Thermal mass flowmeter- A complete guide

 

Instruthinkare professional manufacturers of flowmeters. Many flowmeters are available for delivery and export, such as thermal mass flowmeter, thermal mass gas flowmeter, Coriolis mass flowmeter, etc. These all are the solutions for measuring the flow rate of the fluid. Now, you don’t calculate the mass flow and rate manually.

What is a thermal mass flowmeter?

 

The thermal mass flowmeter is also known as a thermal flowmeter. It measures the mass flow of the fluid. Externally, the heat source makes the pipe or fluid hot, which changes the temperature of the fluid. The thermal mass flowmeter shows the measurement of the mass flow of gas, similar to natural gas. It also shows the energy needs to raise the temperature and measure the fluid’s mass flow. Most of the thermal mass flowmeter measures the volume of the flowing gases or the mass flow. Therefore, there is no need for extra pressure and temperature.

What are the types of thermal mass flowmeters?

 

BSCT offers different types of thermal mass flowmeters, so choose it according to your requirements.

• Thermal mass gas flowmeter: There are two sensors from which the fluid has to pass through in this flowmeter. One sensor receives the reference value, and the second one is for compensating the dispersed heat. Heating the current is used for measuring the mass flow of the gas.
• Insertion thermal mass gas flowmeter: it is the type of flowmeter which measures the mass and volume of the flow rate of the gas as well.

• Remote type Coriolis mass flowmeter: these meters are the leading ones for accurate measurement of the flow. Using this type of thermal mass flowmeter, you can measure volume flow, mass flow, temperature, and density of the liquid.

• Small size thermal mass flowmeter: the design of this thermal mass flowmeter is according to the release of heat and accepts that method where the temperature is constant. Due to its small size, it is easy to install and delivers highly accurate results.

What is the working principle of a thermal mass flowmeter?

 

The working principle of the thermal mass flowmeter is based on the truth that heat is released from the hot body when the fluid is flowing. There are two PT100 temperature sensors in the thermal mass flowmeter. One sensor measures the temperature of the fluid which is currently flowing. And the second one gets heat up, and its temperature is constant. When the fluid starts flowing in the measuring tube, the sensor with temperature cools down due to the flowing of the fluid. The whole cooling effect is dependent on the velocity of the flow of the fluid. The electric current helps in maintaining the temperature differential so that the mass flow is measured directly.

What are the advantages of using a thermal mass flowmeter?

 

There are several advantages of using a thermal mass flowmeter which is as follows:

• Involvement of direct measurement, display of mass flow and temperature of the fluid
• There is no compensation regarding the pressure and temperature
• The turndown ratio of the thermal mass flowmeter is high (100:1)
• It has an excellent sensitivity at the low-end
• During fluctuations, the thermal mass flowmeter reacts in a quicker way
• No moving parts are involved, which means that the thermal mass flowmeter requires less maintenance. It is used in applications even where there is an involvement of saturated gas.
• It can also measure the flow from the large pipes
• Thermal mass flowmeter gives highly accurate results

 

What are the specifications of a thermal mass flowmeter?

 

Medium	Accepts all types of gases except acetylene
Diameter of the pipe	· DN 10-80 (flange type) · DN 100-6000 (insert type) · We customize the diameter of the pipe in the split type
Accuracy rate	1 %
Operating temperature	· In sensor: default type 10 degrees to 200 degrees and when the temperature is high: 10 degrees to 350 degrees · In transmitter: 20 degrees to 45 degrees
Rate of flow	0.5-100 m/s
Pressure required	Medium pressure less than 10MPa
Power supply	· Compact type: DC 24 V or AC 220 V less than 18 W · Remote type: AC 220 V less than 19 W
Response time	1 second
Material of the pipe	Stainless steel, carbon steel, plastic
Display output	LCD in 4 lines
Content for displaying	Mass flow, flowing volume, accumulated time, accumulated flow, temperature, and standard flow.
Material of the sensor	Carbon steel or stainless steel
Protection of ingress	IP67 (part of the sensor)

Who are the manufacturers of a thermal mass flowmeter?

