Method and system for calculating transition parameter of liquefied gas storage medium

Abstract

To provide a system capable of minimizing evaporation loss when liquefied gas is transported or stored.SOLUTION: In a computer-implemented method and system for calculating transition parameters of a liquefied gas storage medium, the storage medium comprises at least one sealed, non-refrigerated tank 11, the transition parameters characterize the change of a two-phase mixture 13 contained in the sealed non-refrigerated tank 11 between an initial state and a final state, the two-phase mixture 13 comprises a liquid phase and a gas phase, and the transition parameters may be a duration of transition, a liquid bleed rate and a vapor bleed rate.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a method and system for calculating transition parameters of a liquefied gas storage medium. More specifically, the transition parameters characterize the thermodynamic processes of a two-phase mixture of liquefied gas and its vapor contained in one or more sealed non-refrigerated tanks.

Background Art

[0002] Liquefied gas is a gas at normal temperature and pressure that becomes liquid by cooling or compression.

[0003] Sealed adiabatic non-refrigerated tanks are generally used to transport cryogenic liquefied gases such as liquefied petroleum gas (also called "LPG") transported at temperatures in the range of -50°C to 0°C, liquid hydrogen (also called "LH2") transported at a temperature of -253°C, or liquefied natural gas (hereinafter called "LNG") transported at a temperature of -162°C. These tanks can also be intended to store liquefied gas used as fuel for propelling onshore, marine or aircraft vehicles.

[0004] A tank containing liquefied gas cooled to a low temperature appears as a two-phase mixture of a liquid and its vapor, the liquefied gas covered by a "gas ceiling".

[0005] When transporting or storing liquefied gas, the tank can be subject to pressure fluctuations. When heat penetrates through the tank wall, the liquefied gas evaporates and the pressure of the gas ceiling rises. Conversely, any vapor extraction, for example to supply fuel to the engine of a liquefied gas-propelled vehicle, reduces the pressure in the gas ceiling.

[0006] However, if the pressure is too low, there is a risk of deforming or separating ( "collapsing") the sealing film of the tank. If the pressure is too high, there is a risk of deteriorating the sealing film and damaging the tank itself. However, the structural integrity of the film and the tank containing the liquefied gas is of particular importance considering the flammability or explosiveness of the liquid being transported or stored, such as LNG.

[0007] To protect against the damaging effects of any overpressure or negative pressure, the tank is equipped with a safety valve that automatically opens when the set pressure is exceeded, and a vacuum shut-off valve that automatically opens when the pressure falls below the set pressure.

[0008] To control pressure fluctuations within the tank within the set pressure range of the vacuum shut-off valve and safety valve, the operator may decide to extract liquid or vapor.

[0009] To limit the pressure rise in the tank, the evaporated gas may be burned or exhausted at the operator's discretion, if permitted by regulatory conditions. In other situations, if the engine of a liquefied gas propulsion vehicle is supplied by steam extraction, the operator may limit the pressure drop in the tank by facilitating liquid extraction, which allows for forced vaporization to supplement the engine supply.

[0010] European Patent No. 3390893 describes a method and system for real-time calculation of the duration of pressure rise in a non-refrigerated tank containing LNG, following an iterative method up to the set pressure of a safety valve. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] European Patent No. 3390893 [Overview of the Initiative] [Problems that the invention aims to solve]

[0012] When transporting or storing liquefied gas, it is beneficial to have a high degree of operational flexibility and thus obtain flexibility in the supply chain. Therefore, one objective underlying some aspects of the present invention is to be able to calculate, in real-time or in advance, transition parameters, namely the duration of pressure fluctuations, the liquid pumping rate or the vapor pumping rate, and to characterize the thermodynamic behavior of the liquefied gas contained in a sealed non-refrigerated tank. This information is a decision-making and optimization tool for the operator, and in particular enables the operator to develop management scenarios in order to minimize evaporation losses when transporting or storing liquefied gas.

