Throttling and heating coupled steam humidity measurement system and method

Abstract

The present invention discloses a throttling and heating coupled steam humidity measurement system and method, which is provided by setting a first steam outlet pipe connected to a steam main pipe and a second steam outlet pipe connected to the end thereof by a throttling member; and connecting a first pressure measuring device to the air inlet end of the first steam outlet pipe, and arranging a heater therein; and connecting a second pressure measuring device, a temperature measuring device and a mass flow meter in the second steam outlet pipe, and arranging an exhaust port at the end thereof. The method realizes the calculation of the humidity of the flowing saturated steam by obtaining the saturated gas phase enthalpy and the saturated liquid phase enthalpy of the saturated steam flowing into the first steam outlet pipe, the voltage and current of the heater, and the mass flow rate and enthalpy value of the superheated steam flowing into the second steam outlet pipe. The method realizes the accurate measurement of the humidity of the flowing saturated steam with large flow and high humidity at low energy consumption. At the same time, it also has the characteristics of high tolerance to impurities, low cost, no need for visualization equipment, and wide range of humidity and flow measurement.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear power measurement, and in particular to a throttling and heating coupled steam humidity measurement system and method. Background Art

[0002] Steam humidity is an important parameter in the field of two-phase flow, which directly affects the accurate measurement of saturated steam flow. The variability of the flow pattern of vapor-liquid two-phase flow, the complexity of mass, energy and momentum exchange between the two phases, and the indirect measurement characteristics of humidity have led to the fact that there is still no better solution for measuring the humidity of saturated steam. At present, the steam humidity measurement methods at home and abroad are mainly divided into two categories: thermodynamic method and non-thermodynamic method.

[0003] Non-thermodynamic method

[0004] Non-thermodynamic methods mainly include capture method, electrical method, optical method, etc. The capture method mainly measures the mass of a certain phase in wet steam by absorption method, and then measures the remaining other phase for a second time. By comparing the results of the two measurements, the steam humidity can be calculated; the electrical method uses the huge difference in dielectric constants between different phases of the fluid to achieve humidity measurement; the optical method mainly reflects the gas-liquid two-phase distribution of the two-phase flow cross section through optical imaging method, realizes the measurement of the cross-sectional gas content, and then calculates the humidity according to the relationship between the cross-sectional gas content and humidity.

[0005] Thermodynamics

[0006] Thermodynamic methods mainly include throttling method, heating method, condensation method, etc. The throttling method is to throttle the extracted wet steam sample to a lower pressure, so that the steam is in a superheated state, and the humidity value of the wet steam is calculated based on the unchanged enthalpy value before and after throttling; the heating method is similar to the throttling method in principle, except that heat is added to the wet steam at a constant pressure to achieve superheating; in the condensation method, the extracted steam sample is condensed into a liquid phase in the condenser, and then the mass of the extracted steam sample, the mass of the liquid phase, and the inlet and outlet temperatures of the liquid phase are measured to calculate the enthalpy value of the extracted steam, and then determine the saturated water enthalpy and latent heat of vaporization at a certain pressure point at the extraction sampling location, and finally calculate the steam humidity.

[0007] Both of the above methods have disadvantages to varying degrees. The disadvantage of the capture method is that it is difficult to measure flowing steam; the disadvantage of the electrical method is that the measurement accuracy is easily affected by impurities; the disadvantage of the optical method is that the imaging equipment is expensive and visualization is difficult under high-pressure conditions; the disadvantage of the throttling method is that when the steam humidity is high, the required pressure drop is too large to achieve the superheated state of the steam, and the steam may even be in a negative pressure state; the disadvantage of the heating method is that when the humidity and flow rate of the steam are large, the required heating power is too high; the disadvantage of the condensation method is similar to the capture method, and it is difficult to measure flowing steam.

