Flow characteristic prediction method for pump-driven two-phase fluid heat dissipation system

Abstract

The invention discloses a flow characteristic prediction method for a pump-driven two-phase fluid heat dissipation system. Relates to the field of spaceflight, in particular to a pump-driven two-phase fluid heat dissipation system flow characteristic prediction method. The dynamic characteristics of a working medium in the operation process of the two-line fluid heat dissipation system of the spacecraft are calculated, the system working state point of the two-phase system is calculated, the matching property of the driving pump and the pump-driven two-phase fluid heat dissipation system is verified before the system is built, and the flow characteristics of the pump-driven two-phase fluid heat dissipation system are predicted. The method comprises the following steps that the working medium flow in a two-phase state is estimated; drawing a system single-phase flow-flow resistance characteristic curve; calculating a two-phase limit working point of the system; selecting a model of a driving pump; drawing and evaluating the matching between the driving pump and the fluid system; according to the method, the flow characteristics of the two-phase system and the working characteristics of the driving pump are speculated in the modes of testing, calculation and the like, the actual working state point of the driving pump is predicted, the matching performance of the driving pump and the fluid system is verified in a mapping mode, and design blind spots are reduced.

Description

Technical Field

[0001] This invention relates to the aerospace field, and more specifically to a method for predicting the flow characteristics of a pump-driven two-phase fluid heat dissipation system. Background Technology

[0002] The pump-driven two-phase fluid cooling system is an active thermal control technology for addressing the high-power, high-heat-fluid-density heat dissipation problem of spacecraft. It uses a driving pump to circulate the working fluid in a closed loop, absorbing heat through phase change at the heat source and dissipating heat at the cold source, thus achieving efficient heat transfer by utilizing the high latent heat of phase change of the working fluid. During the development of this system, the matching of the drive pump and the system loop is a difficult problem in the design stage for the following reasons: (1) The two-phase fluid loop exchanges heat through the gas-liquid phase change process and should be matched with a small flow-high head drive pump. At present, it is usually difficult to match the operating point of the system with the rated operating condition of the drive pump. That is, the drive pump actually works at a speed far below the rated operating condition. For centrifugal pumps, this operating state is prone to the flow rate returning to zero due to the instantaneous increase of system flow resistance; (2) Based on the operating temperature of the internal components of the spacecraft, the circulating working fluid of the corresponding two-phase system is usually in the gaseous state at normal pressure, which makes it difficult to use the corresponding working fluid to measure the flow-head characteristics of the drive pump; (3) Before and after the heat source is started, the state of the working fluid in the evaporator, condenser and other places of the two-phase fluid heat dissipation system changes from single phase to two phase. The system resistance-flow curve changes dynamically, resulting in the system flow rate being non-fixed. This undoubtedly increases the difficulty of determining the flow state of the system.

[0003] Currently, spacecraft employing fluid cooling primarily utilize pump-driven single-phase fluid cooling systems. These systems offer advantages such as simplicity, reliability, and easier analysis of internal flow states during the design phase. However, they often fail to meet stringent design requirements when facing high-power, high-heat-fluid-density heat sources. Since a two-phase fluid cooling system with the heat source off can be considered a low-flow-rate single-phase fluid system, this patent builds upon this foundation to analyze key parameter changes during the transition of the working fluid from single-phase to two-phase. This analysis predicts the actual operating point of the driving pump, reducing design blind spots in pump-driven two-phase fluid cooling systems before system construction and preventing mismatches between the driving pump and the fluid system.

[0004] Chinese invention patent applications “Vacuum-liquid separation type liquid storage tank and its self-adaptive temperature control mechanical pump driven two-phase fluid loop system” (CN202510284398.4), “A pump driven two-phase fluid temperature control device” (CN202420286365.4), “Two-phase fluid loop system for spacecraft heat dissipation” (CN202310382874.7), and “Temperature control device and pump driven two-phase fluid loop system” (CN202011099820.2) all describe the system composition and basic principle of innovative two-loop systems, but do not involve the detailed design of internal parameters.

