Patent Description:
Methods for recovering and effectively using cold energy of a low-temperature liquid such as liquefied natural gas (LNG) have been proposed.

Document <CIT> discloses cold energy recovery from liquefied LNG or hydrogen by means of cascaded Rankine cycles.

Patent Document <NUM> describes a floating facility provided with a power generation device that generates power using LNG cold energy. This power generation device includes a thermodynamic cycle that uses a heat medium as a working fluid, and generates power using a generator connected to a turboexpander driven by the heat medium (working fluid) flowing through a circuit. In the thermodynamic cycle, engine cooling water, seawater, or the like is used as a high-temperature heat source that exchanges heat with the heat medium in an evaporator, and LNG is used as a low-temperature heat source that exchanges heat with the heat medium in a condenser. The LNG is vaporized (regasified) in the condenser, and then supplied to a device or the like that uses the regasified LNG as fuel.

The use of liquid hydrogen (LH2) as fuel for a marine vessel or the like has been proposed. The storage temperature of liquid hydrogen is approximately -<NUM>, which is lower than the storage temperature of LNG (approximately -<NUM>). For this reason, when liquid hydrogen is used instead of LNG in a device including a thermodynamic cycle that recovers and utilizes LNG cold energy, a fluid (a working fluid, a fluid used as a high-temperature heat source, or the like) flowing through a heat exchanger (a condenser, an evaporator, or the like) may become colder and frozen, and the thermodynamic cycle may not work properly.

In light of the above circumstances, an object of at least one embodiment of the present invention is to provide a cold energy recovery facility and a marine vessel capable of suppressing freezing of a fluid flowing through a heat exchanger while recovering cold energy of liquid hydrogen.

A cold energy recovery facility according to an embodiment of the present invention includes the features of claim <NUM>. Another embodiment of the invention is described in claim <NUM>.

Additionally, a marine vessel according to at least an embodiment of the present invention includes a ship, the cold energy recovery facility described above provided at the ship, and an engine or a fuel cell provided at the ship, the engine or the fuel cell using, as fuel, the hydrogen vaporized in the first heat exchanger.

According to at least an embodiment of the present invention, provided are a cold energy recovery facility and a marine vessel capable of suppressing freezing of a fluid flowing through a heat exchanger while recovering cold energy of liquid hydrogen.

Some embodiments of the present invention will be described below with reference to the attached drawings. It is intended, however, that dimensions, materials, shapes, relative arrangements or the like of components described in the embodiments or illustrated in the drawings are only examples and not intended to limit the scope of the present invention to them.

<FIG> is a schematic diagram of a marine vessel to which a cold energy recovery facility according to some examples is applied. As illustrated in <FIG>, a marine vessel <NUM> includes a ship <NUM> (floating body), a cold energy recovery facility <NUM> including a liquid hydrogen tank <NUM> provided on the ship <NUM>, and an engine <NUM> provided in the ship <NUM>.

The ship <NUM> includes a bow 2a having a shape that reduces the resistance that the ship <NUM> receives from a fluid such as seawater, and a stern 2b to which a rudder <NUM> for adjusting the traveling direction of the ship <NUM> can be attached.

The engine <NUM> may be configured to generate power for driving a propeller <NUM> serving as a propulsor. The engine <NUM> may include an engine or a turbine, or may include an electric motor.

As illustrated in <FIG>, the marine vessel <NUM> may be provided with a fuel cell <NUM>. The electric motor serving as the engine <NUM> may be driven by power generated by the fuel cell <NUM>.

In the example illustrated in <FIG>, the marine vessel <NUM> is a marine vessel propelled using hydrogen stored in the liquid hydrogen tank <NUM> as fuel. As described in detail below, the cold energy recovery facility <NUM> includes a hydrogen line <NUM> for guiding hydrogen from the liquid hydrogen tank <NUM> to a supply destination, and a first heat exchanger <NUM> provided on the hydrogen line <NUM>. In the cold energy recovery facility <NUM>, liquid hydrogen from the liquid hydrogen tank <NUM> is vaporized by heat exchange in the first heat exchanger <NUM> to become hydrogen gas. This hydrogen gas is heated to an appropriate temperature by a heater or the like as necessary and then supplied as fuel to the engine <NUM> or the fuel cell <NUM>.

