A device and method for measuring high-frequency dry-wet dynamic characteristics of an inner wall of a circular channel

Abstract

The application discloses a kind of high-frequency dry-wet dynamic characteristic measuring device and method of circular channel inner wall.The working medium storage tank stores liquid working medium, and the two ends of the working medium storage tank are connected with the input end of temperature and pressure control system and the output end of condenser respectively through pipeline, the output end of temperature and pressure control system is connected with the input end of dry-wet dynamic capture system through pipeline, the output end of dry-wet dynamic capture system is connected with the input end of condenser through pipeline, the outer wall of circular channel is sleeved with metal film, and the sidewall of circular channel is embedded with thermocouple array.The method comprises embedding thermocouple on the sidewall of circular channel, obtaining temperature information on the thermocouple, obtaining the heat transfer coefficient of the inner sidewall of circular channel, and determining the dry-wet state of the inner sidewall of circular channel.The application solves the problem that the dry-wet dynamic of the inner wall of circular channel is difficult to visualize capture and analyze, and the device is simple and low in cost.

Description

Technical Field

[0001] This invention relates to a device and method for capturing the wet and dry dynamics of a pipe wall in the field of pipeline technology, and particularly to a device and method for measuring the high-frequency wet and dry dynamic characteristics of the inner wall of a circular channel. Background Technology

[0002] In many high-power liquid cooling systems, unstable gas-liquid phase transitions may occur within the heat dissipation channels. Therefore, capturing and analyzing the wet-dry dynamics of the channel walls is of great significance. When the channel walls become partially dry, the heat transfer coefficient drops sharply, heat dissipation efficiency decreases, and heat transfer deteriorates. This situation significantly impacts the lifespan of the heat dissipation walls and the safe and efficient operation of the entire cooling system. Therefore, capturing and analyzing the wet-dry dynamics of the heat dissipation channel walls and revealing the unstable phase transition heat transfer mechanism within the channels is crucial to preventing heat transfer deterioration.

[0003] Current technologies for capturing high-frequency wet-dry dynamics mostly rely on high-speed cameras to capture images and visualize the heat dissipation wall surface. While this method is intuitive and efficient, it cannot be applied to the wet-dry dynamics analysis of the inner walls of channels, especially circular channels. Therefore, existing technologies lack a device and method capable of capturing the high-frequency wet-dry dynamic characteristics of the inner walls of circular channels. Summary of the Invention

[0004] In order to solve the problems existing in the background art, the purpose of this invention is to design a device and method for measuring the high-frequency dry and wet dynamic characteristics of the inner wall of a circular channel.

[0005] The technical solution adopted in this invention is as follows:

[0006] I. A device for measuring the high-frequency wet and dry dynamic characteristics of the inner wall of a circular channel:

[0007] The device includes a working fluid storage tank, a temperature and pressure control system, a wet / dry dynamic capture system, a condenser, valves, a pressure sensor, a temperature sensor, and a flow sensor. The working fluid storage tank stores liquid working fluid. The output and input ends of the working fluid storage tank are connected to the input end of the temperature and pressure control system and the output end of the condenser via pipelines, respectively. Valves are installed on the pipelines from the working fluid storage tank to the temperature and pressure control system and the condenser. The output end of the temperature and pressure control system is connected to the input end of the wet / dry dynamic capture system via a pipeline. Valves, pressure sensors, temperature sensors, and flow sensors are sequentially installed on the pipeline from the temperature and pressure control system to the wet / dry dynamic capture system. The output end of the wet / dry dynamic capture system is connected to the input end of the condenser via a pipeline. Pressure sensors and temperature sensors are sequentially installed on the pipeline from the wet / dry dynamic capture system to the condenser.

[0008] The aforementioned wet and dry dynamic capture system includes a temperature acquisition module, a channel heating module, and a data analysis module, with both the channel heating module and the data analysis module connected to the temperature acquisition module.

[0009] The temperature acquisition module includes a circular channel, a thermocouple array, and a temperature acquisition device. The circular channel is an annular pipe open at both ends. The input and output ends of the circular channel are connected to the temperature and pressure control system and the condenser, respectively, through the pipes. A thermocouple array is embedded in the side wall of the circular channel. Each thermocouple in the thermocouple array is electrically connected to the data analysis module through the temperature acquisition device. The channel heating module includes a metal film and a power supply. The metal film is sleeved on the outer wall of the circular channel, and the metal film and the power supply are electrically connected. The power supply is used to heat the circular channel.

