Loop heat pipe working fluid charging equivalent debugging method

Abstract

This invention provides an equivalent adjustment method for the working fluid filling quantity of a loop heat pipe. It utilizes the thermal expansion and contraction effect of the liquid working fluid to obtain an equivalent gas-liquid state under on-orbit service conditions. By controlling the temperature of each component of the loop heat pipe, the gas-liquid distribution state of the working fluid within the loop is adjusted. A gas-liquid separation pipeline is set up to achieve gas-liquid separation, and temperature measuring points are arranged on the gas-liquid separation pipeline to monitor the gas-liquid interface position during the adjustment process. Quantitative discharge of the working fluid is achieved through indirect discharge pipelines and valves, enabling precise adjustment of the working fluid quantity. Therefore, this invention allows for precise adjustment of the working fluid filling quantity of large-scale, complex-configuration loop heat pipe products under ground gravity without adjusting their attitude. It has a simple structure and is easy to implement. The indirect discharge pipeline structure enables quantitative discharge of the working fluid with high filling accuracy. Production efficiency is high because the adjustment process is simple and precise, reducing the requirements for filling accuracy and significantly improving the working fluid filling production efficiency.

Description

Technical Field

[0001] This invention belongs to the field of spacecraft thermal control technology, and in particular relates to an equivalent adjustment method for the working fluid filling amount of a loop heat pipe. Background Technology

[0002] Loop heat pipes are a type of high-efficiency heat transfer product developed in recent years. They have outstanding features such as strong heat transfer capacity, long transmission distance, flexible pipe layout, strong anti-gravity working ability, and thermal switching characteristics, enabling large-scale long-distance heat transfer from spacecraft.

[0003] like Figure 1 As shown, a traditional loop heat pipe consists of an evaporator, a receiver, vapor lines, liquid lines, and a condenser. The evaporator is the core component of the loop heat pipe, and it consists of a capillary wick and a shell. Heat is transferred to the capillary wick through the shell, where a gas-liquid phase change occurs on the porous surface of the capillary wick, absorbing heat. The vapor flows along the vapor lines to the condenser, where it releases heat and condenses into a liquid. The liquid flowing out of the condenser continues to be cooled in the condenser and finally flows into the receiver. The liquid working fluid in the receiver maintains the supply to the capillary wick inside the evaporator.

[0004] For large-scale spacecraft systems requiring thermal coupling, the evaporator must be positioned on the heat source side, and the condenser on the heat dissipation side, connected by vapor and liquid pipelines to form a closed loop. The working fluid charge is a critical parameter for ensuring the normal operation of the loop heat pipe. Insufficient charge leads to unstable operation, while excessive charge reduces the condenser's heat exchange area and decreases its heat transfer capacity. For a given loop heat pipe product, precise control of the working fluid charge is necessary to guarantee its heat transfer performance within a specified operating temperature range.

[0005] For large-scale thermal coupling systems based on loop heat pipes, the actual filling volume of the product cannot be obtained by weighing. During the engineering implementation process, the cumulative error of the pipeline length makes it impossible to accurately calculate the theoretical filling volume. Under the ground gravity field, the gas-liquid ratio in pipelines with a diameter greater than 5mm is greatly affected by the attitude and operating state of the loop heat pipe, making it impossible to accurately control the gas-liquid distribution state of the working fluid, and making ground commissioning difficult.

[0006] Spacecraft operating environments are complex, and the designed cryogenic and high-temperature operating points are difficult to simulate in atmospheric conditions. Large-scale thermal vacuum tests are challenging to conduct and significantly increase costs and timelines. A key technical challenge for applying loop heat pipe products to large-scale spacecraft applications is how to quantitatively fill and debug the working fluid under a ground-based gravity field.

