Structural design method of high-pressure brazing plate type air cooler for transcritical CO2 heat pump

Abstract

The invention belongs to the technical field of transcritical CO2 heat pumps, and particularly relates to a structural design method of a high-pressure brazing plate type air cooler for a transcritical CO2 heat pump. The invention provides a structure design method which is based on the classical strength theory and considers the corrugation depth, the corrugation pitch, the corrugation curve and the sheet thickness in a cooperative mode, a calculation model is simplified, and meanwhile, a stainless steel sheet pressure fatigue checking criterion based on a finite element analysis design method is further provided. And the high-reliability structural design of the high-pressure brazing plate type air cooler is realized. Through the implementation of the design method, the precise design of the product can be realized to a certain extent, and the manufacturing cost of the product is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of transcritical CO2 heat pumps, and in particular relates to a structural design method of a high-pressure brazed plate-type air cooler for a transcritical CO2 heat pump. Background Art

[0002] Carbon dioxide (CO2), as a natural working fluid, has very good thermodynamic properties and is a potential alternative environmentally friendly working fluid. The transcritical CO2 heat pump system uses CO2 as a refrigerant. Through the CO2 transcritical reverse Carnot cycle of "compression-heat release-decompression-heat absorption-recompression", it can obtain high-quality heat sources (produce high-temperature hot water or water vapor) while refrigerating, and quickly refrigerate and heat with a large temperature difference. If this technology is used in the industrial field, waste heat can be converted into energy, replacing high-energy-consuming equipment such as boilers, saving energy and reducing carbon emissions, and achieving the goal of zero energy consumption, zero cost, and zero emissions at the heating end of the upgrade of low-grade industrial waste heat, that is, electrification of heating. Therefore, transcritical CO2 heat pump technology has great potential in promoting the utilization and conversion of energy.

[0003] At present, my country has achieved the commercialization of some small and medium-sized CO2 heat pump systems, but they are mainly used in household or commercial fields such as CO2 heat pump water heaters, CO2 heat pump drying, automotive air conditioning and refrigeration units. There is still little research and development of large-scale megawatt-level transcritical CO2 heat pump systems in the industrial field. In general, due to the low critical temperature (31.1℃) and high critical pressure (7.39MPa) of CO2, its technical threshold is high and the manufacturing cost of the device is high, which limits its large-scale application. In particular, for the key core equipment in the system-high-pressure CO2 air cooler, due to its high working pressure (up to 14MPa), complex heat transfer mechanism (CO2 physical properties change dramatically in the pseudo-critical zone), and high compactness requirements, the equipment is difficult to develop.

[0004] Diffusion-welded plate heat exchangers have the advantage of being able to withstand high temperatures and high pressures at the same time, but their high manufacturing costs limit their widespread application. Although the pressure-bearing capacity of brazed plate heat exchangers is relatively weak, they have compact structures, high heat exchange efficiency, small pressure drop, high production efficiency, and low cost, making them more suitable for the application of transcritical CO2 heat pump high-pressure air coolers.

[0005] However, the products currently produced by my country's brazed plate heat exchanger manufacturers are mainly for Freon units (maximum design pressure of about 5MPa), and they are still unable to break through the design pressure of 14MPa for refrigeration brazed plate heat exchangers. There are no mature domestic high-pressure brazed plate CO2 air cooler products on the market. In addition, some products (such as Alfa LavalAXP27, Alfa Laval AXP52, Alfa LavalAXP112, Kelvion GBH-HP series, SWEP B16DW, etc.) use external frame plate structures to achieve higher product bearing pressures, but this design violates the design concept of high manufacturing efficiency, compact structure and light weight of fully brazed plate heat exchangers; and it is not advisable to focus too much on improving the structural strength of the product and simply increase the thickness of the plate and the thickness of the brazing material.

[0006] Therefore, according to the special requirements of the high-pressure brazed plate air cooler structure, providing a new and complete high-pressure brazed plate air cooler structure design method is an important link in the commercialization process of transcritical CO2 heat pump technology and equipment. Summary of the invention

[0007] The present invention is to solve the above problems and provides a structural design method for a high-pressure brazed plate air cooler for a transcritical CO2 heat pump.

