period two

Chilled-Water System Design

notes

Types of Fluid Flow Meters

Pressure-based

Pitot tube

Venturi

Orifice plate

Differential pressure

Turbine and impeller

Vortex

Magnetic

Ultrasonic

Figure 63

The direction and quantity of flow in the bypass pipe may be determined either directly by using a flow meter or indirectly by sensing temperatures.

Direct flow measurement can be accomplished using a variety of flow-meter technologies. These include pressure-based flow meters (pitot tubes, venturi meters, orifice plates, and differential pressure sensors), turbine and impeller meters, vortex meters, magnetic flow meters, and ultrasonic transit-time meters. The accuracy, ease of installation, required maintenance, and cost of these meter technologies vary widely. The accuracy and reliability of the flow meter will directly impact the efficiency and reliability of the chilled-water system. High-quality flow meters are critical to proper system operation.

When using a flow meter, it is important to understand the range of flows and velocities that the specific device can accurately measure. The accuracy of some flow meters is dependent on the velocity of the flow and the development of a smooth flow profile in the stream being measured. To obtain accurate measurements, several diameters of straight pipe may be required, both upstream and downstream of the meter. Finally, in order to give accurate results, many types of flow meters require periodic calibration. This is often overlooked in the maintenance of chilled-water systems.

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Trane TRG-TRC016-EN manual Types of Fluid Flow Meters, Pressure-based, Turbine and impeller Vortex Magnetic Ultrasonic