[0007] CN201110063596.6 discloses a working fluid filling device and method for a medium-low temperature loop heat pipe. This device and method utilize gravity assistance, control valve opening and closing via a combination of methods, and observe the working fluid mass in a quartz tube to precisely control the required working fluid mass. However, this device and method are not suitable for large-scale spacecraft thermal coupling systems. Firstly, large-scale thermal coupling loop heat pipe products are bulky and have complex spatial configurations, making it difficult to adjust their attitude to the required gravity-assisted attitude. Secondly, when applied to large-scale loop heat pipe products, the gas-liquid ratio along the pipeline is significantly affected by attitude and operating conditions, and the readings observed in the quartz tube cannot accurately reflect the actual working fluid mass. Summary of the Invention

[0008] To address the aforementioned issues, this invention provides an equivalent debugging method for the working fluid filling quantity of a loop heat pipe. This method utilizes the thermal expansion and contraction effect of the working fluid to obtain an equivalent gas-liquid state under on-orbit service conditions. Gas-liquid separation is achieved by setting up a gas-liquid separation pipeline, and temperature measuring points are arranged on the gas-liquid separation pipeline to monitor the gas-liquid interface position during the debugging process.

[0009] A method for equivalent adjustment of the working fluid charge of a loop heat pipe, wherein the loop heat pipe includes a filling pipe, an evaporator, a liquid receiver, a vapor pipeline, a liquid pipeline, and a condenser. A gas-liquid separation pipeline is installed downstream of the condenser, and a limited number of temperature measuring points are arranged on the gas-liquid separation pipeline. An indirect discharge pipeline is connected to the inlet of the filling pipe, and a first valve is installed between the filling pipe and the indirect discharge pipeline. A second valve is installed between the indirect discharge pipeline and an external pipeline. The method is as follows:

[0010] S1: The loop heat pipe is operated under low-temperature equivalent conditions, and working fluid is introduced into the loop heat pipe. The actual amount of working fluid introduced is greater than the theoretical amount. At this time, there is no working fluid in the indirect discharge pipe.

[0011] S2: Open the first valve to allow the working medium to gradually enter the indirect discharge pipeline, then close the first valve; monitor whether the gas-liquid interface in the gas-liquid separation pipeline has moved to the first designated position through the temperature measuring point. If not, open the second valve to discharge the working medium in the indirect discharge pipeline to the external pipeline and then repeat step S2. If yes, proceed to step S3.

[0012] S3: The loop heat pipe is set to operate under high-temperature equivalent conditions. The gas-liquid interface in the gas-liquid separation pipeline is monitored by temperature measuring points to see if it has retreated to the second specified position. If it has, the error between the filling amount of the working fluid in the loop heat pipe and the theoretical filling amount meets the set requirements.

[0013] Furthermore, in step S3, if the gas-liquid interface in the gas-liquid separation pipeline does not return to the second designated position, the working fluid is refilled and steps S1 to S2 are repeated until the error between the amount of working fluid in the loop heat pipe and the theoretical amount of working fluid meets the set requirements.

[0014] Furthermore, a gas-liquid separation pipeline is installed downstream of the condenser, so that the working fluid can complete gas-liquid separation after passing through the gas-liquid separation pipeline, and temperature measuring points are arranged on the gas-liquid separation pipeline to monitor the gas-liquid interface position during the debugging process; at the same time, the gas-liquid separation pipeline is a pipe or sleeve structure with an inner diameter of less than 3mm.

[0015] Furthermore, the method for obtaining the theoretical filling amount of the working fluid is as follows:

[0016] The expected temperature state of each component when the loop heat pipe is used in orbit is obtained by simulation, and the working fluid density can be obtained accordingly. Given the volume of each component, the theoretical filling amount of the working fluid can be calculated.

[0017] Furthermore, the method for adjusting the gas-liquid distribution state of the working fluid inside the loop heat pipe under the ground gravity field is as follows:

[0018] A thermoelectric cooler is used to cool the liquid receiver, and a simulated heater is used to heat the evaporator. The working fluid inside the loop heat pipe circulates according to the design. After gas-liquid separation is completed using a gas-liquid separation pipeline, the internal working fluid distribution is as follows: the liquid receiver is filled with liquid working fluid, the liquid pipeline is filled with liquid working fluid, the condenser is partially filled with liquid working fluid and partially filled with gaseous working fluid, the vapor pipeline is filled with gaseous working fluid, and the capillary wick inside the evaporator is filled with liquid working fluid.

[0019] Furthermore, the method to make the loop heat pipe operate under low-temperature equivalent conditions is as follows:

[0020] The liquid receiver is cooled to 21±1.5℃ using a thermoelectric cooler, the evaporator is heated to 31±1.5℃ using a simulated heater, and the condenser is cooled by convection or radiation, so that the temperature of the vapor line is maintained at 31±1.5℃ and the temperature of the liquid line is maintained at 23±1.5℃.

