Device and method for combined measurement of physical properties of high-temperature molten salt based on multilayer heat transfer model

Abstract

The invention discloses a high-temperature molten salt physical property combined measurement device and method based on a multilayer heat transfer model, and relates to a combined measurement device and method. The invention aims to solve the problem that an existing high-temperature molten salt thermophysical property testing device model does not consider internal volume radiation and heat transfer of a packaging container. A laser is connected with an optical fiber collimator through a transmission optical fiber, the optical fiber collimator is arranged below a constant-temperature heating furnace, the constant-temperature heating furnace is placed on a support, a graphite crucible is arranged in the middle of the inner bottom face of the constant-temperature heating furnace, a cover covers the graphite crucible, and a varifocal lens system is arranged over the constant-temperature heating furnace. The zoom lens system is arranged on the upper surface of the cover, the focus of the zoom lens system is located in the center of the upper surface of the cover, the high-sensitivity infrared detector collects infrared signals penetrating through the zoom lens system, the output end of the high-sensitivity infrared detector is connected with the receiving end of the Fourier transform infrared spectrometer, and the Fourier transform infrared spectrometer is connected with the computer. The invention belongs to the technical field of thermophysical property measurement of high-temperature materials.

Description

Technical Field

[0001] The present invention relates to a combined measurement device and method based on a multi-layer heat transfer model, belonging to the technical field of measuring thermal physical properties of high-temperature materials. Background Technique

[0002] Molten salt has many advantages such as a wide working range of phase change temperature, low vapor pressure, moderate viscosity, and good stability, and is widely used in industrial high-temperature waste heat recovery, solar thermal power generation, and other heat transfer / heat storage fields. The accuracy of the thermal physical properties of molten salt is directly related to the safe design of the system. However, the existing test data of molten salt are of low reliability due to the long time and limited test technology, and it is difficult to meet the use requirements. Therefore, the accurate measurement of the thermal physical properties of molten salt has become an urgent problem to be solved. The existing test technology for the thermal physical properties of molten salt is not well developed, especially the test model does not consider the volumetric radiation effect inside the high-temperature molten salt and the heat transfer effect of the encapsulation container. Summary of the Invention

[0003] In order to solve the problem that the existing test device model for the thermal physical properties of high-temperature molten salt does not consider the internal volumetric radiation and the heat transfer of the encapsulation container, the present invention further provides a combined measurement device and method for the physical properties of high-temperature molten salt based on a multi-layer heat transfer model.

[0004] The technical solution adopted by the present invention to solve the above problems is: A combined measurement device for the physical properties of high-temperature molten salt based on a multi-layer heat transfer model of the present invention includes a laser, an optical fiber collimator, a constant-temperature heating furnace, a graphite crucible, a lid, a variable focal length lens system, a high-sensitivity infrared detector, a Fourier transform infrared spectrometer, and a computer;

[0005] The laser is connected to the optical fiber collimator through a transmission optical fiber. The optical fiber collimator is arranged below the constant-temperature heating furnace. The constant-temperature heating furnace is placed on a bracket. The graphite crucible is arranged in the middle of the inner bottom surface of the constant-temperature heating furnace. The lid is covered on the graphite crucible. The variable focal length lens system is arranged directly above the constant-temperature heating furnace, and the focus of the variable focal length lens system is located at the center of the upper surface of the lid. The high-sensitivity infrared detector collects the infrared signal passing through the variable focal length lens system. The output end of the high-sensitivity infrared detector is connected to the receiving end of the Fourier transform infrared spectrometer, and the Fourier transform infrared spectrometer is connected to the computer.

[0006] The steps of a combined measurement method for the physical properties of high-temperature molten salt based on a multi-layer heat transfer model of the present invention include:

[0007] Step 1: Connect the laser with a built-in cooling system to the optical fiber collimator through a transmission optical fiber, and adjust the position of the optical fiber collimator so that the laser beam passes through the center position of the optical window at the bottom of the constant-temperature heating furnace;

[0008] Step 2, injecting the pre-melted salt into a packaging container consisting of a graphite crucible and a lid, wherein the graphite crucible is located at the center of the bottom of the constant temperature heating furnace;

