A method for determining the evaporation rate of fuel tanks on deck and in enclosures

Abstract

The application discloses a kind of for deck and sheltered place fuel tank evaporation rate determination method, comprising: when fuel tank is in stable working condition state, fuel tank state data at determination start and end is respectively collected by sensor;According to fuel tank state data, obtain LNG liquid density value and latent heat of vaporization value by inquiring material attribute manual;According to fuel tank state data and LNG liquid density value, calculate evaporation gas flow;According to fuel tank state data, evaporation gas flow and LNG liquid density value, calculate determination evaporation rate;Through LNG standard state, the determination evaporation rate is standardized correction, obtains the standard evaporation rate of open deck fuel tank under stable working condition;Through LNG standard state, the determination evaporation rate is standardized correction by combining sheltered place temperature data, obtains the standard evaporation rate of sheltered place fuel tank under stable working condition.The method can adapt to the evaporation rate determination of deck fuel tank of different arrangement forms, effectively improve the accuracy and universality of determination result.

Description

Technical Field

[0001] This invention relates to the field of liquefied natural gas storage and transportation, and more particularly to a method for measuring the evaporation rate of fuel tanks on decks and in enclosed spaces. Background Technology

[0002] Liquefied natural gas (LNG) is a clean and efficient energy source widely used in the field of marine fuel; the LNG evaporation rate (BOR) is an important parameter that must be considered during the construction and delivery of gas fuel-powered ships and gas carriers; accurate LNG fuel tank evaporation rate is crucial for ship fuel consumption management, voyage planning, and BOG handling system design. In recent years, the methods for measuring and calculating the evaporation rate of LNG fuel tanks have not been fully studied, lacking effective experience and data support, and no standard measurement and correction methods have been formed in the industry. Moreover, the existing measurement methods have not fully distinguished and considered the impact of differences in the external thermal environment caused by different fuel tank locations on the measurement of evaporation rate. Summary of the Invention

[0003] This invention provides a method for measuring the evaporation rate of fuel tanks on decks and in enclosed spaces, overcoming the difficulty in forming a standard measurement and correction method due to the lack of effective experience and data support, and also failing to fully consider the impact of the environment of fuel tanks in different locations on the evaporation rate measurement.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows: A method for determining the evaporation rate of fuel tanks on decks and in enclosed spaces, comprising: S1. The compressor flow rate is adjusted by the gas phase supply subsystem to maintain the pressure in the fuel tank without change from the start to the end of the measurement, so that the corresponding temperature is also constant. When the fuel tank is in a stable operating condition, the fuel tank state data at the start of the measurement and the fuel tank state data at the end of the measurement are collected by the sensors respectively. The fuel tank status data includes open deck fuel tank status data and enclosed space fuel tank status data; S2. Based on the fuel tank status data, obtain the LNG liquid phase density value and latent heat of vaporization value by consulting the material property manual; S3. Calculate the evaporation gas flow rate based on the fuel tank status data and LNG liquid phase density value; S4. Calculate and determine the evaporation rate based on the fuel tank status data, evaporation gas flow rate, and LNG liquid phase density value; S5. By standardizing and correcting the measured evaporation rate under LNG standard conditions, the standard evaporation rate of the open deck fuel tank under stable operating conditions is obtained. The expression for the standard evaporation rate of the open-air deck fuel tank under steady operating conditions is as follows:

[0005] In the formula, The standard evaporation rate for open-deck fuel tanks; LNG density; This refers to the latent heat of vaporization. This refers to the standard latent heat value of LNG. To determine the initial LNG temperature; To determine the LNG temperature at the end of the measurement; The average atmospheric temperature; To determine sea state; This refers to the evaporation gas flow rate; This refers to the total volume of the fuel tank; For fuel fill rate; For measuring time; S6. By using LNG standard conditions and combining the temperature data of the enclosed space, the measured evaporation rate is standardized and corrected to obtain the standard evaporation rate of the fuel tank in the enclosed space under stable operating conditions. The expression for the standard evaporation rate of the fuel tank in the enclosed space under steady operating conditions is as follows:

[0006] In the formula, Standard evaporation rate for fuel tanks in enclosed spaces; To measure the temperature of the enclosed area during the measurement period; The design is based on the theoretical temperature of the enclosed space.

