JPH0150852B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a capillary viscometer for measuring the viscosity of a low-viscosity liquid. Viscosity The viscosity of a liquid can be measured with high accuracy.

In the conventional liquid capillary viscometer, the viscosity η is determined based on the following principle equation.

η=πr ⁴ (P ₁ − P ₂ )/8LQ Where, η: Viscosity (poise) r: 1/2 of the inner diameter of the capillary (cm) L: Length of the capillary (cm) Q: Liquid flowing in the capillary Volumetric flow rate (cc/sec) P ₁ : Liquid pressure at the inlet of the tube (Kg/cm ² ) P ₂ : Liquid pressure at the outlet of the tube (Kg/cm ² ). In this equation, π, r, and L are constants, so in a capillary viscometer, _{P 1} ^and P ₂ The viscosity was determined from η=K.(P ₁ −P ₂ ).

Therefore, in such a capillary viscometer, it is essential to keep the volumetric flow rate Q constant, and the quantitative performance of the volumetric flow rate of the metering pump as a liquid delivery pump is a fundamental requirement that determines measurement accuracy. A gear pump with good metering performance and low pulsation is used for the pump.

However, for low-viscosity liquids with a viscosity of 10 CP or less, liquid leaks from the gap in the measuring section of the gear pump, making it difficult to ensure quantitative performance. However, as long as a capillary viscometer is used, the condition that Q is constant must always be satisfied, so
In order to improve the metering performance of gear pumps, measures are taken to reduce the gap in the metering section, but liquid leakage in the gap is unavoidable and the ability to measure the volumetric flow rate is lost. As a result, seizure is likely to occur in this portion, resulting in the gear becoming unable to rotate. Therefore, there is a natural limit to narrowing the gap, and there are technical limits to pumping fluids of 10 CP or less by volumetric measurement, and conventional capillary viscometers cannot measure accurately. Ta.

Therefore, in order to solve such problems, in this invention, the liquid to be tested is measured by the mass flow rate, a mass flowmeter is installed in the liquid flow path, and the mass flow rate is measured by the mass flowmeter. , based on the signal from the mass flowmeter, the driving rotation speed of the pump is controlled to maintain the mass flow rate W at a constant value, and the density fluctuation of the liquid is eliminated so that πr ⁴ ρ/8LW = K', and P ₁ and The system detects the pressure difference of P ₂ and calculates the viscosity η as η = K′・(P ₁ − P ₂ ). means, a capillary viscometer that measures the viscosity of the test liquid according to the pressure on both sides of the capillary, and a mass flowmeter that measures the mass flow rate;
By adjusting the flow rate of the test liquid by the test liquid flow means in accordance with the information signal regarding the mass flow rate from the mass flow meter, the flow rate of the test liquid can be adjusted without considering fluid leakage in the gap of the pump. , it is possible to accurately measure the viscosity of a low-viscosity liquid without narrowing the gap in particular.

An embodiment of this invention will be explained with reference to the drawings.
1 is a differential pressure converter, 2 is a mass flow meter (Japanese Patent Application Laid-open No. 1983-
52570), 3 is a pump, 4 is a motor for driving the pump, 5 is a rotation speed controller, 6 is a flow rate controller,
7 is a differential pressure transmitter, and 8 is a viscosity recorder. A thin tube 11 is provided in the differential pressure converter 1, each end of which communicates with the outside of the differential pressure converter 1, and a liquid-sealed diaphragm type pressure detector 10 is provided on a wall surface facing each end of the thin tube 11. , 10' are provided, and the pressure receiving pressure detectors 10, 10' and the differential pressure transmitter 7 are communicated with each other through pressure guiding tubes 20, 20', respectively. Said thin tube 1
A jacket 21 is formed around the outer periphery of the test piece 1 to supply a heating medium (warm water) to keep the measured liquid at a constant temperature and the liquid density constant. 12 is its supply port, and 13 is its discharge port. Further, one of the ports for communicating with the outside of the thin tube 11 is communicated with the measurement liquid inlet 9 through a pipe 22, and communicated with the mass flowmeter 2 through the other pipe 14. The mass flow meter 2 communicates by a pipe 15 with a pump 3, which in turn communicates with a measuring liquid outlet 19 by a pipe 15'.
A jacket 23 is placed around the pipes 15, 15'.
Cases 16 and 16' are provided, and a heat medium is supplied to keep the temperature of the measured liquid constant and the density of the liquid constant. 18 is its supply port, and 17 is its discharge port. The flow rate controller 6 receives an analog or digital output signal from the mass flow meter 2 and sends a signal to the rotation speed controller 5 according to the signal value, and the rotation speed controller 5 adjusts the rotation of the motor 4 based on the signal. The mass flow rate is controlled and maintained at a constant value. At this time, since the temperature and mass flow rate of the liquid are kept constant, there is almost no density variation and it is determined that πr ⁴ ρ/8LW=K'=constant. Further, the differential pressure P ₁ −R ₂ obtained by the differential pressure converter 7 is sent to the viscosity receiving recorder 8, where the value K′=πr ⁴ ρ/8LW obtained by the mass flow meter 2 is calculated by η The viscosity is determined as =K′・(P ₁ −P ₂ ).

With the above configuration, when performing measurement, when the pump 3 is driven to flow the measurement liquid and supply a heat medium to each jacket, the motor 4 is controlled by the signal from the mass flowmeter 2 as described above. and pump 3
By keeping the mass flow rate constant, K′ based on a constant mass is obtained. On the other hand, the pressure difference between both ends of the thin tube 11 is sent from the differential pressure transmitter 7 to the viscosity recorder 8.
Therefore, the viscosity is determined from the above-mentioned K'.

Since the present invention has the configuration described above, it is possible to accurately measure the viscosity of a low-viscosity liquid without considering fluid leakage in the gap of the pump and without making the gap particularly narrow. will be possible. Furthermore, even if the gear pump does not have quantitative properties, it can be used satisfactorily as a liquid feeding pump.

[Brief explanation of drawings]

The figure is a layout diagram partially shown in cross section. 1...Differential pressure converter, 2...Mass flow meter, 3...
Pump, 4... Motor, 5... Rotation speed controller, 6
...Flow rate controller, 7...Differential pressure transmitter, 8...Viscosity receiving recorder, 11...Thin tube, 21, 23...Jet.

Claims (1)

[Claims] 1. A pump that flows the test liquid through the flow path of the test liquid, a capillary viscometer that measures the viscosity of the test liquid according to the pressure on both sides of the capillary, and a mass flow rate of the test liquid. and a mass flowmeter for measuring the mass flow rate of the test liquid, and adjusts the flow rate of the test liquid by the pump in accordance with the information signal regarding the mass flow rate of the test liquid from the mass flow meter, and adjusts the flow rate of the test liquid flowing through the flow path. A capillary viscometer characterized by controlling the mass flow rate to a constant value.