[0009] Step 3: Check whether the interfaces of the constant temperature heating furnace are closed and whether the temperature control equipment is working normally. After checking, close the furnace door and turn on the heating switch. Heat the temperature in the furnace to T 0 Then keep the temperature constant;

[0010] Step 4, adjusting the focal length of the zoom lens system so that the focus is located at the center of the upper surface of the cover, and the high-sensitivity infrared detector captures the infrared signal of the upper surface of the molten salt cover in real time;

[0011] Step 5: After the preparation work is completed, turn on the laser to officially start the experiment, and output a stable and modulatable laser pulse beam;

[0012] Step 6, the laser beam passes through the fiber collimator and irradiates the bottom of the graphite crucible to generate a temperature gradient, which triggers a temperature response on the upper surface of the lid through two heat transfer mechanisms: thermal diffusion and volume radiation. A high-sensitivity infrared detector collects infrared signals emitted from the upper surface of the lid.

[0013] Step 7, the infrared measurement signal is transmitted from the high-sensitivity detector to the Fourier transform infrared spectrometer, the Fourier transform infrared spectrometer performs Fourier transform on the measurement signal, and the transformed result is input into the computer, and the thermal conductivity and absorption coefficient of the high-temperature molten salt are calculated by the established multi-layer transient measurement model and the adaptive chaotic particle swarm optimization algorithm;

[0014] Step 8: Repeat the experiment 10 times and take the average value.

[0015] Furthermore, the multilayer transient heat transfer model considering the heat transfer of the graphite crucible and the lid along the thickness direction and the internal volume radiation of the high-temperature molten salt is:

[0016]

[0017] In formula ①, ρ represents density, c p represents specific heat, k represents thermal conductivity, q r represents the radiation heat flow inside the medium, subscripts 1, 2 and 3 represent the graphite crucible, the molten salt layer to be measured and the lid respectively, and the thickness of the bottom of the graphite crucible is recorded as L 1 , the thickness of the molten salt layer is recorded as l, and the thickness of the bottom of the lid is recorded as L 3 ;

[0018] The thermal boundary conditions and initial conditions are:

[0019]

[0020] T(x,0)=Ts , at t = 0③,

[0021] The radiation source term ▽·q in the energy equation r is written as:

[0022]

[0023] In Equation ④, I represents the radiation intensity and is obtained by solving the radiation transfer equation:

[0024]

[0025] In Equation ⑤, μ = cosθ represents the direction cosine, θ represents the zenith angle (rad), n represents the refractive index of the medium, and κ α represents the absorption coefficient of the medium. Since there are basically no suspended particles in the pure molten salt after melting, internal light scattering can be ignored, and only radiation absorption is considered; the radiation boundary condition is:

[0026]

[0027] In Equation ⑥, n w represents the unit normal vector of the wall surface, s m' represents the unit direction vector in the direction m', and ε w represents the emissivity of the inner surface of the container.

[0028] Furthermore, the specific steps of the adaptive chaotic particle swarm optimization algorithm in Step 7 are as follows:

[0029] Step 701: Define the objective function where x = (x 1 , x 2 , …, x n ) is the parameter vector to be inverted. The subscripts “est” and “mea” represent the predicted and experimentally measured temperature signals during the inversion process, which are input into the computer by a Fourier transform infrared spectrometer. The superscript “t” represents the sampling time of the measurement signal;

[0030] Set the population size N, the maximum number of iterations G, the minimum and maximum inertia weights to be w min = 0.4, w max = 0.9, set the acceleration constants C 1 = C 2 = 1.5, and the upper and lower bounds of the search space [x min , x max ;

[0031] Step 702: Randomly initialize the velocity vector X of the particles i (t) = (x i1 , x i2 , …, xin ), where \(i = 1, 2, \ldots, N\), and \(x\) ij \(\in [x\) min , \(x\) max , randomly initialize the velocity vector \(V\) i (t) = \((v\) i1 , \(v\) i2 , \ldots, \(v\) in ), and \(v\) ij \(\in [-v\) min , \(v\) max , \(v\) max is the preset maximum velocity, calculate the initial fitness value \(P\) i (t) = f(x\) i ), obtain the fitness value of the optimal particle in the population

[0032] Step 703: For each particle, perform velocity update and position update. \(w\) is the inertia weight function, \(t\) is the current iteration number, \(G\) is the total number of iterations, \(R\) 1 , \(R\) 2 are random numbers in \([0, 1]\);