 

A few countries like Canada, the USA, and UK are the leading in manufacturing the thermal mass flowmeter. BSCT is a well-known manufacturer in UK. We have a wide range of flow meters in which thermal mass flowmeter and Coriolis mass flow meter are included. It directly measures the mass flow, volume flow, density, measure temperature of fluids without any extra equipment or calculations. For the last 20 years, we are also exporting different instruments, and the thermal mass flowmeter is among the demanding ones. Almost all industries are using our products for the measurement of flow, pressure, and temperature.

 

How to calibrate thermal mass flowmeter?

 

While using the thermal mass flowmeter, we as manufacturers study the whole process of our users and calibrate it according to the requirements. There is a doubt of inaccuracies if this step is missed. During calibration, a specific amount of gas flows from the sensor, and signals are observed. This process can achieve several times to receive the relationship between the mass flow and the signal received from the sensor for the gas. There are some factors needed for calibrating the thermal mass flowmeter are as follows:

• Size of the pipe: at the installation site, we review the pipe’s length and schedule the flow rate at full scale.
• Composition of gas:  our team evaluates the thermal properties of the gas during the process of calibration. As the behavior and variation of each gas are different. It has contents of carbon dioxide and methane.
• Upstream straight run: the installation of a thermal mass flowmeter is a very critical process. So, the straight pipe of upstream length is required for developing the flow profile.

• Insertion depth: we place the sensor of the thermal mass flowmeter in the center of the pipe. So, it helps detect the flow with the highest velocity, even if it is away from the walls of the pipes.

What are the factors affecting the accuracy thermal mass flowmeter?

 

Some factors affect the accuracy of the thermal mass flowmeter, which are below:

• The velocity profile: the fluid, including the gas, has various velocities flowing in the pipe. It is distributed in the whole pipe and runs in a straight direction reaches the sensor.

• Location of the installation: The location is significant and requires supervision while installing the thermal mass flowmeter. For selecting the position of the meter, first, check the location of the flow and look for the disturbances.

• Calibration of the flowmeter: while measuring the gas using the thermal mass flowmeter, the manufacturer has to understand the conditions of the user’s processes. He can even calibrate the thermal mass flowmeter according to the requirements of the user.
• Flow conditioners: the flow conditioners, also known as flow straighteners, help deliver the flow uniformly through the sensor. For consistent flow, it is essential to calibrate the thermal mass flowmeter and the flow conditioners according to the mentioned parameters by the user.

What are the tips for installing the thermal mass flowmeter?

 

While installing the thermal mass flowmeter, there are some essential tips to follow:

• The mounting position plays an essential role in installing the thermal mass flowmeter. Just install it in a horizontal position, especially when the pressure is high.
• There should be no objects fixed or placed in the inlet and outlet of the thermal mass flowmeter. It might cause disturbance when the rate of flow is high. It is recommended to use pipes with large diameters.
• Before installing the thermal mass flowmeter, make sure the pipe system is clean; you can also install the filters without steam. As a suggestion, in-line filters are available for a thermal mass flowmeter.
• Install the thermal mass flowmeter in the line and tight all the fittings according to the instructions given by manufacturers.
• Before applying the pressure on the fluid, always test the leakage of your systems.

What are the applications of a thermal mass flowmeter?

 

The thermal mass flowmeter has replaced the older technologies for measurement. Its features such as wide turndown, low-pressure drops, and low sensitivity make the applications to use it. Following are the applications of the thermal mass flowmeter:

• Compressed air: the thermal mass flowmeter measures the compressed gas and helps in allocating the internal plants. It helps in finding and look for the leakages if any. Removing a single leakage helps in saving the cost up to $4000 annually.
• Combustion of flowing air: during the controlling and regulating of fuel to air mixtures, there is a need for a thermal mass flowmeter for measuring the mass flow of combustion air.
• Natural gas: an ideal application of thermal mass flowmeter is the measurement of natural gas. It flows from the boilers, furnaces, dryers and reaches the heaters. It also helps in identifying the efficiency that helps in using less fuel.
• Greenhouse gas emissions: The EPA (Environmental Protection Agency) needs many facilities to make their yearly report regarding greenhouse gas emissions from every combustion source. A thermal mass flowmeter is a perfect choice for measuring the usage of natural gas, which follows the instructions of EPA for calculating greenhouse gas emissions.

