A calculation method for complex flow channel design of expansion plate heat exchanger

Abstract

This invention discloses a calculation method for the design of complex flow channels in expansion plate heat exchangers, primarily relating to the technical field of centrifuge temperature-controlled heat exchangers. By employing a method consisting of basic theoretical calculation - preliminary design - simulation verification - primary theoretical model correction - experimental verification - secondary theoretical model correction, the invention obtains an engineering calculation formula for complex expansion plate flow channels within a certain range. This method can rapidly calculate the heat transfer coefficient and pressure loss within the flow channels of non-continuous, complex structures. By adjusting the basic geometric parameters of the heat exchanger, the design of efficient expansion plate heat exchanger flow channels can be rapidly completed. The design and iteration process of heat exchangers with complex honeycomb flow channels can also be completed more quickly, saving time and improving efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of centrifuge temperature control heat exchangers, and in particular to a design and calculation method for complex flow channels of an expansion plate heat exchanger. Background Art

[0002] During the operation of a large high-speed centrifuge, the high-speed rotating arm drives the rotational friction of the air inside the centrifuge chamber, causing the air temperature to rise sharply. When it rises to a certain level, it will damage the centrifuge parts or the hanging basket equipment. Therefore, when a large high-speed centrifuge is in operation, it is necessary to consider temperature control methods to remove the heat from the centrifuge in a timely manner. The usual solution is to install a heat exchanger on the inner wall of the centrifuge chamber. The surface of the heat exchanger is in direct contact with the air in the centrifuge chamber. The heat is exchanged through convection between the air and the wall of the heat exchanger, and the heat is transferred to the heat exchanger. The coolant flowing inside the heat exchanger then removes the heat to the cooling unit outside the centrifuge chamber, completing the heat transfer in the machine room.

[0003] Because large, high-speed centrifuges generate enormous amounts of heat, reaching megawatts, maintaining the air temperature inside the centrifuge chamber below 40°C requires a heat exchanger with high heat transfer efficiency. While the typical approach is to increase the heat transfer area between the hot and cold sides of the heat exchanger, the surface of the heat exchanger facing the centrifuge must be smooth and continuous to ensure a continuous aerodynamic boundary within the chamber while the centrifuge rotates. This requires significantly improving the heat transfer efficiency within the heat exchanger and reducing the thermal resistance. Using an advanced honeycomb flow channel expansion plate heat exchanger can effectively improve this internal heat transfer efficiency.

[0004] The honeycomb flow channel expansion plate heat exchanger is manufactured using a laser welding bulging forming process. After design and pre-arrangement of welding points, two pieces of stainless steel plates are welded into shape through an automatic laser welding process, and then the designed flow channel is formed through a hydraulic bulging forming process. Since the internal wall of the heat exchanger is covered with flow channels, all the wall surfaces can be exposed to the coolant, making the entire heat exchanger wall surface have a lower temperature. The honeycomb-shaped flow channel causes the flow cross-section of the fluid medium to change continuously during the flow process, and the flow is disturbed, which greatly improves the convective heat transfer coefficient. However, due to the very complex structure of the honeycomb flow channel, the traditional heat exchange correlation cannot be applied to this structure. In conventional design, it is necessary to use CFD numerical simulation technology to analyze, calculate and predict the flow field inside the heat exchanger.

[0005] The CFD numerical simulation method is to establish a geometric model of the heat exchanger, use fluid mechanics theory, heat transfer principles and finite element method to conduct numerical analysis of the heat transfer and flow performance of the heat exchanger, optimize the heat exchanger structure according to the calculation results, and after several rounds of iterations, obtain the optimal design parameters of the heat exchanger flow channel.

[0006] Because CFD numerical simulation technology has high computer requirements and long calculation cycles, multiple iterations are required during design and optimization. Design methods relying on CFD numerical simulation are extremely energy-consuming and time-consuming, and cannot meet the requirements of rapid iterative design. How to quickly design, calculate, and analyze the complex flow paths of heat exchangers is a problem that needs to be solved. Summary of the Invention

[0007] The purpose of the present invention is to provide a calculation method for designing complex flow channels of a high-heat-flux and high-efficiency expansion plate heat exchanger for a large high-speed centrifuge, so as to solve the problem of quickly designing the complex flow channels of the heat exchanger.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A calculation method for designing complex flow channels of an expansion plate heat exchanger includes the following steps:

[0010] S1. Determine the heat load per unit area and basic structure of the heat exchanger based on the heat output and basic structure of the large high-speed centrifuge;

[0011] S2. Calculate the equivalent hydraulic diameter of the expansion plate flow channel, and use the internal forced convection heat exchanger correlation formula and resistance coefficient calculation formula to calculate the heat exchanger coefficient and along-the-line resistance in the expansion plate flow channel;

[0012] S3. Adjust the basic structural parameters of the heat exchanger expansion plate to obtain the optimal match between the heat transfer coefficient and the flow resistance. When the flow resistance is within a reasonable range, the heat transfer coefficient meets the use requirements, thus completing the preliminary design of the heat exchanger flow channel.

