General design method for key parameters of pump-driven single-phase fluid loop system

Abstract

The invention discloses a universal design method for key parameters of a pump-driven single-phase fluid loop system, belongs to the technical field of heat dissipation of high-heat-consumption equipment of spacecrafts, and aims to solve the technical problems that the speed of calculating the key parameters of the pump-driven single-phase fluid loop system through simulation iteration is low, and sensitive factors influencing the design of the key parameters are difficult to distinguish. According to the method, a formula calculation mode is adopted to replace system-level simulation iterative calculation, mutual iterative processes during design of all system components are reduced, the initial design duration of pump drive single-phase fluid loop system design is greatly shortened, meanwhile, the method has high accuracy, the formula can directly reflect sensitive factors of key parameter design, and the design efficiency is improved. The complex system design can also be carried out on the basis of the method.

Description

Technical Field

[0001] The invention belongs to the technical field of heat dissipation of high heat consumption equipment of spacecraft. Background Art

[0002] As the heat flux density of single-unit equipment and the total power consumption / weight ratio of spacecraft gradually increase, the selection of heat dissipation surfaces and the transmission of heat during thermal design become increasingly difficult. The pump-driven single-phase fluid loop technology achieves efficient collection, transmission and dissipation of heat through liquid convection heat transfer, which can meet the control requirements of heat transport capacity, the integration requirements of components and the adaptability requirements of the overall design.

[0003] The pump-driven single-phase fluid circuit system in the present invention refers to a closed fluid circulation system for cooling high-power equipment of a spacecraft in a space environment, such as Figure 1 As shown, the ground principle prototype of the pump-driven single-phase fluid loop system is mainly composed of a driving pump, a cold plate, a radiation plate, a circulating working fluid, connecting pipes and joints, a liquid reservoir, a sensor, etc. Its working principle is: the driving pump drives the circulating working fluid to flow through the cold plate installed with a high heat consumption equipment, and the circulating working fluid flows through the radiation plate after the temperature is increased, and radiates heat to the space environment. The cold plate and the radiation plate are both arranged with flow channels for the circulating working fluid to flow.

[0004] Existing patents include spacecraft thermal management systems and ground test system technologies based on pump-driven single-phase fluid loop systems, for example: an autonomous thermal management system for a lunar sample return probe based on a combined heat sink (202110217048.8), a thermal management system and method suitable for cross-domain aircraft (202311583605.3), and a thermal management system and control method for a lunar exploration manned spacecraft (202310491703.8). Both the spacecraft thermal management system and the ground test system are based on a pump-driven single-phase fluid loop.

[0005] The above-mentioned prior arts all describe the layout of the spacecraft thermal management system based on a pump-driven single-phase fluid circuit, and give its composition and temperature control effect. However, the numerical calculation process of the key parameters of the pump-driven single-phase fluid circuit system is not described. In fact, in the initial stage of the design of the pump-driven single-phase fluid circuit system, the key parameters that need to be roughly designed first, such as the selection of the driving pump, the size parameters of the cold plate and the radiation plate, are calculated through simulation iteration. However, due to the mutual coupling relationship between them, system-level simulation iteration calculation is usually required, which will take a lot of time and it is difficult to identify the sensitive factors that affect the design of key parameters. Summary of the invention

[0006] In order to solve the technical problems that the key parameters of a pump-driven single-phase fluid loop system are calculated slowly through simulation iteration and it is difficult to identify sensitive factors that affect the design of key parameters, the present invention proposes a "universal design method for key parameters of a pump-driven single-phase fluid loop system". According to the heat dissipation requirements of high heat consumption equipment in the spacecraft, a numerical design method for key parameters is performed, and the temperature of the high heat consumption equipment under extreme working conditions is calculated.

[0007] General design method for key parameters of pump-driven single-phase fluid circuit system, such as Figure 2 As shown, including:

[0008] Step 1, design and calculation of the cross-sectional dimensions of the cold plate flow channel:

[0009] The high heat consumption equipment installed on the cold plate is defined as H 1 ,H 2 ,…,H n , H 1 Close to the cold plate inlet, H n Near the cold plate outlet, the peak heat consumption of the high heat consumption equipment is Q 1 ,Q2,…,Q n , the total heat consumption is Q s ,

[0010]

[0011] Where: c is the specific heat capacity of the circulating fluid, is the mass flow rate of circulating working fluid, T ho is the cold plate outlet temperature, T hi is the cold plate inlet temperature, T co is the outlet temperature of the radiation panel, T ci is the inlet temperature of the radiation panel, and the total heat consumption Q s When all are discharged through the cold plate, T co Numerically, it is similar to T hi Same, T ci Numerically, it is similar to T ho same;

