How to measure the flow of viscous liquids? For example: glue, heavy oil, asphalt, etc. Commonly used flow meters may not be suitable. High Viscosity Flow Meters are instruments for measuring the flow of viscous fluids.
Common high viscosity flow meters are: Oval Gear flow meters. Mass flow meters, Target flow meters, and Wedge flow meters also work for viscous liquids.
Liquid viscosity
Viscosity is one of the important factors that affect the flow properties of fluids. Viscosity is a physical quantity that measures the resistance to fluid flow. Common units include dynamic viscosity (Pa·s), kinematic viscosity (m²/s), and Engler viscosity (EN).
Fluids with high viscosity require greater external forces to flow, and the energy loss during the flow process is greater. Fluids with low viscosity are easier to flow and have less energy loss.
Definition of High Viscosity
For the measurement of liquid flow, we generally consider that fluids with a viscosity exceeding 100 mPa·s are highly viscous.
For example, the kinematic viscosity of commonly used asphalt at 60°C is generally 100-300 mPa·s.
Common high viscosity liquids
Common high viscosity liquids are: Crude oil, diesel, and heavy oil. Asphalt, paraffin, honey, methanol, crude benzene, resin, and polyvinyl alcohol. High Viscosity Liquids are also widely used in various industries.
- High viscosity fluids (HVF) are used as raw materials (melted vegetable and animal fats) or finished products (chocolate, ice cream) in the food industry.
- In the construction industry, they are used as liquid phase change materials (PCMs) to store thermal energy in structures or building materials in buildings. For example, liquid concrete, asphalt and tar.
- In the automotive industry, they are used as PCMs for passive cooling of batteries, as well as for many other materials.
Common high viscosity fluids:
- Resin, glue;
- Hydraulic oil, lubricating oil, grease;
- Fuel oil;
- Ink, asphalt;
- Cooking oil, fish oil;
- Glucose;
- Honey;
- 48% sugar;
- And so on. . .
Our Sino-Inst flowmeters can measure the following media viscosities: 0.6-2mPa.s, 2-200mPa.s, 200-1000mPa.s, 1000-2000mPa.s, and the maximum is 400,000cp.
How does viscosity affect flow rate?
Viscosity is a physical property of a fluid that describes the forces between molecules within it. Its magnitude directly affects a fluid’s flow characteristics.
When a fluid passes through a pipe or other medium, it encounters resistance. The greater the viscosity, the stronger the interaction between the fluid and the pipe wall, and the greater the resistance the fluid encounters as it flows through the pipe. Furthermore, the greater the viscosity, the greater the viscous forces, which intensify the fluid’s internal friction and reduce its flow rate.
Thus, the greater the viscosity, the greater the internal friction and the slower the flow rate. The lower the viscosity, the lower the internal friction and the faster the flow rate. Therefore, viscosity and flow characteristics are closely related.
Featured Flow Meters for Viscous Fluid
Next, let’s take a closer look at the characteristics of high viscosity flow meters with superior properties.
Oval Gear Flow Meter – Best Flow Meter for High Viscosity Fluids
Industrial Oval Gear Flow Meters are positive-displacement type volume meters. Sino-Inst offers high-temperature and high-pressure types oval gear flow meters for special use. Oval Gear Flow Meters are suitable for chemical fluids, like: fuel oil, water… With features like easy installation, high precision, and a better price.
When the measured liquid enters the oval gear flowmeter through the pipeline, the pressure difference generated at the inlet and outlet drives a pair of gears to rotate continuously. The liquid measured by the crescent cavity is continuously transported to the outlet. The product of the number of revolutions of the oval gear and four times the displacement each time is the total flow of the measured liquid.
Therefore, it is not difficult to find from the measurement principle of the oval gear flowmeter that it relies on the pressure head of the measured medium to drive the oval gear to rotate for measurement. It has nothing to do with the flow state of the fluid.
When measuring liquids with high viscosity, the leakage from the gap between the gear and the metering space is small. Therefore, the greater the viscosity of the measured liquid, the smaller the leakage error. The more favorable it is for measurement, the higher the measurement accuracy. It can be said that the oval gear flowmeter is the best choice for measuring the flow of high-viscosity liquids.
Coriolis Meter for High Viscosity Fluids
The mass flow meter is an instrument that directly measures the flow of high-viscosity fluids. It has the advantages of high accuracy, good stability, and easy operation.
High-viscosity fluids have large internal friction, and traditional volume flow meters are difficult to accurately measure their flow. The mass flow meter uses a direct measurement method to avoid the errors of traditional volume flow meters. Therefore, it has a wide range of applications in measuring the flow of high-viscosity fluids.
