What is Kinematic Viscosity? Meaning and Applications in Life

Industrial oil or hydraulic oil has a very important property, which is viscosity. The particles in fast-flowing streams will impact the slower particles, increasing kinetic energy or inhibiting movement, thus creating internal friction. Today’s article will help you understand what kinematic viscosity is, its meaning, and its applications in real life.

What is Kinematic Viscosity?

Kinematic viscosity of a liquid, also known as dynamic viscosity, is a measure of the internal resistance of a fluid under the influence of gravity with flow. It is determined by measuring the time in seconds for a fixed volume of liquid to flow over a known distance by gravity through a capillary tube in a calibrated viscometer with tightly controlled temperature.

This value is converted into standard units such as square millimeters per second or centistokes (cSt). A viscosity report is only valid if the temperature at the test site is also reported, such as 23 cSt at 40 degrees Celsius.

Among the tests used to analyze used oil, no test provides better consistency or repeatability than viscosity. Similarly, no property is more important for effective component lubrication than the viscosity of the base oil. Viscosity can be measured or reported in terms of dynamic viscosity and kinematic viscosity. These two types are easily confused but have quite significant differences.

How is Kinematic Viscosity Measured? It is usually measured using a viscometer, expressed through static viscosity, dynamic viscosity, and the coefficient of dynamic viscosity. Most used oil analysis experiments measure and report dynamic viscosity. However, most on-site viscometers measure kinematic viscosity but are programmed to estimate and report kinematic viscosity.

As viscosity analysis becomes increasingly important and on-site oil analysis tools become more widely available, oil analysts must understand the difference between kinematic and dynamic measurements.

Learn about the kinematic viscosity of liquids (Photo: Internet)

In simple terms, viscosity is the ability to resist the flow of a liquid at a certain temperature. Viscosity is sometimes referred to as thickness or weight. However, viscosity is not a measurement of size, so calling oil with high viscosity “thick” or oil with low viscosity “thin” is entirely wrong.

Similarly, if there is no temperature reference when measuring viscosity, the report is meaningless. Temperature is a necessary condition to explain viscosity readings. Viscosity is usually reported at temperatures of 40 degrees Celsius and 100 degrees Celsius, or both if required.

How is Kinematic Viscosity Measured?

The technical units commonly used to express viscosity today include centistokes (cSt) for kinematic viscosity and centipoise (cP) for dynamic viscosity. Kinematic viscosity in cSt at 40 degrees Celsius is the basis for the ISO 3448 kinematic viscosity classification system, an international standard. Other common kinematic viscosity systems like Saybolt Universal Seconds (SUS) and the SAE classification system may also relate to measurements at 40 degrees Celsius or 100 degrees Celsius.

Kinematic Viscosity Measurement Formula

How is kinematic viscosity measured? It is measured by noting the time oil passes through the hole of the capillary tube under the influence of gravity. The hole in the kinematic viscometer creates a fixed resistance to the flow. Capillaries of different sizes are available to accommodate liquids of varying viscosities.

The time required for the liquid to flow through the capillary tube is converted to kinematic viscosity using a simple calibration constant provided for each tube. The main procedure for measuring kinematic viscosity is ASTM D445. It is usually modified in used oil analysis laboratories to make the measurement more efficient and time-saving.

Kinematic viscosity is often denoted as v, measured in m²/s, illustrated in the figure below:

 

Illustration of measuring the kinematic viscosity of lubricants using a capillary viscometer (Photo: Internet)

Kinematic viscosity and dynamic viscosity are related through the following expression:

Formula for calculating kinematic viscosity (Photo: Internet)

Table of kinematic viscosity of liquids:

Below is a table of kinematic viscosity measurements for some common liquids:

CentiStokes	Saybolt Second Universal (SSU, SUS)	Typical liquid
0.1		Mercury
1	31	Water (20 độ C)
4.3	40	Milk SAE 20 Crankcase Oil SAE 75 Gear Oil
15.7	80	No. 4 fuel oil
20.6	100	Cream
43.2	200	Vegetable oil
110	500	SAE 30 Crankcase Oil SAE 85 Gear Oil
220	1000	Tomato Juice SAE 50 Crankcase Oil SAE 90 Gear Oil
440	2000	SAE 140 Gear Oil
1100	5000	Glycerine (20 độ C) SAE 250 Gear Oil
2200	10000	Honey
6250	28000	Mayonnaise
19000	86000	Sour cream

Meaning and Applications of Kinematic Viscosity in Real Life:

Kinematic viscosity is an important concept in physics and chemistry, especially for applications involving fluid flow. It is a crucial factor in design applications, product manufacturing, and processes in life. So what are the applications of kinematic viscosity? Here are some real-life applications:

Oil and Energy Industry

This industry is the most common application of kinematic viscosity. It is used to predict and determine the flow conditions of oil, gas, and other liquids during extraction, production, and transportation. This helps optimize efficiency, reduce incidents in pipelines, and related equipment.

Food Industry

In the design and production of beverages and food, kinematic viscosity plays a vital role. It directly affects packaging processes, texture, quality, and product distribution.

Pharmaceutical Industry

What is the role of kinematic viscosity in pharmaceuticals? The quality control and testing of pharmaceuticals such as creams, tablets, and syrups all require kinematic viscosity.

Application of kinematic viscosity in manufacturing industries (Photo: Internet)

Chemical Industry

In this industry, kinematic viscosity helps control many chemical production processes, such as flowing through pipelines, mixing, and chemical reactions.

Printing Ink and Paint Industry

Kinematic viscosity controls the production of ink, paint, and glue based on their viscosity and texture. This ensures uniformity and suitability in the application process.

Textile Industry

Kinematic viscosity is important in fabric and fiber production, especially in the stretching and twisting process of fibers, affecting the texture and quality of textile products.

Paper Manufacturing Industry

Kinematic viscosity affects the spreading and adhesion process of paper fibers, directly impacting the texture and quality of paper during production.

Read more: Malcom Viscometers PCU-285

Conclusion

Hapoin has helped you understand the concept of kinematic viscosity and its significance in various industries. It is clear that the kinematic viscosity of liquids must be understood and controlled to ensure product quality, improve production efficiency, and ensure operational safety.

Jasmine Wu -Hapoin Vietnam