In some examples the marine vessel <NUM> may be a tanker for carrying liquid hydrogen stored in a liquid hydrogen tank.

Note that the cold energy recovery facility according to the present invention is not limited to a facility installed on a marine vessel. The cold energy recovery facility according to some examples may be installed on an aquatic facility other than a marine vessel, or may be installed on land.

Hereinafter, the cold energy recovery facility <NUM> according to some embodiments and examples not covered by the invention will be described. <FIG> are each a schematic diagram of the cold energy recovery facility <NUM> according to an embodiments and examples not covered by the invention.

As illustrated in <FIG>, the cold energy recovery facility <NUM> according to some embodiments includes the liquid hydrogen tank <NUM> for storing liquid hydrogen, the hydrogen line <NUM> through which the hydrogen from the liquid hydrogen tank <NUM> flows, a first circuit <NUM> through which a first working medium flows, a first turboexpander <NUM> provided in the first circuit <NUM>, a second circuit <NUM> through which a second working medium having a freezing point higher than the first working medium flows, and a second turboexpander <NUM> provided in the second circuit <NUM>. The cold energy recovery facility <NUM> further includes the first heat exchanger <NUM> for heat exchange between the hydrogen of the hydrogen line <NUM> and the first working medium of the first circuit <NUM>, a second heat exchanger <NUM> for heat exchange between the first working medium of the first circuit <NUM> and the second working medium of the second circuit <NUM>, and a third heat exchanger <NUM> for heat exchange between the second working medium of the second circuit <NUM> and a heat medium.

The liquid hydrogen in the liquid hydrogen tank <NUM> is fed by the pump <NUM> provided on the hydrogen line <NUM> and vaporized by heat exchange with the first heat medium at the first heat exchanger <NUM>. The vaporized hydrogen may be supplied to a supply destination such as the engine <NUM> or the fuel cell <NUM> via the hydrogen line <NUM>. A first hydrogen heater <NUM> configured to heat the hydrogen may be provided downstream of the first heat exchanger <NUM> in the hydrogen line <NUM>. The first hydrogen heater <NUM> may be configured to heat the hydrogen by heat exchange with the heat medium (e.g., seawater).

The first circuit <NUM> and the first turboexpander <NUM> form a part of a first thermodynamic cycle <NUM> that uses the liquid hydrogen as a low-temperature heat source in the first heat exchanger <NUM> and uses the second working medium as a high-temperature heat source in the second heat exchanger <NUM>.

The first thermodynamic cycle <NUM> illustrated in <FIG> is a Rankine cycle including the first turboexpander <NUM> provided in the first circuit <NUM>, the first heat exchanger <NUM> provided downstream of the first turboexpander <NUM>, a pump <NUM> provided downstream of the first heat exchanger <NUM>, and the second heat exchanger <NUM> provided downstream of the pump <NUM>. A first generator <NUM> may be connected to the first turboexpander <NUM>.

The first turboexpander <NUM> is configured to expand the first working medium, which is in a gas state and flows through the first circuit <NUM> of the first thermodynamic cycle <NUM>. Thus, the first generator <NUM> is driven to generate power. The first heat exchanger <NUM> is configured to condense the first working medium, output from the first turboexpander <NUM> in a gas state, by heat exchange with the liquid hydrogen serving as a low-temperature heat source. The pump <NUM> is configured to pressurize the first working medium condensed by the first heat exchanger <NUM> into a liquid. The second heat exchanger <NUM> is configured to evaporate the liquid first working medium pressurized by the pump <NUM> by heat exchange with the second working medium serving as a high-temperature heat source.

The first thermodynamic cycle <NUM> configured in this way can drive the first turboexpander <NUM> and/or the first generator <NUM> by using cold energy of the liquid hydrogen recovered by heat exchange in the first heat exchanger <NUM>.