[0008] In view of the above shortcomings, it is necessary to develop a steam humidity measurement system and method that couples throttling and heating to solve the problems faced by the existing technology of using only thermodynamic methods, such as being unsuitable for testing steam humidity or excessive flow; or when using only non-thermodynamic methods to measure the humidity of the tested saturated steam, it is not suitable for testing the steam containing impurities and the equipment visualization is difficult. Summary of the invention

[0009] The purpose of the present invention is to provide a system for superheating steam by coupling throttling and heating, and then measuring the humidity of throttling steam, and a saturated steam humidity test method corresponding to the system, so as to achieve accurate and instant measurement of the humidity of large flow and high humidity flowing saturated steam at low energy consumption. At the same time, the system and the test method also have the characteristics of high tolerance to impurities, low cost, no need for visualization equipment, and a wide range of humidity and flow measurement.

[0010] To achieve the above object, the present invention provides the following technical solutions:

[0011] A throttling and heating coupled steam humidity measurement system, the system comprising a first steam outlet pipe connected to a steam main pipe, and a second steam outlet pipe connected to the end of the first steam outlet pipe by a throttling member;

[0012] An exhaust port is provided at the end of the second steam outlet pipe;

[0013] The air inlet end of the first steam outlet pipe is connected to a first pressure measuring device, and a heater is provided in the first steam outlet pipe;

[0014] The second steam outlet pipe is connected with a second pressure measuring device, a temperature measuring device and a mass flow meter.

[0015] As a further improvement of the present invention, the first pressure measuring device includes a first pressure transmitter;

[0016] The second pressure measuring device includes a second pressure transmitter;

[0017] The temperature measuring device includes a temperature transmitter;

[0018] The first pressure transmitter, the second pressure transmitter, the temperature transmitter, and the mass flow meter are all connected to a humidity calculation device.

[0019] As a further improvement of the present invention, the outer circumferences of the first steam outlet pipe and the second steam outlet pipe are both provided with thermal insulation cotton.

[0020] As a further improvement of the present invention, an exhaust valve for controlling the connection / disconnection between the second steam outlet pipe and the outside is further provided at the end of the second steam outlet pipe.

[0021] As a further improvement of the present invention, the inner diameter of the first steam outlet pipe is smaller than the inner diameter of the second steam outlet pipe.

[0022] As a further improvement of the present invention, the second pressure transmitter and the temperature transmitter are connected to the same cross section in the second steam outlet pipe.

[0023] As a further improvement of the present invention, the distance between the cross section and the air inlet end of the second steam outlet pipe is 5 to 10 times the inner diameter of the second steam outlet pipe.

[0024] The present invention also provides a method for measuring saturated steam humidity using the aforementioned throttling and heating coupled steam humidity measurement system, the method comprising:

[0025] Obtaining the saturated gas phase enthalpy and the saturated liquid phase enthalpy of the saturated steam flowing from the steam main pipeline into the first steam outlet pipeline, the voltage and current of the heater, the mass flow rate of the superheated steam flowing into the second steam outlet pipeline, and the enthalpy value of the superheated steam;

[0026] The humidity of the saturated steam is calculated according to the saturated gas phase enthalpy and the saturated liquid phase enthalpy of the saturated steam, the voltage and the current of the heater, the mass flow rate of the superheated steam and the enthalpy value of the superheated steam.

[0027] As a further improvement of the present invention, the calculation formula for calculating the saturated steam humidity according to the saturated gas phase enthalpy and saturated liquid phase enthalpy of the saturated steam, the voltage and current of the heater, the mass flow rate of the superheated steam and the enthalpy value of the superheated steam is:

[0028]

[0029] In the formula, is the steam humidity; h″ is the saturated gas phase enthalpy; h′ is the saturated liquid phase enthalpy; U is the heater voltage; I is the heater current; G is the mass flow rate of superheated steam; h2 is the enthalpy value of superheated steam.