[0033] \(w = w\) max + \((w\) max - \(w\) min ) \times \mu⑦,

[0034]

[0035] \(V\) i (t + 1) = wV\) i (t) + C\) 1 \cdot \(R\) 1 \cdot [P\) i (t) - \(X\) i (t)] + C\) 2 \cdot \(R\) 2 [P\) g (t) - \(X\) i (t)]⑨,

[0036] \(X\) i (t + 1) = \(X\) i (t) + \(V\) i (t + 1)⑩;

[0037] Step 704: Calculate the fitness value \(f(x\) i (t + 1)) of the particle after updating the position, find the individual optimal and global optimal particles. If \(f(x\) i (t + 1)) < \(P\) i , then \(P\) i = \(f(x\) i (t + 1)), and update \(P\) iThe corresponding position;

[0038] If Then And update P g The corresponding particle position;

[0039] Step 705: Sort the particles in Step 704 in ascending order of their fitness values, select the top N / 5 particles to execute the chaotic local search algorithm, and update the positions of these particles;

[0040] Step 706: Determine whether the iteration step t reaches the maximum number of iterations G. If it is satisfied, execute Step 707; otherwise, turn to Step 703;

[0041] Step 707: The search stops, and the position information of the global optimal particle P g is output, that is, the thermal conductivity k and absorption coefficient k a of the parameter to be measured.

[0042] The beneficial effects of the present invention are as follows: The present invention establishes a multi-layer transient heat transfer model considering heat transfer along the thickness direction of the graphite crucible and the lid and volumetric radiation inside the high-temperature molten salt, corrects the deficiencies in the traditional laser flash method measurement model that do not consider relevant factors, makes the measurement model more in line with the actual situation, and thus provides a theoretical basis for accurately measuring the thermal conductivity and absorption coefficient of high-temperature molten salt; through the collaborative work of a high-sensitivity infrared detector and a Fourier transform infrared spectrometer, the interference of background radiation can be effectively removed; during the measurement process, by adjusting the focal length of the variable focal length lens system, a part of the background radiation is removed. After the infrared signal captured by the high-sensitivity infrared detector passes through the Fourier transform infrared spectrometer, the signal related to the physical properties of the molten salt itself can be obtained more accurately, improving the accuracy of the measurement results; in terms of the inversion algorithm, the present invention establishes an adaptive chaotic particle swarm optimization algorithm, which improves the defect that the traditional particle swarm algorithm is prone to fall into local optimum. Description of the Drawings

[0043] Figure 1 is a schematic structural diagram of a high-temperature molten salt physical property joint measurement device based on a multi-layer heat transfer model according to the present invention;

[0044] Figure 2 is a schematic diagram of the conventional infrared detection field of view and the human-computer interaction infrared detection field of view with a variable focal length lens system added;

[0045] Figure 3 is the temperature rise curve of the upper surface of the molten salt layer under each measurement model;

[0046] Figure 4 is a schematic diagram of the joint inversion results of the thermal conductivity and absorption coefficient of the adaptive chaotic particle swarm optimization algorithm established by the present invention;

[0047] Figure 2 The detection field of view of the medium and high sensitivity infrared detector 7 not only includes the upper surface of the lid 5 of concern, but also includes the convex cross-section of the lid 5 and the test environments on both sides, causing the high sensitivity infrared detector 7 to collect unnecessary stray infrared radiation information, which will lead to the oscillation distortion of the signal curve. In order to suppress the influence of the stray radiation signal, the optical path is reasonably designed to flexibly control the field of view of the high sensitivity infrared detector 7 and accurately obtain the transient temperature change response in the millisecond order, as shown in the appendix. Figure 2 The zoom lens system is located between the high sensitivity infrared detector 7 and the constant temperature heating furnace 5, and the field of view is adjusted through human-computer interaction to adapt to specific sample sizes and applications. Specific implementation mode