[0008] The present invention adopts the following technical solutions: A structural design method for a high-pressure brazed plate air cooler for a transcritical CO2 heat pump, wherein a plurality of herringbone corrugated plates are alternately stacked in reverse, and the crests of adjacent corrugated plates are brazed to form a design area of ​​the high-pressure brazed plate air cooler; the corrugation angle in the herringbone corrugated plate is defined as β , the distance between the centers of two adjacent wave peaks of the corrugation, that is, the corrugation pitch is p , the vertical distance between the crest and trough of a single herringbone corrugated plate, i.e. the corrugation depth, is b , the vertical distance from the top to the bottom of a single herringbone corrugated plate, i.e. the thickness of the plate, is t ; The space formed by the troughs of adjacent corrugated plates after brazing is defined as a load-bearing unit. The orthographic projection area of ​​the load-bearing unit is A s The solder attachment area in the orthographic projection area is A t ; The design methodology includes the following steps: S1. According to experience, the corrugation pitch is set to p The solder attachment area is calculated according to the following formula A t The minimum value of the solder attachment area is obtained l; ; ; ; Where, P is the design pressure, P≥14MPa; It is the allowable stress of the brazing joint material between two adjacent corrugated plates, in MPa; S2. Set the corrugation depth based on experience b The plate thickness is calculated based on the strength design theory of the elliptical head of the pressure vessel. t Current value of t m : ; ; In the formula is the allowable stress of the plate material at the design temperature, K is the shape coefficient of the elliptical head, which is determined according to Table 7-1 of GB / T 150.3-2024; S3. Set the plate thickness based on experience t The range of [t min ,t max ],like t m ∈[t min ,t max ], then fix the current corrugation pitch p , Corrugation Depth b and plate thickness t m Otherwise, adjust the corrugation pitch p and / or corrugation depth b until the value of t m ∈[t min ,t max ]; S4. Based on finite element analysis, the design structure is calculated and N Maximum stress amplitude under sub-cyclic pressure fatigue condition S alt1 ; Design based on austenitic stainless steel S - N curve, obtain the S - N In the curve N Allowable stress amplitude S under the cycle alt2 ,like S alt1 ≤S alt2 , then confirm the corrugation pitch p、 Corrugation Depthb , Plate thickness t m The design is completed; if S alt1 >S alt2 , then adjust the corrugation pitch p Or adjust the ripple depth b and plate thickness t m until the value of S alt1 ≤S alt2 , get the confirmed corrugation pitch p、 Corrugation Depth b , Plate thickness t m value to complete the design.

[0009] Preferably, the herringbone corrugated plate is a double-sided corrugated plate, the herringbone corrugations are axisymmetrically arranged, and the axis of symmetry is arranged in the center along the length direction of the plate.

[0010] Preferably, the corrugation pitch p The empirical range is 2.5~5.0 mm, and the corrugation depth b The empirical range is 1.2~1.8 mm.

[0011] Preferably, the value of the allowable stress is determined according to the material properties manual or the technical data provided by the manufacturer; in the step S1, the allowable stress is determined based on the brazing joint material being pure copper T2 or T1 and the operating temperature being 150°C ≤ T ≤200℃; in step S2, the allowable stress is based on the head material being 316L and the working temperature T ≤200℃ value.

[0012] Preferably, in step S3, the thickness of the plate is set t The range of [t min ,t max ]Specifically 0.3mm≤ t ≤0.8mm, and t is a decimal place; the calculated t m The value is rounded up to one decimal place for comparison.

[0013] Preferably, in step S3, the corrugation pitch is adjusted p and / or corrugation depth b The value of either or both can be adjusted at once, the corrugation pitch p The single adjustment range is 0.1 mm, and the corrugation depth b The single adjustment range is 0.05 mm.

[0014] Preferably, in step S4, the calculation S alt The design structure takes 9 adjacent load-bearing units for finite element analysis.