The second circuit <NUM> and the second turboexpander <NUM> form a part of a second thermodynamic cycle <NUM> that uses the first working medium as a low-temperature heat source in the second heat exchanger <NUM> and uses the heat medium as a high-temperature heat source in the third heat exchanger <NUM>.

The second thermodynamic cycle <NUM> illustrated in <FIG> is a Rankine cycle including the second turboexpander <NUM> provided in the second circuit <NUM>, the second heat exchanger <NUM> provided downstream of the second turboexpander <NUM>, a pump <NUM> provided downstream of the second heat exchanger <NUM>, and the third heat exchanger <NUM> provided downstream of the pump <NUM>. A second generator <NUM> may be connected to the second turboexpander <NUM>.

The second turboexpander <NUM> is configured to expand the second working medium, which is in a gas state and flows through the second circuit <NUM> of the second thermodynamic cycle <NUM>. Thus, the second generator <NUM> is driven to generate power. The second heat exchanger <NUM> is configured to condense the second working medium, output from the second turboexpander <NUM> in a gas state, by heat exchange with the first working medium serving as a low-temperature heat source. The pump <NUM> is configured to pressurize the second working medium condensed by the second heat exchanger <NUM> into a liquid. The third heat exchanger <NUM> is configured to evaporate the liquid second working medium pressurized by the pump <NUM> by heat exchange with the heat medium serving as a high-temperature heat source.

The second thermodynamic cycle <NUM> configured in this way can drive the second turboexpander <NUM> and/or the second generator <NUM> by using cold energy of the liquid hydrogen recovered by heat exchange with the first working medium in the second heat exchanger <NUM>.

The heat medium is supplied to the third heat exchanger <NUM> via a heat medium line <NUM>. The heat medium line <NUM> may be provided with a pump <NUM> for feeding the heat medium.

As the second working medium described above, a fluid used as a working medium in a conventional cold energy recovery cycle of an LNG marine vessel or the like can be used. For example, an organic refrigerant such as R1234zee can be used.

As the first working medium described above, a fluid having a lower freezing point than the second working medium can be used. For example, nitrogen (N2) or a noble gas such as argon (Ar) can be used.

As the heat medium supplied to the third heat exchanger <NUM>, seawater, a cooling fluid (cooling water or cooling oil) obtained after cooling a high-temperature device (e.g., an engine or a calculator described below), or the like can be used. The heat medium supplied to the third heat exchanger <NUM> may be a fluid having a higher freezing point than the second working medium.

Note that the first hydrogen heater <NUM> provided on the hydrogen line <NUM> may be supplied with the same heat medium as the heat medium supplied to the third heat exchanger <NUM>. As illustrated in, for example, <FIG>, the heat medium may be supplied to the first hydrogen heater <NUM> via a diverging line <NUM> that diverges from the heat medium line <NUM> passing through the third heat exchanger <NUM>. Alternatively, in some embodiments, the first hydrogen heater <NUM> may be supplied with a heat medium different from the heat medium supplied to the third heat exchanger <NUM>.

In the embodiments described above, the freezing point of the first working medium is lower than that of the second working medium in the cold energy recovery facility <NUM> including the first thermodynamic cycle <NUM> that uses the first working medium and uses the liquid hydrogen as a low-temperature heat source in the first heat exchanger <NUM>, and the second thermodynamic cycle <NUM> that uses the second working medium and uses the first working medium as a low-temperature heat source in the second heat exchanger <NUM>. Thus, in the first thermodynamic cycle <NUM>, heat exchange is performed between the first working medium having a relatively low freezing point and cryogenic liquid hydrogen, so that the first working medium does not easily freeze in the first heat exchanger <NUM>. In addition, in the second thermodynamic cycle <NUM>, heat exchange is performed in the third heat exchanger <NUM> between the second working medium having a relatively high freezing point and the heat medium serving as a high-temperature heat source. Thus, even when the heat medium is a fluid having a relatively high freezing point (e.g., seawater), the heat medium does not easily freeze in the third heat exchanger <NUM>. Thus, according to the embodiments described above, it is possible to suppress freezing of the fluids flowing through the heat exchangers while recovering cold energy of the liquid hydrogen.

