CN1187581C - Low temperature level meter - Google Patents

Abstract

The present invention discloses a low temperature liquid level meter, which is provided with a hollow heat conduction pipe, two flanges, a plate pack, and an acoustic resonance pipe in sequence, wherein the plate pack is fixed by two fixed metal sheets. One end of the acoustic resonance pipe is closed, and the other end of the acoustic resonance pipe is connected with the flanges. One end of the heat conduction pipe is connected with the flanges, and the other end of the heat conduction pipe is open. The present invention makes use of the heat acoustic effect principle to judge the position of a liquid level through sound, which brings convenience to operation. The present invention can precisely determine the height of the liquid level according to the critical point of the generation and the disappearance of the sound and according to the principle that once the heat conduction pipe leaves the liquid level of low temperature liquid, the heat conduction pipe can emit sound. After the heat conduction pipe is inserted in the liquid level, the sound immediately disappears. The method for measuring the liquid level overcomes the splashing danger of the low temperature liquid in the traditional measurement method, and simultaneously, can highly precisely determine the position of the liquid level. What is more important, the present invention has the advantages of simple structure, convenient operation, no moving components, no failure because of clamping, no difficulty of dynamic sealing and long service life, tracks the height of the liquid level in time, and correctly reflects the height of the liquid level.

Description

Liquid level gauge for low temperature

Technical field

The present invention relates to a kind of liquid level gauge for low temperature.

Background technology

At cryogenic gas liquefaction and gas separation field, it is particularly important that the low temperature liquid level gauging seems.Wherein, a kind of is to determine to be stored in the container or the quantity of liquid in the storage tank by the height of the liquid level in measuring vessel, the storage tank; Another kind is by measurement liquid level parameter, and controls this parameter maintenance certain numerical value, keeps balance to guarantee production run.Present cryogenic liquid level instrument has differential pressure type liquid level meter (Han Consulting's inferior type low temperature liquid level meter, electronic gentle moving differential level gauge); Electric capacity liquid level meter; Tape float gauge; Radioactive level gauge; Ultrasonic level meter; Carbon resistance liquid level meter; Utilize metal or alloy to become superconduction depthometer of superconductor etc. at low temperatures in addition.But the liquid level gauge for low temperature of also not utilizing the thermoacoustic effect principle to make.And comprehensive, more than several liquid level meter complex structures, be difficult for processing, cost height, brought trouble for common activity in production.Usually cryogenic liquid is surveyed the liquid level meter and is adopted the less bar of coefficient of heat conductivity (as plastic bar etc.) to insert the cryogenic liquid tank, rapidly it is taken out then, calculates the height of cryogenic liquid liquid level by the aerial frosting length of bar.Though this method is simple, has certain danger.Comparatively accurately need the insulated shaft of inserting in the liquid is extracted rapidly in order to measure, can cause cryogenic liquid to spill like this, and because the littler material of coefficient of heat conductivity, also have certain thermal conductivity, the temperature difference that adds cryogenic liquid and insulated shaft is bigger, heat-transfer rate will obviously be accelerated, thus on the insulated shaft frosting position actual be not the position of cryogenic liquid liquid level temperature.

Summary of the invention

The purpose of this invention is to provide a kind of liquid level gauge for low temperature.

It has hollow heat conducting successively, two flanges, plate is folded, the acoustic resonance pipe, plate is folded by two fixing metal spacers, acoustic resonance Guan Yiduan sealing, the other end is connected with flange, heat pipe one end is connected with flange, other end opening, the material of said heat pipe harmony resonatron is a silver, red copper, aluminium, the external diameter of heat pipe is 15～100mm, wall thickness is 1.5～15mm, long is 144mm～14.4m, acoustic resonance external diameter of pipe 15～100mm, wall thickness 1.5～15mm, length is 131mm～13.1m, being shaped as that plate is folded is plate, the porosint type, pipe type, silk screen type and needle bar type, the small aperture on plate is folded are 2～5 times of heat penetration, the folded stainless steel that adopts of silk screen template, brass; Folded plastics, resin, the pottery of adopting of plate, porosint template.The folded diameter of plate is 30～150mm, and thickness is 16～55mm, evenly is provided with diameter with one heart and is 223～500 of the apertures of 1.5～5mm on plate is folded.

