A continuous fin optimization method for a refrigerator evaporator and a refrigerator evaporator

Abstract

The present invention discloses a method for optimizing continuous fins of a refrigerator evaporator and a refrigerator evaporator. The method includes: establishing a two-dimensional geometric model of the evaporator according to the original evaporator model and the expected overall size of the optimized evaporator; then, according to the working environment of the refrigerator evaporator, determining the gas-side inlet velocity v in of the evaporator, the gas-side inlet temperature T in of the evaporator, the wall temperature T e of the evaporator, and the physical property parameters of the fluid and solid materials; establishing a topology optimization model of the evaporator according to the fluid flow control equation, constraint conditions, and constructing an objective function; stretching the two-dimensional result obtained by topology optimization to obtain a three-dimensional optimized fin until the outlet temperature and inlet pressure of the evaporator after the optimized fin meet the requirements. The invention optimizes the fins of the evaporator by using the topology optimization method, reduces the dependence on the experience of designers, and the pressure drop of the optimized structure is controllable. The obtained evaporator fin structure can greatly improve the heat transfer efficiency on the air side, and when it is used in a refrigerator, the volume ratio of the refrigerator can be increased.

Description

Technical Field

[0001] The present invention relates to the technical field of enhanced heat transfer of heat exchangers, and particularly to an optimization method for continuous fins of a refrigerator evaporator and a refrigerator evaporator. Background Art

[0002] With the continuous consumption of energy and the higher requirements of people for living standards, energy conservation and large capacity of refrigerators have become the main development trends. The evaporator is one of the important components of a refrigerator, and its performance has a significant impact on the overall energy consumption of the refrigerator. In addition, for air-cooled refrigerators, the evaporator is mostly placed behind the refrigerating and freezing chambers, and its volume also has an important impact on the volume utilization rate of the refrigerator. Therefore, optimizing the performance of the evaporator to reduce its volume is helpful for reducing the energy consumption of the refrigerator and increasing the volume utilization rate.

[0003] Considering requirements such as defrosting, currently, the evaporators used in air-cooled refrigerators are mainly tube-fin evaporators. The optimization of traditional tube-fin evaporators mainly falls into two directions. One is the optimization of the tube shape, and the other is the optimization of the fin structure. To enhance heat transfer, the main methods adopted for fin structure optimization are: using corrugated plates, louvered plates, adding vortex generators, etc. Among the above fin optimization methods, corrugated plates and louvered plates are not conducive to defrosting, and the setting of the position and size of the vortex generator requires high experience for designers and is not intelligent enough. Summary of the Invention

[0004] To overcome the shortcomings of the above technologies, the purpose of the present invention is to provide an optimization method for continuous fins of a refrigerator evaporator. This optimization method uses topology optimization technology, which can greatly reduce the dependence on the experience of designers. In addition, the fluid flow is described by the Darcy model. By adjusting the inlet power and changing the fluid velocity, it can be applied to the design of large Reynolds number conditions, breaking through the limitation of common topology optimization on laminar flow states, and avoiding the use of turbulent topology optimization methods, reducing the design difficulty; by changing the projection slope, the convergence of the optimization process and the clarity of the boundary of the optimization result are greatly increased.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] An optimization method for continuous fins of a refrigerator evaporator, comprising:

[0007] Step 1: According to the original evaporator model and the expected overall size of the evaporator after optimization, simplify the three-dimensional original evaporator model into a two-dimensional original evaporator model, and establish an evaporator two-dimensional geometric model for topology optimization through the two-dimensional original evaporator model. The evaporator two-dimensional geometric model includes the number of tube rows N, the tube flow direction spacing S L , the tube transverse spacing S W , the inlet width W, the length L, the outer diameter D1 of the tube, the inlet and outlet positions, and the design domain range;

[0008] Step 2: Determine the inlet velocity v of the gas side of the evaporator according to the working environment of the refrigerator evaporator in , the inlet temperature T of the gas side of the evaporator in , the wall temperature T e and the physical property parameters of the fluid and solid materials;