[0030] As a further improvement of the present invention, obtaining the saturated gas phase enthalpy and the saturated liquid phase enthalpy of the saturated steam, the mass flow rate of the superheated steam, and the enthalpy value of the superheated steam includes:

[0031] The first pressure measuring device is used to obtain the pressure value P1 of the saturated steam flowing from the steam main pipeline into the air inlet end of the first steam outlet pipeline;

[0032] The pressure P2 of the superheated steam after throttling is obtained by using the second pressure measuring device;

[0033] Use the temperature measuring device to obtain the temperature T2 of the superheated steam after throttling;

[0034] The mass flow rate of superheated steam after throttling is obtained by using a mass flow meter;

[0035] According to the pressure value P1 of the saturated steam, the saturated gas phase enthalpy and the saturated liquid phase enthalpy of the saturated steam are obtained;

[0036] The enthalpy value of the superheated steam is obtained according to the pressure P2 of the superheated steam after throttling and the temperature T2 of the superheated steam after throttling.

[0037] As a further improvement of the present invention, the first pressure measuring device includes a first pressure transmitter;

[0038] The second pressure measuring device includes a second pressure transmitter;

[0039] The temperature measuring device includes a temperature transmitter;

[0040] The first pressure transmitter, the second pressure transmitter, the temperature transmitter and the mass flow meter respectively transmit the acquired pressure, temperature or flow information to the humidity calculation device, and the humidity calculation device completes the calculation of the saturated steam humidity.

[0041] Technical effects and advantages of the present invention:

[0042] The throttling and heating coupled steam humidity measurement system and method of the present invention is provided with a first steam outlet pipe connected to the steam main pipe, a second steam outlet pipe connected to the end of the first steam outlet pipe by a throttling device, an exhaust port is provided at the end of the second steam outlet pipe, a first pressure measuring device is connected to the air inlet end of the first steam outlet pipe, a heater is provided in the first steam outlet pipe, and a second pressure measuring device, a temperature measuring device and a mass flow meter are connected in the second steam outlet pipe. The humidity of the flowing saturated steam is successfully calculated by obtaining the saturated gas phase enthalpy and saturated liquid phase enthalpy of the saturated steam flowing into the first steam outlet pipe, the voltage and current of the heater, the mass flow rate of the superheated steam flowing into the second steam outlet pipe and the enthalpy value of the superheated steam. The measurement method can realize the accurate measurement of the humidity of the flowing saturated steam with large flow and high humidity at low energy consumption. At the same time, it also has the characteristics of high tolerance to impurities, low cost, no need for visualization equipment, and a wide range of humidity and flow measurement.

[0043] The throttling and heating coupled steam humidity measurement system and method of the present invention realizes real-time and convenient online measurement of saturated steam humidity by connecting the first pressure transmitter, the second pressure transmitter, the temperature transmitter and the mass flowmeter for testing the saturated steam pressure before heating and the superheated steam pressure, temperature and flow after throttling to a humidity calculation device. This is of great significance for real-time monitoring of saturated steam flow and has broad application prospects.

[0044] Other features and advantages of the present invention will be described in the following description, and partly become obvious from the description, or be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a structural schematic diagram of the throttling and heating coupled steam humidity measurement system of the present invention;

[0046] Figure 2 A schematic diagram of a flow chart of testing saturated steam humidity by the throttling and heating coupled steam humidity measurement system provided by the present invention.

