SU759914A1 - Device for determining gas transfer coefficients - Google Patents

Description

The invention relates to a test technique, and more specifically to devices for determining the coefficients of the transfer of gases through a liquid.

A device is known that makes it possible to determine the diffusion coefficients of gases in liquids, consisting of a diffusion cell divided by a vertical partition [1].

However, the measurement of the diffusion coefficient in this device is difficult due to the difficulty in determining the time at which diffusion begins. Known diffusion cell does not allow to determine the coefficients of solubility and permeability of gases in liquids.

The closest technical solution is a device for determining gas transfer coefficients through polymer film materials, based on a gas chromatograph determining the amount and composition of gas passing through a film consisting of a diffusion cell placed in a thermostat with a heating element, the walls of which have a coolant cavity made of two chambers located one under the other, the upper of which is equipped with a thermocouple, and the volume of the lower chamber is connected through

2

dosing crane with gas chromatograph system [2].

The installation does not allow to determine the coefficients of gas transfer through liquids, 5 for the placement of which is diffusion

the cell has no capacity.

The aim of the invention is to expand the functionality of the device.

To do this, between the upper and lower chambers of the diffusion cell, a liquid tank is installed, made in the form of a cylinder, bounded by polymeric membranes, having two overlapping openings in the cylindrical part of the body, 15 which contain sealing elements at the ends, which are rubber rings

cell equipped with a thermocouple.

FIG. 1 shows a diagram of the proposed device; in fig. 2 - general view

diffusion cell in section.

The device consists of a chromatograph 1 connected to a diffusion cell 2 located in a thermostat 3 with heating elements 4 and a cavity 5 for liquid nitrogen that comes from a Dewar 6. Temperature is controlled by an automatic self-recording potentiometer 7. The diffusion cell 2 contains 30 top 8 and bottom 9 cameras with compaction 759914

 3

10 elements are used to seal the diffusion cell 2. Four screw clamps 11. Gas cylinder 12 is designed to supply carrier gas to chromatograph 1, and cylinder 13 is for test gas, which is fed through tube 14 to upper chamber 8 of diffusion cell 2 Sealing the input thermocouple 15 in the top 8 and bottom 9 chambers of the diffusion cell 2 is carried out by compound 16.

Between the upper 8 and lower 9 chambers of the diffusion cell 2 a container 17 is installed for the test liquid 18, limited by polymeric membranes 19, containing sealing elements 20 on the ends.

Tubes 21 with taps 22 serve to fill the tank 17 with the test liquid 18 and remove air from it. The volume of the lower chamber 9 through the tube 13 is included in the gas system of the chromatograph 1.

The device works as follows.

The container 17 is clamped with screw clamps 11 in the diffusion cell 2 between the upper 8 and lower 9 chambers. The test liquid 18 is poured with open taps 22 through the tube 20 into the container 17. The taps 22 are closed.

Thermocouple junctions 15 are related to polymer polymeric membranes 19.

The volume of the lower chamber 9 of the diffusion cell 2 is washed with a carrier gas. In the upper chamber 8 serves the test gas from the cylinder 13. The sampling of the test gas passing through the polymer membrane 19 and the liquid 18 in the volume of the lower chamber 9, carried out after a certain period of time. The measurement is completed after reaching a steady flow of gas through the liquid 18 and polymer membranes 19.

The permeability coefficient of the system is calculated by the equation

_(one)

 Α · ί ’

where P is the permeability coefficient of the system ³ cm

stemes, -;

cm ² , s. atm

K - coefficient of calibration of the chromatograph, cm ³ / mm ² ;

I— thickness of the tested system (thickness of the liquid layer and thickness of two polymeric membranes), cm;

5 - area of the chromatographic peak, mm ² ;

And the surface of the polymer membrane, cm ² ;

ί - test time, s.

The delay time is calculated by the formula

(2)

A ₂ —A,

where τ is the delay time, s;

L [and L ₂ - the total height of the peaks on

chromatogram for Τι and τ ₂ . The diffusion coefficient of the system is calculated by the equation

I = -, (3)

ten

15

25

thirty

35

40

where Ζ) is the diffusion coefficient, cm ² / s;

I— thickness of the tested system, see

The solubility coefficient of the system is found from the ratio

where σ is the solubility coefficient,

cm ³ / cm ³ .

The coefficient of permeability of a fluid is determined by the equation

20

_ PP _X -I- PP ₂

R & P

(five)

where - the coefficient of permeability of the liquid;

Р - system permeability coefficient;

Р | 'and Р ₂ - permeability coefficients of polymeric membranes.

The diffusion coefficient of a gas in a liquid is determined by the equation

PP _{ + PP ₂ P _{ P ₂ - P '

(6)

where is the diffusion coefficient of the liquid;

O is the diffusion coefficient of the system;

O) and P ₂ are the diffusion coefficients of polymeric 'membranes.

The solubility coefficient of a gas in a liquid is found by the formula:

Lk

_W

(7)

where τ is the ratio of gas solubility in 45 liquids, cm ³ / cm ³ .

The proposed device with a chromatograph for determining gas transfer coefficients allows determining in one experiment the coefficients of permeability, diffusion and solubility in a wide temperature range (90–470 ° K simultaneously for several gases when transferring them through mixtures of liquids).

55

Claims (1)

Claim A device for determining gas transfer coefficients, consisting of a diffusion cell placed in a thermostat 60 and made of two chambers located one under the other, the top of which is equipped with a thermocouple, and the bottom one is connected through a metering tap to the chromatograph gas system, characterized in that 65 in order to expand the functional scope installation possibilities, between the upper and lower chambers of the diffusion cell, a liquid container is installed, made in the form of a cylinder, bounded by polymeric membranes, having two overlapping holes in the cylindrical part of the body, containing sealing elements at the ends, which are rubber rings, and the lower chamber equipped with a thermocouple.