Method for designing number of bent pipes of ship condenser

Abstract

The invention provides a method for designing the number of bent pipes of a ship condenser, and the method comprises the steps: defining set parameters which affect the heat transfer performance of the condenser, and the set parameters comprise the number of the bent pipes; based on other set parameters except the number of the bent pipes, the number range of the used bent pipes is determined; establishing a condenser heat transfer mathematical model based on the set parameters; establishing an elbow number constraint function model based on the size design requirement of the condenser; and the condenser heat transfer mathematical model and the constraint function model are weighted to form a target function in a genetic algorithm, maximization of the target function serves as a target, and meanwhile, the number range of the used bent pipes serves as a constraint condition to conduct iterative calculation so as to obtain the optimal number of the bent pipes. The method is convenient to use, high in accuracy and high in speed, and accurate calculation of the number of the elbows of the ship condenser is achieved.

Description

Technical Field

[0001] The present invention relates to the field of ship condenser design, and particularly to a design method for the number of bent pipes of a ship condenser. Background Art

[0002] A ship condenser is a key component of a ship power system. Its main function is to condense the steam after doing work into liquid water for subsequent recycling. An important factor for evaluating the performance of the condenser is the heat transfer performance. A condenser with better heat transfer performance can significantly improve the thermal efficiency of the power system, which is relatively important for maintaining the safe operation of the ship. As a local area of the metal pipe inside the condenser, the number of bent pipes will directly affect the arrangement of the metal pipes inside the condenser, and thus affect the heat transfer performance of the condenser. Therefore, the design of the number of bent pipes is crucial for the performance of the condenser. Summary of the Invention

[0003] In view of the above-mentioned disadvantages of the related art, the purpose of the present invention is to provide a design method for the number of bent pipes of a ship condenser.

[0004] To achieve the above purpose and other related purposes, the present invention provides a design method for the number of bent pipes of a ship condenser, and the method includes:

[0005] Defining set parameters that affect the heat transfer performance of the condenser, and the set parameters include the number of bent pipes;

[0006] Determining the range of the number of bent pipes used based on other set parameters except the number of bent pipes;

[0007] Establishing a heat transfer mathematical model of the condenser based on the set parameters;

[0008] Establishing a constraint function model for the number of bent pipes based on the design requirements of the condenser size;

[0009] Performing weighted processing on the heat transfer mathematical model and the constraint function model of the condenser to form an objective function in the genetic algorithm, taking the maximization of the objective function as the goal, and at the same time taking the range of the number of bent pipes used as a constraint condition for iterative calculation to obtain the optimal number of bent pipes.

[0010] Optionally, the set parameters further include the total length of the metal pipe, the inner diameter of the metal pipe, and the curvature radius of the bent pipe.

[0011] Optionally, the heat transfer mathematical model of the condenser is: Q = k[πR 2 -π(R - 2r) 2 +2πr(L - nπR)]Δt, where k is the total heat transfer coefficient, R is the curvature radius of the bent pipe, r is the inner diameter of the metal pipe, L is the total length of the metal pipe, Δt is the logarithmic mean temperature difference, and n is the number of bent pipes.

[0012] Optionally, the constraint function model is: where L s represents the condenser size.

[0013] Optionally, the objective function formed by weighting the condenser heat transfer mathematical model and the constraint function model is: where w1 and w2 are weighting coefficients, and Q min is the set minimum total heat transfer amount, and L smax is the set maximum condenser size.

[0014] Optionally, before performing iterative calculation using the genetic algorithm, relevant parameters in the genetic algorithm are first set.

[0015] Optionally, the relevant parameters include population size, number of iterations, crossover rate, maximum mutation rate, minimum mutation rate, and termination condition.

[0016] Optionally, the steps of the iterative calculation include:

[0017] Initializing the population to obtain a set number of individuals;

[0018] Performing encoding, crossover, mutation, and decoding operations on each individual in the population;

[0019] Calculating the fitness value of each individual through the objective function and performing selection and comparison to retain the individual with the highest fitness value;

[0020] Obtaining a set number of new individuals within the front and rear ranges of the retained individuals, and repeating the above steps to retain the individual with the highest fitness value in the new round of iteration;

[0021] Repeating the above steps until the difference in fitness values between two adjacent rounds of iterative calculations is less than the set value, then stopping the calculation.

[0022] As described above, the design method for the number of elbows of the ship condenser of the present invention has the following beneficial effects: The elbow number optimization method of the present invention selects the number of elbows of the condenser as the simulation object, establishes an objective function model, sets relevant constraint conditions based on on-site operating conditions, and introduces a genetic algorithm to calculate the optimal number of elbows of the condenser. The method adopted by the present invention is convenient and simple to use, has high accuracy, high speed, and can accurately calculate the number of elbows of the ship condenser. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It shows a schematic flow chart of the design method for the number of elbows of the ship condenser in the embodiment of the present invention. DETAILED DESCRIPTION

[0024] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand the other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0025] When detailing the embodiments of the present invention, for the convenience of description, the cross-sectional views showing the device structure will be enlarged locally in a non-general proportion, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention here. In addition, in actual production, three-dimensional spatial dimensions including length, width, and depth should be included.