[0047] Reference numerals

[0048] 1. Steam main pipeline; 2. First steam outlet pipeline; 3. Heater; 4. Throttle; 5. First pressure transmitter; 6. Second pressure transmitter; 7. Temperature transmitter; 8. Humidity calculation device; 9. Second steam outlet pipeline; 10. Insulation cotton; 11. Exhaust valve; 12. Mass flow meter. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] In order to solve the deficiencies of the prior art, the present invention discloses a throttling and heating coupled steam humidity measurement system, please refer to Figure 1As shown, the system includes a first steam outlet pipe 2 connected to the steam main pipe 1, and a second steam outlet pipe 9 connected to the end of the first steam outlet pipe 2 by a throttling member 4; an exhaust port is arranged at the end of the second steam outlet pipe 9; a first pressure measuring device is connected to the air inlet end of the first steam outlet pipe 2, and a heater 3 is arranged in the first steam outlet pipe 2, and the heater 3 is arranged behind the first pressure measuring device; a second pressure measuring device, a temperature measuring device and a mass flow meter 12 are connected in the second steam outlet pipe 9. In this way, when the saturated steam in the steam main pipe 1 flows into the first steam outlet pipe 2, the real-time pressure value P1 will be measured by the first test device arranged at the air inlet end of the first steam outlet pipe 2, and then the saturated steam will be heated by the heater 3 arranged at the rear, and the heater 3 can provide energy for the gasification of a part of the liquid phase in the saturated wet steam, thereby gradually reducing the humidity of the steam, and the flow heating process of the heater 3 is a constant pressure process. Then, the saturated steam with significantly reduced humidity continues to flow through the throttling device 4 to reduce pressure, the saturation temperature is reduced, the water in the steam is overheated and vaporized, the humidity continues to decrease, and finally the steam is transformed from a wet saturated steam state to a single-phase superheated state. In this process, preferably, the inner diameter of the first steam outlet pipe 2 can be set to be smaller than the inner diameter of the second steam outlet pipe 9. This is more conducive to reducing the pressure of the steam flowing through the throttling device 4, so that it is transformed from a wet saturated state to a single-phase superheated state.

[0051] At the same time, the second pressure measuring device, temperature measuring device and mass flow meter 12 arranged in the second steam outlet pipe 9 will measure the pressure value P2, temperature value T2 and mass flow rate G of the superheated steam in the pipe in real time.

[0052] Furthermore, the flow of wet steam in the pipeline during this process satisfies the following equation:

[0053]

[0054] In the formula, is the heat exchange between wet steam and the environment before and after throttling (W), is the enthalpy change of wet steam before and after throttling (W), GgΔz is the potential energy change of wet steam before and after throttling (W), is the work done by wet steam before and after throttling (W), is the change in kinetic energy of wet steam before and after throttling (W). In addition, since the heated steam does not do work to the outside before and after throttling, the heat exchange is small, and the flow velocity and position differences before and after throttling are small, the above formula can be simplified to:

[0055]

[0056] In the formula, is the enthalpy value before throttling (W), is the enthalpy value after throttling (W); therefore, it can be considered that the enthalpy value of the heated wet steam before and after the pressure reduction through the throttling device 4 remains unchanged.

[0057] For further information, please refer to Figure 2 The specific introduction is as follows:

[0058] First, the first pressure measuring device measures the wet saturated steam in the first steam outlet pipe 2 and before the heater 3 to obtain the pressure P1 of the initial state before heating. Since the pressure in the saturated state is in a single-valued function relationship with the saturated gas phase enthalpy h″ and the saturated liquid phase enthalpy h′, the saturated gas phase enthalpy h″ and the saturated liquid phase enthalpy h′ of the saturated steam to be measured can be obtained according to P1 by using a mature physical property calculation program. Therefore, the enthalpy value of the saturated wet steam before heating is for:

[0059]

[0060] In the formula, is the enthalpy of saturated wet steam before heating (W), is the steam humidity, h″ is the saturated gas phase enthalpy (J / kg), h′ is the saturated liquid phase enthalpy (J / kg), and G is the steam mass flow rate (kg / s).

[0061] Secondly, heater 3 heats the wet steam at a constant pressure, and the heat input to the system is calculated using the following formula:

[0062]

[0063] In the formula, is the heat input to the system (W), U is the heater voltage (V), and I is the heater current (A).

[0064] Therefore, the total enthalpy of saturated wet steam before throttling is for:

[0065]

[0066] In the formula, is the enthalpy of saturated wet steam before heating (W), The heat input to the system for the heater (W).

