Thermal Mass flowmeters



AT Thermal Mass Flowmeter is one of the most advanced flowmeter in gas mass monitoring. The sensor of AT Thermal Mass Flowmeter is related to flow rate of the gas mass and meet the situation which the temperature and pressure is unstable .


THE PRINCIPLE OF OPERATION


Thermal sensor consists of two sensing elements - a velocity sensor and a temperature sensor that automatically corrects for changes in gas temperature(figure1). The transducer electronics heats the velocity sensor to a constant temperature differential above the gas temperature and measures the cooling effect of the gas flow. The electrical power required to maintain a constant temperature differential is directly proportional to the gas mass flow rate.

In order to keep the stable temperature between Ts and Ta, circuit should be provided higher power. The range of power is related to the mass flow rate of liquid. Through test the output of power can get the mass flow rate. Furthermore, the heat on the heated velocity sensor bring by the move of gasses not cause the heat exchange. So this kind of flowmeter can measure all kinds of gases. The table of AT Series Thermal Mass Flowmeter please see figure.



Classic ITMF flow meter consists of two temperature sensor figure 2. A measured portion of heating power p be put into one sensor to rise the temperature to measured alue T2. Other sensor test gas temperature T1. Gas mass flow can be assured according to the difference between heated sensor and gas in temperature (△T=T2-T1) and heating power P.

△T P = K + K x (Q )K3


In the formula: K1, k2, k3--design and calibration parameters; △T-- Range of temperature (=T2-T1), K; P---input heating power, w; Qm-- mass flow, kg/s. This is definited as Gregory King's law. k1, k2, k3 depend on geometric dimensioning of sensor and gas characters,as heat conductivity, viscosity and specific heat capacity. These quotient numerical value are particular own by flowmeter and gas,thus ITMF should correct according to the tested gas. The relevence among heating power P,range of temperature and mass flow (qm) can be signified as follows: In the formula: K1,k2,k3--design and calibration parameters; △T-- Range of temperature(=T2-T1), K; P---input heating power, w; Qm-- mass flow, kg/s. This is definited as Gregory King's law. k1, k2, k3 depend on geometric dimensioning of sensor and gas characters,as heat conductivity, viscosity and specific heat capacity. These quotient numerical value are particular own by flowmeter and gas,thus ITMF should correct according to the tested gas.





Feature



ACCURACY


AT series thermal mass flowmeter has well Repeatability, ± 0.1% of full scale. The accuracy of system can reach ± 1 %. Although the accuracy of other kinds of flowmeter will be better than ± 1 %, but the accuracy is hard to reach ± 1 % through the combination of temperature transmitter, pressure transmitter, secondary meter, the total error for real system will be more than that value, especially when the component of flow changes. Because AT series thermal mass flowmeter directly measure mass flow, it has sensor and transmitter and display by its own. But the traditional gas flow meter need to make up for a measurement system with temperature transmitter, pressure transmitter, secondary meter. According to reliable design theories, obviously, AT series thermal mass flowmeter possess a good reliabilities and measurement accuracies.


WIDE MEASURING RANGE

AT series thermal mass flowmeter use advanced intelligent chips and display alphanumeric 2 x 16digit backlit LCD, it can display ten digits of cumulant flow and four digits of instantaneous flow and flow percentage and the self-check. There are three keys behind the display, which can switch display content and setting various data. It also can use the remote-control which has three matching keys. You can do all operations by using the remote-control with no cover opened. The unit of flow rate can set kg/h or Nm3/h. The connection has 4-20mA signal output and RS232 communicator, and adopting MODBUS or HART protocol.

The range ability of orifice plate is 1:3, the range of vortex flowmeter is about 1:10. But AT series thermal mass flowmeter is 1:120. The upper limit of min flow velocity is 0.5m/s, upper limit of max flow velocity is 60m/s and lower limit is 0 m/s. This feature make AT series thermal mass flowmeter can meet almost all occasions that the flow has big changs. AT series thermal mass flowmeter is rare to adjust to low flow velocity measurement products among all kinds of flowmeters. Because of radication, orifice meter has a high error when flow rate is lower than 30%, and the vortex flowmeter will have normal vortex to be measured when the flow velocity is higher than 5m/s. Yet the sensor of series thermal mass flowmeter has good sense to low flow rate and it could take 0.5 m/s as a upper limit.


EASY INSTALLATION

AT series thermal mass flowmeter can be installed on the level, uprightness and incline duct, but should be upright with duct.
AT series thermal mass flowmeter use flange hold way to installed. It can provide a set of flange, bolt and nut. series thermal mass flowmeter mate flange at random and used for welding on the trapping duct.
AT series thermal mass flowmeter usually need 15D straight pipe. When the occasion can not meet this require, you can choose our own rectifier.
When fixing the flowmeter by flange, the thermal mass flow in the dust could be shown after being electrified.



NON CUT OFF INITIAL INSTALLATION OF INSERTION METERS

When the diameter of duct between Ф40-Ф2000mm, we suggest you use series insertion Thermal Mass flowmeter (figure 4). In many occasions, the installation need no stop gas, the insertion ones which with ball valve and special tools could well achieve the non cutoff installing and demounting.(figure 5) More details please refer to the "installation".