[0013] One idea behind the present invention is to directly calculate the transition parameters that characterize the thermodynamic process of the two-phase mixture of liquefied gas and its vapor contained in one or more sealed non-refrigerated tanks by completing the mass balance and energy balance between the initial state and the final state specified by the operator.

Means for Solving the Problems

[0014] According to one embodiment, the present invention is a computer-implemented method for calculating the transition parameters of a liquefied gas storage medium, wherein the storage medium comprises at least one sealed non-refrigerated tank, the transition parameters characterize the change of the two-phase mixture contained in the sealed non-refrigerated tank between the initial state and the final state, the two-phase mixture comprises a liquid phase and a gas phase, and the transition parameters are the duration τ of the transition, the liquid pumping rate m l or the vapor pumping rate m v and provides a computer-implemented method. The method is - For the liquid phase and gas phase of the initial state, based on the initial liquid phase temperature T l,i , the initial gas phase temperature T v,i , the initial gas phase pressure P i , the initial liquid phase volume V l,i and the initial liquid phase composition x l,i , the initial mass densities ρ l,i and ρ v,i , as well as the initial internal mass energy U l,iand U v,i The steps to determine, - For the final liquid and gas phases, the equation of state and the final gas phase pressure P. f Based on this, the final mass density ρ l,f and ρ v,f , final internal mass energy U l,f and U v,f , as well as final mass enthalpy H l,f and H v,f The steps to determine, - A step of calculating the transition parameter using the following formula,

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[0015] Since mass and energy are broad-spectrum properties, the conservation equations for mass and energy in a multi-tank system are determined by the sum of these same equations considered for each tank. Accordingly, according to another embodiment, the storage medium comprises multiple tanks, and for the liquid and gas phases, the initial and final mass densities, initial and final internal mass energies, and final mass enthalpy are determined for each tank, and the transition parameters are calculated using the following equations.

number

[0016] According to a particular embodiment, the transition parameter is the transition duration τ and the vapor extraction velocity m v and liquid extraction velocity m l This is determined in advance.

[0017] According to an alternative embodiment, the transition parameter is the steam extraction rate m v The liquid extraction velocity is m l The transition time t is predetermined.

[0018] According to another alternative embodiment, the transition parameter is the liquid extraction velocity m l The transition time t and the steam extraction rate m are as follows: v This is determined in advance.

[0019] According to a particular embodiment, the storage medium comprises at least one level sensor configured to determine the volume of the liquid phase in at least one sealed, non-refrigerated tank, and the initial volume V of the liquid phase l,i This is determined by the level sensor.

[0020] According to a particular embodiment, the storage medium comprises at least one temperature sensor configured to measure the temperature of the gas phase in at least one sealed, non-refrigerated tank, and at least one temperature sensor configured to measure the temperature of the liquid phase, wherein the initial temperature of the gas phase T v,i and the initial temperature T of the liquid phase l,i This is measured by a temperature sensor.

[0021] According to a particular embodiment, the storage medium comprises at least one pressure sensor configured to measure the pressure of the gas phase in at least one sealed, non-refrigerated tank, and the initial pressure P of the gas phase i This is measured by a pressure sensor.

[0022] According to a particular embodiment, the storage medium comprises at least one composition sensor configured to determine the composition of the liquid phase in at least one sealed, non-refrigerated tank, and the initial composition of the liquid phase x l,i This is determined by a composition sensor.

[0023] According to a particular embodiment, the storage medium includes a flow sensor configured to measure the steam extraction mass flow rate or liquid extraction mass flow rate leaving a sealed, non-refrigerated tank, and the liquid extraction velocity ml or steam extraction speed m v This is determined by the flow sensor.

[0024] According to one embodiment, the storage medium comprises at least one sealed, non-refrigerated tank equipped with a safety valve, and the final pressure of the gas phase P f The pressure is below the set pressure of the safety valve, and the initial pressure P of the gas phase is below that. i That's all.