[0067] Next, the second pressure measuring device measures the superheated steam in the second steam outlet pipe 9 to obtain the pressure P2 of the superheated steam after throttling, and the temperature measuring device measures the superheated steam in the second steam outlet pipe 9 to obtain the temperature T2 of the superheated steam after throttling. Because the enthalpy of superheated steam is only related to temperature and pressure, the enthalpy h2 of the superheated steam in the second steam outlet pipe 9 can be obtained according to P2 and T2 by using a mature physical property calculation program, and then the enthalpy is multiplied by the mass flow rate G of the superheated steam to obtain the total enthalpy Gh2 of the superheated steam after throttling. Since the total enthalpy remains unchanged before and after throttling, therefore:

[0068]

[0069] Where G is the mass flow rate of superheated steam (kg / s), is the enthalpy of wet steam before heating (W), is the heat input into the heater system (W), and h2 is the enthalpy of superheated steam (J / kg).

[0070] Furthermore, by combining the above formulas, we have:

[0071]

[0072] In the formula, is the steam humidity, h″ is the saturated gas phase enthalpy (J / kg), h′ is the saturated liquid phase enthalpy (J / kg), U is the heater voltage (V), I is the heater current (A), G is the superheated steam mass flow rate (kg / s), and h2 is the superheated steam enthalpy value (kJ / kg).

[0073] Finally, solving the above equation can give the humidity of saturated steam:

[0074]

[0075] In the formula, is the steam humidity, h″ is the saturated gas phase enthalpy (J / kg), h′ is the saturated liquid phase enthalpy (J / kg), U is the heater voltage (V), I is the heater current (A), G is the superheated steam mass flow rate (kg / s), and h2 is the superheated steam enthalpy value (J / kg).

[0076] Furthermore, if the first pressure measuring device mentioned above is set as the first pressure transmitter 5 installed on the inner wall of the first steam outlet pipe 2, the second pressure measuring device is set as the second pressure transmitter 6 installed on the inner wall of the second steam outlet pipe 9, and the temperature measuring device is set as the temperature transmitter 7 installed on the inner wall of the second steam outlet pipe 9, and the first pressure transmitter 5, the second pressure transmitter 6, the temperature transmitter 7 and the mass flow meter 12 are all connected to the humidity calculation device 8, then the humidity calculation device 8 can receive the electrical signals transmitted by the first pressure transmitter 5, the second pressure transmitter 6, the temperature transmitter 7 and the mass flow meter 12, and automatically calculate, generate and display the saturated steam humidity. Therefore, the steam humidity test system and method provided by the present invention can monitor the humidity of saturated steam online in real time, thereby further improving the practicality of the design device.

[0077] Specifically, the main body of the humidity calculation device is a computer, which is connected to a display, a keyboard, a USB interface, and a flow, temperature, and pressure data acquisition interface, so that all the aforementioned calculations are completed in the computer.

[0078] Furthermore, in the process of obtaining the aforementioned superheated steam enthalpy value h2, it is worth noting that in order to more accurately obtain the enthalpy value h2 of the superheated steam in the second steam outlet pipe 9 based on P2 and T2, it is necessary to set the second pressure measuring device and the temperature measuring device at the same cross-section of the second steam outlet pipe 9.

[0079] Specifically, the cross section where the second pressure measuring device and the temperature measuring device are set is preferably 5 to 10 times the inner diameter of the second steam outlet pipe 9 from one end of the air inlet. This arrangement, on the one hand, avoids the situation where the second pressure measuring device and the temperature measuring device are set too close to the air inlet end of the second steam outlet pipe, causing disturbances after steam throttling near the outlet of the throttling device 4, thereby affecting the accurate measurement of the superheated steam pressure and further affecting the accurate measurement of the superheated steam enthalpy. On the other hand, it also avoids the situation where the second pressure measuring device and the temperature measuring device are set too far from the air inlet end of the second steam outlet pipe 9, causing heat loss during steam transmission, thereby affecting the accurate measurement of the superheated steam temperature and further affecting the accurate acquisition of the superheated steam enthalpy. Therefore, the preferred setting distance is 5 to 10 times the inner diameter of the second steam outlet pipe 9.

