Method and device for predicting condensation rate in gas-liquid parallel flow process of liquefied natural gas after-condenser

Abstract

The invention discloses a liquefied natural gas recondenser gas-liquid parallel flow process condensation rate prediction method and device. The method comprises the steps that structure parameters and actual operation condition parameters of a recondenser are obtained to form an original database; analyzing influence factors of the condensation rate, and performing normalization and dimensionless processing on the influence factors to obtain standard influence factors; according to a typical physical process in the after-condenser, constructing a correlation between the standard influence factors and the condensation rate in a zoning manner, and fitting undetermined parameters in the correlation to determine an expression of the undetermined parameters; and determining an empirical correlation formula of the recondenser according to the expression of the to-be-determined parameters so as to predict the condensation rate of the recondenser. The problem that design of an existing recondenser structure and working conditions lacks theoretical guidance is solved, then the recondensation process of a liquefied natural gas receiving station is guided to conduct reasonable flow regulation and control, BOG at an outlet is completely condensed, and safety of a natural gas pipeline network is guaranteed.

Description

Technical Field

[0001] The present application relates to the technical field of liquefied natural gas, and in particular to a method and device for predicting the condensation rate of a gas-liquid co-flow process of a liquefied natural gas recondenser. Background Art

[0002] Natural gas accounts for an increasingly high proportion of my country's energy. During the storage and transportation of liquefied natural gas (LNG) in LNG receiving stations, a large amount of superheated boil-off gas (BOG) will be generated due to heat leakage. In order to achieve energy recovery and utilization, LNG receiving stations generally adopt the recondensation process, which uses the supercooling of LNG to condense and recover the gas phase BOG. ​​The LNG recondenser (recondenser) is the core component of the recondensation process, which plays a role of condensation and buffering in the process system.

[0003] The recondenser is a large tower equipment, which is mainly composed of a head, a cylinder, a bottom cover, a gas-liquid distribution plate, a liquid distribution pipe and a random packing. The gas phase BOG enters the tower from the upper part of the recondenser, and enters the packing layer area after passing through the baffle and the gas-liquid distribution plate; the liquid phase LNG enters the tower from one side, and enters the packing layer after being distributed through the liquid distribution pipe and the gas-liquid distribution plate. The packing layer is formed by a random pile of DN50 Raschig rings (or other new packings). The condensation process is enhanced by increasing the specific surface area. The gas and liquid phases in the packing layer flow in parallel and directly contact and condense, which is the core area of ​​the condensation process of the recondenser. The mixed working fluid is finally condensed into LNG, which flows out from the lower outlet and is passed to the rear compressor for pressurized output to the pipeline network. According to the different flow condensation stages in the recondenser, the whole can be divided into the upper area, the packing layer area (middle area), and the lower area.

[0004] The working performance of the recondenser affects the stable and safe operation of the entire system. For different flow conditions, the gas phase BOG must be completely condensed. The overall size of the recondenser is 10m high and 2.5m in diameter. The internal structure is complex, including a variety of tower internals including gas-liquid distribution plates and liquid distribution pipes; the operating pressure range is 0.7~0.8Mpa and the temperature is -160~-20℃; and a complex two-phase flow condensation heat transfer process occurs inside, making it difficult to carry out experimental and theoretical analysis. In actual operation, the inlet temperature and pressure of BOG and LNG are basically unchanged by the control of system parameters, and the inlet flow rate and liquid-gas mass ratio are important adjustment parameters. Secondly, for receiving stations with different receiving capacities, the tower diameter of the recondenser and the height of the packing layer are key design parameters. There are differences in the condensation characteristics of the recondenser under different operating conditions and geometric structures. Whether the outlet gas phase can be completely condensed into the liquid phase, that is, the BOG condensation rate, is the core issue of concern in engineering. Existing research has mainly focused on the flow heat transfer process of random packing, falling film condensation law and distribution characteristics of gas-liquid distribution plate, etc., lacking an overall study of the whole process. The results are only applicable to local processes and it is impossible to establish the condensation law of the macroscopic process of the recondenser. Summary of the invention

[0005] The embodiment of the present application solves the problem of lack of theoretical guidance in the design of existing recondenser structures and operating conditions by providing a method and device for predicting the condensation rate of a gas-liquid co-flow process of a liquefied natural gas recondenser.

