A low-medium pressure steam dryness detector and a detection method thereof
Patent Information
- Application Number
- CN202610956832.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-30
- Publication Date
- 2026-10-27
AI Technical Summary
1、本发明通过螺旋的复杂扰流结构，提高待测蒸汽的受热均匀性并降低热损失；
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Abstract
Description
Technical Field
[0001] This invention relates to the field of pure steam quality testing technology for pharmaceutical and medical sterilization, and particularly to a medium-low pressure steam dryness tester and its testing method. Background Technology
[0002] Pure steam is a critical common medium in the aseptic manufacturing process of the pharmaceutical industry, widely used for online sterilization in moist heat sterilizers, bioreactors, liquid preparation systems, and clean pipelines. The dryness fraction of steam—the proportion of water vapor in the saturated steam to the total steam mass—directly determines the reliability and reproducibility of the sterilization process. According to EN285:2015, "Large Sterilizers," the steam dryness fraction for sterilizing metal containers must not be less than 0.95, and for non-metallic containers, it must not be less than 0.90. Insufficient dryness can lead to insufficient latent heat release, inability to maintain sterilization temperature, and the formation of "wet bags" on the containers, resulting in serious aseptic assurance risks.
[0003] Currently, the EN285 annex specifies the condensation method. This method uses Pitot tubes and Dewar flasks to collect condensate from steam and measure its mass, temperature, and initial water volume, calculating the dryness fraction based on heat balance. While the condensation method offers high theoretical accuracy as a standard reference method, it suffers from drawbacks in practical applications, including cumbersome operation, low efficiency, and significant human error.
[0004] As alternatives to condensation, there are other methods for monitoring dryness, such as throttling, heating, and weighing.
[0005] The heating method is one of the more promising technical approaches. The principle of the heating method is to throttle and expand steam to a low-pressure state, apply controllable heating power to ensure it enters the superheated zone, and then calculate the initial steam dryness fraction based on energy balance by measuring the temperature, pressure, and heating power before and after heating. However, this method still has shortcomings, such as: 1. Insufficient control of heat loss. The heating method relies on precise energy balance, that is, the balance between the applied electric power and the net heat absorbed by the steam. Traditional devices have relatively simple insulation measures for the detection pipeline, and some heat is lost to the environment through the pipe wall. Moreover, the amount of heat loss fluctuates with factors such as ambient temperature and airflow disturbance, which is difficult to compensate for accurately, leading to systematic errors in the dryness calculation. 2. Poor heating efficiency and steam mixing uniformity. Existing devices mostly use external heating or single-point internal heating. The heat exchange area between the heating element and the steam is limited, and the steam temperature distribution after heating is uneven. The temperature measured at the measuring point is difficult to represent the average temperature of the cross section, which affects the accurate determination of superheat. 3. Long detection time. Existing heating detection methods require sufficient heating of steam, resulting in a relatively long detection time to meet the heating conversion requirements. 4. Inaccurate flow rate detection and power feedback lead to large errors in the results. The accurate detection of steam flow rate largely affects the steam dryness result, and current methods make it difficult to accurately detect continuous flow rate under high temperature and high pressure conditions.
[0006] In summary, developing a heating-based steam dryness analyzer with controllable heat loss, high heating efficiency, thorough steam mixing, rapid detection, accurate results, and high integration is of significant engineering application value and market potential in meeting the urgent need for online, real-time, and accurate measurement of steam dryness in the field. Summary of the Invention
[0007] Technical objective: To address the deficiencies in existing technologies, this invention discloses a medium-low pressure steam dryness detector and its detection method, enabling rapid, stable, and accurate detection of the dryness value of small-flow medium-low pressure steam.
[0008] Technical solution: To achieve the above technical objectives, the present invention adopts the following technical solution.