[0009] Step 3: Establish an evaporator topology optimization model according to the fluid flow control method, constraint conditions, and construct an objective function;

[0010] Step 4: Solve the evaporator topology optimization model;

[0011] Step 5: Obtain the two-dimensional topology optimization result of the fin according to the solution result of Step 4;

[0012] Step 6: Import the two-dimensional topology optimization result of the fin obtained in Step 5 into the graphical design software, simplify the solid boundary using a spline curve, and stretch the simplified boundary into a protrusion with the same thickness as the original fin and a height of 1 / 5 - 3 / 4 of the original fin pitch to establish a three-dimensional geometric model of the remaining part of the original fin and the tube;

[0013] Step 7: Import the three-dimensional geometric model established in Step 6 into the computational fluid dynamics software for simulation calculation: Apply a constant temperature boundary condition to the inner wall of the tube, and specify a constant mass flow rate and inlet temperature for the entire design domain inlet;

[0014] Step 8: According to the simulation calculation result in Step 7, determine whether the outlet temperature and inlet pressure of the evaporator after optimizing the fin meet the requirements. If they meet, obtain the optimized evaporator fin; if not, repeat Steps 3 - 7 until the requirements are met.

[0015] A further technical solution is that in Step 1, the two-dimensional geometric model of the evaporator further includes a second tube outer diameter D2 concentric with the tube outer diameter D1, and D2 > D1. The fin position outside the D2 annular region is set as the design domain.

[0016] A further technical solution is that the physical property parameters of the fluid and solid materials include: thermal conductivity, constant pressure heat capacity, dynamic viscosity, and density.

[0017] A further technical solution is that the thermal conductivity of the fluid and solid materials in the design domain is obtained by the following formula:

[0018]

[0019] where λ(γ) is the thermal conductivity interpolation function, λ f is the fluid thermal conductivity, λ s is the solid thermal conductivity, q λ is the thermal conductivity convex factor, and γ is the design variable.

[0020] A further technical solution is as follows:

[0021] In step 3, establishing the topological optimization model of the evaporator specifically includes:

[0022] (3a). Describe the fluid flow in the design domain and determine the fluid flow control equation. The specific fluid flow control equation is as follows:

[0023]

[0024] κ(γ) = κ s +(κ f -κ s )γ 3 ;

[0025] where u is the fluid velocity, κ(γ) is the permeability interpolation function, μ is the fluid dynamic viscosity, is the pressure gradient in the design domain, κ s is the solid permeability, and κ f is the fluid working medium permeability;

[0026] (3b). Constrain the pump work on the gas side of the evaporator and specify the inlet pump work P in of the two-dimensional geometric model of the evaporator. The formula is as follows:

[0027] ∫ Γ pdΓ ≤ P in

[0028] where P in is the inlet pump work, p is the pressure at each point, and Γ is the inlet boundary;

[0029] (3c). Construct the objective function and select the maximum heat extraction in the solid domain as the objective. The formula is as follows:

[0030]

[0031] where obj is the objective function; Ω is the design domain, h q is the heat extraction coefficient, q h is the heat extraction convex factor, T is the temperature at each point in the design domain, and T e is the refrigerant evaporation temperature;

[0032] (3d). According to steps (3a) to (3c), construct the topological optimization criterion with the following formula:

[0033] find γ

[0034]

[0035]

[0036]

[0037] ∫ Γ pdΓ ≤ P in

[0038] ∫ Ω γdΩ ≥ V min

[0039] 0 ≤ γ ≤ 1

[0040] Among them, T is the temperature at each point, ρ is the density, and C p is the heat capacity at constant pressure, and V min is the limiting value of the volume fraction.

[0041] A further technical solution is that the solid permeability κ s and the fluid working medium permeability κ f are determined by the following method:

[0042] Establish a model that simultaneously includes a solid domain and a fluid domain. Among them, the fluid domain contains at least one bend. Given the boundary conditions, make it a conjugate heat transfer model of fluid-solid, and use a turbulence model for calculation to obtain the velocity field, pressure distribution, and temperature field; set different permeabilities for the solid domain and the fluid domain in the model that includes the solid domain and the fluid domain, and all use the Darcy seepage model for calculation; compare the results obtained by using the Darcy seepage model with the results obtained by using the turbulence model. If the temperature and velocity distributions are close, determine to select the current set permeability value for subsequent optimization; if not, adjust the permeability until it is close to the calculation result of the turbulence model. At this time, the set permeability is the permeability used for subsequent optimization.

