CN102590033A - Device for measuring flow characteristics and electrokinetic parameters of ionic liquid solution micropipe - Google Patents

Abstract

The invention discloses a device for measuring the flow characteristics and the electrokinetic parameters of an ionic liquid solution micropipe. The device comprises a gas pressure supply system, a liquid storage tank, a test section and a data acquisition system, wherein the gas pressure supply system comprises a high-pressure nitrogen cylinder, a precision pressure-reducing valve and the like; one end of a plastic two-way joint in the test section is connected with a micro pipeline, the other end is connected with a buffer cavity, a differential pressure sensor and a Pt100 temperature measuring probe are connected below the buffer cavity, one pair of measuring electrodes are introduced from the side face and are connected with a locked phase amplifier and a signal generator, a shut-off valve and an outlet valve are respectively arranged on fluid inlet and outlet pipelines, and an online conductivity sensor is connected on a header pipe. Not only can the degree of influence of electric viscosity on the flow characteristics of fluid be judged, but also the wall zeta potential and the specific surface conductivity can be obtained. The device has the characteristics of stability, reliability and easiness and convenience for operation, data acquisition can be completed through a computer, and long-distance control can be realized.

Description

The measurement mechanism that contains ionic liquid solution canalicular flow characteristic and moving electrical quantity thereof

Technical field

The present invention relates to measure the field of fluid flow characteristics and moving electrical quantity thereof, relate in particular to a kind of measurement mechanism that contains ionic liquid solution canalicular flow characteristic and moving electrical quantity thereof.

Background technology

The interface electrokinetic phenomenon influences the transmittance process of fluid in the microtubule, and when solid material contacted with polar solvent or electrolyte solution, solid material surface can produce surface charge; The liquid that influence is contiguous forms electrostatic double layer, produces the surface zeta potential electromotive force; Electric charge redistribution during the pressure-driven fluid in the solution forms electrokinetic potential, thereby convection cell produces electrostatic force, influences fluid motion; Macro manifestations is that stickiness increases, and resistance to flow increases, i.e. electro-viscous effect.

Ionic liquid is made up of the yin, yang ion; The organic fuse salt that under room temperature or situation, is in a liquid state near room temperature; Have the trend that replaces VOC, mobile in microtubule of its WS or organic solution has singularity, has electro-viscous effect.At present domestic does not still have a report that relevant measurement contains ionic liquid solution device of flow characteristics and moving electrical quantity thereof in microtubule.Therefore; Develop the experimental provision that a kind of measurement contains ionic liquid solution flow characteristics and moving electrical quantity thereof in microtubule, thereby the flow characteristics of fully realizing under the microscale is significant in application such as microreactor design, little heat interchanger exploitations in the future for ionic liquid.

Summary of the invention

The object of the invention is to provide a kind of measurement mechanism that contains ionic liquid solution canalicular flow characteristic and moving electrical quantity thereof.

The measurement mechanism that contains ionic liquid solution canalicular flow characteristic and moving electrical quantity thereof comprises gas voltage supply system, test section and data acquisition system (DAS); Gas voltage supply system comprises high-pressure nitrogen bottle, reduction valve, first filtrator, second filtrator, accurate reduction valve, stop valve, retaining valve, quick-opening valve, the 3rd filtrator, coil pipe, fluid reservoir, calibration cell, gas-holder; High-pressure nitrogen bottle, reduction valve, first filtrator, second filtrator, accurate reduction valve, gas-holder, stop valve, retaining valve link to each other in order; Be provided with coil pipe in the fluid reservoir; The coil pipe two ends link to each other with the import and export of low temperature thermostat bath respectively, and the fluid reservoir bottom links to each other with the 3rd filtrator, quick-opening valve one end in order; Test section and data acquisition system (DAS) comprise Pt100 temperature probe, cushion chamber, first outlet valve, online conductivity sensor, first stop valve, three-way connection, first branch road, second branch road, second stop valve, glass bushing heat interchanger, microtubule, second outlet valve, electronic balance, potential electrode, differential pressure pick-up, signal generator, lock-in amplifier, robot calculator, data collecting card, two pass joints, viton gasket, securing member; Be provided with microtubule in the glass bushing heat interchanger, the microtubule two ends connect first end and link to each other with two two respectively, fix through viton gasket, securing member; The other end of two two pass joints links to each other with two cushion chamber one ends respectively, is respectively equipped with potential electrode in two cushion chambers, and two potential electrode link to each other with signal generator, lock-in amplifier respectively; Two cushion chamber lower ends are respectively equipped with differential pressure pick-up, Pt100 temperature probe, and link to each other with data collecting card, robot calculator respectively; One cushion chamber upper end links to each other with first outlet valve, first stop valve, one end, and another cushion chamber upper end links to each other with second outlet valve, second stop valve, one end; The quick-opening valve other end links to each other with online conductivity sensor, three-way connection in order, tells two branch roads from three-way connection, and first branch road links to each other with first stop valve, one end, and second branch road links to each other with the other end of second stop valve.

