What Is a Differential Pressure Flowmeter?
A differential pressure flowmeter is a flowmeter that measures fluid flow rate by detecting the pressure difference created as the fluid passes through a conduit. This pressure difference, typically generated across a constraining structure like an orifice plate, is used to calculate the flow rate. Differential pressure flowmeters offer a cost-effective solution compared to other flowmeter types and are suitable for high-temperature and high-pressure environments. However, they can have a limited measuring range and may incur high-pressure loss.
Uses of Differential Pressure Flowmeters
Differential pressure flowmeters are versatile tools employed in various fields:
- Environmental Measurement: For monitoring industrial furnace exhaust gas flow rates.
- Power Plants: In hydroelectric plants for measuring water flow rate, and in thermal power plants for monitoring steam in boiler and turbine systems.
- Leisure Facilities: Such as hot spring resorts, to control steam flow rate for heating efficiency.
Principle of Differential Pressure Flowmeters
The operational principle is based on Bernoulli’s theorem. A constraining structure, like an orifice, is installed in the pipeline, causing a velocity increase and pressure decrease in the fluid. Pressure sensors measure the differential pressure upstream and downstream of the structure. This differential pressure, proportional to the square root of the flow rate, allows for flow rate estimation.
Stable flow before the orifice is essential for accurate measurement, requiring a straight pipe length of 5 to 10 times the pipe diameter before the orifice.
Differential Pressure Flowmeter Types
Differential pressure flowmeters come in various forms:
- Orifice Plate Flowmeter: Uses an orifice plate with circular or oval holes to measure fluid flow rate, commonly used for steam and exhaust gas measurement.
- Venturi Meter: Features a conical constricted section, offering high accuracy and suitability for a wide range of flow rates.
- Pitot Tube Flowmeter: Utilizes a conical probe to measure pressure differences caused by fluid velocity changes, especially effective for gas flow rate measurement.