Method and device for measuring thickness of surface liquid film

Abstract

The invention relates to the field of liquid film thickness measurement, and provides a surface liquid film thickness measurement method and device. The device comprises an annular fixer, a rotating motor, a stepping motor, a probe, a slide rail stabilizer and the like. And the annular fixer fixes the test tube through a bolt and adapts to different tube diameters. The rotating motor drives the annular rotator to rotate, so that the circumferential movement of the probe is realized; the electric horizontal guide rail drives the sliding block and the stepping motor to achieve axial movement of the probe, and three-dimensional accurate positioning of the probe is completed. The probe is in contact with the liquid film and the pipe wall to form a closed circuit, and the moving state of the probe is monitored through current changes. The device can realize automatic, precise and multi-point distribution measurement of the thickness of the liquid film on the surface of the pipeline, has the advantages of simple structure, convenience in operation, stability, reliability, high applicability and low cost, and is widely applicable to measurement and analysis of the thickness of the industrial liquid film.

Description

Technical Field

[0001] The invention relates to the field of liquid film thickness measurement, and in particular to a method and a device for measuring the thickness of a surface liquid film. Background Art

[0002] Water is the source of life, the most important natural resource on earth, and the basis for the survival of human beings and other life. At present, my country is facing the severe problem of insufficient clean water resources. Wastewater desalination treatment is of great significance to solving the shortage of water resources. Existing wastewater desalination technologies include distillation, reverse osmosis, electrolysis and ion exchange. Among them, low-temperature multi-effect evaporation is widely used due to its low water quality requirements and simple operation. Liquid film thickness is one of the key factors affecting the heat exchange efficiency of low-temperature multi-effect evaporation heat exchanger. A thinner liquid film can reduce the thermal resistance during falling film evaporation, thereby increasing the heat exchange efficiency; a thicker liquid film can improve the stability of the film, making it less likely to break or fail, thereby improving the separation efficiency and evaporation efficiency. Existing liquid film measurement methods include laser method, ultrasonic method and spectral confocal method. These methods have the problems of high cost and difficult operation in measuring the liquid film thickness in falling film evaporator in industrial applications. In order to study the influence of liquid film thickness on the heat exchange efficiency of low-temperature multi-effect evaporator during falling film evaporation. Therefore, a measuring device is needed that is low-cost, easy to operate, highly automated, and can quickly and accurately measure the liquid film thickness on the surface of the heat exchange tube at different positions during the mold falling evaporation process. Summary of the invention

[0003] In view of the deficiencies in the prior art, the present invention provides a method and device for measuring the thickness of a surface liquid film.

[0004] In a first aspect, the present invention provides a method for measuring the thickness of a surface liquid film. The method comprises: The probe is combined with a stepper motor to accurately measure the thickness of the liquid film by controlling the movement of the probe with an electrical signal. This method uses a closed circuit formed by the contact between the probe, the liquid film and the metal tube wall to reflect the change in the contact state between the probe and the liquid film through changes in current. During the measurement process, the probe is initially in direct contact with the tube wall, and the ammeter reading is the largest at this time; as the stepper motor drives the probe away from the tube wall, the circuit resistance gradually increases and the current gradually decreases due to the presence of the liquid film. When the probe is completely separated from the liquid film, the circuit is disconnected and the current drops to zero. At this time, the total movement distance of the stepper motor is recorded, which is the thickness of the liquid film.

[0005] In a second aspect, the present invention provides a device for measuring the thickness of a surface liquid film. The device comprises: Annular holder 1, threaded through hole 2, test tube avoidance hole 3, rotating motor 4, rotating motor holder 5, annular rotator 6, annular guide rail 7, slide rail stabilizer 8, annular gear 9, electric horizontal guide rail 10, electric horizontal guide rail holder 11, stepper motor holder 12, probe avoidance hole 13, stepper motor 14, probe 15, bearing 16, wire 17, power supply 18, ammeter 19, switch 20, data cable 21, computer 22, test tube 23, slider 24.

