Glass, kinematic viscosity

X5.2 A detailed procedure for the measurement of the ice point and recalibration of thermometers is described in 6.5 of Test Method E 77. The suggestions in the following sections of this appendix are given specifically for the mercury-in-glass kinematic viscosity thermometers described in Table X4.2, and may not apply to other thermometers. 

Gla.ss Ca.pilla.ry Viscometers. The glass capillary viscometer is widely used to measure the viscosity of Newtonian fluids. The driving force is usually the hydrostatic head of the test Hquid. Kinematic viscosity is measured directly, and most of the viscometers are limited to low viscosity fluids, ca 0.4—16,000 mm /s. However, external pressure can be appHed to many glass viscometers to increase the range of measurement and enable the study of non-Newtonian behavior. Glass capillary viscometers are low shear stress instmments 1—15 Pa or 10—150 dyn/cm if operated by gravity only. The rate of shear can be as high as 20,000 based on a 200—800 s efflux time. 

On studying the temperature dependence of the kinematic viscosity of glasses it appears that the formula... 

Example 11.3 Consider a gas-solid horizontal pipe flow. The pipe diameter is 50 mm. The particle used is 50 pm glass bead with the density of 2,500 kg/m3. The average particle volume fraction is 0.1 percent. The gas density and kinematic viscosity are 1.2 kg/m3 and 1.5 x 10-5m2/s, respectively. Estimate the minimum transport velocity and power consumption per unit length. 

In glass capillary viscometers, both entrance and exit effects depend on the kinetic energy of the fluid stream in the capillary. Based on extensive experimental data, the kinematic viscosity, v = r]/p, data with a correction term for kinetic energy is expressed ... 

The ratio of viscosity and density is the kinematic viscosity, which is directly measured in gravity-driven flows. The kinematic viscosity has the same temperature dependence as the friction coefficient. The density of polymer melts weakly decreases as temperature is raised, imparting a weak temperature dependence to the modulus at any relaxation time r. The temperature dependence of the viscosity of polymer melts is dominated by the dependence of the friction coefficient. Near the glass... 

The use of these empirical procedures is being superseded by the more precise kinematic viscosity method (ASTM D-445, IP 71), in which a fixed volume of fuel flows through the capillary of a calibrated glass capillary viscometer under an accurately reproducible head and at a closely controlled temperature. The result is obtained from the product of the time taken for the fuel to flow between two etched marks on the capillary tube and the calibration factor of the viscometer and is reported in centistokes. Because the viscosity decreases with increasing temperature the temperature of test must also be reported if the viscosity value is to have any significance. For distillate fuel oils the usual test temperature is 38°C (100°F). 

The most common viscosity test is the kinematic viscosity method (ASTM D445, IP-71, DIN 51566 and ISO 3104). Note that lubricant viscosity is discussed in detail in the next chapter. The kinematic viscosity is the product of the time of flow and the calibration factor of the instrument. The test determines the kinematic viscosity of liquid lubricants by measuring the time taken for a specific volume of the liquid to flow through a calibrated glass capillary viscometer under specified driving head (gravity) and temperature conditions. The test is usually performed at a lubricant temperature of 40°C and/or 100°C to standardize the results obtained and allow comparison among different users. 

Viscosity can also be measured with viscometers where the movement or the developed force is due to gravity, by the fluid s own weight. Such a system is developed when the fluid flows in special glass tubes (capillary tubes). In this case, the kinematic viscosity (qj or v) is measured, and the measurement unit is in square millimetres per second. This unit is also known as centistoke (cSt). However, when the fluid is forced to flow under negative pressure (vacuum), then the dynamic viscosity (Pa-s) is measured. 

Dilute-solution viscosity (solution viscosity) n. (1) A catchall term that can mean any of the interrelated and quantitatively defined viscosity ratios of dilute polymer solutions or their absolute viscosities. (2) The kinematic viscosity of a solution as measured by timing the rate of efflux of a known volume of solution, by gravity flow, through a calibrated glass capillary that is immersed in a temperature-controlled bath. Two common types of viscometer are the Ostwald-Fenske and Ubbelohde. From the viscosities of the solution rj and the solvent 7o, and the solution concentration c, five frequently mentioned viscosities (viscosity ratios, actually) can be derived, as follows ... 

Viscosity is usually measured by the time it takes a fluid to flow through a tube under standard conditions. Figure 5.2 is a schematic of a glass Ostwald viscometer. The fluid to be measured is poured into the left tube. The unit is immersed in a constant temperature water bath and when a constant temperature is reached, the fluid is drawn up into the right tube. The time required for the level to fall from 4 to 5 is measured with a stopwatch The quantity p/p = v of the liquid, called kinematic viscosity is proportional to the time required for outflow. Such a device... 

In a bubble viscometer, a liquid streams downward in the ring-shaped zone between the glass wall of a sealed tube and a rising air bubble. The rate at which the bubble rises is a direct measure of the kinematic viscosity. The rate of bubble rise is compared with a set of calibrated bubble tubes containing liquids of known viscosities. Bubble viscometers are shown in Figure 7-30. 

This test method specifies a procedure for the determination of the kinematic viscosity, p, of liquid petroleum products, both transparent and opaque, by measuring the time for a volume of liquid to flow under gravity through a calibrated glass capillary viscometer. The dynamic viscosity, rj, can be obtained by multiplying the kinematic viscosity, p, by the density, p, of the liquid. 

Viscometers—Use only calibrated viscometers of the glass capillary type, capable of being used to determine kinematic viscosity within the limits of the precision given in the precision section. 

Thermometers—C alibrated liquid-in-glass thermometers (see Table X4.2) of an accuracy after correction of 0.04 F (0.02 C) can be used or any other thermometric device of equal accuracy. ASTM Kinematic Viscosity Thermometers 47F and 47C are suitable for the most commonly used temperature of 140T (60 C). 

Thermometers—Calibrated mercury-in-glass thermometers of suitable range and graduated to 0.1 T (0.0S C). They shall conform to the requirements of Specification E 1. Calibrated ASTM kinematic viscosity thermometers are satisfactory. Other thermometric devices ate permissible provided their accuracy, precision, and sensitivity are equ or better than ASTM kinematic viscosity thermometers. 

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