[0012] According to the installation surface size of the high heat consumption equipment and the cold plate manufacturing process, the length and width of the cold plate flow channel cross section are calculated to be a and b respectively;

[0013] Define the average temperature of the radiation panel as T ca , T ca =(T co +T ci ) / 2, then any high heat consumption equipment H n Temperature T n :

[0014]

[0015] Where: a f is the heat transfer coefficient between the circulating medium and the inner side of the cold plate, h c is the contact thermal conductivity between the high heat consumption equipment and the cold plate, A l is the flow channel side area, A d is the installation surface area of ​​high heat consumption equipment, when T n When the temperature requirements of high heat consumption equipment are met, calculate Step 2. When the temperature requirements of high heat consumption equipment are not met, change the average temperature T of the radiation panel. ca , cross-sectional dimensions of the cold plate flow channel.

[0016] Step 2, design and calculation of radiation plate size and internal flow channel size:

[0017] The heat balance relationship of the radiation panel is:

[0018]

[0019] Where: Q s is the total heat consumption of high heat consumption equipment, is the external heat flux absorbed on both sides of the radiation plate, A R is the single-side area of ​​the radiation plate, ε R is the infrared emissivity of the radiation panel surface, σ is the Stefan-Holtzmann constant, T ca is the average temperature of the radiation plate, and the maximum value of the external heat flux absorbed by both sides of the radiation plate is taken to calculate the single-side area A of the radiation plate. R The minimum value of

[0020] In order to ensure the basic radiation heat dissipation capacity of the radiation plate, the distance d between the radiation plate channels is defined as 2 With the flow channel width d 1 The constraints are as follows:

[0021] Where: c is the thermal conductivity of the radiation panel substrate, λ Al is the thermal conductivity of aluminum alloy.

[0022] Step 3, drive pump selection design calculation:

[0023] Calculation of flow resistance of the pump-driven monomer fluid circuit system after the drive pump is started: including the flow resistance ΔP 1 and local resistance ΔP 2 ,

[0024] ΔP 1 =δ(l / d e )(0.5ρν 2 ),

[0025] ΔP 2=ξ(0.5ρν 2 ),

[0026] Where: δ is the friction factor, l is the flow channel length, d e is the hydraulic diameter of the corresponding flow channel, ρ is the density of the circulating working fluid, ν is the flow velocity of the circulating working fluid, ξ is the local resistance coefficient, and the driving pump is selected according to the calculated flow resistance and the mass flow rate of the circulating working fluid.

[0027] Technical effect:

[0028] According to the heat dissipation requirements of high heat consumption equipment, the present invention can quickly obtain the key parameters of the pump-driven single-phase fluid circuit system through thermodynamic numerical calculation methods in the early stage of design, and predict the temperature of the high heat consumption equipment under extreme working conditions. It explains the numerical design method of key parameters for the basic structure of the pump-driven single-phase fluid circuit system, laying the foundation for the detailed design of the subsequent system. There is no related content similar to the main purpose of the present invention in the prior art.

[0029] By using formula calculation to replace system-level simulation iterative calculations, the mutual iteration process in the design of each system component is reduced, which greatly shortens the initial design time of the pump-driven single-phase fluid circuit system design. At the same time, it has high accuracy. The formula can directly reflect the sensitive factors of key parameter design. Complex system design can also be carried out on the basis of this method. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the ground principle prototype of the existing pump-driven single-phase fluid circuit system.

[0031] Among them, 1-driving pump, 2-cold plate, 3-radiation plate, 4-connecting pipe, 5-connector, 6-liquid reservoir, 7-sensor, 8-high heat consumption equipment H 1 , 9-High heat consumption equipment H 2 , 10-filter, 11-filling valve.

[0032] Figure 2 It is a flowchart of the overall process of the present invention and serves as an abstract drawing. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by ordinary technicians in the field without creative work by adopting the embodiments of the present invention are within the scope of protection of the present invention.

[0034] Heat transfer coefficient between the circulating medium and the inner side of the cold plate in Step 1

[0035] Where: Nu is the Nusselt number, λ is the thermal conductivity of the circulating fluid, d e is the hydraulic diameter of the flow channel, and the Nusselt number Nu is calculated as follows:

[0036]

[0037] Nu=F(a / b)(R e <2300),

[0038] Where: R e is the Reynolds number, P r is the Prandtl number, (a / b) is the aspect ratio of the cross section of the cold plate flow channel, and F(a / b) represents the Reynolds number R e When it is less than 2300, the Nusselt number Nu has a fixed functional relationship with the aspect ratio of the cross section of the cold plate flow channel. In the design process of the pump-driven single-phase fluid circuit system, the flow state of the circulating medium is usually laminar flow (R e <2300), when the design result is a turbulent state, a larger flow resistance will lead to a smaller pump efficiency, and at the same time there will be no significant improvement in the heat exchange capacity. Therefore, the flow channel is designed to make the flow in a laminar state.

