A charging method of a loop heat pipe

Abstract

The application provides a charging method of a loop heat pipe and belongs to the technical field of loop heat pipes. The application realizes complete flow of the charging process through the following steps: S1, system connection; S2, system purging; S3, system sealing; S4, pre-charging vacuum; S5, system weighing; S6, over-charging; S7, system heat discharging; S8, performance testing; S9, system cold discharging; S10, system weighing; and S11, system sealing and welding. Each process link is short in time, the charging efficiency is high, batch production is facilitated, the step of working medium replacement is saved compared with the traditional charging process, and the charging cost is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of loop heat pipe, in particular to a filling method of loop heat pipe. BACKGROUND

[0002] Loop heat pipe has the advantages of large heat transfer, long heat transfer distance, one-way heat transfer, flexible layout, high reliability, long service life, excellent gravity resistance, etc., and is widely used in thermal control of aerospace, data center and other fields.

[0003] Loop heat pipe is composed of evaporator, condenser, liquid reservoir, vapor pipe and liquid pipe, and realizes rapid heat transfer through evaporation and condensation of working medium sealed in the loop heat pipe. The filling of working medium is an important link in the production of loop heat pipe, and the filling amount will directly affect the start and stable operation of the system; the presence of non-condensable gas in the loop heat pipe will also cause the failure of the loop heat pipe.

[0004] Traditional heat pipe usually adopts vacuum filling method for system filling, that is, a certain amount of working medium is filled after the system is vacuumized. However, the evaporator of loop heat pipe has micron-level capillary hole diameter, and the connecting pipe and the condenser pipe are both millimeter-level slender capillary pipes. Therefore, it is difficult to extract ideal vacuum degree in the vacuumizing process, and low vacuum filling will cause a large amount of non-condensable gas remaining in the liquid reservoir, which will seriously affect the uniformity and long-term stability of the system.

[0005] Therefore, compared with traditional heat pipe, the conventional filling process of loop heat pipe requires high-temperature degassing, that is, the system needs to be heated to a high temperature in the vacuumizing process to facilitate the extraction of ideal vacuum degree; at the same time, a working medium replacement needs to be completed before formal filling to ensure that the non-condensable gas in the loop heat pipe can be completely discharged. The conventional filling process flow of loop heat pipe is: high-temperature vacuumizing → filling → working medium replacement → non-condensable gas discharge → high-temperature vacuumizing → filling.

[0006] The conventional filling process flow is time-consuming and low in efficiency, and requires a large process cost, so it is not suitable for batch production. SUMMARY

[0007] In order to solve the technical problems of long filling process flow, low efficiency, high process cost and unsuitability for batch production in the prior art, the present application is implemented as follows:

[0008] A filling method of loop heat pipe, comprising the following steps:

[0009] S1, connecting the loop heat pipe, wherein one end of the condenser is temporarily not connected with the vapor pipe;

[0010] S2, purging the loop heat pipe by filling high-purity inert gas through the filling pipe;

[0011] S3, connecting the other end of the vapor pipe with the inlet of the condenser;

[0012] S4, pre-pumping the loop heat pipe until the vacuum degree in the loop heat pipe reaches P;

[0013] S5, weighing the loop heat pipe and recording the current weight value W1;

[0014] S6, filling the loop heat pipe with excess working medium;

[0015] S7, pasting an electric heating sheet on the outer surface of the evaporator and applying a heat equivalent to the designed heat load, at this time, the non-condensable gas is gathered at the top of the liquid reservoir, and the system is subjected to heat discharge in the heated state;

[0016] S8, adding temperature measuring points to the liquid reservoir 2, the evaporator 1, the inlet of the vapor pipe, the outlet of the vapor pipe, the inlet of the liquid pipe and the outlet of the liquid pipe, detecting the temperatures T1, T2, T3, T4, T5 and T6 of the liquid reservoir, the evaporator, the inlet of the vapor pipe, the outlet of the vapor pipe, the inlet of the liquid pipe and the outlet of the liquid pipe, when the temperature difference ΔT between T3 and T1 is less than 0.5℃, the next step is entered, if ΔT is greater than or equal to 0.5℃, the step S7 is repeated;

[0017] S9, adjusting the power of the electric heating sheet to 0, when the temperatures T1, T2, T3, T4 and T5 are the same as the ambient temperature T, the loop heat pipe is subjected to cold discharge;

[0018] S10, weighing the loop heat pipe after cold discharge and recording the current weight value W2, if the weight W2 of the loop heat pipe after cold discharge is within G1-G2, the step S11 is entered, if not, the step S10 is repeated;

[0019] S11, sealing the filling pipe.