[0009] A medium-low pressure steam dryness detector includes: a steam inlet channel, a steam dryness heat pipe, a resistance heating component, a power closed-loop control component, a temperature detection component, a pressure detection component, an adjustable current limiting unit, a condensation component, a condensate volume measurement component, and a controller. One end of the steam inlet channel is a steam inlet, and the other end is connected to the steam dryness heat pipe; the steam inlet channel is equipped with a pressure detection component connected to the controller; The steam dryness heat pipe has a concentric inner and outer ring pipe structure, which is used to form a channel for steam heating and parameter detection; the steam dryness heat pipe includes an inner ring pipe and an outer ring channel, and the steam flows out of the inner ring pipe and then back to the outer ring channel; The resistance heating element is installed inside the steam dryness heat pipe parallel to the steam flow direction and extends outside the steam dryness heat pipe. It is used to input controllable heat to the steam to be measured, so that the steam reaches a superheated state. The resistance heating element is connected to the power closed-loop control element. The power closed-loop control element is connected to the controller. The controller realizes closed-loop control of the heating power of the resistance heating element according to the feedback signal of the power meter. The steam dryness heat pipe has an internal turbulence structure to improve the flow state of steam in the heating channel; the temperature detection component is used to detect the temperature parameters of steam before and after heating. The output end of the steam dryness heat tube is equipped with an adjustable flow limiting unit, which is used to limit and regulate the flow of the steam to be tested entering the detection system; The adjustable flow limiting unit is connected to the condensation component, which is used to fully condense the heated steam into liquid water for condensate flow measurement; the condensation component is also connected to the condensate volume measurement component, which is used to continuously measure the change in condensate volume over time. The controller is used to acquire the temperature parameters before and after steam heating fed back by the temperature detection component, the real-time pressure of the steam to be measured fed back by the pressure detection component, the actual input power of the resistance heating component fed back by the power closed-loop control component, and the liquid level height fed back by the condensate volume measurement component; and to calculate the steam mass flow rate and steam dryness fraction based on heat balance and condensate volume-time slope.
[0010] This invention also discloses a detection method for a medium-low pressure steam dryness analyzer, applied to the medium-low pressure steam dryness analyzer described above, comprising the following steps: S1. The steam to be tested is introduced into the steam dryness heat pipe from the steam inlet 1, and the temperature T1 and pressure P1 of the steam to be tested before heating are detected. S2. In the steam dryness heat tube, the steam to be tested is heated to a superheated state under the action of the resistance heating component until the temperature T2 and heating power W of the heated steam to be tested are obtained in a smooth and stable manner. S3. Control the steam to be tested to enter the outer ring channel for heat preservation. The output end of the outer ring channel is connected to the adjustable flow limiting unit. The flow rate of the steam to be tested is adjusted by the adjustable flow limiting unit to match the heating capacity and condensation capacity, and then it enters the condensation component. S4. The steam to be tested is introduced into the condensation component for condensation to obtain liquid condensate, which flows into the condensate volume measurement component. The condensate volume measurement component includes a graduated cylinder with a certain cross-sectional area to obtain the pressure difference DP1. The liquid level is calculated by the pressure difference DP1. The graduated cylinder is emptied and recalculated after it is full. S5. Within the stable time interval of the temperature T1, temperature T2, pressure P1, and power W of the steam to be tested, continuously measure the data of the condensate volume change with time, select the stable interval of the condensate volume-time curve, and calculate the slope of the volume with respect to time within the stable interval, i.e., the steam mass flow rate Q, and then calculate the dryness fraction D.
[0011] Beneficial effects: 1. This invention improves the heating uniformity of the steam under test and reduces heat loss through a complex spiral turbulence structure; 2. This invention controls the resistance heating component through a power closed-loop control component, thereby improving the accuracy of heat input during the heating process of the steam to be tested; in addition, the resistance heating component is set inside the steam dryness heat pipe to achieve full heating, which greatly shortens the detection time, with a single detection time range of 2-5 minutes; 3. This invention detects the temperature T1, T2, pressure P1, and power W of superheated steam. Based on the stable range of all values and the condensate volume-time slope flow rate calculation mechanism, the steam flow rate Q is calculated, and then the dryness value of the steam to be tested is calculated. It can be continuously monitored, and the dryness value can be monitored in real time by the change of the stable value slope, so as to quickly, stably and accurately detect the steam dryness value. Attached Figure Description
[0012] Figure 1 This is a schematic diagram of a medium-low pressure steam dryness detector according to Embodiment 1 of the present invention; Figure 2 for Figure 1 Schematic diagram of the structure of a medium steam dryness heat pipe; Figure 3 for Figure 2 Cross-sectional view; Figure 4 for Figure 2 A 45° oblique cross-sectional view; Figure 5 for Figure 2 A schematic diagram showing the flow direction of the steam to be tested. Figure 6 for Figure 1 Schematic diagram of the central condenser assembly and condensate volume measurement assembly; Figure 7 This is a schematic diagram of a medium-low pressure steam dryness detector according to Embodiment 1 of the present invention. Figure 1 ; Figure 8 This is a schematic diagram of a medium-low pressure steam dryness detector according to Embodiment 1 of the present invention. Figure 2 . Detailed Implementation
[0013] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.
