Selection and installation of thermal mass flow meter

The thermal flow meter is a meter that detects the flow rate using the heat transfer principle, that is, the flow rate is detected according to the heat exchange between the fluid in the fluid and the heat source (fluid inner or external heated object or heated). mainly measuring the gas; the thermal mass flow meter is mainly divided into two types, namely heat distribution and immersion (or insert).

1. Features of the thermal mass flow meter

(1) Main features of thermal distributed mass flow meter: Direct measurement of mass flow without temperature and pressure compensation; non-contact, no movable parts, no blocking, low pressure loss, high reliability; measurement of low flow micro gas Traffic, minimum 5ml / min (standard state); required gas medium dry cleaning, no water, oil, etc.; shunting can obtain linear characteristics, can be used to measure large, medium voltage flow, ensuring shunt temperature; dynamic response is very slow, The time constant is approximately 5 s.

(2) Main characteristics of immersion thermal mass flow meter: Direct measurement of mass flow without temperature and pressure compensation; no movable components, high reliability; suitable for large diameter, non-circular cross-section, narrow space measurement (insert After testing, the platinum resistance sensor uses a stainless steel housing, and it is not sensitive to dust, solid particles, oil and moisture of other parts. The plugin type can be removed continuously for repair and replacement. Can be used to measure the measuring of the dirt.

2. Use the thermal mass flowmeter

(1) For small and micro motion coriolis streams, the thermal distributed mass flow meter can be used for single-component gas or fixed proportional mixed gas measurements.

(2) The insertion immersion thermal mass flow meter can be selected for large caliber flow measurement.

3. Precautions for the installation and use of the thermal mass flow meter

(1) In the installation posture, most of the thermal distributed mass flow meters can be mounted at any position (horizontal, vertical or tilt), as long as the electrical zero adjustment is adjusted at the pressure and temperature after installation, some instruments are installed. Sensitive, must be carried out in strict accordance with the instructions. Most immersed thermal mass flow meters are not affected by the installation posture, but should be operated in strict accordance with the low flow rate.

(2) In the case of a front straight pipe section, the heat distribution is not sensitive, the immersion flow sensor and the insert meter with measured tube require a certain length of straight pipe section, and according to the manufacturer's recommendations.

(3) The vibration of the pipe connected to the thermal mass flow meter does not cause vibration interference within a common range; the detection lever of the inserted thermal mass flowmeter must be fixed to the pipe and avoid vibration.

(4) The thermal flow meter gauge response time is long, and the pulsation flow is not suitable.