Visualized low-temperature fluid static evaporation test system

Abstract

A visual low-temperature fluid static evaporation test system includes: an experimental chamber and a heat exchanger sealed in an outer cover, and a mass flowmeter located outside the outer cover. Multiple thermometers are installed in the experimental chamber, the bottom of which is connected to the heat exchanger through a bellows, and the top of which is connected to the mass flowmeter and the heat exchanger in sequence to discharge evaporated low-temperature fluid. The present invention is a test system that can completely and accurately test the static evaporation process of low-temperature fluid while meeting visualization and refinement requirements.

Description

Technical Field

[0001] The present invention relates to a technology in the field of low-temperature fluid phase change, in particular to a visual low-temperature fluid static evaporation test system. Background Art

[0002] Existing devices make it difficult to measure the thermophysical parameters near the interface of statically evaporating cryogenic fluids. Therefore, there is no experimental scheme that can perform precise measurement and visual observation of the static evaporation process of cryogenic fluids. This has greatly hindered the development of relevant theories about cryogenic fluids and the optimization of related technologies. Summary of the Invention

[0003] In response to the defects of the existing technology that are unable to accurately control and adjust the position of the gas-liquid interface of the cryogenic fluid and unable to measure the temperature in the extremely thin area near the phase interface with a high response rate, the present invention proposes a visual low-temperature fluid static evaporation test system. The test system can completely and accurately test the static evaporation process of the cryogenic fluid while meeting the requirements of visualization and refinement.

[0004] The present invention is achieved through the following technical solutions:

[0005] The present invention includes: an experimental chamber and a heat exchanger sealed in an outer cover, and a mass flow meter located outside the outer cover, wherein: a plurality of thermometers are arranged in the experimental chamber, the bottom of which is connected to the heat exchanger through a bellows, and the top of which is connected to the mass flow meter and the heat exchanger in sequence to discharge evaporated low-temperature fluid.

[0006] The heat exchanger liquefies all cryogenic fluid vapor from the air inlet pipe and forms cryogenic fluid droplets. The cryogenic fluid droplets flow out from the outlet at the bottom of the heat exchanger under the action of gravity and return to the experimental chamber through the connecting bellows.

[0007] The discharged evaporated cryogenic fluid flows through the exhaust pipe, mass flow meter, air inlet pipe, heat exchanger and bellows and then returns to the experimental chamber. The circulation of the cryogenic fluid in the system ensures that the observed cryogenic fluid gas-liquid interface remains stable in position, making the measured temperature field more accurate.

[0008] A constant temperature cold screen connected to a heat exchanger is provided outside the experimental chamber to form a thermal boundary of the test system to achieve continuous temperature changes. The constant temperature cold screen and the heat exchanger are overlapped by a thermal conductive copper strip; the low temperature fluid in the heat exchanger and the thermostat is used to provide cooling for the constant temperature cold screen.

[0009] The constant temperature cold screen is provided with an electric heating film, which provides heat to the constant temperature cold screen by heating it through electricity.

[0010] The heat exchanger is provided with a thermostat, which is filled with low-temperature fluid during testing.

[0011] The multiple thermometers include: three thermometers arranged at different heights in the experimental chamber, the first thermometer is arranged at the top of the experimental chamber, for detecting the temperature of the low-temperature gas in the experimental chamber; the second thermometer is arranged in the middle of the experimental chamber, for detecting the temperature of the low-temperature gas-liquid interface in the experimental chamber; the third thermometer is arranged at the bottom of the experimental chamber, for detecting the temperature of the low-temperature liquid in the experimental chamber.

[0012] The diameter of the measuring probes of the first thermometer, the second thermometer and the third thermometer is less than 50 microns, and the interference of the measurement on the local temperature and speed is minimized by using an E-type thermocouple with a wire diameter of 50 microns.

[0013] The sealing arrangement is achieved by an end cover flange arranged on the top of the outer cover and a vacuum port arranged on the outer cover.

[0014] The outer cover is provided with transparent windows, wherein a first window is positioned on the wall of the sealed chamber near the experimental chamber, and a second window is positioned opposite the first window. The outer side of the first window is flush with the outer cover. The constant temperature cold shield has a hole in the optical path formed by the first and second windows. The shape of the hole is the projection of the experimental chamber onto the constant temperature cold shield along the optical path. A high-magnification telecentric lens is positioned outside the first window, and a surface light source is positioned outside the second window.