Said cushion chamber is the organic glass cavity, and is right cylinder.Said microtubule places the glass bushing heat interchanger.

The present invention not only can measure fluid pressure drop of flow in microtubule; Can also measure owing to there is the electrokinetic potential that produces in electrostatic double layer; Thereby can judge that electroviscosity to containing the influence degree of ionic liquid solution flow characteristics, can also obtain wall zeta electromotive force and specific surface conductivity.Through connecting online conductivity meter, not only can measure conductivity of fluid, can also whether clean up by signal piping.The gas voltage supply system that is adopted have voltage supply steadily, be easy to regulate, the characteristics of handling safety.Circuit design is become the loop form, and the valve of increasing export, thereby can change the flow direction of fluid, make things convenient for duplicate measurements and pipeline to clean through the by-pass valve control switch.Measure temperature, pressure drop and conductivity device and be connected to computing machine, can show in real time on computers and image data, can realize remote control by lead.

Description of drawings

Fig. 1 contains the synoptic diagram of the measurement mechanism of ionic liquid solution canalicular flow characteristic and moving electrical quantity thereof;

Fig. 2 test section is along the sectional view of pipeline direction;

Among the figure, high-pressure nitrogen bottle 1, reduction valve 2, first filtrator 3, second filtrator 4, accurate reduction valve 5, stop valve 6, retaining valve 7, quick-opening valve 8, the 3rd filtrator 9, coil pipe 10, fluid reservoir 11, calibration cell 12, gas-holder 13, Pt100 temperature probe 14, cushion chamber 15, first outlet valve 16, online conductivity sensor 17, first stop valve 18, first branch road 19, three-way connection 20, second branch road 21, second stop valve 22, glass bushing heat interchanger 23, microtubule 24, second outlet valve 25, electronic balance 26, potential electrode 27, differential pressure pick-up 28, signal generator 29, lock-in amplifier 30, robot calculator 31, data collecting card 32, two pass joints 33, viton gasket 34, securing member 35.

