Alkali metal heat pipe phase distribution measurement device and method

Abstract

The present invention discloses an alkali metal heat pipe phase distribution measurement device and method, the measurement device comprises a ray source, a ray collimator and a scintillator detector; the ray source and the scintillator detector are respectively placed at two ends of the alkali metal heat pipe in a radial direction, the ray source and the receiving scintillator detector are respectively used to emit gamma rays; the ray collimator is arranged at the front end of the ray source, and is used to adjust the beam intensity of the gamma rays. The measurement device of the present invention can realize the gas-liquid two-phase distribution measurement of the alkali metal heat pipe.

Description

Technical Field

[0001] The invention relates to the technical field of heat transfer, and in particular to a device and method for measuring phase distribution of an alkali metal heat pipe. Background Art

[0002] As an efficient passive heat transfer device, heat pipes can achieve efficient heat transfer over long distances, and have the advantages of good isothermal properties, simple design, easy processing and manufacturing, simple structure, convenient maintenance, and no need for pump work. Heat pipes can be divided according to the working temperature range, including low-temperature heat pipes (-273 ~ 0℃), normal temperature heat pipes (0 ~ 250℃), medium temperature heat pipes (250 ~ 450℃), high temperature heat pipes (450 ~ 1000℃), etc. Among them, high-temperature heat pipes usually use alkali metals as working fluids, so they are also called alkali metal high-temperature heat pipes. This type of heat pipe is mainly used for special purposes such as aerospace, nuclear engineering, etc.

[0003] The detection of the internal operating status of alkali metal heat pipes is of great significance for the operation monitoring and safe production of alkali metal heat pipes. Since the working fluid of alkali metal heat pipes is opaque, it is impossible to use optical probes or windows to build a visual experimental device to obtain the phase distribution of the gas-liquid two-phase fluid inside the heat pipe. Summary of the invention

[0004] The object of the present invention is to provide an alkali metal heat pipe phase distribution measurement device and method, so as to realize the gas-liquid two-phase distribution measurement of the alkali metal heat pipe.

[0005] The present invention is achieved through the following technical solutions:

[0006] An alkali metal heat pipe phase distribution measuring device comprises a radiation source, a radiation collimator and a scintillator detector;

[0007] The ray source and the scintillator detector are respectively placed at two ends of the alkali metal heat pipe in a radial direction, and the ray source and the receiving scintillator detector are respectively used to emit gamma rays;

[0008] The ray collimator is arranged at the front end of the ray source and is used to adjust the beam intensity of the gamma ray.

[0009] The measuring device of the present invention can be loaded at any position that needs to be detected in the heat pipe insulation section, insulation section, and condensation section, and can also be designed with multiple gamma rays to form an array to perform real-time measurements at the same position but different angles of the heat pipe, or at the same angle but different heat pipe positions (the installation position of the ray measuring device can be moved along the length direction of the heat pipe to obtain the phase distribution of the heat pipe at different positions).

[0010] The present invention can set a linear guide rail parallel to the central axis of the alkali metal heat pipe on the outside of the alkali metal heat pipe to realize the movement of the measuring device in the length direction of the alkali metal heat pipe; and can set an annular guide rail on the outside of the alkali metal heat pipe to realize the rotation of the measuring device on the same cross section, and the annular guide rail and the alkali metal heat pipe have the same central axis.

[0011] The measuring device of the present invention can realize the measurement of the gas-liquid two-phase distribution of the alkali metal heat pipe, which solves the problem that it is impossible to use optical probes or windows to build a visual experimental device to obtain the phase distribution of the gas-liquid two-phase fluid inside the heat pipe.

[0012] Furthermore, the beam formed after the gamma rays are collimated by the ray collimator includes narrow-beam gamma rays and wide-beam gamma rays.

[0013] The beam is a star-chasing beam in the alkali metal heat pipe.

[0014] The narrow-beam gamma rays and wide-beam gamma rays of the present invention are two relative concepts. Rays with a collimation angle of less than 10 degrees are narrow-beam gamma rays, and rays with a collimation angle of more than 30 degrees are wide-beam gamma rays.

[0015] Furthermore, the wide beam gamma ray is used to measure the phase distribution information; and the narrow beam gamma ray is used to measure the reconstructed phase distribution information.

[0016] Furthermore, the radiation source is placed in a lead shielding shell.