[0010] The data analysis module includes a signal amplifier, a signal converter, and a data analysis processor. The input terminal of the temperature acquisition device is connected to a thermocouple, the output terminal of the temperature acquisition device is connected to the input terminal of the signal amplifier, and the output terminal of the signal amplifier is connected between the signal converter and the data analysis processor.

[0011] The thermocouple array is mainly formed by two thermocouple lines arranged radially at intervals along a circular channel. Each thermocouple line is set along the axial direction of the circular channel. Each thermocouple line is composed of thermocouples arranged sequentially along the same straight line. The number and arrangement of thermocouples in the two thermocouple lines are the same and aligned.

[0012] II. A method for measuring the high-frequency dry and wet dynamic characteristics of the inner wall of a circular channel, comprising the following steps:

[0013] Step S1: Cover the circular channel to be tested with a thin metal film;

[0014] Step S2: Arrange several measuring points in the side wall of the circular channel, and embed a thermocouple at each measuring point location; the measuring points form two measuring point routes arranged along the axial direction of the circular channel, each measuring point route is formed by sequentially connecting measuring points along the same straight line, the two measuring point routes are arranged radially at intervals along the circular channel, and the number and arrangement of measuring points in the two measuring point routes are the same and aligned.

[0015] Step S3: Start the device and use the temperature acquisition device to collect the temperature information of the thermocouple;

[0016] Step S4: The temperature acquisition device transmits the acquired temperature information to the data analysis processor, which processes the data to obtain the heat transfer coefficient of the inner wall of the circular channel.

[0017] Step S5: Determine the dry / wet state of the inner wall of the circular channel by the heat transfer coefficient of the inner wall.

[0018] The specific steps for obtaining the heat transfer coefficient of the inner wall of the circular channel in step S4 are as follows:

[0019] Step S4.1: Take the measurement point route near the inner wall of the circular channel as the first measurement point route, and the measurement point route near the outer wall of the circular channel as the second measurement point route. Take the measurement point near the input end of the circular channel in the first measurement point route as the origin, and the axis of the circular channel as the Z-axis to establish a coordinate system.

[0020] Step S4.2: Construct the temperature fluctuation function at the measuring point using the data analysis processor. The temperature fluctuation function at the measuring point is f. k (t,z) is obtained by processing it in the following way:

[0021]

[0022] Among them, f k (t,z) represents the temperature at position z at time t in the k-th measurement route. The subscript k indicates the ordinal number of the measurement route, which is 1 or 2. N represents a preset constant, i represents -1 to N, and M represents the characteristic function sin(m j ·L z The largest order of Γ = 0, where j represents the range from 0 to M, and Γ() represents the gamma function; m j This indicates that the characteristic function sin(m) is satisfied. j ·L z The eigenvalues ​​when ) = 0, This represents the fitting coefficient of the temperature fluctuation function at the measuring point in the k-th measuring point route;

[0023] Step S4.3: Process the data using a data analysis processor to obtain the function of the axial temperature distribution on the inner wall of the circular channel as a function of time:

[0024]

[0025] Among them, T w (z,t) represents the temperature at position z on the inner wall of the circular channel at time t. This represents the first recursive coefficient in the k-th measurement point route. The first recursive coefficient is obtained by processing it according to the following formula:

[0026]

[0027]

[0028] a=λ / ρc

[0029] Where a is the thermal diffusivity of the circular channel material, λ is the thermal conductivity of the circular channel material, ρ is the density of the circular channel material, c is the specific heat capacity of the circular channel material, int() represents the floor function, and F n This represents the temperature distribution coefficient, where the subscript n ranges from 0 to int[2N-i].

[0030] Step S4.4: Process the data using a data analysis processor to obtain the function showing the change of the axial distribution of heat flux density on the inner wall of the circular channel over time:

[0031]

[0032] Where λ represents the thermal conductivity of the circular channel material, q w (z,t) represents the heat flux density at position z on the inner wall of the circular channel at time t. This represents the second recursive coefficient in the k-th measurement point route. The second recursive coefficient is obtained by the following formula:

[0033]

[0034]

[0035] Among them, R n Indicates the heat flux density distribution coefficient;

[0036] Step S4.5: The axial distribution of the heat transfer coefficient on the inner wall of the circular channel as a function of time is obtained by processing the following formula:

[0037]

[0038] Among them, h w (z,t) represents the heat transfer coefficient at position z on the inner wall of the circular channel at time t, where T l This represents the temperature of the internal working fluid at time t.

[0039] Step 5 specifically includes:

[0040] The dry / wet state of the inner wall of a circular channel can be determined by the heat transfer coefficient of the inner wall surface.