[0048] Specific implementation mode 1: As shown in the figure, a high-temperature molten salt physical property joint measurement device based on a multi-layer heat transfer model includes a laser 1, an optical fiber collimator 2, a constant temperature heating furnace 3, a graphite crucible 4, a lid 5, a zoom lens system 6, a high sensitivity infrared detector 7, a Fourier transform infrared spectrometer 8, and a computer 9; Figure 1 The laser 1 is connected to the optical fiber collimator 2 through a transmission optical fiber. The optical fiber collimator 2 is arranged below the constant temperature heating furnace 3. The constant temperature heating furnace 3 is placed on a bracket. The graphite crucible 4 is arranged in the middle of the inner bottom surface of the constant temperature heating furnace 3. The lid 5 is covered on the graphite crucible 4. The zoom lens system 6 is arranged directly above the constant temperature heating furnace 3, and the focus of the zoom lens system 6 is located at the center of the upper surface of the lid 5. The high sensitivity infrared detector 7 collects the infrared signal passing through the zoom lens system 6. The output end of the high sensitivity infrared detector 7 is connected to the receiving end of the Fourier transform infrared spectrometer 8, and the Fourier transform infrared spectrometer 8 is connected to the computer 9.

[0049] Among them, the central positions of the optical fiber collimator 2, the graphite crucible 4, the lid 5, the zoom lens system 6, and the high sensitivity infrared detector 7 are located on the same axis;

[0050] Among them, the laser power of the laser 1 is adjustable, the laser waveform is adjustable, and the pulse width is adjustable within 0.01 ms to 20 ms;

[0051] Among them, the optical fiber collimator 2 is the F810SMA-780 produced by THORLAB in the United States, and the diameter range of the collimated light beam is 6.0 - 8.0 mm;

[0052] Among them, the constant temperature heating furnace 3 is closed and the internal atmosphere is guaranteed to be a vacuum, and optical windows are installed at the central positions of the upper and lower surfaces;

[0053] Among them, the constant temperature heating furnace 3 is closed and the internal atmosphere is guaranteed to be a vacuum, and optical windows are installed at the central positions of the upper and lower surfaces;

[0054] Among them, the bottom of the graphite crucible 4 is coated with a graphite coating, the inner side wall is coated with a zirconia coating, and the inner bottom is coated with a graphite coating;

[0055] Among them, the zoom lens system 6 can be moved up and down to dynamically adjust the field of view range.

[0056] During the test, the center of the sample is always coaxial with the center of the optical window, that is, it is ensured that the graphite crucible 4 is placed at the center position inside the constant temperature heating furnace; the bottom of the graphite crucible 4 is coated with a graphite coating with high absorptivity, and the inner side wall is coated with a zirconia coating with low thermal conductivity to avoid heat transfer along the radial direction.

[0057] Appendix Figure 3 is the temperature rise curve of the upper surface of the molten salt layer under each measurement model. It can be seen that after considering the internal volume radiation in the test model, a spike will appear at the position of the temperature rise curve after the laser pulse beam heating ends. When further considering the influence of the heat transfer of the encapsulation container, the height of the spike decreases. When only considering the pure heat conduction inside the molten salt, the first peak of the curve disappears.

[0058] Appendix Figure 4 is the joint inversion result of the thermal conductivity and absorption coefficient by the self-adaptive chaotic particle swarm optimization algorithm established in the present invention considering the measurement error γ. It can be seen that as the measurement error γ increases, the relative error between the inversion result and the true value also increases. When the measurement error γ = 3%, the relative error between the inversion result and the true value is also acceptable, indicating that the inversion optimization algorithm established in the present invention has good robustness

[0059] Specific Embodiment 2: As Figures 1 to 4 shown, a method for jointly measuring the physical properties of high-temperature molten salts based on a multi-layer heat transfer model, the specific steps include:

[0060] Step 1: Connect the laser 1 with a built-in cooling system to the fiber collimator 2 through a transmission fiber, and adjust the position of the fiber collimator 2 so that the laser beam passes through the center position of the optical window at the bottom of the constant temperature heating furnace 3;

[0061] Step 2: Inject the pre-molten salt into the encapsulation container composed of the graphite crucible 4 and the lid 5. Further define that the graphite crucible 4 is located at the center position at the bottom of the constant temperature heating furnace 3;

[0062] Step 3: Check whether each interface of the constant temperature heating furnace 3 is closed and whether the temperature control equipment is working properly. After checking, close the furnace door and turn on the heating switch. Heat the temperature inside the furnace to T 0 and then keep the temperature constant;

