Method and system for predicting residual lossless storage and transportation time of low-temperature container
By establishing a thermal equilibrium model and using Russian models to correct the lossless storage and transportation time, combined with the high-vacuum multi-layer adiabatic maintenance time equation, the problem of large errors in the prediction of lossless storage and transportation time of low-temperature containers is solved, and the accuracy and safety of the prediction are improved.
Patent Information
- Application Number
- CN202411640919.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-18
- Publication Date
- 2025-03-25
AI Technical Summary
In the prediction of lossless storage and transportation time of low-temperature containers, the prediction time error is large when approaching the start-up pressure of the safety valve, resulting in safety hazards and material losses.
By obtaining the basic parameters of the low-temperature container, a thermal equilibrium model is established to obtain the lossless storage and transportation time under the standard state, and correct it according to the Russian model, combining the high-vacuum multi-layer adiabatic maintenance time equation under the standard state, the remaining lossless storage and transportation time is predicted.
The accuracy of prediction of lossless storage and transportation time of low-temperature containers is improved, especially when approaching the starting pressure of the safety valve, the prediction time is closer to the true value, reducing safety hazards and material losses.
Smart Images
Figure CN119691915A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of low-temperature container storage and transportation time prediction, and in particular to a method and system for predicting the remaining lossless storage and transportation time of a low-temperature container. Background Art
[0002] A cryogenic container is a container for loading cryogenic media (such as LNG, liquid nitrogen, etc.). For a cryogenic container filled at a rated filling rate, the cryogenic medium is very easy to vaporize after absorbing the heat transmitted from the outside. The vaporized gas occupies a limited gas phase space, causing the gas phase pressure of the container to gradually increase. When the pressure reaches the opening pressure of the safety valve, the pressure will be released through the safety valve to discharge the medium vapor (i.e., BOG gas) to the outside environment. The time it takes for the pressure of the container to rise from the ambient atmospheric pressure to the opening of the safety valve, and converted into the time under the standard environment, is the standard lossless storage and transportation time, also known as the maintenance time. If the storage and transportation time of the cryogenic container exceeds its maintenance time, the safety valve will be opened frequently, which will cause material losses on the one hand, and increase potential safety hazards on the other hand, such as affecting the structure of adjacent equipment, causing frostbite to personnel, and causing accidental ignition. Therefore, it is an important technology to accurately monitor the remaining lossless storage and transportation time of the cryogenic container so that corresponding preventive measures can be taken in advance.
[0003] At present, the prediction of the lossless storage and transportation time of cryogenic containers is based on the static daily evaporation rate measured by the test and calculated according to the saturated homogeneous model. The methods used are mainly based on the national standard GB / T 18443.7-2010 "Vacuum Insulation Cryogenic Equipment Performance Test Method Part 7: Maintenance Time Measurement", and some algorithms use the Russian model for correction. However, such methods currently have the problem of large prediction time errors when approaching the safety valve trip pressure. Summary of the invention
[0004] In order to overcome the problems existing in the prior art, the present invention provides a method for monitoring the remaining lossless storage and transportation time of a cryogenic container, comprising: Obtain the basic parameters of the cryogenic container; Establish a heat balance model to obtain the lossless storage and transportation time under standard conditions; According to the Russian model, the lossless storage and transportation time under the standard state is corrected to obtain the corrected lossless storage and transportation time; Based on the modified lossless storage and transportation time and the high vacuum multi-layer insulation maintenance time equation under standard conditions, the remaining lossless storage and transportation time is predicted.
[0005] Furthermore, the basic parameters of the low-temperature container include container volume, medium filling rate, medium static daily evaporation rate, initial pressure in the container, safety valve set pressure, liquid medium density, gas medium density, latent heat of vaporization, saturation pressure, saturation temperature, and saturated gas-liquid internal energy value.