[0015] Preferably, in step S4, when S alt1 >S alt2 When the corrugation depth is kept constant, first find the location of the maximum local stress point in the design structure. If the maximum point is located at the welded joint, b and plate thickness t m No change, only the corrugation pitch is adjusted p To increase the solder spreading area, the corrugation pitch p The single adjustment range is 0.1 mm; otherwise, the corrugation pitch is maintained p No change, adjust the ripple depth b and plate thickness t m , the corrugation depth b The single adjustment range is 0.05 mm, the plate thickness t m The single adjustment range is 0.1 mm.

[0016] The beneficial effects of this application are: This application forms a design method based on failure modes for the pressure-bearing core area of ​​the high-pressure brazed plate air cooler - the corrugated plate heat exchange area. Taking into account the fact that the joint tissue elements do not diffuse significantly when copper brazes stainless steel, and the joint strength is low, the inventor believes that the main failure mode lies in the strength failure of the copper joint and the plastic deformation failure of the stainless steel sheet. On this basis, an analytical calculation method based on classical strength theory is proposed, and the calculation model is simplified, thereby deriving a structural design method that synergistically considers the corrugation depth, corrugation pitch, corrugation curve, and plate thickness. In addition, in view of the current situation that mechanical fatigue failure may occur in high-pressure brazed plate air coolers but has not been widely paid attention to, a stainless steel sheet pressure fatigue verification criterion based on the finite element analysis design method is proposed. Through the above two aspects, a high-reliability structural design of a high-pressure brazed plate air cooler is achieved.

[0017] In addition, through the implementation of this design method, accurate product design is achieved to a certain extent, reducing product manufacturing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the structure of a high-pressure brazed plate air cooler for a transcritical CO2 heat pump involved in this application; Figure 2 This is a schematic diagram of brazing corrugated plates to form a load-bearing unit in this application; Figure 3 This is a schematic diagram of the corrugated plate structure in this application; Figure 4 It is an enlarged side view of the corrugated plate in this application; Figure 5 This is a schematic diagram of the structure of the improved high-pressure brazed plate air cooler for the transcritical CO2 heat pump in this application.

[0019] The meanings of the reference numerals in the figures are as follows: 10-end plate, 11-tube, 12-diceta; 21-herringbone corrugated plate on high pressure CO2 side, 22-herringbone corrugated plate on low pressure water side, 23-carrying unit; 30-corner hole, 31-support reinforcement ring; p- Corrugation pitch, β- Corrugation angle, t-plate thickness, b-corrugation depth. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is described in more detail below in conjunction with the embodiments.

[0021] For ease of understanding, the structure of the high-pressure brazed plate air cooler for the transcritical CO2 heat pump involved in this application is explained. It should be emphasized that the structure of the high-pressure brazed plate air cooler can refer to the structure of the plate heat exchanger on the market. The following is only a general description, not a limitation on the high-pressure brazed plate air cooler.

[0022] See also Figure 1 A high-pressure brazed plate air cooler for a transcritical CO2 heat pump comprises a corrugated plate heat exchange zone and an end plate 10 covering the upper and lower sides of the corrugated plate heat exchanger. The corrugated plate heat exchange zone is formed by alternately stacking herringbone corrugated plates 21 on the high-pressure CO2 side and herringbone corrugated plates 22 on the low-pressure water side in reverse, and the crests of adjacent corrugated plates are brazed and connected. The herringbone corrugated plates 21 on the high-pressure CO2 side and the herringbone corrugated plates 22 on the low-pressure water side have the same structure, both are double-sided corrugated plates, and the herringbone corrugated plates on the plate are arranged symmetrically with the axis of symmetry arranged in the middle along the length direction of the plate. The herringbone corrugation shape on the plate in this application can refer to Fig. 2 in the paper Longo GA, Gasparella A. Heat transfer and pressure drop during HFCrefrigerantvaporisation inside a brazed plate heat exchanger [J]. International Journal of Heat & Mass Transfer, 2007, 50 (25-26): 5194-5203.