[0041] If the heat transfer coefficient of the inner wall of the circular channel is lower than the preset heat transfer coefficient threshold, the inner wall of the circular channel is considered to be in a dry state.

[0042] Otherwise, the inner wall of the circular channel is considered to be in a moist state.

[0043] The temperature distribution coefficient F n The following formula is used to obtain:

[0044]

[0045]

[0046]

[0047] Where l represents 0 to n, D l E represents the first coefficient. n-l R represents the third recursive coefficient. k r represents the radial distance between the k-th measuring point route and the inner wall of the circular channel. in The inner diameter of the circular channel is represented by p, which represents l to positive infinity, s represents 0 to p, g represents 1 to nl-1, and u represents 1 to ps.

[0048] The heat flux density distribution coefficient R n The following formula is used to obtain:

[0049]

[0050]

[0051] Among them, H l The second coefficient is represented by v, where v represents 0 to p-1 and w represents 1 to pv-1.

[0052] The beneficial effects of this invention are as follows:

[0053] 1. The method of the present invention simplifies the capture process, and the dry and wet dynamic characteristics of the inner wall surface can be obtained by processing the collected data.

[0054] 2. This invention provides a means of prediction. For parts that are difficult to visualize and observe, this invention can predict the dry and wet characteristics of the channel. Attached Figure Description

[0055] Figure 1 This is a schematic diagram of the device flow of the present invention;

[0056] Figure 2 This is a schematic diagram of the operation process of the wet and dry dynamic capture system;

[0057] Figure 3 This is a schematic diagram of the system and monitoring points under simulated operating conditions;

[0058] Figure 4 The simulation results for simulation condition 1 are shown in the figure. In the figure, a is a schematic diagram of the temperature distribution along the two measuring points over time, and b is a schematic diagram of the axial distribution of the calculated heat transfer coefficient of the inner wall over time.

[0059] Figure 5The following is a simulation result diagram for simulation condition 2. In the diagram, a is a schematic diagram of the temperature distribution along the two measuring points over time, b is a schematic diagram of the axial distribution of the calculated heat transfer coefficient of the inner wall over time, and c is a schematic diagram of the heat transfer coefficient at the locally dried-out location over time.

[0060] In the diagram: 1. Working fluid storage tank; 2. Temperature and pressure control system; 3. Dry and wet dynamic capture system; 4. Condenser; 5. Valve; 6. Pressure sensor; 7. Temperature sensor; 8. Flow sensor. Detailed Implementation

[0061] The present invention will be further described below with reference to the accompanying drawings and specific simulation examples. Those skilled in the art should understand that the simulation examples are merely illustrative of the invention and should not be construed as limiting its scope.

[0062] like Figure 1 As shown, the device includes a working fluid storage tank 1, a temperature and pressure control system 2, a wet / dry dynamic capture system 3, a condenser 4, valves 5, a pressure sensor 6, a temperature sensor 7, and a flow sensor 8. The working fluid storage tank 1 stores the liquid working fluid to be tested. The output and input ends of the working fluid storage tank 1 are connected to the input end of the temperature and pressure control system 2 and the output end of the condenser 4 respectively through pipelines. Valves 5 are installed on the pipelines from the working fluid storage tank 1 to the temperature and pressure control system 2 and the condenser 4. The output end of the temperature and pressure control system 2 is connected to the input end of the wet / dry dynamic capture system 3 through a pipeline. Valves 5, pressure sensors 6, temperature sensors 7, and flow sensors 8 are sequentially installed on the pipeline from the temperature and pressure control system 2 to the wet / dry dynamic capture system 3. The output end of the wet / dry dynamic capture system 3 is connected to the input end of the condenser 4 through a pipeline. Pressure sensors 6 and temperature sensors 7 are sequentially installed on the pipeline from the wet / dry dynamic capture system 3 to the condenser 4.

[0063] The temperature and pressure control system 2 includes a heater for regulating the temperature of the liquid working fluid and a delivery pump for regulating the pressure of the liquid working fluid.

[0064] like Figure 2 As shown, the device's wet and dry dynamic capture system 3 includes a temperature acquisition module, a channel heating module, and a data analysis module. Both the channel heating module and the data analysis module are connected to the temperature acquisition module. The temperature acquisition module includes a circular channel, a thermocouple array, and a temperature acquisition device. The circular channel is an annular pipe with openings at both ends. The input and output ends of the circular channel are connected to the output end of the temperature and pressure control system 2 and the input end of the condenser 4, respectively, through the pipes. A thermocouple array is embedded in the side wall of the circular channel. Each thermocouple in the thermocouple array is electrically connected to the data analysis module through the temperature acquisition device.