[0014] Example 1: As shown in the attached document Figure 1 To be continued Figure 8As shown in the figure, this embodiment of a low-pressure steam dryness detector is suitable for detecting the dryness of steam at low flow rates and low pressures. Low flow rate refers to a flow rate generally not exceeding 100 mL per minute; low pressure refers to a steam pressure below 1 MPa. This embodiment of the low-pressure steam dryness detector includes: a steam inlet channel, a steam dryness heat pipe, a resistance heating component, a power closed-loop control component, a temperature detection component, a pressure detection component, an adjustable flow limiting unit, a condensation component, a condensate volume measurement component, and a controller. The controller and its corresponding connections are not shown in the accompanying drawings.
[0015] One end of the steam intake channel is a steam inlet 1, and the other end is connected to the steam dryness heat pipe 4. The steam to be tested enters the steam intake channel from the steam inlet 1 and flows to the steam dryness heat pipe. The steam intake channel is equipped with a pressure detection component connected to the controller. The pressure detection component includes a pressure sensor 3. The pressure sensor 3 is used to detect the real-time pressure of the steam to be tested and feed it back to the controller.
[0016] As attached Figure 4 As shown, the steam dryness heat pipe has a concentric inner and outer ring pipe structure, used to form a channel for steam heating and parameter detection. The steam dryness heat pipe includes an inner ring pipe 12 and an outer ring channel 13; The inner ring pipe 12 is the steam flow channel to be tested and also the steam heating channel. After the steam flows out of the inner ring pipe 12 to the top, it turns back to the outer ring channel 13. The outer ring channel 13 is used to insulate the inner ring steam channel, thereby reducing the impact of environmental heat dissipation.
[0017] The resistance heating element 5 is positioned parallel to the steam flow direction inside the steam dryness heat pipe and extends beyond it. It is used to input controllable heat into the steam to be measured, causing the steam to reach a superheated state. One end of the resistance heating element is located at the center of the inner ring pipe 12 and parallel to the pipe itself, ensuring that the heating part of the resistance heating element is completely immersed in the flowing steam atmosphere. The resistance heating element is connected to a power closed-loop control component. The resistance heating element includes a heating rod, the front end of which is located inside the steam dryness heat pipe, specifically at the center of the inner ring pipe 12. The electrical interface at the base of the heating rod extends out of the steam dryness heat pipe and connects to the power closed-loop control component, which regulates the heating power of the heating rod. The power closed-loop control component includes an adjustable voltage output power supply and a power meter. The power meter is connected to the circuit loop of the resistance heating element and the adjustable voltage output power supply, and communicates with the controller to detect the actual input power of the resistance heating element in real time and feed it back to the controller. An adjustable voltage output power supply is connected to the resistance heating component and the controller. The controller adjusts the output voltage of the adjustable voltage output power supply based on the feedback signal from the power meter to achieve closed-loop control of the heating power of the resistance heating component. This invention introduces a closed-loop control mechanism for resistance heating power. Through the cooperation of power meter feedback and the adjustable voltage output power supply, the heating input power is made stable and controllable, ensuring the accuracy of heat balance calculation.
[0018] In this embodiment, the heating rod is a divergent cylindrical heating rod, for example, a divergent structure with a sunflower-shaped cross-section, used to improve the heat exchange area and heat exchange uniformity between steam and the resistance heating component. In this invention, the heating rod adopts a small sunflower-shaped cross-section to further increase the surface area for heat exchange.
[0019] The steam dryness heat pipe has an internal turbulence structure to improve the flow state of steam in the heating channel, enhance the heat exchange between steam and heating components, reduce local temperature differences, and improve the representativeness of the outlet temperature measurement. The turbulence structure includes a heating diffuser 8, a baffle 9, a first guide block 10, and a second guide block 11 in the order of contact with the steam. After the steam enters, the steam pressure pushes against the second guide block 11, thereby pushing the first guide block 10 forward.
[0020] In general, resistance heating in straight channels often results in insufficient contact between steam and air due to excessively fast steam flow, leading to energy interaction and significant calculation errors. This invention designs a spiral hot steam channel that combines turbulence reduction to ensure sufficient and uniform heating of the steam. Through a series of spiral turbulence plates, porous turbulence plates, baffles, mesh mixing components, swirl vanes, diversion and re-convergence structures, annular guide vanes, and stepped flow channel structures, the heating process is made uniform, the airflow is fully contacted, and the energy conversion is ultimately calculated accurately.