[0021] Meanwhile, the working fluid shrinks in volume under low-temperature equivalent conditions. After the working fluid preferentially fills the evaporator, liquid receiver and liquid pipeline, the remaining working fluid can fill part of the gas-liquid separation pipeline.

[0022] Furthermore, the method to make the loop heat pipe operate under high-temperature equivalent conditions is as follows:

[0023] The liquid receiver is cooled to 27±1.5℃ using a thermoelectric cooler, the evaporator is heated to 37±1.5℃ using a simulated heater, and the condenser is cooled by convection or radiation, so that the temperature of the vapor line is maintained at 37±1.5℃ and the temperature of the liquid line is maintained at 33±1.5℃.

[0024] Meanwhile, the working fluid expands in volume under high-temperature equivalent conditions. After the working fluid preferentially fills the evaporator, liquid receiver and liquid pipeline, the remaining working fluid can completely fill the gas-liquid separation pipeline.

[0025] Furthermore, the total volume of the indirect discharge pipeline is smaller than that of the gas-liquid separation pipeline, although both have the same cross-sectional diameter, which is on the order of millimeters.

[0026] Beneficial effects:

[0027] 1. This invention provides an equivalent debugging method for the working fluid filling quantity of a loop heat pipe. It utilizes the thermal expansion and contraction effect of the liquid working fluid to obtain an equivalent gas-liquid state under on-orbit service conditions. By controlling the temperature of each component of the loop heat pipe, the gas-liquid distribution state of the working fluid inside the loop is adjusted. A gas-liquid separation pipeline is set up to achieve gas-liquid separation, and temperature measuring points are arranged on the gas-liquid separation pipeline to monitor the gas-liquid interface position during the debugging process. Quantitative discharge of the working fluid is achieved through pipelines and valves for indirect discharge, enabling precise debugging of the working fluid quantity. Therefore, this invention has good adaptability; under the ground gravity field, precise debugging of the working fluid filling quantity of large-scale, complex-configuration loop heat pipe products can be performed without adjusting the attitude. It has a simple structure and is easy to implement. The indirect discharge pipeline structure enables quantitative discharge of the working fluid with high filling accuracy. It also has high production efficiency; due to the simple and high-precision operation of the debugging process, the requirement for filling accuracy is reduced, and the production efficiency of working fluid filling is greatly improved.

[0028] 2. This invention provides an equivalent debugging method for the working fluid filling amount of a loop heat pipe. It uses a thermoelectric cooler to cool the liquid receiver, a simulated heater to heat the evaporator, and convection or radiation to cool the condenser. In other words, this invention can adjust the initial gas-liquid distribution state of the internal working fluid by cooling or heating each component of the loop heat pipe. It has strong design flexibility for equivalent operating conditions and can be debugged in an atmospheric environment, avoiding the need to simulate on-orbit conditions in a vacuum tank, thus saving development costs.

[0029] 3. This invention provides an equivalent adjustment method for the working fluid filling amount of a loop heat pipe. The gas-liquid separation pipeline can achieve gas-liquid separation without adjusting the product posture by using a preferred pipeline or sleeve structure with a small cross-sectional diameter in the millimeter range. The movement of the gas-liquid interface can be monitored by arranging a limited number of temperature measuring points. This method is easy to implement for large-scale loop heat pipe products with complex configurations.

[0030] 4. This invention provides an equivalent adjustment method for the working fluid filling amount of a loop heat pipe. The gas-liquid separation pipeline is a tube body or sleeve structure with an inner diameter of less than 3mm. Both are commonly used materials for loop heat pipes and have the advantages of easy availability of raw materials and good manufacturing process. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the existing loop heat pipe principle;

[0032] Figure 2 This is a schematic diagram of the structure of the loop heat pipe of the present invention;

[0033] Figure 3 This document records the temperature changes at the capillary pump and condenser measuring points during the commissioning process.

[0034] 1-Liquid receiver, 2-Evaporator, 3-Steam line, 4-Condenser, 5-Gas-liquid separation line, 6-Liquid line, 7-Indirect discharge line, 8-First valve, 9-Second valve. Detailed Implementation

[0035] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.