[0015] Technical Effects

[0016] Compared with the prior art, the technical effects of the present invention include:

[0017] 1. Without any mechanical moving parts, the position of the evaporation interface in the experimental chamber can be precisely controlled and kept stable, and the temperature and pressure in the sub-millimeter thin layer near the interface of the stably evaporated low-temperature fluid can be measured.

[0018] 2. The use of high-magnification telecentric lenses and surface light sources to achieve visual observation can meet the need to obtain position information near the interface when a static low-temperature fluid evaporates.

[0019] 3. Use a constant temperature cold screen to effectively prevent radiation heat leakage from the environment to the experimental chamber. The adjustable temperature of the constant temperature cold screen can meet the experimental requirements of the evaporation characteristics of low-temperature fluids under different ambient temperatures.

[0020] 4. It can meet the experimental requirements of static evaporation processes of various low-temperature fluids such as liquid helium, liquid hydrogen, liquid nitrogen, liquid oxygen, and liquid methane.

[0021] 5. Each pipeline connection adopts a detachable connection method, and the heat exchanger and thermostat adopt a detachable fixing method, which can facilitate the replacement of pipelines or components according to test requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of the present invention.

[0023] In the figure: 1 air supply valve, 2 pressure sensor, 3 mass flow meter, 4 reflux valve, 5 thermostat, 6 heat exchanger, 7 thermal copper tape, 8 thermometer lead, 9 thermometer through-chamber, 10 lower part of the experimental chamber, 11 connecting bellows, 12 second window, 13 first window, 14 third thermometer, 15 second thermometer, 16 first thermometer, 17 experimental chamber, 18 constant temperature cold shield, 19 vacuum port, 20 outer cover, 21 closed chamber end cover flange, 22 air supply pipe, 23 exhaust pipe, 24 air inlet pipe. DETAILED DESCRIPTION

[0024] like Figure 1 As shown, this embodiment relates to a visualized low-temperature fluid static evaporation test system, including: an experimental chamber 17 and a heat exchanger 6 sealed in an outer cover 20, and a mass flowmeter 3 located outside the outer cover 20, wherein: a plurality of thermometers are arranged in the experimental chamber, the bottom of which is connected to the heat exchanger 6 through a bellows 11, and the top of which is connected to the mass flowmeter 3 and the heat exchanger 6 in sequence to discharge the evaporated low-temperature fluid.

[0025] The heat exchanger 6 liquefies all the cryogenic fluid vapor from the air inlet pipe 24 and forms cryogenic fluid droplets. The cryogenic fluid droplets flow out from the outlet at the bottom of the heat exchanger 6 under the action of gravity and return to the experimental chamber 17 through the connecting bellows 11.

[0026] A heater is provided on the outside of the heat exchanger 6 .

[0027] A constant temperature cold shield 18 connected to the heat exchanger 6 is provided outside the experimental chamber to form the thermal boundary of the test system to achieve continuous temperature change. The constant temperature cold shield 18 and the heat exchanger 6 are overlapped by a thermal conductive copper belt; the low temperature fluid in the heat exchanger 6 and the thermostat 5 is used to provide cooling for the constant temperature cold shield.

[0028] The constant temperature cold screen 8 is provided with an electric heating film, which provides heat to the constant temperature cold screen by heating it with electricity.

[0029] The heat exchanger 6 is provided with a thermostat 5, which is built-in with a low-temperature fluid during testing, that is, a fluid with a boiling point below -150°C under standard atmospheric pressure, including but not limited to: liquid hydrogen, liquid oxygen, liquid methane, liquid helium, liquid neon, and liquid nitrogen.

[0030] The evaporated cryogenic fluid flows through exhaust pipe 23, mass flowmeter 3, intake pipe 24, heat exchanger 6, and connecting bellows 11 before returning to experimental chamber 17. The circulation of the cryogenic fluid in the system ensures that the observed cryogenic fluid gas-liquid interface remains stable, making the measured temperature field more accurate.