[0065] The channel heating module includes a metal film and a power supply. The metal film is sleeved on the outer wall of the circular channel, and the metal film and the power supply are electrically connected. The power supply is used to heat the circular channel.

[0066] The data analysis module includes a signal amplifier, a signal converter, and a data analysis processor. The input terminal of the temperature acquisition unit is connected to a thermocouple, the output terminal of the temperature acquisition unit is connected to the input terminal of the signal amplifier, and the output terminal of the signal amplifier is connected to the signal converter and the data analysis processor.

[0067] The thermocouple array is mainly formed by two thermocouple lines arranged radially at intervals along a circular channel. Each thermocouple line is set along the axial direction of the circular channel. Each thermocouple line is formed by sequentially connecting thermocouples in the same straight line along the axial direction of the circular channel. In specific implementation, each thermocouple line is composed of five thermocouples arranged at intervals along the axial direction of the circular channel. The number and arrangement of thermocouples in the two thermocouple lines are the same, and the arrangement positions are aligned one-to-one in the radial direction of the circular channel.

[0068] The working medium storage tank 1 is a small working medium storage tank. The working medium storage tank 1 stores liquid working medium to be tested and can output and recover the required and used liquid working medium. The temperature and pressure control system 2 is a system that can control the temperature and regulate the pressure of the transported liquid working medium. The temperature and pressure control system 2 can control and regulate the temperature and pressure of the liquid working medium required for the test.

[0069] In the wet and dry dynamic capture system 3, a thin metal film is added to the outer wall of the circular channel, and the circular channel is uniformly heated by an external direct current; simultaneously, the circular channel is configured according to the following... Figure 2 Thermocouples are arranged as shown to collect the temperature of the inner wall of the circular channel and transmit it to the temperature acquisition unit. The data analysis module uses the data signal from the temperature acquisition unit and analyzes the collected temperature through a signal amplifier, a signal converter, and a data analysis processor to obtain the dry and wet dynamics of the circular channel. The condenser 4 can cool and condense the gas-liquid two-phase working fluid in the high-frequency dry and wet dynamic characteristic testing device, turning it into a liquid working fluid. The valve 5 can adjust the working fluid required in each part of the device, so that the flow rate of the entire device can be adjusted within the required range.

[0070] The process of the device of the present invention is as follows:

[0071] The working fluid storage tank 1 stores the liquid working fluid to be tested. The liquid working fluid is transferred to the temperature and pressure control module 2 after passing through the flow-adjustable valve 5. Then, after being controlled by the flow of valve 5 and measured and monitored by the pressure sensor 6, temperature sensor 7, and flow sensor 8, it is transferred to the dry and wet dynamic capture system 3. In the dry and wet dynamic capture system 3, after data acquisition and analysis, the measurement is transmitted to the condenser 4 through the pressure sensor 6 and temperature sensor 7. The condenser 4 cools the gas-liquid two-phase working fluid in the dry and wet dynamic capture system 3 into a liquid working fluid, and then transports it back to the working fluid storage tank 1 under the control of valve 5.

[0072] The dry and wet dynamic capture system 3 of this invention uses an external direct current to heat the metal film on the outer wall of the channel. The arrangement or wrapping method of the metal film is shown in the schematic diagram. Figure 2 As shown, a thin metal film is placed or wrapped around the outside of the circular channel to be tested, and a direct current is applied to the thin metal film to achieve uniform heating of the outer wall of the circular channel by utilizing the thermal effect of resistance.

[0073] The method of the present invention includes the following steps:

[0074] Step S1: Cover the circular channel to be tested with a metal film that has good thermal and electrical conductivity and uniform texture.

[0075] Step S2: Several measuring points are arranged in the side wall of the circular channel, and a thermocouple is buried at each measuring point. The measuring points form two measuring point routes arranged along the axial direction of the circular channel. Each measuring point route is formed by sequentially connecting measuring points along the same straight line along the axial direction of the circular channel. The two measuring point routes are arranged radially along the circular channel to form a measuring point array. The number and arrangement of measuring points in the two measuring point routes are the same, and the arrangement positions are aligned radially in the circular channel.

[0076] In practice, thermocouples are buried at the same depth in the same way to measure the temperature change at the measuring point; the temperature change at the measuring point is collected by thermocouples buried inside the side wall of the circular channel; several measuring points are arranged at equal intervals along the axial direction at two given depths, and all measuring points are located in the same radial plane passing through the axis of the circular channel, with measuring points at different depths corresponding one-to-one.