[0043] A further technical solution is that in step 4, the process of solving the topological optimization model of the evaporator specifically includes:

[0044] (4a). Mesh the design domain;

[0045] (4b). When solving the topological optimization, when the difference between the design variables in two consecutive iterations does not exceed 10 -5 , it is considered convergent;

[0046] (4c). Filter and project the design variables. At the beginning of the calculation, select a smaller projection slope β, and during the calculation process, gradually increase the projection slope β. Its expression is as follows:

[0047]

[0048]

[0049] Among them, γ c is the original design variable, r is the filtering radius, and γf where is the design variable after filtering, β is the projection coefficient, and γ β is the projection point threshold.

[0050] A further technical solution is that in the step 6, when stretching the simplified boundary, the stretching range is set to 1 / 5 - 1 of the edge of the closed-loop solid domain.

[0051] Meanwhile, the present invention also provides the following technical solution:

[0052] A refrigerator evaporator includes fins, and a plurality of evaporator round tubes and protrusions arranged on the fins. The protrusions are formed by stretching through the above-mentioned continuous fin optimization method for the refrigerator evaporator.

[0053] A further technical solution is that the plurality of evaporator round tubes and the protrusions are arranged at intervals, and the evaporator round tubes are arranged in one row or multiple rows.

[0054] Compared with the prior art, the beneficial effects of the present invention are:

[0055] The present invention optimizes the evaporator fins by using the topology optimization method. Compared with the traditional method, it reduces the dependence on the experience of designers and the pressure drop of the optimized structure is controllable. In addition, the present invention uses the Darcy model to describe the fluid flow, breaking through the applicable Reynolds number range of common topology optimization. The evaporator fin structure obtained by the optimization method of the present invention can greatly improve the heat transfer efficiency on the air side. Applying the refrigerator evaporator obtained by this method to a refrigerator can increase the volume ratio of the refrigerator. Description of the Drawings

[0056] Figure 1 is the two-dimensional original evaporator model in the embodiment of the present invention;

[0057] Figure 2 is the two-dimensional result obtained by topology optimization in the embodiment of the present invention;

[0058] Figure 3 is the schematic diagram of the optimized fin structure in the embodiment of the present invention;

[0059] Figure 4 is the schematic diagram of the evaporator structure with continuous fins after optimization in the embodiment of the present invention;

[0060] Figure 5 is the schematic diagram of the evaporator structure with flat fins in the embodiment of the present invention.

[0061] Reference Signs:

[0062] 1 - Optimized fin; 11 - Fin base plane; 12 - Protrusion; 2 - Evaporator round tube; 3 - Flat fin; 4 - Solid domain; 5 - Fluid domain; L - Length; W - Inlet width; D1 - Outer diameter of the tube; D2 - Second outer diameter of the tube; SL - Tube flow direction spacing. Detailed implementation manners

[0063] Next, in combination with the accompanying drawings in the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0064] Embodiment 1

[0065] An optimization method for continuous fins of a refrigerator evaporator, the specific steps are as follows:

[0066] Step 1, according to the original evaporator model and the expected overall size of the optimized evaporator, simplify the three-dimensional original evaporator model into a two-dimensional original evaporator model, and establish a two-dimensional geometric model of the evaporator for topology optimization through the two-dimensional original evaporator model.

[0067] Specifically, as Figure 1 shown, the two-dimensional geometric model of the evaporator includes determining the inlet width W, length L, number of tube rows N, tube flow direction spacing S L , tube transverse spacing S W , tube outer diameter D1, inlet and outlet positions, and design domain range, etc. The annular area between the tubes can be set as a non-design domain, and the rest is the design domain; preferably, in order to ensure the processability of the topology optimization structure, a second tube outer diameter D2 larger than the tube outer diameter D1 is determined. Among them, the annular area between the tubes is the non-design domain, and the rest is the design domain, as Figure 1 shown by the shaded line.