[0006] In the first aspect, an embodiment of the present application provides a method for predicting the condensation rate of a liquefied natural gas recondenser in a gas-liquid co-flow process, comprising: acquiring structural parameters of the recondenser and actual operating condition parameters to form an original database; analyzing influencing factors of the condensation rate, and normalizing and dimensionlessly processing them to obtain standard influencing factors; according to typical physical processes in the recondenser, constructing a correlation formula between the standard influencing factors and the condensation rate in partitions, and fitting the undetermined parameters in the correlation formula to determine their expressions; determining an empirical correlation formula of the recondenser based on the expression of the undetermined parameters, thereby predicting the condensation rate of the recondenser.

[0007] In combination with the first aspect, in a possible implementation method, the structural parameters of the recondenser and the actual operating condition parameters are obtained to form an original database, including: constructing a three-dimensional model of the recondenser and setting simulation condition parameters; performing numerical simulation based on different simulation condition parameters to obtain corresponding simulation condensation rates; obtaining actual operating parameters of the recondenser of the liquefied natural gas receiving station; recording the outlet temperature under different actual operating parameters and converting it into a condensation rate; wherein the actual operating parameters and the simulation condition parameters include tower diameter, packing layer height, BOG flow rate and liquid-gas mass ratio; integrating the simulation condition parameters, the simulated condensation rate, the actual operating parameters and the condensation rate to form the original database.

[0008] In combination with the first aspect, in a possible implementation, the structural parameters include a tower diameter and a packing layer height of the recondenser; and the actual operating condition parameters include a BOG flow rate and a liquid-to-gas mass ratio.

[0009] In combination with the first aspect, in a possible implementation, the standard influencing factors include apparent Reynolds number, modified Nusselt number, packing layer height and liquid-gas mass ratio;

[0010] Wherein, the apparent Reynolds number is as follows:

[0011]

[0012] The modified Nusselt number is as follows:

[0013]

[0014] The liquid-to-gas mass ratio is as follows:

[0015]

[0016] The dimensionless height of the packing layer is as follows:

[0017]

[0018] In the formula, Re B represents the apparent Reynolds number, Q represents the inlet BOG flow rate, D represents the tower diameter, μ represents the viscosity, Nu c represents the modified Nusselt number, b represents the characteristic size of the condensation process, Q B Indicates the BOG flow rate of the gas phase, μ B Indicates the viscosity of the vapor phase, Pr B represents the Prandtl number of steam, λ L Indicates the thermal conductivity of the liquid evaporation gas, λ B represents the thermal conductivity of the vapor phase, ρ B represents the density of the vapor phase, ρ L represents the density of the liquid-phase evaporated gas, α represents the liquid-gas mass ratio, Q LNG Indicates the inlet BOG flow rate, Q BOG It represents the inlet BOG flow rate of evaporation gas, H represents the dimensionless height of the packing layer, h represents the actual height of the packing layer, and h0 represents the unit height of the packing area.

[0019] In combination with the first aspect, in a possible implementation manner, the characteristic size of the condensation process is as follows:

[0020]

[0021] In the formula, b represents the characteristic size of the condensation process, σ represents the surface tension, g represents the gravitational acceleration, and ρ l represents the liquid density, ρ g Represents the gas phase density.

[0022] In combination with the first aspect, in a possible implementation, constructing the association equation between the standard influencing factor and the condensation rate by partition according to the typical physical process in the recondenser includes:

[0023] The condensation rate of the recondenser is divided into the condensation rate of the upper region, the condensation rate of the middle region and the condensation rate of the lower region, and they are calculated separately;

[0024] Among them, the condensation rate of the upper area is as follows:

[0025]

[0026] The condensation rate in the middle region is as follows:

[0027]

[0028] The condensation rate of the lower region is as follows:

[0029] β1=1×10 -3 (5.76Re B -6.29)αH -1.5 ;

[0030] Where β0 represents the condensation rate in the upper region, Re B represents the apparent Reynolds number, α represents the liquid-gas mass ratio, Nu c represents the modified Nusselt number, β h represents the condensation rate in the middle area, G ε represents the condensation rate per unit height, Q represents the inlet BOG flow rate, d represents the tower diameter of the recondenser, H represents the dimensionless height of the packing layer, and β1 represents the condensation rate in the lower area.