Embodiment

As shown in the figure, the measurement mechanism that contains ionic liquid solution canalicular flow characteristic and moving electrical quantity thereof comprises gas voltage supply system, fluid reservoir, test section and data acquisition system (DAS); Gas voltage supply system comprises high-pressure nitrogen bottle 1, reduction valve 2, first filtrator 3, second filtrator 4, accurate reduction valve 5, stop valve 6, retaining valve 7, quick-opening valve 8, the 3rd filtrator 9, coil pipe 10, fluid reservoir 11, calibration cell 12, gas-holder 13; High-pressure nitrogen bottle 1, reduction valve 2, first filtrator 3, second filtrator 4, accurate reduction valve 5, gas-holder 13, stop valve 6, retaining valve 7 link to each other in order; Be provided with coil pipe 10 in the fluid reservoir 11; Coil pipe 10 two ends link to each other with the import and export of low temperature thermostat bath 12 respectively, and fluid reservoir 11 bottoms link to each other with the 3rd filtrator 9, quick-opening valve 8 one ends in order; Test section and data acquisition system (DAS) comprise Pt100 temperature probe 14; Cushion chamber 15; First outlet valve 16; Online conductivity sensor 17; First stop valve 18; Three-way connection 19; First branch road 20; Second branch road 21; Second stop valve 22; Glass bushing heat interchanger 23; Microtubule 24; Second outlet valve 25; Electronic balance 26; Potential electrode 27; Differential pressure pick-up 28; Signal generator 29; Lock-in amplifier 30; Robot calculator 31; Data collecting card 32; Two pass joints 33; Viton gasket 34; Securing member 35; Be provided with microtubule 24 in the glass bushing heat interchanger 23, microtubule 24 two ends link to each other with two two pass joint 33 1 ends respectively, fix through viton gasket 34, securing member 35; The other end of two two pass joints 33 links to each other with two cushion chamber 15 1 ends respectively, is respectively equipped with potential electrode 27, two potential electrode 27 in two cushion chambers 15 and links to each other with signal generator 29, lock-in amplifier 30 respectively; Two cushion chamber 15 lower ends are respectively equipped with differential pressure pick-up 28, Pt100 temperature probe 14, and link to each other with data collecting card 32, robot calculator 31 respectively; One cushion chamber, 15 upper ends link to each other with first outlet valve 16, first stop valve, 18 1 ends, and another cushion chamber 15 upper ends link to each other with second outlet valve 25, second stop valve, 22 1 ends; Quick-opening valve 8 other ends link to each other with online conductivity sensor 17, three-way connection 20 in order, tell two branch roads from three-way connection 20, and first branch road 19 links to each other with first stop valve, 18 1 ends, and second branch road 21 links to each other with the other end of second stop valve 22.

Said flow line is the loop, and outlet and outlet valve are set in said flow circuits, thereby can change the flow direction of fluid through the by-pass valve control switch, makes things convenient for the cleaning of duplicate measurements and pipeline.Said microchannel is fixed through plastics two pass joints, viton gasket, securing member, is convenient to change the microtubule of different tube diameters.The two ends, microchannel all are in the inboard of pressure tap and keep the 1-2mm distance with pressure tap, and the pressure at pressure tap place is more stable when making stability of flow.Said cushion chamber is nonconducting organic glass cavity, can reduce the interference that the environment additional electric field is measured electrokinetic potential, and it is designed to right cylinder, can avoid bubble to pile up at the wall place and causes resistance to flow to change.Said measurement potential device is connected to lock-in amplifier, avoids noise effect, and measurement temperature, pressure drop, conductivity device are connected to computing machine through data collecting card, can show in real time on computers and image data.Said glass sock tubular type heat interchanger can guarantee to avoid causing owing to the heat interchange with environment the difference of fluid inlet and outlet temperature.Said gas voltage supply system realizes pressure coarse adjustment, fine tuning through reduction valve, accurate reduction valve; Said gas-holder can make flow of nitrogen gas more steady, thereby pressure stable more is provided; Said retaining valve can prevent liquid to reflux; Said filtrator is used for removing the impurity of nitrogen, fluid to be measured, prevents to get into microchannel and results in blockage.

Measurement contains the experimental provision of ionic liquid solution canalicular flow characteristic and moving electrical quantity thereof, and its data processing method is following:

Usually flow characteristics is also referred to as drooping characteristic, and that record in the experiment is the mass rate Q in the microchannel unit interval, kg/s, and then the average velocity u of microchannel inner fluid is:

$u=\frac{4Q}{\mathrm{\ρ\π}{d}^2}---\left(1\right)$

The computing formula of reynolds number Re is in the microtubule:

$\mathrm{Re}=\frac{\mathrm{\ρdu}}{\mathrm{\μ}}---\left(2\right)$

ρ is a fluid density in the formula, kg/m ³U is a fluid average velocity, m/s; D is circular microchannel diameter, m; μ is the kinetic viscosity of fluid, Pas.

According to classical theory, the conventional yardstick interior laminar flow of pipe down satisfies Poiseuille stream for abundant development, the frictional resistance constant, and promptly Poisuille value fRe can be by computes, and promptly Hagen-Poisuille separates.