[0039] Calculate the temperature T of each high heat consumption equipment n After that, it is determined whether it meets the temperature requirements and whether the necessary design margin is left. If it does not meet the requirements, the average temperature T of the radiation panel is changed. ca , cold plate runner cross-sectional dimensions and other parameters. If they meet the requirements, proceed to Step 2 calculation.

[0040] The calculation formula of the friction factor δ in Step 3 is as follows:

[0041] δ=64 / R e (R e <2300),

[0042] δ=F(R e ,ε / d e )(R e ≥2300),

[0043] Where: ε is the absolute roughness of the pipeline, F(R e ,ε / d e ) indicates that when the Reynolds number R e When the friction factor is greater than or equal to 2300, the Reynolds number R e , relative roughness ε / d e It presents a complex functional relationship, and the driving pump is selected according to the calculated flow resistance and circulating working fluid mass flow rate.

[0044] In order to verify the accuracy and feasibility of the present invention, the design process of a ground principle prototype of a pump-driven single-phase fluid loop system based on this method is described below. There is no branch flow channel in the loop system, and the circulating working fluid is a 50% / 50% water / ethylene glycol mixture.

[0045] Step 1, design and calculation of the cross-sectional dimensions of the cold plate flow channel:

[0046] High heat consumption equipment 1 Close to the inlet of cold plate 2, its peak heat consumption Q 1 The maximum heat flux density of the mounting surface is 1.37W / cm 2 ; High heat consumption equipment H 2 Near the outlet of cold plate 2, its peak heat consumption Q 2 The maximum heat flux density of the mounting surface is 0.7W / cm 2 , total heat consumption Q s The maximum operating temperature of high heat consumption equipment should be less than 55℃.

[0047]

[0048] Where: c is the specific heat capacity of the circulating fluid, is the mass flow rate of circulating working fluid, T ho is the outlet temperature of cold plate 2, T hi is the inlet temperature of cold plate 2, T co is the outlet temperature of radiation plate 3, T ci is the inlet temperature of the radiation panel 3. Total heat consumption Q s When all are discharged through cold plate 2, T co Numerically, it is similar to T hi Same, T ci Numerically, it is similar to T ho Similarly, the temperature difference between the inlet and outlet of the radiation plate 3 is 6℃~10℃, and the minimum value of 6℃ is selected here to obtain the mass flow rate of the circulating working fluid The maximum value is 1.45L / min.

[0049] According to the constraints such as the installation surface size of the high heat consumption equipment and the manufacturing process of the cold plate 2, the cross-sectional size of the cold plate flow channel is defined as 20 mm×2 mm.

[0050] The average temperature of the radiation plate 3 is T ca is 25℃, and its value is (T co +T ci ) / 2, then the inlet temperature of the radiation plate 3 is T ci At 28°C, T co The outlet temperature of the radiation plate 3 is 22°C.

[0051] High heat consumption equipment n Temperature Tn It can be calculated by the following formula:

[0052]

[0053] Where: a f is the heat transfer coefficient between the fluid and the inner side of the cold plate 2; h c A is the contact thermal conductivity between the high heat consumption equipment and the cold plate; l A is the side area of ​​the flow channel; d The installation surface area of ​​high heat consumption equipment.

[0054] The heat transfer coefficient a f Calculated by the following formula:

[0055]

[0056] Where Nu is the Nusselt number; λ is the thermal conductivity of the circulating fluid; d e is the hydraulic diameter of the flow channel. The calculation formula of Nusselt number Nu is as follows:

[0057]

[0058] Nu=F(a / b)(R e <2300),

[0059] In the formula, R e is the Reynolds number; P r is the Prandtl number; (a / b) is the aspect ratio of the cross section of the flow channel of the cold plate 2. It is considered that when the Reynolds number R e When it is less than 2300, the Nusselt number Nu has a fixed relationship with the aspect ratio of the flow channel cross section.

[0060] Calculation can get high heat consumption equipment H 1 Lower channel Reynolds number R e 698, high heat consumption equipment H 2 Lower channel Reynolds number R e is 600, which is less than 2300, that is, the flow of the circulating working fluid is in a laminar state.

[0061] The cross-sectional aspect ratio of the cold plate 2 flow channel is 10. Based on the engineering experience, the Nusselt number Nu is taken as 8.2, so the heat transfer coefficient a f It is 789.3W / m2·K.