In addition, in the embodiments described above, the first turboexpander <NUM> and the second turboexpander <NUM> are driven in a multi-stage thermodynamic cycle including the first thermodynamic cycle and the second thermodynamic cycle. Thus, the overall power of the turbines can be increased as compared to a conventional configuration that employs a single-stage thermodynamic cycle. When the first generator <NUM> and the second generator <NUM> are connected to the first turboexpander <NUM> and the second turboexpander <NUM>, respectively, the overall power generation amount can be increased as compared to a conventional configuration that employs a single-stage thermodynamic cycle.

In some embodiments and examples not covered by the invention, as illustrated in, for example, <FIG>, the cold energy recovery facility <NUM> further includes a second hydrogen heater <NUM> provided downstream of the first heat exchanger <NUM> and upstream of the first hydrogen heater <NUM> in the hydrogen line <NUM>. The second hydrogen heater <NUM> is configured to heat the hydrogen in the hydrogen line <NUM> by heat exchange with at least some of the second working medium discharged from the second turboexpander <NUM> of the second thermodynamic cycle <NUM>.

In the embodiments and examples not covered by the invention illustrated in <FIG> and <FIG>, the second heat exchanger <NUM> and the second hydrogen heater <NUM> are provided in parallel in the second circuit <NUM>. Specifically, the second hydrogen heater <NUM> is provided on a bypass line <NUM> provided to bypass the second heat exchanger <NUM> in the second circuit <NUM>. The bypass line <NUM> is provided to diverge from the second circuit <NUM> on a side downstream of the second turboexpander <NUM> and upstream of the second heat exchanger <NUM> and merge into the second circuit <NUM> on a side downstream of the second heat exchanger <NUM> and upstream of the pump <NUM> (i.e., upstream of the third heat exchanger <NUM>).

In the example illustrated in <FIG> and the embodiment illustrated in <FIG> the second heat exchanger <NUM> and the second hydrogen heater <NUM> are provided in series in the second circuit <NUM>. Specifically, the second hydrogen heater <NUM> is provided downstream of the second turboexpander <NUM> and upstream of the second heat exchanger <NUM> in the second circuit <NUM>.

In the embodiments described above, in the hydrogen line <NUM> for guiding the hydrogen to the supply destination, the second hydrogen heater <NUM> for heat exchange between the hydrogen and the second working medium is provided upstream of the first hydrogen heater <NUM> for heat exchange between the hydrogen and the heat medium. Thus, in the first hydrogen heater <NUM>, heat exchange occurs between the heat medium and the hydrogen, the temperature of which has been increased by heat exchange with the second working medium in the second hydrogen heater <NUM>. Thus, even when the heat medium supplied to the first hydrogen heater <NUM> is a fluid having a relatively high freezing point (e.g., seawater), the heat medium does not easily freeze in the first hydrogen heater <NUM>. Consequently, freezing of the fluid flowing through the first hydrogen heater <NUM> (heat exchanger) can be suppressed.

In some embodiments, as illustrated in, for example, <FIG>, the cold energy recovery facility <NUM> further includes a third hydrogen heater <NUM> provided downstream of the second hydrogen heater <NUM> and upstream of the first hydrogen heater <NUM> in the hydrogen line <NUM>.

In the exemplary embodiment illustrated in <FIG>, the third hydrogen heater <NUM> is configured to heat the hydrogen by heat exchange with an intermediate medium circulating in an intermediate medium circulation line <NUM>. The intermediate medium circulation line <NUM> is provided with an intermediate medium cooler <NUM> for heating the intermediate medium by heat exchange with the heat medium, and a pump <NUM>. Thus, by the intermediate medium circulating in the intermediate medium circulation line <NUM>, heat of the heat medium is transferred to the hydrogen via the intermediate medium, thereby heating the hydrogen.