[0023] Each corrugated plate is provided with two groups of corner holes 30 arranged symmetrically along the symmetry axis of the herringbone corrugation, and the two groups of corner holes 30 are respectively arranged at both ends of the length direction of the corrugated plate. The corner holes 30 are overlapped in the heat exchange area of ​​the corrugated plate to form a CO2 side fluid channel connected to the high-pressure CO2 side herringbone corrugated plate 21 and a water side fluid channel connected to the low-pressure water side herringbone corrugated plate 22. The corrugated plate heat exchange area is connected to the end plate 10 by brazing, and the end plate 10 is provided with a corresponding pipe 11 connected to the CO2 side fluid channel and the water side fluid channel.

[0024] The corrugated plate heat exchange area is the design area of ​​the high pressure brazed plate air cooler described in this application. The design factors include the center distance between two adjacent corrugated peaks, i.e., the corrugated pitch. p The vertical distance between the crest and trough of a single herringbone corrugated plate is the corrugation depth. b , the vertical distance from the top to the bottom of a single herringbone corrugated plate is the plate thickness t .

[0025] In the structure of high-pressure brazed plate air cooler for transcritical CO2 heat pump, too thick brazing filler metal will make the gap of the welding joint too large. During vacuum brazing in the furnace, the good fluidity of pure copper may affect its gap filling ability, resulting in a cold weld of the brazed joint, thus affecting the structural strength. In addition, the accumulation of excess brazing filler metal reduces the flow area, affects the heat transfer and resistance characteristics, and greatly increases the risk of scaling and clogging when generating high-temperature hot water above 65°C. Therefore, the thickness of the brazing filler metal should be as thin as possible while meeting the brazing requirements.

[0026] In order to facilitate the design, the structure of the high-pressure brazed plate air cooler for transcritical CO2 heat pump was adjusted in the early stage of this application, in which the structural strength, the anti-scaling and clogging of high-temperature hot water and the selection of the brazing material thickness of the welding process were considered in coordination, and the thermal and resistance characteristics of the high-pressure brazed plate air cooler were considered in coordination, and the brazing material thickness and the corrugation angle in the herringbone corrugated plate were adjusted. β Set it to a fixed value and use it by default in the design.

[0027] The method involved in this application is described in detail below. For the convenience of calculation, this application defines the space formed by the troughs of adjacent corrugated plates after brazing as the bearing unit 23, and the orthographic projection area of ​​the bearing unit 23 is A s The solder attachment area in the orthographic projection area is A t ; Then, the design method of the high-pressure brazed plate air cooler structure for a transcritical CO2 heat pump includes the following steps: S1. According to experience, the corrugation pitch is set to pThe solder attachment area is calculated according to the following formula A t The minimum value of the solder attachment area is obtained l ; ; ; ; Where, P is the design pressure, P≥14MPa; The brazing joint material (pure copper T2 or T1) between two adjacent corrugated plates is T (150℃≤ T The allowable stress at ≤200℃ is determined in accordance with GB / T 5231-2012 or the material properties manual or technical data provided by the manufacturer, and the unit is MPa; S2. Set the corrugation depth based on experience b The value of l That is, the flat length of the corrugation crest along the extension direction of the curve. Therefore, when the corrugation depth is determined, the corrugation curve can be determined, so the plate thickness t The plate thickness can be calculated equivalently for the elliptical head of a pressure vessel: the plate thickness is calculated based on the strength design theory of the elliptical head of a pressure vessel (the head material is 316L, and the allowable stress is taken at 200°C). t Current value of t m : ; ; In the formula is the allowable stress of the plate material at the design temperature, K is the shape coefficient of the elliptical head, which is determined according to Table 7-1 of GB / T 150.3-2024; S3. Set the plate thickness based on experience t The range of [t min ,t max ],like t m ∈[t min ,t max ], then fix the current corrugation pitch p and plate thickness t m Otherwise, adjust the corrugation pitch p and / or corrugation depth b until the value of t m ∈[t min ,t max]; In step S3, since the thickness of the finished plate rolled out by the processing plant is generally 0.3 mm, 0.4 mm, ..., 0.8 mm, etc., the plate thickness can be set t The range of [t min ,t max ]Specifically 0.3mm≤ t ≤0.8mm, and t is a decimal place; the calculated t m The value is rounded up to one decimal place for comparison.