[0077] Step S3: Start the device and use the temperature acquisition device to collect the temperature information obtained by the thermocouple;

[0078] Step S4: The temperature acquisition device transmits the acquired temperature information to the data analysis processor, which processes the data to obtain the heat transfer coefficient of the inner wall of the circular channel.

[0079] Step S5: Determine the dry / wet state of the inner wall of the circular channel by the heat transfer coefficient of the inner wall.

[0080] The specific steps for obtaining the heat transfer coefficient of the inner wall of the circular channel in step S4 are as follows:

[0081] Step S4.1: Take the measurement point route near the inner wall of the circular channel as the first measurement point route, and the measurement point route near the outer wall of the circular channel as the second measurement point route. Take the measurement point near the input end of the circular channel in the first measurement point route as the origin, and the axis of the circular channel as the Z-axis to establish a coordinate system.

[0082] Step S4.2: Construct the temperature fluctuation function at the measuring point using the data analysis processor. The temperature fluctuation function at the measuring point is f. k (t,z) is obtained by processing it in the following way:

[0083]

[0084] Among them, f k (t,z) represents the temperature at position z at time t in the k-th measurement route. The subscript k indicates the ordinal number of the measurement route, which is 1 or 2. z represents the coordinate on the Z-axis. t represents the time. N represents a preset constant, which is 4 or 5. i represents -1 to N, i = -1, 0, 1, 2, ..., N. M represents the characteristic function sin(m j ·L z The largest order of Γ = 0, where j represents the range from 0 to M, j = 0, 1, 2, ..., M, and Γ() represents the gamma function; m j This indicates that the characteristic function sin(m) is satisfied. j ·L z The eigenvalues ​​when ) = 0, This represents the fitting coefficient of the temperature fluctuation function at the measuring point in the k-th measuring point route;

[0085] Fit coefficients The temperature-time relationship obtained from the measurement points is fitted using the temperature fluctuation function of the measurement points.

[0086] Satisfying the characteristic function sin(m) j ·L z The eigenvalue m when ) = 0 j It was obtained by processing in the following way:

[0087]

[0088] Among them, L Z This represents the axial distance from the origin to the last measuring point (i.e., the measuring point closest to the output end of the circular channel) in the measuring point route.

[0089] Step S4.3: Process the data using a data analysis processor to obtain the function of the axial temperature distribution on the inner wall of the circular channel as a function of time:

[0090]

[0091] Among them, T w (z,t) represents the temperature at position z on the inner wall of the circular channel at time t. This represents the first recursive coefficient in the k-th measurement point route. The first recursive coefficient is obtained by processing it according to the following formula:

[0092]

[0093]

[0094] a=λ / ρc

[0095] Where a is the thermal diffusivity of the circular channel material, λ is the thermal conductivity of the circular channel material, ρ is the density of the circular channel material, c is the specific heat capacity of the circular channel material, int() represents the floor function, and F n This represents the temperature distribution coefficient, where the subscript n ranges from 0 to int[2N-i], n = 0, 1, 2, ..., int[2N-i]. The fitting coefficient of the temperature fluctuation function measured along the k-th measuring point route Correspondingly;

[0096] Step S4.4: Process the data using a data analysis processor to obtain the function showing the change of the axial distribution of heat flux density on the inner wall of the circular channel over time:

[0097]

[0098] Where λ represents the thermal conductivity of the circular channel material, q w (z,t) represents the heat flux density at position z on the inner wall of the circular channel at time t. This represents the second recursive coefficient in the k-th measurement point route. The second recursive coefficient is obtained by the following formula:

[0099]

[0100]

[0101] Among them, R n Indicates the heat flux density distribution coefficient;

[0102] Step S4.5: The axial distribution of the heat transfer coefficient on the inner wall of the circular channel as a function of time is obtained by processing the following formula:

[0103]

[0104] Among them, h w(z,t) represents the heat transfer coefficient at position z on the inner wall of the circular channel at time t, where T l This represents the temperature of the internal working fluid at time t.

[0105] Step 5 specifically involves:

[0106] The dry / wet state of the inner wall of a circular channel can be determined by the heat transfer coefficient of the inner wall surface.

[0107] If the heat transfer coefficient of the inner wall of the circular channel is lower than the preset heat transfer coefficient threshold, the inner wall of the circular channel is considered to be in a dry state.

[0108] Otherwise, the inner wall of the circular channel is considered to be in a moist state.