[0036] Example 1

[0037] A method for equivalent adjustment of working fluid charge in a loop heat pipe, such as... Figure 2 As shown, the loop heat pipe includes a filling pipe, an evaporator, a liquid receiver, a vapor pipe, a liquid pipe, and a condenser. A gas-liquid separation pipe is provided downstream of the condenser, and more than five temperature measuring points are arranged on the gas-liquid separation pipe. An indirect discharge pipe is connected to the inlet of the filling pipe, and a first valve is provided between the filling pipe and the indirect discharge pipe. A second valve is provided between the indirect discharge pipe and the external pipe.

[0038] It should be noted that the gas-liquid separation pipeline preferably has a small cross-sectional diameter, such as a millimeter-scale pipeline, which facilitates monitoring of the gas-liquid interface position when the working fluid volume changes. The gas-liquid separation pipeline is characterized by a volume slightly smaller than the allowable filling tolerance; additionally, the gas-liquid separation pipeline preferably has fins to facilitate monitoring of the gas-liquid interface position via an infrared camera. The total volume of the indirect discharge pipeline is smaller than the total volume of the gas-liquid separation pipeline, preferably 1 / 4 to 1 / 3 of the total volume of the gas-liquid separation pipeline; furthermore, the present invention can use thermocouples or infrared cameras to monitor the gas-liquid distribution state in the gas-liquid separation pipeline.

[0039] The equivalent debugging method is as follows:

[0040] S1: The loop heat pipe is operated under low-temperature equivalent conditions, and working fluid is introduced into the loop heat pipe. The actual amount of working fluid introduced is greater than the theoretical amount. At this time, there is no working fluid in the indirect discharge pipe.

[0041] It should be noted that the initial gas-liquid distribution inside the loop heat pipe is as follows: the liquid reservoir contains liquid working fluid, the evaporator capillary wick contains liquid working fluid, the vapor pipe contains gas working fluid, the condenser contains a certain proportion of gas working fluid and a certain proportion of liquid working fluid, and the part near the vapor pipe contains gas working fluid, the part near the gas-liquid separation pipe contains liquid working fluid, the gas-liquid separation section contains liquid working fluid, and the liquid pipe contains liquid working fluid.

[0042] The theoretical charge of the working fluid is obtained as follows: Based on the system simulation results, the expected temperature state of different components when the loop heat pipe is used in orbit can be obtained, and the density of the working fluid can be obtained accordingly. Given the volume of the components, the theoretical charge weight of the working fluid can be calculated. The components include the filling pipe, evaporator, liquid receiver, vapor pipeline, liquid pipeline, and condenser, etc.

[0043] Furthermore, during ground commissioning, the temperature of different components can be controlled by heating or cooling. The design incorporates a low-temperature equivalent operating condition. Since the working fluid charge exceeds the theoretical charge, the gas-liquid separation pipeline is initially filled with subcooled liquid. Specifically, this condition is characterized by the working fluid volume shrinking. After the liquid working fluid preferentially fills the evaporator, reservoir, and liquid pipeline, the remaining working fluid volume can fill part of the gas-liquid separation pipeline.

[0044] S2: Open the first valve to allow the working medium to gradually enter the indirect discharge pipeline, then close the first valve; monitor whether the gas-liquid interface in the gas-liquid separation pipeline has moved to the first designated position through the temperature measuring point. If the gas volume occupies more than 1 / 4 of the total volume of the gas-liquid separation pipeline, if not, open the second valve to discharge the working medium in the indirect discharge pipeline to the external pipeline and then repeat step S2. If yes, proceed to step S3.

[0045] It should be noted that, as Figure 2 As shown, the condenser 4 and steam line 3 are on the right side of the gas-liquid separation pipeline 5, and the liquid line 6 is on the left side. The temperature in the steam line 3 is higher than the temperature in the liquid line. The position of the gas-liquid interface can be determined by the temperature measuring points arranged along the pipeline direction on the gas-liquid separation pipeline. Specifically, if the temperature monitored by a certain temperature measuring point is the same as or close to the temperature on the steam line, and the temperature of the nearest temperature measuring point to the left of that temperature measuring point is the same as or close to the temperature on the liquid line 6, then the gas-liquid interface is located between these two temperature measuring points. It can also be seen that the denser the temperature measuring points are arranged on the gas-liquid separation pipeline, the higher the accuracy of the gas-liquid interface position measurement.

