Case Study: Custom Thermal Mass Flow Meter For Nitrogen Flow Measurement

Thermal mass flow meters are widely used to measure gas flow in industrial processes. They determine the mass flow rate by measuring the thermal changes in the fluid as it flows through the sensor. Sino-Inst’s thermal mass flow meters utilize a unique temperature differential measurement method to overcome the drawback of traditional thermal mass flow meters that use a constant temperature differential principle. These meters, when measuring gas flow, suffer from significant zero-point drift caused by water, oil, and impurities in the gas, leading to measurement failures.

Customization Case

A customer from Indonesia needed to measure nitrogen flow and requested a custom Japanese standard flange connection and a split display. We ultimately determined the following specifications:

Thermal gas mass flow meter
DN100mm
Nitrogen
DC24V/AC220V dual power supply
Output 4-20mA with RS485 communication
LCD display of instantaneous flow and cumulative
total
Main body material: 316
JIS 16K RF Japanese standard flange connection
Split type with 20m cable
Measuring range: 28-2800Nm³/h
Temperature resistance: 100℃
Pressure resistance: 1.6MPa

Nitrogen Applications

Nitrogen is a colorless, non-toxic, odorless inert gas with low production cost and high efficiency. Therefore, nitrogen is used in various industries.

Metallurgy and Metalworking Industries

Nitrogen is widely used in the metal industry. Nitrogen-based atmosphere heat treatment, using nitrogen as a primary component, is a safe, environmentally friendly, and energy-saving new technology and process. Industry experts indicate that almost all heat treatment processes, including carburizing, nitriding, normalizing, tempering, bright annealing, spheroidizing annealing, and recrystallization annealing, can be performed using a nitrogen-based atmosphere.

Petrochemicals

In the chemical industry, nitrogen is widely used as chemical feed gas, pipeline purging, atmosphere replacement, protective atmosphere, and product transportation, improving petroleum processing and refining processes.

Fresh Food

Nitrogen-based storage and preservation of fruits, vegetables, and tea is a popular method for preserving and preserving fruits, vegetables, and tea. In an environment high in ammonia and low in hydrogen, it can slow metabolism and inhibit ripening, thereby reducing oxidative spoilage and decay in food. Nitrogen-filled packaging can maintain food’s geometric shape, dryness, crispness, color, and aroma. Furthermore, in the production of beer and beverages, nitrogen can be used as a process gas, not only preserving freshness and storage but also improving the taste of beer and beverages.

Operating Principle

Thermal gas mass flowmeters utilize the principle of thermal diffusion, which is based on the fact that fluid flow removes heat from the heated object. Thermal diffusion technology maintains excellent performance and high reliability under harsh conditions.

The sensor portion of our thermal gas mass flowmeters consists of two reference-grade platinum resistance temperature sensors. During operation, one sensor continuously measures the medium temperature T1; the other sensor, which self-heats to a temperature higher than the medium temperature T2, senses and measures the fluid flow rate and is called a velocity sensor.

A constant temperature difference ΔT = T2 – T1 is created between the two, with T2 > T1. When fluid flows through, gas molecules collide with the sensor and remove heat from T2, causing the temperature of T2 to drop. To maintain ΔT constant, the supply current to T2 must be increased. The faster the gas flows, the more heat is removed. There is a fixed functional relationship between gas flow rate and heat gain.

Our thermal gas mass flowmeter operates on the principle of constant temperature difference and is unaffected by temperature or pressure, eliminating the need for pressure and temperature corrections and resulting in high accuracy.

Advantages

Wide rangeability, suitable for gas leak detection.
Excellent vibration resistance and long service life. The sensor has no moving parts or pressure sensing components, making it unaffected by vibration affecting measurement accuracy.
Easy installation and maintenance. Installation and maintenance can be performed without interrupting production, if site conditions permit. (Special customization required.)
Fully digital processing, strong anti-interference capabilities, reliable measurement, and high accuracy.
RS-485 or HART communication enables factory automation and integration.
Optional power supply.

Applications

Measurement of oxygen, nitrogen, hydrogen, chlorine, natural gas, liquefied petroleum gas, flare gas, compressed air, and multi-component gases.

Measurement of blast furnace gas, coke oven gas, flue gas, air in gas processes, calciner flue gas, and combustion gases in coal-fired boilers.

Measurement of aeration and chlorine in biogas and water treatment.

Measurement of flue gas flow from chimneys.

Measurement of gas flow generated in cement and cigarette production processes, carbon dioxide flow in beer production, and gas flow in solvent recovery systems.

Measurement of primary and secondary air in power plant blast furnaces, flow in underground mine ventilation or exhaust systems, and gas flow (velocity) in heating, ventilation, and air conditioning systems.

Other Flowmeters For Nitrogen Flow Measurement

Metal tube float flowmeters: Particularly suitable for measuring low-velocity and low-flow nitrogen. A mechanical type is available to accommodate situations where there is no power supply. It requires minimal straight pipe length.

Vortex flowmeter: Vortex flowmeters can measure gases with temperatures up to 350°C. They are not suitable for measuring gases with velocities below 4 m/s. They require high straight pipe length.
Gas turbine flowmeter: Suitable for measuring clean, room-temperature gases. They are primarily used for natural gas.

Differential pressure flowmeter: Suitable for measuring the flow of high-pressure, large-diameter, and high-temperature gases, but they suffer from high pressure drop.

Coriolis mass flowmeter: The highest accuracy (up to ±0.2%). The medium can contain impurities, but it is more expensive. When measuring gases, higher pressure is required for good measurement results.

Comparison Of Nitrogen And Liquid Nitrogen Flow Measurement

Nitrogen is typically at room temperature and pressure. Thermal mass flowmeters, metal tube float flowmeters, vortex flowmeters, gas turbine flowmeters, and mass flowmeters are commonly used to measure nitrogen flow.

Liquid nitrogen is an inert, colorless, odorless, and transparent liquid at extremely low temperatures. Liquid nitrogen can reach temperatures as low as -196°C. Water in pipes and fittings freezes quickly at these temperatures, causing blockages. Therefore, for liquid nitrogen measurement, our flowmeters require cryogenic design, and both the pipes and flowmeters must be well insulated. We typically use gear flowmeters, cryogenic liquid turbine flowmeters, mass flowmeters, and differential pressure flowmeters to measure liquid nitrogen flow.