[0063] Step 4: Adjust the focal length of the zoom lens system 6 so that it is located at the center of the upper surface of the lid 5, and the high-sensitivity infrared detector 7 captures the infrared signal on the upper surface of the molten salt lid 5 in real time;

[0064] Step 5: After the preparatory work is completed, turn on the laser 1 to officially start the experiment, and output a stable and modulated laser pulse beam;

[0065] Step 6: After the laser beam passes through the fiber collimator 2, it irradiates the bottom of the graphite crucible 4, generating a temperature gradient. Through two heat transfer mechanisms, namely thermal diffusion and volumetric radiation, a temperature response is induced on the upper surface of the lid 5, and the high-sensitivity infrared detector 7 collects the infrared signal emitted from the upper surface of the lid 5;

[0066] Step 7: The infrared measurement signal is transmitted from the high-sensitivity detector 7 to the Fourier transform infrared spectrometer 8. The Fourier transform infrared spectrometer 8 performs a Fourier transform on the measurement signal, and the transformed result is input into the computer 9. The thermal conductivity and absorption coefficient of the high-temperature molten salt are calculated through the established multi-layer transient measurement model and the self-adaptive chaotic particle swarm optimization algorithm;

[0067] Step 8: Repeat the experiment 10 times and take the average value.

[0068] Among them, the multi-layer transient heat transfer model considering heat transfer in the thickness direction of the graphite crucible 4 and the lid 5 as well as volumetric radiation inside the high-temperature molten salt is:

[0069]

[0070] In formula ①, ρ represents density, c p represents specific heat, k represents thermal conductivity, q r represents the internal radiation heat flux of the medium, and the subscripts 1, 2, and 3 represent the graphite crucible 4, the molten salt layer to be measured, and the lid 5 respectively. The thickness of the bottom of the graphite crucible 4 is denoted as L 1 , the thickness of the molten salt layer is denoted as l, and the thickness of the bottom of the lid 5 is denoted as L 3 ;

[0071] The thermal boundary conditions and initial conditions are:

[0072]

[0073] T(x, 0) = T s , t = 0 ③,

[0074] The radiation source term ▽·q in the energy equation r is written as:

[0075]

[0076] In formula ④, I represents radiation intensity, which is obtained by solving the radiation transfer equation:

[0077]

[0078] In Equation ⑤, μ = cosθ represents the direction cosine, θ represents the zenith angle (rad), n represents the refractive index of the medium, and κ α represents the medium absorption coefficient. Since there are basically no suspended particles in the pure molten salt after melting, internal light scattering can be ignored, and only radiative absorption is considered; the radiation boundary condition is:

[0079]

[0080] In Equation ⑥, n w represents the unit normal vector of the wall surface, s m' represents the unit direction vector in the direction m', and ε w represents the emissivity of the inner surface of the container.

[0081] Among them, the specific steps of the adaptive chaotic particle swarm optimization algorithm in Step 7 are as follows:

[0082] Step 701, define the objective function where x = (x 1 , x 2 , …, x n ) is the parameter vector to be inverted. The subscripts “est” and “mea” represent the predicted and experimentally measured temperature signals during the inversion process, which are input into the computer 9 by the Fourier transform infrared spectrometer 8. The superscript “t” represents the sampling time of the measurement signal;

[0083] Set the population size N, the maximum number of iterations G, the minimum and maximum inertia weights to be w min = 0.4, w max = 0.9, set the acceleration constants C 1 = C 2 = 1.5, and the upper and lower bounds of the search space [x min , x max ;

[0084] Step 702, randomly initialize the velocity vector X i (t) = (x i1 , x i2 , …, x in ), where i = 1, 2, …, N, and x ij ∈[x min , x max . Randomly initialize the velocity vector V i (t) = (v i1 , v i2 , …, v in ), and v ij ∈[-v min , v max , v maxis the preset maximum speed, and calculate the initial fitness value P of each particle i (t) = f(x i ), and obtain the fitness value of the optimal particle in the population

[0085] Step 703: For each particle, perform velocity update and position update. w is the inertia weight function, t is the current iteration number, G is the total iteration number, R 1 、R 2 are random numbers within [0, 1];

[0086] w = w max +(w max - w min ) × μ⑦,

[0087]