[0006] Furthermore, the heat balance model includes cumulative heat transfer and daily heat transfer. The cumulative heat transfer is, ; in, Q is the cumulative heat transfer, U 21 and U 22 are the thermodynamic energies of gas and liquid at the end, U 11 and U 12 are the initial thermodynamic energies of gas and liquid respectively; Daily heat transfer Q d for, ; in, m is the filling mass of the container, α is the static daily evaporation rate, r 1 is the latent heat of vaporization of the initial liquid saturated vapor, r 2 is the latent heat of vaporization of the initial liquid saturated vapor; The lossless storage and transportation time under the standard state is: ; in, t It is the lossless storage and transportation time under standard conditions.
[0007] Furthermore, the lossless storage and transportation time under the standard state is corrected according to the Russian model, and the corrected lossless storage and transportation time is obtained as follows: The dimensionless time is obtained according to the Russian model, and the ratio of the lossless storage and transportation time to the dimensionless time is used as the corrected lossless storage and transportation time.
[0008] Furthermore, the Russian model is: ; ; ; in, t ' is dimensionless time, p ' is the dimensionless pressure, p is the final state equipment pressure, p cr is the critical pressure, p 0 is the initial pressure, f is the medium filling rate, φ is the dimensionless leakage heat flux, α is the static daily evaporation rate, γ is the latent heat of vaporization of the medium at an absolute pressure of 0.1 MPa, c is the specific heat capacity of the initial liquid, T is the initial temperature.
[0009] Furthermore, the high vacuum multi-layer insulation maintenance time equation under the standard state is specifically: ; in, t e For the corrected lossless storage and transportation time, t 0 The remaining lossless storage and transportation time, T 1 To estimate the average ambient temperature, T 2 is the average pressure in the container corresponding to the saturation temperature of the medium, T s It is the saturation temperature of the low-temperature medium under standard atmospheric pressure.
[0010] The present invention also provides a system for predicting the remaining lossless storage and transportation time of a cryogenic container, comprising: A parameter acquisition module is used to obtain basic parameters of the cryogenic container; Thermal balance determination module, establishes a thermal balance model to obtain lossless storage and transportation time under standard conditions; A correction module is used to correct the lossless storage and transportation time under the standard state according to the Russian model to obtain the corrected lossless storage and transportation time; The prediction module is used to predict the remaining lossless storage and transportation time based on the modified lossless storage and transportation time and the high vacuum multi-layer insulation maintenance time equation under standard conditions.
[0011] The present invention also provides a computer-readable medium storing an executable program, wherein the executable program performs the above method when executed.
[0012] Compared with the prior art, the present invention has the following beneficial effects: The method for predicting the remaining lossless storage and transportation time of a cryogenic container provided by the present invention is convenient, highly accurate and effective. At the same time, compared with the single Russian model and the high vacuum multi-layer insulation maintenance time equation under standard conditions, the predicted time of the present invention is closer to the true value when approaching the safety valve trip pressure, which is convenient for taking corresponding preventive measures in advance and has good engineering practice significance. BRIEF DESCRIPTION OF THE DRAWINGS
[0013] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0014] Figure 1 A schematic diagram of the structure of a low-temperature container monitoring system is shown; Figure 2 A flow chart showing the method for predicting the remaining lossless storage and transportation time of a cryogenic container according to Example 1 is shown; Figure 3 A comparison chart of the remaining lossless storage and transportation time predicted by Example 1, Comparative Example 1, and Comparative Example 2 is shown; Figure 4 A schematic diagram showing the structure of a system for predicting the remaining lossless storage and transportation time of a cryogenic container according to Example 2 is shown; Description of reference numerals: 10. Cryogenic container; 101. Inner container; 102. Insulation material; 103. Outer shell; 20. Pressure gauge; 30. Safety valve; 40. Remote monitoring component. DETAILED DESCRIPTION