[0062] The high heat consumption equipment and the cold plate 2 are installed with heat conduction. According to the engineering experience value, the contact heat conduction h between the high heat consumption equipment and the cold plate is taken. c 1000W / m 2 ·K; High heat consumption equipment H 1 Corresponding cold plate 2 flow channel side area A l1 0.0387m 2, high heat consumption equipment H 2 Corresponding cold plate flow channel side area A l2 0.0792m 2 .

[0063] Under high temperature conditions, high heat consumption equipment H 1 The temperature is 44.5℃, high heat consumption equipment H 2 The temperature is 38.5℃, which meets the design requirements and can be used for the next calculation.

[0064] Step 2, design and calculation of radiation plate size and internal flow channel size:

[0065] The radiation heat dissipation capacity of the radiation plate 3 is the main factor restricting the maximum refrigeration capacity of the pump-driven single-phase fluid circuit, and its heat balance relationship is:

[0066]

[0067] In the formula, A is the external heat flux absorbed on both sides of the radiation plate 3; R is the single-side area of ​​the radiation plate 3; ε R is the infrared emissivity of the radiation plate 3 surface, taking the maximum value of the absorbed external heat flux, the single-side area A of the radiation plate 3 can be calculated R The minimum value of .

[0068] The surface of the radiation plate is sprayed with thermal control white paint or blackened according to the heat flow outside the space, so that the single side area A of the radiation plate R minimize.

[0069] The ground prototype was placed in a vacuum tank for thermal testing, so Replaced by where ε 0 is the infrared emissivity of the vacuum tank wall, which is 0.9; T 0 is the heat sink temperature of the vacuum tank, which is 213K.

[0070] The surface of the radiation plate 3 is blackened and its surface infrared emissivity ε is taken R The design area of ​​the radiation panel should not be less than 0.65m 2 In order to avoid excessive local resistance caused by a sudden change in the flow channel cross-sectional area, the cross-sectional dimensions of the flow channel of the radiation plate 3 are consistent with those of the flow channel of the cold plate.

[0071] In order to ensure the basic radiation heat dissipation capacity of the radiation plate 3, the distance d between the flow channels is defined as 2 With the flow channel width d 1 The constraints are as follows:

[0072]

[0073] In the formula, λ c is the thermal conductivity of the substrate of the radiation plate 3; Al The thermal conductivity of aluminum alloy is 130W / (m·K). The base material of the radiation plate 3 of the ground principle prototype is aluminum alloy, and the width d between the flow channels is 2 It is 80mm.

[0074] Step 3, drive pump selection design calculation:

[0075] In order to ensure that the driving pump 1 has high sealing and high reliability, a shielded centrifugal pump is selected. The key parameter of the pump is the head-flow relationship at different speeds. The head is the flow resistance of the fluid circuit after the driving pump is started, including the resistance along the way ΔP 1 and local resistance ΔP 2 ,

[0076] ΔP 1 =δ(l / d e )(0.5ρν 2 ),

[0077] ΔP 2 =ξ(0.5ρν 2 ),

[0078] Wherein, δ is the friction factor; l is the flow channel length; ρ is the density of the circulating working fluid; ν is the flow velocity of the circulating working fluid; ξ is the local resistance coefficient.

[0079] The calculation formula of the friction factor δ is as follows:

[0080] δ=64 / R e 9R e <2300),

[0081] The flow resistance is greatly affected by the viscosity of the circulating working fluid, and the circulating working fluid usually has a higher viscosity at lower temperatures. Therefore, the working fluid viscosity under the lowest operating temperature conditions of the system is selected for calculation. The circulating working fluid used in the ground principle prototype is a 50% / 50% water / ethylene glycol mixture, which has a freezing point of -35°C. Its minimum operating temperature is defined as -10°C. At this temperature, the system flow resistance is 128kPa.

[0082] After obtaining the system flow resistance and the mass flow rate of the circulating working fluid, the driving pump is selected accordingly. During the selection, the driving pump should have at least 30% of the conveying capacity margin. If the driving pump is difficult to select to the expected requirements, then return to adjust the parameters such as the mass flow rate of the circulating working fluid, the cross-sectional size of the cold plate flow channel, and the size of the radiation plate flow channel.

[0083] The calibration data of the centrifugal pump finally selected are as follows, which has sufficient delivery capacity margin.