[0080] Furthermore, in the present embodiment, thermal insulation cotton 10 is provided on the outer peripheries of the first steam outlet pipe 2 and the second steam outlet pipe 9 to prevent the heat of the steam from being lost and condensation from occurring, thereby increasing the measurement error.

[0081] Furthermore, an exhaust valve 11 for controlling the on / off connection of the second steam outlet pipe 9 with the outside world can be provided at the end of the second steam outlet pipe 9, so that it can be kept open to discharge exhaust gas when the humidity measurement system is working; and kept closed when the humidity measurement system is shut down; and the outlet flow rate can be adjusted by adjusting the opening of the valve.

[0082] To further illustrate the use effect of the present invention, three different saturated steam humidity measurement schemes will be compared in the following examples, and it is assumed that the steam humidity is a known value. Here, it is assumed that the humidity For 0.12:

[0083] After the exhaust valve 11 is opened, the saturated wet steam to be measured enters the first steam outlet pipe 2 from the steam main pipe 1, and its pressure P1 is measured after passing through the pressure transmitter 5. Here, it is assumed that the measured pressure P1 is 0.984MPa. Using the known steam humidity and saturated steam pressure P1. Through mature thermophysical property calculation program, the saturated wet steam enthalpy h1 in the initial state can be obtained as 2534 kJ / kg;

[0084] Option 1, using only throttling method:

[0085] Since only the throttling method is considered, the heater 3 does not work, and the wet steam is changed into a superheated state only by the pressure reduction effect of the throttling device 4. From formula 2, it can be seen that the enthalpy value before and after throttling remains unchanged, so the enthalpy h2 after throttling is also 2534 kJ / kg;

[0086] From h2=2534kJ / kg, using mature thermophysical property calculation program, we can get the dry saturated steam pressure corresponding to h2 as 0.002MPa;

[0087] This means that if only the throttling method is considered, when P1 is 0.984 MPa, if the humidity of steam with a humidity of about 0.12 is to be measured, the pressure drop caused by the throttling element 4 is at least 0.984-0.002=0.982 MPa;

[0088] The above calculations show that only using the throttling method to achieve the superheated state of steam will cause excessive steam pressure drop, and the flow pressure of the steam after pressure reduction will be too small, which will cause the suction and carrying capacity of the gas phase to be weakened and the deposition effect of the liquid phase to be enhanced, which is not conducive to the accurate measurement of the flow rate. Moreover, the pressure after throttling is lower than the standard atmospheric pressure, and maintaining the negative pressure state requires increasing the complexity and cost of the system.

[0089] Option 2, heating only:

[0090] Since only the heating method is considered, the throttling effect of the throttling device 4 is not considered for the time being, and only the heater 3 is relied on to provide heat to convert the wet steam into superheated steam. Since the heating process is a constant pressure, the pressure of the wet steam when it is heated from the initial state to the dry saturated superheated steam remains unchanged, which is P2 = P1 = 0.984MPa;

[0091] From P2=0.984MPa, using the thermophysical property calculation program, it can be obtained that the enthalpy value of the dry saturated superheated steam at this time is 2776kJ / kg, which means that if only the heating method is considered, when P1 is 0.984MPa, if the humidity of steam with a humidity of about 0.12 is to be measured, the heat input of heater 3 is at least 2776-2534=242kJ / kg. If the mass flow rate of wet steam is 1kg / s, the heating power required to heat it to superheat by the heating method is at least 242kW, which places too high requirements on the heating capacity of the system.