[0005] Chinese invention patent application "A Pump-Driven Two-Phase Fluid Circuit and Design Method for High-Temperature Heat Dissipation in a Fixed Planar Region" (CN202510789325.0) proposes methods for calculating the flow resistance in single-phase and two-phase regions of the system and methods for selecting the drive pump. However, it has the following problems: (1) The calculation of the system flow resistance includes parameters such as the working fluid mass flow rate and velocity. These parameters are related to the resistance-flow characteristics of the drive pump and the system, i.e., they are coupled with each other, making it impossible to conduct detailed design based on the patent; (2) The patent states that the maximum flow resistance that the drive pump can overcome should be greater than the system flow resistance. This statement lacks a definition of the minimum flow rate of the system, i.e., the flow rate driven by the drive pump at the operating point of the system flow resistance should be able to meet the system's heat dissipation requirements. This statement is not reflected in the patent. In summary, this patent lacks feasibility in guiding actual design. Summary of the Invention

[0006] To address the limitations of existing technologies in verifying the compatibility between the drive pump and the pump-driven two-phase fluid cooling system, and in predicting the flow characteristics of such systems, this invention aims to propose a method for predicting the flow characteristics of pump-driven two-phase fluid cooling systems. This method calculates the system's operating state point based on the dynamic characteristics of the working fluid during the operation of a spacecraft's two-phase fluid cooling system, verifies the compatibility between the drive pump and the pump-driven two-phase fluid cooling system before system deployment, and predicts the flow characteristics of the pump-driven two-phase fluid cooling system.

[0007] The method includes the following steps: S1. Obtain the average heat consumption of the evaporator. And the cross-sectional area of ​​the pipeline, and define the outlet dryness. Phase transition temperature and latent heat of phase transition of the working fluid at the phase transition temperature. and the density of a single phase of liquid ; S2, according to , and Estimate the flow rate of the working fluid under two-phase conditions. ; S3, according to Estimate the mass flow rate of the liquid working fluid. and according to Calculate the first Total resistance of single-phase flow at a given flow rate , and then The x-axis is... Plot the single-phase flow rate-flow resistance characteristic curve of the system on the vertical axis; S4. Define the dryness at the beginning and end of the liquid phase segment in a two-phase state as follows: and ,according to Calculate the two-phase limiting operating point of a pump-driven two-phase fluid cooling system. ; S5. Select the drive pump, and according to... In the coordinate system of the single-phase flow-resistance characteristic curve of the system, the flow-head characteristic curve of the drive pump at different speeds is plotted to obtain a schematic diagram of the matching between the drive pump and the fluid system. S6. In the matching diagram of the drive pump and fluid system, mark... , and by The first intersection point of the extended line along the positive y-axis and the flow-head characteristic curve of the drive pump is denoted as . , This indicates the two-phase operating point of the pump at standard speed. The flow-head characteristic curve of the drive pump is denoted as ; System single-phase flow rate-flow resistance characteristic curve and The intersection point is denoted as , This indicates the single-phase operating point of the pump at standard speed; S7, according to and Predict the flow characteristics of a pump-driven two-phase fluid cooling system.

[0008] Furthermore, in step S2, the working fluid flow rate in the two-phase state... The formula for calculation is: .

[0009] Furthermore, in step S3, the mass flow rate of the liquid working fluid... minimum value and The values ​​are equal. maximum value Not less than .

[0010] Furthermore, in step S3, the first Total resistance of single-phase flow at a given flow rate The formula for calculation is: ,in, Indicates the first Friction resistance along single-phase flow at a given flow rate , Indicates the friction coefficient. Indicates the length of the flow channel. Indicates the hydraulic diameter of the flow channel. This represents the single-phase flow velocity of a liquid, based on the mass flow rate of the liquid working fluid. , And calculation of pipe cross-sectional area; Indicates the first Local resistance of single-phase flow at a given flow rate , This represents the local drag coefficient.