[0015] The following will be combined with the specific embodiments of the present invention and the drawings of the specification to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0016] Example 1 like Figure 1As shown, this embodiment is based on a conventional cryogenic container monitoring system, which includes a cryogenic container 10, and a pressure gauge 20 and a remote monitoring component 40 connected to the cryogenic container 10 in sequence. A safety valve 30 is also provided between the cryogenic container 10 and the pressure gauge 20. The cryogenic container 10 includes an inner container 101, an insulating material 102 and an outer shell 103 from the inside to the outside. Among them, the inner container 101 is a pressure vessel, which contains low-temperature medium and is made of stainless steel; the insulating material 102 is composed of alternating layers of radiation screens with high reflectivity and spacers with low thermal conductivity, which are coated on the outer surface of the inner container 101 to play an insulating role; the safety valve 30 is used to ensure the safety of the low-temperature container 10 under extreme working conditions; the pressure gauge 20 is used to monitor the pressure value of the inner container 101 in real time; the remote monitoring component 40 is used to obtain the data of the pressure gauge 20 and the basic parameters of the inner container 101, and can also issue an early warning signal. The remote monitoring component 40 can update the running program according to the remote instructions issued by the receiving end, and can adjust the data upload cycle during operation, and send the monitored parameters and the box number and location of the low-temperature container 10 to the receiving end for personnel observation.
[0017] This embodiment also provides a method for predicting the remaining lossless storage and transportation time of a cryogenic container. Figure 2 As shown, it includes the following steps: S101. Obtain basic parameters of the cryogenic container.
[0018] These basic parameters include, container volume V (m 3 ), medium filling rate f (%), medium static daily evaporation rate α (% / d), the initial pressure in the container is P o (MPa), safety valve set pressure P s (MPa), P o and P s Select the appropriate container saturation pressure point to reflect the pressure increase process. Each saturation pressure, saturation temperature, medium physical properties, and saturated gas-liquid internal energy value of the cryogenic liquid are one-to-one corresponding. Consult the data to obtain the liquid medium density and gas medium density under different pressures. ρ (kg / m 3 ), latent heat of vaporization r (kJ / kg) and so on.
[0019] S102. Establish a heat balance model to obtain lossless storage and transportation time under standard conditions.
[0020] The heat balance model includes cumulative heat transfer and daily heat transfer. The cumulative heat transfer is, ; in, Q is the cumulative heat transfer, U 21 and U 22 are the thermodynamic energies of gas and liquid at the end, U 11 and U 12 are the initial thermodynamic energies of gas and liquid, Q , U 21 , U 22 , U 21 and U 22 The unit is kJ.
[0021] Daily heat transfer Q d for, ; in, m is the filling mass of the container (kg), α is the static daily evaporation rate (% / d), r 1 is the latent heat of vaporization of the initial liquid saturated vapor (kJ / kg), r 2 is the latent heat of vaporization of the initial liquid saturated vapor (kJ / kg); The lossless storage and transportation time under the standard state is: ; in, t is the lossless storage and transportation time under standard conditions (days).
[0022] S103. Correct the lossless storage and transportation time under the standard state according to the Russian model to obtain a corrected lossless storage and transportation time.
[0023] The Russian model is modified as follows: ; ; ; in, t ' is dimensionless time, p ' is the dimensionless pressure (MPa), p is the final equipment pressure (MPa), p cr is the critical pressure (MPa), p 0is the initial pressure (MPa), f is the medium filling rate (%), φ is the dimensionless leakage heat flux, α is the static daily evaporation rate, γ is the latent heat of vaporization of the medium at an absolute pressure of 0.1 MPa (kJ / kg), c is the specific heat capacity of the initial liquid (kJ·kg -1 ·K -1 ), T is the initial temperature (K).
[0024] According to the Russian model, the dimensionless time is obtained, and the ratio of the lossless storage and transportation time to the dimensionless time is used as the corrected lossless storage and transportation time, that is, ; in, t e It is the corrected lossless storage and transportation time.
