Method and device for measuring flow of hydrogen-containing mixed gas based on thermal conductivity

Abstract

The invention discloses a flow measurement method and device for hydrogen-containing mixed gas based on thermal conductivity, and belongs to a flow measurement technology for hydrogen-containing mixed gas. According to the method, firstly, zero gas is adopted for calibration and reference so as to obtain hydrogen mass flowmeter data under the condition that hydrogen is not contained, and hydrogen mass flowmeter data under different flows are obtained by adjusting a float flowmeter; then acquiring data under different hydrogen contents and different flows by adopting hydrogen-containing mixed gases with different volumes, a hydrogen float flowmeter and a hydrogen mass flowmeter, synchronously recording gas path temperature and pressure in a measurement process, and fitting to obtain a slope and concentration relationship through volume-mass flow relationship curves of gases with different concentrations; and finally, deducing a volume flow calculation formula of the mixed hydrogen by utilizing the compensated parameters such as the density and the heat conductivity of the mixed gas and combining hydrogen density and mass flow data in a standard state. According to the invention, a reliable calibration basis is provided for the flow measurement of the hydrogen mixed gas.

Description

Technical Field

[0001] The present invention belongs to the technical field of flow measurement, and in particular relates to a method and device for measuring the flow of a hydrogen-containing mixed gas based on thermal conductivity. Background Art

[0002] In industrial manufacturing and chemical production, hydrogen is often used as a raw material or byproduct, requiring real-time monitoring for leaks. In the metalworking industry, hydrogen is used in reduction or heat treatment processes. In the energy sector, leak detection in hydrogen storage tanks and fuel cells ensures safe vehicle operation. Therefore, detecting hydrogen concentration is particularly important.

[0003] The thermal conductivity principle is commonly used to measure hydrogen. Due to the varying thermal conductivities of various gases, different gases remove varying amounts of heat as they pass through the sensor, indirectly determining the measured component's content. When using the thermal conductivity principle to measure trace hydrogen concentrations, volume flow is a key factor.

[0004] Currently, most sensors used to measure gas volume flow are ultrasonic gas flow sensors, electromagnetic gas flow sensors, Karman vortex flow sensors, Hall gas flow sensors, etc. Most of these sensors are expensive or are limited by the site of use and installation conditions.

[0005] Hydrogen, unlike other gases, has a much higher thermal conductivity. Therefore, the thermal conductivity of a mixture of hydrogen and other gases is determined by the percentage of hydrogen in the mixture. Therefore, the present invention uses a thermal mass flow sensor, along with temperature and pressure sensors to compensate for the measured flow. Summary of the Invention

[0006] Purpose of the invention: The present invention aims to provide a flow measurement method for hydrogen-containing mixed gases based on thermal conductivity, providing a solution for low-cost, high-precision hydrogen flow detection. At the same time, the present invention also provides a flow measurement device for hydrogen-containing mixed gases based on thermal conductivity to realize the detection application of the method.

[0007] In order to achieve the above-mentioned purpose of the invention, the technical solutions provided by the present invention are as follows:

[0008] A method for measuring the flow rate of a hydrogen-containing mixed gas based on thermal conductivity, comprising the following steps:

[0009] S1. Introduce zero gas and obtain hydrogen mass flowmeter data in the absence of hydrogen through the zero gas float flowmeter and the hydrogen mass flowmeter, and record the hydrogen mass flowmeter data at different flow rates by adjusting the float flowmeter;

[0010] The float flowmeter is used to control and adjust the volume flow of zero gas, which refers to pure gas or mixed gas with a thermal conductivity lower than that of hydrogen;

[0011] S2. introducing hydrogen-containing mixed gases with different volume fractions, and using corresponding hydrogen float flowmeters and hydrogen mass flowmeters to obtain data of different hydrogen contents at different flow rates;

[0012] S3, measuring the temperature and pressure values ​​corresponding to the hydrogen mass flow meter data of step S1 and step S2 by a temperature sensor and a pressure sensor;

[0013] S4. Draw a dot graph of the relationship between the volume flow rate and mass flow rate of gases of various concentrations, fit the curve, list the slope and concentration data and draw a dot graph;