What is the difference between the Vortex flow meter and thermal mass flowmeter?

 

The thermal mass flowmeter helps in measuring the flow of the fluid that exists in the pipe. The configuration of the thermal mass flowmeter is simple. The gas flowing passes through two sensors: one is for heating velocity, and the other is for temperature. This flowmeter works in such a way that the difference between the gas and sensor remains constant.

Vortex flowmeter helps in developing the flow profile and needs long straight pipes upstream. However, the reducers and elbows distort the flow profile. So, consecutive runs are the solution to resolve this issue. It is recommended to use 35 straight pipes diameters upstream and 5 straight pipes diameters downstream.

Which type of thermal mass flowmeter gives accurate results?

Coriolis mass flowmeter is the best flowmeter for delivering accurate results. This flowmeter is among our famous instruments as it works extraordinarily when there is a low-pressure drop.

Coriolis mass flowmeter has a pair of bent tubes. It helps in finding the Coriolis force received from the pair of bent tubes. It is from the inner mass flow carried by the fluid. The Coriolis force can get in two conditions: vibration of the frequency in the pair of bent tubes and flowing fluid in the tubes. The sensors can detect the receiving force and electric signals. The production of mass flow is through the regulation of the signal.

What is an insertion type thermal mass flowmeter?

There are several designs on which thermal mass flowmeter works. They are insertion, in-line, and by-pass. If there are large pipes and you don’t want them to be cut for installing the flowmeter. Simply use the insertion thermal mass flowmeter. This design is easy to install and available in various sizes. The thermal mass flowmeter must consider some factors: the flow, compensation, and cross-section rate to measure the total mass flow. While scaling, the new flowmeter for scaling must check the insertion length of the pipe. If the size is wrong, then measurement issues arise.

Does thermal mass flowmeter require temperature during the flow of gas?

Yes, the thermal mass flowmeter is indeed in need of temperature whenever the gas flows. It is used in the transmitter or externally where the pressure is different. As manufacturers do understand, the properties of the gas affect the heat transfer and change with temperature. The Resistance Temperature Detector measures the temperature during the process and is available for calculation. You can calculate the rate of the mass flow on the electric power or energy in milliwatts. There is a need for a constant temperature difference between the sensor, which is already heated, and the other one where the temperature is displaying.

What is the difference between a thermal mass flowmeter and a mass flow meter?

You can only use the thermal mass flowmeter for measuring the gas-only. This flowmeter uses various gases for absorbing and conductivity. It measures the mass flow of the liquid through the changes in the temperature. It happens when the fluid is flowing in the pipe and heats up by using an external source.

The mass flowmeter is also known as the Coriolis flowmeter. It uses the principle of Coriolis for measuring the mass of the fluid which is flowing in it. It helps in measuring the gas and liquid. The volume of the fluid depends on the temperature and pressure of the flowing fluid.

How to install a thermal mass flowmeter?

There are integrated flow meter converters and a flow sensor in the thermal mass flowmeter. Depending on the type of the flow sensor, you can install a thermal mass flowmeter in two ways:

• Integration plug-in thermal mass flowmeter: first, weld the base and the externally placed threads outside the pipe during the installation. The unique tool is used for punching the pipe of diameter 22mm. After the completion of the drilling process, eliminate this tool. After this step, the sensor installation is on the valve and takes in the mid of the pipe.

• Tube-type thermal mass flowmeter: this type of thermal mass flowmeter already has a pipe for the process. There are two types of connections for connecting the pipeline: thread connection.

What are the features of a thermal mass flowmeter?

The main features of the thermal mass flowmeter are defined below:

• the thermal mass flowmeter measures the mass flow where the temperature is constant
• There is no need for a transmitter for increasing the pressure and temperature
• There are no moving parts in all types of thermal mass flowmeter
• You can use a thermal mass flowmeter during the metal welding and construction along with the plug-in-ball valve. It helps in losing less pressure.
• The involvement of the microprocessor delivers impressive performance. In addition, conversion from digital to analog chip is also available.
• The thermal mass flowmeter is very sensitive to measure the low flow rate.
• It is the right choice for measuring all kinds of flowing gases

How to measure air or gas through a thermal mass flowmeter?

