SU1673844A2 - Method for measuring flow rate of substance by means of a tapered device - Google Patents

Abstract

The invention relates to measurement methods. The purpose of the invention is to increase the accuracy of measuring the mass flow rate of a fluid with a variable density. The flow of fluid moving in the pipeline 1 passes through the constriction device 2. The differential pressure at the constriction device 2 measured by the differential pressure gauge 3 is supplied as a signal to the input of the controlling computing device 4. At the output of the device 4, a signal is periodically generated that controls the actuator 7 which opens the valve 8. When the valve 8 is open, part of the liquid enters the bypass outlet 6, where the volume flow rate of the outlet part of the liquid is measured by means of the flow meter 9, which returns The value of the differential pressure at the restriction device 2 with the valve open and the volume flow in the bypass outlet measured by the flow meter 9 are also fed to the inputs of the computing device 4. In the computing device 4, the results are processed measurements, the density of the fluid and the mass flow rate of the fluid are calculated. The result obtained is recorded by the output device 5. The presence of a flow meter 9 installed on the bypass outlet allows the density of the fluid to be determined, which improves the accuracy of the mass flow measurement. 1 il.

Description

yo

ABOUT

4j

(A) 00

N5

My part of the liquid that returns to the main flow downstream of the restriction device 2. The differential pressure measured by the restriction meter 3 at the restriction device 2 with the damper open and the volume flow rate in the bypass discharge measured by the flow meter 9 are also fed to the inputs of the computing device 4. In the computational device 4

The invention relates to methods for measuring flow rates of a fluid, can be used to create variable pressure drop flow meters for the chemical, petrochemical, oil refining and other branches of the national economy and is an improvement of the method according to auth. USSR № 1530911.

The purpose of the invention is the enhancement of functionality by providing a measurement of the mass flow rate of a substance with a variable density.

The drawing shows a diagram of the device that implements the method.

The device contains a pipeline 1. a restriction device 2. a differential pressure meter 3. a specialized control computing device 4, an output device 5, a bypass branch 6, an actuator 7, a rotary valve 8, a volume meter 9 for consumption.

One input of the differential pressure gauge 3 is connected to the pipeline 1 to the restriction device 2, and the other after the restriction device 2, which is normal to pipeline 1, the output of the differential pressure meter 3 is connected to the input of the computing device 4, the other input 4 is connected to the output of the volume flow meter 9 connected to the bypass outlet 6. One output of the computing device 4 is connected to the output device 5, the other output, 4 - to the input of the actuator 7, the output of which is connected to the rotary valve 8, the bypass outlet 6 by one end through the turntable The socket 8 is connected to the pipeline 1 to the restriction device 2, the other end of the bypass outlet 6 is connected to the pipeline 1 after the restriction device 2 via the volumetric meter 9.

The device that implements the method works as follows

When the valve 8 is closed, the entire flow of fluid in the pipeline 1 passes through the restriction device 2. The value re-evaluates the measurement results, the density of the liquid and the mass flow rate of the liquid are calculated. The result obtained is recorded by the output device 5. The presence of a flow meter 9 installed on the bypass outlet allows the density of the fluid to be determined, which improves the accuracy of the mass flow measurement. 1 il.

Yes, the pressure ДР on the restriction device with the valve 8 closed, measured by the differential pressure gauge 3, is fed to the input of the control computing device 4. At

the output of the controlling computing device 4 is periodically generated by a signal that controls the actuator 7, which opens the valve 8. Part of the liquid in the pipeline 1 when

The open valve 8 enters the bypass outlet 6, where the flow meter 9 measures the volume flow of the discharge part of the liquid, which then returns to the main flow behind the restriction device 2.

The mass flow rate of fluid in the pipeline Q is equal to the sum of the mass flow rates of the fluid through the restriction device Od and through the bypass outlet O with the open valve, i.e.

Q - Od On

(one)

Measured by differential pressure gauge 3, the value of the differential pressure L Rd on the restriction device 2 with the valve open and the volume flow rate 00b in the bypass outlet, measured by the flow meter 9,

also come to the inputs of computational

device 4.

In computing device 4, the measurement results are processed according to the following dependencies. The mass flow rate Q. determined by the restriction device is expressed as (1):

 /

Q

(2)

where a is the coefficient of discharge;

d is the diameter of the orifice of the restriction device;

DR - pressure drop across the restriction device,

p is the density of the measured medium. In expression (2), BP is the pressure drop across the restriction device with the damper closed. Dependency for flow rate 45

STI through a narrowing device with an open damper has the form:

2,

(3)

One a-- - 2DRD / e

where LRd is the pressure drop across the restriction device when the damper is open.

The mass flow rate of the fluid Ob through a bypass outlet with an open damper can be represented as

About 0 / o (4)

where is the volume flow rate in the beipet outlet.

Substitution of expressions (2), (3) and (4) into the balance equation (1). get addicted

. AND

Substituting the expression (5) into formula (2) to determine the flow rate, we obtain

DR DR DRS OOB

ABOUT

 9 d4 lg

- se - -g

E

(6)

Thus, from the expression (6) by measuring the differential pressure L P on the restriction device with the valve closed and

50

55

ten

The differential pressure D RD and the volumetric flow rate Ob in the bypass outlet with the damper open determine the mass flow rate O taking into account the change in the density of the fluid.

Claims (1)

Claims The method of measuring the flow rate of a substance using a restriction device according to the author No. 1530911. characterized in that, in order to expand its functionality by measuring the mass flow rate of a substance with variable density, the volume flow rate of the discharge part of the flow is additionally measured, and the mass flow rate determined by the formula 7 L2B4 DR-UDRDR Q - 8 where a is the coefficient of discharge; d is the diameter of the orifice of the restriction device; D P is the pressure drop across the restriction device; D Rd - pressure drop across the restriction device when the valve is open, OOB is the volumetric flow rate of the fluid in the bypass outlet.