Working principle of thermal flowmeter | Comparison of laminar flow principle and thermal principle gas mass flowmeter/controller performance and application (II) _ Baidu Knowledge .. | doppler ultrasonic flow meter working principle

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1. Working principle of thermal gas mass flowmeter

Thermal gas mass flowmeter works based on the principle of fluid heat conduction, and directly calculates the mass flow rate by measuring the heat change when the gas flows through the heating sensor. 1. Core working principle: Thermal diffusion principle: There are two temperature sensors inside the instrument (one for heating and one for temperature measurement). When gas flows through a heating sensor, it carries away heat, causing temperature changes. By measuring the temperature difference between two sensors or the energy required to maintain heating power, the mass flow rate of gas can be directly calculated. Due to the direct measurement of the heat carried away by gas molecules, there is no need for temperature and pressure compensation. 2. Key components and workflow: Sensor probes typically include a heating unit (RTD) and a temperature measurement unit (RTD). Circuit unit: Provides heating power and accurately measures temperature signal difference. Working mode: • Constant power method: Keep the heating power constant and calculate the flow rate by measuring the temperature difference (Δ T) between two sensors. • Constant temperature difference method: By dynamically adjusting the heating power, the temperature difference (Δ T) between the two sensors is kept constant, and the required heating power value is proportional to the flow rate

3. Main technical features • Direct measurement of mass flow rate: no additional temperature and pressure sensors need to be equipped for compensation conversion like volumetric flow meters. High precision: The precision of high-quality products can reach ± 1% or even higher of the reading. Strong ability to

measure low flow velocity: sensitive to small flow rates, capable of measuring flow velocities as low as 0.1 m/s. • No moving parts: high reliability, low pressure loss. Gas specificity: Instruments are usually calibrated for specific gases (such as air, N ₂, O ₂, etc.) when they leave the factory. When measuring different gases, recalibration is required because the thermal conductivity and specific heat capacity of different gases vary. 4. Typical application scenarios - Compressed air measurement and energy management - Gas (natural gas, coal gas) control for boilers and burners - High purity specialty gas monitoring in semiconductor manufacturing processes - Aeration process control in wastewater treatment - Laboratory gas consumption monitoring Selection and usage precautions - It is necessary to select the corresponding calibrated instrument based on the actual measured gas composition. -The installation point needs to ensure full pipe flow, usually requiring sufficient straight pipe sections in front and behind the instrument. -Not suitable for gases with viscosity, oil mist or high dust content, to avoid contaminating the sensor and causing measurement errors. -Pay attention to whether the process connection method, pressure rating, and material of the instrument match the process pipeline.

2. Types and principles of flow meters

Types and principles of flow meters Flow meters are one of the important instruments in industrial measurement, used to measure the volume or mass of fluid (liquid or gas) flowing through per unit time.

. With the development of industrial production, there is an increasing demand for accuracy and range of flow measurement, resulting in the emergence of various types of

Working principle of thermal flowmeter | Comparison of laminar flow principle and thermal principle gas mass flowmeter/controller performance and application (II) _ Baidu Knowledge ..

1. Working principle of thermal gas mass flowmeter

2. Types and principles of flow meters

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