[0031] In combination with the first aspect, in a possible implementation method, after predicting the condensation rate of the recondenser, it also includes: judging whether the structure of the recondensation tower meets the requirements according to the condensation rate, and if so, designing the recondenser based on the structural parameters; if not, adjusting the structural parameters of the recondensation tower until it meets the requirements.

[0032] In the second aspect, an embodiment of the present application provides a device for predicting the condensation rate of a liquefied natural gas recondenser in a gas-liquid parallel flow process, comprising: an acquisition module, used to acquire the structural parameters of the recondenser and the actual operating condition parameters to form an original database; an analysis module, used to analyze the influencing factors of the condensation rate, and normalize and dimensionlessly process them to obtain standard influencing factors; a fitting module, used to partition and construct a correlation formula between the standard influencing factors and the condensation rate according to typical physical processes in the recondenser, and fit the undetermined parameters in the correlation formula to determine their expressions; a prediction module, used to determine the empirical correlation formula of the recondenser according to the expression of the undetermined parameters, so as to predict the condensation rate of the recondenser.

[0033] In a third aspect, an embodiment of the present application provides a device, comprising: a processor; a memory for storing processor-executable instructions; when the processor executes the executable instructions, it implements the method described in the first aspect or any possible implementation method of the first aspect.

[0034] In a fourth aspect, an embodiment of the present application provides a non-volatile computer-readable storage medium, wherein the non-volatile computer-readable storage medium includes a medium for storing a computer program or instructions, which, when executed, enables the method described in the first aspect or any possible implementation method of the first aspect to be implemented.

[0035] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

[0036] The embodiment of the present application determines the influencing factors of the condensation rate from different levels through structural parameters and actual operating condition parameters; by predicting the condensation characteristics of the recondenser under different tower diameters and packing layer heights, it can guide the design of the recondenser structure. It solves the problem that the existing recondenser structure and operating condition design lacks theoretical guidance, and then guides the recondensation process of the liquefied natural gas receiving station to perform reasonable flow control, so that the BOG at the outlet is fully condensed and the safety of the natural gas pipeline network is guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application 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 any creative work.

[0038] Figure 1 A flow chart of a method for predicting condensation rate of a gas-liquid co-flow process of a liquefied natural gas recondenser provided in an embodiment of the present application;

[0039] Figure 2 A schematic diagram of the structure of a device for predicting the condensation rate of a gas-liquid co-flow process of a liquefied natural gas recondenser provided in an embodiment of the present application;

[0040] Figure 3 A comparison chart of the results of the numerical simulation and the actual working conditions provided in the embodiment of the present application;

[0041] Figure 4 A comparison chart of the prediction accuracy of the condensation rate in the upper region provided in the embodiment of the present application;

[0042] Figure 5 A comparison chart of the prediction accuracy of the condensation rate in the middle region provided in the embodiment of the present application;

[0043] Figure 6 A comparison chart of the prediction accuracy of the condensation rate in the lower region provided in the embodiment of the present application;

[0044] Figure 7 The unit height condensation rate G provided in the embodiment of the present application is ε The curve diagram of the change law along the height;

[0045] Figure 8 This is a comparison chart of the prediction accuracy of the condensation rate of the recondenser provided in the embodiments of the present application. DETAILED DESCRIPTION

[0046] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are 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.

[0047] The following describes some of the techniques involved in the embodiments of the present application to facilitate understanding, and they should be considered as merely exemplary. Therefore, it should be appreciated by those of ordinary skill in the art that various changes and modifications may be made to the embodiments described herein without departing from the scope and spirit of the present application. Similarly, for the sake of clarity and conciseness, some descriptions of well-known functions and structures are omitted in the following description.

[0048] Figure 1 1 is a flow chart of a method for predicting condensation rate of a gas-liquid co-flow process of a liquefied natural gas recondenser provided in an embodiment of the present application, comprising steps 101 to 104. Figure 1 This is only an execution order shown in the embodiment of the present application, and does not represent the only execution order of the method for predicting the condensation rate of the gas-liquid co-flow process of the liquefied natural gas recondenser. In the case where the final result can be achieved, Figure 1 The steps shown may be performed in parallel or reversed.