The mass flow meter can also be customized to measure High temperature type: -50～350℃, High pressure type: up to 30MPa.
New Gear Flow Meter Customized For: Micro Flow – High Temperature – Low Temperature – High Pressure
The circular gear flowmeter is a new type of high-precision flowmeter. It can be used to measure media under various extreme conditions. Especially for high-viscosity fluids with small flow rates.
- High pressure resistance (1.0-45MPa);
- High and low temperature resistance (-196℃-200℃);
- Can measure various viscous media;
- High precision and high repeatability;
- Pulse output/analog output optional;
- Wide range ratio (1:100);
- Wide measurement range;
- Strong corrosion resistance and anti-fouling ability;
Target Flowmeter Measuring High Viscosity Fluid
The target flowmeter offers exceptional media compatibility. It is particularly well-suited for challenging flow measurement conditions, such as high viscosity, dirty media, media prone to condensation and clogging, high and low temperatures, and severe corrosion.
- High-temperature and high-pressure resistant: from -40°C ~ 450°C, with pressures up to 42 MPa.
- It can measure low-velocity media, with velocities greater than 0.1 m/s (a Reynolds number greater than 1000 is sufficient).
- It can measure high-viscosity media containing sediment.
- The flow range can be adjusted by replacing the load-bearing element as needed.
- Various mounting options are available: clamp-on, flange-mounted, threaded, in-line, sanitary, integrated, or split.
High Viscosity Flow Measurement
High Viscosity flow measurement is an important job for many industries.
High viscosity fluids are thick and hard to pour, and demanding additional power to pump. Such as oil, asphalt/ bitumen, Fructose, molasses, honey, glucose, resin, etc.
Low viscosity media, like pure water or milk, are very thin and easily pumped.
When a flowmeter is applied in high viscosity liquid, you should select an appropriate meter. Lots of different types flow meters cannot measure high viscosity fluid.
Turbine meters, DP flow meters and velocity measuring devices rely on a minimum liquid speed. And they are challenged by high-viscosity fluids. To use these techniques with high viscosity fluids, we can use larger diameter pipes. Larger diameter pipes will maintain line pressure drop and liquid transport costs as low as possible.
Many high viscosity fluid flow meter technologies operate best in the turbulent flow region i.e. with Reynolds numbers above ~2000. This is a dimensionless number that characterises fluid motion.
Sino-Inst’s Turbine flow meters, DP flow meters (like orifice plate) are velocity flowmeters. They both request a mini medium speed. Normally, High viscosity fluid cannot even offer this mini speed.
Choose sanitary flow meter for your pure water or milk.
The viscosity of a fluid refers to the property that the resistance of that fluid to flow. When the microfluids or the fluid layer inside the fluid have a relative movement, internal friction is generated. And this internal friction will prevent the fluid from doing relative movement.
For example, high viscosity fluids such as oil, honey, etc. are thick making them hard to pour and requiring additional power to pump. Low viscosity fluids like water or alcohol are thin and easily pumped.
Viscosity is generally expressed in five ways:
Dynamic viscosity, kinematic viscosity, Engle viscosity, Rayleigh viscosity and Sai viscosity.
Obviously, any actual fluid is viscous. Its viscosity can be reflected in the different ability of different fluids to resist relative. It can be seen that viscosity is an inherent property of actual fluids. And it will directly reflect the difference in fluid’s ability to resist relative movements. It can be seen that viscosity is an inherent property of the actual fluid. And it will directly affect the fluid’s flow and heat transfer performance.
The measurement of Crude Oil and Viscous fluids requires rugged and reliable metering equipment.
Compared with other liquid measurements, petroleum flow measurement has the following main features.
- There are many oil varieties, and the differences between different varieties are large.
a. Medium and low viscosity petroleum products such as kerosene, diesel. Low viscosity, low temperature, clean fluid, no harsh requirements for measurement.
b. High-viscosity oils such as crude oil, heavy oil, residual oil, etc., have high viscosity. In order to facilitate transportation, they are often heated to higher temperatures. The fluid contains solid impurities and must be strictly filtered before flow measurement.
c. Low viscosity oils such as gasoline and liquefied petroleum gas have very low viscosity.
- High measurement accuracy is required. The measurement of oil used for trade settlement must reach the required accuracy. To ensure the interests of both the supply and demand sides. GB 17167 stipulates that the measurement of gasoline, diesel, and crude oil used for energy consumption assessment of branch plants (workshops) and key energy-consuming equipment should reach 0.5% accuracy. The measurement of gasoline, diesel, and crude oil used for entering and leaving enterprises should reach 0.35% accuracy. While in In bulk oil measurement, the requirements for measurement accuracy are higher and the significance is greater. For example, the crude oil measured by the crude oil transfer metering station is about several million tons per year. And an error of one thousandth will cause a settlement error of several million yuan per year.