[0006] The annular fixer 1 is provided with a threaded through hole 2, the test tube 23 passes through the test tube avoidance hole 3, the bolt is connected to the threaded through hole 2 and fixes the test tube 23 to the annular fixer 1; the annular fixer 1 and the rotating motor fixer 5 are provided with screw holes, the rotating motor fixer 5 is connected to the annular fixer 1 by bolts and fixes the rotating motor 4 to the annular fixer 1.

[0007] The slide rail stabilizer 8 is further connected to the annular guide rail 7 through a pulley, and the slide rail stabilizer 8 can slide on the annular guide rail 7; the annular guide rail 7 and the annular gear 9 are provided with screw holes, and the annular guide rail 7 and the annular gear 9 are connected by bolts, and the annular rotator 6 is provided with and groove, and the annular rotator 6 groove and the annular gear 9 are both provided with screw holes, and the annular rotator 6 and the annular gear 9 are connected by bolts.

[0008] The annular rotator 6 is further connected to the annular fixer 1 via a bearing 16 ; the shaft of the rotating motor 4 is transmission-connected to the annular gear 9 , and the rotating motor 4 drives the annular rotator 6 to rotate.

[0009] The electric horizontal guide rail fixture 11 is further connected to the annular rotator 6 by bolts and the electric horizontal guide rail 10 is fixed to the annular rotator 6; the electric horizontal guide rail 10 is provided with a slider 24, and the slider 24 and the stepper motor fixture 12 are both provided with threaded holes, the stepper motor fixture 12 is connected to the slider 24 by bolts and the stepper motor 14 is fixed to the slider 24, and the stepper motor 14 passes through the probe avoidance hole 13.

[0010] Furthermore, the probe 15 and the test tube 23 are respectively connected to the positive and negative electrodes of the power supply 18 through the wire 17, and the wire 17 is provided with an ammeter 19 and a circuit switch 20; the stepper motor 14, the rotary motor 4 and the electric horizontal guide rail 10 are connected to the computer 22 through the data line 21.

[0011] Compared with the existing liquid film thickness measuring device, the present invention has the following advantages.

[0012] 1. A method and device for measuring the thickness of a surface liquid film. The method introduces a stepper motor, which is combined with a probe to accurately control the position of the probe through an electrical signal, so that the measurement of the liquid film thickness is more stable and accurate. At the same time, the structure is simple and easy to change. The device structure can be changed according to engineering requirements, and stepper motors of different specifications and precisions can be replaced according to engineering requirements and the range of liquid film thickness.

[0013] 2. A method and device for measuring the thickness of a surface liquid film. The design of the measuring device structure enables it to measure the thickness of the liquid film at different circumferential angles and axial positions of the tube, thereby fully understanding the distribution of the liquid film thickness and improving the comprehensiveness of the measurement. The circumferential and axial movement of the probe is completed by a computer-controlled motor drive, which makes the device not only highly automated, but also more accurate and easy to control in the three-dimensional movement of the probe.

[0014] 3. A method and device for measuring the thickness of a surface liquid film. Compared with traditional measuring devices, the measuring device is low-cost, stable and reliable, and has a high degree of automation, and is more suitable for accurate measurement of the thickness of a surface liquid film in industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The present invention is a schematic structural diagram of a measuring device for measuring the thickness of a surface liquid film.

[0016] Figure 2 for Figure 1 Schematic diagram of the structure of the middle ring gear and the ring guide

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0018] In the description of the invention, it should be noted that the orientation or positional relationship indicated by the terms "top", "bottom", "one side", "the other side", "front", "back", "middle part", "inside", "top end", "bottom end", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the invention; the terms "first", "second", and "third" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance; in addition, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0019] like Figure 1 The figure shows a measuring device for measuring the thickness of a surface liquid film, comprising an annular fixture 1, a threaded through hole 2, a test tube avoidance hole 3, a rotating motor 4, a rotating motor fixture 5, an annular rotator 6, an annular guide rail 7, a slide rail stabilizer 8, an annular gear 9, an electric horizontal guide rail 10, an electric horizontal guide rail fixture 11, a stepper motor fixture 12, a probe avoidance hole 13, a stepper motor 14, a probe 15, a bearing 16, a wire 17, a power supply 18, an ammeter 19, a switch 20, a data line 21, a computer 22, a test tube 23, and a slider 24.