[0013] S4. Based on the preliminary design, perform 3D modeling of the geometric structure, mesh it, and import it into CFD calculation software for simulation calculation to obtain the temperature distribution, heat transfer coefficient, and pressure loss inside the heat exchanger;

[0014] S5. Perform the first revision of the theoretical model based on the results of CFD calculation. The main revised parameter is the equivalent height of the heat exchanger expansion plate flow channel to ensure the rationality of the theoretical calculation.

[0015] S6. Produce a heat exchanger expansion plate test piece that is consistent with the preliminary design, and conduct heat transfer and flow tests on the heat exchanger. The test boundary conditions are completely consistent with the design conditions.

[0016] S7. After obtaining the test results, perform data processing and analysis on the test results and make a second revision to the theoretical model;

[0017] S8. The theoretical calculation formula obtained through the above steps can quickly calculate the heat transfer coefficient and pressure loss of the internal flow channel of the discontinuous complex structure. By adjusting the basic geometric parameters of the heat exchanger, the design of the flow channel of the high-efficiency expansion plate heat exchanger can be quickly completed.

[0018] Preferably, the basic structure of the heat exchanger in step S1 includes the length and width of the heat exchanger unit and the bending form of the expansion plate flow channel.

[0019] Preferably, the test boundary conditions in step S6 include the heat load per unit area of ​​the heat exchanger, the flow rate of the medium inside the heat exchanger, the medium inside the heat exchanger, and the adiabatic boundary of the heat exchanger.

[0020] Preferably, the correction in step S7 mainly adjusts the safety factor during design to ensure that sufficient safety margin is left during the engineering design process.

[0021] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0022] 1. This application obtains the engineering calculation formula for complex expansion plate flow channels within a certain range by adopting the method of basic theoretical calculation-preliminary design-simulation verification-theoretical model primary correction-experimental verification-theoretical model secondary correction. It can quickly calculate the heat transfer coefficient and pressure loss of the internal flow channels of non-continuous complex structures. By adjusting the basic geometric parameters of the heat exchanger, the design of the flow channels of high-efficiency expansion plate heat exchangers can be quickly completed, and the design and iteration process of complex honeycomb flow channel heat exchangers can be completed more quickly, saving time and improving efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A flowchart of a calculation method for designing complex flow channels of an expansion plate heat exchanger according to an embodiment of the present invention is shown;

[0024] Figure 2 A schematic diagram of the bending of the internal flow channel of the heat exchanger provided in an embodiment of the present invention is shown;

[0025] Figure 3 A schematic diagram of a honeycomb flow channel according to an embodiment of the present invention is shown;

[0026] Figure 4 A schematic diagram of a three-dimensional model of a heat exchanger unit provided in an embodiment of the present invention is shown;

[0027] Figure 5 A schematic diagram of simulation results of a heat exchanger unit provided according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0029] See also Figure 1-5 , the present invention provides a technical solution:

[0030] A calculation method for designing complex flow channels of an expansion plate heat exchanger includes the following steps:

[0031] S1. Determine the heat load per unit area and basic structure of the heat exchanger based on the heat output and basic structure of the large high-speed centrifuge;

[0032] S2. Calculate the equivalent hydraulic diameter of the expansion plate flow channel, and use the internal forced convection heat exchanger correlation formula and resistance coefficient calculation formula to calculate the heat exchanger coefficient and along-the-line resistance in the expansion plate flow channel;

[0033] S3. Adjust the basic structural parameters of the heat exchanger expansion plate to obtain the optimal match between the heat transfer coefficient and the flow resistance. When the flow resistance is within a reasonable range, the heat transfer coefficient meets the use requirements, thus completing the preliminary design of the heat exchanger flow channel.