[0026] For the convenience of description, spatial relationship terms such as "below", "beneath", "lower than", "under", "above", "on" may be used herein to describe the relationship between one element or feature shown in the drawings and other elements or features. It will be understood that these spatial relationship terms are intended to cover other directions of the device in use or operation in addition to the directions depicted in the drawings. In addition, when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or there can also be one or more intervening layers. As used herein, "between... and..." means including the endpoint values.

[0027] In the context of the present application, the structure in which the first feature is "above" the second feature described may include embodiments where the first and second features are formed in direct contact, and may also include embodiments where additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0028] It should be noted that the diagrams provided in this embodiment only illustrate the basic concept of the present invention in a schematic manner. Therefore, only the components related to the present invention are shown in the diagrams, rather than being drawn according to the number, shape, and size of the components in actual implementation. The type, quantity, and ratio of each component in its actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0029] As Figure 1 shown, this embodiment provides a design method for the number of elbows in a ship condenser, which is used to optimize the number of elbows in the metal pipes of the condenser. The method includes:

[0030] Defining set parameters that affect the heat transfer performance of the condenser.

[0031] Selecting the number of elbows in the condenser as the research object, and the set parameters include the total length of the metal pipes in the condenser, the inner diameter of the metal pipes, the curvature radius of the elbows, and the number of elbows. Among them, the curvature radius of the elbow refers to the distance from the center of the circle at the bending part of the elbow to the center line of the elbow.

[0032] In this embodiment, it is determined that the radian of the elbow is 180°, and the curvature radius of the elbow remains unchanged; it is determined that the lengths of all straight pipe sections in the metal pipe are the same; it is determined that the total length of the metal pipe remains unchanged during the optimization calculation process; it is determined that the length of all elbows shall not be greater than the length of the straight pipe.

[0033] Based on the total length of the metal pipe, the inner diameter of the metal pipe, and the curvature radius of the elbow, the range of the number of elbows used is determined.

[0034] In the design of the metal pipeline of the condenser, the total length of the metal pipe, the inner diameter of the metal pipe, and the curvature radius of the elbow are usually determined values. Based on the specific values of the total length of the metal pipe, the inner diameter of the metal pipe, and the curvature radius of the elbow, the range of the number of elbows used can be judged by experience.

[0035] Based on the set parameters, a heat transfer mathematical model of the condenser is established, and the total heat transfer amount Q of the condenser is calculated by using this heat transfer mathematical model of the condenser.

[0036] Based on the total length of the metal pipe, the inner diameter of the metal pipe, the curvature radius of the elbow, and the number of elbows, a calculation formula for the total heat transfer amount of the condenser is established: Q = k[πR 2 -π(R - 2r) 2 +2πr(L - nπR)]Δt, where k is the total heat transfer coefficient, R is the curvature radius of the elbow, with the unit of m; r is the inner diameter of the metal pipe, with the unit of m; L is the total length of the metal pipe, with the unit of m; Δt is the logarithmic mean temperature difference, with the unit of °C; n is the number of elbows; the unit of the total heat transfer amount is W.

[0037] Based on the requirements for the size of the condenser, the smaller the size of the condenser is, the better. Therefore, the number of elbows is further restricted to establish a constraint function model: where L s can represent the size of the condenser.

[0038] The heat transfer mathematical model of the condenser and the constraint function model are weighted to form the objective function in the genetic algorithm. Taking the maximization of the objective function as the goal, and at the same time taking the range of the number of elbows used as the constraint condition, iterative calculation is carried out to obtain the optimal number of elbows.

[0039] Specifically, the objective function formed by weighting the heat transfer mathematical model of the condenser and the constraint function model is:

[0040]

[0041] where w1 and w2 are weighting coefficients, which are determined according to specific situations. For example, w1 and w2 are 0.6 and 0.4 respectively, and Q min is the set minimum total heat transfer amount, that is, the total heat transfer amount of the condenser cannot be lower than Q min, in this embodiment, Q min = 500KW, L smax is the set maximum condenser size, that is, the maximum size of the condenser design cannot be greater than L smax , in this embodiment, L smax = 3m.

[0042] Before adopting the genetic algorithm, first set the relevant parameters of the genetic algorithm. The relevant parameters include population size, number of iterations, crossover rate, maximum mutation rate, minimum mutation rate, and termination condition.