An example of the intermediate medium includes an organic medium such as glycol water or propane.

Note that the intermediate medium circulation line <NUM> may be provided with an intermediate medium tank <NUM> for storing the intermediate medium. Further, the intermediate medium cooler <NUM> may be configured to be supplied with the heat medium via a diverging line <NUM> that diverges from the heat medium line <NUM>.

According to the embodiments described above, the third hydrogen heater <NUM> for heat exchange between the hydrogen and the intermediate medium flowing through the intermediate medium circulation line <NUM> is provided downstream of the second hydrogen heater <NUM> and upstream of the first hydrogen heater <NUM> in the hydrogen line <NUM>, and the intermediate medium cooler <NUM> for heating the intermediate medium by heat exchange with the heat medium (seawater) is provided on the intermediate medium circulation line <NUM>. Thus, in the third hydrogen heater <NUM>, the hydrogen after being heated in the second hydrogen heater <NUM> is further heated by heat exchange with the intermediate medium transporting heat of the heat medium. Thus, freezing of the heat medium in the first hydrogen heater <NUM> located downstream of the third hydrogen heater <NUM> in the hydrogen line <NUM> can be more effectively suppressed.

In the embodiments and the examples not covered by the invention illustrated in <FIG>, to more reliably prevent freezing of the heat medium in the first hydrogen heater <NUM>, the temperature of the second working medium supplied to the second hydrogen heater <NUM> (i.e., the temperature at the outlet of the second turboexpander <NUM>) may need to be adjusted (to be increased to some extent). In such a case, the temperature of the second working medium at the outlet of the second turboexpander <NUM> can be adjusted, for example, as follows.

<FIG> is a schematic diagram of the cold energy recovery facility <NUM> according to one example, and illustrates a modification example of the cold energy recovery facility <NUM> illustrated in <FIG>.

In the example illustrated in <FIG>, a storage tank <NUM> for storing the second working medium is provided downstream of the second heat exchanger <NUM> (more specifically, downstream of the merging point of the bypass line <NUM>) and upstream of the pump <NUM> in the second circuit <NUM>. The storage tank <NUM> is a tank for storing a surplus of the second working medium so that the second working medium in a liquid state can be stably delivered, even when the balance between evaporation and condensation of the second working medium in the second thermodynamic cycle <NUM> changes.

The storage tank <NUM> is provided with a pressure sensor <NUM> for detecting the pressure inside the storage tank <NUM>. Also, the rotational speed of the pump <NUM> is controlled based on the pressure value in the storage tank <NUM> detected by the pressure sensor <NUM>.

The pressure of a high-pressure part (part between the outlet of the pump <NUM> and the inlet of the second turboexpander <NUM>) in the second circuit <NUM> is controlled by the delivery pressure of the pump <NUM>, and the pressure of a low-pressure part (part between the outlet of the second turboexpander <NUM> and the inlet of the pump <NUM>) is controlled by the temperature of the condensate of the second working medium.

Thus, first, the rotational speed of the pump <NUM> is adjusted to change the flow rate of the second working medium in the second circuit <NUM>. When the flow rate of the second working medium is changed, the temperature of the cooling medium at the outlet of the second heat exchanger <NUM> changes, and thus the pressure in the storage tank <NUM> changes. By feeding back the pressure inside the storage tank <NUM>, which is detected by the pressure sensor <NUM>, to the pump <NUM>, the pressure of the low-pressure part can be controlled. This can also adjust the temperature of the second working medium at the outlet of the second turboexpander <NUM>.

In this way, the temperature of the second working medium supplied to the second hydrogen heater <NUM> (i.e., the temperature at the outlet of the second turboexpander <NUM>) can be adjusted appropriately.

The above mechanism for adjusting the pressure and/or temperature of the second circuit <NUM> (configuration including the storage tank <NUM> and the pressure sensor <NUM>) is applicable to each of the examples and embodiments illustrated in <FIG>.