[0046] S3: Set the loop heat pipe to operate under high-temperature equivalent conditions. Monitor the gas-liquid interface in the gas-liquid separation pipeline through temperature measuring points to see if it has retreated to the second specified position. If yes, the error between the filling amount of the working fluid in the loop heat pipe and the theoretical filling amount meets the set requirements. If no, it means that the working fluid was released in the previous steps, and the working fluid needs to be refilled and steps S1 to S2 need to be repeated until the error between the filling amount of the working fluid in the loop heat pipe and the theoretical filling amount meets the set requirements.

[0047] The characteristics of the high-temperature equivalent operating condition are: under this condition, the working fluid volume expands, and after the liquid working fluid preferentially fills the evaporator, the liquid storage tank and the liquid pipeline, the remaining working fluid volume can completely fill the gas-liquid separation pipeline.

[0048] It should be noted that, due to the increase in temperature, the liquid working fluid expands in volume. If the working fluid in the loop heat pipe is not released in excess, the gas-liquid interface in the gas-liquid separation pipe should return to the second specified position after the working fluid expands in volume. That is, the gas-liquid separation pipe that has been opened will gradually close. The working fluid in the loop heat pipe is then verified to be properly adjusted through the high-temperature equivalent working condition.

[0049] Therefore, this invention regulates the gas-liquid distribution of the working fluid inside the loop by controlling the temperature of each component of the loop heat pipe; utilizes the thermal expansion and contraction effect of the liquid working fluid to obtain the equivalent gas-liquid state under on-orbit service conditions; sets up a gas-liquid separation pipeline to monitor the gas-liquid interface, and monitors the position of the gas-liquid interface during the debugging process by infrared or thermocouples; and achieves quantitative discharge of the working fluid through pipelines and valves for indirect discharge, thereby realizing precise debugging of the working fluid.

[0050] Example 2

[0051] The following section uses an ammonia working fluid loop heat pipe as an example to further illustrate the equivalent adjustment method for working fluid filling quantity of the present invention.

[0052] (1) Calculation of theoretical filling capacity

[0053] Based on the system simulation results, the temperature levels and working fluid gas-liquid states of different components during the on-orbit operation of the loop heat pipe are obtained, and the density of the working fluid is queried accordingly. Combined with the known component volumes, the theoretical working fluid filling capacity m is calculated.

[0054] (2) Design equivalent operating conditions

[0055] The design assumes a low-temperature equivalent operating condition, ensuring that the working fluid charge (m) can fill the evaporator, liquid receiver, and liquid pipeline. The gas-liquid separation pipeline has half its length filled with liquid working fluid and half with gaseous working fluid. Design results: Evaporator temperature 31℃, liquid receiver temperature 21℃, vapor pipeline temperature 31℃, liquid pipeline temperature 23℃, and the gas-liquid separation pipeline has half its length filled with liquid working fluid and half with gaseous working fluid.

[0056] The design assumes a high-temperature equivalent operating condition, ensuring that after the working fluid (m) fills the evaporator, liquid receiver, and liquid pipeline, the remaining working fluid volume can completely fill the gas-liquid separation pipeline. Design results: Evaporator temperature 37℃, liquid receiver temperature 27℃, vapor pipeline temperature 37℃, liquid pipeline temperature 33℃, and the gas-liquid separation pipeline is completely filled with liquid working fluid.

[0057] The gas-liquid separation pipeline is selected with a diameter of 3mm, a wall thickness of 0.8mm, and a length of 0.5m. At 20℃, the working fluid inside the gas-liquid separation pipeline is 0.3g, and the filling amount adjustment accuracy is better than 0.3g.

[0058] (3) Filling working fluid

[0059] Ammonia working fluid is charged into the loop heat pipe circuit by indirect charging method, ensuring that the charging amount is 2-4g more than the theoretical charging amount.

[0060] (4) Arrange temperature measuring points

[0061] Temperature measuring points are arranged on each component of the loop heat pipe, with 5 temperature measuring points arranged sequentially along the subcooled loop pipe to monitor the operating status of the loop heat pipe.

[0062] (5) Start the loop heat pipe

[0063] The liquid receiver is cooled using a thermoelectric cooler (TEC), the evaporator is heated using a simulated heater, and the condenser dissipates heat through natural convection.

