Advantages of Thermal Mass Flowmeter | disadvantages of Thermal Mass Flowmeter
This page covers advantages and disadvantages of Thermal Mass Flowmeter. It mentions Thermal Mass Flowmeter advantages or benefits and Thermal Mass Flowmeter disadvantages or drawbacks.
What is Thermal Mass Flowmeter?
• This meter can be built by measuring temperature differential i.e. it works based on principle of measuring heat transfer.
• It measures fluid mass flow rate by heat convection from heated surface to the flowing fluid.
• There are two types of thermal mass flowmeter viz. thermal dispertion or immersible type and capillary tube type.
• In thermal dispertion type, heat is transferred to boundary layer of fluid flowing over the heated surface.
• In capillary tube type, heat is transferred to bulk of the fluid flowing through small and heated capillary tube.
• The figure-1 depicts thermal mass flowmeter. As shown, the
two RTD sensors are used in its construction.
One of the sensors is self heated (known as flow sensor) where as
the other sensor (known as reference sensor) measures gas temperature.
Sensors are installed as part of probe in insetion style or
they are inserted in the pipe section itself as in-line flowmeter.
• The electric power needed to maintain constant temperature differential is directly proportional to gas mass flow rate.
Benefits or advantages of Thermal Mass Flowmeter
Following are the benefits or advantages of Thermal Mass Flowmeter:
➨It is used for measurement of direct gas mass flow.
➨It works independent of pressure, density and viscosity.
➨It offers higher accuracy.
➨It has very low drop in pressure.
➨Pressure and temperature compensation is not required.
➨It has large span.
➨It has no moving parts.
➨It is rugged in construction.
➨It has short response time.
➨It can be easily sterilized.
Drawbacks or disadvantages of Thermal Mass Flowmeter
Following are the drawbacks or disadvantages of Thermal Mass Flowmeter:
➨It is used for gas measurements only.
➨It requires inlet and outlet sections.
➨Condensation of moisture in saturated gases on temperature detector will cause thermometer to read low. Moreover coating as well as material build up on sensor will inhibit heat transfer. This causes meter to read low.
➨The other sources of error in meter readings include variation in specific heat caused due to changes in cmposition of gas.
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