[0020] Specifically, the liquid film thickness measuring device of the present scheme includes an annular fixture 1 at the left and right ends. The annular fixture 1 has a circular ring shape, and a test tube avoidance hole 3 is provided in the center part for allowing test tubes of different diameters to pass through. The surface of the annular fixture 1 is provided with three evenly distributed threaded through holes 2 for installing bolts. These bolts extend into the test tube avoidance holes 3 through the threaded through holes 2 and directly squeeze the test tube 23, thereby achieving the fixation of the test tube 23. This design enables the device to adapt to test tubes 23 of different outer diameters, and has higher versatility and flexibility. The cross-section of the annular fixture 1 is designed with a threaded hole, which is used to connect the rotating motor 4 to the rotating motor fixture 5 through bolts and fix it on the annular fixture 1.

[0021] The annular rotator 6 is provided with a groove, and the groove surface is provided with a plurality of threaded holes. The annular gear 9 is provided with a threaded hole, and the annular gear 9 is connected and fixed to the annular rotator 6 by bolts, and the bolts also fix the annular guide rail 7 to the annular gear 9. The cross section of the annular rotator 6 is designed with a threaded hole, and the threaded hole connects the electric horizontal guide rail 10 with the electric horizontal guide rail fixture 11 and fixes it on the annular rotator 6 by bolts. A slider 24 is provided on the electric horizontal guide rail 10, and a plurality of threaded holes are provided on the slider 24, and these threaded holes are used to install the stepper motor fixture 12, so as to connect the stepper motor 14 with the slider. A probe avoidance hole 13 is provided in the center of the stepper motor fixture 12, and the purpose of designing the hole is to allow the probe 15 to pass through. The slider 24 can be driven by the electric horizontal guide rail 10 according to demand, driving the probe 15 to move along the axial direction of the test tube 23, so that the device can flexibly measure the liquid film thickness at different positions of the test tube 23.

[0022] The annular holder 1 is provided with a bearing hole, and the annular rotator 6 is provided with a shaft, and the shaft of the annular rotator 6 is connected to the annular holder through a bearing 16. A through hole is provided on the slide rail stabilizer 8, and the shaft of the rotary motor 4 is connected to the annular gear 9 fixed on the annular rotator 6 after passing through the through hole. The annular rotator 6 can be driven by the rotary motor 4 according to demand, driving the probe 15 to move along the circumference of the test tube 23, so that the device can flexibly measure the liquid film thickness at different positions of the test tube 23.

[0023] The probe 15 and the test tube 23 are connected to the positive and negative electrodes of the power supply 18 through the wire 17, and the wire 17 is provided with an ammeter 19 and a circuit switch 20. The stepper motor 14, the rotary motor 4 and the electric horizontal guide rail 10 are connected to the computer 22 through the data line 21.

[0024] The measuring process of the liquid film thickness measuring device of this scheme is as follows: first, the annular fixture 1 is installed on the test tube 23, so that the test tube 23 passes through the test tube avoidance hole 3, and the test tube 23 is fixed to the annular fixture 1 by bolts. While tightening the bolts, adjust the tightness of the bolts to ensure that the annular fixture 1 is firmly connected to the test tube 23 to avoid displacement or shaking of the test tube during subsequent measurements. Next, the rotating motor fixture 5 is aligned and fixed with the threaded holes on the annular fixture 1 by bolts, and the rotating motor 4 is installed on the rotating motor fixture 5. The annular rotator 6 is connected to the bearing in the annular fixture 1 through the shaft rod to ensure the smooth rotation of the rotator. Then the shaft rod of the rotating motor is passed through the through hole on the slide rail stabilizer 8 and connected to the ring gear 9. The slide rail stabilizer 8 is connected to the annular guide rail 7 through a pulley to ensure the stability and accuracy of the rotating motor during operation. The cross section of the annular rotator 6 is designed with threaded holes, and the electric horizontal guide rail holder 11 and the electric horizontal guide rail 10 are installed on the annular rotator 6 by bolts to form a horizontal movement structure of the probe.