 

The thermal mass flowmeter requires heat transfer during the flow of the gas. If there is any moisture in the gas in contact with the sensor, you will observe the change in heat transfer. It results in incorrect flow measurement, and that’s why the thermal mass flowmeter uses constant differential temperature due to the droplets in the moisture. The power is also constant because the temperature of the sensor rises above the given point. The gas flow remains unchanged even because of the existing moisture. Instruthink, as the manufacturers have designed the processes to clean and dry the gases.

What is the response time of the thermal mass flowmeter?

It is better to receive a fast response but not a good choice in flowmeters. If the response is quick in the thermal mass flowmeter, it will deliver excess valves and cause instability in the flow. Too slow response lags the stability of the flow and is not possible to receive the desired outcome. There is some moisture in the gas, so the thermal mass flowmeter produces instability in the readings. It is due to the droplets which are hitting the sensors. Too high and too low response time is not suitable for a thermal mass flowmeter. You can calculate the response time is by the temperature induced by heating electrically and the velocity of the flow.

 

What is the theory of operation of a thermal mass flowmeter?

 

A thermal mass flowmeter uses the principle of heat conduction for measuring the mass flow of the gases. There are two thermal resistors (platinum RTD) in the sensor of the thermal mass flowmeter. The first one is mass speed sensor T1, and the other is temperature sensor T2 for measuring the temperature changes in the gas. The two RTD are placed during the measurement of the gas. T1 sensor heats up at the constant temperature and is above the temperature of the gas. T2 sensor helps in sensing the temperature of the measuring gas. When the mass flow rate increases, the flow of the air uses more heat, and there is a decrease in the temperature of the sensor T1. To maintain the constant difference of the temperature between T1 and T2, increase the healing power. Using King’s law of thermal effects, there is a relationship between heating power (P), the temperature difference (T1-T2), and mass flow Q.

P/ (T1-T2) = K1 + K2 f (Q) K3

K1, K2, and K3 are considered constants which are physical properties of the gas present.

What are the limitations of using a thermal mass flowmeter?

 

Here are some of the limitations that exist while using the thermal mass flowmeter. They are below:

• There is no relation between the mass velocity and transfer of heat in the thermal mass flowmeter. The thermal mass flowmeter provides sensitivity when the flow of the gas is low. In working conditions, it is dependent on the velocity. When the pressure increases, so the density of the gas also increases. The thermal mass flowmeter measures the rise in velocity, but the actual velocity remains the same.
• The thermal mass flowmeter measures the heat transfer through the gas flow. The moisture present in the gas gets in contact with the sensor. Gradually, the heat transfer and the thermal mass flowmeter give an incorrect measurement of the gas flow.
• During the measurement of gas, the thermal mass flowmeter needs calibration whenever there is a change in the gas composition. Therefore, any modifications in the gas lead to the collection of wrong data.
• The thermal mass flowmeter is suitable for measuring flows at low velocity. However, the correct measurement depends on how is the calibration of the thermal mass flowmeter. Some types of thermal mass flowmeters are not calibrated at low velocities for the measure.

 

How to overcome the limitations while using a thermal mass flowmeter?

 

The thermal mass flowmeter is a widely used instrument for measuring the mass and flow of the gas. Along with the limitations of the thermal mass flowmeter, there are some solutions to overcome them, which are as follows:

• Not to use thermal mass flowmeter where the pressure is more significant than 150 PSL in the gas systems.
• A knock-out drum helps in separating the moist drops from the gas. When the gas passes from the vessels, the velocity of the gas decreases, and the direction of the flow changes. Gravity helps the moisture to fall, and gas flows in an upward direction. Now, the moisture is removed effectively.
• Whenever there is a change in the heat transfer from the difference of the gas, it affects the accuracy of the thermal mass flowmeter, which is very minimum. Now the manufacturers have the composition of the gases, so they are well-aware about making a new gas.
• If the velocity of your application is low, do contact your manufacturer about the capacity and calibration of the thermal mass flowmeter regarding the velocity range.

 

What are the disadvantages of using a thermal mass flowmeter?