[0025] According to another embodiment, the storage medium comprises at least one sealed, non-refrigerated tank equipped with a vacuum shutoff valve, and the final pressure of the gas phase P f This is greater than or equal to the set pressure of the vacuum shutoff valve, and the initial pressure P of the gas phase. i The following applies:

[0026] According to certain embodiments, the two-phase mixture is a flammable mixture.

[0027] According to another specific embodiment, the two-phase mixture is liquefied natural gas. According to yet another specific embodiment, the two-phase mixture may be liquefied petroleum gas or liquefied hydrogen.

[0028] According to certain embodiments, a sealed, non-refrigerated tank serves as a fuel reservoir for propelling land, sea, air, or space vehicles.

[0029] According to another specific embodiment, the offshore vehicle is a liquefied natural gas-propelled tanker or vessel.

[0030] According to embodiments, the present invention also provides a non-temporary computer-readable medium containing program instructions that, when executed by an apparatus, cause the apparatus to perform the method described above. The apparatus may be a computer or similar hardware.

[0031] According to one embodiment, the present invention also provides a system for calculating transition parameters of a liquefied gas storage medium that characterize the change of a two-phase mixture between an initial state and a final state, wherein the transition parameters are the duration of the transition τ and the liquid extraction velocity m.l or steam extraction speed m v The present invention provides a system that can be used to achieve this. The system comprises a storage medium including at least one sealed, non-refrigerated tank containing a two-phase mixture, wherein the two-phase mixture includes a liquid phase and a gas phase; a computing device configured to perform one of the aforementioned methods; and a human-machine interface that interacts with the computing device to inform an operator of the calculated transition parameters.

[0032] According to one embodiment, the present invention also provides a land, sea, or aircraft vehicle comprising a fuel reservoir for propelling the vehicle and the aforementioned system configured to calculate the transition parameters of the fuel tank. [Brief explanation of the drawing]

[0033] The present invention will be better understood and further objectives, details, features and advantages will become clearer through the following description of some specific embodiments of the invention, which are provided merely as non-limiting examples with reference to the accompanying drawings.

[0034] [Figure 1] This is a schematic diagram of a liquefied gas propulsion vessel. [Figure 2] This is a schematic cross-sectional view of a liquefied gas carrier. [Figure 3] This is a flowchart showing a method for calculating transition parameters according to one embodiment of the present invention. [Figure 4] Figure 3 is a schematic cross-sectional view of a liquefied gas storage system in which the method can be implemented. [Figure 5] A schematic diagram of an interface that can be used to communicate input data and / or transition parameters specific to the storage system to the operator is shown. [Modes for carrying out the invention]

[0035] The following embodiments describe a powered offshore vehicle, a liquefied gas propulsion tanker, or a vessel comprising at least one sealed, non-refrigerated tank that serves as a reservoir for transporting liquefied gas or supplying liquefied gas to one or more engines of the vehicle.

[0036] The common shapes of sealed, non-refrigerated tanks can be polyhedral (e.g., prismatic), cylindrical, spherical, or various other types. Non-refrigerated tanks can have a single or double sealing membrane. The sealing membrane is generally made of thin stainless steel sheet or sterling steel. The primary membrane is generally in direct contact with the liquefied gas at very low temperatures.

[0037] Figure 1 shows a liquefied gas propulsion vessel 1 equipped with a non-refrigerated, sealed tank 2 that acts as a reservoir for storing liquefied gas intended to be supplied to its engine.

[0038] Figure 2 shows a liquefied gas carrier or tanker 3 equipped with four sealed, non-refrigerated tanks 4, 5, 6, and 7.

[0039] It is known that when heat penetrates through the walls of a sealed, non-refrigerated tank, the temperature inside the tank rises, causing the liquefied gas contained within to evaporate, and consequently, the pressure in the gas ceiling increases.

