SU1255898A1 - Method of determining density of liquid mediums - Google Patents

Abstract

The invention relates to instrumentation technology and can be used to measure the density of liquid media in various areas of industry. The purpose of the invention is to improve the accuracy of determination by eliminating the influence on the measurement result of a change in the gas flow rate and its temperature. The method consists in simultaneously supplying gas to a measuring chamber immersed in a controlled medium and to: a constant volume chamber. The pressure in both chambers is measured and the moment of their equality is recorded. From the registered value, the density is determined. 2 Il. 1C 01 ate 00 from 00

Description

I

The invention relates to a measurement technique, in particular, piezometric methods for measuring the density of liquid media, and can be used in various fields of industry, for example, chemical, petrochemical, food, etc.

The purpose of the invention is to improve the accuracy of determination by eliminating the influence on the measurement result of a change in the gas flow rate and its temperature.

Figure 1 shows a setup diagram for implementing the proposed density measurement method; Fig. 2 shows the graphical dependence of the pressure change in the measuring chamber and the constant volume chamber on time at various gas flow rates at their inlet.

The circuit contains two chambers: measuring 1 and constant volume 2; Measuring chamber 1 is made in the form of a tube immersed in a controlled medium. Chamber 2 is made in the form of a pneumatic chamber of constant volume, which is also immersed in a controlled environment. Gas from the outlets of the air flow regulators 3 and 4 is supplied to both chambers with a constant constant flow O, / G G. The chamber inputs) and 2 are connected to the inputs of the differential pressure gauge 5, while the camera input .2 is also connected to the pressure gauge 6.

When the measuring chamber is filled with gas with a constant flow rate G., pressure P. in it is determined from

gas

equations of state

I.V -0RT, (1)

where V, the volume of the measuring chamber Q is the mass quantity of gas in the chamber; R gas constant T is absolute temperature.

With GJ const the amount of gas in the measuring element

 G, t, (2)

where t is time.

Equation (l) with regard to equation (2) is

  G, tRT. (3)

The volume of the measuring chamber is determined by the level h of the controlled liquid in this chamber and its cross-sectional area, i.e.

V, - h-S, D4)

The pressure in the measuring chamber is determined by the hydrostatic equation

P, Pgh, (5)

558982

where p is the density of the controlled fluid, g is the acceleration of free fall,

From equation (5) it follows F

ten

15

20

25

(6) Substituting equation (6) into (), and then the resulting value in. equation (3), and having carried out the transformation, we obtain the equation that determines the pressure in the measuring chamber when it is filled with a squeezed pelvis (air):

I G t R T, h

R.I-Q-- P .- (7)

From equation (7), pressure P depends on the gas flow rate G supplied to the measuring chamber, on the temperature of the gas in the measuring chamber. Equation (7) is valid for V, O at the initial time instant, i.e. at t - 0.

In the event that the density of the controlled medium is judged by the time in which a given pressure P is reached in the chamber, formula (7) results in the form of

s, p,

G

t

The density measurement method is implemented as follows.

Gas from the output of the gas flow controllers (air) is simultaneously fed into chambers 1. and-2. The process of filling them with compressed air begins, and, as a result, pressure increases in the chambers. The rate of pressure change in the chambers is different due to different initial volumes, and V, 5 g de V, is the volume of chamber 2 of constant volume. The change in pressure in the measuring chamber 1 will occur at a faster rate at the initial moment of time than in the chamber 2 of a constant volume 2 (Fig 2).

Difference of pressure P - P

is fixed by a differential pressure gauge 5, here P is the pressure in the measuring chamber, Pjj is the pressure in the chamber of constant volume. As soon as the pressures in the chambers become equal to Р, —R. O, a zero level signal appears at the output of the differential pressure gauge. At this point in time, the pressure in the chamber 2 of a constant volume is recorded according to the indications of the pressure gauge 6. The density of the controlled fluid is judged by the magnitude of this pressure.

When the constant volume of chamber 2 is filled with compressed gas with a flow rate G, the pressure in it is determined by the equation of state

G R T

t.

(eight)

Both chambers are filled from one time point with the same flow rate, with both chambers immersed in a controlled environment.

At a certain point in time t, the pressure in the measuring chamber P will become equal to the pressure in the chamber of constant volume P, i.e.

P PJ (9)

Substituted from equations () and

(8) pressure values B, and P in

control (9), we get

G i RTf g GiRT.

,

Pg

§Г v

Since from equation (8)

, P, V,,

that

R,

 glYLp. S,

From Equation (10), the PO is seen at const

but it depends on the density of my environment, i.e.

RP CP

The change in the temperature of the gas and its flow rate in the proposed measurement method does not affect the result of the measurements.

Fig. 2 shows the pressure change in the chambers at different gas flow rates G supplied to chambers 1 and 2 according to the pressure change in the measuring chamber and in the constant-volume chamber with Q, 3 and 4, respectively, depending on the pressure change in the measuring chamber and in a constant chamber

15

20

25

thirty

Claims (1)

ma with g. Consumption G is greater than G. Invention Formula The method of determining the density of liquid media, consisting in supplying a gas to a measuring chamber immersed in a controlled medium, and measuring the gas pressure in it, characterized in that, in order to increase the determination accuracy by eliminating the effect on the measurement result of changes in gas flow and its temperature The gas simultaneously with the same flow rate is fed into the constant volume chamber, the equality of the gas pressures in both chambers is recorded, and the density is determined from the recorded value. With / katy Air P I T1 ; i FIG. I FIG. 2