[0014] S5. Density compensation is performed on the hydrogen-containing mixed gas in step S2. The density compensation formula is:

[0015]

[0016] Among them, ρ x Indicates the density of hydrogen-containing mixed gas, P x Indicates the current pressure in the pipeline, P0 indicates the atmospheric pressure under standard conditions, T0 indicates the environment and temperature under standard conditions, T X Indicates the current temperature in the pipeline, ρ0 indicates the density of the hydrogen-containing mixed gas under standard conditions;

[0017] S6. Based on the compensated mixed gas density, mixed gas thermal conductivity, hydrogen density under standard conditions, and mass flow rate, the volume flow rate calculation formula is obtained:

[0018]

[0019] Among them, Q m represents the measured volume flow rate of the hydrogen-containing mixed gas, K is the slope of the fitting curve obtained in step S4, and λ x Indicates the thermal conductivity of the hydrogen-containing gas mixture, Q V Indicates the calculated volume flow rate of the hydrogen-containing mixed gas.

[0020] In the above method, step S4 includes data preprocessing to remove abnormal points caused by transient fluctuations of the sensor. Then, for curve fitting, the slope k and intercept b are solved through matrix operations:

[0021]

[0022] Where x and y represent the volume flow rate and mass flow rate in the relationship dot graph, respectively, and n represents the number of valid data groups. Respectively represent the average value of volume flow rate and mass flow rate in the valid data.

[0023] Furthermore, the zero gas includes a single gas or any mixed gas including nitrogen, neon, argon, oxygen, and air, and the thermal conductivity of the mixed gas is lower than 1 / 20 of that of hydrogen.

[0024] Furthermore, in the method, the flow rate is controlled by the float flowmeter by adjusting the flow rate at equal intervals, thereby simplifying the measurement process and reducing the complexity of data processing.

[0025] Furthermore, the hydrogen content in the hydrogen-containing mixed gas is adjusted from 0 to 100%, and hydrogen mass flowmeter data at different flow rates under corresponding contents are obtained.

[0026] Furthermore, the zero gas is pure nitrogen, and the hydrogen-containing mixed gas is a mixed gas of nitrogen and hydrogen.

[0027] The present invention also provides a flow measurement device for a hydrogen-containing mixed gas, which is used to implement the flow measurement method for the hydrogen-containing mixed gas.

[0028] Furthermore, the measuring device comprises:

[0029] memory for storing computer programs;

[0030] The processor is used to execute the computer program to implement the flow measurement method of the hydrogen-containing mixed gas, including inputting the data obtained in steps S1-S3 and then executing the calculations in steps S4-S6.

[0031] Furthermore, the measuring device further comprises a float flowmeter, a hydrogen mass flowmeter, a temperature sensor and a pressure sensor, wherein the float flowmeter, the hydrogen mass flowmeter, the temperature sensor and the pressure sensor are all located on the pipeline for measuring the flow of the hydrogen-containing mixed gas;

[0032] The float flowmeter is used to adjust the flow of zero gas or hydrogen, including a nitrogen float flowmeter or a hydrogen float flowmeter, and also includes a hydrogen float flowmeter configured according to the hydrogen content in different hydrogen-containing mixed gases to control the corresponding proportion.

[0033] Based on the implementation of the above scheme, the present invention also provides a computer-readable storage medium, comprising at least one processor and at least one memory containing computer program code, wherein the memory and the computer program code are configured to execute step S4 in the flow measurement method of the hydrogen-containing mixed gas, including calculations for executing steps S5 and S6.

[0034] Beneficial effects: The present invention provides a method for accurately measuring the volume flow rate of mixed hydrogen, which can ensure that the volume of hydrogen flowing through the thermal conductivity sensor remains constant when the concentration changes, thereby more accurately measuring its concentration, which is more conducive to industrial production or laboratory experiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the detection pipeline in the detection device;

[0036] Figure 2 is a measurement flow chart of the method (using nitrogen as zero gas for measurement without hydrogen);

[0037] Figure 3 It is a dot diagram showing the relationship between the volume flow rate and mass flow rate of the mixed hydrogen in the embodiment. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the embodiments and the accompanying drawings.