[0011] Furthermore, in step S4, the two-phase limiting operating point of the pump-driven two-phase fluid cooling system... The formula for calculating the ordinate is: ,in, and Indicates in Traffic down The frictional resistance of single-phase flow at the first flow rate and the first Local resistance of single-phase flow at a given flow rate; Indicates in Two-phase friction resistance under different flow rates, , , , , , This represents the gaseous density of the working fluid. , , and They are all used to represent the corresponding relational expressions for calculation and have no actual meaning; Indicates in Local resistance to two-phase flow at a given flow rate , This represents the local drag coefficient of the two phases.

[0012] Furthermore, in step S5, the selected drive pump meets the following requirement: the rated flow rate minus the head under single-phase conditions should not be less than [a certain value]. .

[0013] Furthermore, in step S6, if the extended line and the flow-head characteristic curve of the drive pump do not intersect, then the drive pump selected in step S5 is not matched with the pump-driven two-phase fluid cooling system, and the process returns to step S5 to reselect the drive pump.

[0014] Furthermore, in step S7, at the standard rotational speed, Towards The transfer process is equivalent to the process in a pump-driven two-phase fluid heat dissipation system where the heat source at the evaporator goes from being closed to being open and then to a stable state.

[0015] The beneficial effects of the method described in this invention are as follows: The present invention discloses a method for predicting the flow characteristics of a pump-driven two-phase fluid cooling system. By testing and calculation, the flow characteristics of the two-phase system and the working characteristics of the driving pump are inferred, the actual working state point of the driving pump is predicted, the matching between the driving pump and the pump-driven two-phase fluid cooling system (fluid system) is verified by plotting, and the flow characteristics of the pump-driven two-phase fluid cooling system are predicted, thereby reducing design blind spots. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the pump-driven two-phase fluid cooling system described in this invention; Figure 2 This is a schematic diagram of the matching between the drive pump and the fluid system described in this invention, where the horizontal axis represents the mass flow rate and the vertical axis represents the pressure drop. Detailed Implementation

[0017] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] This embodiment provides a method for predicting the flow characteristics of a pump-driven two-phase fluid heat dissipation system, the method comprising the following steps: A method for predicting the flow characteristics of a pump-driven two-phase fluid cooling system is disclosed, with the design target being a spacecraft pump-driven two-phase fluid cooling system. This system requires at least a drive pump, an evaporator, a condenser, a receiver, piping, and a working fluid. The drive pump drives the working fluid to undergo a phase change and absorb heat at the evaporator, and a phase change and heat transfer at the condenser. The phase change temperature is controlled by the receiver. The method described in this invention supports extended designs of the system based on the above components, such as arranging a preheater or regenerator before the evaporator. The evaporator is in thermal contact with the spacecraft's heating equipment. There can be one or more evaporators and heating equipment. The average heat dissipation of the heating equipment during operation is defined as... Assuming the working fluid has a dryness fraction when it enters the inlet of the pre-evaporator The dryness level is 0 to avoid localized dry burning; the dryness level at the outlet of the final stage evaporator is set at 0. It was designed to be less than 0.5.

[0019] The working fluid is typically selected from substances such as ammonia, propane, and carbon dioxide, which are gaseous at normal pressure. The latent heat of phase change of the working fluid at the phase change temperature is defined as... .

[0020] The condenser should be located before the inlet of the drive pump. The working fluid flowing through the condenser changes from a gas-liquid two-phase state to a subcooled state. The calculation assumes a dryness fraction of the working fluid at the condenser inlet. Consistent with the dryness of the evaporator outlet.

[0021] This embodiment uses a ground-based prototype of a pump-driven two-phase fluid loop system as an example: The prototype consists of a drive pump, a liquid receiver, an evaporator, a condenser, a preheater, piping, a working fluid (R134a), and sensors.

[0022] like Figure 1 As shown, the prototype includes two identical evaporators (evaporator 1 and evaporator 2), with surface-mounted thin-film heating elements simulating heat sources. Evaporator 1 consumes 150W of heat when the heat source is on, while evaporator 2 consumes 250W. A condenser is located after evaporator 2; after cooling by the condenser, the working fluid enters the drive pump in a subcooled liquid phase. A preheater is located before evaporator 1, its function being to heat the subcooled liquid phase to a saturated state. The prototype controls the phase change temperature to 20°C via a liquid receiver.