[0007] Furthermore, the expression for the evaporation gas flow rate is:

[0008] In the formula, This refers to the evaporation gas flow rate; To determine the initial LNG liquid phase density value; The LNG liquid phase density value at the end of the measurement; To determine the initial LNG volume; This represents the LNG volume at the end of the measurement.

[0009] Furthermore, the expression for calculating the evaporation rate is as follows:

[0010] In the formula, To determine the evaporation rate; This refers to the total volume of the fuel tank; For fuel fill rate; For measuring time.

[0011] Beneficial effects: The present invention provides a method for measuring the evaporation rate of fuel tanks on decks and in enclosed spaces. By ensuring that the fuel tank is in a stable operating condition and collecting real-time status data and basic LNG parameters, reliable basic data is provided for evaporation rate calculation. At the same time, the liquid phase density and latent heat of vaporization of LNG are calculated separately, which accurately reflects the physical properties of the fuel, thereby significantly improving the accuracy of evaporation rate measurement. For different installation locations of the fuel tank, the system is corrected using either ambient temperature or fuel tank temperature, eliminating the influence of environmental differences on the evaporation rate. It can be flexibly applied to various ship deck arrangements and has strong versatility and adaptability. By correcting the measured evaporation rate, the evaporation rate under standard conditions is obtained, providing a unified and reliable reference for fuel management, energy consumption analysis, and ship design. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a schematic flowchart of the evaporation rate determination method of the present invention; Figure 2 This is a schematic diagram of the evaporation rate measurement system for the open-air deck fuel tank in this embodiment; Figure 3 This is a schematic diagram of the evaporation rate measurement system for the enclosed deck fuel tank in this embodiment.

[0014] In the diagram, 1. Fuel tank; 11. Tank body; 12. Pressure sensor; 13. Temperature sensor; 14. Liquid level sensor; 2. Liquid phase fuel supply subsystem; 21. Fuel pump; 22. Liquid phase ESD remote control valve; 23. Liquid phase supply pipe; 24. Evaporator heater; 25. Forced evaporation gas phase pipe; 3. Gas phase fuel supply subsystem; 31. Gas phase ESD remote control valve; 32. Gas phase supply pipe; 33. Evaporation gas flow meter. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] This embodiment provides a method for determining the evaporation rate of fuel tanks on decks and in enclosed spaces, such as... Figure 1 As shown, it includes: S1. The compressor flow rate is adjusted through the gas phase supply subsystem to maintain the pressure in the fuel tank unchanged from the start to the end of the measurement. ), so that the corresponding temperature is also constant ( When the fuel tank is in a stable operating condition, the fuel tank state data at the beginning of the measurement and at the end of the measurement are collected by sensors respectively. The fuel tank status data includes open deck fuel tank status data and enclosed space fuel tank status data; In this embodiment, the fuel tank operates under stable conditions because the fuel tank is actively controlled to be locked at a thermodynamic static equilibrium point.

[0017] The stable operating condition in this embodiment also includes the following conditions: 1. The fuel tank remains in a stable state, with no significant temperature changes in the surrounding area; 2. The liquid phase supply subsystem and related equipment are shut down, and all liquid phase valves are closed; 3. The fuel tank instrument monitoring and safety control system is functioning normally; Data collection was conducted based on the following conditions: Ambient air temperature 45℃; Seawater temperature 32℃; Fuel reference temperature -161.5℃; Fuel composition: pure methane; Fuel fill rate : 98% or a specified value; fuel standard density 425 kg / m³; Standard latent heat value of fuel 511 kJ / kg.

[0018] Specifically, the status data of the open deck fuel tanks are shown in Table 1: Table 1

[0019] The status data of the fuel tanks in the enclosed areas are shown in Table 2: Table 2

[0020] In Tables 1 and 2, the start time of the measurement is indicated by subscript 1, and the end time of the measurement is indicated by subscript 2.

[0021] S2. Based on the fuel tank status data, obtain the LNG liquid phase density value and latent heat of vaporization value by consulting the material property manual; In this embodiment, the material property manual is existing general knowledge information and will not be described in detail here.

[0022] S3. Calculate the evaporation gas flow rate based on the fuel tank status data and LNG liquid phase density value; Preferably, the expression for the evaporation gas flow rate is:

[0023] In the formula, This refers to the evaporation gas flow rate; To determine the initial LNG liquid phase density value; The LNG liquid phase density value at the end of the measurement; To determine the initial LNG volume; This represents the LNG volume at the end of the measurement.