[0040] In LNG tankers or LNG-powered vessels, evaporative gas (abbreviated as BOG, or "boil-off gas") can be used to supply the main engines that propel the ship and auxiliary engines that generate onboard electricity. If the evaporative gas flow is greater than the engine consumption, the excess is directed to one or two boilers or, if permitted by regulatory conditions, discharged to suppress overpressure caused by evaporation. Conversely, if the evaporative gas flow is less than the engine consumption, LNG extraction can be performed. Forced evaporation of the extracted liquefied gas (abbreviated as FBOG, or "forced evaporative gas") then allows the difference in flow rates to be offset between natural evaporation and engine consumption, and limits the drop in the gas ceiling contained in tanks 2, 4, 5, 6, or 7.

[0041] To avoid drying losses due to burning or venting excess gas evaporated in the event of overpressure, the operator shall, either in advance or in real time, characterize the thermodynamic behavior of the LNG contained in sealed, non-refrigerated tanks 2, 4, 5, 6, or 7 by transition parameters, namely the duration τ of the pressure fluctuation and the steam extraction rate m. v and liquid extraction velocity m l It is necessary to be able to know this.

[0042] Figure 3 is a flowchart illustrating the method for calculating transition parameters. The transition parameters characterize the thermodynamic change between an initial state 8 and a final state 9 of a two-phase mixture of liquefied gas and vapor contained in sealed, non-refrigerated tanks 2, 4, 5, 6, or 7. At a given time point, the thermodynamic state of the two-phase mixture is described by a set of state variables that characterize its macroscopic physical properties. The initial state 8 corresponds to the thermodynamic state of the two-phase mixture specified by the operator, or to the thermodynamic state of the two-phase mixture when the method for calculating transition parameters is invoked. The final state 9 corresponds to the thermodynamic state of the two-phase mixture specified by the operator.

[0043] According to the first embodiment, all physical properties (mass density, internal energy, and enthalpy) of the two-phase mixture can be determined by knowing the temperature, pressure, volume, and composition of the liquefied gas and its vapor in the initial state 8 and the final state 9.

[0044] In the initial state 8, for the liquid and gas phases, the calculated data 82, i.e., the mass density ρ, is used. l,i and ρ v,i , and internal mass energy U l,i and U v,i This is input data 81, namely the liquidus temperature T l,i , gas phase temperature T v,i , gas phase pressure P i liquid phase volume V l,i and liquid phase composition x l,i Determined based on: Temperature, pressure, and volume can be measured by sensors or specified by the operator. Composition of liquefied gas x l,i The composition of that vapor x v,i Set the following: In particular, if the liquefied gas is LNG, its composition x l,i This is specified in the quality certificate and bill of lading issued at the time of loading into sealed, non-refrigerated tanks 2, 4, 5, 6, or 7, or measured using a composition sensor, or pre-calculated using an LNG "aging" model.

[0045] In the final state 9, the operator receives input data 91, namely gas phase P. f Specify the pressure. The two-phase mixture is assumed to be in thermodynamic equilibrium, and the liquefied gas is assumed to be at its bubble point. According to these assumptions, the gas phase P f The pressure is liquefied gas T l,f The temperature and the steam inside the tank v,f Set both temperatures to be equal. Composition of liquefied gas x l,f and the composition x of its vapor v,iThis is determined based on the equation of state. In a preferred embodiment, this equation of state is a three-parameter cubic equation of state derived from the Redlich-Kwong-Peng-Robinson equation developed by Martin Cismondi and Jorgen Mollerup ("Development and application of a three-parameter RK-PR equation of state," Fluid Phase Equilibria, 232, 2005, pp. 74-89). For the liquid and gas phases, calculated data 92, i.e., mass density ρ l,f and ρ v,f , internal mass energy U l,f and U v,f , as well as mass enthalpy H l,f and H v,f This is determined based on the input data 91 specified by the operator.