- On-line live flow calibration should be considered. The flowmeter used for petroleum measurement generally has a large caliber, which is extremely inconvenient to remove for inspection. Generally, there should be a real flow calibration facility or an interface connected to a standard meter for online real flow calibration.
- Mass flow measurement. In most cases it is settled by mass flow.
- The fluid is flammable and explosive.
The resistance to flow is proportional to the speed V. For laminar flow, the pressure drop can be expressed as:
J = 32μVL / (ρgd ^ 2)
The relationship between the flow velocity V, the flow rate Q, the pipe diameter d, the pressure difference P, and the dynamic viscosity coefficient μ of the material is:
V = ρgd ^ 2P / (32μL)
Q = πd ^ 4ρgP / (128μL)
Other physical quantities in the formula:
π—pieral ratio;
ρ—fluid density,
g—gravitational acceleration;
P—pressure difference between two ends of the pipeline;
L—pipe length
The value of fluid viscosity varies with the type of fluid and changes with pressure and temperature.
- 1) Fluid type. Generally, the viscosity of a liquid is greater than the viscosity of a gas under the same conditions.
- 2) Pressure. For common fluids, such as water, gas, etc., the viscosity value does not change much with pressure and is generally negligible.
- 3) Temperature. It is the main factor affecting viscosity. As the temperature increases, the viscosity of the liquid decreases, and the viscosity of the gas increases.
a. Liquid:
Cohesion is the main factor that produces viscosity. When the temperature increases, the distance between molecules increases. The attractive force decreases. so the shear stress generated by the shear deformation speed is reduced. So the fluid viscosity value decreases.
b. Gas:
The distance between gas molecules is large and the cohesive force is small. So the viscosity is mainly caused by the exchange of momentum of gas molecules. As temperature rises, molecular movements accelerate. And momentum exchange is frequent, so fluid viscosity increases.
Sino-Inst offers a variety of customized solutions for high-viscosity fluids. In addition to high-viscosity fluid flow meters, we also offer high-viscosity fluid level sensors, high-viscosity fluid pressure sensors, and high-viscosity fluid temperature sensors.
How Does Viscosity Affect the Different Flow Meter Technologies?
Viscosity affects different meters in different ways. Here we briefly discuss. We define “high viscosity” as: more than (say) 1000 cP.
Positive Displacement (PD) Meters
The accuracy of Positive Displacement meters, such as Oval gear meters, are not greatly affected by changes in viscosity, which is one of PD meters’ main advantages. A PD meter can be calibrated at 3 centipoise and be within ±0.5% accuracy in a range of 1 centipoise to 1,000,000 centipoise.
Mass flow meters can measure high-viscosity liquids. But performance can sometimes be compromised. If the pressure drop across the flowmeter limits, accurate flow measurement to the lower part of the flow range.
Magnetic flowmeters can also measure electrically conductive liquids that exhibit high viscosity. As a practical matter, magnetic flowmeters are not often applied to high-viscosity liquid. Because the majority of such applications involve hydrocarbons that are not sufficiently conductive.
Differential pressure and Vortex shedding flowmeters
Differential pressure and vortex shedding flowmeters are generally not applied to high-viscosity liquids. Because of their Reynolds number constraints.
Unless pressure is a concern, you should not need to consider the effect of fluid viscosity if it remains with a range of 3 to 500cP. For oval gear meters equipped with High Viscosity Rotors, that range increases to 3 to 2,000cP.
For liquids with viscosities of less that 3cP, there are several considerations that need to be factored into your final choice of flow meter(s).
- Stated minimum flows need to be adjusted to 10% of the stated maximum flows. For example, the OM006 (1/4 inch) meter has a published range of 0.5 to 27 GPH. If used for measurement of fluids with a viscosity of 3cP or less, adjust the range to 2.7 to 27 GPH.
- Although we can’t offer specifics, accuracy can vary slightly when measuring any liquid that has a viscosity ranging from 1.0 to 3cP that has no lubricating qualities.
- The most difficult fluids to measure with an Oval Gear meter are non-lubricating liquids with viscosities below 1.0cP.
- For fluids with viscosities greater than 2,000 cP, end users should give serious consideration to the use of High Viscosity (HV) rotors. Doing allows for additional flow ranges under similar conditions.
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Sino-Inst has many years of experience in flow meter production and supply. We specialize in providing efficient flow measurement solutions for users in various industries.
Whether it is high temperature, high pressure, low temperature, high viscosity or other extreme conditions, we will try our best to meet your measurement needs. If you have any questions, please feel free to contact our engineers!