[0068] Step 2, according to the working environment of the refrigerator evaporator, determine the gas-side inlet velocity v in of the evaporator, gas-side inlet temperature T in of the evaporator, wall temperature T e of the evaporator, and physical property parameters of the fluid and solid materials;

[0069] Specifically, in this embodiment, determine the gas-side inlet temperature T in of the evaporator = 273.15K; set the wall temperature T e as the evaporation temperature of the refrigerant in the tube, and the wall temperature T e = 253.15K; determine the physical property parameters of the fluid and solid materials including: thermal conductivity, constant pressure heat capacity, dynamic viscosity, and density. Among them, the thermal conductivity in the design domain is obtained by the Darcy interpolation method, and the formula is as follows:

[0070]

[0071] Among them, λ(γ) is the thermal conductivity interpolation function; λ f is the fluid thermal conductivity, and λ s is the solid thermal conductivity, q λ is the convex factor of the thermal conductivity. In this embodiment, q λ = 0.01, and γ is the design variable.

[0072] Step 3: According to the fluid flow control method, constraints, and construct an objective function to establish an evaporator topology optimization model;

[0073] (3a). Use the Darcy seepage model to describe the fluid flow in the design domain and determine the fluid flow control method. The control equation of the specific fluid flow control method is:

[0074]

[0075] κ(γ) = κ s +(κ f -κ s )γ 3 ;

[0076] Among them, u is the fluid velocity, κ(γ) is the permeability interpolation function, μ is the fluid dynamic viscosity, is the pressure gradient in the design domain, κ s is the solid permeability, and κ f is the fluid working medium permeability.

[0077] In this embodiment, κ s = 1*10 -16 m 2 , and κ f = 1*10 -4 m 2 . Among them, the solid permeability κ s and the fluid working medium permeability κ f can be determined by the following method: Establish a model that simultaneously includes the solid domain and the fluid domain. Among them, the fluid domain includes two turning bends. Given the boundary conditions, make it a conjugate heat transfer model of fluid-solid, and use the turbulence model for calculation to obtain its velocity field, pressure distribution, and temperature field. Set different permeabilities for the solid domain and the fluid domain in the model that includes the solid domain and the fluid domain, and all use the Darcy seepage model for calculation; compare the obtained results with the results of the turbulence model. If the temperature and velocity distributions are close, determine to select the permeability value for subsequent optimization. If not, adjust the permeability until it is close to the calculation results of the turbulence model. At this time, the permeability is the permeability used for subsequent optimization.

[0078] (3b). Constrain the pump work on the gas side of the evaporator, and given the inlet pump work P in of the two-dimensional model, the formula is as follows:

[0079] ∫ Γ pdΓ ≤ P in ;

[0080] Among them, P in is the inlet pump power, p is the pressure at each point, and Γ is the inlet boundary.

[0081] (3c). Construct the objective function. In this embodiment, the maximum heat extraction in the solid domain is selected as the objective, and the formula is as follows:

[0082]

[0083] Among them, obj is the objective function; Ω is the design domain, h q is the heat extraction coefficient, q h is the heat extraction convex factor, T is the temperature at each point in the design domain, T e is the refrigerant evaporation temperature. In this embodiment, q h is given as 0.1.

[0084] (3d). Combining (3a) to (3c), the topology optimization criterion is constructed as:

[0085] find γ;

[0086]

[0087]

[0088]

[0089] ∫ T pdΓ ≤ P in ;

[0090] ∫ Ω γdΩ ≥ V min ;

[0091] 0 ≤ γ ≤ 1;

[0092] Among them, T is the temperature at each point, ρ is the density, C p is the constant pressure heat capacity, and V min is the volume fraction limit value.