[0039] Example 1: First, prepare a hydrogen-containing mixed gas with high-purity nitrogen and hydrogen contents of 10%, 25%, 50%, 60% and 80%, respectively. The other gas in the hydrogen-containing mixed gas is nitrogen. A float flowmeter and a hydrogen mass flowmeter for preparing high-purity hydrogen are also included. High-purity nitrogen and 10%, 25%, 50%, 60%, 80% and 99.99% hydrogen are used, and the flow rate is adjusted in steps of 50mL / min within the range of 50-450mL / min, and the mass flowmeter reading is recorded. During the measurement, the gas path temperature and pressure are recorded synchronously, and the density of the mixed gas is calculated using a compensation formula. Based on the experimental data, the volume-mass flow relationship curve of each concentration gas is plotted, and the slope and concentration relationship is obtained by fitting. Finally, the compensated mixed gas density, thermal conductivity and other parameters are used, combined with the hydrogen density and mass flow data under standard conditions, to derive the volume flow calculation formula for the mixed hydrogen. This method provides a reliable calibration basis for the flow measurement of hydrogen mixed gas. Based on the experimental data, the relationship curve between volume flow and mass flow is fitted, and finally a calculation model for the volume flow of mixed hydrogen is established, providing a solution for low-cost and high-precision hydrogen flow detection.

[0040] The implementation steps of the method of the present invention are as follows:

[0041] Step 1: Introduce high-purity nitrogen gas through the nitrogen float flowmeter and hydrogen mass flowmeter. Adjust the float flowmeter knob so that the float indicates 50ml / min and record the hydrogen mass flowmeter reading.

[0042] Step 2: Adjust the float flowmeter knob so that the float indicates 100 ml / min, record the hydrogen float flowmeter reading, and then adjust the knob every 50 ml / min and record the reading until the mass flowmeter reading is recorded when the float flowmeter indicates 450 ml / min.

[0043] Step 3: Replace the 10% hydrogen and introduce it into the 10% hydrogen float flowmeter and hydrogen mass flowmeter. Make the float indicate 50ml / min and record the hydrogen mass flowmeter reading. Repeat step 2.

[0044] Step 4: Measure the temperature and pressure in the gas line and record the readings. Substitute these readings into the compensation formula and calculate the density of the mixed gas.

[0045] Step 5: Replace 25%, 50%, 60%, 80% or high purity hydrogen and repeat steps 2, 3 and 4.

[0046] Step 6: Draw a dot graph of the relationship between volume flow rate and mass flow rate of gases of various concentrations, fit the curve, list the slope and concentration data and draw a dot graph.

[0047] Step 7: Based on the compensated mixed gas density, mixed gas thermal conductivity, hydrogen density under standard conditions, and mass flow rate, substitute them into the volume flow calculation formula to obtain the volume flow rate of the mixed hydrogen.

[0048] Example 2: Combination Figure 1-3 As shown, the device and method provided by the present invention include the following processes in hydrogen-containing mixed gas measurement:

[0049] (1) High-purity nitrogen flow measurement

[0050] Initial setting: high-purity nitrogen (99.999%) is introduced and passed through the nitrogen float flowmeter and the hydrogen mass flowmeter in sequence.

[0051] Flow adjustment: Adjust the float flowmeter knob to stabilize the float at 50mL / min and record the reading of the hydrogen mass flowmeter.

[0052] Adjust the float flowmeter to 100, 150, 200, 250, 300, 350, 400, and 450 mL / min in sequence, and record the readings of the hydrogen mass flowmeter respectively.

[0053] (2) 10% hydrogen-nitrogen mixed gas flow measurement

[0054] Gas switching: Turn off high-purity nitrogen and switch to a mixed gas source of 10% hydrogen + 90% nitrogen.

[0055] Flow adjustment: Adjust the float flowmeter to 50mL / min and record the hydrogen mass flowmeter reading.

[0056] Repeat the flow adjustment steps of high-purity nitrogen (50-450 mL / min, 50 mL / min intervals), and record the mass flow data corresponding to each flow point.

[0057] (3) Temperature and pressure data collection and density calculation

[0058] Environmental parameter measurement: Use a temperature sensor to measure the gas path temperature (unit: K), and use a pressure sensor to measure the gas path pressure (unit: kPa).