[0023] The sensor includes a pressure sensor and a temperature sensor, used to detect the system status.

[0024] To verify the compatibility of the aforementioned drive pump and system (pump-driven two-phase fluid cooling system) and to predict the flow characteristics of the aforementioned drive pump and pump-driven two-phase fluid cooling system, the following operations are performed in this embodiment: S1. Obtain the average heat consumption of the evaporator. And the cross-sectional area of ​​the pipeline, and define the outlet dryness. ( Generally defined as 0.3~0.5, phase transition temperature (20℃), and latent heat of phase transition of the working fluid at 20℃. and the density of a single phase of liquid In this embodiment, , , Approximately Single-phase density of liquid Approximately 1240 kg / m 3 The cross-sectional area of ​​the pipeline is 1.5e-5m. 2 .

[0025] S2: According to , and Estimate the flow rate of the working fluid under two-phase conditions and calculate the mass flow rate of the working fluid under two-phase conditions. : (The calculation result is rounded up).

[0026] S3, according to Estimate the mass flow rate of the liquid working fluid. and according to Calculate the first Total resistance of single-phase flow at a given flow rate and with The x-axis is... Plot the single-phase flow rate-flow resistance characteristic curve of the system on the vertical axis; like Figure 2 As shown, (Mass flow rate) is the horizontal axis. Using pressure drop as the vertical axis, select several points within the range to plot the single-phase flow rate-flow resistance characteristic curve of the system; In step S3, the flow-resistance characteristics of the system in the working fluid liquid phase are tested by combining formula estimation with numerical simulation or formula estimation with physical experimentation. The mass flow rate of the liquid working fluid is measured. satisfy Relationship, minimum value and The values ​​are equal. maximum value Not less than The flow rate interval should ensure a smooth flow rate-flow resistance characteristic curve. The pressure difference between the inlet and outlet of each evaporator and condenser should be statistically analyzed during the above process.

[0027] No. Total resistance of single-phase flow at a given flow rate The formula for calculation is: ,in, Indicates the first Friction resistance along single-phase flow at a given flow rate , Indicates the friction coefficient. Indicates the length of the flow channel. Indicates the hydraulic diameter of the flow channel. This represents the single-phase flow velocity of a liquid, based on the mass flow rate of the liquid working fluid. , And calculation of pipe cross-sectional area; Indicates the first Local resistance of single-phase flow at a given flow rate , This represents the local drag coefficient.

[0028] The friction coefficient With local drag coefficient While there are generally accepted estimation methods in the industry, this patent requires additional verification through numerical simulation or physical testing. The total single-phase flow resistance of the system at a given flow rate after verification is thus... .

[0029] This embodiment disassembles the system into an evaporator, a condenser, and other parts. The calculation of R134a in the liquid phase at 20℃ is performed using formulas and three-dimensional simulation. Up to a mass flow rate of 14 g / s (a total of 8 mass flow rate points, this example only lists 4.5 g / s and...) The flow resistance of each component in the system. The single-phase flow resistance of each component in the system can be calculated by summing the friction force along the unidirectional flow and the local resistance of the single-phase flow.

[0030] Calculations show that at a flow rate of 4.5 g / s, the single-phase flow resistance on both sides of evaporator 1 and evaporator 2 is 2.3 kPa, the single-phase flow resistance of the condenser is 8.1 kPa, and the single-phase flow resistance of the remaining pipes and connections is 7.9 kPa. Therefore, the total single-phase flow resistance at a flow rate of 4.5 g / s is calculated to be 20.6 kPa. ).

[0031] Similarly, At the specified flow rate, the pressure difference across a single evaporator is 12.6 kPa. The pressure difference across the condenser is 46.3 kPa. The single-phase flow resistance of the remaining pipelines and connections is 29 kPa. Calculations show that... The total resistance to single-phase flow at the specified flow rate is 100.5 kPa.