[0025] The slider 24 is designed with a plurality of threaded holes for installing the stepper motor holder 12, thereby fixing the stepper motor 14 to the slider 24. A probe avoidance hole 13 is provided at the center of the stepper motor holder 12 to ensure that the output shaft of the stepper motor can freely extend through the probe avoidance hole 13 and drive the probe 15 to move in the vertical direction.

[0026] Connect the probe 15 to the positive and negative electrodes of the power supply 18 through the wire 17, and connect the ammeter 19 and the circuit switch 20 in the circuit to monitor the current change when the probe contacts the liquid film. Connect the rotary motor 4, the electric horizontal guide rail 10 and the stepper motor 14 to the computer 22 through the data line 21. Start the control program on the computer and initialize the equipment: The rotary motor 4 drives the annular rotator 6 to reset to the initial position, ensuring that the probe is at the specified starting position of the test tube 23. The electric horizontal guide 10 drives the slider 24 to move to the starting position of the horizontal guide, so that the initial position of the probe remains consistent along the axial direction of the test tube. The stepper motor 14 adjusts the probe 15 to a position away from the surface of the test tube 23 to ensure the initial accuracy of the vertical measurement process.

[0027] Start the computer control program, drive the stepper motor 14 to drive the probe 15 to gradually approach the wall of the test tube 23. When the probe 15 contacts the wall of the test tube 23, the circuit is turned on, and the ammeter 19 shows that the current reaches the maximum value. This state is used to calibrate the starting contact position of the probe 15. The stepper motor 14 is controlled by the computer 22 to drive the probe 15 to gradually move away from the wall at a set step length. In this process, due to the presence of the liquid film, the resistance between the probe 15 and the wall of the test tube 23 gradually increases, and the reading of the ammeter 19 gradually decreases. When the probe 15 moves to a certain distance and the reading of the ammeter 19 suddenly drops to zero, it means that the probe 15 is completely separated from the liquid film and the circuit is open. At this time, the computer 22 records the moving distance of the stepper motor 14, which is the thickness value of the liquid film.

Claims

1. A method and device for measuring the thickness of a surface liquid film, comprising an annular holder (1), a threaded through hole (2), a test tube avoidance hole (3), a rotating motor (4), a rotating motor holder (5), an annular rotator (6), an annular guide rail (7), a slide rail stabilizer (8), an annular gear (9), an electric horizontal guide rail (10), an electric horizontal guide rail holder (11), a stepper motor holder (12), a probe avoidance hole (13), a stepper motor (14), a probe (15), a bearing (16), a wire (17), a power supply (18), an ammeter (19), a switch (20), a data line (21), a computer (22), a test tube (23), and a slider (24). It is characterized in that The annular fixer (1) is provided with a threaded through hole (2), the test tube (23) passes through the test tube avoidance hole (3), the bolt is connected to the threaded through hole (2) and fixes the test tube (23) to the annular fixer (1); the annular fixer (1) and the rotating motor fixer (5) are provided with threaded holes, the rotating motor fixer (5) and the annular fixer (1) are connected by bolts and fix the rotating motor (4) to the annular fixer (1); the slide rail stabilizer (8) is provided with two pairs of pulleys and through holes, the slide rail stabilizer (8) is connected by a slide The wheel is connected to the annular guide rail (7), and the slide rail stabilizer (8) can slide on the annular guide rail (7); the annular guide rail (7) and the annular gear (9) are provided with screw holes, and the annular guide rail (7) and the annular gear (9) are connected by bolts; the annular rotator (6) is provided with a shaft and a groove, and the groove of the annular rotator (6) and the annular gear (9) are both provided with threaded holes, and the annular rotator (6) and the annular gear (9) are connected by bolts; the annular fixer (1) is provided with a bearing hole, and the annular rotator (6) is connected to the annular gear (9) through a bearing (16). The electric horizontal guide rail (10) is connected to a circular holder (1); the shaft of the rotating motor (4) is in transmission connection with the ring gear (9), and the rotating motor (4) drives the circular rotator (6) to rotate; the electric horizontal guide rail holder (11) and the circular rotator (6) are both provided with screw holes, the electric horizontal guide rail holder (11) and the circular rotator (6) are connected with the electric horizontal guide rail (10) and the circular rotator (6) by bolts; the electric horizontal guide rail (10) is provided with a slider (24), and the slider (24) and the stepping motor holder (12) are both provided with screw holes. The stepper motor holder (12) and the slider (24) are connected by bolts to fix the stepper motor (14) and the slider (24), and the stepper motor (14) passes through the probe avoidance hole (13); the probe (15) and the test tube (23) are respectively connected to the positive and negative electrodes of the power supply (18) through a wire (17), and an ammeter (19) and a circuit switch (20) are provided on the wire (17); the stepper motor (14), the rotary motor (4) and the electric horizontal guide rail (10) are connected to a computer (22) through a data line (21).

