embodiment of clogging removal. The third embodiment of clogging removal shown in FIG. 7 differs from the first embodiment of clogging removal shown in FIG. 5 in that it does not have an auxiliary heat exchanger (312) and provides a plurality of pumps (610, 620) that provide driving force to flow liquefied gas to a main heat exchanger (311). Therefore, the description will focus on these differences, and for identical parts, the description and reference numerals of the first embodiment of clogging removal described above will be used.

[0144] A subcooling system (3'') according to the third embodiment of clogging removal may include a main heat exchanger (311) that heat exchanges between a refrigerant and a liquefied gas, and a control unit (not shown) that controls the number of pumps (610, 620) driven. Additionally, a refrigerant circulation line (L4) through which the refrigerant flows and a main subcooling line (L6) through which the liquefied gas flows may be provided.

[0145] The main subcooling line (L6) can be connected to a plurality of pumps (610, 620), respectively. The plurality of pumps (610, 620) can pump the liquefied gas so that it flows along the main subcooling line (L6). To this end, the plurality of pumps (610, 620) can be placed inside a storage tank (not shown) where the liquefied gas is stored.

[0146] Meanwhile, in order to determine the occurrence and removal of clogging, a front pressure sensor (540) and a rear pressure sensor (550) may be provided. The front pressure sensor (540) and the rear pressure sensor (550) are provided on the main supercooling line (L6) to measure the pressure at the front and rear of the main heat exchanger (311), respectively.

[0147] Specifically, the upstream pressure sensor (540) can be positioned between the branch point (P5) and the main heat exchanger (311) and can measure the pressure at the upstream end of the main heat exchanger (311). The downstream pressure sensor (550) can be positioned at the downstream end of the main heat exchanger (311) and can measure the pressure at the downstream end of the main heat exchanger (311).

[0148] The control unit can control the pumps (610, 620) to adjust the number of pumps (610, 620) driven according to the pressure difference measured by the front pressure sensor (540) and the rear pressure sensor (550). That is, if the pressure difference increases, the number of pumps (610, 620) driven can be increased, and if the pressure difference decreases, the number of pumps (610, 620) driven can be reduced. If the number of pumps increases, the flow rate of the liquefied gas on the main subcooling line (L6) increases, and accordingly, the temperature at which the liquefied gas is subcooled can be increased. Therefore, if the pressure difference increases, the number of pumps (610, 620) driven can be increased to prevent clogging from occurring in the main subcooling line (L6) or to remove clogging that has occurred.

[0149] In this embodiment, two pumps are provided as an example, but the concept of the present invention is not limited thereto, and more pumps may be provided.

[0150] The supercooling system (3'') according to the present invention can eliminate clogging by adjusting the number of pumps that provide driving force to flow liquefied gas to the main heat exchanger (311) through the main supercooling line (L6).

[0151]

[0152] The foregoing description is merely an illustrative explanation of the technical concept of the present invention, and those skilled in the art to which the present invention pertains will be able to make various modifications and variations within the scope of the essential characteristics of the present invention. Accordingly, the embodiments disclosed in the present invention are intended to explain, not limit, the technical concept of the present invention, and the scope of the technical concept of the present invention is not limited by these embodiments. The scope of protection of the present invention shall be interpreted by the claims below, and all technical concepts within an equivalent scope shall be interpreted as being included within the scope of rights of the present invention.

Claims

1. In a supercooling system for supercooling fuel of a vessel carrying liquefied gas, A fuel tank that stores fuel supplied to the engine; Cargo tank for storing liquefied gas; A subcooling unit for supercooling the above liquefied gas; A fuel supply line connected from the fuel tank to the engine to supply fuel to the engine; A fuel recovery line branched from the fuel supply line and connected to the fuel tank; and It includes a fuel subcooling heat exchanger disposed on the fuel recovery line and heat-exchanging the fuel with the liquefied gas subcooled by the subcooling unit, and A supercooling system in which the fuel in the above fuel supercooling heat exchanger is supercooled by supercooled liquefied gas.

2. In Claim 1, A supercooling system comprising a liquefied gas supercooling line that transfers liquefied gas from the cargo tank to the subcooling unit and recovers the liquefied gas supercooled by the subcooling unit to the cargo tank via the fuel supercooling heat exchanger.

3. In Claim 2, A supercooling system further comprising, in the above-mentioned liquefied gas supercooling line, a bypass line arranged so that a portion of the supercooled liquefied gas bypasses the fuel supercooling heat exchanger.

4. In Claim 3, A bypass valve provided in the above bypass line; and A supercooling system further comprising a control unit that controls the amount of liquefied gas bypassing the fuel supercooling heat exchanger through the bypass line by controlling the bypass valve.

5. In Claim 4, It further includes a temperature sensor for measuring the temperature of the fuel that has passed through the fuel supercooling heat exchanger, and A supercooling system in which the control unit adjusts the opening rate of the bypass valve according to the temperature of the fuel measured by the temperature sensor.

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