[0032] like Figure 2 As shown, based on the calculated system resistance at 8 mass flow points, the single-phase flow rate-flow resistance characteristic curve of the system can be fitted.

[0033] S4. Define the dryness at the beginning and end of the liquid phase segment in a two-phase state as follows: and ,according to Calculate the two-phase limiting operating point of a pump-driven two-phase fluid cooling system. ; When the heat dissipation of the heating device When the working fluid is applied to the evaporator and reaches equilibrium, the working fluid in the evaporator, condenser, and intermediate flow channel is in a two-phase state, while the condenser outlet to the evaporator inlet flow channel via the drive pump is in a liquid phase state; the maximum dryness at the tail of the evaporator is the evaporator outlet dryness defined in S1. Assuming no backflow in the pipeline, the mass flow rate relationship for each flow path cross-section is as follows: ; The pressure change in a two-phase loop under zero-gravity conditions consists of two parts: the pressure drop due to frictional resistance and the pressure change caused by acceleration. Since the two-phase fluid cooling system of a spacecraft necessarily includes an evaporator and a condenser, the acceleration pressure drop in the evaporator and the acceleration pressure rise in the condenser cancel each other out. Only the frictional resistance pressure drop is calculated, and the system is divided into several segments. Within each segment, the flow channel cross-section is consistent, and the dryness of the working fluid changes monotonically. The segments represent regions of liquid-phase flow, where the calculation results from S3 or their resistance coefficients can be integrated. The segments represent two-phase flow, and their two-phase flow resistance (considered equivalent to the frictional resistance pressure drop) can be calculated by summing the frictional forces along the two-phase flow and the local resistances of the two-phase flow.

[0034] The calculation of frictional resistance pressure drop requires the fluid circuit to be divided into several parts. The segments that can be divided into separate calculations must meet the following conditions: (1) The cross-sectional shape of the flow channel in the segment remains basically unchanged; (2) The dryness in the segment increases, decreases, remains unchanged, or has no dryness (liquid phase state).

[0035] If the working fluid within the section is in the liquid phase, the calculation results or drag coefficient in S3 can be inherited; if the section is in a two-phase state, the dryness at the beginning and end of the section can be used. for and Then the friction resistance along the two phases (in) The frictional resistance of the two phases under the specified flow rate can be calculated using the following formula:

[0036]

[0037]

[0038]

[0039]

[0040] in, This represents the gaseous density of the working fluid (in this embodiment) Dryness ≥ , , , and They are all used to represent the corresponding relational expressions for calculation and have no actual meaning.

[0041] Two-phase local resistance (in) The local resistance of two-phase flow at a given flow rate can be calculated using the following formula:

[0042] in, This represents the local drag coefficient of the two phases, and its value is quite diverse and complex under different local structures. In this embodiment... And leave a certain margin; the dryness of the local structure You can refer to steps S1 and S2 and calculate based on the heat exchange of the flow channel in front of that location.

[0043] The system in Total resistance to two-phase flow at certain flow rates for:

[0044] The two-phase limiting operating point of the pump-driven two-phase fluid cooling system is: ,in, and Indicates in Traffic down The frictional resistance of single-phase flow at the first flow rate and the first Local resistance of single-phase flow at a given flow rate.

[0045] In this embodiment, when the heat consumption Q of the heating device is applied to the evaporator and reaches a balanced state, the dryness of the inlet of evaporator 1 is 0 and the dryness of the outlet is 0.19, the dryness of the inlet of evaporator 2 is 0.19 and the dryness of the outlet is 0.5, and the dryness of the inlet of the condenser is 0.5. It is expected that the working fluid will return to a pure liquid phase state when it flows through 3 / 4 of the condenser channel.

[0046] Calculated At the specified flow rate, the frictional pressure drop across evaporator 1 is 36.5 kPa, the frictional pressure drop across evaporator 2 is 40.8 kPa, the frictional pressure drop across condenser is 21.7 kPa, the flow resistance across the remaining pipes and connections is 10.3 kPa, and the total system resistance is 109.3 kPa. ).

