In industrial flow measurement, differential pressure flow meters hold a prominent position due to their reliable measurement principle and wide range of applications. Venturi flow meters and V-cone flowmeters are typical examples of differential pressure flow meters. Although both use the Bernoulli equation to calculate flow by measuring differential pressure, they each have their own advantages and disadvantages in practical applications.
The post will explain the differences between the two from various perspectives. I hope you will find it useful.
What is a V-Cone Flow Meter?
A V-cone flow meter combines a V-cone sensor with a differential pressure transmitter. It is a type of differential pressure flow. Its measurement principle is based on Bernoulli’s theorem, which states that energy conversion in a closed pipe is proportional to the square root of the differential pressure.
It usually consists of an inlet, a tapered section, and an outlet. The tapered section is its key feature. It measures flow by generating a differential pressure. It can accurately measure flow of various media over a wide Reynolds number range.
Advantages
- Minimal pressure drop;
- Generates a more stable differential pressure signal;
- High reliability;
- Integrated structural design;
- Advanced multivariable measurement technology;
- Comprehensive compensation functions;
- Powerful intelligent features;
- Features self-diagnosis, configuration, cyclic display, communication, power-off protection, and device management information;
- High repeatability and measurement accuracy: Repeatability better than ±0.1%; Measurement accuracy better than ±0.5%;
- Wear resistance, self-cleaning, excellent long-term stability, and long service life;
- Short straight pipe requirements: Generally, 0-3D upstream and 0-1D downstream. If a valve is installed upstream of the V-cone flow meter, the distance between the flow meter and the valve should be 3D.
- The V-cone flow meter can be configured with any user-specified transmitter to output a 4-20mA differential pressure or other flow signal.
Disadvantages:
- If the medium contains particulate matter, it can easily clog;
- Some pipeline valves opened too quickly, resulting in a sudden surge of pressure, can break the cone probe or even damage the pipe;
- Because it is a differential pressure flow meter, it requires pressure and temperature compensation;
- If multiple V-cone flow meters are used on a single pipeline, the pressure drop is even greater.
What is a Venturi Flow Meter?
A Venturi flow meter is a fluid measurement instrument based on Bernoulli’s equation. It is designed by British engineer Venturi in the late 18th century. And it is widely used in fluid dynamics, it utilizes a sudden expansion and contraction structure in a pipe to accurately measure fluid flow rate.
Advantages:
- Wide range of applications;
- High measurement accuracy;
- Wide measuring range;
- No moving parts;
- Low resistance;
- Simple structure.
Disadvantages:
- Requires larger installation space;
- Sensitive to fluid properties;
- High installation requirements.
V-Cone Flow Meter vs. Venturi Flow Meter
V-Cone flow meters and Venturi flow meters differ in many ways. Based on Sino-Inst’s many years of experience in flow meter supply, we will explain the differences between the two in the following aspects.
Different Working Principle:
V-Cone flow meter working principle:
Because real fluids are viscous and not ideal fluids, when flowing in a pipe, there are two flow regimes: laminar flow and turbulent flow, provided the flow is fully developed. According to the principle of conservation of energy in continuous flow and Bernoulli’s equation: For a fluid flowing in a laminar state, the velocity distribution is a parabola centered on the pipe centerline, and the pressure drop across the pipe is proportional to the flow rate. For a fluid flowing in a turbulent state, the velocity distribution is an exponential surface symmetrically centered on the pipe centerline, and the pressure drop across the pipe is proportional to the square of the flow rate.
Working Principle of a Venturi Flow Meter:
According to the Venturi effect, when a restricted flow passes through a constricted flow area, the fluid velocity increases. The velocity is inversely proportional to the flow area. When a fluid filling a pipe passes through a restrictive device, a localized constriction forms at the throat of the Venturi tube.
This increases the fluid velocity and reduces the static pressure. Then,it creates a differential pressure across the venturi tube. The greater the fluid velocity, the greater the pressure differential. This differential pressure can be used to calculate the fluid velocity and, therefore, the flow rate.