The present invention utilizes the thermoacoustic effect principle, judge the position of liquid level by the sound, bring certain convenience to operation, and it is the liquid level that in a single day leaves cryogenic liquid according to heat pipe, will sound, insert behind the liquid level sound mechanism that just disappears again, just can determine the height of liquid level according to the critical point of the generation of sound and disappearance accurately at once.The method of this measurement liquid level has not only overcome the danger that the cryogenic liquid of traditional measurement method can splash, and can determine the position at liquid level place simultaneously again highly accurately.The more important thing is that the present invention is simple in structure, easy to make, movement-less part does not have the difficulty of blocking malfunctioning and motive seal, can use for a long time, and the liquid level height also can in time be followed the tracks of, and correctly reflects.

Description of drawings

Fig. 1 is the liquid level gauge for low temperature structural representation;

Fig. 2 is a liquid level gauge for low temperature plate stack structure enlarged drawing.

Embodiment

Theoretically, thermoacoustic effect is meant compressible fluid working substance with thermal expansivity, and have between the solid actuating medium of big thermal capacity and coefficient of heat conductivity, because the sound oscillation of the relative solid of fluid and generation thermal interaction, and the time equal thermodynamic energy graded effect that causes.

For general standing wave, the temperature fluctuation in the sound field just causes that by the adiabatic compression and the adiabatic expansion of vibration air mass amplitude is minimum, and people are difficult to notice.If add enough short flat board (second medium), because the thermo-contact of second medium and pressure wave causes the fluid in the heat penetration to produce the hot-fluid along the acoustic propagation direction, can there be a thermograde along dull and stereotyped direction, when this thermograde is enough to overcome the critical temperature gradient of dull and stereotyped decision own, will shows as hot-fluid and flow to low-temperature end and convert the part heat to merit output from temperature end.This shows that will realize that heat drives sound oscillation, its necessary condition has 2 points: the one, second medium be arranged, the 2nd, enough thermogrades be arranged.If sounding then needs mobile gas in addition.

In the hot sound pipe of standing wave standing-wave sound field is arranged, it is the straight tube of a vertical end sealing of placing, and is built-in with plastic plate folded (perhaps wire gauze).Plate is folded generally to be made up of cluster glass pore, can play the result who strengthens thermoacoustic effect.According to the Rayleigh criterion, the vertical pipe of placing " when a bit cooling off, has the convection current draught therein.The first-harmonic acoustic pressure is node at two ends, and the center is an antinode, particle velocity antithesis, two ends are antinode and the center is a node, in four/one-period before acoustic pressure reaches greatly, all are to flow to the center in the particle velocity of the upper half and following half.Identical with the mean air flow direction and strengthen in the particle velocity of following half, plate is folded from airborne draw heat increase.Owing between transfer of heat and the acoustic pressure suitable phase differential is arranged,, and forms driving force so transfer of heat helps the acoustic pressure vibration just." as can be known, acoustic pressure drives and both depended on particle velocity, concerns acoustic pressure again.For first-harmonic, pipe interior nodes and antinode all can not vibrate in the driving tube.And node is between the antinode, and promptly 1/4th pipe range places are best drive points on the mouth of pipe.Be the optimum position of the folded effect of plate herein.Interval between the general heat sound plate is approximately twice or more hot boundary layer thickness (thermal break-through distance).