[0025] S104. Predict the remaining lossless storage and transportation time based on the corrected lossless storage and transportation time and the high vacuum multi-layer insulation maintenance time equation under standard conditions.
[0026] The specific equation for maintaining high vacuum multi-layer insulation time under standard state is: ; in, t e is the corrected loss-free storage and transportation time (days), t 0 is the remaining lossless storage and transportation time (days), T 1 To estimate the average ambient temperature (K), T 2 is the average pressure in the container corresponding to the saturation temperature of the medium (K), T s It is the saturation temperature of the low-temperature medium under standard atmospheric pressure (K).
[0027] According to the region and season where the cryogenic container is transported, the T 1 ; According to the pressure in the container measured by the pressure gauge and the medium stored in the container, you can obtain T 2 ; According to the above formula, it can be calculated by modifying the Russian model t e Calculate the predicted maintenance time of the cryogenic container in the current state t 0 It can also be seen that, in this embodiment, the remaining lossless storage and transportation time of the low-temperature container can be obtained based on the pressure in the container and by consulting the existing data.
[0028] Comparative Example 1 The calculation formula for the high vacuum multilayer insulation maintenance time under the standard state in the national standard GB / T 18443.7-2010 "Vacuum insulation cryogenic equipment performance test method Part 7: Maintenance time measurement" is: ; in, H 20 is the maintenance time under standard state (days), H 0 Maintenance time for the test (days), T 1 To estimate the average ambient temperature (K), T 2 is the average pressure in the container corresponding to the saturation temperature of the medium (K), T s It is the saturation temperature of the low-temperature medium under standard atmospheric pressure (K).
[0029] Calculated H 20 The result is taken as the remaining damage-free storage and transportation time of the cryogenic container.
[0030] Comparative Example 2 The remaining lossless storage and transportation time of the cryogenic container is obtained by using the Russian model to modify the prediction algorithm. The specific Russian model can be referred to in the embodiment, which will not be described in detail here.
[0031] By collecting LNG tank data in the plant area, the remaining lossless storage and transportation time prediction algorithm was compared and analyzed. The tank filling medium is LNG, the filling rate is 90%, and the safety valve trip pressure is 0.64Mpa. The remaining lossless storage and transportation time was predicted according to the methods of the embodiment, comparative example 1 and comparative example 2, and the results are as follows: Figure 3 As shown. It can be seen that when the pressure is relatively low, the prediction curves obtained by the three algorithms have relatively large errors; as the pressure rises, the prediction curve of the embodiment gradually decreases in error compared with the test curve, and the closer to the take-off pressure, the smaller the error. On the other hand, the predicted number of days in the embodiment is more conservative and more in line with actual transportation safety requirements. These results show that the monitoring method for the remaining lossless storage and transportation time of low-temperature containers provided by the present invention has the characteristics of high accuracy and good effect compared with the single Russian model and the national standard calculation method, which is convenient for taking corresponding preventive measures in advance and has good engineering practice significance. On the whole, the present invention can dynamically adjust the LNG density parameters according to the collected medium temperature, more accurately calculate the refilling status of the tank medium, and timely report the warning information according to the safety valve take-off pressure when the pressure in the container and the predicted number of days reach the warning value.
[0032] Example 2 A system for predicting the remaining lossless storage and transportation time of cryogenic containers, such as Figure 4 As shown, including A parameter acquisition module is used to obtain basic parameters of the cryogenic container; Thermal balance determination module, establishes a thermal balance model to obtain lossless storage and transportation time under standard conditions; A correction module is used to correct the lossless storage and transportation time under the standard state according to the Russian model to obtain the corrected lossless storage and transportation time; The prediction module is used to predict the remaining lossless storage and transportation time based on the modified lossless storage and transportation time and the high vacuum multi-layer insulation maintenance time equation under standard conditions.
[0033] The specific module execution process in this embodiment has been described in detail in the corresponding invention embodiment, and will not be repeated in this embodiment.