Note that, although not specifically illustrated, a storage tank for storing the first working medium may be provided downstream of the first heat exchanger <NUM> and upstream of the pump <NUM> in the first circuit <NUM> in some embodiments. By providing this storage tank, a surplus of the first working medium can be stored so that the first working medium in a liquid state can be stably delivered, even when the balance between evaporation and condensation of the first working medium in the first thermodynamic cycle <NUM> changes.

In some embodiments, as illustrated in, for example, <FIG>, the cold energy recovery facility <NUM> includes a working medium heater <NUM> for heating the first working medium upstream of the first turboexpander <NUM> in the first circuit <NUM>. The working medium heater <NUM> is provided downstream of the second heat exchanger <NUM> and upstream of the first turboexpander <NUM> in the first circuit <NUM>. In the embodiment illustrated in <FIG>, the working medium heater <NUM> is configured to heat the first working medium by heat exchange with the heat medium. The working medium heater <NUM> is supplied with the heat medium via a diverging line <NUM> diverging from the heat medium line <NUM>.

According to the embodiments described above, the working medium heater <NUM> for heating the first working medium flowing upstream of the first turboexpander <NUM> in the first circuit <NUM> is provided. Thus, the temperature of the working medium at the inlet of the first turboexpander <NUM> can be increased. Thus, the heat drop between the inlet and outlet of the first turboexpander <NUM> can be increased, whereby the power of the first turboexpander <NUM> can be increased.

Note that in the examples and embodiments illustrated in <FIG>, since the second working medium is cooled in the second hydrogen heater <NUM> provided in the second circuit <NUM>, the amount of heat exchange between the first working medium and the second working medium in the second heat exchanger <NUM> may be reduced as compared to a case where the second hydrogen heater <NUM> is not provided. Even in such a case, since the gas temperature at the inlet of the first turboexpander <NUM> can be increased by providing the above-described working medium heater <NUM>,the power reduction of the first turboexpander <NUM> can be suppressed.

In some examples and embodiments, as illustrated in, for example, <FIG> and <FIG>, the cold energy recovery facility <NUM> includes an air conditioning cycle <NUM> that uses a third working medium as a cooling medium. The air conditioning cycle <NUM> includes a third circuit <NUM> through which the third working medium circulates, a condenser <NUM> for condensing the third working medium, an expansion valve <NUM> for expanding the condensed third working medium, an evaporator <NUM> for evaporating the expanded third working medium, and a compressor <NUM> for compressing the third working medium in a gas state. The condenser <NUM>, the expansion valve <NUM>, the evaporator <NUM>, and the compressor <NUM> are provided in the third circuit <NUM>. The compressor <NUM> is driven by a motor <NUM>.

The condenser <NUM> is configured to condense the third working medium of the air conditioning cycle <NUM> by heat exchange with the working medium in a gas state upstream of the turboexpander of the first thermodynamic cycle <NUM> or the second thermodynamic cycle <NUM>. In the example illustrated in <FIG>, the condenser <NUM> is configured to condense the third working medium by heat exchange with the first working medium in a gas state upstream of the first turboexpander <NUM> in the first circuit <NUM> that forms the first thermodynamic cycle <NUM>. In the embodiment illustrated in <FIG>, the condenser <NUM> is configured to condense the third working medium by heat exchange with the second working medium in a gas state upstream of the second turboexpander <NUM> in the second circuit <NUM> that forms the second thermodynamic cycle <NUM>.

The evaporator <NUM> is configured to evaporate the third working medium by heat exchange with the heat medium supplied via a heat medium line <NUM>. The heat medium line <NUM> may be provided with a pump <NUM> for feeding the heat medium. The heat medium supplied to the evaporator <NUM> may be water, seawater, or a cooling fluid for cooling a device.

According to the embodiments described above, the first working medium or the second working medium can be heated by heat exchange with the third working medium in the condenser <NUM>, into which the high-temperature high-pressure third working medium compressed by the compressor <NUM> flows in the air conditioning cycle <NUM>. Thus, the heat drop between the inlet and the outlet of the first turboexpander <NUM> or the second turboexpander <NUM> can be increased, so that the power of the first turboexpander <NUM> or the second turboexpander <NUM> can be increased.

