A complex full working condition method for open deck fuel tank evaporation rate determination

Abstract

The application discloses a kind of complex full working condition methods for open deck fuel tank evaporation rate, comprising: when fuel tank is in full working condition state, the fuel tank state data of determination start and determination end is respectively collected by sensor;According to fuel tank state data, LNG liquid density value, gasification latent heat value and LNG steam specific heat value are calculated by empirical formula;According to fuel tank state data and LNG liquid density value, evaporation gas flow is calculated;According to fuel tank state data, evaporation gas flow and LNG liquid density value, determination evaporation rate is calculated;According to evaporation gas flow, gasification latent heat value and LNG steam specific heat value, standard evaporation gas flow is obtained by energy conservation law calculation;Standard evaporation gas flow and LNG standard state data are used to standardize correction determination evaporation rate, and the standard evaporation rate of full working condition fuel tank is obtained.This method can realize accurate determination of open deck fuel tank evaporation rate under complex full working condition.

Description

Technical Field

[0001] This invention relates to the field of liquefied natural gas storage and transportation, and in particular to a method for measuring the evaporation rate of open-air deck fuel tanks under complex all operating conditions. 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, in actual navigation, open-deck fuel tanks face complex and variable operating conditions, which significantly affect the evaporation process of LNG. Existing measurement methods usually assume that the fuel tank is under stable and ideal operating conditions, and that the physical properties of LNG are taken as constants or estimated based on empirical formulas. They fail to fully consider the real-time changes of physical properties under these complex operating conditions, making it difficult to truly reflect the actual evaporation behavior of the fuel tank. Summary of the Invention

[0003] This invention provides a method for measuring the evaporation rate of fuel tanks on open decks under complex operating conditions, in order to overcome the problem that the real-time changes in the physical properties of fuel tanks under complex operating conditions are not fully considered, which makes it difficult to accurately reflect the actual evaporation behavior of fuel tanks.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows: A method for determining the evaporation rate of open-air deck fuel tanks under complex full-operation conditions includes: S1. When the fuel tank is in full operating condition, the fuel tank state data at the beginning of the measurement and the fuel tank state data at the end of the measurement are collected by the sensors respectively. The full operating condition refers to the gas phase supply subsystem being able to operate normally and supplying gas to the user through the compressor, so that the pressure and temperature in the fuel tank change from the start to the end of the measurement. S2. Based on the fuel tank status data, calculate the LNG liquid phase density, latent heat of vaporization, and specific heat of LNG vapor using empirical formulas and by querying the material property table. S3. Calculate the evaporation gas flow rate based on the fuel tank status data and LNG liquid phase density value; The expression for the evaporation gas flow rate is:

[0005] In the formula, 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; The LNG volume at the end of the measurement; 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. Based on the evaporation gas flow rate, latent heat of vaporization, and specific heat of LNG vapor, the standard evaporation gas flow rate is calculated using the law of conservation of energy. The measured evaporation rate is then standardized and corrected using the standard evaporation gas flow rate and LNG standard state data to obtain the standard evaporation rate of the fuel tank under all operating conditions. The expression for the standard evaporation rate of the fuel tank under all operating conditions is:

[0006] In the formula, The standard evaporation rate for a complex, all-condition fuel tank; This refers to the specific heat value of LNG steam. This refers to the standard liquid phase density of LNG. 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; 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; The LNG volume at the end of the measurement; This refers to the total volume of the fuel tank; For fill rate; For measuring time.

[0007] Furthermore, the fuel tank status data includes: average atmospheric temperature, LNG temperature at the start of the measurement, LNG temperature at the end of the measurement, fuel tank pressure at the start of the measurement, fuel tank pressure at the end of the measurement, LNG volume at the start of the measurement, LNG volume at the end of the measurement, measurement time, and sea state.

[0008] Furthermore, the expression for calculating the evaporation rate is as follows:

[0009] In the formula, To determine the evaporation rate; This refers to the evaporation gas flow rate; To determine the initial LNG liquid phase density value; This refers to the total volume of the fuel tank; For fill rate; For measuring time.

[0010] Beneficial effects: This invention provides a method for determining the evaporation rate of fuel tanks on open decks under complex full operating conditions. By collecting multi-source state data, including pressure, temperature, liquid level, and ambient weather, in real time, and dynamically calculating key thermophysical parameters such as liquid phase density, latent heat of vaporization, and specific heat of vapor of LNG under the current operating conditions, it avoids the errors caused by using fixed empirical values ​​in traditional methods, thereby significantly improving the accuracy of the basic evaporation rate calculation. By utilizing thermodynamic parameters such as latent heat of vaporization and specific heat of steam calculated based on measured data, the measured evaporation rate is thermodynamically corrected. This effectively eliminates or compensates for interference caused by complex factors such as drastic fluctuations in the external environment and changes in pressure and temperature inside the fuel tank, ultimately outputting a highly comparable "standard evaporation rate" that truly reflects the insulation performance of the fuel tank itself. This provides unified and reliable benchmark data for fuel tank design optimization, fuel consumption measurement, and configuration of the evaporative gas treatment system. Attached Figure Description

[0011] 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.