[0059] Density calculation: Substitute the temperature and pressure data into the compensation formula to calculate the density of the mixed gas ρ x :

[0060]

[0061] (4) Flow calibration of hydrogen mixtures with different concentrations

[0062] Replace the gas source: replace with 25%, 50%, 60%, 80% hydrogen-nitrogen mixed gas and high-purity hydrogen (99.999%) in sequence, repeat steps 2 to 3, and record the flow rate, temperature, pressure and mass flow rate data at each concentration.

[0063] (5) Data processing and analysis

[0064] Draw the flow relationship curve: Use the float flowmeter reading (volume flow, mL / min) as the horizontal axis and the hydrogen mass flowmeter reading (mass flow, sccm) as the vertical axis to draw a scatter plot of the gas concentrations, and use the least squares method to fit the curve.

[0065] Taking 80% hydrogen mixed gas as an example, nine sets of flow rate data (50-450 mL / min, step size 50 mL / min) were collected and the least squares method was used to fit a linear curve. The specific steps are as follows:

[0066] Data preprocessing: Eliminate abnormal points caused by transient fluctuations of the sensor (such as data showing a sudden drop of 5% in mass flow rate at 300 mL / min);

[0067] Parameter calculation: Solve the slope k and intercept b through matrix operations:

[0068]

[0069] Where n = 9 is the number of valid data sets, x is the volume flow rate, and y is the mass flow rate;

[0070] Verification curve: The fitting results are k=1.85, b=-2.7, and the residual standard deviation σ=1.2 sccm, which meets the accuracy requirement (σ<1.5 sccm).

[0071] Slope-concentration relationship analysis: Summarize the slopes corresponding to different hydrogen concentrations (10%, 25%, 50%, 60%, 80%, 100%), draw a relationship graph between the slope and hydrogen concentration, and analyze its changing trend.

[0072] (6) Calculation of mixed hydrogen volume flow rate

[0073] Parameter input: Compensated mixed gas density (ρ x ).

[0074] Calculate the thermal conductivity of the mixed gas (λ x ), λ x =Σλ i n i ;

[0075] The density of hydrogen under standard conditions (ρ H2 =0.0899 g / L).

[0076] Q m represents the measured mass flow rate, and the mixed hydrogen volume flow rate is calculated as:

[0077]

[0078] Finally, combined with the requirements of actual measurement technology, the present invention performs the following uncertainty analysis:

[0079] 1) Mass flow meter error: According to the manufacturer's standard, full scale (500sccm) ±1%, that is, u1 = 5sccm;

[0080] 2) Fitting residual: The standard deviation of the fitting curve residual at 80% hydrogen concentration is σ = 1.2 sccm,

[0081] 3) Temperature and pressure compensation error: The temperature sensor accuracy is ±0.5°C, resulting in a density calculation deviation of ±0.2%, u3 = 0.002Qm;

[0082] 4) Repeatability error: The standard deviation of three repeated experiments is u4 = 0.8 sccm.

[0083] Combined uncertainty At 300 sccm, uc = 5.1 sccm (expanded uncertainty U = 2uc = 10.2 sccm, confidence level 95%).

[0084] According to the above uncertainty analysis, the relative expanded uncertainty of the present invention in the range of 50-450 mL / min is ±1.7% (k=2), which is significantly better than ±3.5% when not compensated.