[0046] When the two-phase mixture changes between the initial state 8 and the final state 9, the liquid extraction velocity m l , steam extraction speed m v It is assumed that the power Q contributed by heat intrusion through the tank walls is constant. The liquid and vapor extraction rates can be measured by flow sensors or specified by the operator. The output Q is determined based on the tank evaporation rate (BOR), which is usually provided by the manufacturer. This parameter characterizes the thermal resistance of the tank insulation to any heat intrusion. In a preferred embodiment, the BOR is corrected by taking into account the tank's fill level.

[0047] Solving the conservation-based mass and energy equations between the initial state 8 and the final state 9 makes it possible to directly calculate the desired transition parameter values.

[0048] According to one embodiment, the extraction speed m of the set steam v and the extraction velocity of the liquid m lIn this process, the operator calculates the pressure rise time τ in the sealed, non-refrigerated tanks 2, 4, 5, 6, or 7 by using the initial pressure P i Final pressure P exceeding this value f For example, if an LNG tanker or LNG-propelled vessel is moored in a port area where regulations stipulate that the main and auxiliary engines must be shut down (the vessel then supplied with shore electricity), and that the burning or discharge of evaporated LNG is prohibited, the operator needs to know how long the vessel can remain near the dock while maintaining an acceptable pressure level for the operability of the tanks.

[0049] According to another embodiment, the steam extraction velocity m v and the extraction velocity of the liquid m l When setting up, the operator calculates the pressure drop time τ in the sealed, non-refrigerated tanks 2, 4, 5, 6, or 7 by using the initial pressure P i Final pressure P below f This specifies the timeframe. For example, if the engines of an LNG tanker or LNG propulsion vessel consume more than the flow of naturally evaporated gases, the operator needs to know how much time is available before it is necessary to perform liquid extraction to supply the engines and maintain a pressure level acceptable for the operability of the tanks.

[0050] According to another embodiment, the set transition period τ and the liquid extraction rate m l In this process, the operator controls the steam extraction rate m in the sealed, non-refrigerated tanks 2, 4, 5, 6, or 7. v To calculate the final pressure P f To specify this, for example, if the downtime of an LNG tanker or LNG propulsion vessel is predetermined, the operator may need to know the steam extraction rate that should be applied to supply power to the auxiliary engines that generate onboard electricity while maintaining the pressure within acceptable limits for tank operability.

[0051] Figure 4 is a schematic cross-sectional view of a system 10 for calculating transition parameters using the method described above, within a sealed non-refrigerated tank 11, the walls of which are attached to a polyhedral support structure 12. The sealed non-refrigerated tank 11 contains a two-phase mixture 13 of liquefied gas and vapor at very low temperatures and includes a level sensor 14, temperature sensors 151 to 155, pressure sensor 16, composition sensor 17, vapor extraction flow rate sensor 18, and a pump located at the bottom of the tank, equipped with a flow rate sensor 19, which allows for liquid extraction. The sealed non-refrigerated tank 11 includes a safety valve 20 and a vacuum shut-off valve 21. The system 10 includes a computing device 22 connected by wired or wireless links to the sensors 14, 151 to 155, 16, 17, 18 and 19 described above, to enable obtaining measurements of the physical quantities necessary to calculate the transition parameters.

[0052] According to one embodiment, the level sensor 14 for determining the volume of liquefied gas in the tank can be a capacitive sensor, a float, a radar, or a laser. In a preferred embodiment, temperature sensors 151 to 155 can also perform this function.

[0053] According to one embodiment, the temperature sensors 151-155 are temperature probes, and generally there are four or five probes distributed across the entire height of the tank at known elevations. In a preferred embodiment, the probes are positioned such that at least one probe 153, 154, or 155 is immersed in the liquefied gas, and at least one probe 151 or 152 is located at the gas phase level. Measuring the level of the liquefied gas in the tank allows for the identification of the immersed probes and the probes located in the gas phase based on the known elevation of each probe. When several probes are immersed in the liquefied gas, the initial temperature of the liquid phase T l,i Temperature measurements are averaged to determine the initial temperature T of the gas phase. Similarly, when several probes are located in the gas phase, the temperature measurements are averaged to determine the initial temperature T of the gas phase. v,i It is averaged to determine the result.