[0017] Furthermore, the radiation source includes 241 Am and 135 Cs.

[0018] The measuring method based on the alkali metal heat pipe phase distribution measuring device comprises the following steps:

[0019] S1. Adjust the ray collimator so that the gamma ray beam in the alkali metal heat pipe is a wide-beam gamma ray, perform multiple angle measurements on the same cross section of the alkali metal heat pipe so that the wide-beam gamma rays at multiple angles fully cover the cross section, and measure the cross-sectional phase fraction inside the alkali metal heat pipe;

[0020] S2. Adjust the ray collimator so that the gamma ray beam in the alkali metal heat pipe is a narrow-beam gamma ray. Perform multiple angle measurements on the same cross section of the alkali metal heat pipe so that the narrow-beam gamma rays at multiple angles fully cover the cross section. The measured linear phase fraction of the alkali metal heat pipe at each angle is obtained.

[0021] Furthermore, in step S1, a plurality of measuring devices are arranged in a circular array to measure the cross-sectional phase fraction, or the cross-sectional phase fraction is measured by circumferentially rotating the same measuring device.

[0022] Furthermore, in step S1, the line phase fraction is measured by arranging a plurality of measuring devices in a circular array, or by rotating the same measuring device in a circumferential direction.

[0023] Furthermore, in step S1, the calculation formula of the cross-sectional phase fraction α is as follows:

[0024]

[0025] Where I is the emission intensity, Among them, μ r is the average linear attenuation coefficient of the sample, d is the sample thickness, I0 is the initial activity; I L and I G It is a quantity used for calibration. The subscripts L and G refer to the working conditions when the pipeline is full of liquid phase or full of gas phase respectively.

[0026] Furthermore, in step S1, the line phase fraction α line The calculation formula is as follows:

[0027]

[0028] Where I is the emission intensity, Among them, μ r is the average linear attenuation coefficient of the sample, d is the sample thickness, I0 is the initial activity; I L and I G It is a quantity used for calibration. The subscripts L and G refer to the working conditions when the pipeline is full of liquid phase or full of gas phase respectively.

[0029] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0030] 1. The measuring device of the present invention can realize the gas-liquid two-phase distribution measurement of alkali metal heat pipes.

[0031] 2. The measuring device of the present invention has a simple structure and the measuring method is easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0033] Figure 1 It is a schematic diagram of wide beam gamma ray measurement of the alkali metal heat pipe measurement device of the present invention;

[0034] Figure 2 This is a schematic diagram of the layout of a wide beam gamma array with the same cross section;

[0035] Figure 3It is a schematic diagram of narrow beam gamma ray measurement of the alkali metal heat pipe measurement device of the present invention;

[0036] Figure 4 This is a schematic diagram of the arrangement of a narrow beam gamma array with the same cross section;

[0037] Figure 5 Schematic diagram of reconstruction for phase distribution scanning measurement.

[0038] Marks and corresponding parts names in the attached drawings:

[0039] 1-heat pipe evaporation section, 2-heat pipe insulation section, 3-heat pipe condensation section, 4-heat pipe cladding, 5-heat pipe liquid absorption core, 6-heat pipe central air cavity, 7-insulation layer, 8-ray source, 9-ray collimator, 10-scintillator detector, 11-gamma ray beam, 12-lead shielding shell. DETAILED DESCRIPTION

[0040] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0041] Embodiment 1:

[0042] like Figure 1-Figure 5 As shown, the alkali metal heat pipe phase distribution measuring device includes a radiation source 8, a radiation collimator 9 and a scintillator detector 10;

[0043] The ray source 8 and the scintillator detector 10 are respectively placed at two ends of the alkali metal heat pipe in a radial direction, and the ray source 8 and the receiving scintillator detector 10 are respectively used to emit gamma rays;

[0044] The ray collimator 9 is arranged at the front end of the ray source 8, and is used to adjust the beam intensity of the gamma rays; the beam formed by the gamma rays after being collimated by the ray collimator 9 includes narrow-beam gamma rays and wide-beam gamma rays; the wide-beam gamma rays are used to measure phase distribution information; the narrow-beam gamma rays are used to measure reconstructed phase distribution information.

[0045] In this embodiment, the radiation source 8 is placed in the lead shielding shell 12; the radiation source 8 is 241 Am or 135 Cs.

