Flowmeters
For a good summary of the types and principles, see this article
- Orifices - cheap, but limitted turndown rate of 4:1. Actual flow is less than might be expected from the size of the orifice (coefficient of contraction). Flow ∝ √P
- Venturis - cheap. Turndown 10:1 with only about 20% pressure drop.
- Nozzles - comparable with orifices
- Pitot tubes - use a special case of the Bernoulli equation where the flow-velocity in the side tube is zero.
- Rotameters (Variable orifice). Turndown 12:1 and accuracy up to 1%
- Calorimetrics - e.g. hot-wire. Rate of heat loss ∝ v2 and varies with gas viscosity, density and SHC.
- Turbine - turndown of 100:1 with high accuracy under constant condtions
- Vortex - rate of vortex shedding proportional to flow rate, but depends on gas compositions.
- Electromagnetic
- Doppler
- Ultrasonic - measure transit time
- Thermal
- Coriolis