The present invention adopts following basic hot part spare to realize.These parts respectively have different functions.Finished thermal energy transfer in liquid level gauge for low temperature, the mutual conversion of heat energy and acoustic energy, functions such as transportation.These basic parts are:

1) the heat pipe heat pipe is a heat exchanger components.When the liquid level meter had just inserted cryogenic liquid, it mainly carried out heat interchange by modes such as heat conduction, convection current and gas in the pipe, and the gas in the pipe is reached or as much as possible near the tube wall temperature.In addition, it must make the gas in the pipe be the laminar motion state as far as possible.The structure of heat pipe can adopt good solid circles tubulose (as the metal tube) structure of heat conductivility, also can adopt the metal tube bank by the little caliber of good heat conductivity to constitute.The caliber of metal tube or metal tube bank does not have strict regulation, generally decides by concrete condition.The solid dielectric of heat pipe should have good thermal conductivity, thereby makes temperature on the tube wall as much as possible near low temperature.The temperature of liquid, the temperature on the tube wall is low more, and the cooldown rate of gas is fast more in the pipe, simultaneously, also more near the cryogenic liquid temperature, so that the gas in the pipe is as far as possible near waiting temperature state.

2) the folded heat sound of heat sound plate plate is folded is the most key parts of liquid level gauge for low temperature, is the spot of heat sound transfer process.Plate is folded have plate, porosint type, tubule type (comprising circular hole and square), multiple structures such as silk screen type and needle bar type.It seems that according to result of study it is most effective that the needle bar template is folded, and plate taking second place, yet though the needle bar structure has higher plate to fold efficient, its complex manufacturing technology generally is difficult to obtain actual application.Dull and stereotyped template is folded easy to make, and has higher efficient.But, dull and stereotyped template is folded requires machining precision higher.Usually adopt approximate plate helical coil tubular structure.Because the convenience aspect making and installation, silk screen type and porosint type heat sound plate are folded and have been obtained increasing application.Plate laminate materials commonly used is also varied, and total selection principle is the foundation that helps the folded middle thermograde of plate.If select the words of silk screen type or porosint, general heat conductivilitys such as stainless copper, the brass material preferably of selecting, like this because the thermal contact resistance between silk screen or the porosint is bigger, and the heat conductivility of metal material itself is better, make the plate after making fold the axial thermal conductivity ability, and radially the capacity of heat transmission is stronger.Not only help the foundation of the folded middle thermograde of plate, and, help the raising of heat sound transformation efficiency; The plate of other patterns is folded, in order to obtain the thermograde that comparatively favourable heat sound transforms, generally uses the material of heat conductivility difference, as plastics, pottery, resin etc.

Can see that from the ultimate principle of thermoacoustics thermoacoustic effect only betides in the about heat penetration scope of anomaly plate, excessive if the folded spacing of plate obtains, inevitable some area does not participate in heat sound pump heat, influences the folded efficient of plate.If it is too small that the folded spacing of plate obtains, then the viscous loss meeting increases, contrast exist multiple different view, the proposed pitch that has get 2～4 times heat penetration value ( ${\mathrm{\δ}}_k=\sqrt{2K/{\mathrm{\ω\ρ}}_m\mathrm{Cp}}$ Be the heat penetration of gas, wherein K is the thermal conductivity of gas, and Cp is a specific heat at constant pressure, and ω is an angular frequency, ρ _mBe average density).The folded spacing of heat sound plate of then thinking that has is that 2.5～5 times of heat penetration values more meet the theoretical hypothesis of linear heat sound.In general, 2～5 times of heat penetrations are the proper values in plate folded spacing ground.In addition, another folded important physical dimension of heat sound plate is the folded length of plate.Under the certain situation of cold and hot end temperature, the folded length of plate directly affects the thermograde at the folded two ends of plate.If the folded length of plate is too short, then the rely gas-solid interface area that exists of thermoacoustic effect is too little, and folded oversize when plate, also can cause along the thermograde on the folded length of plate and reduce, and conversion efficiency reduces.In addition, the folded length of plate also can influence the relation between the phase place.Thereby can exist a best plate to fold length.But there is not the efficient transition problem owing to survey the liquid level meter.Thereby as long as satisfy can be in plate be folded thermograde above the needed critical gradient of sounding.