[0034] S4. Based on the preliminary design, perform 3D modeling of the geometric structure, mesh it, and import it into CFD calculation software for simulation calculation to obtain the temperature distribution, heat transfer coefficient, and pressure loss inside the heat exchanger;

[0035] S5. Perform the first revision of the theoretical model based on the results of CFD calculation. The main revised parameter is the equivalent height of the heat exchanger expansion plate flow channel to ensure the rationality of the theoretical calculation.

[0036] S6. Produce a heat exchanger expansion plate test piece that is consistent with the preliminary design, and conduct heat transfer and flow tests on the heat exchanger. The test boundary conditions are completely consistent with the design conditions.

[0037] S7. After obtaining the test results, perform data processing and analysis on the test results and make a second revision to the theoretical model;

[0038] S8. The theoretical calculation formula obtained through the above steps can quickly calculate the heat transfer coefficient and pressure loss of the internal flow channel of the discontinuous complex structure. By adjusting the basic geometric parameters of the heat exchanger, the design of the flow channel of the high-efficiency expansion plate heat exchanger can be quickly completed.

[0039] Specifically, the basic structure of the heat exchanger in step S1 includes the length, width and bending form of the expansion plate flow channel of the heat exchanger unit; the test boundary conditions in step S6 include the heat load per unit area of ​​the heat exchanger, the flow rate of the medium inside the heat exchanger, the medium inside the heat exchanger and the insulation boundary of the heat exchanger; the correction in step S7 mainly adjusts the safety factor during the design to ensure that sufficient safety margin is left during the engineering design process.

[0040] The specific implementation is as follows:

[0041] a. The large high-speed centrifuge heat exchanger has a diameter of 15m and is divided into 30 heat exchanger units in the circumferential direction. The maximum heating capacity is 1933kW and the total heat exchange area of ​​the heat exchanger is 215m 2 , the heat load per unit area of ​​the heat exchanger is 8990W / m 2 , given that the refrigerant flow rate inside the heat exchanger is 220m 3 / h. The heat exchanger unit width is 1415mm, height is 4900mm, the heat exchanger flow channel bending form can be two fold or four fold form, the specific structure is as follows Figure 2 As shown;

[0042] b. Calculate the equivalent hydraulic diameter of the expansion plate flow channel according to formula (1), where a represents the actual flow channel width and b represents the effective flow channel height. Figure 3 As shown in the figure, since the internal flow channel of the expansion plate structure is an unconventional structure, according to engineering experience, the effective height of the honeycomb flow channel is generally 0.2 to 0.6 times the maximum height of the expansion plate flow channel.

[0043]

[0044] Calculate the drag coefficient according to Filonenko's formula:

[0045] f=(1.82lgRe-1.64) -2

[0046] Calculate the convective heat transfer coefficient according to the Gnielinski formula:

[0047]

[0048] According to the above results, the heat exchanger's along-the-line resistance and convection heat transfer coefficient can be calculated;

[0049] c. Adjust the basic structural parameters of the heat exchanger expansion plate to obtain the optimal match between the heat transfer coefficient and the flow resistance. This ensures that the heat transfer coefficient meets the requirements while the flow resistance is within a reasonable range, thus completing the preliminary design of the heat exchanger flow channel.

[0050] d. According to the preliminary design, carry out three-dimensional modeling of the geometric structure, such as Figure 4As shown. It is imported into ICEM software for meshing. Taking into account the complex internal structure of the heat exchanger, unstructured mesh generation technology is adopted. The unit form is mainly hexahedral units, including wedge units. Through the inspection of the mesh quality inspection tool in ICEM, the mesh of the entire model is good and meets the calculation requirements. The control equation is discretized according to the divided calculation grid and the generated calculation nodes, and the model is simulated and calculated in combination with the given boundary conditions. The calculation software uses Fluent, the calculation turbulence model uses the Realizablek-ε model, the pressure-velocity coupling uses the Simple algorithm, and the discretization of each parameter uses the second-order accuracy upwind scheme. The judgment standard for solution convergence is the relative residual. There are four boundary conditions in the calculation, namely the inlet boundary condition, the outlet boundary condition, the inner wall boundary condition and the outer wall boundary condition. When performing the simulation, the velocity inlet and free outlet flow boundary conditions are used, and the inlet velocity and temperature are set as needed; the inner wall and outer wall boundary conditions are set as no-slip velocity boundary conditions, and the temperature distribution obeys the constant heat flow condition. After multiple iterations, the calculation converges and the simulation calculation process is completed. The results are as follows Figure 5 As shown, the temperature distribution, heat transfer coefficient and pressure loss inside the heat exchanger are obtained;