[0028] S4. Based on finite element analysis, refer to the fatigue test method in 6.3.5 of "JB / T 8701-2019 Plate Heat Exchanger for Refrigeration", calculate the design structure under the N Maximum stress amplitude under sub-cyclic pressure fatigue condition S alt1 ; Design based on austenitic stainless steel S - N Curve (GB / T 4732.4-2024 page 293 Figure 4 ), obtain the S - N In the curve N Allowable stress amplitude under the cycle S alt2 .

[0029] like S alt1 ≤ S alt2 , then confirm the corrugation pitch p、 Corrugation Depth b , Plate thickness t m The design is completed. like S alt1 > S alt2 First, find the location of the maximum local stress point in the design structure. If the maximum point is located at the weld joint, keep the corrugation depth b and plate thickness t m No change, only the corrugation pitch is adjusted p To increase the solder spreading area; otherwise, keep the corrugation pitch p No change, adjust the ripple depth b and plate thickness t m ; Adjust until S alt1 ≤ S alt2, get the confirmed corrugation pitch p、 Corrugation Depth b , Plate thickness t m value to complete the design.

[0030] In this method, the corrugation pitch p The empirical range is 2.5~5.0 mm, and the corrugation depth b The empirical range is 1.2~1.8mm; adjust the corrugation pitch p and / or the value of corrugation depth b are adjusted one by one or both, and the corrugation pitch is p The single adjustment range is 0.1 mm, and the corrugation depth b The single adjustment range is 0.05 mm, the plate thickness t m The single adjustment range is 0.1 mm.

[0031] In this method, the S alt1 The design structure takes nine adjacent load-bearing units 23 for finite element analysis.

[0032] In a complete design solution, the steps are as follows: High-pressure brazed plate air cooler for a transcritical CO2 heat pump, setting the corrugation angle β It is 120° to increase the number of heat transfer units on the weak heat transfer side (CO2 side).

[0033] S1. According to experience, the corrugation pitch is set to p The value is 4.8 mm, and the solder attachment area is calculated according to the following formula A t The minimum value of the solder attachment area is obtained l ; ; ; ; Where, P is the design pressure, P = 14 MPa; The brazed joint (made of pure copper T2) between two adjacent corrugated plates is T ( T =200℃) is determined in accordance with GB / T 5231-2012 and is expressed in MPa. In this step, the solder attachment area is calculated. A t The minimum value is 5.7 mm 2 , side length of solder attachment area l2.57 mm; S2. Set the corrugation depth based on experience b The value is 1.65 mm. The plate thickness is calculated based on the strength design theory of the elliptical head of the pressure vessel (the head material is 316L, and the allowable stress is taken at 200°C). t Current value of t m : ; ; In the formula is the allowable stress of the plate material at the design temperature, K is the shape coefficient of the elliptical head, which is obtained according to Table 7-1 of GB / T 150.3-2024; in this step, the plate thickness is calculated t m It is 0.51 mm.

[0034] S3. According to experience, the plate thickness is set to 0.3 ≤ t ≤0.8, and t is the tenth decimal place, t m Rounded to 0.6 mm, satisfying t m ∈[t min ,t max ], thus fixing the current corrugation pitch p and plate thickness t m The value of S4. Select 9 load-bearing units 23 in adjacent local areas as the design structure, and calculate the maximum stress amplitude of the design structure under 100,000 cycles of pressure fatigue based on the finite element analysis design method. S alt1 According to the design of austenitic stainless steel S - N curve, obtain the S - N In the curve N The allowable stress amplitude under the cycle is based on S alt2 and S alt1 The relationship between the corrugation pitch p、 Corrugation depth b, plate thickness t m The value of .

[0035] In this design, the maximum stress amplitude in the structure is S alt1184MPa, based on the design of austenitic stainless steel S - N From the curve, we can see that S alt2 =200MPa. S alt1 ≤ S alt2 , which meets the requirements, therefore, the corrugated plate corrugation pitch designed this time p 4.8 mm 、 Corrugation Depth b 1.65 mm, plate thickness t m is 0.6 mm.