[0109] Temperature distribution coefficient F n The following formula is used to obtain:

[0110]

[0111]

[0112]

[0113] Where l represents 0 to n, l = 0, 1, 2, ..., n, D l E represents the first coefficient. n-l R represents the third recursive coefficient. k r represents the radial distance between the k-th measuring point route and the inner wall of the circular channel. in Let p represent the inner diameter of the circular channel, p represent the distance from l to positive infinity, p = l, l+1, l+2..., s represent the distance from 0 to p, s = 0, 1, 2..., p, g represent the distance from 1 to nl-1, g = 1, 2, 3..., nl-1, and u represent the distance from 1 to ps, u = 1, 2, 3..., ps;

[0114] Heat flux density distribution coefficient R n The following formula is used to obtain:

[0115]

[0116]

[0117] Among them, H l Let v represent the second coefficient, v = 0, 1, 2, ..., p-1, and w represent the second coefficient, w = 0, 1, 2, ..., pv-1.

[0118] The outer metal film covering the circular channel should be of uniform texture, possessing good electrical and thermal conductivity to generate a good thermal effect. Under the action of an applied direct current, the circular channel can be heated uniformly. In this specific implementation, a type K thermocouple is used, and a piezoelectric sensor is selected as the pressure sensor 6.

[0119] The more uneven the axial temperature distribution in a circular channel, the larger the required value of M. The maximum spatial resolution of the fitted temperature distribution function is half the interval between adjacent measuring points along the axial direction of the circular channel. When the surface temperature distribution changes drastically in the z-direction, the interval between measuring points along the axial direction must be less than twice the required spatial resolution. The value of M should not be less than the number of axial measuring points at the same depth. A value of N of 4 or 5 is sufficient to smooth the temperature change curve over time, thereby reducing the influence of noise. A higher value of N will significantly improve the approximation of temperature changes by the fitted function.

[0120] To achieve a better response time, the measuring points on the first measuring route need to be as close as possible to the inner wall of the circular pipe channel. For capturing the dynamics of wall dryness and wetness, based on the constructed distribution function of temperature, heat flux density, and heat transfer coefficient, when the predicted heat transfer coefficient of the inner wall decreases sharply, it can be determined that local dryness has occurred at that point; if the heat transfer coefficient of the inner wall, based on the constructed distribution function of temperature, heat flux density, and heat transfer coefficient, remains within a stable range with minimal fluctuations, we consider that point on the wall to be in a wet state. This achieves the goal of capturing the dynamics of wall dryness and wetness based on the pulsating changes in the inner wall heat transfer coefficient.

[0121] To facilitate understanding of the present invention and to verify its feasibility, the present invention provides the following simulation examples:

[0122] like Figure 3 The diagram shows a circular channel with an inner diameter of 5 mm and an outer diameter of 15 mm, made of iron (density ρ = 7800 kg / m³). 3 Specific heat capacity c = 483 J / (kg·K), thermal conductivity λ = 50.4 W / (m·K), initial temperature of the circular channel is 200℃, and internal working fluid temperature T l =30℃, 8 monitoring points are arranged at equal intervals (2mm spacing) at distances of 1mm and 3mm from the inner wall surface. The heat transfer coefficient of the inner wall surface is changed to monitor the temperature change of the measuring points. Based on the temperature data of the monitoring points, axial temperature change fitting functions on the first and second measuring point routes are constructed, denoted as f1(t,z) and f2(t,z) respectively.

[0123] Simulation Example 1

[0124] Given operating conditions: The wet-dry interface moves uniformly to the left at a speed of u = 50 mm / s. The left side of the interface is the wetted zone, and the right side is the dry zone. The heat transfer coefficient of the dry zone is given as h = 0.1 kW / (m²).2 ·s), heat transfer coefficient in the wetted zone h=2kW / (m 2 •s). The movement process of the dried-up area is simulated using simulation software. Based on the temperature data of the monitoring points, the heat transfer coefficient of the inner wall surface is predicted using the method proposed in this invention. The feasibility and accuracy of the invention are judged by comparing it with the set operating conditions.

[0125] After simulation and data processing, the data results are as follows: Figure 4 a and Figure 4 As shown in Figure b, through processing the simulation results and simulating the derived temperature data, it is clearly observed that the predicted surface heat transfer coefficient is basically consistent with the trend of the given operating conditions. As time changes, the dried-up area gradually moves to the left along the axial direction (origin of the coordinate system), and the corresponding surface heat transfer coefficient also decreases. This effectively verifies the invention's prediction of the inner wall heat transfer coefficient, demonstrating good feasibility and accuracy.