[0031] The multiple thermometers include: three thermometers 13, 14, and 15 arranged at different heights in the experimental chamber, the first thermometer 16 is arranged at the top of the experimental chamber 17, for detecting the temperature of the low-temperature gas in the experimental chamber 17; the second thermometer 15 is arranged in the middle of the experimental chamber 17, for detecting the temperature of the low-temperature gas-liquid interface in the experimental chamber 17; the third thermometer 14 is arranged at the bottom of the experimental chamber 17, for detecting the temperature of the low-temperature liquid in the experimental chamber 17.

[0032] The diameter of the measuring probes of the first thermometer 16 , the second thermometer 15 , and the third thermometer 14 is less than 50 microns, and the interference of the measurement on the local temperature and speed is minimized by using E-type thermocouples with a wire diameter of 50 microns.

[0033] An air supply valve 1 is provided between the mass flow meter 3 and the experimental chamber.

[0034] The experimental chamber 17 comprises an upper metal flange and a lower glass chamber.

[0035] The sealing arrangement is achieved by an end cap flange 21 provided at the top of the outer cover 20 and a vacuum port 19 provided on the outer cover 20. A vacuum control valve is connected to the vacuum port 19. The sealed chamber can be dynamically evacuated to a pressure of 0 to 0.01 Pa by a molecular pump unit. In this embodiment, the pressure of the sealed chamber is 0.01 Pa.

[0036] The outer cover 20 is provided with transparent windows 12 and 13. The first window 13 is located on the wall of the sealed chamber near the experimental chamber 17, and the second window 12 is located opposite the first window 13. The outer side of the first window 13 is flush with the outer cover 20. A constant temperature cold shield 18 has a hole in the optical path formed by the first and second windows 13, 12. The shape of the hole is the projection of the experimental chamber 17 onto the constant temperature cold shield 18 along the optical path. A high-magnification telecentric lens is located outside the first window 13, and a surface light source is located outside the second window 12.

[0037] In this embodiment, the visible area formed by the first window 13 and the second window 12 can fully observe the lower glass area of the experimental chamber 17.

[0038] The vacuum port 19 and the vacuum control valve (not shown in the figure) on the outer cover 20 are provided on the outer cover 20, and the vacuum control valve is connected to the vacuum port 19. The closed chamber can be dynamically vacuumed by the molecular pump unit.

[0039] The constant temperature cold shield 18 and heat exchanger 6 are surrounded by multi-layer insulation material, which includes one or more of the following materials: constant density vacuum multi-layer, variable density vacuum multi-layer. The multi-layer insulation material is formed by alternating at least 20 layers of metal foil and spacer material.

[0040] The test process for testing the mass flow rate of the static evaporation process of the cryogenic fluid in this embodiment includes:

[0041] ① Connect the experimental chamber 17 to the connecting bellows 11 through a quick-change joint, and connect the connecting bellows 11 to the heat exchanger 6 through a quick-change joint.

[0042] ② Place various types of insulation materials around the heat exchanger 6, connecting bellows 11, and thermostat 18. After the coating is complete, thermometers are placed outside the heat exchanger 6 and thermostat 18 to monitor the temperature. Once installed, these components are connected to the thermostat 5 and placed together in a sealed chamber.

[0043] ③ Use the molecular pump unit to pump the vacuum degree in the closed chamber to the level of 0.01Pa.

[0044] ④ Fill the thermostat 5 with low-temperature fluid to cool the system until the constant temperature cold shield 18, the experimental chamber 17, and the heat exchanger 6 reach the predetermined value, and then enter the test phase.

[0045] ⑤ During the test, low-temperature fluid is regularly added to the thermostat 5 to ensure that the temperature on the heat exchanger 6 is constant. The liquid level in the experimental chamber 17 is increased or decreased by adding or discharging gas through the air supply valve 1. When the readings of the three thermometers in the experimental chamber 17 fluctuate by less than 0.2K within 2 minutes, it means that the test conditions have stabilized. At this time, the average temperature value within 30 seconds is taken as the basis, as the temperature measurement value of the current position, the average value of the mass flowmeter 3 reading within 30 seconds is taken as the mass flow rate at the current position, and the average value of the pressure sensor 2 reading within 30 seconds is taken as the pressure data at the current position. After the measurement is completed, the gas-liquid interface position is changed, and another gas-liquid interface position is measured. The temperature of the heat exchanger 6 is adjusted by the heater, and the pressure in the experimental chamber 17 is adjusted.