[0036] Furthermore, after the design of the corrugated plate heat exchange area is completed, the pressure-bearing weak links of the high-pressure brazed plate air cooler, namely, the pipe 11, the outermost corrugated plate and the corrugated plate corner hole 30, are adaptively adjusted. Figure 5 , wherein the end plate 10 is selected to be thickened, for example, a 2 mm thick plate to increase the brazing area of ​​the pipe. A support reinforcement gasket 31 is added to the edge of the corner hole 30 of the herringbone corrugated plate 21 on the high-pressure CO2 side and / or the herringbone corrugated plate 22 on the low-pressure water side to improve the pressure-bearing capacity of the corrugated plate corner hole 30 area. The material of the support reinforcement gasket 31 is 304 or 316, and its thickness is equal to 2 times the corrugation depth, and a notch is provided for the drainage of CO2 in the corner hole area; the support reinforcement gasket 31 and the corrugated plate sheet are reliably connected by brazing. A turbulent flow structure is also provided in the corrugated plate corner hole 30 area to enhance the pressure-bearing and heat exchange capacity of the corrugated plate corner hole 30 area. The turbulent flow structure is a plurality of groups of irregular-shaped cells 12, and the thickness of the cells 12 is equal to 2 times the corrugation depth.

[0037] Furthermore, the inner diameter of the CO 2 side inlet pipe 11 is adjusted to be larger than the inner diameter of the outlet pipe 11 to match the drastic change in CO 2 density and reduce the flow pressure drop at the corner hole 30 as much as possible.

[0038] verify At present, there is no mature domestic high-pressure fully brazed plate CO2 air cooler product on the market. Taking the brazed plate condenser in a common Freon heat pump unit as an example, the corrugated plate pitch is p 7.5 mm 、 Corrugation Depth b 1.95 mm, plate thickness t m The diameter of the steel pipe is 0.4 mm. Its design pressure is 5 MPa, and its bursting pressure is usually not higher than 20 MPa.

[0039] The transcritical CO2 high pressure brazed plate air cooler developed after redesign of this application scheme has a corrugated plate corrugation angle β120°, corrugation pitch p 2.8 mm 、 Corrugation Depth b 1.4 mm, plate thickness t m The diameter of the pipe is 0.3 mm. After the burst test, the burst pressure reached 50 MPa, which is 3 times greater than the design pressure. In addition, no leakage was found after 100,000 times of pressure fatigue cycle test. All of them have met the requirements of product type test.

[0040] The developed air cooler prototype has undergone explosion tests with a burst pressure of 50 MPa, and no leakage was found after 100,000 pressure fatigue cycle tests.