[0049] Step 101: Obtain the structural parameters of the recondenser and the actual operating condition parameters to form an original database. In an embodiment of the present application, a three-dimensional model of the recondenser is constructed, and the simulation condition parameters are set. Numerical simulation is performed based on different simulation condition parameters to obtain the corresponding simulated condensation rate. Obtain the actual operating parameters of the recondenser of the liquefied natural gas receiving station. Record the outlet temperature under different actual operating parameters and convert it into a condensation rate. Among them, the actual operating parameters and the simulation condition parameters include tower diameter, packing layer height, BOG flow rate and liquid-gas mass ratio. Integrate the simulation condition parameters, simulated condensation rate, actual operating parameters and condensation rate to form an original database.

[0050] Specifically, the original database of the recondenser consists of actual operating parameters and numerical simulation results. Since the actual operating parameters are limited and the local parameters in the recondenser are missing, the numerical simulation method is used to perform modeling calculations to expand the original database of the recondenser. The numerical simulation method in this application has been verified, and the error between the numerical simulation method and the actual operating conditions is within 9%, indicating that the data obtained by the numerical simulation is accurate and reliable. Figure 3 shown.

[0051] Step 102: Analyze the influencing factors of the condensation rate, and normalize and dimensionlessly process them to obtain standard influencing factors. In the embodiment of the present application, the influencing factors of the condensation rate analyzed include the tower diameter of the recondenser, the inlet BOG flow rate, the packing layer height and the liquid-gas mass ratio, and the standard influencing factors obtained after normalization and dimensionless processing include the apparent Reynolds number, the modified Nusselt number, the packing layer height and the liquid-gas mass ratio, as follows.

[0052] The apparent Reynolds number is as follows:

[0053]

[0054] The corrected Nusselt number is as follows:

[0055]

[0056] The liquid-to-gas mass ratio is as follows:

[0057]

[0058] The dimensionless height of the packing layer is as follows:

[0059]

[0060] In the formula, Re B represents the apparent Reynolds number, Q represents the inlet BOG flow rate, D represents the tower diameter, μ represents the viscosity, Nu c represents the modified Nusselt number, b represents the characteristic size of the condensation process, QB Indicates the BOG flow rate of the gas phase, μ B Indicates the viscosity of the vapor phase, Pr B is the gas phase Prandtl number, λ L Indicates the thermal conductivity of the liquid evaporation gas, λ B represents the thermal conductivity of the vapor phase, ρ B represents the density of the vapor phase, ρ L represents the density of the liquid-phase evaporated gas, α represents the liquid-gas mass ratio, Q LNG Indicates the inlet BOG flow rate, Q BOG It represents the inlet BOG flow rate of evaporation gas, H represents the dimensionless height of the packing layer, h represents the actual height of the packing layer, and h0 represents the unit height of the packing area.

[0061] Among them, the characteristic dimensions of the condensation process are as follows:

[0062]

[0063] In the formula, b represents the characteristic size of the condensation process, σ represents the surface tension, g represents the gravitational acceleration, and ρ l represents the liquid density, ρ g Represents the gas phase density.

[0064] Step 103: According to the typical physical process in the recondenser, the association between the standard influencing factors and the condensation rate is constructed by partition, and the undetermined parameters in the association are fitted to determine the expression. In the embodiment of the present application, the condensation rate of the recondenser is divided into the condensation rate of the upper region, the condensation rate of the middle region and the condensation rate of the lower region, and they are calculated separately. According to the analysis of the numerical simulation results, it can be seen that: the condensation in the upper region occurs in the area above the gas-liquid distribution plate. Due to the direct contact between the gas and the liquid, the condensation rate in the upper region is related to the tower diameter, the inlet BOG flow rate and the liquid-gas mass ratio of the recondenser. The gas and liquid in the packing layer area (the condensation rate in the middle region) are fully mixed and directly contacted and condensed, which is the core area of ​​condensation. Therefore, the condensation rate in the middle region is related to the tower diameter, the height of the packing layer, the inlet BOG flow rate and the liquid-gas mass ratio of the recondenser. A small amount of gas phase that has not yet condensed in the lower region condenses, so the condensation rate in the lower region is related to the tower diameter, the height of the packing layer, the inlet BOG flow rate and the liquid-gas mass ratio of the recondenser.