Note that the configuration of the air conditioning cycle <NUM> is not limited to the illustrated configuration, and various known air conditioning cycles can be applied.

In some embodiments, as illustrated in, for example, <FIG>, the cold energy recovery facility <NUM> includes a supply line <NUM> for supplying the first working medium to a device <NUM>, and a return line <NUM> for returning the first working medium from the device <NUM> to the first circuit <NUM>. The supply line <NUM> diverges from the first circuit <NUM> on an upstream side of the first turboexpander <NUM>, and the return line <NUM> merges into the first circuit <NUM> on a downstream side of the first turboexpander <NUM>. The first circuit <NUM> is configured such that an inert substance (e.g., nitrogen or a noble gas such as argon) serving as the first working medium circulates. Note that in <FIG>, the supply line <NUM> is provided with a valve <NUM> for adjusting the amount of the first working medium flowing through the supply line <NUM>.

According to the embodiments described above, the inert substance is used as the first working medium, and the supply line <NUM> diverging from the first circuit <NUM> on an upstream side of the first turboexpander <NUM>, and the return line <NUM> merging into the first circuit <NUM> on a downstream side of the first turboexpander <NUM> are provided. Thus, the pressure difference between the inlet and the outlet of the first turboexpander <NUM> in the first circuit <NUM> can be used to supply the inert substance in a gas state (inert gas) to the device <NUM> via the supply line <NUM>, and return the gas of the inert substance from the device <NUM> to the first circuit <NUM> via the return line <NUM>. In this way, the first working medium being an inert substance can be used effectively for another purpose.

The device <NUM> described above may be, for example, a gas transport tube for transporting combustible gas. The gas transport tube may have a double tube structure including an inner peripheral pipe for allowing the combustible gas to flow and an outer peripheral pipe provided around the outer periphery of the inner peripheral pipe. Then, the gas of the inert substance may be supplied to the outer peripheral pipe of the gas transport tube via the supply line <NUM> described above. Note that the gas transport tube described above may be a pipe constituting the hydrogen line <NUM>.

According to the embodiments described above, since the gas (inert gas) of the first working medium being an inert substance is supplied to the outer peripheral pipe of the gas transport tube having a double tube structure, the combustible gas is transferred by the inert gas even after leaking from the inner peripheral pipe, and thus leakage can be detected early by a gas detector. In this way, the first working medium can be used effectively for early detection of gas leakage.

As described above, the heat medium supplied to the third heat exchanger <NUM> via the heat medium line <NUM> may include the cooling fluid (cooling water or cooling oil) after cooling the high-temperature device.

In this case, the cooling fluid that has cooled the high-temperature device is supplied to the third heat exchanger <NUM> as the heat medium. Thus, the cooling fluid that has cooled the high-temperature device as a high-temperature heat source for actuating the thermodynamic cycle can be used to suppress freezing of the fluid flowing through the heat exchanger while recovering cold energy of the liquid hydrogen.

The above high-temperature device may include a calculator. <FIG> is a schematic diagram of a calculator, which is an example of the high-temperature device. The calculator <NUM> illustrated in <FIG> is an immersion server configured to be cooled by being immersed in refrigerant oil <NUM> in a liquid state.

The calculator <NUM> is installed in an immersion tank <NUM> in a state of being immersed in the refrigerant oil <NUM> in a liquid state. Additionally, a condenser <NUM> is provided above the calculator <NUM> in the immersion tank <NUM>. The immersion tank <NUM> has a hermetically sealed structure. The refrigerant oil <NUM> in a liquid state and refrigerant oil <NUM> in a gas state coexist in the immersion tank <NUM>. A cooling fluid (e.g., cooling water or cooling oil) is supplied to the condenser <NUM> via a cooling fluid line <NUM>. Note that the cooling fluid line <NUM> is provided with a pump <NUM>.