The pressure differential deltap P that records in the experiment _TotaL comprises three parts: pressure differential deltap P, microchannel inflow point runner that fluid flows through microchannel dwindle the local pressure differential deltap P that causes suddenly _cAnd the local pressure differential deltap P that causes of exit runner sudden enlargement _e

$\mathrm{\Δ}{P}_c=K_c\frac{\mathrm{\ρ}{u}^2}{2}---\left(4\right)$

$\mathrm{\Δ}{P}_e=K_e\frac{\mathrm{\ρ}{u}^2}{2}---\left(5\right)$

In the formula, K _c, K _eBe respectively and dwindle resistance coefficient, sudden enlargement resistance coefficient suddenly.Can calculate by following formula respectively.

K _c＝0.5(1-A ₁/A ₂) (6)

K _e＝(1-A ₁/A ₂) ² (7)

In the formula, A ₁, A ₂Be respectively the cross-sectional area of microchannel, the cross-sectional area of the cushion chamber that links to each other with microchannel.Therefore, pressure drop Δ P can be tried to achieve by following formula.

ΔP＝ΔP _total-ΔP _c-ΔP _e (8)

The Δ P that records through experiment _TotaL calculates Δ P, finds the Δ P that it is more mobile than classics _TheoreticalBigger than normal, consider and possibly increase, so verify according to following theoretical model owing to electroviscosity causes the resistance of fluid.

Theoretical according to static, the electric density ρ in wall electrostatic potential ψ and the solution in the unit volume _eThe available cylindrical coordinates of distribution in zero dimension Poisson-Boltzmann equation describe

$\frac{1}{r}\frac{d}{\mathrm{dr}}\left(r\frac{\mathrm{d\ψ}\left(r\right)}{\mathrm{dr}}\right)=K^2\sinh \mathrm{\ψ}\left(r\right)---\left(9\right)$

$K=\mathrm{\δ}\·R=\sqrt{\frac{8\mathrm{\π}{n}_{\∞}{z}^2{e}^2}{{\mathrm{\ϵ}}_r{\mathrm{\ϵ}}_0{k}_{b}T}R}---\left(10\right)$

Boundary condition does

$r=0,\frac{\mathrm{d\ψ}\left(r\right)}{\mathrm{dr}}=0;$ $r=1,\mathrm{\ψ}\left(1\right)=\frac{\mathrm{e\ζ}}{k_{b}T}$

In the formula, ε _rRelative dielectric constant for solution; ε ₀Be permittivity of vacuum, C/V; n _∞Be respectively main body ion concentration and quantivalency with z; E is the elementary charge number, C; k _bBe Boltzmann constant, J/K; T is an absolute temperature, K; ζ is a wall zeta electromotive force, V; δ is the Debye-Huckle parameter, δ ^-1Then be electrostatic double layer thickness.

Thus it is clear that, know that the zeta electromotive force of wall just can be obtained ψ (r), thereby obtain the electric density ρ in the unit volume _e, it is the function of ψ (r), promptly

${\mathrm{\ρ}}_e=-2\mathrm{ze}{n}_{\∞}\sinh \left(\frac{\mathrm{ze\ψ}\left(r\right)}{k_{b}T}\right)---\left(11\right)$

Develop stream fully fully for incompressible, stable state, its flow equation does

$\mathrm{\μ}\frac{1}{r}\frac{\∂}{\text{\∂r}}\left(r\frac{\∂\stackrel{\‾}{u}}{\∂r}\right)=\frac{\∂P}{\∂z}+F---\left(12\right)$

$F=-{\mathrm{\ρ}}_e{\stackrel{\‾}{E}}_z---\left(13\right)$

Know that by formula (12), formula (13) body force item F is for considering near the electrostatic force that is caused by net charge in the wall electrostatic double layer zone.

is the clean electric field of this moment, can try to achieve

by the charge balance of solution, the conductivity and the specific surface conductivity of solution

It is thus clear that, find the solution electrostatic field equation and flow equation, need know the zeta electromotive force and the specific surface conductivity of wall, the two is important moving electrical quantity, one of purpose that also is this patent belongs to.Therefore, electrokinetic potential, pressure drop and the conductivity of same a kind of fluid under different tube diameters through recording can return out parameter to be asked by formula (14), formula (15), i.e. the zeta electromotive force of wall and specific surface conductivity.