3) the resonatron resonatron is one section outside wall surface and the good solid pipeline of extraneous heat conduction.It has two main effects, and first effect is the coupling of length in system by pipeline, produces half-wave resonance or nearly resonance sound field in total system.The two ends acoustical conductivity of hot acoustic resonance pipe is than the zone of preferably crossing over high acoustical conductivity ratio and hanging down the acoustical conductivity ratio.Second effect, it should have good heat-conducting.Like this, can make resonatron play the effect of temperature end heat interchanger, so that the gas in the pipe is in or near the normal temperature state.In addition, it also plays and is used to connect the two ends that are in same warm area forming the feedback regulation loop of sound wave, or is used for the natural frequency of regulating system, and the cross sectional shape of resonatron can be varied.But its acoustic streaming road equivalent yardstick should greater than or much larger than the heat penetration of local fluid, to avoid the hot-fluid loss from the temperature end to the low-temperature end owing to solid thermal conduction and thermoacoustic effect generation, but can not be too big so that the empty volume of total system is too big, energy density is too low.Resonatron can adopt straight tube along the longitudinal direction, also can adopt from the varying cross-section duct of low-temperature end to the temperature end expansion.As tubaeform continuous expansion, or the expansion of trapezoidal staged.The outside wall surface of resonatron should with the external world's abundant thermo-contact of trying one's best so that the gas in the pipe reaches the normal temperature state, the foundation that can help the thermograde of heat sound plate in folded like this with keep.The openend of resonatron can be provided with (also can not being provided with) laminarization element, makes flowing in the resonatron approach laminar flow as far as possible, reduces or elimination Turbulence Mixed and loss.

The liquid level gauge for low temperature of indication of the present invention is to be made of above several basic acoustics and hot part spare.Selection that these several parts are different and combination can form the low temperature liquidometer of different structure characteristics.The different selections and the combination of indication here all needs to satisfy such condition, and promptly a cryogenic liquid liquidometer comprises above several basic element of character at least.At the heat conduction pipe end, heat pipe absorbs cold from the cryogenic liquid liquid level, thus the wall temperature that makes heat pipe near or reach the temperature of cryogenic liquid.By the heat conduction between tube wall and gas, the gas in modes such as convection current even radiation will be managed also is cooled to the temperature near cryogenic liquid.Cryogenic gas forms certain thermograde in that plate is folded, when the thermograde in plate is folded produces required critical gradient greater than thermoacoustic effect, begins some heat energy and is converted into acoustic energy, if the air current flow in this moment pipe will be sent acoustic disturbance.A fixing sound vibration frequency is coordinated in acoustic disturbance in resonatron, and feedback amplification rapidly, and will sound this moment.Wherein whether gas flow is the essential condition that can decision sound in the pipe.When the cryogenic liquid level instrument inserted liquid level, the air-flow in the heat pipe produced other Laminar Flow hardly except random flowing such as convection current.Thereby can not sounding.And heat pipe is when leaving liquid because extraneous gas pours in the pipe, thereby sounding at once, be exactly by sounding whether the height of liquid level is determined in critical point accurately.

Adopt above-mentioned design, position that can point-device definite cryogenic liquid liquid level, and the present invention is simple in structure, the operation is also comparatively easy, and it has not only overcome the danger of traditional definite cryogenic liquid liquid level position method, and inaccuracy, and can be applied to different occasions widely.

Liquid level gauge for low temperature has folded 2, the acoustic resonance pipe 3 of hollow heat conducting 1, two flanges 4, plate successively, plate is folded fixing by two fixing metal pads 7, the sealing of acoustic resonance pipe 3 one ends, and the other end is connected with flange, heat pipe 1 one ends are connected with flange, other end opening.

The material of said heat pipe 1 harmony resonatron 3 is silver, red copper, aluminium, and the external diameter of heat pipe is 15～100mm, and wall thickness is 1.5～15mm, and long is 144mm～14.4m.Acoustic resonance external diameter of pipe 15～100mm, wall thickness 1.5～15mm, length is 131m～13.1m.