[0020] Preferably, in the step S2, the pressure of the blowing is 1-3 MPa, and the blowing time is 60-300 s.

[0021] Preferably, in the step S4, the vacuum degree P is 80-120 Pa.

[0022] Preferably, in the step S6, the filling amount is 1.01-1.1 times of the theoretical filling amount W.

[0023] Preferably, in the step S11, G1 is W1+W*0.99 grams;

[0024] G2 is W1+W*1.01 grams.

[0025] Preferably, the inert gas in the step S2 is selected from one or more of nitrogen, argon or neon.

[0026] Preferably, the step S7 further comprises a step S7.1 of placing the filling tube at the uppermost of the reservoir.

[0027] The implementation of the present application can solve the technical problems of long process time, low efficiency, high process cost and unsuitability for batch production in the prior art; the present application realizes the technical effects of shorter process time, high filling efficiency, convenience for batch production and guarantee of absolute cleanliness and accurate filling amount inside the loop heat pipe by adopting the secondary degassing process for the loop heat pipe. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are only one embodiment of the present application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0029] Figure 1 is a schematic diagram of a loop heat pipe to be filled;

[0030] Figure 2 is a schematic diagram of the overall workflow of the present embodiment.

[0031] In the above drawings, the respective figure number marks represent:

[0032] 1, evaporator

[0033] 1-1, capillary wick

[0034] 1-2, vapor line interface

[0035] 2, reservoir

[0036] 2-1, filling port

[0037] 2-2, liquid line interface

[0038] 2-3, filling tube

[0039] 3, vapor line

[0040] 4, condenser

[0041] 4-1, condenser line

[0042] 4-2, condenser inlet interface

[0043] 4-3, condenser outlet interface

[0044] 5. Liquid pipeline

[0045] 6. First temperature measuring point

[0046] 7. Second temperature measuring point

[0047] 8. Third temperature measuring point

[0048] 9. Fourth temperature measuring point

[0049] 10. Fifth temperature measuring point

[0050] 11. Sixth temperature measuring point Detailed Implementation

[0051] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0052] Example

[0053] A method for filling a loop heat pipe, such as Figure 1 As shown, the loop heat pipe includes an evaporator 1, a liquid receiver 2, a vapor line 3, a condenser 4, and a liquid line 5. The liquid receiver 2 is cylindrical and includes a filling port 2-1, a liquid line interface 2-2, and a filling pipe 2-3. The filling port 2-1 is located on the cylindrical surface of the liquid receiver 2, and the filling pipe 2-3 is welded to the filling port 2-1. The liquid line interface 2-2 is located on the cylindrical bottom surface of the liquid receiver 2.

[0054] Evaporator 1 is cylindrical and includes a capillary wick 1-1 and a steam pipe interface 1-2. The capillary wick 1-1 is made of porous material with a porosity of 70% and is interference-fitted inside the evaporator 1. The steam pipe interface 1-2 is located on the bottom surface of the cylinder of the evaporator 1.

[0055] The condenser 4 includes a condenser pipe 4-1, a condenser inlet port 4-2, and a condenser outlet port 4-3. The two ends of the condenser pipe 4-1 are connected to the condenser inlet port 4-2 and the condenser outlet port 4-3, respectively.

