Thermal gas flowmeter

I. Overview

The thermal gas mass flowmeter is designed based on the principle of thermal diffusion. From the appearance, the thermal gas mass flowmeter has two stainless steel rods with a diameter of about Φ 3, which are the sensors of the flowmeter. During operation, a sensor continuously measures the temperature T1 of the medium and serves as one side of the Wheatstone bridge, which we call a temperature sensor; Another sensor serves as the other side of the Wheatstone bridge, self heating to a temperature higher than the medium temperature up to T2. It is used to sense fluid velocity and is called a velocity sensor. The temperature Δ T=T2-T1, T2>T1. When a fluid flows through, the gas molecules collide with the sensor and take away the heat of T2, causing the temperature of T2 to decrease. To keep Δ T constant, the power supply current of T2 should be increased. The faster the gas flow rate, the more heat is taken away. There is a fixed functional relationship between the gas flow rate and the increased heat, which is the principle of constant temperature difference.

The constant temperature differential thermal gas mass flowmeter is not only unaffected by temperature, but also by pressure. The thermal gas mass flowmeter is a true direct mass flowmeter, and users do not need to adjust pressure and temperature.

2、 Technical parameters

Accuracy ± 1.5% Reading ± 0.5% Full Scale

Repeatability ± 0.5%

Range upper limit 60m/s

Lower range limit 0.05m/s

Applicable pipe diameter range: φ 3- φ 2000

Applicable pressure range 2MPa, no pressure compensation required

Applicable medium temperature range -30-200 ℃, no temperature compensation required

Applicable medium: all gases except acetylene gas

Containing dust, sand, moisture, and various corrosive gases.

Sensor diameter of φ 2.5 and φ 3

Insertion probe with outer diameter of φ 19 (standard)

Sensor material 316L, 304 stainless steel

Probe material (protective tube) 304 stainless steel, 316L

The material of the transmitter housing is die cast aluminum

Surface treatment thermal spraying

Instrument power supply 220V AC 24V DC

Output 4-20mA, HART, pulse RS-485 (MODBUS-RTU) communication

Load capacity 250 Ω

On site display of LCD instantaneous and cumulative display

Structural type: integrated type, split type

Type classification: flange insertion type, flange pipeline type, ball valve insertion type, ball valve pipeline type, flange ball valve hybrid insertion type, flange ball valve hybrid pipeline type

Alarm 1-2 relays, 5A/220V AC, 5A/30V DC

Protection level IP65

Cable outlet hole M20 × 1.5