[0021] The temperature detection component includes a first temperature sensor 2 and a second temperature sensor 6, used to detect temperature parameters before and after steam heating or at key locations. In this embodiment, the first temperature sensor 2 is installed on the steam inlet channel to detect the real-time temperature of the steam to be tested, i.e., the temperature value of the steam to be tested before heating, and feeds it back to the controller; the second temperature sensor 6 is installed at the connection between the inner ring pipe 12 and the outer ring channel 13, i.e., at the rear end of the inner ring pipe 12, to improve the accuracy of characterizing the superheated steam state.
[0022] The output end of the steam dryness heat pipe is equipped with an adjustable flow limiting unit 7. The adjustable flow limiting unit is used to limit and regulate the flow of the steam to be tested entering the detection system so that the steam flow rate matches the subsequent heating capacity and condensation capacity.
[0023] The adjustable flow limiting unit can be an orifice plate, needle valve, regulating valve, or variable orifice structure.
[0024] The adjustable flow limiting unit is connected to the condenser assembly 14, which is used to fully condense the heated steam into liquid water for condensate flow rate measurement. The condenser assembly is a condenser coil.
[0025] The condensation component is connected to the condensate volume measurement component, which is used to continuously measure the change in condensate volume over time.
[0026] The condensate volume measurement component includes a graduated cylinder 15 and a differential pressure sensor mounted on the graduated cylinder 15. The graduated cylinder 15 is connected to the condensation component, and a drain outlet 16 is provided at the bottom of the graduated cylinder 15. The condensate volume measurement component can use a differential pressure sensor on a fixed container to obtain the differential pressure and convert it into liquid level height to calculate the condensate flow rate. However, it is not limited to using other methods such as graduated cylinder reading, liquid level sensor, weighing conversion, image recognition, etc. The preferred method is a measurement method that can output continuous volume-time data.
[0027] In this embodiment, the temperature sensor, pressure sensor, and differential pressure sensor preferably adopt a quick-release universal interface to facilitate metrological verification, maintenance and replacement, and adaptation to different application scenarios.
[0028] The controller is used to acquire the temperature parameters before and after steam heating fed back by the temperature detection component, the real-time pressure of the steam to be measured fed back by the pressure detection component, the actual input power of the resistance heating component fed back by the power closed-loop control component, and the liquid level height fed back by the condensate volume measurement component, i.e. the liquid level height fed back by the differential pressure sensor on the measuring cylinder; and to calculate the steam mass flow rate and steam dryness based on heat balance and condensate volume-time slope.
[0029] As attached Figure 1 Appendix Figure 7 and attached Figure 8The diagram shown is a physical representation of the structure of this invention. The upper part includes a steam dryness heat pipe and a condensate volume measuring component, while the lower part is a condensation component. The yellow part represents the steam inlet channel and the steam dryness heat pipe, while the rose-red part represents the measuring cylinder and the condensation coil.
[0030] The detection method of a medium-low pressure steam dryness detector according to this embodiment includes the following steps: S1. The steam to be tested is introduced into the steam dryness heat pipe from the steam inlet 1, and the temperature T1 and pressure P1 of the steam to be tested before heating are detected. S2. In the steam dryness heat pipe, the steam to be tested is heated to a superheated state under the action of the resistance heating component until a smooth and stable temperature T2 and heating power W of the heated steam are obtained. The resistance heating component applies energy using power W1, and the power closed-loop control component detects the power W2 in real time, obtaining the final power index as the heating power W through closed-loop control. In this embodiment, the temperature T2 of the heated steam needs to be higher than the temperature T1 of the steam before heating by a preset threshold. For example, if the preset threshold is set to 25°C, temperature regulation can be achieved by performing PID closed-loop control in the power closed-loop control component and adjusting the power of the resistance heating component.
[0031] S3. The steam to be tested is controlled to enter the outer ring channel 13 for heat preservation. The output end of the outer ring channel 13 is connected to an adjustable flow limiting unit. The adjustable flow limiting unit adjusts the flow rate of the steam to be tested to match its heating and condensing capabilities before it enters the condensing assembly. Specifically, if the adjustable flow limiting unit uses an orifice plate, the flow rate is adjusted by removing the chuck and replacing the orifice plate in the middle. Alternatively, if the adjustable flow limiting unit uses a needle valve or a regulating valve, the flow rate is controlled by adjusting the valve opening. In actual use, continuous adjustment is not required; adjustment is only needed once based on the site conditions.