[0126] Simulation Example 2

[0127] Given operating conditions: In a given circular channel, with the following inner wall boundary conditions: at 0 ≤ t < 0.1 s, the inner wall surface is wet, and the heat transfer coefficient at this time is h = 2 kW / (m²). 2 •s); When 0.1≤t<0.11s, the area at z=6mm dries up, the dried-up zone is a circle with a radius of 1mm, the drying time is 0.01s, and the heat transfer coefficient at drying time is h=0.1kW / (m²). 2 ·s), other areas are moist; the inner wall is moist when 0.11≤t<0.2s; when 0.2≤t<0.22s, the area at z=8mm dries out, the dried area is a circle with a radius of 1mm, and the drying time is 0.02s, while other areas are moist; when t≥0.22s, the inner wall is moist, and the heat transfer coefficient of the entire area is h=2kW / (m²). 2 Based on the temperature changes at each monitoring point, the method proposed in this invention is used to calculate the time-varying function of the heat transfer coefficient distribution on the inner wall of the circular channel. The accuracy of this method is verified by comparing it with the set operating conditions.

[0128] After simulation and calculation, data on the temperature change at the monitoring point over time were obtained. Then, the method proposed in this invention was used to predict the heat transfer coefficient of the inner wall surface. The prediction results are as follows: Figure 5 As shown. Figure 5 'a' is based on the axial temperature distribution variation functions f1(z,t) and f2(z,t) obtained by fitting the temperature at the monitoring points along the first and second measuring point routes. Figure 5 b is the calculated axial temperature distribution variation function of the inner wall surface. Figure 5Figure 'c' is a schematic diagram showing the change of the heat transfer coefficient at the set drying location over time. It can be seen that this method can accurately predict the axial location and drying time of the inner wall surface, further verifying the feasibility and accuracy of the invention.

Claims

1. A method for determining the high-frequency wet and dry dynamic characteristics of the inner wall of a circular channel, characterized in that, The high-frequency dry and wet dynamic characteristic measuring device used in the method for the inner wall of the circular channel includes a working fluid storage tank (1), a temperature and pressure control system (2), a dry and wet dynamic capture system (3), a condenser (4), a valve (5), a pressure sensor (6), a temperature sensor (7), and a flow sensor (8). The working fluid storage tank (1) stores liquid working fluid. The output and input ends of the working fluid storage tank (1) are connected to the input end of the temperature and pressure control system (2) and the output end of the condenser (4) respectively through pipelines. The working fluid storage tank (1) supplies power to the temperature and pressure control system (2) and the condenser (4) respectively. Valves (5) are installed on the pipes. The output end of the temperature and pressure control system (2) is connected to the input end of the wet and dry dynamic capture system (3) through the pipe. Valves (5), pressure sensors (6), temperature sensors (7) and flow sensors (8) are installed in sequence on the pipe from the temperature and pressure control system (2) to the wet and dry dynamic capture system (3). The output end of the wet and dry dynamic capture system (3) is connected to the input end of the condenser (4) through the pipe. Pressure sensors (6) and temperature sensors (7) are installed in sequence on the pipe from the wet and dry dynamic capture system (3) to the condenser (4). The aforementioned wet and dry dynamic capture system (3) includes a temperature acquisition module, a channel heating module, and a data analysis module, both of which are connected to the temperature acquisition module; The temperature acquisition module includes a circular channel, a thermocouple array, and a temperature acquisition device. The circular channel is an annular pipe with openings at both ends. The input and output ends of the circular channel are connected to the temperature and pressure control system (2) and the condenser (4) respectively through the pipes. A thermocouple array is embedded in the side wall of the circular channel. Each thermocouple in the thermocouple array is electrically connected to the data analysis module through the temperature acquisition device. The channel heating module includes a metal film and a power supply. The metal film is sleeved on the outer side wall of the circular channel. The metal film and the power supply are electrically connected. The power supply is used to heat the circular channel. The data analysis module includes a signal amplifier, a signal converter, and a data analysis processor. The input terminal of the temperature acquisition device is connected to a thermocouple, the output terminal of the temperature acquisition device is connected to the input terminal of the signal amplifier, and the output terminal of the signal amplifier is connected to the signal converter and the data analysis processor. The thermocouple array is mainly formed by two thermocouple lines arranged radially at intervals along a circular channel. Each thermocouple line is set along the axial direction of the circular channel. Each thermocouple line is composed of thermocouples arranged sequentially along the same straight line. The number and arrangement of thermocouples in the two thermocouple lines are the same and aligned. Includes the following steps: Step S1: Cover the circular channel to be tested with a thin metal film; Step S2: Arrange several measuring points in the side wall of the circular channel, and embed a thermocouple at each measuring point location; the measuring points form two measuring point routes arranged along the axial direction of the circular channel, each measuring point route is formed by sequentially connecting measuring points along the same straight line, the two measuring point routes are arranged radially at intervals along the circular channel, and the number and arrangement of measuring points in the two measuring point routes are the same and aligned. Step S3: Start the device and use the temperature acquisition device to collect the temperature information of the thermocouple; Step S4: The temperature acquisition device transmits the acquired temperature information to the data analysis processor, which processes the data to obtain the heat transfer coefficient of the inner wall of the circular channel. Step S5: Determine the dry / wet state of the inner wall of the circular channel by the heat transfer coefficient of the inner wall.