[0065] Specifically, for the upper region, the larger the apparent Reynolds number, the shorter the sufficient contact time between the gas and liquid phases, which is less conducive to condensation. The larger the modified Nusselt number, the greater the total amount of heat exchange process and the condensation rate. An increase in the liquid-gas mass ratio is conducive to condensation. Therefore, the apparent Reynolds number is inversely proportional to the condensation rate, and the modified Nusselt number and the liquid-gas mass ratio are directly proportional to the condensation rate. According to the parameter correlation analysis, the correlation between the modified Nusselt number of 1.8 and the liquid-gas mass ratio of 1.1 and the condensation rate in the upper region is greater than 0.95, and the function form can be preliminarily determined to be: β0=C·f(Re B )α 1.1 Nu c 1.8 The final condensation rate of the upper region is obtained by further fitting as follows:

[0066] The comparison of prediction accuracy of condensation rate in the upper area is shown in the figure below: Figure 4 As shown, the error between the prediction results and the original data is within 20%.

[0067] Regarding the condensation process of BOG in the packing layer, since there is no macroscopic correlation study on direct gas-liquid contact condensation, the mass transfer rate per unit height G is used by referring to and analogizing the mass transfer rate of the mass transfer process in the tower. ε (kg s - 1 m -1 ) represents the condensation efficiency in the packing layer. It means the amount of BOG condensed into LNG per unit height and per unit time in the packing area. The condensation rate in the packing area can be obtained by integrating the condensation mass transfer rate along the height direction: condensation rate

[0068] The condensation rate of each example under different working conditions is fitted along the height direction. Figure 7 Taking typical working conditions as an example, the unit height condensation rate G under each working condition is ε and the dimensionless height H satisfy G ε =a·H -b +c relationship.

[0069] The values ​​of the undetermined parameters a, b, and c under each working condition are shown in Table 1. After fitting in the above manner, the relationship between the condensation rate and the packing layer height is established, and the values ​​of the undetermined parameters a, b, and c are related to the apparent Reynolds number of the gas phase in the recondenser, the condensation corrected Nusselt number, and the liquid-gas ratio. The specific form needs to be determined based on the single parameter correlation combined with dimensional analysis.

[0070] Table 1 Value table of undetermined parameters

[0071] <![CDATA[Re B ×10 5 ]]> <![CDATA[Nu c ]]> Liquid-gas ratio α a b c 4.2667 45.168 7.95 0.2111 0.5507 -0.0881 3.5556 45.168 7.95 0.1705 0.5483 -0.0573 3.0476 45.168 7.95 0.1827 0.4357 -0.0750 4.2667 45.168 7.5 0.1977 0.5967 -0.0685 3.5556 45.168 7.5 0.1055 0.6375 0.0132 6.8141 59.817 7.47 0.3722 0.7574 -0.0917 5.6784 59.817 7.47 0.3479 0.6346 -0.1014 4.8672 59.817 7.47 0.4181 0.7365 -0.1138 5.6784 59.817 8 0.2965 0.7097 -0.0710 9.1601 71.436 7.44 0.2743 0.9865 0.0067 7.6334 71.436 7.44 0.2849 0.8208 -0.02 6.5429 71.436 7.44 0.1996 0.7353 0.0091 9.1601 71.436 8 0.2270 1.0842 0.0397

[0072] The correlation analysis of the unknown parameters a, b, and c with each standard influencing factor was conducted, and it was found that a, b, and c have a strong correlation with the apparent Reynolds number and the modified Nusselt number, but a weak correlation with the liquid-gas mass ratio in any form. Therefore, the expression form of the unknown parameters can be determined as: a=f(Re, Nu c )、b=g(Re,Nu c )、c=ψ(Re,Nu c ). Among them, the correlation between the undetermined parameter b and the independent variable is the most significant, so the undetermined parameter b is fitted and the expression of the undetermined parameter b is obtained as follows:

[0073]

[0074] According to the fitting value, the undetermined parameter b is fixed and refitted to obtain the values ​​of the modified undetermined parameters a and c. Then the above correlation analysis process is repeated for the modified undetermined parameter a, and the correlation formula of the undetermined parameter a is obtained as follows:

[0075]

[0076] The secondary corrected undetermined parameter a is obtained from the expression of the undetermined parameter a. Combined with the corrected value of the undetermined parameter b, the secondary corrected undetermined parameter c is obtained by fitting with a and b as determined values. The expression of c obtained by fitting the secondary corrected undetermined parameter c is:

[0077]

[0078] Therefore, the condensation rate in the middle area is as follows:

[0079] The comparison of prediction accuracy of condensation rate in the central region is shown in the figure below: Figure 5 shown.

