Size design method for semicircular flow channel structure of printed circuit board type heat exchanger

Abstract

The invention provides a size design method for a semicircular flow channel structure of a printed circuit board type heat exchanger. The size design method comprises the steps that S1, parametric modeling is conducted on the semicircular flow channel structure of a PCHE core body; s2, dimension parameters of the semicircular flow channel structure are dimensionless, the aperture ratio of the section of a semicircular plate serves as an optimization variable, and the value range of the parameters is determined; s3, a test design method is adopted to generate design test points, and a sample set is obtained through finite element calculation; s4, according to the design standard, screening the maximum working pressure of different runner structure sizes; and S5, performing nonlinear curved surface fitting on calculation results under different sheet thicknesses to obtain a fitting equation. According to the design method, whether the strength of the size of the semicircular runner structure meeting the thermotechnical design reaches the standard or not can be more accurately and rapidly judged, and the reliability is high.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat exchange equipment, in particular to a size design method of a semi-circular flow channel structure of a printed circuit board type heat exchanger. BACKGROUND

[0002] The printed circuit board type heat exchanger (PCHE) is a micro-channel heat exchanger with excellent heat transfer performance. The fluid channel is formed on a metal plate by photochemical etching process. The channel cross section is mainly in the form of a semi-circular structure with a millimeter level. It has the advantages of high temperature resistance, high pressure resistance, compact structure, small volume, light weight, high heat transfer area density, and low leakage risk. It is often used as a core equipment in the fields of petroleum chemical industry, ocean engineering, nuclear energy, thermal power, shipbuilding, hydrogen energy, etc.

[0003] For PCHE manufacturing and wide application, total cost analysis as a total evaluation index is of great significance. Therefore, the patent with the application number 202311285314.6 discloses a S-CO2 printed circuit board type heat exchanger (PCHE) configuration optimization method based on minimum cost, which includes S101: constructing a S-CO2 cycle printed circuit board type heat exchanger and a segmented calculation model; S102: taking the minimum dimensionless total cost as the optimization objective, and adopting a segmented thermal design method; S103: optimizing the length-width ratio of the S-CO2 printed circuit board heat exchanger; S104: optimizing the heat exchange channel radius of the S-CO2 printed circuit board heat exchanger; S105: performing double degree of freedom optimization of the S-CO2 printed circuit board heat exchanger. This scheme mainly designs the flow channel size through total cost, flow characteristics, heat transfer performance, etc., and does not consider the influence of flow channel size on the strength of the heat exchanger.

[0004] Research has found that the strength of the printed circuit board type heat exchanger is greatly affected by the flow channel structure size, and also relates to the safety and reliability of the heat exchanger. However, the semi-circular flow channel structure size of the printed circuit board type heat exchanger is currently mainly calculated by the design method in ASME VIII-1, but only the rectangular structure can be initially selected, and the initial selection of the semi-circular channel structure can only be calculated by being equivalent to the rectangular structure, so that the designed flow channel has insufficient applicability and does not have economic efficiency.

[0005] Therefore, the present application is proposed. SUMMARY

[0006] The problem solved by the present application is that the prior art cannot quickly and accurately determine whether the size of the semi-circular channel of the printed circuit board type heat exchanger that meets the thermal design can meet the strength requirement, resulting in low design efficiency and poor reliability of the printed circuit board type heat exchanger.

[0007] To solve the above problems, the application provides a size design method of a printed circuit board type heat exchanger semicircular flow channel structure, comprising:

[0008] S1, parameterized modeling of the PCHE core semicircular flow channel structure;

[0009] S2, dimensionless of the semicircular flow channel structure size parameters, and taking the opening rate of the semicircular plate section as an optimization variable to determine the value range of the parameters;

[0010] S3, generating design test points by using a test design method, and obtaining a sample set by finite element calculation;

[0011] S4, screening the maximum working pressure of different flow channel structures according to the design standard;

[0012] S5, nonlinear surface fitting of the calculation results under different plate thicknesses to obtain a fitting equation.

[0013] Preferably, in step S1, the size of the semicircular flow channel plate is parameterized and a two-dimensional geometric model is established based on the plate thickness t, etching depth H and etching channel center distance e.

[0014] Preferably, in step S2, the dimensionless parameters of the plate size are:

[0015] The opening rate Acr is Wherein the value range of Acr is 0.1-0.8, the thickness t of the plate is 0.5-2.5mm, and the etching depth H satisfies 0<H<t.

[0016] Preferably, in step S3, the test points of e>2H are selected to construct the sample set.