Being shaped as of plate folded 2 is plate, porosint type, pipe type, silk screen type and needle bar type, and the small aperture on plate is folded is 2～5 times of heat penetration, and the silk screen template is folded, adopts stainless steel, brass; Plate, porosint template is folded, and adopts plastics, resin, pottery; The folded diameter of plate is 30～150mm, and thickness is 16～55mm, evenly is provided with diameter with one heart and is 223～500 of the apertures of 1.5～5mm on plate is folded.

The material of metallic gasket 7 is selected silver, red copper, aluminium, and its size is folded consistent with plate with shape.

Two flanges adopt bolt, nut 5 to connect, and nut is provided with plastic washer 6, and packing ring adopts fluoroplastic.

Liquid level gauge for low temperature operation instruction of the present invention:

This liquid level gauge for low temperature is slowly inserted in the larger storage tank of storing cryogenic fluids, pipe shaft vertically downward, heat pipe 1 openend gos deep into below the cryogenic liquid liquid level, another section acoustic resonance pipe 3 is held in the hand, the temperature remains within the normal range.After keeping a period of time, can find that pipe shaft has the sense of shaking strongly, the vertical-lift pipe shaft is up to the sound that sends " drone ... ".Write down the present position by the external world with reference to scale this moment, compares with liquid level meter size again, can determine the position at cryogenic liquid liquid level place.

Liquid level gauge for low temperature principle of work of the present invention is as follows:

Cryogenic liquid will be surveyed the cooling of liquid level meter heat pipe, and the acoustic resonance pipe of the other end is under the normal temperature, Cryogenic air is just set up certain thermograde in plate is folded like this, when this thermograde meets or exceeds the critical temperature gradient, will be converted into acoustic energy by some heat energy.In addition, the cryogenic gas of uniform temperature and solid dielectric effect sounding still need an extra condition: the air-flow in the hot sound pipe must flow.If the gas in the pipe is static fully, then can not sound.This liquid level gauge for low temperature utilizes this principle accurately to measure the cryogenic liquid liquid level exactly.When the mouth of pipe of survey liquid level meter places cryogenic liquid, because cryogenic liquid stops up the mouth of pipe.Though can form certain thermograde, because gas does not flow in the pipe, thereby can not sounding.Slowly promote the survey liquid level meter that is inserted in the liquid, when the mouth of pipe exposed liquid level just, the fluid in the pipe flowed at once.Send simultaneously " drone " the sound.

Claims (3)

1, a kind of liquid level gauge for low temperature, it is characterized in that: it has hollow heat conducting (1) successively, two flanges (4), plate is folded (2), acoustic resonance pipe (3), plate is folded fixing by two fixing metal pads (7), the sealing of acoustic resonance pipe (3) one ends, the other end is connected with flange, heat pipe (1) one end is connected with flange, other end opening, the material of said heat pipe (1) harmony resonatron (3) is a silver, red copper, aluminium, the external diameter of heat pipe is 15～100mm, and wall thickness is 1.5～15mm, and long is 144mm～14.4m, acoustic resonance external diameter of pipe 15～100mm, wall thickness 1.5～15mm, length is 131mm～13.1m, being shaped as of plate folded (2) is plate, the porosint type, pipe type, silk screen type and needle bar type, small aperture on plate is folded is 2～5 times of heat penetration, the folded stainless steel that adopts of silk screen template, brass; Folded plastics, resin, the pottery of adopting of plate, porosint template.The folded diameter of plate is 30～150mm, and thickness is 16～55mm, evenly is provided with diameter with one heart and is 223～500 of the apertures of 1.5～5mm on plate is folded.

2, a kind of liquid level gauge for low temperature according to claim 1 is characterized in that: the material of said metallic gasket (7) is selected silver, red copper, aluminium, and its size is folded consistent with plate with shape.

3, a kind of liquid level gauge for low temperature according to claim 1 is characterized in that: said two flanges adopt bolt, nut (5) to fix, and nut is provided with plastic washer (6), and packing ring adopts fluoroplastic.

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