[0092] Scheme 3, using the heating throttling coupling method provided by the present invention:

[0093] For the convenience of quantitative comparison, it is assumed that the humidity of the wet saturated steam with a humidity of 0.12 and a pressure of 0.984 MPa is 0.05 after being heated at a constant pressure by the heater 3. Using the known humidity and pressure, through the thermophysical property calculation program, the enthalpy of the steam after heating can be obtained to be 2675 kJ / kg. Therefore, the heating amount required to be provided by the heater 3 is 2675–2534=141 kJ / kg;

[0094] After heating, the steam with reduced humidity is throttled through the throttling device 4. The enthalpy value before and after throttling remains unchanged, which is still 2675 kJ / kg. Therefore, the dry saturated superheated steam pressure corresponding to the enthalpy value can be obtained through the thermophysical property calculation program as 0.1 MPa.

[0095] Therefore, when the initial pressure of saturated steam is 0.984 MPa and the humidity is about 0.12, if the heating and throttling scheme provided by the present invention is adopted, the humidity of the wet steam is first heated from 0.12 to 0.05, and then throttling is performed. The required heating amount is 2675-2534=141 kJ / kg, and the pressure required for throttling to superheating is 0.1 MPa.

[0096] It can be seen that, compared with the throttling method of Scheme 1 and the heating method of Scheme 2, the heating amount required by Scheme 3 is reduced from 242 kJ / kg to 141 kJ / kg, and the pressure after throttling is increased from 0.002 MPa to 0.1 MPa.

[0097] The above comparison process is sufficient to illustrate that: first, the heater 3 is used to heat the wet steam at a constant pressure to reduce the humidity, and then the throttling method is used to reduce the pressure of the wet steam from a wet saturated state to a superheated state. This is smaller than the pressure drop required by the throttling method alone, and less than the heat required by the heating method alone. In other words, the measurement range of the present invention is larger than the measurement range of the heating method and throttling alone.

[0098] In summary, the throttling and heating coupled steam humidity measurement system of the present invention is provided with a first steam outlet pipe connected to the steam main pipe, a second steam outlet pipe connected to the end of the first steam outlet pipe by a throttling device, an exhaust port is provided at the end of the second steam outlet pipe, a first pressure measuring device is connected to the air inlet end of the first steam outlet pipe, a heater is provided in the first steam outlet pipe, and a second pressure measuring device, a temperature measuring device and a mass flow meter are connected in the second steam outlet pipe. The humidity of the flowing saturated steam is successfully calculated by obtaining the saturated gas phase enthalpy and saturated liquid phase enthalpy of the saturated steam flowing into the first steam outlet pipe, the voltage and current of the heater, the mass flow rate of the superheated steam flowing into the second steam outlet pipe and the enthalpy value of the superheated steam. The measurement method can realize the accurate measurement of the humidity of the flowing saturated steam with large flow and high humidity at low energy consumption. At the same time, it also has the characteristics of high tolerance to impurities, low cost, no need for visualization equipment, and a wide range of humidity and flow measurement. In addition, by connecting the first pressure transmitter, the second pressure transmitter, the temperature transmitter and the mass flowmeter for testing the saturated steam pressure before heating and the superheated steam pressure, temperature and flow after throttling to the humidity calculation device, real-time and convenient online measurement of the saturated steam humidity is achieved, which is of great significance for real-time monitoring of saturated steam flow and has broad application prospects.