[0080] The mass fraction of evaporated gas condensed in the lower area is about 10%. When the upper and middle areas are fully condensed, the condensation amount in the lower area is small. Therefore, the condensation rate in the lower area is proportional to the apparent Reynolds number and inversely proportional to the height of the packing layer. According to the correlation analysis, within the existing data range, the value of the modified Nusselt number has little effect on the condensation rate in the lower area. The correlation between the packing layer height of 1.5, the apparent Reynolds number and the condensation rate in the lower area is close to 1, so the correlation form can be determined as: β1 = C f (Re B )αH -1.5 Therefore, the condensation rate in the lower area is as follows:

[0081] β1=1×10 -3 (5.76Re B -6.29)αH -1.5 The comparison of the prediction accuracy of the condensation rate in the lower area is shown in the figure below: Figure 6As shown, the error between the prediction results and the original data is within 20%.

[0082] Where β0 represents the condensation rate in the upper region, Re B represents the apparent Reynolds number, α represents the liquid-gas mass ratio, Nu c represents the modified Nusselt number, β h represents the condensation rate in the middle area, G ε represents the condensation rate per unit height, Q represents the inlet BOG flow rate, d represents the tower diameter of the recondenser, H represents the dimensionless height of the packing layer, β1 represents the condensation rate of the lower area, h represents the actual height of the packing layer, and C is a constant.

[0083] Step 104: Determine the empirical correlation formula of the recondenser according to the expression of the undetermined parameter, so as to predict the condensation rate of the recondenser. In the embodiment of the present application, the empirical correlation formula of the recondenser is as follows:

[0084] β=β0+β h +β1. In the formula, β represents the condensation rate of the recondenser, β0 represents the condensation rate of the upper area, and β h represents the condensation rate in the middle area, β1 represents the condensation rate in the lower area, and the comparison of the prediction accuracy of the condensation rate is shown in the figure below. Figure 8 shown.

[0085] The applicable range of each influencing factor is determined based on the empirical correlation formula, as shown in Table 2.

[0086] Table 2 Applicable intervals of influencing factors

[0087]

[0088] The empirical correlation obtained in this scheme can predict the condensation effect of the recondenser under different parameters and can be used in the design process of the recondenser structure and operating conditions.

[0089] Although the present application provides method operation steps as described in the embodiments or flowcharts, more or fewer operation steps may be included based on conventional or non-creative labor. The order of steps listed in this embodiment is only one way of executing the order of many steps and does not represent the only execution order. When the actual device or client product is executed, it can be executed in sequence or in parallel according to the method shown in this embodiment or the accompanying drawings (for example, in a parallel processor or multi-threaded processing environment).

[0090] like Figure 2 As shown, the embodiment of the present application also provides a condensation rate prediction device 200 for a gas-liquid co-flow process of a liquefied natural gas recondenser. The device comprises: an acquisition module 201, an analysis module 202, a fitting module 203 and a prediction module 204, which are specifically as follows.

[0091] The acquisition module 201 is used to acquire the structural parameters of the recondenser and the actual operating condition parameters to form an original database.

[0092] The analysis module 202 is used to analyze the influencing factors of the condensation rate, and perform normalization and dimensionless processing on the influencing factors to obtain standard influencing factors.

[0093] The fitting module 203 is used to construct the correlation equation between the standard influencing factors and the condensation rate according to the typical physical process in the recondenser, and to fit the undetermined parameters in the correlation equation to determine its expression.

[0094] The prediction module 204 is used to determine the empirical correlation formula of the recondenser according to the expression of the undetermined parameter, so as to predict the condensation rate of the recondenser.

[0095] Some modules in the apparatus described in the present application can be described in the general context of computer executable instructions executed by a computer, such as program modules. Generally, program modules include routines, programs, objects, components, data structures, classes, etc. that perform specific tasks or implement specific abstract data types. The present application can also be practiced in distributed computing environments, in which tasks are performed by remote processing devices connected through a communication network. In a distributed computing environment, program modules can be located in local and remote computer storage media including storage devices.