[0088] V i (t + 1) = wV i (t)+C 1 ·R 1 ·[P i (t)-X i (t)]+C 2 ·R 2 [P g (t)-X i (t)]⑨,

[0089] X i (t + 1) = X i (t)+V i (t + 1)⑩;

[0090] Step 704: Calculate the fitness value f(x i (t + 1)) of the particle after updating the position, and find the individual optimal and global optimal particles. If f(x i (t + 1)) < P i , then P i = f(x i (t + 1)), and update the position corresponding to P i ;

[0091] If then and update the particle position corresponding to P g ;

[0092] Step 705: Sort the particles in Step 704 in ascending order of their fitness values, select the first N / 5 particles to execute the chaotic local search algorithm, and update the positions of these particles;

[0093] Step 706: Determine whether the iteration step t reaches the maximum number of iterations G. If satisfied, execute Step 707; otherwise, turn to Step 703;

[0094] Step 707: Stop the search and output the position information of the global optimal particle P g , that is, the thermal conductivity k and absorption coefficient k of the parameter to be measured a values.

[0095] As mentioned above, it is only a preferred embodiment of the present invention and does not impose any form of limitation on the present invention. Although the present invention has been disclosed above with the preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments with equivalent changes by using the disclosed technical content within the scope of the technical solution of the present invention. However, as long as it does not depart from the technical solution content of the present invention and is based on the technical essence of the present invention, any simple modification, equivalent replacement, and improvement made to the above embodiments still fall within the protection scope of the technical solution of the present invention.

Claims

1. A high-temperature molten salt physical property joint measurement device based on a multi-layer heat transfer model, characterized in that: It comprises a laser (1), an optical fiber collimator (2), a constant temperature heating furnace (3), a graphite crucible (4), a cover (5), a zoom lens system (6), a high-sensitivity infrared detector (7), a Fourier transform infrared spectrometer (8) and a computer (9); The laser (1) is connected to the optical fiber collimator (2) through a transmission optical fiber. The optical fiber collimator (2) is arranged below a constant temperature heating furnace (3). The constant temperature heating furnace (3) is placed on a bracket. A graphite crucible (4) is arranged at the middle of the inner bottom surface of the constant temperature heating furnace (3). A cover (5) is mounted on the graphite crucible (4). A zoom lens system (6) is arranged directly above the constant temperature heating furnace (3). The focus of the zoom lens system (6) is located at the center of the upper surface of the cover (5). A high-sensitivity infrared detector (7) collects infrared signals transmitted through the zoom lens system (6). The output end of the high-sensitivity infrared detector (7) is connected to the receiving end of a Fourier transform infrared spectrometer (8). The Fourier transform infrared spectrometer (8) is connected to a computer (9).

2. A combined measurement method for high-temperature molten salt properties based on a multi-layer heat transfer model, characterized in that: The specific steps include: Step 1, connecting a laser (1) with a built-in cooling system to a fiber collimator (2) via a transmission optical fiber, and adjusting the position of the fiber collimator (2) so that the laser beam passes through the center of the optical window at the bottom of a constant temperature heating furnace (3); Step 2, injecting the pre-melted salt into a packaging container consisting of a graphite crucible (4) and a cover (5), wherein the graphite crucible (4) is located at the center of the bottom of the constant temperature heating furnace (3); Step 3, check whether the interfaces of the constant temperature heating furnace (3) are closed and whether the temperature control equipment is working normally. After checking that everything is correct, close the furnace door and turn on the heating switch. After the temperature in the furnace is heated to T0, keep the temperature unchanged; Step 4, adjusting the focal length of the zoom lens system (6) so that it is located at the center of the upper surface of the cover (5), and the high-sensitivity infrared detector (7) captures the infrared signal of the upper surface of the molten salt cover (5) in real time; Step 5: After the preparation work is completed, turn on the laser (1) to officially start the experiment, and output a stable and modulatable laser pulse beam; Step 6, the laser beam passes through the optical fiber collimator (2) and irradiates the bottom of the graphite crucible (4), generating a temperature gradient, which causes the upper surface of the cover (5) to generate a temperature response through two heat transfer mechanisms: thermal diffusion and volume radiation. The high-sensitivity infrared detector (7) collects the infrared signal emitted by the upper surface of the cover (5); Step 7, the infrared measurement signal is transmitted from the high-sensitivity detector (7) to the Fourier transform infrared spectrometer (8), the Fourier transform infrared spectrometer (8) performs Fourier transform on the measurement signal, and the transformed result is input into the computer (9), and the thermal conductivity and absorption coefficient of the high-temperature molten salt are calculated by the established multi-layer transient measurement model and the adaptive chaotic particle swarm optimization algorithm; Step 8: Repeat the experiment 10 times and take the average value.