$\frac{E_s}{\mathrm{\ΔP}}=\frac{{\mathrm{\ϵ}}_0{\mathrm{\ϵ}}_r\mathrm{\ζ}}{\mathrm{\μ}({\mathrm{\λ}}_0+{\mathrm{\λ}}_s/R)}{\mathrm{\φ}}_P---\left(14\right)$

${\mathrm{\φ}}_P=\frac{1-\frac{\cosh K-1}{K\sinh K}}{1+\frac{\mathrm{\δ}({\mathrm{\ϵ}}_0{\mathrm{\ϵ}}_r{)}^2{\mathrm{\ζ}}^2}{2\mathrm{R\μ}({\mathrm{\λ}}_0+{\mathrm{\λ}}_s/R)}}---\left(15\right)$

In the formula, E _sThe electrokinetic potential of fluid in the microchannel that records for experiment, V; λ ₀Be conductivity of fluid, S/m; λ _sBe specific surface conductivity, S; R is the radius of circular microchannel, m; φ _PBe modifying factor.

Know K=R/ δ by formula (10) ^-1Be the ratio of microchannel size and electrostatic double layer thickness; Claim moving electric diameter again; Big I through this moving electric diameter judges whether the influence of electro-viscous effect can be ignored, and the pressure drop of the actual increase that records is compared with produce the body force item owing to electro-viscous effect, just can the proof theory model and analyze the amplitude that causes the fluid flow resistance increase owing to electroviscosity.

The course of work of the present invention is following:

(1) before the experiment beginning, earlier pressure transducer, thermal resistance, conductivity meter etc. are proofreaied and correct.Simultaneously whole pipe system is thoroughly cleaned, method of operating is following: use earlier washed with de-ionized water, behind the cleaning multipass, clean with fluid to be measured.Because conductivity is very sensitive to the slight variation of ion concentration, therefore stablize and when matching, can think that whole pipe system cleans up with the actual conductivity value of fluid to be measured when conductivity value reaches, carry out next step measurement then.The fine pipe of microtubule, especially stainless steel is owing to leave grease in process; Can not impact experimental result if do not remove; Therefore before carrying out flowing experiment, need carry out oil removal treatment, method of operating is following: place 80-90 ℃ heat alkali liquid, hot water to soak respectively 15 minutes the fine pipe of stainless steel, concussion was cleaned about 10 minutes in supersonic wave cleaning machine then; Be placed on again in the ethanol and soaked 20 minutes, ethanol in the microtubule is cleaned up with deionized water.At last, it is for use to be placed on 110 ℃ drying in oven.

(2) temperature of setting calibration cell, stable a period of time makes that the fluid temperature in the fluid reservoir is constant in a certain temperature.Open nitrogen cylinder; Regulate oxygen reduction valve 2, make the outlet pressure of nitrogen remain on certain value, nitrogen flows through two filtrators; Let nitrogen be full of accurate reduction valve pipeline before; Open the quick-opening valve 8 between fluid reservoir and the test section again, control to the required pressure of experiment, promote the fluid smooth flow in the fluid reservoir then through regulating accurate reduction valve 5.Open first stop valve 18, second outlet valve 25, close second stop valve 22, first outlet valve 16, make flow of liquid cross test section, collect the fluid that flows out bypass duct in the certain hour then, weigh, obtain the mass rate of fluid with the precise electronic balance.Because the bubble that is present in the microchannel has remarkable influence to liquid mobile, can cause flowing law to change and cause mobile instability, therefore in measuring process, it is particularly important to get rid of influence of air bubbles.Usually, when fluid inlet and outlet temperature, test section pressure stability, can think that fluid flows and reach stable state; Gather and stablize back 10 minutes temperature, pressure, potential value, conductivity value this moment, and second stop valve 22, first outlet valve 16 are opened in horizontal survey 3 times then; Close first stop valve 18, second outlet valve 25; Promptly change direction of flow, the mean value of measuring for six times is got in duplicate measurements in a manner described under identical measuring condition at last.When various flows to measurement finish after, the pressure-regulating valve of adjustments of gas voltage supply system carries out identical caliber by the aforesaid operations method again, the measurement of different flow.When changing different fluids to be measured, as stated above whole pipe system is thoroughly cleaned.