[0093] Step 4, solve the evaporator topology optimization model:

[0094] (4a). Mesh the design domain. Since there are non-design domains with multiple tubes, preferably, in this embodiment, triangular meshes are used to divide the boundary layer in the area near the tube wall;

[0095] (4b). Select the moving asymptote algorithm to solve the topology optimization. When the difference in design variables between two iterations does not exceed 10-5 When it is satisfied, it is regarded as convergence;

[0096] (4c). During the topology optimization process, the Helmholtz filtering method is selected to avoid the appearance of fluid domain islands; in order to obtain a clear boundary, the hyperbolic tangent projection method is adopted for the design variables, and its expression is as follows:

[0097]

[0098]

[0099] Among them, γ c is the original design variable, r is the filtering radius, γ f is the filtered design variable, β is the projection coefficient. In this embodiment, β adopts a step-by-step increasing method. Given the initial β = 1, β doubles every 100 calculations until its value is 16. γ β is the projection point threshold. In this embodiment, γ β is selected to be 0.75.

[0100] Step 5, as Figure 2 shown, select the γ = 0.5 isosurface in the optimization result obtained in step 4 as the solid domain boundary to obtain the two-dimensional topology optimization result of the fin and output it; the output design domain includes a fluid domain 5 and a solid domain 4, where the solid domain is the position where the protrusion is set.

[0101] Step 6, import the two-dimensional topology optimization result of the fin obtained above into the graphical design software, simplify the solid boundary with a spline curve, and equidistantly space the simplified boundary. Stretch the closed area formed by the simplified boundary and the equidistant boundary to form a protrusion.

[0102] In this embodiment, it is selected to equidistantly space the simplified solid boundary by the same thickness as the original fin, stretch each single side of each closed solid domain, the stretching direction is perpendicular to the fin base plane 11, and the stretching height is 1 / 5 - 3 / 4 of the fin pitch. After stretching, all the protrusions 12 are located on one side of the fin base plane. In other embodiments, the stretching direction can form an arbitrary angle with the fin base plane, and the stretched protrusions can be located on one side of the fin base plane or on both sides. According to the two-dimensional topology optimization design domain, establish the three-dimensional models of the remaining solid domain and the fluid domain. The three-dimensional model of the fin is as Figure 3 shown, and the three-dimensional model of the evaporator is as Figure 4 shown. In other embodiments, it is also possible to select to stretch the entire closed area formed by the simplified boundary and the equidistant boundary, and the stretching height can also be other values.

[0103] Step 7: Import the three-dimensional model established in Step 6 into computational fluid dynamics software for simulation analysis: Apply a constant temperature boundary condition to the inner wall of the tube, and specify a constant mass flow rate and inlet temperature for the entire design domain inlet.

[0104] Step 8: According to the simulation results of Step 7, determine whether the outlet temperature and inlet pressure of the evaporator after optimizing the fins meet the requirements. If the results meet the requirements, the design is completed. If not, repeat Steps 3-7 until the requirements are met.

[0105] The effectiveness of the method for optimizing the continuous fins of a refrigerator evaporator according to the present invention is reflected by the following comparison of simulation results:

[0106] 1) Simulation parameters

[0107] Reference Figure 5 , for the evaporator with flat fins 3, the dimensions of the three-dimensional model for comparative calculation are 297 mm * 25 mm * 10 mm, with a total of 7 rows of tubes, the tube wall thickness is 0.75 mm, the tube pitch is 20 mm, the fin thickness is 0.15 mm, and the fin width is 25 mm. The temperature T e of the inner wall of the tube is 253.15 K, the fluid inlet temperature T in is 273.15 K, the inlet mass flow rate is 0.0184 kg / min, the static pressure at the outlet is 0 Pa, the solid material is aluminum, and the fluid is air.

[0108] 2) Simulation results and content

[0109] Using the above simulation parameters for Figure 4 the structure of the evaporator with optimized continuous fins shown in Figure 5 and the structure of the evaporator with flat fins shown in

[0110]

[0111] Numerical simulation is carried out. The comparison of the heat dissipation performance of the two evaporator structures is shown in Table 1:

[0112] It can be seen from Table 1 that after adopting topological optimization of the fins, under the same boundary conditions, the outlet temperature of the model decreases by 2.82 K, the heat transfer coefficient increases by 22.14%, and the pressure drop only increases by 1.66%. Without increasing the volume of the evaporator and hardly increasing the pump work, the heat transfer capacity of the evaporator has a significant improvement.