[0056] In the embodiment, the inner diameter of the evaporator 1 is 14 mm, the length is 225 mm; the outer diameter of the capillary wick 1-1 is 14 mm, the wall thickness is 4 mm, and the length is 210 mm; the inner diameter of the vapor pipe 3 is 2 mm, and the length is 5000 mm; the inner diameter of the liquid pipe 5 is 2 mm, and the length is 6000 mm; the inner diameter of the condenser pipe 4-1 is 2 mm, and the length is 10000 mm; the inner diameter of the liquid reservoir 2 is 32 mm, and the length of the liquid reservoir is 120 mm. The designed heat transfer capacity of the loop heat pipe is 500 W, the working temperature range is between 0-40℃, and the working medium is ammonia. In the embodiment, the theoretical filling amount W is calculated by the designed heat load, the working temperature range, the selected working medium, and the sizes of the evaporator 1, the capillary wick 1-1, the vapor pipe 3, the liquid pipe 5, the condenser pipe 4-1, and the liquid reservoir 2. In the embodiment, the theoretical filling amount W of ammonia is 88.2025 grams. The theoretical filling amount W is calculated by the calculation method disclosed in the patent with the publication number CN114923357A.

[0057] As shown in Figure 2 , a filling method of a loop heat pipe, comprising the following steps:

[0058] S1, system connection: connecting the loop heat pipe, welding the liquid reservoir 2 and the evaporator 1, welding the liquid pipe interface 2-2 of the liquid reservoir 2 with one end of the liquid pipe 5, welding the other end of the liquid pipe 5 with the condenser outlet interface 4-3, welding the vapor pipe interface 1-2 of the evaporator 1 with one end of the vapor pipe 3. In this step, the other end of the vapor pipe 3 is temporarily not connected with the condenser inlet interface 4-2;

[0059] S2, system purging: purging the loop heat pipe by filling pure nitrogen with a purity of 99.99% into the loop heat pipe from the charging pipe 2-3 of the liquid reservoir 2 to preliminarily discharge impurities and mixed gas in the loop heat pipe, wherein the purging pressure is 1.5 MPa, and the duration is 120 s;

[0060] S3, system sealing: sealing the loop heat pipe in the embodiment, and welding and connecting the other end of the vapor pipe 3 with the condenser inlet interface 4-2;

[0061] S4, pre-charging vacuum: pre-vacuumizing the loop heat pipe through the vacuumizing equipment by the charging pipe 2-3, and stopping vacuumizing when the vacuum degree in the loop heat pipe reaches 100 Pa as shown by the vacuum gauge on the vacuumizing equipment;

[0062] S5, system weighing: weighing the loop heat pipe, and recording the current weight value W1 of the loop heat pipe. In the embodiment, the weight W1 of the loop heat pipe is 1636.4447 grams;

[0063] S6, overfilling: the loop heat pipe is overfilled, the amount of the working medium filled is 1.01-1.1 times of the theoretical filling amount W, that is, 1.01*W-1.1*W. In this step, the amount of the working medium filled is 105% of the theoretical filling amount, that is, 92.6126 grams;

[0064] S7, system heat discharge: the loop heat pipe is discharged, an electric heating sheet is attached to the outer surface of the evaporator 1, and 500W of heat is applied, the charging pipe 2-3 is placed at the uppermost part of the reservoir 2, at this time, the non-condensable gas is gathered at the top of the reservoir 2, and the loop heat pipe is discharged in a heated state to discharge the non-condensable gas;

[0065] S8, performance test: the first temperature measuring point 6 is added to the reservoir 2, the second temperature measuring point 7 is added to the evaporator 1, the third temperature measuring point 8 is added to the inlet of the vapor pipe 3, the fourth temperature measuring point 9 is added to the outlet of the vapor pipe 3, the fifth temperature measuring point 10 is added to the inlet of the liquid pipe 5, and the sixth temperature measuring point 11 is added to the outlet of the liquid pipe 5, the temperatures T1, T2, T3, T4, T5 and T6 of the reservoir 2, the evaporator 1, the inlet of the vapor pipe 3, the outlet of the vapor pipe 3, the inlet of the liquid pipe 5 and the outlet of the liquid pipe 5 are detected respectively, so as to detect the uniformity of the loop heat pipe. When the temperature difference ΔT between the detection temperature T3 of the third temperature measuring point 8 and the detection temperature T1 of the first temperature measuring point 6 is less than 0.5℃, the heat discharge is completed;