[0064] Turn on the TEC, input voltage 14V, set current limit 1.4A, and monitor the temperature level at each measuring point;

[0065] When the temperature difference between the evaporator saddle and the liquid receiver is greater than 7°C, turn on the auxiliary start heater, input voltage 50V, set current limit 0.3A, and monitor the temperature level at each measuring point;

[0066] Adjust the input power of the simulated heating element to start the loop heat pipe and maintain the evaporator temperature at 31±1.5℃, the liquid receiver temperature at 21±1.5℃, and the steam pipe temperature at 31±1.5℃.

[0067] (6) Adjust the filling amount

[0068] Excess ammonia is discharged through a commissioning fixture connected to the filling pipe until half of the gas-liquid separation pipeline is filled with vapor and half with liquid. The indirect discharge pipeline is selected with a diameter of 3mm, a wall thickness of 0.8mm, and a length of 0.1m, and the operation is as follows:

[0069] First, open valve 1, which is connected to the filling pipe, so that the liquid working fluid enters the indirect discharge pipeline, and then close valve 1.

[0070] Observe the opening position of the gas-liquid interface. If the gas-liquid interface is not opened to the design position, then open valve 2, which is connected to the outside, to indirectly discharge the working fluid in the discharge pipeline to the outside.

[0071] Repeat the above two operations until the gas-liquid interface opens to the designed position.

[0072] (7) Verify the closure of the gas-liquid separation pipeline under high-temperature conditions

[0073] Adjust the loading power to raise the operating temperature of the loop heat pipe, maintain the evaporator temperature at 37±1.5℃, the liquid receiver temperature at 27±1.5℃, and the steam pipe temperature at 37±1.5℃; monitor the gas-liquid interface retreat of the gas-liquid separation pipe, and after confirming that the gas-liquid separation pipe is closed in the design state, the filling volume adjustment is completed.

[0074] The changes in the capillary pump measuring points and condenser measuring points during the commissioning process are as follows: Figure 3 As shown, turn on the TEC to assist in starting the operating loop heat pipes. Turn on the temperature-controlled heating to bring the evaporator temperature to the stable temperature required for low-temperature operation. Figure 3 It can be concluded that the condenser fins are partially open. After the loop heat pipe reaches the low-temperature operating condition, a certain mass is discharged through the indirect exhaust pipe, and the measuring points on the gas-liquid separation pipe open sequentially to the required positions. After the low-temperature operating condition stabilizes, the high-temperature operating condition is verified. When all components of the product reach the designed high-temperature operating condition, the measuring points on the gas-liquid separation pipe begin to close, and the temperature drops.

[0075] Therefore, this invention utilizes the method of designing low-temperature equivalent operating conditions based on the thermal expansion and contraction of the liquid working fluid to equivalently design the gas-liquid distribution state of the working fluid in orbit into a gas-liquid distribution state easily interpretable from the ground, reducing the resources required for environmental simulation. Simultaneously, the gas-liquid separation pipeline design for determining the gas-liquid interface position in this invention requires a pipeline volume smaller than the filling accuracy requirements and a smaller pipeline diameter to facilitate observation of the gas-liquid interface movement. Finally, through the design of a reasonable indirect discharge pipeline, excess working fluid can be quantitatively discharged. The diameter of the discharge pipeline is close to that of the gas-liquid separation pipeline, while its length is shorter.

[0076] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A method for equivalent adjustment of the working fluid charge of a loop heat pipe, wherein the loop heat pipe includes a charging pipe, an evaporator, a liquid receiver, a vapor line, a liquid line, and a condenser, characterized in that, A gas-liquid separation pipeline is installed downstream of the condenser, and a limited number of temperature measuring points are arranged on the gas-liquid separation pipeline. An indirect discharge pipeline is connected to the inlet of the filling pipe, and a first valve is installed between the filling pipe and the indirect discharge pipeline. A second valve is installed between the indirect discharge pipeline and the external pipeline. The gas-liquid distribution in the gas-liquid separation pipeline is monitored using a thermocouple or an infrared camera. The method is as follows: S1: The loop heat pipe is operated under low-temperature equivalent conditions, and working fluid is introduced into the loop heat pipe. The actual amount of working fluid introduced is greater than the theoretical amount. At this time, there is no working fluid in the indirect discharge pipe. S2: Open the first valve to allow the working medium to gradually enter the indirect discharge pipeline, then close the first valve; monitor whether the gas-liquid interface in the gas-liquid separation pipeline has moved to the first designated position through the temperature measuring point. If not, open the second valve to discharge the working medium in the indirect discharge pipeline to the external pipeline and then repeat step S2. If yes, proceed to step S3. S3: The loop heat pipe is set to operate under high-temperature equivalent conditions. The gas-liquid interface in the gas-liquid separation pipeline is monitored by temperature measuring points to see if it has retreated to the second specified position. If it has, the error between the filling amount of the working fluid in the loop heat pipe and the theoretical filling amount meets the set requirements.