The Venturi effect is a physical phenomenon in which a fluid (liquid or gas) increases its velocity while simultaneously reducing its static pressure when passing through a constricted pipe. Its name comes from its discoverer, Italian physicist Giovanni Battista Venturi. This effect is used to create a Venturi tube. A classic Venturi tube is typically divided into three sections: a smoothly converging inlet section, a circular throat with the smallest diameter, and a gradually expanding outlet section.
Different Measurement Media:
V-Cone Flow Meters:
- Applicable for measuring the flow of various gases, liquids, and steam;
- Coke oven gas, steam, flue gas, crude oil, propylene gas, liquefied petroleum gas;
- Natural gas, ammonia, hydrogen, slurry, nitrogen, hydrogen peroxide;
- Organic gases, two-phase liquids, air, circulating water, and other media;
- Fluids containing fixed particles, low-pressure fluids, high-humidity gases, and various dirty fluids.
Venturi flow meters are particularly suitable for measuring non-corrosive, low-viscosity liquids or gases. They can also be used for measuring complex flow conditions such as two-way flow, mixed-phase flow, low flow rates, large pipe diameters, and irregular-shaped pipes. Their internal structure and materials are resistant to corrosion and wear while ensuring measurement accuracy.
Choose a V-Cone Flow Meter or a Venturi Flow Meter
All in all, a Venturi flow meter is suitable for measuring fluids with a wide flow range and low viscosity. A V-Cone flow meter is suitable for measuring fluids with a samll flow range and high viscosity. The choice of flow meter should be determined based on the specific measurement conditions.
Read More about:
Sino-Inst Featured Differential Pressure Flow Meters
Venturi flow meter classifications:
1. Classic Venturi tube: Used for flow measurement in various media, featuring low pressure loss, short required straight pipe sections, and long service life.
2. Sleeve-type Venturi tube: Primarily used for flow measurement and control of large-diameter, high-pressure, or hazardous media in the petrochemical industry.
3. Venturi nozzle: Suitable for measuring various media, featuring low pressure loss, short required straight pipe sections, and long service life. The installed length of the main body is shorter than that of the classic Venturi tube.
How to calculate flow rate in a venturi meter?
The principle of a venturi tube is to measure flow rate using the local pressure drop as the fluid passes through a pipe. The calculation formula is as follows:
Q = K √(2gh)
Where Q is the fluid flow rate, K is the coefficient of the venturi tube, g is the acceleration due to gravity, and h is the height difference between the two ends of the venturi tube. What is the difference between a V-cone flow meter and an orifice flow meter?
What is the difference between a V-cone flow meter and an orifice flow meter?
Both use differential pressure to measure flow.
Orifice flow meters were introduced relatively early. Their simple structure and wide measuring range make them widely used across various industries. While technological advancements have overcome the disadvantage of low turndown ratio, the replacement orifice plate is expensive, leading to high procurement costs. This led to the development of the V-cone flow meter as a replacement.
Although the V-cone flow meter shares the same operating principle as the orifice flow meter, there are essential differences between them. The orifice flow meter is a center-constricting throttling device, while the V-cone flow meter is a side-constricting throttling device. The limited measuring range of the orifice flow meter is a major limitation to its use. The V-cone flow meter overcomes this shortcoming.
In summary, in many cases, replacing an orifice flow meter with a V-cone flow meter should offer more advantages than disadvantages. So, when choosing, we must still consider factors such as the actual operating conditions.
How accurate is a V-cone flow meter?
Sino-Inst's V-cone flow meters have a repeatability of better than ±0.1% and a measurement accuracy of better than ±0.5%.
In short, Sino-Inst’s V-cone flow meters and Venturi flow meters are both differential pressure flow meters. They are used in various industrial applications.
Sino-Inst is a flow meter supplier from China. If you need to purchase a flow meter, please feel free to contact us. We will provide you with high-quality and affordable products. We will not increase prices due to tariffs. Our flow meters are sold worldwide. Sino-Inst can provide you with the most suitable measurement solution free of charge.