[0099] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for measuring steam humidity by coupling throttling and heating, wherein: The method is based on a throttling and heating coupled steam humidity measurement system; The system comprises a first steam outlet pipe (2) connected to a steam main pipe (1), and a second steam outlet pipe (9) connected to the end of the first steam outlet pipe (2) via a throttling device (4); The air inlet end of the first steam outlet pipe (2) is connected to a first pressure measuring device, and a heater (3) is provided in the first steam outlet pipe (2); A second pressure measuring device, a temperature measuring device and a mass flow meter (12) are connected to the second steam outlet pipe (9), and an exhaust port is provided at the end of the second steam outlet pipe (9); The method comprises, Obtaining the saturated gas phase enthalpy and the saturated liquid phase enthalpy of the saturated steam flowing from the steam main pipeline (1) into the first steam outlet pipeline (2), the voltage and current of the heater (3), the mass flow rate of the superheated steam flowing into the second steam outlet pipeline (9), and the enthalpy value of the superheated steam; Calculating the humidity of the saturated steam according to the saturated gas phase enthalpy and the saturated liquid phase enthalpy of the saturated steam, the voltage and current of the heater (3), the mass flow rate of the superheated steam and the enthalpy value of the superheated steam; The calculation formula for calculating saturated steam humidity is: In the formula, is the steam humidity; h″ is the saturated gas phase enthalpy; h′ is the saturated liquid phase enthalpy; U is the heater voltage; I is the heater current; G is the mass flow rate of superheated steam; h2 is the enthalpy value of superheated steam.

2. The throttling and heating coupled steam humidity measurement method according to claim 1, wherein: The first pressure measuring device comprises a first pressure transmitter (5); The second pressure measuring device comprises a second pressure transmitter (6); The temperature measuring device comprises a temperature transmitter (7); The first pressure transmitter (5), the second pressure transmitter (6), the temperature transmitter (7) and the mass flow meter (12) are all connected to a humidity calculation device (8).

3. The throttling and heating coupled steam humidity measurement method according to claim 1, wherein: The outer circumferences of the first steam outlet pipe (2) and the second steam outlet pipe (9) are both provided with thermal insulation cotton (10).

4. The throttling and heating coupled steam humidity measurement method according to claim 1, wherein: An exhaust valve (11) for controlling the second steam outlet pipe (9) to be opened or closed to the outside is also provided at the end of the second steam outlet pipe (9).

5. The throttling and heating coupled steam humidity measurement method according to claim 1, wherein: The inner diameter of the first steam outlet pipe (2) is smaller than the inner diameter of the second steam outlet pipe (9).

6. The throttling and heating coupled steam humidity measurement method according to claim 2, wherein: The second pressure transmitter (6) and the temperature transmitter (7) are connected to the same cross section in the second steam outlet pipe (9).

7. The throttling and heating coupled steam humidity measurement method according to claim 6, wherein: The distance between the cross section and the air inlet end of the second steam outlet pipe (9) is 5 to 10 times the inner diameter of the second steam outlet pipe (9).

8. The method according to claim 1, wherein: Obtaining the saturated gas phase enthalpy and saturated liquid phase enthalpy of saturated steam, the mass flow rate of superheated steam, and the enthalpy value of superheated steam includes: Using a first pressure measuring device to obtain a pressure value P1 of saturated steam flowing from a steam main pipeline (1) into an air inlet end of a first steam outlet pipeline (2); The pressure P2 of the superheated steam after throttling is obtained by using the second pressure measuring device; Use the temperature measuring device to obtain the temperature T2 of the superheated steam after throttling; Using a mass flow meter (12) to obtain the mass flow of superheated steam after throttling; According to the pressure value P1 of the saturated steam, the saturated gas phase enthalpy and the saturated liquid phase enthalpy of the saturated steam are obtained; The enthalpy value of the superheated steam is obtained according to the pressure P2 of the superheated steam after throttling and the temperature T2 of the superheated steam after throttling.

9. The method according to claim 8, wherein: The first pressure measuring device comprises a first pressure transmitter (5); The second pressure measuring device comprises a second pressure transmitter (6); The temperature measuring device comprises a temperature transmitter (7); The first pressure transmitter (5), the second pressure transmitter (6), the temperature transmitter (7) and the mass flow meter (12) respectively transmit the acquired pressure, temperature or flow information to the humidity calculation device (8), and the humidity calculation device (8) completes the calculation of the saturated steam humidity.

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