[0047] That is, the two-phase limiting operating point of the system for( ,109.3 kPa).

[0048] S5. Selection of Drive Pump: Considering the actual application scenarios of spacecraft, the drive pump is often a miniature centrifugal pump as the basic form. The initially selected drive pump should have a rated flow rate minus head (pressure drop) of not less than [value missing] under single-phase working fluid conditions in the system. With a certain margin, the drive pump in this embodiment is initially selected as a miniature shielded centrifugal pump. The design process of this drive pump uses water as the working medium, with a rated speed of 16000 rpm and a rated operating point of (8g / s, 120kPa). Since the working fluid (R134a) in the two-phase system is usually gaseous at normal pressure, it is not convenient to test the pump drive characteristics. Other working fluids with similar kinematic viscosity to the system's working fluid (liquid) can be used for testing. In this embodiment, considering experimental safety factors, acetone, whose kinematic viscosity is close to that of liquid R134a, is selected for pump drive characteristic testing. The ratio of their liquid phase densities at 20°C is... The value is 0.65; the mass flow rate, head, and pump power obtained from the test are compared with ( By multiplying these values, we can approximate the flow-head characteristic curves of the drive pump under different speeds with liquid R134a working fluid, and simultaneously obtain the drive pump power at each operating point.

[0049] Test from the rated speed of the drive pump downwards in stages until the drive pump cannot operate stably at low speeds, such as... Figure 2 As shown, this embodiment is based on In the coordinate system of the single-phase flow-resistance characteristic curve of the system, the flow-head characteristic curve of the drive pump at different speeds is plotted to obtain a schematic diagram of the matching between the drive pump and the fluid system. In this embodiment, five different speeds are selected. The intersection of the system's single-phase flow-resistance characteristic curve and the drive pump's flow-head characteristic curve at different speeds is denoted as . , This indicates the single-phase operating point of the pump at standard speed.

[0050] S6, such as Figure 2 As shown in the schematic diagram of the matching between the drive pump and the fluid system, the markings are... , and by Extend a line along the positive y-axis. The first intersection point of this extension line and the (closest) flow-head characteristic curve of the drive pump is denoted as... , This indicates the two-phase operating point of the pump at standard speed, where the pump power is 7.5W. Figure 2 As shown in this embodiment, the flow-head characteristic curve of the drive pump corresponding to rotational speed 2 (14000 rpm) is ( Intersects with the extension line ( The flow-head characteristic curve of the drive pump is denoted as ), that is, the rotational speed 2 is the standard rotational speed when the two-phase system is running.

[0051] The intersection point with the single-phase flow rate-flow resistance characteristic curve of the system is denoted as . , This is the single-phase operating point at standard speed, where the pump power is 8W.

[0052] In step S6, if any of the following conditions exist, you should return to step S5 to reselect the drive pump: (1) Unable to perform plotting operations, such as due to the flow-head curve of the drive pump being in... Below the point (where the extended line and the flow-head characteristic curve of the drive pump do not intersect), etc. (2) point Too close to the curve At the edge of the pressure drop, a small increase in pressure drop can easily cause the flow rate to drop to zero. (3) The power consumption of the drive pump does not meet the overall design requirements of the spacecraft.

[0053] S7, according to and Predict the flow characteristics of a pump-driven two-phase fluid cooling system.

[0054] In step S7, at the standard speed, Towards The transfer process is similar to the process in a pump-driven two-phase fluid cooling system where the heat source at the evaporator goes from closed to open and then to a steady state, i.e., according to... and Predict the flow characteristics of a pump-driven two-phase fluid cooling system.