[0096] The devices or modules described in the above application embodiments can be implemented by computer chips or entities, or by products with certain functions. For the convenience of description, the above devices are described in various modules according to their functions. When implementing the embodiments of the present application, the functions of each module can be implemented in the same or multiple software and / or hardware. Of course, the module that implements a certain function can also be implemented by combining multiple sub-modules or sub-units.

[0097] The methods, devices or modules described in this application can be implemented in the form of computer-readable program codes. The controller can be implemented in any appropriate manner. For example, the controller can take the form of a microprocessor or processor and a computer-readable medium storing computer-readable program codes (such as software or firmware) that can be executed by the (micro) processor, logic gates, switches, application-specific integrated circuits (English: Application Specific Integrated Circuit; Abbreviation: ASIC), programmable logic controllers and embedded microcontrollers. Examples of controllers include but are not limited to the following microcontrollers: ARC 625D, Atmel AT91SAM, Microchip PIC18F26K20 and Silicone Labs C8051F320. The memory controller can also be implemented as part of the control logic of the memory. Those skilled in the art also know that in addition to implementing the controller in a purely computer-readable program code, the controller can be implemented in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers and embedded microcontrollers by logically programming the method steps. Therefore, this controller can be considered as a hardware component, and the devices included in it for implementing various functions can also be regarded as structures within the hardware component. Or even, the means for realizing various functions may be regarded as both a software module for realizing the method and a structure within a hardware component.

[0098] An embodiment of the present application further provides a device, comprising: a processor; a memory for storing processor executable instructions; when the processor executes the executable instructions, the method described in the embodiment of the present application is implemented.

[0099] The embodiments of the present application also provide a non-volatile computer-readable storage medium on which a computer program or instruction is stored. When the computer program or instruction is executed, the method described in the embodiments of the present application is implemented.

[0100] In addition, each functional module in each embodiment of the present invention may be integrated into one processing module, or each module may exist independently, or two or more modules may be integrated into one module.

[0101] The above storage media include but are not limited to random access memory (RAM), read-only memory (ROM), cache, hard disk (HDD) or memory card. The memory can be used to store computer program instructions.

[0102] It can be known from the description of the above implementation methods that those skilled in the art can clearly understand that the present application can be implemented by means of software plus necessary hardware. Based on such an understanding, the technical solution of the present application can be essentially or partly contributed to the prior art in the form of a software product, or it can be reflected in the implementation process of data migration. The computer software product can be stored in a storage medium, such as ROM / RAM, a magnetic disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a mobile terminal, a server, or a network device, etc.) to execute the methods described in the various embodiments of the present application or certain parts of the embodiments.

[0103] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. All or part of this application can be used in many general or special computer system environments or configurations. For example: personal computers, server computers, handheld devices or portable devices, tablet devices, mobile communication terminals, multi-processor systems, microprocessor-based systems, programmable electronic devices, network PCs, minicomputers, mainframe computers, distributed computing environments including any of the above systems or devices, etc.

[0104] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present application.

Claims

1. A method for predicting the condensation rate of a gas-liquid co-flow process in a liquefied natural gas recondenser, characterized in that: include: Obtaining the structural parameters of the recondenser and the actual operating condition parameters to form an original database; The influencing factors of condensation rate are analyzed, and the standard influencing factors are obtained by normalizing and dimensionless processing. According to the typical physical process in the recondenser, the correlation formula between the standard influencing factors and the condensation rate is constructed by partitioning, and the undetermined parameters in the correlation formula are fitted to determine the expression thereof; An empirical correlation formula for the recondenser is determined according to the expression of the undetermined parameter, so as to predict the condensation rate of the recondenser.

2. The method according to claim 1, characterized in that: The structural parameters of the recondenser and the actual operating condition parameters are obtained to form an original database, including: Construct a three-dimensional model of the recondenser and set the simulation operating parameters; Perform numerical simulation based on different simulation working condition parameters to obtain corresponding simulation condensation rate; Obtain the actual operating parameters of the recondenser at the LNG receiving terminal; Record the outlet temperature under different actual operating parameters and convert it into condensation rate; wherein the actual operating parameters and simulated operating parameters include tower diameter, packing layer height, BOG flow rate and liquid-gas mass ratio; The simulated operating condition parameters, the simulated condensation rate, the actual operating parameters and the condensation rate are integrated to form the original database.