[0084]

[0085] It should be noted that the design process described in the present invention is aimed at the underlying parameters of the pump-driven single-phase fluid circuit system, and does not affect the subsequent design process of the system nesting into the superior system or adding temperature control, backup functions, etc. The design method described in the present invention is based on the premise that the circulating working fluid flows in a branchless flow channel. Flow branches can be added based on this calculation result in the future. Such designs will not be elaborated in this patent. The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

Claims

1. A general design method for key parameters of a pump-driven single-phase fluid circuit system, characterized in that: include: Step 1, design and calculation of the cross-sectional dimensions of the cold plate flow channel: The high heat consumption equipment installed on the cold plate is defined as H1, H2, ..., H n , H1 is close to the cold plate inlet, H n Near the cold plate outlet, the peak heat consumption of the high heat consumption equipment is Q1, Q2, ..., Q n , the total heat consumption is Q s , Where: c is the specific heat capacity of the circulating fluid, is the mass flow rate of circulating working fluid, T ho is the cold plate outlet temperature, T hi is the cold plate inlet temperature, T co is the outlet temperature of the radiation panel, T ci is the inlet temperature of the radiation panel, and the total heat consumption Q s When all are discharged through the cold plate, T co Numerically, it is similar to T hi Same, T ci Numerically, it is similar to T ho same; According to the installation surface size of the high heat consumption equipment and the cold plate manufacturing process, the length and width of the cold plate flow channel cross section are calculated to be a and b respectively; Define the average temperature of the radiation panel as T ca , T ca =(T co +T ci ) / 2, then any high heat consumption equipment H n Temperature T n : Where: a f is the heat transfer coefficient between the circulating medium and the inner side of the cold plate, h c is the contact thermal conductivity between the high heat consumption equipment and the cold plate, A l is the flow channel side area, A d is the installation surface area of ​​high heat consumption equipment, when T n When the temperature requirements of high heat consumption equipment are met, calculate Step 2. When the temperature requirements of high heat consumption equipment are not met, change the average temperature T of the radiation panel. ca , cross-sectional dimensions of the cold plate flow channel; Step 2, design and calculation of radiation plate size and internal flow channel size: The heat balance relationship of the radiation panel is: Where: Q s is the total heat consumption of high heat consumption equipment, is the external heat flux absorbed on both sides of the radiation plate, A R is the single-side area of ​​the radiation plate, ε R is the infrared emissivity of the radiation panel surface, σ is the Stefan-Holtzmann constant, T ca is the average temperature of the radiation plate, and the maximum value of the external heat flux absorbed by both sides of the radiation plate is taken to calculate the single-side area A of the radiation plate. R The minimum value of The constraint relationship between the distance d2 between the radiation plate channels and the channel width d1 is defined as follows: Where: c is the thermal conductivity of the radiation panel substrate, λ Al is the thermal conductivity of aluminum alloy; Step 3, drive pump selection design calculation: Calculation of flow resistance of the pump-driven monomer fluid circuit system after the driving pump is started: including the along-the-line resistance ΔP1 and the local resistance ΔP2, ΔP1=δ(l / d e (0.5pn) 2 ), ΔP2=ξ(0.5ρν 2 ), Where: δ is the friction factor, l is the flow channel length, d e is the hydraulic diameter of the corresponding flow channel, ρ is the density of the circulating working fluid, ν is the flow velocity of the circulating working fluid, ξ is the local resistance coefficient, and the driving pump is selected according to the calculated flow resistance and the mass flow rate of the circulating working fluid.

2. The universal design method for key parameters of a pump-driven single-phase fluid circuit system according to claim 1, characterized in that: Heat transfer coefficient between the circulating medium and the inner side of the cold plate in Step 1 Where: Nu is the Nusselt number, λ is the thermal conductivity of the circulating fluid, d e is the hydraulic diameter of the flow channel, and the Nusselt number Nu is calculated as follows: No=F(a / b)(R e <2300), Where: R e is the Reynolds number, P r is the Prandtl number, (a / b) is the aspect ratio of the cross section of the cold plate flow channel, and F(a / b) represents the Reynolds number R e When it is less than 2300, the Nusselt number Nu has a fixed functional relationship with the aspect ratio (a / b) of the cross section of the cold plate flow channel.

3. The universal design method for key parameters of a pump-driven single-phase fluid circuit system according to claim 1, characterized in that: The calculation formula of the friction factor δ in Step 3 is as follows: δ=64 / R e (R e <2300), δ=F(R e ,e / d e )(R e ≥2300), Where: ε is the absolute roughness of the pipeline, R e is the Reynolds number, d e is the hydraulic diameter of the flow channel, F(R e ,ε / d e Indicates that when the Reynolds number R e When the friction factor is greater than or equal to 2300, the Reynolds number R e , relative roughness ε / d e A complex functional relationship.

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