[0113] The present invention also discloses a refrigerator evaporator, including fins, and a plurality of evaporator round tubes 2 and protrusions 12 provided on the fins, and the protrusions are obtained according to the above method for optimizing the continuous fins of the refrigerator evaporator.

[0114] In this embodiment, the evaporator round tubes 2 are arranged at intervals with the protrusions. Preferably, the evaporator round tubes are arranged in a row. Of course, they can also be arranged in multiple rows.

[0115] The method of the present invention establishes a two-dimensional geometric model of the evaporator according to the geometric characteristics and working conditions of the evaporator to be optimized, determines the design domain, uses the Darcy seepage model to describe the fluid flow, selects the maximum heat absorption of the solid domain as the objective function, obtains the two-dimensional topology optimization result of the fin, simplifies and stretches the solid boundary of the two-dimensional result to obtain the three-dimensional geometric model of the rest of the original fin and the tube, and verifies it; reduces the dependence on the experience of designers, avoids using complex turbulent topology optimization models to optimize large Reynolds number conditions, and greatly improves the optimization efficiency of the refrigerator evaporator; and using the evaporator obtained by this method in the refrigerator can increase the volume ratio of the refrigerator.

[0116] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for optimizing continuous fins of a refrigerator evaporator, characterized in that, Including: Step 1. According to the original evaporator model and the expected overall dimensions of the optimized evaporator, simplify the three-dimensional original evaporator model into a two-dimensional original evaporator model, and establish an evaporator two-dimensional geometric model for topology optimization through the two-dimensional original evaporator model. The evaporator two-dimensional geometric model includes the number of tube rows N, the tube flow direction spacing S L , the tube transverse spacing S W , the inlet width W, the length L, the outer diameter D1 of the tube, the inlet and outlet positions, and the design domain range; Step 2: Determine the inlet velocity v of the gas side of the evaporator according to the working environment of the refrigerator evaporator in , the inlet temperature T of the gas side of the evaporator in , the wall temperature T e , and the physical property parameters of the fluid and solid materials; Step 3: According to the fluid flow control equation, constraint conditions, construct an objective function, and establish an evaporator topology optimization model; Step 4: Solve the evaporator topology optimization model; Step 5: According to the solution result of Step 4, obtain the two-dimensional topology optimization result of the fin; Step 6: Import the two-dimensional topology optimization result of the fin obtained in Step 5 into the graphical design software, simplify the solid boundary using spline curves, and stretch the simplified boundary into a protrusion with the same thickness as the original fin and a height of 1 / 5 - 3 / 4 of the original fin pitch, and establish a three-dimensional geometric model of the remaining part of the original fin and the tube; Step 7: Import the three-dimensional geometric model established in Step 6 into the computational fluid dynamics software for simulation calculation: Apply a constant temperature boundary condition to the inner wall of the tube, and give a constant mass flow rate and inlet temperature at the inlet of the entire design domain; Step 8: According to the simulation calculation result in Step 7, judge whether the outlet temperature and inlet pressure of the evaporator after optimizing the fin meet the requirements. If they meet, obtain the optimized evaporator fin; if not, repeat Steps 3 - 7 until the requirements are met.

2. The method for optimizing continuous fins of a refrigerator evaporator according to claim 1, characterized in that, In the said Step 1, the two-dimensional geometric model of the evaporator further includes a second tube outer diameter D2 concentric with the tube outer diameter D1, and D2 > D1. Set the fin position outside the D2 annular region as the design domain.

3. The method for optimizing continuous fins of a refrigerator evaporator according to claim 1, characterized in that, The physical property parameters of the fluid and solid materials include: thermal conductivity, constant pressure heat capacity, dynamic viscosity, and density.