[0043] If the population size is set to P, when performing the first iteration, first initialize the population, that is, randomly select P individuals from the constraint conditions of the elbow pipe and encode them respectively. Then, perform crossover and mutation operations on each encoded individual. After the operations are completed, decode them, and then calculate the fitness value of each individual through the objective function. At this time, P fitness values will be obtained. Through the roulette wheel selection strategy or the elite selection strategy, perform selection and comparison to retain the individuals with higher fitness values.

[0044] Obtain a total of P values again in the front and back ranges of the retained individuals, and then repeat the steps of the first iteration for the second iteration to obtain the second retained individuals. By repeating the above steps, after N iterations, the fitness values of N individuals can be obtained. If the difference between the fitness value of the (N - 1)th retained individual and the fitness value of the Nth retained individual is less than the set value, end the loop to obtain the optimal number of elbow pipes.

[0045] For example, the total length of the metal pipe is 1000m, the curvature radius of the elbow pipe is 100mm, and the inner diameter of the metal pipe is 19mm. Based on the above parameters, the number of elbow pipes can be defined between 20 and 200. Among the relevant parameters of the genetic algorithm, the population size is defined as 10, the number of iterations is 1000, the crossover rate is 0.8, the maximum mutation rate is 0.2, and the minimum mutation rate is 0.1.

[0046] When initializing the population, select 10 individuals in the range of 20 - 200, and then perform crossover and mutation operations. Then, calculate 10 fitness values through the objective function F, which are respectively represented as F1, F2... F 10 , after selection and comparison through the roulette wheel selection strategy or the elite selection strategy, if F2 is the best, select a total of 10 new individuals before and after the number of elbow pipes n corresponding to F2, and repeat the above steps to select the second best fitness value. If F 10 is the best. Then compare the difference between F2 and F 10 to see if it is less than the set value. If it is satisfied, stop the calculation, and the number of elbow pipes corresponding to F 10 is the best. Otherwise, continue the iterative calculation until the difference between the values of two adjacent total heat transfer amounts is less than the set value.

[0047] The above embodiments are only illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A design method for the number of elbow pipes of a ship condenser, characterized in that, The method includes: defining set parameters that affect the heat transfer performance of the condenser, where the set parameters include the number of bent pipes; determining the range of the number of bent pipes used based on other set parameters except the number of bent pipes; establishing a mathematical model for the heat transfer of the condenser based on the set parameters; establishing a constraint function model for the number of bent pipes based on the design requirements of the condenser size; performing weighted processing on the mathematical model for the heat transfer of the condenser and the constraint function model to form the objective function in the genetic algorithm, taking the maximization of the objective function as the goal, and at the same time taking the range of the number of bent pipes used as the constraint condition to perform iterative calculations to obtain the optimal number of bent pipes.

2. The design method of the number of elbow pipes of a ship condenser according to claim 1, characterized in that: The set parameters further include the total length of the metal pipes, the inner diameter of the metal pipes, and the curvature radius of the bent pipes.

3. The design method of the number of bent pipes of the ship condenser according to claim 1, characterized in that: The heat transfer mathematical model of the condenser is: Q = k[πR 2 - π(R - 2r) 2 + 2πr(L - nπR)]Δt, where k is the total heat transfer coefficient, R is the curvature radius of the bent pipe, r is the inner diameter of the metal pipe, L is the total length of the metal pipe, Δt is the logarithmic mean temperature difference, and n is the number of bent pipes.

4. The design method of the number of elbow pipes of a ship condenser according to claim 1, characterized in that: The constraint function model is as follows: where L s represents the condenser size.

5. The design method of the number of elbow pipes of a ship condenser according to claim 1, characterized in that: The objective function formed by weighting the heat transfer mathematical model and the constraint function model of the condenser is as follows: where w1 and w2 are weighting coefficients, Q min is the set minimum total heat transfer amount, and L smax is the set maximum condenser size.

6. The design method of the number of elbows of a ship condenser according to claim 1, characterized in that: Before performing iterative calculations using the genetic algorithm, first set the relevant parameters in the genetic algorithm.

7. The design method of the number of elbow pipes of a ship condenser according to claim 1, characterized in that: The relevant parameters include the population size, the number of iterations, the crossover rate, the maximum mutation rate, the minimum mutation rate, and the termination condition.

8. The design method of the number of elbow pipes of a ship condenser according to claim 1, characterized in that: The steps of the iterative calculation include: initializing the population to obtain a set number of individuals; performing encoding, crossover, mutation, and decoding operations on each individual in the population; calculating the fitness value of each individual through the objective function and performing selection and comparison to retain the individual with the highest fitness value; obtaining a set number of new individuals within the front and rear ranges of the retained individuals, and repeating the above steps to retain the individual with the highest fitness value in the new round of iteration; repeating the above steps until the difference in fitness values between two adjacent rounds of iterative calculations is less than the set value, then stop the calculation.

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