SU1509671A1 - Method of determining surface tension of liquid - Google Patents

Abstract

The invention relates to monitoring devices for physico-chemical parameters at the interface of a liquid-gas and a liquid-liquid interface and can be widely used to determine surface tension by the drop volume method in the chemical and petrochemical industry. The purpose of the invention is to improve the accuracy of determination of surface tension by reducing errors associated with the uncertainty of the volume of a drop of liquid. A device containing a syringe for the test liquid, calibrated by the outer diameter of the capillary, a micrometer head, an electric drive, a photoelectronic system for detecting the moment of detachment of a drop from the end of the capillary, additionally includes a stabilized voltage block that is functionally interconnected, and a controlled generator of drop-down exponential signals. voltage, repeater, adder, power amplifier, one-shot, pulse counter, timer, and setting devices of initial and final values of voltage Nij power control winding of the electric actuator, providing an exponential decrease in liquid feed rate in a capillary that provides the minimum drop volume variation rate at the time of separation and reduces the volume of droplets scatter values. 1 il.

Description

 The invention relates to a measuring and control technique, in particular, to measuring devices in the field of physicochemical studies of surface properties at the liquid-liquid or liquid-gas interface, and can be used in the chemical and petroleum industry; in the development of mixtures for intensifying oil production .

The aim of the invention is to improve the accuracy of determination by reducing the errors associated with the uncertainty of the volume of a drop of liquid.

The drawing shows a diagram of the proposed device.

The device contains a capillary tube calibrated with the outer diameter (for example, 5-12 mm), the inner volume of which is in communication with the syringe 2 for

315

fluid flow, the transducer 3 of the rotational movement into translational, mechanically connected with the micrometer head 4 and the electric drive 5 with an adjustable rotational speed. Capillary 1 is located in vessel 6 for receiving the separated droplets. Near the end of the capillary 1 in the vessel 6 there are placed the light source 7 and the photocell 8, which are included in the launch circuit of the one-shot 9, the output of which is connected to the pulse counter 10. The output of pulse counter 10 is connected to the control input of timer 11. At the output of the device power supply 12, the initial 13 and final 14 power supplies of the control winding of the electric drive 5 are set as variable resistances. The output voltage of the setters is controlled by a switch 15 with a voltmeter 16. The output of the setting device 14 is connected to the first input of the adder 17, and to the second input of the adder 17 through the switching element 18 and the repeater 19 are connected to the output of the setting device 13 and the output of the generator 20 of a dropping exponential voltage The output of the adder 17 is connected to the control to the winding of the electric drive 5 through the power amplifier 21. At the output of the power supply unit 12, a relay 22 is installed, the contacts of which are blocked by a pushbutton switch 23. The contacts of the relay 24 are connected in series with the relay 22. The output of the single-vibrator 9 is connected to a relay 25, the contacts of which are included in the starting circuit of the generator 20 and blocked by button 26, Timer II is equipped with a button 27 to reset the readings. At the output of the adder 17 is set toggle 28.

The device works as follows.

The syringe 2 is filled with the liquid under test and the capillary p 1 is installed and, after squeezing out a few drops, the syringe is installed in the device so that the syringe stem 2 through the transducer 3 is in spring-loaded contact with the micrometer head 4 and the capillary is in the vessel 6 with the test liquid in a strictly vertical position, In the vicinity of the end face

five

0

five

67

0

Q

five

0

14. ,

pill ra 1 install source 7

light and photocell .8.

In the initial state, the device controls should be in this state: the toggle switch 28 is turned off, the switching element 18 is in the lower position, the switch 15 is in an arbitrary position, the contacts of the relay 22 and 25 3 are open, the contact of the relay 24 is in the closed state, the windings relays 22, 25 and 24 are de-energized. The power supply unit 12 is turned on, with a stabilized voltage of ± 15 V appearing at its output, which is used to power all the units of the device, to power the windings of the electric drive 5, to power the light source 7 and to power the relay windings. The button of the button switch 23 is pressed briefly, the relay 22 is triggered, which, by its contact, is self-blocking. As a result, the setting power of 1.3 and 14 is supplied with a supply voltage of 15 V, using the setting device 14, the switch 15 and the voltmeter 16 set the final power supply voltage of the electric drive 5, t, e. such that it has the lowest rotational speed of its output shaft and, correspondingly. Generally, the smallest flow of liquid to the drop that forms at the end of the cap 1ll, for the DPR-0.25 motor, this voltage is equal to -3 V. With the aid of the setting device 13, the switch 15 and the voltmeter 16 set any constant voltage, for example, 4 B, which in total with the voltage previously set by the setting point 14, should be one of the points of the operating characteristic of the electric drive 5,.

The switch 28 is turned on, as a result of which the indicated voltages, one directly and one through the repeater 19, are fed to the input of the adder 17. As a result, there will be a voltage at its output, which is equal to the sum of the input voltages, for example 7 V. the voltage through the power amplifier 21 is supplied to the control winding of the electric drive 5, as a result of which its output shaft rotates at a constant frequency. This leads to the fact that the stem of the syringe 2 begins to move downwards and a droplet forms at the end of the cap. At the moment when the weight of the drop becomes slightly larger than the surface forces holding it on the outer edge, the drop separates from

51509671

the end and to the input of the one-shot 9 from the photoel, cement 8 receives a signal that causes the output of the single-vibrator 9 to have a short pulse and a short-time operation of the relay 25. At the same time, the pulse counter 10 starts, which starts the timer 11 for counting the time ( in seconds). Relay 24 does not work. As soon as the second pulse from the photo cell 8 is received as a result of the separation of the second

ten

ml to pr mete ve vi ni n

droplets formed by a constant flow of fluid into it, a pulse reappears at the output of the pulse counter 10, which stops timer 11 and switches on relay 24, last opens its contact, de-energizes relay 22, which closes the voltage supply circuit to the setpoint devices 13 and 14, as a result of which the actuator 5 stops.