4. The method for optimizing continuous fins of a refrigerator evaporator according to claim 3, characterized in that, The thermal conductivity of the fluid and solid materials in the design domain is obtained by the following formula: Among them, λ(γ) is the thermal conductivity interpolation function, λ f is the fluid thermal conductivity, λ s is the solid thermal conductivity, q λ is the convex factor of the thermal conductivity, and γ is the design variable.

5. The method for optimizing continuous fins of a refrigerator evaporator according to claim 1, characterized in that, In the said Step 3, establishing the evaporator topology optimization model specifically includes: (3a). Describe the fluid flow in the design domain, determine the fluid flow control equation, and the specific fluid flow control equation is as follows: κ(γ) = κ s + (κ f - κ s )γ 3 ; where, u is the fluid velocity, κ(γ) is the permeability interpolation function, μ is the dynamic viscosity of the fluid, is the pressure gradient within the design domain, κ s is the solid permeability, κ f is the permeability of the fluid working medium; (3b). Constrain the pump work on the gas side of the evaporator and specify the pump work P at the inlet of the two-dimensional geometric model of the evaporator in , which is listed as follows: ∫ Γ pdΓ ≤ P in ; Among them, P in is the inlet pump power, p is the pressure at each point, and Г is the inlet boundary; (3c). Construct an objective function, select the maximum heat absorption in the solid domain as the target, and list the formula as follows: Among them, obj is the objective function; Ω is the design domain, h q is the heat extraction coefficient, q h is the heat extraction convex factor, T is the temperature at each point in the design domain, T e is the refrigerant evaporation temperature; (3d). According to Steps (3a) to (3c), construct the topology optimization criterion with the following formula: find γ ∫ Γ pdΓ ≤ P in ; ∫ Ω γ dΩ ≥ V min ; 0 ≤ γ ≤ 1; Among them, T is the temperature at each point, ρ is the density, C p is the heat capacity at constant pressure, V min is the volume fraction limit value.

6. The continuous fin optimization method for a refrigerator evaporator according to claim 5, wherein, The solid permeability κ s and the fluid working medium permeability κ f are determined by the following method: Establish a model that includes both the solid domain and the fluid domain. Among them, the fluid domain includes at least one bend. Given the boundary conditions to make it a fluid-solid conjugate heat transfer model, and use the turbulence model for calculation to obtain the velocity field, pressure distribution, and temperature field; Set different permeabilities for the solid domain and the fluid domain in the model including the solid domain and the fluid domain, and all use the Darcy seepage model for calculation; Compare the results obtained by the Darcy seepage model with the results obtained by the turbulence model. If the temperature and velocity distributions are close, determine to select the current set permeability value for subsequent optimization; If not, adjust the permeability until it is close to the calculation result of the turbulence model, and the set permeability at this time is the permeability used for subsequent optimization.

7. The continuous fin optimization method for a refrigerator evaporator according to claim 5, wherein, In the said Step 4, the process of solving the evaporator topology optimization model specifically includes: (4a). Mesh the design domain; (4b). When solving the topology optimization, if the difference between the design variables in two consecutive iterations does not exceed 10 -5 , it is considered to be convergent; (4c). Filter and project the design variables. At the beginning of the calculation, select a smaller projection slope β, and gradually increase the projection slope β during the calculation process. Its expression is as follows: Among them, γ c is the original design variable, r is the filtering radius, γ f is the filtered design variable, β is the projection coefficient, γ β is the projection point threshold.

8. The continuous fin optimization method for a refrigerator evaporator according to claim 1, wherein, In the said Step 6, when stretching the simplified boundary, the stretching range of any closed-loop solid domain can be 1 / 5 - 1 of the edge of the solid domain corresponding to the result of Step 5.

9. A refrigerator evaporator, wherein, It includes fins, and a plurality of evaporator round tubes and protrusions arranged on the fins. The protrusions are formed by stretching according to the continuous fin optimization method of the refrigerator evaporator described in any one of claims 1-8.

10. The refrigerator evaporator according to claim 9, wherein, The plurality of evaporator round tubes are arranged at intervals with the protrusions, and the evaporator round tubes are arranged in one row or multiple rows.

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