[0046] The alkali metal heat pipe is composed of a heat pipe evaporation section 1, a heat pipe insulation section 2, a heat pipe condensation section 3, a heat pipe cladding 4, a heat pipe liquid wick 5, an air cavity 6, and an insulation layer 7 of the insulation section. The measuring device described in this embodiment can be loaded at any position of the heat pipe evaporation section 1, the heat pipe insulation section 2 and the heat pipe condensation section 3 that needs to be detected, and can also be designed as multiple gamma rays to form an array, so as to perform real-time measurement at the same position but different angles of the heat pipe, or at the same angle but different heat pipe positions at the same position.

[0047] The gamma rays emitted by the ray source 8 are collimated by the ray collimator 9 and then transmitted in the heat pipe to form a conical gamma ray beam 11. After the gamma ray beam 11 transmits the heat pipe, the phase distribution on the ray path can be inversely calculated by the intensity of the gamma rays.

[0048] The installation position of the radiation measuring device can be moved along the length direction of the heat pipe, so as to obtain the phase distribution of the heat pipe at different positions.

[0049] Multiple gamma ray devices can be arranged at the same heat pipe cross section to form array measurement. The scintillator detector 10 is used to receive information of the transmitted gamma ray, and the channel address of the scintillator detector 10 can be set to select and match the corresponding gamma ray energy.

[0050] The gamma ray attenuation method is used to measure phase content, which is based on the exponential attenuation law of gamma rays. The gamma source can be regarded as a point source, and the emission intensity I can be expressed as:

[0051]

[0052] Among them, μ r is the average linear attenuation coefficient of the sample, d is the sample thickness, and I0 is the initial activity.

[0053] It is worth noting that after the gamma rays are collimated and enter the pipeline, the coverage range is not the entire flow channel but a conical range. The size of the cone beam in the measurement can be adjusted by the ray collimator 9 behind the gamma ray source and the receiving area of ​​the scintillator detector 10. It can be divided into two situations: narrow beam gamma ray detection and wide beam gamma ray detection.

[0054] The measurement method of this embodiment includes the following steps:

[0055] S1. Adjust the ray collimator 9 so that the gamma ray beam in the alkali metal heat pipe is a wide-beam gamma ray, perform multiple angle measurements on the same cross section of the alkali metal heat pipe so that the wide-beam gamma rays at multiple angles fully cover the cross section, and measure the cross-sectional phase fraction inside the alkali metal heat pipe; use a ring array to arrange multiple measuring devices to measure the cross-sectional phase fraction, or use a circumferential rotation of the same measuring device to measure the cross-sectional phase fraction;

[0056] S2. Adjust the ray collimator 9 so that the gamma ray beam in the alkali metal heat pipe is a narrow-beam gamma ray, perform multiple angle measurements on the same cross section of the alkali metal heat pipe so that the narrow-beam gamma rays at multiple angles fully cover the cross section, and measure the linear phase fraction of the alkali metal heat pipe at each angle; use a ring array to arrange multiple measuring devices to achieve the measurement of the linear phase fraction, or use a circumferential rotation of the same measuring device to achieve the measurement of the linear phase fraction.

[0057] Specifically:

[0058] Case of wide beam gamma ray detectors:

[0059] The measured cross-sectional phase fraction α inside the alkali metal heat pipe can be expressed by the following formula:

[0060]

[0061] Where I is the emission intensity, Among them, μ r is the average linear attenuation coefficient of the sample, d is the sample thickness, I0 is the initial activity; I L and I G It is a quantity used for calibration. The subscripts L and G refer to the working conditions when the pipeline is full of liquid phase or full of gas phase respectively.

[0062] Similarly, the liquid holdup, ε L , can be calculated using the following relationship:

[0063] ε L =1-α

[0064] like Figure 1 Wide-beam gamma rays can present information about phase fractions in a relatively large range; multiple gamma-ray measurement devices can also be used to perform measurements at different angles. Using wide-beam gamma rays for multiple angle measurements can cover a larger range, such as Figure 2 shown.