[0051] e. Based on the simulation results, the theoretical model was revised for the first time. The main parameter revised was the equivalent height of the heat exchanger expansion plate flow channel. The equivalent height coefficient was adjusted to 0.35, and the theoretical pressure loss was 1.5 times the theoretical pressure loss along the path. After the adjustment, the error between the theoretical calculation and the simulation calculation was within 20%;

[0052] f. Produce a heat exchanger expansion plate test piece consistent with the preliminary design and conduct heat transfer and flow tests on the heat exchanger. The test boundary conditions are completely consistent with the design conditions. The test heat load is simulated using the equivalent heat flow method, using the radiant heat emitted by the infrared lamp array to simulate the heat generated by the gas inside the centrifuge;

[0053] g. After obtaining the test results, the test results were processed and analyzed, and the theoretical model was revised for the second time. After the revision, the safety factor was 1.6;

[0054] h. Obtained the formula for calculating the pressure loss of the internal flow of a high-heat-flux, high-efficiency expansion plate heat exchanger and the formula for calculating the coefficient of a convection heat exchanger, and applied them to the design and calculation of other types of centrifuge heat exchangers.

[0055] This application obtains the engineering calculation formula for complex expansion plate flow channels within a certain range by adopting the method of basic theoretical calculation-preliminary design-simulation verification-theoretical model primary correction-experimental verification-theoretical model secondary correction. It can quickly calculate the heat transfer coefficient and pressure loss of the internal flow channels of non-continuous complex structures. By adjusting the basic geometric parameters of the heat exchanger, the design of the flow channels of high-efficiency expansion plate heat exchangers can be quickly completed, and the design and iteration process of complex honeycomb flow channel heat exchangers can be completed more quickly, saving time and improving efficiency.

[0056] The above description of the embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A calculation method for designing complex flow channels of an expansion plate heat exchanger, characterized in that: The following steps are involved: S1. Determine the heat load per unit area and basic structure of the heat exchanger based on the heat output and basic structure of the large high-speed centrifuge; S2. Calculate the equivalent hydraulic diameter of the expansion plate flow channel, and use the internal forced convection heat exchanger correlation formula and resistance coefficient calculation formula to calculate the heat exchanger coefficient and along-the-line resistance in the expansion plate flow channel; S3. Adjust the basic structural parameters of the heat exchanger expansion plate to obtain the optimal match between the heat transfer coefficient and the flow resistance. When the flow resistance is within a reasonable range, the heat transfer coefficient meets the use requirements, thus completing the preliminary design of the heat exchanger flow channel. S4. Based on the preliminary design, perform 3D modeling of the geometric structure, divide the mesh into three dimensions, and import the model into CFD calculation software for simulation calculation to obtain the temperature distribution, heat transfer coefficient, and pressure loss inside the heat exchanger. S5. Perform the first revision of the theoretical model based on the results of CFD calculation. The main revised parameter is the equivalent height of the heat exchanger expansion plate flow channel to ensure the rationality of the theoretical calculation. S6. Produce a heat exchanger expansion plate test piece that is consistent with the preliminary design, and conduct heat transfer and flow tests on the heat exchanger. The test boundary conditions are completely consistent with the design conditions. S7. After obtaining the test results, perform data processing and analysis on the test results and make a second revision to the theoretical model; S8. The theoretical calculation formula obtained through the above steps can quickly calculate the heat transfer coefficient and pressure loss of the internal flow channel of the discontinuous complex structure. By adjusting the basic geometric parameters of the heat exchanger, the design of the flow channel of the high-efficiency expansion plate heat exchanger can be quickly completed.

2. A calculation method for designing complex flow channels of an expansion plate heat exchanger according to claim 1, characterized in that: The basic structure of the heat exchanger in step S1 includes the length and width of the heat exchanger unit and the bending form of the expansion plate flow channel.

3. The calculation method for designing complex flow channels of an expansion plate heat exchanger according to claim 1, characterized in that: The test boundary conditions in step S6 include the heat load per unit area of ​​the heat exchanger, the flow rate of the medium inside the heat exchanger, the medium inside the heat exchanger, and the adiabatic boundary of the heat exchanger.

4. The design and calculation method for complex flow channels of an expansion plate heat exchanger according to claim 1, characterized in that: The correction in step S7 mainly adjusts the safety factor during design to ensure that sufficient safety margin is left during the engineering design process.

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