2. The equivalent adjustment method for working fluid charge of a loop heat pipe as described in claim 1, characterized in that, In step S3, if the gas-liquid interface in the gas-liquid separation pipeline does not return to the second designated position, the working medium is refilled and steps S1 to S2 are repeated until the error between the amount of working medium in the loop heat pipe and the theoretical amount meets the set requirements.

3. The equivalent adjustment method for working fluid charge of a loop heat pipe as described in claim 1, characterized in that, A gas-liquid separation pipeline is installed downstream of the condenser, so that the working fluid can be separated into gas and liquid after passing through the gas-liquid separation pipeline. Temperature measuring points are arranged on the gas-liquid separation pipeline to monitor the position of the gas-liquid interface during the debugging process. At the same time, the gas-liquid separation pipeline is a pipe or sleeve structure with an inner diameter of less than 3mm.

4. The equivalent adjustment method for working fluid charge of a loop heat pipe as described in claim 1, characterized in that, The method for obtaining the theoretical filling amount of the working fluid is as follows: The expected temperature state of each component when the loop heat pipe is used in orbit is obtained by simulation, and the working fluid density can be obtained accordingly. Given the volume of each component, the theoretical filling amount of the working fluid can be calculated.

5. The equivalent adjustment method for working fluid charge of a loop heat pipe as described in claim 1, characterized in that, The method for adjusting the gas-liquid distribution of the working fluid inside the loop heat pipe under the ground's gravity field is as follows: A thermoelectric cooler is used to cool the liquid receiver, and a simulated heater is used to heat the evaporator. The working fluid inside the loop heat pipe circulates according to the design. After gas-liquid separation is completed using a gas-liquid separation pipeline, the internal working fluid distribution is as follows: the liquid receiver is filled with liquid working fluid, the liquid pipeline is filled with liquid working fluid, the condenser is partially filled with liquid working fluid and partially filled with gaseous working fluid, the vapor pipeline is filled with gaseous working fluid, and the capillary wick inside the evaporator is filled with liquid working fluid.

6. The equivalent adjustment method for working fluid charge of a loop heat pipe as described in claim 1, characterized in that, The method to make the loop heat pipe operate under low-temperature equivalent conditions is as follows: The liquid receiver is cooled to 21±1.5℃ using a thermoelectric cooler, the evaporator is heated to 31±1.5℃ using a simulated heater, and the condenser is cooled by convection or radiation, so that the temperature of the vapor line is maintained at 31±1.5℃ and the temperature of the liquid line is maintained at 23±1.5℃. Meanwhile, the working fluid shrinks in volume under low-temperature equivalent conditions. After the working fluid preferentially fills the evaporator, liquid receiver and liquid pipeline, the remaining working fluid can fill part of the gas-liquid separation pipeline.

7. The equivalent adjustment method for working fluid charge of a loop heat pipe as described in claim 1, characterized in that, The method to make the loop heat pipe operate under high-temperature equivalent conditions is as follows: The liquid receiver is cooled to 27±1.5℃ using a thermoelectric cooler, the evaporator is heated to 37±1.5℃ using a simulated heater, and the condenser is cooled by convection or radiation, so that the temperature of the vapor line is maintained at 37±1.5℃ and the temperature of the liquid line is maintained at 33±1.5℃. Meanwhile, the working fluid expands in volume under high-temperature equivalent conditions. After the working fluid preferentially fills the evaporator, liquid receiver and liquid pipeline, the remaining working fluid can completely fill the gas-liquid separation pipeline.

8. The equivalent adjustment method for working fluid charge of a loop heat pipe as described in any one of claims 1 to 7, characterized in that, The total volume of the indirect discharge pipeline is smaller than that of the gas-liquid separation pipeline, but both have the same cross-sectional diameter, which is on the order of millimeters.

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