[0065] The case of narrow beam gamma ray detectors:

[0066] like Figure 3 , narrow beam gamma rays can reflect the phase fraction information on a specific straight line;

[0067] By using narrow beam gamma rays to measure at multiple angles, the attenuation information on multiple straight lines inside the alkali metal heat pipe can be obtained, such as Figure 4 As shown, the internal information at multiple angles can be measured. The detector can be rotated to obtain the internal information at each angle. In order to distinguish it from the cross-sectional phase fraction in the usual sense, we call this measurement result the line phase fraction, denoted by α line Linear phase fraction α lineAs the measurement angle θ of the gamma ray system changes, it can be calculated using:

[0068]

[0069] Where I is the emission intensity. When other conditions are constant, as the proportion of gas phase and liquid phase changes, The subscripts L and G refer to the operating conditions when the pipeline is full of liquid phase or full of gas phase, respectively. L and I G It is the quantity used for calibration.

[0070] Similarly, the line holdup, ε L,line , can be calculated using the following relationship:

[0071] ε L,line (θ)=1-α(θ)

[0072] Scanning measurement method of narrow beam gamma ray detector:

[0073] like Figure 4 , multiple narrow-beam gamma detectors can be used to accurately measure information on multiple straight lines. At the same time, the gamma rays can be set to rotate along the tangent direction to measure at different angles:

[0074] θ(t)=ωt

[0075] The measured phase distribution information is as follows:

[0076]

[0077] Scanning measurements are performed to obtain information on the cross-sectional phase content on each straight line inside the heat pipe and to reconstruct the internal phase distribution, such as Figure 5 shown.

[0078] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for measuring phase distribution of an alkali metal heat pipe, characterized in that: The measuring device used in the measuring method comprises a ray source (8), a ray collimator (9) and a scintillator detector (10); the ray source (8) and the scintillator detector (10) are respectively arranged at two ends of the alkali metal heat pipe in a radial direction, and the ray source (8) and the receiving scintillator detector (10) are respectively used to emit gamma rays and receive information of gamma rays after transmission; the ray collimator (9) is arranged at the front end of the ray source (8) and is used to adjust the beam intensity of the gamma rays; the beam formed by the gamma rays after being collimated by the ray collimator (9) comprises narrow-beam gamma rays and wide-beam gamma rays; the wide-beam gamma rays are used to measure phase distribution information; the narrow-beam gamma rays are used to measure reconstructed phase distribution information; the ray source (8) comprises 241Am and 135Cs; The measurement method includes the following steps: S1. Adjusting the ray collimator (9) so that the gamma ray beam in the alkali metal heat pipe is a wide-beam gamma ray, performing multiple angle measurements on the same cross section of the alkali metal heat pipe so that the wide-beam gamma rays at multiple angles fully cover the cross section, and measuring the cross-sectional phase fraction inside the alkali metal heat pipe; S2, adjusting the ray collimator (9) so that the gamma ray beam in the alkali metal heat pipe is a narrow beam gamma ray, performing multiple angle measurements on the same cross section of the alkali metal heat pipe so that the narrow beam gamma rays at multiple angles fully cover the cross section, and measuring the linear phase fraction of the alkali metal heat pipe at each angle; During measurement, a linear guide rail and an annular guide rail parallel to the central axis of the alkali metal heat pipe are arranged on the outer side of the alkali metal heat pipe; In step S1, a plurality of measuring devices are arranged in a circular array to measure the cross-sectional phase fraction, or the cross-sectional phase fraction is measured by circumferentially rotating the same measuring device; In step S1, a plurality of measuring devices are arranged in a circular array to measure the line phase fraction, or the line phase fraction is measured by rotating the same measuring device in a circumferential direction; The radiation source (8) is placed in a lead shielding shell (12).

2. The method for measuring phase distribution of an alkali metal heat pipe according to claim 1, characterized in that: In step S1, the calculation formula of the cross-sectional phase fraction α is as follows: Where I is the emission intensity, Where μr is the average linear attenuation coefficient of the sample, d is the sample thickness, and I0 is the initial activity. IL and IG are quantities used for calibration, and the subscripts L and G refer to the working conditions when the pipeline is full of liquid or full of gas, respectively.

3. The method for measuring phase distribution of an alkali metal heat pipe according to claim 1, characterized in that: In step S1, the calculation formula of the line phase fraction αline is as follows: Where I is the emission intensity, Where μr is the average linear attenuation coefficient of the sample, d is the sample thickness, and I0 is the initial activity. IL and IG are quantities used for calibration, and the subscripts L and G refer to the working conditions when the pipeline is full of liquid or full of gas, respectively.

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