[0012] 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.

[0013] 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

[0014] 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.

[0015] This embodiment provides a method for determining the evaporation rate of fuel tanks on open decks under complex, full-operation conditions, such as... Figure 1 As shown, it includes: S1. When the fuel tank is in full operating condition, the fuel tank state data at the beginning of the measurement and the fuel tank state data at the end of the measurement are collected by the sensors respectively. The full operating condition refers to the gas phase supply subsystem being able to operate normally and supplying gas to the user through the compressor, so that the pressure and temperature in the fuel tank change from the start to the end of the measurement. In this embodiment, the fuel tank is in a complex operating condition because the fuel tank is in a state of dynamic imbalance during operation. The conditions for the complex full-operational condition are as follows: 1. The fuel tank is in a partially normal operating condition, and the pressure is maintained within the safety valve set pressure; 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.

[0016] Preferably, the fuel tank status data includes: average atmospheric temperature, LNG temperature at the start of the measurement, LNG temperature at the end of the measurement, fuel tank pressure at the start of the measurement, fuel tank pressure at the end of the measurement, LNG volume at the start of the measurement, LNG volume at the end of the measurement, measurement time, and sea state.

[0017] The specific details of the fuel tank status data are shown in Table 1: Table 1

[0018] In Table 1, the start time of the measurement is indicated by subscript 1, and the end time of the measurement is indicated by subscript 2.

[0019] S2. Based on the fuel tank status data, calculate the LNG liquid phase density, latent heat of vaporization, and specific heat of LNG vapor using empirical formulas and by querying the material property table. Specifically, the LNG liquid phase density value is obtained at the beginning and end of the measurement using the following empirical formula:

[0020] In the formula, The density of the LNG liquid phase; For the first Mole percentage of materials in each LNG component; For the first Molar mass of materials in a LNG component; For the first The density of each LNG liquid phase component at the corresponding temperature can be obtained by looking up the material property table; This represents the total number of types of LNG components. An index for the components of LNG; Substituting the LNG composition at the start of the measurement and the density of the LNG liquid phase component at the corresponding temperature obtained by querying the temperature at the start of the measurement into the empirical formula for the LNG liquid phase density value, the LNG liquid phase density at the start of the measurement is obtained. ; Substituting the LNG component at the end of the measurement and the density of the LNG liquid phase component at the corresponding temperature obtained by querying the temperature at the end of the measurement into the empirical formula for the LNG liquid phase density value, the LNG liquid phase density at the end of the measurement is obtained. ; The material property table mentioned is common knowledge and will not be elaborated here. The latent heat of vaporization is obtained using the following empirical formula:

[0021] In the formula, This refers to the latent heat of vaporization of LNG. For the first The latent heat of vaporization of each LNG component can be obtained by looking up the material property table. The specific calorific value of the LNG steam is obtained using the following empirical formula:

[0022] In the formula, This refers to the specific heat value of LNG steam. For the first Molar percentage of each LNG component in the vapor phase of the evaporated gas; For the first The specific heat value of each LNG component vapor can be obtained by looking up the material property table.

[0023] S3. Calculate the evaporation gas flow rate based on the fuel tank status data and LNG liquid phase density value; The expression for the evaporation gas flow rate is:

[0024] In the formula, 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.

[0025] As another implementation method, the evaporation gas flow rate can also be obtained directly by installing an evaporation gas flow sensor.

[0026] 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:

[0027] In the formula, To determine the evaporation rate; This refers to the evaporation gas flow rate; To determine the initial LNG liquid phase density value; This refers to the total volume of the fuel tank; For fill rate; For measuring time.

[0028] S5. Based on the evaporation gas flow rate, latent heat of vaporization, and specific heat of LNG vapor, the standard evaporation gas flow rate is calculated using the law of conservation of energy. The measured evaporation rate is then standardized and corrected using the standard evaporation gas flow rate and LNG standard state data to obtain the standard evaporation rate of the fuel tank under all operating conditions. The expression for the standard evaporation rate of the fuel tank under all operating conditions is:

[0029] In the formula, The standard evaporation rate for a complex, all-condition fuel tank; This refers to the specific heat value of LNG steam. This refers to the standard liquid phase density of LNG. 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; 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; The LNG volume at the end of the measurement; This refers to the total volume of the fuel tank; For fill rate; For measuring time.