[0066] S9, system cooling: the loop heat pipe is cooled, the power of the electric heating sheet is adjusted to 0, and when the temperature values T1, T2, T3, T4, T5 and T6 detected by the first temperature measuring point 6, the second temperature measuring point 7, the third temperature measuring point 8, the fourth temperature measuring point 9, the fifth temperature measuring point 10 and the sixth temperature measuring point 11 are all the same as the ambient temperature T, the loop heat pipe is cooled, and the excess working medium is discharged by manual discharge;

[0067] S10, system weighing: the loop heat pipe after cooling is weighed, and the current weight value W2 is recorded, and when the filling amount error of the loop heat pipe is within 0.1%, the cooling is completed. At this time, the weight W2 is within the range of G1-G2, that is, G1=W1+0.99*W, G2=W1+1.01*W. In this embodiment, the value of G1-G2 is 1723.7652-1725.5293 grams;

[0068] S11, system sealing: the charging pipe 2-3 is sealed, and thus the filling of the loop heat pipe is completed.

[0069] The beneficial effects of the present application are:

[0070] 1. The filling process is completely streamlined, each process link is short in time, the filling efficiency is high, and batch production is facilitated;

[0071] 2. The filling process has high fault tolerance and the quality of product batch filling is high;

[0072] 3. Compared with the conventional filling process, the step of working medium replacement is omitted, and the filling cost is low;

[0073] 4. The improvement of the process reduces the vacuum degree requirement of the vacuum extraction link, thereby reducing the requirement for the equipment, and the filling production line is easy to establish;

[0074] 5. Each process link has low requirement for the operator, and it is easy to train and post;

[0075] 6. The purity requirement for the filling working medium is low, and it does not need to be 99.9% or above.

Claims

1. A method for filling a loop heat pipe, characterized in that, The steps include the following: S1. Connect the loop heat pipe, wherein one end of the condenser is not connected to the steam pipe for the time being; S2. High-purity inert gas is introduced through the filling tube to purge the loop heat pipe; S3. Connect one end of the steam pipe to the inlet of the condenser; S4. Pre-evacuate the loop heat pipe until the vacuum level inside the loop heat pipe reaches P; S5. Weigh the loop heat pipe and record the current weight value W1. S6. Fill the loop heat pipe with an excess of working fluid; S7. Attach electric heating elements to the outer surface of the evaporator and apply heat equivalent to the design heat load. Under heating conditions, the system will release heat. S8. Add temperature measuring points at the inlet, outlet, liquid inlet, and outlet of the liquid receiver, evaporator, steam pipeline, and liquid pipeline to detect the temperatures T1, T2, T3, T4, T5, and T6 of the liquid receiver, evaporator, steam pipeline, steam pipeline, liquid pipeline, and liquid pipeline. If the temperature difference ΔT between T3 and T1 is less than 0.5℃, proceed to the next step. If ΔT is greater than or equal to 0.5℃, repeat step S7. S9. Adjust the power of the electric heating element to 0. When T1, T2, T3, T4 and T5 are the same as the ambient temperature T, perform cold radiator cooling on the loop heat pipe. S10. Weigh the loop heat pipe after the radiator and record the current weight value W2. If the weight W2 of the loop heat pipe after the radiator is within G1 to G2, proceed to step S11. If not, repeat step S10. S11. The filling tube is sealed by welding.

2. The method for filling a loop heat pipe according to claim 1, characterized in that, In step S6, the amount of working fluid added is 1.01-1.1 times the theoretical filling amount W.

3. The method for filling a loop heat pipe according to claim 1, characterized in that, In step S2, the purging pressure is 1MPa-3MPa and the purging time is 60s-300s.

4. The method for filling a loop heat pipe according to claim 1, characterized in that, In step S4, the vacuum degree P is 80-120 Pa.

5. The method for filling a loop heat pipe according to claim 1, characterized in that, In step S11, G1 is W1 + W * 0.99 grams; G2 is W1 + W*1.01 grams.

6. The method for filling a loop heat pipe according to claim 1, characterized in that, The inert gas in step S2 is selected from one or more of nitrogen, argon, or neon.

7. The method for filling a loop heat pipe according to claim 1, characterized in that, Step S7 further includes step S7.1 placing the filling tube at the top of the reservoir.

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