[0017] Preferably, in step S4, the ansysworkbench finite element software is used for numerical simulation analysis, the equivalent stress of the plate under different pressures is calculated, the pressure value that just meets the strength condition is recorded, and the maximum equivalent stress on the path Path is taken as the calculation result.

[0018] Preferably, the equivalent stress calculated in step S4 should meet the following conditions: a) the allowable limit of the primary overall film equivalent stress (S Ⅰ ) is KS m t , S m t is the allowable stress of the material at the design temperature; b) the allowable limit of the primary local film equivalent stress (S Ⅱ ) is KS PL ; c) the allowable limit of the primary film (overall or local) plus the primary bending equivalent stress (S Ⅲ ) is KSPL .

[0019] Preferably, the fitting equation in the step S5 is P=a+b·wf 2 +c·wf+d·df 2 +e·df+f·wf·df.

[0020] Compared with the prior art, the size design method of the semicircular flow channel structure of the printed circuit board type heat exchanger has the following beneficial effects: 1) the present application provides a finite element calculation method for initially selecting the size of the semicircular flow channel structure, and obtains fitting equations and curved surfaces for several commonly used plate thicknesses. Compared with the prior art such as the formula method, it can more accurately and quickly determine whether the semicircular flow channel structure size obtained by thermal design meets the strength condition; the present application uses a finite element model to calculate the strength of different plate sizes, which can handle more complex sizes compared with the formula method, improve the applicability of the calculation results, and the calculation results are more economical; the design method proposed in the present application can be used for the initial selection of the flow channel structure size of PCHE plates of other materials and flow channel forms, and has universal reference significance. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 A flow chart of the size design method of the semicircular flow channel structure according to the embodiment 1 of the present application;

[0022] Figure 2 A size diagram of the semicircular flow channel structure in the plate according to the embodiment 1 of the present application;

[0023] Figure 3 A sampling path diagram according to the embodiment 1 of the present application;

[0024] Figure 4 A nonlinear curved surface fitting result diagram according to the embodiment 1 of the present application. DETAILED DESCRIPTION

[0025] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below with reference to the drawings. On the premise of not conflicting, the technical features of the embodiments of the present application can be combined with each other.

[0026] Embodiment 1

[0027] As shown in Figure 1 , a size design method of a semicircular flow channel structure of a printed circuit board type heat exchanger, comprising:

[0028] S1, parameterized modeling is performed on the semicircular flow channel structure of the PCHE core body;

[0029] The PCHE core is formed by etching a plate into a semicircular fluid channel, and the cold and hot side plates are stacked and formed by diffusion welding, as shown in Figure 2 The thickness of the plate is t, the etching depth is H, and the center distance of the etching channel is e. The relevant dimensions are parameterized, and a two-dimensional geometric model (3 rows of heat exchange channels x 3 columns) of the PCHE semicircular flow channel structure is established. The effect of core length on stress distribution can be ignored.

[0030] S2, the size parameters of the semicircular flow channel structure are dimensionless, and the opening ratio of the semicircular plate section is taken as the optimization variable to determine the value range of the parameters;

[0031] Assume that the dimensionless parameters of the plate size are:

[0032] The opening ratio Acr is

[0033] Therefore Where Acr represents the proportion of the opening part on the plate to the plate cross-sectional area, the value range is 0.1-0.8, the thickness t of the plate is selected as 0.5, 1.0, 1.5, 2.0, 2.5 mm, and the etching depth H satisfies 0<H<t.

[0034] S3, generate design test points by using the test design method, and obtain the sample set by finite element calculation;

[0035] According to the values of Acr, t and H, the values of wf, df and e are calculated by using the above formula. If e<2H exists, it represents that the structure is unreasonable and should be discarded. The test points for different plate thicknesses t=0.5, 1.0, 1.5, 2.0, 2.5 mm are generated by using the difference sampling method, and the sample set is obtained by finite element calculation, as shown in Table 1.

[0036] Table 1 Sample set obtained by finite element calculation

[0037]

[0038]

[0039]

[0040] S4, according to the design standard, the maximum working pressure of different flow channel structure sizes is screened;

[0041] According to the plastic collapse evaluation in the national standard GB / T 4732-2024 pressure vessel analysis and design standard, to prevent plastic collapse failure, the equivalent stress in the calculation should meet: a) the allowable limit of the first overall membrane equivalent stress (SI) is KSmt, and Smt is the allowable stress of the material at the design temperature; b) the allowable limit of the first local membrane equivalent stress (SII) is KSPL; c) the allowable limit of the first membrane (overall or local) plus the first bending equivalent stress (SIII) is KSPL. Among them, because the load combination in the design method does not include wind load and earthquake load, the load combination coefficient K is 1.0. The ansysworkbench finite element software is used for numerical simulation analysis, the equivalent stress of the plate under different pressures is calculated, the pressure value that just meets the strength condition is recorded, the maximum equivalent stress on the path Path is taken as the calculation result, and the sampling path is as shown in Figure 3

[0042] S5, the calculation results under different plate thicknesses are respectively subjected to nonlinear curved surface fitting to obtain a fitting equation.