In the immersion tank <NUM>, the refrigerant oil <NUM> in a liquid state is vaporized by being subject to heat from the calculator <NUM>. Also, the refrigerant oil <NUM> in a gas state is cooled by the condenser <NUM> and liquefied. By repeating the cycle of vaporization and liquefaction of the refrigerant oil, heat from the calculator <NUM> is transferred to the cooling fluid via the refrigerant oil and the condenser <NUM> in the immersion tank <NUM>. In this way, the calculator <NUM> is cooled by the cooling fluid.

The cooling fluid discharged from a condenser <NUM> in the cooling fluid line <NUM> is supplied to the third heat exchanger <NUM> via the heat medium line <NUM>. Note that the cooling fluid discharged from the third heat exchanger <NUM> in the heat medium line <NUM> may again be supplied to the condenser <NUM> of the immersion tank <NUM> via the cooling fluid line <NUM>.

Note that the calculator serving as the high-temperature device described above is not limited to the immersion server. In some embodiments, the calculator may be another known liquid-cooled calculator, for example, a water-cooled calculator in which the processor is cooled by water.

According to the embodiments described above, the cooling fluid that has cooled the calculator <NUM> is supplied to the third heat exchanger <NUM> as the heat medium. Thus, the cooling fluid that has cooled the calculator <NUM> as the high-temperature heat source for actuating the thermodynamic cycle can be used to suppress freezing of the fluid flowing through the heat exchanger while recovering cold energy of the liquid hydrogen.

In the present specification, an expression of relative or absolute arrangement such as "in a direction", "along a direction", "parallel", "orthogonal", "centered", "concentric" or "coaxial" shall not be construed as indicating only the arrangement in a strict literal sense, and also includes a state where the arrangement is relatively displaced by a tolerance, or by an angle or a distance that can still achieve the same function.

For example, expressions indicating a state of being equal such as "same," "equal," or "uniform" shall not be construed as indicating only a state of being strictly equal but also as indicating a state in which there is a tolerance or a difference as long as the same function can be obtained.

In addition, in the present specification, an expression of a shape such as a rectangular shape or a cylindrical shape shall not be construed as only a geometrically strict shape, and also includes a shape with unevenness or chamfered corners or the like within the range in which the same effect can be achieved.

Claim 1:
A cold energy recovery facility comprising:
a liquid hydrogen tank (<NUM>) configured to store liquid hydrogen;
a first circuit (<NUM>) configured to circulate a first working medium;
a second circuit (<NUM>) configured to circulate a second working medium having a freezing point higher than the first working medium;
a first turboexpander (<NUM>) provided in the first circuit (<NUM>), the first turboexpander (<NUM>) being configured to be driven by the first working medium in a gas state;
a second turboexpander (<NUM>) provided in the second circuit (<NUM>), the second turboexpander (<NUM>) being configured to be driven by the second working medium in a gas state;
a first heat exchanger (<NUM>) configured to vaporize the liquid hydrogen from the liquid hydrogen tank (<NUM>) by heat exchange with the first working medium;
a second heat exchanger (<NUM>) configured to vaporize the first working medium in a liquid state by heat exchange with the second working medium; and
a third heat exchanger (<NUM>) configured to vaporize the second working medium in a liquid state by heat exchange with a heat medium, wherein
the first circuit (<NUM>) and the first turboexpander (<NUM>) form a part of a first thermodynamic cycle that uses the liquid hydrogen as a low-temperature heat source in the first heat exchanger (<NUM>), and
the second circuit (<NUM>) and the second turboexpander (<NUM>) form a part of a second thermodynamic cycle that uses the first working medium as a low-temperature heat source in the second heat exchanger; and
wherein the cold energy recovery facility is characterized in that it further comprises a working medium heater (<NUM>) provided downstream of the second heat exchanger (<NUM>) and upstream of the first turboexpander (<NUM>) in the first circuit (<NUM>), the working medium heater (<NUM>) being configured to heat the first working medium flowing through the first circuit (<NUM>).