[0034] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.
Claims
1. A method for predicting the remaining lossless storage and transportation time of a cryogenic container, characterized in that: include, Obtain the basic parameters of the cryogenic container; Establish a heat balance model to obtain the lossless storage and transportation time under standard conditions; According to the Russian model, the lossless storage and transportation time under the standard state is corrected to obtain the corrected lossless storage and transportation time; Based on the modified lossless storage and transportation time and the high vacuum multi-layer insulation maintenance time equation under standard conditions, the remaining lossless storage and transportation time is predicted.
2. The method for predicting the remaining lossless storage and transportation time of a cryogenic container according to claim 1, characterized in that: The basic parameters of the cryogenic container include container volume, medium filling rate, medium static daily evaporation rate, initial pressure in the container, safety valve set pressure, liquid medium density, gas medium density, latent heat of vaporization, saturation pressure, saturation temperature, and saturated gas-liquid internal energy value.
3. The method for predicting the remaining lossless storage and transportation time of a cryogenic container according to claim 1, characterized in that: The heat balance model includes cumulative heat transfer and daily heat transfer. The cumulative heat transfer is, ； in, Q is the cumulative heat transfer, U 21 and U 22 are the thermodynamic energies of gas and liquid at the end, U 11 and U 12 are the initial thermodynamic energies of gas and liquid respectively; Daily heat transfer Q d for, ； in, m is the filling mass of the container, α is the static daily evaporation rate, r 1 is the latent heat of vaporization of the initial liquid saturated vapor, r 2 is the latent heat of vaporization of the initial liquid saturated vapor; The lossless storage and transportation time under the standard state is: ； in, t It is the lossless storage and transportation time under standard conditions.
4. The method for predicting the remaining lossless storage and transportation time of a cryogenic container according to claim 1, characterized in that: The lossless storage and transportation time under the standard state is corrected according to the Russian model, and the corrected lossless storage and transportation time is obtained as follows: The dimensionless time is obtained according to the Russian model, and the ratio of the lossless storage and transportation time to the dimensionless time is used as the corrected lossless storage and transportation time.
5. The method for predicting the remaining lossless storage and transportation time of a cryogenic container according to claim 1, characterized in that: The Russian model is, ； ； ； in, t ' is dimensionless time, p ' is the dimensionless pressure, p is the final state equipment pressure, p cr is the critical pressure, p 0 is the initial pressure, f is the medium filling rate, φ is the dimensionless leakage heat flux, α is the static daily evaporation rate, γ is the latent heat of vaporization of the medium at an absolute pressure of 0.1 MPa, c is the specific heat capacity of the initial liquid, T is the initial temperature.
6. The method for predicting the remaining lossless storage and transportation time of a cryogenic container according to claim 1, characterized in that: The high vacuum multi-layer insulation maintenance time equation under the standard state is specifically: ； in, t e For the corrected lossless storage and transportation time, t 0 is the remaining lossless storage and transportation time, T 1 is the estimated average ambient temperature. T 2 is the average pressure in the container corresponding to the saturation temperature of the medium, T s It is the saturation temperature of the low-temperature medium under standard atmospheric pressure.
7. A system for predicting the remaining lossless storage and transportation time of cryogenic containers, characterized in that: include, A parameter acquisition module is used to obtain basic parameters of the cryogenic container; Thermal balance determination module, establishes a thermal balance model to obtain lossless storage and transportation time under standard conditions; A correction module is used to correct the lossless storage and transportation time under the standard state according to the Russian model to obtain the corrected lossless storage and transportation time; The prediction module is used to predict the remaining lossless storage and transportation time based on the modified lossless storage and transportation time and the high vacuum multi-layer insulation maintenance time equation under standard conditions.
8. A computer-readable medium storing an executable program, characterized in that: When the executable program is executed, the method according to any one of claims 1 to 6 is implemented.