[0043] A 3D scatter plot is established for the calculation results with wf as the x-axis, df as the y-axis and P as the z-axis, and nonlinear curved surface fitting is performed, the function model is selected as an explicit function, the function type is LabTalk expression, the independent variable is wf, df, the dependent variable is P, and the parameters are a, b, c, d, e and f. The fitting equation body is:

[0044] P = a + b·wf 2 + c·wf + d·df 2 + e·df + f·wf·df, wherein the value of a is 27.36731±3.84261, the value of b is-52.87172±3.89717, the value of c is 29.5994±6.55622, the value of d is 1.78387±5.56671, the value of e is-10.49775±8.08341, and the value of f is 5.73211±5.22558, as shown in Table 2, and the fitting result is shown in FIG. 4.

[0045] Table 2 Fitting equation of different plate thickness t (0.5, 1.0, 1.5, 2.0, 2.5 mm)

[0046]

[0047]

[0048] Example 2 result verification

[0049] ​The initial design conditions for a heat exchanger used in a certain system are an inlet design temperature of 60°C and a design pressure of 7.7 MPa. The dimensions of the semicircular flow channel plate obtained through thermal design are thickness t = 1.5 mm, etching depth H = 1 mm, and etching channel center distance e = 2.4 mm.

[0050] The parameters of the semicircular flow channel structure are dimensionless.

[0051] Substitute the fitting equation P = 27.37-52.87wf for a plate thickness of 1.5 mm 2 +29.6wf+1.78df 2 P = 12.3 MPa is obtained from -10.5df+5.73wfdf, which is significantly higher than the design pressure value of 7.7 MPa. The size of the semicircular flow channel plate obtained through thermal design can meet the strength design standards.

[0052] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined by the claims.

Claims

1. A method for designing the size of a semicircular flow channel structure of a printed circuit board type heat exchanger, characterized in that: include: S1. Parametric modeling of the semicircular flow channel structure of the PCHE core; S2. Dimensionalize the semicircular channel structure parameters and use the porosity of the semicircular plate section as an optimization variable to determine the parameter value range. S3. Use the experimental design method to generate design test points and obtain the sample set through finite element calculation; S4. Screen the maximum working pressure of different flow channel structure sizes according to design standards; S5. Perform nonlinear surface fitting on the calculation results under different plate thicknesses to obtain the fitting equation.

2. The method for designing the size of a semicircular flow channel structure of a printed circuit board type heat exchanger according to claim 1, characterized in that: In step S1 , the size of the semicircular flow channel plate is parameterized based on the plate thickness t, etching depth H, and etching channel center distance e, and a two-dimensional geometric model is established.

3. The method for designing the size of a semicircular flow channel structure of a printed circuit board type heat exchanger according to claim 1, characterized in that: The dimensionless parameter of the plate size in step S2 is: ； ； The opening ratio Acr is , where the value range of Acr is 0.1~0.8, the thickness t of the plate is 0.5~2.5mm, and the etching depth H satisfies 0 <H<t。 4. The method for designing the size of a semicircular flow channel structure of a printed circuit board type heat exchanger according to claim 1, characterized in that: In step S3, test points with e>2H are selected to construct a sample set.

5. The method for designing the size of a semicircular flow channel structure of a printed circuit board type heat exchanger according to claim 1, characterized in that: In step S4, the ANSYS workbench finite element software is used to perform numerical simulation analysis, calculate the equivalent stress of the plate under different pressures, record the pressure value that just meets the strength condition, and take the maximum equivalent stress on the path Path as the calculation result.

6. The method for designing the size of a semicircular flow channel structure of a printed circuit board type heat exchanger according to claim 5, characterized in that: The equivalent stress calculated in step S4 should satisfy the following requirements: a) the primary overall membrane equivalent stress (S Ⅰ ) is allowed to be KS m t , S m t is the allowable stress of the material at the design temperature; b) the primary local membrane equivalent stress (S Ⅱ ) is allowed to be KS PL ; c) once the film (whole or local) is subjected to a bending equivalent stress (S Ⅲ ) is allowed to be KS PL。 7. The method for designing the size of a semicircular flow channel structure of a printed circuit board type heat exchanger according to claim 1, characterized in that: The fitting equation in step S5 is: .

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