3. The method according to claim 1, characterized in that The structural parameters include the tower diameter and packing layer height of the recondenser; The actual operating condition parameters include BOG flow rate and liquid-to-gas mass ratio.

4. The method according to claim 1, characterized in that: The standard influencing factors include apparent Reynolds number, modified Nusselt number, packing layer height and liquid-gas mass ratio; Wherein, the apparent Reynolds number is as follows: The modified Nusselt number is as follows: The liquid-to-gas mass ratio is as follows: The dimensionless height of the packing layer is as follows: In the formula, Re B represents the apparent Reynolds number, Q represents the inlet BOG flow rate, D represents the tower diameter, μ represents the viscosity, Nu c represents the modified Nusselt number, b represents the characteristic size of the condensation process, Q B Indicates the BOG flow rate of the gas phase, μ B Indicates the viscosity of the vapor phase, Pr B represents the Prandtl number of steam, λ L Indicates the thermal conductivity of the liquid evaporation gas, λ B represents the thermal conductivity of the vapor phase, ρ B represents the density of the vapor phase, ρ L represents the density of the liquid-phase evaporated gas, α represents the liquid-gas mass ratio, Q LNG Indicates the inlet BOG flow rate, Q BOG It represents the inlet BOG flow rate of evaporation gas, H represents the dimensionless height of the packing layer, h represents the actual height of the packing layer, and h0 represents the unit height of the packing area.

5. The method according to claim 4, characterized in that The characteristic dimensions of the condensation process are as follows: In the formula, b represents the characteristic size of the condensation process, σ represents the surface tension, g represents the gravitational acceleration, and ρ l represents the liquid density, ρ g Represents the gas phase density.

6. The method according to claim 4, characterized in that According to the typical physical process in the recondenser, the correlation equation between the standard influencing factors and the condensation rate is constructed by partition, including: The condensation rate of the recondenser is divided into the condensation rate of the upper region, the condensation rate of the middle region and the condensation rate of the lower region, and they are calculated separately; Among them, the condensation rate of the upper area is as follows: The condensation rate in the middle region is as follows: The condensation rate of the lower region is as follows: β1=1×10 -3 (5.76Re B -6.29)αH -1.5 ; Where β0 represents the condensation rate in the upper region, Re B represents the apparent Reynolds number, α represents the liquid-gas mass ratio, Nu c represents the modified Nusselt number, β h represents the condensation rate in the middle area, G ε represents the condensation rate per unit height, Q represents the inlet BOG flow rate, d represents the tower diameter of the recondenser, H represents the height of the packing layer, and β1 represents the condensation rate in the lower area.

7. The method according to claim 1, characterized in that After predicting the condensation rate of the recondenser, the method further includes: Determine whether the structure of the recondensation tower meets the requirements according to the condensation rate, and if so, design the recondenser based on the structural parameters; If not, adjust the structural parameters of the recondensation tower until they meet the requirements.

8. A device for predicting condensation rate of gas-liquid co-flow process in a liquefied natural gas recondenser, characterized in that: include: An acquisition module is used to acquire structural parameters of the recondenser and actual operating condition parameters to form an original database; An analysis module is used to analyze the influencing factors of the condensation rate, and normalize and dimensionlessly process them to obtain standard influencing factors; A fitting module, for constructing a correlation formula between the standard influencing factors and the condensation rate by partition according to a typical physical process in the recondenser, and fitting undetermined parameters in the correlation formula to determine its expression; The prediction module is used to determine the empirical correlation formula of the recondenser according to the expression of the undetermined parameter, so as to predict the condensation rate of the recondenser.

9. A device for executing a method for predicting condensation rate of a gas-liquid co-flow process of a liquefied natural gas recondenser, characterized in that: include: processor; a memory for storing processor-executable instructions; When the processor executes the executable instructions, the method according to any one of claims 1 to 7 is implemented.

10. A non-volatile computer-readable storage medium, characterized in that: The device comprises a computer program or an instruction for storing the computer program or the instruction, which, when executed, enables the method according to any one of claims 1 to 7 to be implemented.

Images