[0046] Through specific experiments, operating the aforementioned device at a pressure of 100 kPa using liquid oxygen as the working fluid, we obtained experimental data: the temperature distribution within 3 mm of the liquid oxygen interface and the corresponding evaporation rate data. The temperatures on both sides of the gas-liquid interface show a downward trend as they approach the interface, reaching their lowest value at the interface. At the gas-liquid interface, the gas-side temperature is 0.5-0.8 K higher than the liquid-side temperature.

[0047] Compared with the existing technology, the position control accuracy of the low-temperature fluid gas-liquid interface of this device is improved to 5 microns, and the spatial resolution of temperature measurement near the gas-liquid interface is improved to 50 microns.

[0048] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principles and purpose of the present invention. The scope of protection of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. All implementation schemes within its scope shall be subject to the constraints of the present invention.

Claims

1. A visual low-temperature fluid static evaporation test system, characterized in that: include: An experimental chamber and a heat exchanger are sealed in the outer cover, and a mass flow meter is located outside the outer cover, wherein: a plurality of thermometers are provided in the experimental chamber, the bottom of which is connected to the heat exchanger through a bellows, and the top of which is connected to the mass flow meter and the heat exchanger in sequence to discharge evaporated cryogenic fluid; The heat exchanger liquefies all cryogenic fluid vapor from the air inlet pipe and forms cryogenic fluid droplets. The cryogenic fluid droplets flow out from the outlet at the bottom of the heat exchanger under the action of gravity and return to the experimental chamber through the connecting bellows. The discharged evaporated cryogenic fluid flows through the exhaust pipe, mass flow meter, air inlet pipe, heat exchanger and bellows and then returns to the experimental chamber. The circulation of the cryogenic fluid in the system ensures that the observed cryogenic fluid gas-liquid interface remains stable, making the measured temperature field more accurate. A constant temperature cold screen connected to a heat exchanger is provided outside the experimental chamber to form a thermal boundary of the test system to achieve continuous temperature changes. The constant temperature cold screen and the heat exchanger are overlapped by a thermal conductive copper strip; the low temperature fluid in the heat exchanger and the thermostat is used to provide cooling for the constant temperature cold screen.

2. The visual low-temperature fluid static evaporation test system according to claim 1 is characterized in that: The constant temperature cold screen is provided with an electric heating film, which provides heat to the constant temperature cold screen by heating through electricity.

3. The visual low-temperature fluid static evaporation test system according to claim 1 is characterized in that: The heat exchanger is provided with a thermostat, which is filled with low-temperature fluid during testing.

4. The visual low-temperature fluid static evaporation test system according to claim 1 is characterized in that: The multiple thermometers include: three thermometers arranged at different heights in the experimental chamber, the first thermometer is arranged at the top of the experimental chamber, for detecting the temperature of the low-temperature gas in the experimental chamber; the second thermometer is arranged in the middle of the experimental chamber, for detecting the temperature of the low-temperature gas-liquid interface in the experimental chamber; the third thermometer is arranged at the bottom of the experimental chamber, for detecting the temperature of the low-temperature liquid in the experimental chamber.

5. The visual low-temperature fluid static evaporation test system according to claim 4 is characterized in that: The diameter of the measuring probes of the first thermometer, the second thermometer and the third thermometer is less than 50 microns, and the interference of the measurement on the local temperature and speed is minimized by using an E-type thermocouple with a wire diameter of 50 microns.

6. The visual low-temperature fluid static evaporation test system according to claim 1 is characterized in that: The sealing arrangement is achieved by an end cover flange arranged on the top of the outer cover and a vacuum port arranged on the outer cover.

7. The visual low-temperature fluid static evaporation test system according to claim 1 is characterized in that: The outer cover is provided with two transparent windows, wherein: the first window is arranged on the wall of the closed chamber close to the experimental chamber, and the second window is arranged on the opposite side of the first window; the outer side of the first window is flush with the outer cover.

8. The visual low-temperature fluid static evaporation test system according to claim 1 or 2, characterized in that: The constant temperature cold screen has a hole on the light path formed along the first window and the second window. The hole is a projection of the experimental chamber on the constant temperature cold screen along the light path.

9. The visual low-temperature fluid static evaporation test system according to claim 7 is characterized in that: A high-power telecentric lens is provided outside the first viewing window, and a surface light source is provided outside the second viewing window.

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