What Is a Thermal Flow Meter?

Thermal flow meters use the principle of thermal diffusion. Thermal diffusion technology is a technology with excellent performance and high reliability under harsh conditions. Thermal flow meters have two temperature sensors placed in the medium, one of which is heated to a temperature above the ambient temperature, and the other temperature sensor is used to sense the temperature of the medium. The medium flow rate increases, the heat taken away by the medium increases, and the temperature difference between the two temperature sensors will change as the medium flow rate changes. According to the proportional relationship between the temperature difference and the medium flow rate, the fluid flow rate Q can be obtained. Most of the thermal flowmeters are used to measure gas, and only a small number of thermal flowmeters are used to measure small liquid flows.

There is a close relationship between the flow of fluid and the movement of heat, and the exchange of heat between flowing fluid and solids, and can be used to measure the flow and velocity of fluids. The method of measuring flow using thermal energy can basically be divided into two forms: One method is to place a heating element in a flowing fluid. The temperature of the heating element will necessarily change with the flow rate. The flow can be measured by the degree of cooling of the heating element; Another method is to add the necessary heat to the fluid. Since the thermal energy flows with the fluid, the flow can be obtained by detecting the change in heat at the corresponding point. The former is generally called thermal conductivity, and the instruments belonging to this measurement method include hot wire anemometers and hot ball anemometers. The latter is generally called the thermal type, and the instruments belonging to this measurement method include Thomas flowmeters and boundary layer flowmeters. ^[1]

Thermal flowmeter is a direct mass flowmeter, which can be used to measure mass flow.

According to different measuring principles, thermal flow meters can be divided into thermal flow meters and thermal conductivity flow meters.

The basic principle of the thermal measurement method is to heat the fluid in the pipeline from a heat source, and the thermal energy flows with the fluid. The mass flow of the fluid is obtained by measuring the heat change of the flowing fluid. ^[1]

Technical parameters of thermal flow meter: Measuring range: continuous adjustment from 0-20 cm / s to 1-100 cm / s. (Related to water, for other media, range expansion)

Features of thermal flow meters

1.No moving parts, reduced sealing surface, greatly reducing leakage rate, easy installation and routine maintenance;

2. Wide measurement range, the maximum measurement range can reach 20: 1 (liquid) or 30: 1 (gas);

3. Accurate measurement and high precision, flange type can reach 0.2% (liquid) or 0.5% (gas);

4, extremely high sensitivity, can measure ultra-small flow, which can measure low flow rate of 0.08m / s, electromagnetic flowmeter 0.5m / s;

5, good repeatability, generally 0.05 ~ 0.08%, with optional small signal removal, non-linear correction, filtering time can be selected;

6.The pressure loss is small, and the small diameter is only about 1/2 P of the standard orifice plate; the pressure loss above the DN100 diameter has begun to greatly reduce;

7, convenient calibration, in addition to the standard device verification, you can also use the dry calibration method, that is, using the weight hanging method, one-button operation can complete the calibration;

8. The flow resistance range can be changed according to actual needs. The online removable plug-in structure can realize non-stop production and continuous flow repair or replacement.

9, low-power battery on-site display, can directly read the displayed value online, the display can simultaneously read the instantaneous flow cumulative flow and percentage bar graph, and can switch to display the compensation temperature and compensation pressure indication;

10. Strong anti-interference and anti-impurity capabilities, multiple output forms, can transmit various parameters remotely, no need to mix heat.

11. The measurement gas does not need temperature and pressure compensation, and can directly display the standard volume flow.