[0041] The above implementation modes are only used to illustrate the technical solutions of the present invention, but not to limit the present invention. Although the present invention has been described in detail with reference to the above implementation modes, those skilled in the art should understand that any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A structural design method for a high-pressure brazed plate air cooler for a transcritical CO2 heat pump, characterized in that: A plurality of herringbone corrugated plates are alternately stacked in reverse, and the crests of adjacent corrugated plates are brazed to form the design area of ​​the high-pressure brazed plate-type air cooler; the corrugation angle in the herringbone corrugated plate is defined as β , the distance between the centers of two adjacent wave peaks of the corrugation, i.e. the corrugation pitch, is p , the vertical distance between the crest and trough of a single herringbone corrugated plate, i.e. the corrugation depth, is b , the vertical distance from the top to the bottom of a single herringbone corrugated plate, i.e. the thickness of the plate, is t ; The space formed by the troughs of adjacent corrugated plates after brazing is defined as a load-bearing unit. The orthographic projection area of ​​the load-bearing unit is A s The solder attachment area in the orthographic projection area is A t ; The design methodology includes the following steps: S1. According to experience, the corrugation pitch is set to p The solder attachment area is calculated according to the following formula A t The minimum value of the solder attachment area is obtained l ; ； ； ； Where, P is the design pressure, P≥14MPa; It is the allowable stress of the brazing joint material between two adjacent corrugated plates, in MPa; S2. Set the corrugation depth based on experience b The plate thickness is calculated based on the strength design theory of the elliptical head of the pressure vessel. t Current value of t m : ； ； In the formula is the allowable stress of the plate material at the design temperature, K is the shape coefficient of the elliptical head, which is taken according to Table 7-1 of GB / T150.3-2024; S3. Set the plate thickness based on experience t The range of [t min ,t max ],like t m ∈[t min ,t max ], then fix the current corrugation pitch p , Corrugation Depth b and plate thickness t m Otherwise, adjust the corrugation pitch p and / or corrugation depth b until the value of t m ∈[t min ,t max ]; S4. Based on finite element analysis, the design structure is calculated and N Maximum stress amplitude under sub-cyclic pressure fatigue condition S alt1 ; Design based on austenitic stainless steel S - N curve, obtain the S - N In the curve N Allowable stress amplitude S under the cycle alt2 ,like S alt1 ≤S alt2 , then confirm the corrugation pitch p、 Corrugation Depth b , Plate thickness t m The design is completed; if S alt1 >S alt2 , then adjust the corrugation pitch p Or adjust the ripple depth b and plate thickness t m until the value of S alt1 ≤S alt2 , get the confirmed corrugation pitch p、 Corrugation Depth b , Plate thickness t m value to complete the design.

2. The structural design method of a high-pressure brazed plate air cooler for a transcritical CO2 heat pump according to claim 1, characterized in that: The herringbone corrugated plate is a double-sided corrugated plate, the herringbone corrugations are axisymmetrically arranged, and the axis of symmetry is arranged in the center along the length direction of the plate.

3. The structural design method of a high-pressure brazed plate air cooler for a transcritical CO2 heat pump according to claim 1, characterized in that: The corrugation pitch p The empirical range is 2.5~5.0 mm, and the corrugation depth b The empirical range is 1.2~1.8 mm.

4. The structural design method of a high-pressure brazed plate air cooler for a transcritical CO2 heat pump according to claim 1, characterized in that: The value of the allowable stress is determined according to the material performance manual or the technical data provided by the manufacturer; in step S1, the allowable stress is based on the brazing joint material being pure copper T2 or T1 and the operating temperature being 150°C ≤ T ≤200℃; in step S2, the allowable stress is based on the head material being 316L and the working temperature T ≤200℃ value.

5. The structural design method of a high-pressure brazed plate air cooler for a transcritical CO2 heat pump according to claim 1, characterized in that: In step S3, the thickness of the plate is set t The range of [t min ,t max ]Specifically 0.3mm≤ t ≤0.8mm, and t is a decimal place; the calculated t m The value is rounded up to one decimal place for comparison.

6. The structural design method of a high-pressure brazed plate air cooler for a transcritical CO2 heat pump according to claim 3, characterized in that: In step S3, the corrugation pitch is adjusted p and / or corrugation depth b The value of either or both is adjusted at once, the corrugation pitch p The single adjustment range is 0.1 mm, and the corrugation depth b The single adjustment range is 0.05 mm.

7. The structural design method of a high-pressure brazed plate air cooler for a transcritical CO2 heat pump according to claim 1, characterized in that: In step S4, for calculating S alt1 The designed structure takes nine adjacent load-bearing units for finite element analysis.

8. The structural design method of a high-pressure brazed plate air cooler for a transcritical CO2 heat pump according to claim 1, characterized in that: In step S4, when S alt1 >S alt2 When the corrugation depth is kept constant, first find the location of the maximum local stress point in the design structure. If the maximum point is located at the welded joint, b and plate thickness t m No change, only the corrugation pitch is adjusted p To increase the solder spreading area, the corrugation pitch p The single adjustment range is 0.1 mm; otherwise, the corrugation pitch is maintained p No change, adjust the ripple depth b and plate thickness t m , the corrugation depth b The single adjustment range is 0.05 mm, the plate thickness t m The single adjustment range is 0.1 mm.

Images