What is a flowmeter?
Fluid flow measurement is one of the most important measurement parameters in various industries.
In fact, most experts, after measuring the temperature of the fluid, the most important quantity to measure in industry is called flow.
Given the importance of measuring this quantity as well as the variability in the process of various industries, many methods for measuring fluid flow have become common over time.
Choosing the right Flowmeter for any industry requires comprehensive knowledge of the performance of these devices and considering the main parameters of measurement such as accuracy, cost to sell flowmeters, repair and calibration costs, compatibility of Flowmeter performance with the conditions of the production process in the industry Is desired and..
Important points in choosing a flowmeter
- Fluid specifications
- Amplitude of pressure and temperature changes
- Piping and installation site
- Measurement range and accuracy of the device
- Flow measurement unit
Basis of mass thermal flowmeter operation
Common CTMF mass flowmeter includes body and flow sensor. The temperature sensor is located inside the body of the flow meter. A certain part of the gas flow passing through the body of the flow meter passes through the working path and the gas flow is calculated by it.
A flow meter in which a common flow sensor includes a thin tube and two temperature sensors. Depending on the manufacturer, the heater can be combined with any of the temperature sensors or placed separately in the middle of the flow sensor, ie between the upstream temperature sensor T 1 and the downstream sensor T 2 .
A powerful power supply transmits constant heat to the flowmeter sensor. In the absence of motion in the fluid, both sensors measure the same temperature. When the flow rate increases, the heat travels away from the upstream sensor T 1 and is transferred to the downstream sensor T 2. The bridge circuit interprets this temperature difference and generates the flow output signal with the help of an amplifier. The difference between the measured temperature between the sensors and the flow rate is mass.
Flow in thermal flow meters sensors is accurate only at low rates. Therefore, to measure higher rates, it is necessary to distribute the entire flow. This fluid distribution in the body is equipped with a linear flow element. This element produces a linear drop and pressure that is proportional to the mass flow.
The range and range of this type of flow meter is directly affected by the specific heat of the gas c p . Calibration is not possible for all process gases. If the gas is corrosive or hazardous, reference gases such as air and nitrogen are usually used for calibration.
Since a lot of heat is transferred in high flows, in this equipment, practically only very low flow rates can be accurately measured. As a result, linear flow elements are commonly used for CTMF flowmeters. Which are located in the main line and cause a certain proportion of Dubai to cross in different areas of the crossing line. The end of the capillary tube is connected to the outlet and inlet of the flow linear manifold. This structure fixes the gas passage ratio through the capillary section. In this type of design, the heater and temperature sensors are placed in the capillary tube instead of the main path. Of course, there is another plan that the sensors are not located directly in the main path, ie without the capillary tube and the Dubai linear element.
Application of mass thermal flowmeter
Thermal flowmeters, also known as thermal dispersion or thermal immersible flowmeters, belong to a set of instruments used to measure the total mass flow of fluids, especially gases flowing through closed ducts.
Another type of thermal flowmeter is the capillary tube flowmeter. Many mass flow controllers (MFCs) that use a set consisting of a mass flowmeter, electronic components, and a valve are based on this design. In addition, a mass heat flowmeter can be embedded in a silicon-based MEMS chip based on measuring the temperature difference.
The use of this method in mass heat flowmeters is attributed to LV King, who in 1914 published his famous law called the King Law, which showed how a heated wire immersed in a fluid has a mass velocity flowing in a Measures the point of it. King called the instrument a “hot wire anemometer.” However, industrial examples of thermal flowmeters were not unveiled until the 1960s and 1970s.
Both types of heat flowmeters mentioned earlier measure the mass flow of a fluid using heat transferred from a hot surface to a flowing fluid. In thermal diffusion and buoyancy heat flowmeters, heat is transferred to the boundary layer of the fluid flowing on the hot surface. In a capillary tube-type heat flowmeter, heat is transferred to a mass of fluid that passes through a thin, heated tube. Principles of operation Both types of thermal flowmeters are essentially thermal, but their differences are such that two separate standards are required for them. In addition, their applications are very different. Thermal diffusion flowmeters are commonly used for industrial applications related to gas flow in pipes and ducts, while capillary types of heat flowmeters are mainly used for smaller gas flows and clean liquid in pipes.
Important points in choosing thermal flowmeters:
- Thermal flowmeters are commonly used to measure clean gases such as air, nitrogen, hydrogen and other industrial gases.
- They can be used for mixed gases if the composition of the gas and consequently its heat capacity is known.
- An important advantage of this method is that it does not depend on gas density and therefore does not need to compensate for temperature and pressure changes.
- This method cannot be used for abrasive fluids due to damage to the sensor. Also, the fluids that the flowmeter creates on the sensors reduce its accuracy.
- Because the calibration of these sensors is based on the thermal properties of their components, such as sensors and heaters, repairing and replacing them reduces its accuracy.
- Gases in which there is a possibility of condensation and production of liquid droplets cause invalid measurements in this type of flowmeter because the liquid droplets زیادی a large amount of heat that is absorbed by the heater.
- Non-contact without input sensor
- No obstruction in the fluid path
- Less maintenance needs
- Suitable only for low flow gases
- It is prone to corrosion and wear.
Rose Calibration Company in Melbourne, Australia with over ten years of experience provides all calibration, maintenance, and repair services throughout Australia. If you live in Sydney, Melbourne, Adelaide, Perth, Geelong, and Brisbane, you can receive your quote in less than two hours by fill-up the form via the “Booking” link.