[0054] According to one embodiment, the pressure sensor 16 is a pressure gauge that measures the pressure of the gas phase inside the tank. Next, the initial pressure P of the gas ceiling is measured. i To determine this, the pressure is corrected by taking atmospheric pressure into account.

[0055] According to one embodiment, the composition sensor 17 determines the initial composition x of the liquid phase. l,i This is a gas-phase chromatograph that analyzes a sample of re-evaporated liquefied gas to determine the properties of the gas.

[0056] According to one embodiment, the flow sensor 18 for measuring steam extraction is a flow meter installed at the inlets of the boiler and engine to which the gas is supplied. The flow sensor 19 for measuring the flow rate of liquefied gas extraction is a flow meter located at the pump outlet. In a preferred embodiment, the flow meter is a Coriolis effect mass flow meter.

[0057] In one embodiment, the tank is equipped with a safety valve 20 that automatically opens at its set pressure. For tanks containing LNG, the set pressure is generally set to 700 mbarg or 2 barg. For example, if the main engine of an LNG tanker or LNG propulsion vessel is shut down and the consumption of the auxiliary engine is insufficient to compensate for the flow of evaporated gas, and regulatory conditions prohibit the combustion or discharge of excess gas, the operator needs to know the time τ of the gas ceiling pressure rise relative to the pressure for the valve to open automatically. In this case, the operator needs to know the initial gas phase pressure P which is below the set pressure of the safety valve 20. i The final gas phase pressure P is as described above. f Specify.

[0058] According to one embodiment, the tank is equipped with a vacuum shut-off valve 21 that automatically opens at its set pressure. In the case of a tank containing LNG, the set pressure of the vacuum shut-off valve is generally set to 20 mbarg or 50 mbarg. For example, if the engine of an LNG tanker or LNG propulsion vessel consumes more than the flow rate of naturally evaporated gas, the operator needs to know the pressure drop time τ from the gas ceiling to the pressure in order to automatically open the vacuum shut-off valve. In this case, the operator needs to know the initial gas phase pressure P which is above the set pressure of the vacuum shut-off valve 21.i Specify the final vapor pressure P as follows. f

[0059] FIG. 5 schematically shows an interface for notifying an operator of input data (pressure, temperature, volume, and composition) specific to the gas storage system and the calculated transition parameters. In this example, the liquefied gas is LNG cooled to a temperature of -161.15°C. The initial volume V of the liquefied gas contained in the tank l,i is expressed as a percentage of the filling rate.

[0060] According to one embodiment, the operator specifies that the final pressure P f and the input data specific to the two-phase mixture 13 are physical quantities measured by one or more level sensors 14, temperature sensors 151 to 155, pressure sensors 16, composition sensors 17, and flow sensors 18 and 19. The measured physical quantities are transmitted to the operator via a human-machine interface that interacts with the computing device 22.

[0061] As an alternative embodiment, the operator specifies the final pressure P f and all or part of the input data specific to the two-phase mixture 13 that is known (e.g., the initial composition x of the liquid phase at the time of loading of the liquefied gas shown in the quality certificate and the bill of lading l,i ) or pre-calculated (e.g., the initial composition x of the liquid phase determined from the age degradation model of the liquefied gas l,i ).

[0062] Some of the elements shown, particularly the computing device 22, can be manufactured in various forms in a single or distributed manner by hardware and / or software components. Available hardware components are specific ASICs, FPGAs, or microprocessors. Software components can be described in various programming languages, such as C, C++, Java, or VHDL. This list is not exhaustive.

[0063] ​Although the present invention has been described in relation to several specific embodiments, it is clear that the present invention is by no means limited thereto and includes all technical equivalents of the means described, as well as combinations thereof where they fall within the scope of the present invention.