[0032] S4. The steam to be tested is introduced into the condensation component for condensation to obtain liquid condensate, which flows into the condensate volume measurement component. The condensate volume measurement component includes a graduated cylinder with a certain cross-sectional area to obtain the pressure difference DP1. The liquid level is calculated by using the pressure difference DP1. After the graduated cylinder is full, it is emptied through the drain port and the calculation is repeated.
[0033] S5. Within the stable time interval of the temperature T1, temperature T2, pressure P1, and power W of the steam to be tested, continuously measure the data of the condensate volume change with time, select the stable interval of the condensate volume-time curve, and calculate the slope of the volume with respect to time within the stable interval, i.e., the steam mass flow rate Q, and then calculate the dryness fraction D. The formula for calculating the steam mass flow rate Q is as follows: , Where Q is the stable steam mass flow rate, V is the condensate volume, t is the time for collecting condensate, DP is the corresponding pressure difference value, k is a parameter related to the cross-sectional area of the graduated cylinder, and is a fixed parameter of the graduated cylinder.
[0034] The formula for calculating dryness fraction D is: , Where D is dryness fraction, h is specific enthalpy of steam, hf is specific enthalpy of steam in liquid state, hg is specific enthalpy of steam in gaseous state, hfg is latent heat of vaporization, P is specific energy, ht2 is the enthalpy value of steam in superheated state after heating, which is a fixed value under stable pressure and temperature regulation, W is the stable power of heating rod, and Q is the steam mass flow rate.
[0035] This invention determines the enthalpy of superheated steam by detecting the temperature T1, T2, and pressure P1 of superheated steam, as well as the power W and flow rate Q, based on the stable interval values of all these values. It also calculates the dryness fraction of the steam under test and can perform continuous monitoring, using the change in the slope of the stable value to monitor the change in dryness fraction in real time.
[0036] The dryness measurement of this invention mainly relies on the condensate volume-time slope flow rate calculation mechanism. Compared with the single-point condensate volume difference calculation in the prior art, this invention uses the slope of the stable interval of the continuously collected volume-time curve to calculate the steam flow rate, and then calculates the dryness, which improves the accuracy of the calculation.
[0037] In the embodiments of this application, the terms "first" and "second" (if they exist) are used only as name identifiers and do not represent the order of first and second.
[0038] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A medium-low pressure steam dryness detector, characterized in that, include: Steam inlet channel, steam dryness heat pipe, resistance heating component, power closed-loop control component, temperature detection component, pressure detection component, adjustable current limiting unit, condensation component, condensate volume measurement component, and controller; One end of the steam inlet channel is a steam inlet, and the other end is connected to the steam dryness heat pipe; the steam inlet channel is equipped with a pressure detection component connected to the controller; The steam dryness heat pipe has a concentric inner and outer ring pipe structure, which is used to form a channel for steam heating and parameter detection; the steam dryness heat pipe includes an inner ring pipe and an outer ring channel, and the steam flows out of the inner ring pipe and then back to the outer ring channel; The resistance heating element is installed inside the steam dryness heat pipe parallel to the steam flow direction and extends outside the steam dryness heat pipe. It is used to input controllable heat to the steam to be measured, so that the steam reaches a superheated state. The resistance heating element is connected to the power closed-loop control element. The power closed-loop control element is connected to the controller. The controller realizes closed-loop control of the heating power of the resistance heating element according to the feedback signal of the power meter. The steam dryness heat pipe has an internal turbulence structure to improve the flow state of steam in the heating channel; the temperature detection component is used to detect the temperature parameters of steam before and after heating. The output end of the steam dryness heat tube is equipped with an adjustable flow limiting unit, which is used to limit and regulate the flow of the steam to be tested entering the detection system; The adjustable flow limiting unit is connected to the condensation component, which is used to fully condense the heated steam into liquid water for condensate flow measurement; the condensation component is also connected to the condensate volume measurement component, which is used to continuously measure the change in condensate volume over time. The controller is used to acquire the temperature parameters before and after steam heating fed back by the temperature detection component, the real-time pressure of the steam to be measured fed back by the pressure detection component, the actual input power of the resistance heating component fed back by the power closed-loop control component, and the liquid level height fed back by the condensate volume measurement component; and to calculate the steam mass flow rate and steam dryness based on heat balance and condensate volume-time slope.