Then using dependencies

KlUj.-Ii TP ()

(ABOUT

calculate the initial value of the supply voltage and the winding of the electro25 according to the falling exponential law decreases the flow of the test liquid in the resulting drop at the end of the capillary 1. Through T T the first drop separates, the transfer 5, when implementing further JQ when the exponential exponential law changes the flow of the test liquid to the resulting drop, where U is the previously set voltage at the unit setting point 13 (B); time measured by timer 11 and

the main supply of fluid into it, As a result, the one-shot 9 and short-circuit relay 25, which by its contact restores

, ci "r, t.",. and - the voltage U at the output of the generator 20. the expenditure on the formation of one drop. Simultaneously, the counts are turned on when the test liquid is continuously fed into it; T is the specified (required) time for the formation of one drop with the falling exponential

The pulse of 10 pulses, which starts the timer 11. The second drops that form will again occur when the ex-40 exposes, the potential flow of the test liquid into the resulting drop and its formation again triggers the corresponding circuit elements. However, the impulse to stop the timer 11

the flow of liquid in a drop; K (recommended K 4); T is the time constant of the falling exponential. The law of change in the supply of a liquid to a drop (). about

Dependence (1) is obtained by solving the following equation:

f

T, j and

Tj, / K

dt.

(2)

compiled on the basis of the assumption j that the volume of the separated droplet at a constant flow of liquid, is equal to the volume of the separated kappi with a falling exponential flow of liquid into the resulting drop.

TO

4, and

 4 V

(one)

Vj 10.87 V.

After calculating the voltage U u

the magat button 27, as a result of which the relay 24 de-energizes and closes its contact in the circuit of relay 22. In addition, the display of the timer 11 is reset, the toggle switch 28 is opened, the switching element 18 is set to the upper position and the short button is pressed 23 Using the setpoint 13, the switch 15 and the voltmeter 16 set the calculated value of the voltage U; j. By changing the parameters of the generator 20, the value T is set. Za5 temporarily press button 26 and turn on the toggle switch 28. At the same time, the voltages U and U are simultaneously applied to the input of the adder 17, which, summing and amplifying in power,

One kind of voltage is applied to the winding of the electric drive 5. As a result, the output shaft of the electric drive first rotates at an exponentially decreasing speed. At the same time

5, according to the falling exponential law, the flow of the test liquid is reduced to the droplet formed at the end of the capillary 1. Through T T, the first droplet formed, which is formed when the exponent drops down U at the generator output 20. At the same time, the counting

The pulse of 10 pulses, which starts the timer 11. The second drop that forms is again triggered by the exponential flow of the test liquid into the resulting drop, and its formation again triggers the corresponding circuit elements. However, the impulse to stop the timer 11

and the relay 25 is not triggered, since the counter 10 is set to count ten drops. At the moment when the ten drops drop apart from the first one that starts the system into operation,

a pulse appears from the output of counter 10, which stops timer II and turns on relay 25. As a result of this, as in the previously described scenario, the drive 5 stops.

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The calculation of the surface tension value of the test point at its interface with a saturated gas is carried out using the dependence

. ., / - & p-g

(3)

where G is the surface tension, N / m; f (O ASlSCr / vy) - 0.7694 (r / V) + 0.9267; V is the volume of one drop, calculated on the basis of the readings of the micrometric head 4 and the previously determined characteristics of the syringe 2, m;

the difference between the densities of the test liquid in the drop and the surrounding / m;

its acceleration, the acceleration of the earth’s t

outer radius of the capillary.

m,

Claims (1)

Invention Formula A device for determining the surface tension of a fluid, containing a calibrated outer diameter to 15 20 Element located near the end of the capillary and connected to a pulse counter, characterized in that, in order to increase the accuracy of determination by reducing errors associated with the uncertainty of the volume of a drop of liquid, the initial power units are connected to the electrical circuit by the power supply unit and the control winding of the electric rotation drive. and the final voltage, the exponential voltage of the exponential voltage and the adder, while the output of the power supply unit is connected to the inputs of the initial and final voltage settings, the output beyond Occupancy final voltage coupled to a first input of an adder, vkod setpoint initial voltage and exponential generator output pull-down voltage through kommutatsionnpCh element connected to the second input of the adder whose output is connected to the control winding ru is a capillary, the internal volume of which is 25 electric drives of rotation, and in It communicates with a syringe for the test fluid, equipped with a micrometer head, an electric drive of the micrometer head, the control winding of which is connected to a 30 power supply unit, and a photoelectronic droplet counting system containing photoalss R the electrical circuit between the photocell and the pulse counter is connected in series with a single-vibration and electrical relay, a pair of contacts of which are included in the starting circuit of the falling exponential voltage generator,