[0085] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for measuring the flow rate of a hydrogen-containing mixed gas based on thermal conductivity, characterized in that the steps include: S1. Introduce zero gas and obtain hydrogen mass flowmeter data in the absence of hydrogen through the zero gas float flowmeter and the hydrogen mass flowmeter, and record the hydrogen mass flowmeter data at different flow rates by adjusting the float flowmeter; The float flowmeter is used to control and adjust the volume flow of zero gas, which refers to pure gas or mixed gas with a thermal conductivity lower than that of hydrogen; S2. introducing hydrogen-containing mixed gases with different volume fractions, and using corresponding float flowmeters and hydrogen mass flowmeters to obtain data at different hydrogen contents and flow rates; S3, measuring the temperature and pressure values ​​corresponding to the hydrogen mass flow meter data of step S1 and step S2 by a temperature sensor and a pressure sensor; S4. Draw a dot graph of the relationship between the volume flow rate and mass flow rate of gases of various concentrations, fit the curve, list the slope and concentration data and draw a dot graph; S5. Density compensation is performed on the hydrogen-containing mixed gas in step S2. The density compensation formula is: Among them, ρ x Indicates the density of hydrogen-containing mixed gas, P x Indicates the current pressure in the pipeline, P0 indicates the atmospheric pressure under standard conditions, T0 indicates the environment and temperature under standard conditions, T X Indicates the current temperature in the pipeline, ρ0 indicates the density of the hydrogen-containing mixed gas under standard conditions; S6. According to the compensated mixed gas density, mixed gas thermal conductivity, and mass flow rate, the volume flow rate calculation formula is substituted into the mixed hydrogen volume flow rate calculation formula: Among them, Q m represents the mass flow rate of the measured hydrogen-containing mixed gas, K is the slope of the fitting curve obtained in step S4, and λ x Indicates the thermal conductivity of the hydrogen-containing gas mixture, Q V Indicates the calculated volume flow rate of the hydrogen-containing mixed gas.

2. The method for measuring the flow rate of hydrogen-containing mixed gas according to claim 1, characterized in that: Step S4 includes data preprocessing to remove abnormal points caused by transient fluctuations of the sensor. Then, for curve fitting, the slope k and intercept b are solved through matrix operations: Where x and y represent the volume flow rate and mass flow rate in the relationship dot graph, respectively, and n represents the number of valid data groups. Respectively represent the average value of volume flow rate and mass flow rate in the valid data.

3. The method for measuring the flow rate of hydrogen-containing mixed gas according to claim 1, wherein: The zero gas includes a single gas or any mixed gas including nitrogen, neon, argon, oxygen, and air, and the thermal conductivity of the mixed gas is less than 1 / 20 of that of hydrogen.

4. The method for measuring the flow rate of hydrogen-containing mixed gas according to claim 1, wherein: In this method, the flow rate is controlled by the float flowmeter, including adjusting the flow rate at equal intervals.

5. The method for measuring the flow rate of hydrogen-containing mixed gas according to claim 1, characterized in that: The hydrogen content in the hydrogen-containing mixed gas is adjusted from 0 to 100%, and hydrogen mass flowmeter data at different flow rates under corresponding contents are obtained.

6. The method for measuring the flow rate of hydrogen-containing mixed gas according to claim 1, characterized in that: The zero gas is pure nitrogen, and the hydrogen-containing mixed gas is a mixed gas of nitrogen and hydrogen.

7. A flow measurement device for a hydrogen-containing mixed gas, characterized in that: The device is used to implement the flow measurement method of the hydrogen-containing mixed gas as described in any one of claims 1 to 6.

8. The flow rate measuring device for hydrogen-containing mixed gas according to claim 7, characterized in that: The measuring device comprises: memory for storing computer programs; A processor is used to execute the computer program to implement the flow measurement method of the hydrogen-containing mixed gas as claimed in claim 1, comprising inputting the data obtained in steps S1-S3 and then executing the calculations in steps S4-S6.

9. The flow rate measuring device for hydrogen-containing mixed gas according to claim 7 or 8, characterized in that: The measuring device also includes a float flowmeter, a hydrogen mass flowmeter, a temperature sensor and a pressure sensor, wherein the float flowmeter, the hydrogen mass flowmeter, the temperature sensor and the pressure sensor are all located on the pipeline for measuring the flow of the hydrogen-containing mixed gas; The float flowmeter is used to adjust the flow of zero gas or hydrogen, including a nitrogen float flowmeter or a hydrogen float flowmeter, and also includes a hydrogen float flowmeter configured according to the hydrogen content in different hydrogen-containing mixed gases to control the corresponding proportion.

10. A computer-readable storage medium, characterized in that The method comprises at least one processor and at least one memory including computer program code, wherein the memory and the computer program code are configured to execute step S4 in the method for measuring the flow rate of hydrogen-containing mixed gas, including calculations for executing steps S5 and S6.

Images