[0024] As another implementation method, the evaporation gas flow rate can also be obtained directly by installing an evaporation gas flow sensor.

[0025] S4. Calculate and determine the evaporation rate based on the fuel tank status data, evaporation gas flow rate, and LNG liquid phase density value; Preferably, the expression for calculating the evaporation rate is:

[0026] In the formula, To determine the evaporation rate; This refers to the total volume of the fuel tank; For fuel fill rate; For measuring time.

[0027] S5. By standardizing and correcting the measured evaporation rate under LNG standard conditions, the standard evaporation rate of the open deck fuel tank under stable operating conditions is obtained. The expression for the standard evaporation rate of the open-air deck fuel tank under steady operating conditions is as follows:

[0028] In the formula, The standard evaporation rate for an open deck; LNG density; This refers to the latent heat of vaporization. This refers to the standard latent heat value of LNG. To determine the initial LNG temperature; To determine the LNG temperature at the end of the measurement; The average atmospheric temperature; To determine sea state; This refers to the evaporation gas flow rate; This refers to the total volume of the fuel tank; For fuel fill rate; For measuring time.

[0029] Specifically, the LNG standard condition is the widely accepted benchmark in the LNG shipbuilding industry, including fuel convention of pure methane, boiling point of -161.5℃, liquid phase density of 425kg / m³, and latent heat of vaporization of 511KJ / kg; Based on the standard conditions of LNG, the measured evaporation rate is corrected to the standard conditions of the fuel; the correction terms include latent heat correction, liquid phase density correction, temperature correction, and sea state correction. The latent heat correction term is to adjust the latent heat value of vaporization. Revised to standard latent heat value of fuel It is added to the evaporation rate measurement to eliminate the influence of latent heat differences under the measurement pressure; The liquid phase density correction term is used to adjust the LNG liquid phase density in the evaporation rate measurement. Replace with LNG standard liquid phase density ; The temperature correction term is calculated using a temperature correction formula based on the LNG temperature at the start and end of the measurement, and the ambient temperature. This formula yields a dimensionless correction coefficient for the open-deck fuel tank temperature, which is then added to the evaporation rate measurement. The expression for the dimensionless correction coefficient for the open-deck fuel tank temperature is as follows: This is used to compensate for the influence of actual LNG temperature and ambient temperature on the evaporation driving force. The sea state correction item adds a standard sea state to the evaporation rate measurement. The standard sea state is... Among them, measuring sea state It is a dimensionless correction coefficient. This represents calm sea conditions (baseline conditions). The more severe the sea conditions (larger waves), the greater the convective heat transfer between the ship and the seawater / air, and the higher the evaporation rate. Therefore, the measured value needs to be divided by [the value]. To correct the value to that under calm sea conditions.

[0030] S6. By using LNG standard conditions and combining the temperature data of the enclosed space, the measured evaporation rate is standardized and corrected to obtain the standard evaporation rate of the fuel tank in the enclosed space under stable operating conditions. The expression for the standard evaporation rate of the fuel tank in the enclosed space under steady operating conditions is as follows:

[0031] In the formula, Standard evaporation rate for fuel tanks in enclosed spaces; To measure the temperature of the enclosed area during the measurement period; The design is based on the theoretical temperature of the enclosed space.

[0032] Specifically, the temperature correction term in the standard evaporation rate of the enclosed space fuel tank is calculated using a temperature correction formula based on the LNG temperature at the start and end of the measurement, the enclosed space temperature during the measurement, and the theoretically designed enclosed space temperature. This formula yields a dimensionless correction coefficient for the enclosed space fuel tank temperature, which is then added to the measured evaporation rate. The expression for the dimensionless correction coefficient for the enclosed space temperature is as follows: .

