# Method of determining viscous of liquid

FIELD: investigating or analyzing materials.

SUBSTANCE: method comprises measuring the initial liquid column in the vessel and time of discharging of a given a given liquid volume through the cylindrical passage under the action of gravity, measuring, at least three times, the height of the liquid column in the vessel, measuring the inclination of the outlet cylinder of the passage, and calculating the viscosity from the formula proposed.

EFFECT: enhanced accuracy of determining.

The present invention relates to the field of study physical and chemical properties of liquids.

There is a method of determining the viscosity of the liquid (A.S. No. 1191779, G 01 N 11/08, 1985) according to the difference of time elapses through the capillary of the same volume of the controlled fluid and a fluid of known viscosity. The disadvantage of this method is the complexity of implementation of the method that requires the actual doubling of the cost of the equipment.

There is a method of determining the viscosity of the liquid (A.S. No. 493703, G 01 N 11/08, 1976), which consists in measuring the time of expiration of the constant volume of the controlled fluid from the capillary under the action of gravity or external pressure and calculating the viscosity. The disadvantage of this method is the low accuracy of determination of viscosity as the expiration occurs when the variable height of the liquid column, which is not taken into account when calculating the viscosity

There is a method of determining the viscosity of the liquid (A.S. No. 1176213, G 01 N 11/08, 1983) using a capillary viscometer by fixing the level of the environment at a constant steady state expires and fixing the height of the column environment at the beginning of drip expiration. The disadvantage of this method is the complexity of its implementation, caused by the necessity of stabilizing the environment at a constant mode expires.

The closest anal the GOM to the present invention is a method for determining the viscosity of the liquid (Shchepkin SR, Kulakov MV Automatic instrumentation for chemical production. M., 1961, s-536), which consists in determining the time of expiration of a specified volume of liquid from the container through the capillary under the action of gravity and the calculation of dynamic viscosity according to the formula Poiseuille flow

where μ dynamic viscosity;

d - internal diameter of the capillary;

g - acceleration of gravity;

ΔP is the differential pressure acting on the liquid column in the capillary;

l is the length of the capillary;

Q is the average volumetric flow rate equal to Q=V/t;

V is the volume of fluid ejected through the capillary during t:

ν - kinematic viscosity;

ρ - the density of the liquid.

The disadvantage of this method is the low accuracy of determination of viscosity by using formulas describing stationary after at constant differential pressure acting on the liquid column in the capillary to the expiration of the alternating differential pressure as the height of the liquid column in the vessel above the capillary decreases during expiration and non-linear in time.

The technical task of the present invention is to improve the accuracy of determining the viscosity of a fluid at a variable pressure differential acting on the liquid column when it istace the AI through the cylindrical channel.

This object is achieved in that in the known method of determining the viscosity of liquids, which consists in the measurement of the initial height of the liquid column in the vessel and the time of expiration of a specified volume of liquid through a cylindrical channel under the action of gravity, what is new is that in the process of expiration produce at least three measurements of the height of the liquid column in the tank, measure the inclination of the cylindrical exhaust channel, and the viscosity is calculated by the formula:

where C is a constant;

n - number of measurements of the height of the liquid column in the vessel;

H_{j}- the number of measured values of the height of the liquid column in the vessel above the inlet to outlet;

L is the length of the cylindrical channel;

θ - the angle of the channel to the horizon;

H_{0}- the height of the liquid column in the vessel at the time of the beginning of measurements N and time t;

t_{j}- moments of measurements of H_{j},

t_{0}- the initial measurement N;

R is the internal radius of the cylindrical channel;

R_{c}is the radius of the cylindrical part of the vessel;

d_{j}- the coefficients of the series, approximating the distribution of the fluid velocity in the channel;

N is the number of members determined by the required accuracy of the races is billing purposes;

ν - the desired kinematic viscosity of the fluid;

g - acceleration of gravity;

ρ_{g}- the density of the gas in the cavity, which is the leakage of liquid;

ρ - the density of the liquid.

The system (1)...(4) derived from a more General analytical solution of the system of equations of continuity and Navier-Stokes equations describing unsteady unidirectional motion of a viscous fluid in a cylindrical channel of constant cross-section:

using the following assumptions and boundary conditions:

where t - time;

W(t,r) is the velocity of the fluid;

z ϕ, r - longitudinal, angular and radial coordinates;

ρF_{r}that ρF_{ϕ}projections of mass forces on the axis r and ϕ;

P(t,z) is the pressure of the fluid in the channel;

H(t) is the height of the liquid column in the vessel above the inlet to outlet;

P_{0}- the pressure above the liquid surface in the vessel;

P_{A2}the fluid pressure at the outlet of the channel;

It is possible to prove (or to verify by substitution)that the system (5)...(8) under conditions of limited options (9) and (10) satisfy the following expressions:

where d_{i}equal (4).

The constant C, depending on the parameters of the capacity of the channel and the liquid is calculated by equation (1) using a range of experimental values of H_{i}when n≥2. The values of d_{0}and ν uniquely determined from conditions (2) and (3).

The method is as follows: a system consisting of a tank partially or completely cylindrical in shape, the exhaust pipe of length L with the valve on the end, fill the investigated liquid, measure the pressure and temperature of the ambient air, measured the angle of the outlet of the cylindrical channel, open the valve to drain the fluid at atmospheric pressure and after 2-5% of the discharge capacity to produce at the moments t_{0}, t_{1}, t_{2}... measurements of the liquid level in the cylindrical part of the tank, then close the valve and calculate values of c using expression (1), and ν - using conditions (2), (3) and formula (4). Recent measurements of H_{i}must be made no later than the liquid falls below the cylindrical part of the vessel.

The method of determining the viscosity of liquids, which consists in the measurement of the initial height of the liquid column in the vessel and the time of expiration of a specified volume of liquid through a cylindrical channel under the action of gravity, characterized in that in the process of osteceni who make at least three measurements of the height of the liquid column in the vessel, measure the inclination of the cylindrical exhaust channel, and the viscosity is calculated by the formula

where C is a constant;

n - number of measurements of the height of the liquid column in the vessel;

H_{j}- the number of measured values of the height of the liquid column in the vessel above the inlet to outlet;

L is the length of the cylindrical channel;

θ - the angle of the channel to the horizon;

H_{0}- the height of the liquid column in the vessel at the time of the beginning of measurements N and time t;

t_{j}- moments of measurements of H_{j};

t_{0}- the initial measurement H;

R is the internal radius of the cylindrical channel;

R_{c}is the radius of the cylindrical part of the vessel;

d_{i}- the coefficients of the series, approximating the distribution of the fluid velocity in the channel;

N is the number of members determined by the required accuracy of calculations;

ν - the desired kinematic viscosity of the fluid;

g - acceleration of gravity;

p_{g}- the density of the gas in the cavity, which is the leakage of liquid;

ρ - the density of the liquid.

**Same patents:**

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FIELD: investigating or analyzing materials.

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EFFECT: enhanced accuracy of determining.

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