APPLICABLE DUCT DIAMETER RANGE

Ф6-Ф10000mm

MASS FLOW MEASUREMENT

Measure and display gas mass flow without compensation of temperature and pressure.

DISPLAY ON-SITE

Accumulated mass flow or standard cube flow, instantaneous mass flow or standard cube flow, flow percentage.

HIGH PRESSURE RESISTANT

Maximum internal duct pressure is 20Mpa.

LOWER FLOW RATE

Minimum upper limit flow rate is 0.5m/s, lower limit is 0 m/s.

SETTING ON-SITE

Suited for all occasions, automatic identification and revise on-site according to different composition of gas.

NON LINEARITY REVISE

Conduct data processing by adopting specified intelligent chip, conduct nonlinearity revise and various kinds operations by utilizing softwares, 16 nonlinearity functions could be set.

HIGH RELIABILITY

Automatic fault checking, automatic repair for display and fault.

PROTECTION

Explode-proof and water-proof.

OVER RUNNING PRESSURE ALARM

HIGI would appear when flow over the setting value.

COMMUNICATION FUNCTION

Standard Connector RS485, Protocol MODBUS

MULTIPLE OUTPUT

can choose mass flow and temperature double-line output.



APPLICATION

  • Industrial And Process Gas Mass Flow.
  • Fuel Flow For Burners And Fuel Cells.
  • Nox Control Using Ammonia
  • Aeration Air And Digester Gas Waste Water Treatment Facilities
  • Compressed Air
  • Natural Gas
  • Combustion Air
  • Metering Semi-conductor Gases
  • Chloring Matering In Paper Industries
  • Solvent And Voc Recovery
  • Air Sampling
  • General Purpose Mass Flow, Rd.
  • Flow Calibration Standrards



AT SERIES THERMAL MASS FLOWMETER TECHNICAL SPECIFICATIONS:

AT series in-line thermal mass flow meter AT series insertion thermal mass flowmeter
  • Pipe Size : In Line Type: Ф6-Ф200mm, Insertion Type: Ф40-Ф10000mm
  • Power Supply : 24VDC±10%, ≥350mA (you can also use our private power supply DW2407), or 220VAC±10%
  • Output : 4-20mA load resistance ≤350Ω (750Ω optional) communication output, RS-485, MODBUS,
  • HART Power : dissipation <8W suitable>
  • Medium : All kinds of gases (pure & stable gases), except for acetylene
  • Display : Upper row cumulant flow displayed by ten digits, Bottom row instantaneous flow displayed by four digits (double rows displayed)
  • Accuracy : ±0.5%; ±1%
  • Medium Temperature : -40~120℃ (200℃ optional)
  • Rated Pressure : <2.5MPa G(<20MPa optional)
  • Environment Temperature : -40~50
  • Relative Humidity : 5%~90%
  • Atmospheric Pressure : 86~106Kpa
  • Straight Pipe : 15D, only 3D Up Scale and Down Scale Resp.
  • Explosion-proof Flame-proof: Exd ⅡCT3
  • Water-proo : Spraying protection type IP65, submerged type IP68
  • M.O.C (Wettes Parts) : 1Cr18Ni9Ti,316L(non-stick nano materials optional), 1Cr18Ni9Ti(non-stick nano materials optional)
  • Characteristics : Wide range----range proportion1:120 (exceptional1:1000)。Minimum flow rate is 0, Maximum flow rate could reach to 60m/s。intelligentialize----adopt the latest smart chip appeared at abroad In recent years, liquid crystal display with double row sixteen digits. Mass flow measurement----temperature and pressure are not needed for compensation, can measure and display the flow of gaseous mass or standard. Lower flow rate measurement----upper limit flow rate could be 0.5m/s, lower limit is 0. Display on-site----accumulated mass flow or standard cube flow, instantaneous mass flow or standard cube flow, flow percentage. Setting on-site----suited for all occasions, automatic identification and revise on-site according to different composition gas.


IN LINE THERMAL MASS FLOW METER


  • Pipe Line size: 25, 40, 50, 80, 100, 150, 200, 250, 300, 400
  • Explosion Proof : 1: Yes, 2: No
  • Installation Form: Integral, Remote, Submerge type
  • Output Signal: 1. Normal 4 to 20 ma,
  • Communication Output
  • Wetted Part M.O.C: 1 cr18Ni9Ti, 316L
  • Protect Class: IP 65, IP 68
  • Pressure: 1. 2.5 Mpa, 2. 6 Mpa, 3. 20 Mpa
  • Max. Flow Rate: Nm3/Hr. Kg/Hr, T/H
  • Medium

INSERTION THERMAL MASS FLOW METER


  • Pipe Line size: 25, 40, 50, 80, 100, 150, 200, 250, 300, 400
  • Explosion Proof : 1: Yes, 2: No
  • Installation Form: Integral, Remote, Submerge type
  • Output Signal: 1. Normal 4 to 20 ma,
  • Communication Output
  • Wetted Part M.O.C: 1 cr18Ni9Ti, 316L
  • Protect Class: IP 65, IP 68
  • Pressure: 1. 2.5 Mpa, 2. 6 Mpa, 3. 20 Mpa
  • Max. Flow Rate: Nm3/Hr. Kg/Hr, T/H
  • Medium


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