[0030] Specifically, the steps to obtain the standard evaporation gas flow rate are as follows: S51. According to the law of conservation of energy, calculate the total energy transferred into the fuel tank during the measurement period. The expression is:

[0031] In the formula, This represents the total energy transferred into the fuel tank during the measurement period; S52. Convert the total energy transferred to the fuel tank during the measurement period to standard conditions to obtain the standard evaporation gas flow rate, expressed as:

[0032] In the formula, This is the standard evaporation gas flow rate.

[0033] Specifically, the measured evaporation rate is standardized and corrected using standard evaporation gas flow rate and LNG standard state data; The LNG standard condition is a widely accepted benchmark in the LNG shipbuilding industry, including fuel convention of pure methane, standard boiling point of -161.5℃, standard liquid density of 425kg / m³, and standard latent heat of vaporization of 511KJ / kg. The standardized corrections include corrections for evaporation gas flow rate, liquid phase density, temperature, and sea state. The evaporation gas flow rate calibration item is to measure the evaporation gas flow rate in the evaporation rate measurement. Replace with standard evaporation gas flow rate ; 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 calculates a dimensionless correction coefficient for the temperature of the open-deck fuel tank under all operating conditions. This dimensionless correction coefficient is then added to the evaporation rate measurement. The expression for the dimensionless correction coefficient for the temperature of the open-deck fuel tank under all operating conditions 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.

[0034] In this embodiment, a system for measuring the evaporation rate of open-air deck fuel tanks under complex full-operating conditions is proposed, such as... Figure 2 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.

[0035] 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.

[0036] The present invention has the following beneficial effects: This invention provides a method for determining the evaporation rate of fuel tanks on open decks under complex full-condition working conditions. By collecting multi-source state data, including pressure, temperature, liquid level, and ambient weather, in real time, and dynamically calculating key thermophysical parameters such as liquid phase density, latent heat of vaporization, and specific heat of vapor of LNG under the current working conditions, this method avoids the errors caused by using fixed empirical values ​​in traditional methods, thereby significantly improving the accuracy of the basic evaporation rate calculation. By utilizing thermodynamic parameters such as latent heat of vaporization and specific heat of steam calculated based on measured data, the measured evaporation rate is thermodynamically corrected. This effectively eliminates or compensates for interference caused by complex factors such as drastic fluctuations in the external environment and changes in pressure and temperature inside the fuel tank, ultimately outputting a highly comparable "standard evaporation rate" that truly reflects the insulation performance of the fuel tank itself. This provides unified and reliable benchmark data for fuel tank design optimization, fuel consumption measurement, and configuration of the evaporative gas treatment system.

[0037] 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 open decks under complex full-operating conditions, characterized in that, include: S1. When the fuel tank is in full operating condition, the fuel tank state data at the beginning of the measurement and the fuel tank state data at the end of the measurement are collected by the sensors respectively. The full operating condition refers to the gas phase supply subsystem being able to operate normally and supplying gas to the user through the compressor, so that the pressure and temperature in the fuel tank change from the start to the end of the measurement. S2. Based on the fuel tank status data, calculate the LNG liquid phase density, latent heat of vaporization, and specific heat of LNG vapor using empirical formulas and by querying the material property table. S3. Calculate the evaporation gas flow rate based on the fuel tank status data and LNG liquid phase density value; The expression for the evaporation gas flow rate is: In the formula, 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; The LNG volume at the end of the measurement; 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. Based on the evaporation gas flow rate, latent heat of vaporization, and specific heat of LNG vapor, the standard evaporation gas flow rate is calculated using the law of conservation of energy. The measured evaporation rate is then standardized and corrected using the standard evaporation gas flow rate and LNG standard state data to obtain the standard evaporation rate of the fuel tank under all operating conditions. The expression for the standard evaporation rate of the fuel tank under all operating conditions is: In the formula, The standard evaporation rate for a complex, all-condition fuel tank; This refers to the specific heat value of LNG steam. This refers to the standard liquid phase density of LNG. 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; 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; The LNG volume at the end of the measurement; This refers to the total volume of the fuel tank; For fill rate; For measuring time.

2. The method for determining the evaporation rate of fuel tanks on open decks under complex full-operating conditions according to claim 1, characterized in that, The fuel tank status data includes: average atmospheric temperature, LNG temperature at the start of the measurement, LNG temperature at the end of the measurement, fuel tank pressure at the start of the measurement, fuel tank pressure at the end of the measurement, LNG volume at the start of the measurement, LNG volume at the end of the measurement, measurement time, and sea state.

3. The method for determining the evaporation rate of fuel tanks on open decks under complex full-operating conditions 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 evaporation gas flow rate; To determine the initial LNG liquid phase density value; This refers to the total volume of the fuel tank; For fill rate; For measuring time.

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