3. The method for joint measurement of high-temperature molten salt physical properties based on a multi-layer heat transfer model according to claim 2 is characterized in that: The multilayer transient heat transfer model considering the heat transfer along the thickness direction of the graphite crucible (4) and the lid (5) and the internal volume radiation of the high-temperature molten salt is: In formula ①, ρ represents density, c p represents specific heat, k represents thermal conductivity, q r represents the radiation heat flow inside the medium, the subscripts 1, 2 and 3 represent the graphite crucible (4), the molten salt layer to be measured and the cover (5), respectively, the bottom thickness of the graphite crucible (4) is recorded as L1, the thickness of the molten salt layer is recorded as l, and the bottom thickness of the cover (5) is recorded as L3; The thermal boundary conditions and initial conditions are: T(x,0)=T s ,t=0③, Radiation source term in the energy equation Written as: In formula ④, I represents the radiation intensity, which is obtained by solving the radiation transfer equation: In formula ⑤, μ = cosθ represents the direction cosine, θ represents the zenith angle (rad), n represents the refractive index of the medium, and κ α represents the medium absorption coefficient. Since there are basically no suspended particles after pure molten salt is melted, the internal light scattering can be ignored and only the radiation absorption effect is considered; the radiation boundary condition is: In formula ⑥, n w represents the normal vector outside the wall, s m' represents the unit direction vector in the direction m', ε w Represents the emissivity of the inner surface of the container.

4. The method for joint measurement of high-temperature molten salt physical properties based on a multi-layer heat transfer model according to claim 2 is characterized in that: The specific steps of the adaptive chaotic particle swarm optimization algorithm in step 7 are: Step 701: Define the objective function where x=(x1,x2,…,x n ) is the parameter vector to be inverted, the subscripts "est" and "mea" represent the temperature signals predicted and experimentally measured during the inversion process, respectively, which are input to the computer (9) by the Fourier transform infrared spectrometer (8), and the superscript "t" represents the sampling time of the measurement signal; Set the population size N, the maximum number of iterations G, the minimum and maximum inertia weights w respectively min =0.4, w max = 0.9, set the acceleration constant C1 = C2 = 1.5, the upper and lower bounds of the search space [x min ,x max ]; Step 702: Randomly initialize the particle's velocity vector X i (t) = (x i1 ,x i2 ,…,x in ), where i = 1, 2, ..., N, and x ij ∈[x min ,x max ], randomly initialize the velocity vector V of each particle i (t)=(v i1 ,v i2 ,…,v in ), and v ij ∈[-v min ,v max ],v max is the preset maximum speed, calculate the initial fitness value P of each particle i (t) = f(x i ), and obtain the optimal particle fitness value of the population Step 703: Update the velocity and position of each particle, w is the inertia weight function, t is the current iteration number, G is the total iteration number, R1 and R2 are random numbers in [0, 1]; in=in max +(in max -In min )×μ⑦, V i (t+1)=wV i (t)+C1·R1·[P i (t)-X i (t)]+C2·R2[P g (t)-X i (t)]⑨, X i (t+1)=X i (t)+V i (t+1)⑩; Step 704: Calculate the particle fitness value f(x i (t+1)), find the individual optimal and global optimal particles, if f(x i (t+1))<P i , then P i =f(x i (t+1)), and update P i The corresponding position; if but And update P g The corresponding particle position; Step 705: sort the particles in step 704 from low to high according to their fitness values, select the first N / 5 particles to execute the chaotic local search algorithm, and update the positions of these particles; Step 706: Determine whether the number of iteration steps t reaches the maximum number of iterations G. If so, proceed to step 707; otherwise, proceed to step 703. Step 707: Search stops and the global optimal particle P is output g The position information of the measured parameters is the thermal conductivity k and the absorption coefficient k a The value of .

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