 

Along with the advantages, there are also some disadvantages while using the thermal mass flowmeter. So let’s take a look at it as well:

• The response of the thermal mass flowmeter is relatively low
• Whenever there is any change in the composition of the gas, the value of the measurement of the value changes and the conductivity. It causes errors in the results
• In small flowing fluids, a thermal mass flowmeter brings the required heat for measuring the gas
• If you use a thermal mass flowmeter during heat distribution, the scale on the pipe affected the measuring valve. It also involves cleaning, and thin tubes can cause blockages. It is not suitable for normal conditions.

Is there upstream and downstream in thermal mass flowmeter?

 

A thermal mass flowmeter measures the mass flow and density. All the measurements are not sensitive to the fluid profile. While installing, there are some limitations, so there is no need for upstream and downstream straight pipes. The sensors in the thermal mass flowmeter check the tubes of the sensors that they are complete. If you install the pipe in the vertical direction, check that the fluid (it can be any liquid including slurries) flows in up direction and gas is flowing downwards. But this meter cannot make the pipe straight if it is already not aligned.

What is the turndown ratio of the thermal mass flowmeter?

 

Turndown ratio defines the flow measurement, which shows the range of the particular flowmeter and its ability to measure accuracy. It also means the ratio between the maximum and minimum capacity. Therefore, it is beneficial when you are selecting a flowmeter for a particular application. For example, the turnout ratio of the thermal mass flowmeter is 1000:1. Similar turndown ratios are mentioned for the flowmeter is used on both gas and liquid. The manufacturers also mention the turndown ratios on their instruments and products.

The expression of turndown ratio is:

Turndown Ratio (TR)= Q(max)/ Q(min)

Q(max)= maximum flow

Q(min)= minimum flow

What are the troubleshooting issues in the thermal mass flowmeter?

 

There are some troubleshooting issues in the thermal mass flowmeter. Let’s take a look at these:

• There is no uniformity in the flow of the fluid.
• The installation of the flowmeter is less than the required pipe diameters upstream and downstream of the sensor.
• You cant securely scale the sensor probe.
• Sensor and transmitter are not working or showing the wrong results
• The rate of the flow in the pipe is larger or smaller than the mentioned limit of the flowmeter
• Distortion in the flow profile
• The small-signal cut-off is set above the limit or on high value.

 

What is the correction factor in the thermal mass flowmeter?

 

For measuring the mass flow of the gas, pressure, and temperature must be correct. The difference in pressure device delivers the actual flow rate, which gets modified according to the pressure and temperature. Total three signals transmit towards the computer. It helps in determining the mass flow rate of the gas. It means that every device separately is used for regulating the proper flow of the gas. The solution of all this one that in a thermal mass flowmeter. It is just a single instrument for directly measuring the mass flow rate of the gas.

How to calculate resistance using a thermal mass flowmeter?

 

You can use the thermal mass flowmeter in different applications. But it can also measure thermal resistance. Yes, it is true. It is stated in the standard ISO 8301 that thermal resistance can be calculated through the thermal flowmeters. All the ranges for the measurements are mentioned in this standard.  The essential factor is stabilizing the heat flow and forming a particular thermal resistance during the calculation. You can maintain it through the temperature difference between the hot and cold plates. That’s why you can use most of the thermal flowmeters for insulating the materials.

What is a Rosemount thermal mass flowmeter?

 

The Rosemount multivariable vortex flowmeter is a combination of temperature and fluid flow devices. It is the instrument that gives highly accurate results, and the cost of the installation is less. You can easily integrate and remove the temperature sensor from this flowmeter. The whole process of measuring temperature is smooth enough. It also helps assign the variables related to the flow and temperature and receive the output in digital form. The transmitter is also available for providing and compensating the pressure along with the temperature.  You can get the accurate volume on display from the applications. The turndown ratio of the Rosemount multivariable vortex flowmeter is 38:1.

Final thoughts:

Instruthinkis the leading manufacturer of flowmeters, and the thermal mass flowmeter is one of them. We do calibrate the flowmeters as well to produce the correct meter for your application. For inquiries related to the thermal mass flowmeter, call us on our given number or email us at info@ instruthink.com. Order your thermal flowmeter now.