[0033] In this embodiment, a system for measuring the evaporation rate of deck fuel tanks is proposed, such as... Figure 2 and Figure 3 As shown, it includes: a fuel tank 1, a liquid phase fuel supply subsystem 2 connected to the fuel tank 1, and a gas phase fuel supply subsystem 3; The fuel tank 1 includes a tank body 11, and a pressure sensor 12, a temperature sensor 13 and a liquid level sensor 14 disposed on the tank body 11; The liquid phase fuel supply subsystem 2 includes a fuel pump 21, a liquid phase ESD remote control valve 22, a liquid phase supply pipe 23, an evaporator heater 24, and a forced evaporation vapor phase pipe 25. The fuel pump 21 is mounted on the cabin 11 and is connected to the inlet of the evaporator heater 24 via the liquid phase supply pipe 23. The liquid phase ESD remote control valve 22 is mounted on the liquid phase supply pipe 23. One end of the forced evaporation vapor phase pipe 25 is connected to the outlet of the evaporator heater 24, and the other end is used to connect to the main valve of the gas-using equipment. The gas phase fuel supply subsystem 3 includes a gas phase ESD remote control valve 31 and a gas phase supply pipe 32; one end of the gas phase supply pipe 32 is connected to the gas phase space of the cabin 11, and the other end is used to connect to the main valve of the gas-using equipment; the gas phase ESD remote control valve 31 is installed on the gas phase supply pipe 32. The gas phase fuel supply subsystem 3 may optionally be equipped with an evaporation gas flow meter 33 for measuring the evaporation gas flow rate.

[0034] The present invention has the following beneficial effects: This invention provides a method for measuring the evaporation rate of fuel tanks on decks and in enclosed spaces. By ensuring that the fuel tank is in a stable operating condition and collecting real-time status data and basic LNG parameters, reliable basic data is provided for evaporation rate calculation. At the same time, the liquid phase density and latent heat of vaporization of LNG are calculated separately, which accurately reflects the physical properties of the fuel, thereby significantly improving the accuracy of evaporation rate measurement. For different installation locations of the fuel tank, the system is corrected using either ambient temperature or fuel tank temperature, eliminating the influence of environmental differences on the evaporation rate. It can be flexibly applied to various ship deck arrangements and has strong versatility and adaptability. By correcting the measured evaporation rate, the evaporation rate under standard conditions is obtained, providing a unified and reliable reference for fuel management, energy consumption analysis, and ship design.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for determining the evaporation rate of fuel tanks on decks and in enclosed spaces, characterized in that, include: S1. The compressor flow rate is adjusted by the gas phase supply subsystem to maintain the pressure in the fuel tank without change from the start to the end of the measurement, so that the corresponding temperature is also constant. When the fuel tank is in a stable operating condition, the fuel tank state data at the start of the measurement and the fuel tank state data at the end of the measurement are collected by the sensors respectively. The fuel tank status data includes open deck fuel tank status data and enclosed space fuel tank status data; S2. Based on the fuel tank status data, obtain the LNG liquid phase density value and latent heat of vaporization value by consulting the material property manual; S3. Calculate the evaporation gas flow rate based on the fuel tank status data and LNG liquid phase density value; S4. Calculate and determine the evaporation rate based on the fuel tank status data, evaporation gas flow rate, and LNG liquid phase density value; S5. By standardizing and correcting the measured evaporation rate under LNG standard conditions, the standard evaporation rate of the open deck fuel tank under stable operating conditions is obtained. The expression for the standard evaporation rate of the open-air deck fuel tank under steady operating conditions is as follows: In the formula, The standard evaporation rate for open-deck fuel tanks; LNG density; This refers to the latent heat of vaporization. This refers to the standard latent heat value of LNG. To determine the initial LNG temperature; To determine the LNG temperature at the end of the measurement; The average atmospheric temperature; To determine sea state; This refers to the evaporation gas flow rate; This refers to the total volume of the fuel tank; For fuel fill rate; For measuring time; S6. By using LNG standard conditions and combining the temperature data of the enclosed space, the measured evaporation rate is standardized and corrected to obtain the standard evaporation rate of the fuel tank in the enclosed space under stable operating conditions. The expression for the standard evaporation rate of the fuel tank in the enclosed space under steady operating conditions is as follows: In the formula, Standard evaporation rate for fuel tanks in enclosed spaces; To measure the temperature of the enclosed area during the measurement period; The design is based on the theoretical temperature of the enclosed space.

2. The method for determining the evaporation rate of fuel tanks on decks and in enclosed spaces according to claim 1, characterized in that, The expression for the evaporation gas flow rate is: In the formula, This refers to the evaporation gas flow rate; To determine the initial LNG liquid phase density value; The LNG liquid phase density value at the end of the measurement; To determine the initial LNG volume; This represents the LNG volume at the end of the measurement.

3. The method for determining the evaporation rate of fuel tanks on decks and in enclosed spaces according to claim 2, characterized in that, The expression for calculating the evaporation rate is: In the formula, To determine the evaporation rate; This refers to the total volume of the fuel tank; For fuel fill rate; For measuring time.

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