[0064] The use of the verbs "comprise" or "include" and their conjugations does not preclude the existence of any elements or steps other than those described in the claims.

[0065] In the claims, no reference numerals in parentheses shall be construed as limiting the claims.

Claims

1. 1. A computer-implemented method for calculating transition parameters of a liquefied gas storage medium, the storage medium comprising at least one sealed, non-refrigerated tank (2, 4, 5, 6, 7 or 11) equipped with a safety valve (20), the transition parameters characterizing the change of a two-phase mixture (13) contained in the sealed, non-refrigerated tank between an initial state (8) and a final state (9), the two-phase mixture comprising a liquid phase and a gas phase, the transition parameters being defined by a duration τ of the transition, a liquid extraction rate m ｌ and steam extraction speed m ｖ and wherein the method is selected from the group consisting of: - for the liquid and gas phases of the initial state (8), the initial liquid phase temperature T ｌ，ｉ , initial gas phase temperature T ｖ，ｉ , initial gas phase pressure P ｉ , initial liquid phase volume V ｌ，ｉ and the initial liquid phase composition x ｌ，ｉ Based on the initial mass density ρ ｌ，ｉ and ρ ｖ，ｉ and initial internal mass energy U ｌ，ｉ and U ｖ，ｉ determining a - For the liquid and gas phases of the final state (9), the equation of state and the final gas phase pressure P ｆ Based on the final mass density ρ ｌ，ｆ and ρ ｖ，ｆ , final internal mass energy U ｌ，ｆ and U ｖ，ｆ , and the final mass enthalpy H ｌ，ｆ and H ｖ，ｆ determining the final pressure P of the gas phase ｆ is equal to or less than the set pressure of the safety valve (20), and the initial pressure P ｉ the determining step; - calculating said transition parameters using the following formula: [Equation 1] where Q corresponds to the energy contribution due to heat penetration through the tank wall per unit time, and V ｔ corresponds to the total volume of the tank, [Equation 2] and calculating,

2. 1. A computer-implemented method for calculating transition parameters of a liquefied gas storage medium, the storage medium comprising at least one sealed, non-refrigerated tank (2, 4, 5, 6, 7 or 11) equipped with a vacuum shut-off valve (21), the transition parameters characterizing the change of a two-phase mixture (13) contained in the sealed, non-refrigerated tank between an initial state (8) and a final state (9), the two-phase mixture comprising a liquid phase and a gas phase, the transition parameters being defined by a duration of transition τ, a liquid extraction rate m ｌ and steam extraction speed m ｖ and wherein the method is selected from the group consisting of: - for the liquid and gas phases of the initial state (8), the initial liquid phase temperature T ｌ，ｉ , initial gas phase temperature T ｖ，ｉ , initial gas phase pressure P ｉ , initial liquid phase volume V ｌ，ｉ and the initial liquid phase composition x ｌ，ｉ Based on the initial mass density ρ ｌ，ｉ and ρ ｖ，ｉ and initial internal mass energy U ｌ，ｉ and U ｖ，ｉ determining a - For the liquid and gas phases of the final state (9), the equation of state and the final gas phase pressure P ｆ Based on the final mass density ρ ｌ，ｆ and ρ ｖ，ｆ , final internal mass energy U ｌ，ｆ and U ｖ，ｆ , and the final mass enthalpy H ｌ，ｆ and H ｖ，ｆ determining the final pressure P of the gas phase ｆ is equal to or greater than the set pressure of the vacuum shutoff valve (21), and the initial pressure P ｉ a determining step, - calculating said transition parameters using the following formula: [Equation 3] where Q corresponds to the energy contribution due to heat penetration through the tank wall per unit time, and V ｔ corresponds to the total volume of the tank, [Equation 4] and calculating,

3. the storage medium comprises a plurality of tanks (2, 4, 5, 6, 7 and 11), and the initial and final mass densities, the initial and final internal mass energies, and the final mass enthalpies are determined for each tank for the liquid and gas phases, and the transition parameters are calculated using the following equations: [Equation 5] 3. The method according to claim 1, wherein the index j refers to the index of the tank under consideration.