2. The medium-low pressure steam dryness detector according to claim 1, characterized in that: The resistance heating assembly includes a heating rod with its front end located inside the steam dryness heat pipe. An electrical interface at the base of the heating rod extends out of the steam dryness heat pipe and is connected to a power closed-loop control assembly.
3. The medium-low pressure steam dryness detector according to claim 1, characterized in that: The power closed-loop control component includes an adjustable voltage output power supply and a power meter. The power meter is connected to the circuit loop of the resistance heating component and the adjustable voltage output power supply, and communicates with the controller to detect the actual input power of the resistance heating component in real time and feed it back to the controller. The adjustable voltage output power supply is connected to the resistance heating component and the controller. The controller adjusts the output voltage of the adjustable voltage output power supply according to the feedback signal from the power meter to achieve closed-loop control of the heating power of the resistance heating component.
4. The medium-low pressure steam dryness detector according to claim 1, characterized in that: The temperature detection component includes a first temperature sensor and a second temperature sensor. The first temperature sensor is installed on the steam inlet channel to detect the real-time temperature of the steam to be tested, i.e., the temperature value of the steam to be tested before heating, and feeds it back to the controller. The second temperature sensor is installed at the connection between the inner ring pipe and the outer ring channel, i.e., at the rear end of the inner ring pipe channel.
5. The medium-low pressure steam dryness detector according to claim 1, characterized in that: The condensate volume measurement component includes a graduated cylinder and a differential pressure sensor mounted on the graduated cylinder, which is used to acquire the differential pressure and convert it into liquid level height, thereby calculating the condensate flow rate.
6. The medium-low pressure steam dryness detector according to claim 2, characterized in that: The heating rod is a divergent cylindrical heating rod.
7. The medium-low pressure steam dryness detector according to claim 1, characterized in that: The pressure detection component includes a pressure sensor, which detects the real-time pressure of the steam to be tested and feeds it back to the controller.
8. A detection method for a medium-low pressure steam dryness analyzer, applied to a medium-low pressure steam dryness analyzer as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. The steam to be tested is introduced into the steam dryness heat pipe from the steam inlet 1, and the temperature T1 and pressure P1 of the steam to be tested before heating are detected. S2. In the steam dryness heat tube, the steam to be tested is heated to a superheated state under the action of the resistance heating component until the temperature T2 and heating power W of the heated steam to be tested are obtained in a smooth and stable manner. S3. Control the steam to be tested to enter the outer ring channel for heat preservation. The output end of the outer ring channel is connected to the adjustable flow limiting unit. The flow rate of the steam to be tested is adjusted by the adjustable flow limiting unit to match the heating capacity and condensation capacity, and then it enters the condensation component. S4. The steam to be tested is introduced into the condensation component for condensation to obtain liquid condensate, which flows into the condensate volume measurement component. The condensate volume measurement component includes a graduated cylinder with a certain cross-sectional area to obtain the pressure difference DP1. The liquid level is calculated by the pressure difference DP1. The graduated cylinder is emptied and recalculated after it is full. S5. Within the stable time interval of the temperature T1, temperature T2, pressure P1, and power W of the steam to be tested, continuously measure the data of the condensate volume change with time, select the stable interval of the condensate volume-time curve, and calculate the slope of the volume with respect to time within the stable interval, i.e., the steam mass flow rate Q, and then calculate the dryness fraction D.
9. The detection method of a medium-low pressure steam dryness detector according to claim 8, characterized in that: The formula for calculating the steam mass flow rate Q is: ， Where Q is the stable steam mass flow rate, V is the condensate volume, t is the time for collecting condensate, DP is the corresponding pressure difference value, and k is a parameter related to the cross-sectional area of the graduated cylinder.
10. The detection method of a medium-low pressure steam dryness detector according to claim 8, characterized in that: The formula for calculating dryness fraction D is: ， Where D is dryness fraction, h is specific enthalpy of steam, hf is specific enthalpy of steam in liquid state, hg is specific enthalpy of steam in gaseous state, hfg is latent heat of vaporization, P is specific energy, ht2 is the enthalpy value of steam in superheated state after heating, W is the stable power of heating rod, and Q is steam mass flow rate.