2. The method for determining the high-frequency wet and dry dynamic characteristics of the inner wall of a circular channel according to claim 1, characterized in that: The specific steps for obtaining the heat transfer coefficient of the inner wall of the circular channel in step S4 are as follows: Step S4.1: Take the measurement point route near the inner wall of the circular channel as the first measurement point route, and the measurement point route near the outer wall of the circular channel as the second measurement point route. Take the measurement point near the input end of the circular channel in the first measurement point route as the origin, and the axis of the circular channel as the Z-axis to establish a coordinate system. Step S4.2: Constructing the measuring point temperature fluctuation function by using the data analysis processor, the measuring point temperature fluctuation function is obtained by processing in the following manner: in, This represents the temperature at position z at time t in the k-th measurement route. The subscript k indicates the ordinal number of the measurement route, which is 1 or 2. N represents a preset constant, i represents -1 to N, and M represents the characteristic function. The maximum order, j represents 0 to M, Г() represents the gamma function; m j This indicates that the characteristic function is satisfied. eigenvalues ​​at time, This represents the fitting coefficient of the temperature fluctuation function at the measuring point in the k-th measuring point route; Step S4.3: Process the data using a data analysis processor to obtain the function of the axial temperature distribution on the inner wall of the circular channel as a function of time: wherein Tz(t) represents the temperature at the z position on the inner side wall surface of the circular passage at the time t, Tz(t) represents the temperature at the z position on the inner side wall surface of the circular passage at the time t, Tk(t) represents the first recursive coefficient in the kth measuring point route, and the first recursive coefficient is obtained by processing according to the following formula: a = λ / ρc where a is the thermal diffusivity of the circular channel material, λ is the thermal conductivity of the circular channel material, p is the density of the circular channel material, c is the specific heat capacity of the circular channel material, int() represents the integer function, F n represents a temperature distribution coefficient, and subscript n represents from 0 to int[2N-i]; Step S4.4: Process the data using a data analysis processor to obtain the function showing the change of the axial distribution of heat flux density on the inner wall of the circular channel over time: where λ represents the thermal conductivity of the circular channel material, represents the heat flux density at the z position on the inner wall surface of the circular channel at time t, represents the second recursive coefficient in the kth measurement point route, and the second recursive coefficient is obtained by processing according to the following formula: wherein R n represents the heat flux density distribution coefficient; Step S4.5: The axial distribution of the heat transfer coefficient on the inner wall of the circular channel as a function of time is obtained by processing the following formula: wherein, represents the heat transfer coefficient at the z position on the inner side wall surface of the circular passage at time t, T l represents the temperature of the internal working medium at time t.

3. The method of claim 1, wherein the method is a method of measuring high frequency dry and wet dynamic characteristics of an inner wall of a circular passage. Step 5 specifically includes: The dry / wet state of the inner wall of a circular channel can be determined by the heat transfer coefficient of the inner wall surface. If the heat transfer coefficient of the inner wall of the circular channel is lower than the preset heat transfer coefficient threshold, the inner wall of the circular channel is considered to be in a dry state. Otherwise, the inner wall of the circular channel is considered to be in a moist state.

4. The method of claim 2, wherein the method is a method of measuring high frequency dry and wet dynamic characteristics of an inner wall of a circular passage, characterized by: The temperature distribution coefficient F n The treatment was performed according to the following formula: Where l represents 0 to n, D l E represents the first coefficient. n-l R represents the third recursive coefficient. k r represents the radial distance between the k-th measuring point route and the inner wall of the circular channel. in The inner diameter of the circular channel is represented by p, which represents l to positive infinity, s represents 0 to p, g represents 1 to nl-1, and u represents 1 to ps.

5. The method of claim 2, wherein the method is a method of measuring high frequency dry and wet dynamic characteristics of an inner wall of a circular passage, characterized by: The heat flow density distribution coefficient R n The treatment was performed according to the following formula: where H l denotes a second coefficient, v denotes 0 to p-1, and w denotes 1 to p-v-1.

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