4. The transition parameter is the duration τ of the transition, and the steam extraction rate m ｖ and the liquid extraction rate m ｌ The method of claim 1 or 2, wherein is predetermined.

5. The transition parameter is the steam extraction speed m ｖ and the liquid extraction speed m ｌ The method of claim 1 or 2, wherein the duration of the transition is predetermined.

6. The transition parameter is the liquid extraction rate m ｌ and the steam extraction speed m ｖ The method of claim 1 or 2, wherein the duration of the transition is predetermined.

7. The storage medium comprises at least one level sensor (14) configured to determine the volume of the liquid phase in at least one sealed non-refrigerated tank (2, 4, 5, 6, 7 or 11), and the initial volume V of the liquid phase ｌ，ｉ The method of claim 1 or 2, wherein is determined by the level sensor (14).

8. The storage medium comprises at least one temperature sensor (151 or 152) configured to measure the temperature of the gas phase in at least one sealed non-refrigerated tank (2, 4, 5, 6, 7 or 11) and at least one temperature sensor (153, 154 or 155) configured to measure the temperature of the liquid phase, and the initial temperature T ｖ，ｉ and the initial temperature T of the liquid phase ｌ，ｉ The method according to claim 1 or 2, wherein the temperature is measured by the temperature sensors (151 to 155).

9. The storage medium comprises at least one pressure sensor (16) configured to measure the pressure of the gas phase in at least one sealed non-refrigerated tank (2, 4, 5, 6, 7 or 11), and the initial pressure P of the gas phase ｉ 3. The method according to claim 1, wherein the pressure sensor (16) measures the pressure.

10. The storage medium comprises at least one composition sensor (17) configured to determine the composition of the liquid phase in at least one sealed non-refrigerated tank (2, 4, 5, 6, 7 or 11), and the initial composition x of the liquid phase is ｌ，ｉ The method of claim 1 or 2, wherein is determined by the composition sensor.

11. The storage medium comprises at least one flow sensor configured to measure a vapor extraction mass flow rate (18) or a liquid extraction mass flow rate (19) leaving a sealed non-refrigerated tank (2, 4, 5, 6, 7 or 11), and the liquid extraction rate m ｌ or the steam extraction speed m ｖ 3. The method according to claim 1, wherein the flow rate is determined by the flow sensor (18 or 19).

12. 3. The method of claim 1 or 2, wherein the two-phase mixture (13) is a combustible mixture.

13. 13. The method of claim 12, wherein the combustible mixture is selected from the list consisting of liquefied natural gas, liquefied petroleum gas, and liquefied hydrogen.

14. 13. The method of claim 12, wherein the sealed, non-refrigerated tank is a fuel reservoir for propelling a land, marine, air, or space vehicle.

15. A system (10) for calculating transition parameters of a liquefied gas storage medium characterizing the evolution of a two-phase mixture (13) between an initial state (8) and a final state (9), the transition parameters being defined by the duration of the transition τ, the liquid extraction rate m ｌ and steam extraction speed m ｖ and wherein said system is selected from the group consisting of: a storage medium comprising at least one sealed non-refrigerated tank (2, 4, 5, 6, 7 or 11) containing said two-phase mixture, said two-phase mixture comprising a liquid phase and a gas phase; a computing device (22) configured to implement the method according to claim 1 or 2; a human-machine interface that interacts with said computing device to inform an operator of the calculated transition parameters.

16. 16. A land, sea, air or space vehicle comprising a fuel reservoir for propelling the vehicle and a system according to claim 15 configured to calculate transition parameters of the fuel tank.

17. A non-transitory computer readable medium comprising program instructions that, when executed by an apparatus, cause said apparatus to perform the method of claim 1 or 2.

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