Claims

1. A method for predicting the flow characteristics of a pump-driven two-phase fluid heat dissipation system, characterized in that, The method includes the following steps: S1. Obtain the average heat consumption of the evaporator. And the cross-sectional area of ​​the pipeline, and define the outlet dryness. Phase transition temperature and latent heat of phase transition of the working fluid at the phase transition temperature. and the density of a single phase of liquid ; S2, according to , and Estimate the flow rate of the working fluid under two-phase conditions. ; S3, according to Estimate the mass flow rate of the liquid working fluid. and according to Calculate the first Total resistance of single-phase flow at a given flow rate , and then The x-axis is... Plot the single-phase flow rate-flow resistance characteristic curve of the system on the vertical axis; S4. Define the dryness at the beginning and end of the liquid phase segment in a two-phase state as follows: and ,according to Calculate the two-phase limiting operating point of a pump-driven two-phase fluid cooling system. ; S5. Select the drive pump, and according to... In the coordinate system of the single-phase flow-resistance characteristic curve of the system, the flow-head characteristic curve of the drive pump at different speeds is plotted to obtain a schematic diagram of the matching between the drive pump and the fluid system. S6. In the matching diagram of the drive pump and fluid system, mark... , and by Extend a line along the positive y-axis. The first intersection point of this extended line and the flow-head characteristic curve of the drive pump is denoted as... , This indicates the two-phase operating point of the pump at standard speed. The flow-head characteristic curve of the drive pump is denoted as ; System single-phase flow rate-flow resistance characteristic curve and The intersection point is denoted as , This indicates the single-phase operating point of the pump at standard speed; S7, according to and Predict the flow characteristics of a pump-driven two-phase fluid cooling system.

2. The method for predicting the flow characteristics of a pump-driven two-phase fluid heat dissipation system according to claim 1, characterized in that, In step S2, the flow rate of the working fluid in the two-phase state The formula for calculation is: .

3. The method for predicting the flow characteristics of a pump-driven two-phase fluid heat dissipation system according to claim 2, characterized in that, In step S3, the mass flow rate of the liquid working fluid is... minimum value and The values ​​are equal. maximum value Not less than .

4. The method for predicting the flow characteristics of a pump-driven two-phase fluid heat dissipation system according to claim 3, characterized in that, In step S3, the first Total resistance of single-phase flow at a given flow rate The formula for calculation is: ,in, Indicates the first Friction resistance along single-phase flow at a given flow rate , Indicates the friction coefficient. Indicates the length of the flow channel. Indicates the hydraulic diameter of the flow channel. This represents the single-phase flow velocity of a liquid, based on the mass flow rate of the liquid working fluid. , And calculation of pipe cross-sectional area; Indicates the first Local resistance of single-phase flow at a given flow rate , This represents the local drag coefficient.

5. The method for predicting the flow characteristics of a pump-driven two-phase fluid heat dissipation system according to claim 4, characterized in that, In step S4, the two-phase limiting operating point of the pump-driven two-phase fluid cooling system. The formula for calculating the ordinate is: ,in, and Indicates in Traffic down The frictional resistance of single-phase flow at the first flow rate and the first Local resistance of single-phase flow at a given flow rate; Indicates in Two-phase friction resistance under different flow rates, , , , , , This represents the gaseous density of the working fluid; , , and They are all used to represent the corresponding relational expressions for calculation and have no actual meaning; Indicates in Local resistance to two-phase flow at a given flow rate , This represents the local drag coefficient of the two phases.

6. The method for predicting the flow characteristics of a pump-driven two-phase fluid heat dissipation system according to claim 5, characterized in that, In step S5, the selected drive pump meets the following requirement: the rated flow rate minus the head under single-phase conditions should not be less than [a certain value]. .

7. The method for predicting the flow characteristics of a pump-driven two-phase fluid heat dissipation system according to claim 6, characterized in that, In step S6, if the extension line and the flow-head characteristic curve of the drive pump do not intersect, then the drive pump selected in step S5 is not matched with the pump-driven two-phase fluid cooling system, and the process returns to step S5 to reselect the drive pump.

8. The method for predicting the flow characteristics of a pump-driven two-phase fluid heat dissipation system according to claim 7, characterized in that, In step S7, at the standard speed, Towards The transfer process is equivalent to the process in a pump-driven two-phase fluid heat dissipation system where the heat source at the evaporator goes from being closed to being open and then to a stable state.

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