2. A measuring device for measuring the thickness of a surface liquid film according to claim 1, characterized in that The rotary motor (4) drives the annular rotator (6) to rotate in the circumferential direction, thereby adjusting the circumferential positions of the electric horizontal guide rail (10) and the probe (15).

3. A measuring device for measuring the thickness of a surface liquid film according to claim 1, characterized in that The slide rail stabilizer (8) is provided with a through hole, and the through hole is used to allow the shaft of the rotating motor (4) to pass through, so as to stabilize the rotating motor (4) and limit its swing.

4. A measuring device for measuring the thickness of a surface liquid film according to claim 1, characterized in that The electric horizontal guide rail (10) is provided with a slider (24), and the slider (24) drives the stepping motor holder (12) to move in the horizontal direction, so as to achieve measurement of the probe (15) at different horizontal positions.

5. A testing method using a measuring device for measuring the thickness of a surface liquid film as claimed in claim 1, characterized in that: The method comprises the following steps: S1: fixing the device to the test tube (23), ensuring that the annular fixture (1) is stably connected to the test tube (23); the computer (22) is connected to the rotating motor (4), the electric horizontal guide rail (10) and the stepping motor (14) through the data line (21); initializing each motor to the zero position; the probe (15) is connected to the positive and negative poles of the power supply (18); the ammeter (19) and the switch (20) form a monitoring circuit to ensure that the circuit works normally; S2: controlling the rotating motor (4) through the computer (22) to drive the annular gear (9) and the annular rotator (6) to rotate; the slide rail stabilizer (8) cooperates with the annular guide rail (7) through the pulley to ensure that the rotating motion is smooth and accurate; the probe (15) always points to the required measuring position during the rotation process; according to the set measuring point, the computer controls the rotating motor to stop automatically to achieve accurate positioning of the circumferential angle; S3: After the rotation positioning is completed, the computer (22) controls the electric horizontal guide rail (10) to move the slider (24) in the horizontal direction, and the slider (24) drives the stepper motor holder (12) and the stepper motor (14) to move horizontally, so as to realize the precise movement of the probe (15) in the horizontal position; S4: After the circumferential and horizontal positioning is completed, the computer (22) controls the stepper motor (14) to drive the probe (15) to gradually approach the surface of the test tube (23) in the vertical direction. When the probe contacts the liquid film, the circuit is turned on and the ammeter (19) displays the current value; as the stepper motor (14) gradually moves the probe away from the tube wall, the resistance increases and the current gradually decreases. When the probe is completely separated from the liquid film, the ammeter (19) displays the current as zero. At this time, the computer records the total displacement of the stepper motor, which is the thickness value of the liquid film.

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