This standard specifies the principle, sample preparation, test equipment and instruments, test conditions and procedures, result processing and evaluation of heat pipe life test. This standard is applicable to the life test of various heat pipes whose working temperature is higher than the ambient temperature. GB/T 14813-1993 Heat pipe life test method GB/T14813-1993 standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Life testing method for heat pipe
Life testing method for heat pipe1 Subject content and scope of application
GB/T 14813-93
This standard specifies the principle, sample preparation, test equipment and instruments, test conditions and procedures, result processing and evaluation of heat pipe life test.
This standard is applicable to the life test of various heat pipes whose working temperature is higher than the ambient temperature. 2 Principle and basis
When the working medium of the heat pipe is incompatible with the shell and core materials, non-condensable gas will be generated and accumulated at the end of the condensation section of the heat pipe, making its wall temperature significantly lower than other points on the length of the heat pipe. And with the passage of time, the low temperature zone gradually expands, causing the heat transfer performance of the heat pipe to gradually decline, resulting in failure of the heat pipe. The life of the heat pipe is determined according to the compatibility of the working medium with the shell and core materials. 3 Sample preparation
3.1 Sample structure
The sample is a heat pipe with a diameter of 1 000 rmrm. The total length is divided into three parts: evaporation section A, insulation section B and condensation section C, see Figure a. The outside of the heat pipe is generally a bare tube, but fins can be installed in the condensation section C as needed. The length of the insulation section B is 200mm. According to the needs of heating and cooling, the lengths of the evaporation section A and condensation section C are selected under the condition that the total length remains unchanged. For each heat pipe undergoing life test, the type and brand of the shell and core materials used, the composition and purity of the working fluid, and the relevant heat pipe manufacturing process must be recorded. 3.2 Arrangement and fixation of temperature measuring elements
3.2.1 The temperature measuring element adopts a thermocouple, and its error is not greater than 0.3℃ after calibration. 3.2.2 There are 10 temperature measuring elements on the heat pipe, evenly distributed at three points in the evaporation section of the heat pipe, two points in the insulation section and five points in the condensation section. The specific arrangement is shown in Figure b. 3.2.3 The temperature measuring element should be in close contact with the outer wall of the tube, spot welded or embedded in the tube wall. Before the thermocouple wire is led out, an isothermal section should be maintained. When the electric heating wire is connected to the evaporation section, the temperature measuring point of the evaporation section should be isolated from the electric heating wire. 3.3 Insulation treatment
The evaporation section A and the insulation section B should be tightly wrapped with insulation materials. Approved by the State Administration of Technical Supervision on December 30, 1993, and implemented on August 1, 1994
4 Test load and instrument
GB/T 14813-93
Test sample structure
6 Measurement point distribution
Test sample structure diagram
1—heat pipe: 2—insulation layer: 3-electric heater: 4—thermal electrolysis temperature measurement points and their numbers, A—evaporation section: B—insulation section C—condensation section 4.1 The life test bench is mainly composed of an electric heater, a power supply, a temperature measurement system, and a test bench. If necessary, a temperature control device and a water cooling device can be configured.
4.2 Test instrument
4.2.1 The accuracy level of the instrument for measuring heating electric power shall not be lower than Class 1.5. 4.2.2 The instrument for measuring temperature can be a digital voltmeter or a potentiometer with a resolution of no more than 10V. When using a digital thermometer, the resolution is not greater than 1°C.
5 Test conditions
5.1 Test time
Generally 3 to 5 years, or determined according to specific requirements. 5.2 Test state of heat pipe
During the test, the heat pipe should be in a vertical state. 5.3 Heating method of heat pipe evaporation section
GB/T 14813--93
During the test, the evaporation section of the heat pipe is evenly heated by electric heating. The electric heating wire can be directly wound around the heat pipe, or the evaporation section can be inserted into a special heater (furnace). The heater or heating wire must be electrically insulated from the heat pipe and insulated with an insulation layer on the outside. 5.4 Cooling method of heat pipe condensation section
The condensation section of the heat pipe in the test is cooled by natural convection of air. If necessary, water cooling method can be used. 5.5 Heat pipe test working temperature
The test working temperature T (℃) of the heat pipe is determined by the working temperature required for the life test of the heat pipe. It is expressed as the average value of the temperature of the 6th and 7th measuring points. During the test, the working temperature deviation should be kept within ±5℃, that is: T-±5
5. 6 Heat pipe measurement working temperatureWww.bzxZ.net
+（1）
Take the normal boiling point of the working fluid or the test working temperature as the measurement working temperature. The deviation of the working temperature during measurement is allowed to be within ±5℃. 6 Test sequence
6.1 At the beginning of the test, adjust the heat pipe working temperature to the measurement working temperature. The temperature non-uniformity of the evaporation section and the condensation section should meet the specified values ​​of this type of heat pipe.
6.2 When the working temperature of the heat pipe reaches the measured working temperature, record the electric heating power and the temperature of each measuring point, and fill in the following table Life test record table
Test piece code
Measurement items
Test time, h
Daily test time!
Accumulation time
Working fluid code
Pipe code
Root temperature of each measuring point t;, ℃
Process code
6. 3 Within one month after the start of the life test, it should be measured once a day. Afterwards, it can be measured once every five days. 6.4 In principle, the life test should be carried out continuously. If it is intermittently operated, the operating life should be calculated according to the actual working hours. 7 Processing of test results
7.1 The temperature of the three measuring points of the Yanfa section should meet the uniformity requirements specified in the technical conditions of this type of heat pipe. If it exceeds the specified requirements, the data during this period will be invalid, and this period of time should be deducted from the accumulation time. 7.2 The test results are calculated according to the following formula
Wherein: At.
GB/T 14B13—93
At, = tott
The difference between the temperature of each measuring point in the condensation section and the working temperature of the heat pipe, t: ——The temperature of the 1st to 5th measuring points in the condensation section, ℃; tt,——The temperature of the 6th and 7th measuring points in the adiabatic section, ℃. (2)
7.3 Use a graph to show the change of r. with time. With the accumulation time (h) of the test as the horizontal axis and the temperature difference △t as the vertical axis, draw five curves of the relationship between the temperature difference and time.
8 Evaluation of test results
According to the failure mode described in the test principle, the compatibility of the heat pipe working fluid and the shell material can be evaluated, and the life of the heat pipe can be determined by the compatibility.
8.1 Fully compatible
After a certain period of operation, if, At2t, do not exceed the specified value of the heat pipe, then the material of this heat pipe is fully compatible with the working medium within its test operating temperature range and the operating time. The service life of this heat pipe is greater than the test accumulation time. B.2 Basic compatibility
After a certain period of operation, if only, does not exceed the specified value of the heat pipe, then the material of this heat pipe is basically compatible with the working medium within its test operating temperature range and the operating time. The service life of this heat pipe does not exceed the test accumulation time. 8.3 Incompatible
After a certain period of operation,: exceeds the specified value of the heat pipe, then the material of this heat pipe is incompatible with the working medium. The service life of this heat pipe is very short and is unqualified.
8.4 Variable specified value
The specified value is selected according to the isothermal requirements specified in the technical conditions of this product. Additional notes:
This standard is proposed by the Ministry of Aviation and Aerospace Industry. This standard was drafted by the 501st Design Department of the 5th Institute of the Ministry of Aerospace Industry and the 711st Institute of the 7th Institute of China State Shipbuilding Corporation. The main drafters of this standard are Sun Quanping, Hou Zengqi and Wang Xiusui.
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