(3) rerum natura of fluid is tabled look-up through the mean value of the out temperature of the fluid that records in the experiment and is drawn in the formula; Through changing the microchannel of different tube diameters, can obtain wall zeta electromotive force and specific surface conductivity λ in conjunction with the conductivity of the pressure drop that records, electrokinetic potential and liquid _s, the two is important moving electrical quantity, can be used for finding the solution electrostatic field equation and flow equation.Through drawing Δ P/L-Re graph of a relation; Compare with classical flow model; The amplitude that simultaneously resistance is increased is compared with the body force item that brings owing to electro-viscous effect, just can analyze intuitively owing to electroviscosity causes pressure-driven fluid resistance to flow increasing degree.

Claims (3)

1. a measurement mechanism that contains ionic liquid solution canalicular flow characteristic and moving electrical quantity thereof is characterized in that comprising gas voltage supply system, test section and data acquisition system (DAS); Gas voltage supply system comprises high-pressure nitrogen bottle (1), reduction valve (2), first filtrator (3), second filtrator (4), accurate reduction valve (5), stop valve (6), retaining valve (7), quick-opening valve (8), the 3rd filtrator (9), coil pipe (10), fluid reservoir (11), low temperature thermostat bath (12), gas-holder (13); High-pressure nitrogen bottle (1), reduction valve (2), first filtrator (3), second filtrator (4), accurate reduction valve (5), gas-holder (13), stop valve (6), retaining valve (7) link to each other in order; Be provided with coil pipe (10) in the fluid reservoir (11); Coil pipe (10) two ends link to each other with the import and export of calibration cell (12) respectively, and fluid reservoir (11) bottom links to each other with the 3rd filtrator (9), quick-opening valve (8) one ends in order; Test section and data acquisition system (DAS) comprise Pt100 temperature probe (14); Cushion chamber (15); First outlet valve (16); Online conductivity sensor (17); First stop valve (18); First branch road (19); Three-way connection (20); Second branch road (21); Second stop valve (22); Glass bushing heat interchanger (23); Microtubule (24); Second outlet valve (25); Electronic balance (26); Potential electrode (27); Differential pressure pick-up (28); Signal generator (29); Lock-in amplifier (30); Robot calculator (31); Data collecting card (32); Two pass joints (33); Viton gasket (34); Securing member (35); Be provided with microtubule (24) in the glass bushing heat interchanger (23), microtubule (24) two ends link to each other with two two pass joints (33) one ends respectively, fix through viton gasket (34), securing member (35); The other end of two two pass joints (33) links to each other with two cushion chambers (15) one ends respectively; Be respectively equipped with potential electrode (27) in two cushion chambers (15), two potential electrode (27) link to each other with signal generator (29), lock-in amplifier (30) respectively; Two cushion chambers (15) lower end is respectively equipped with differential pressure pick-up (28), Pt100 temperature probe (14), and links to each other with data collecting card (32), robot calculator (31) respectively; One cushion chamber (15) upper end links to each other with first outlet valve (16), first stop valve (18) one ends, and another cushion chamber (15) upper end links to each other with second outlet valve (25), second stop valve (22) one ends; Quick-opening valve (8) other end links to each other with online conductivity sensor (17), three-way connection (20) in order; Tell two branch roads from three-way connection (20); First branch road (19) links to each other with first stop valve (18) one ends, and second branch road (21) links to each other with the other end of second stop valve (22).

2. a kind of measurement mechanism that contains ionic liquid solution canalicular flow characteristic and moving electrical quantity thereof according to claim 1 is characterized in that said cushion chamber (15) is the organic glass cavity, and is right cylinder.

3. a kind of measurement mechanism that contains ionic liquid solution canalicular flow characteristic and moving electrical quantity thereof according to claim 1 is characterized in that said microtubule (24) places glass bushing heat interchanger (23).

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