A potentially important factor in choosing an appropriate flowmeter technology is energy loss
caused by pressure drop. Some flowmeter designs, such as the common orifice plate, are inexpensive
to install but carry a high price in terms of the energy lost in permanent pressure drop (the total,
non-recoverable loss in pressure from the inlet of the device to the outlet, not the temporary pressure
difference between inlet and vena contracta). Energy costs money, and so industrial facilities would
be wise to consider the long-term cost of a flowmeter before settling on the one that is cheapest to
install. It could very well be, for example, that an expensive venturi tube will cost less after years
of operation than a cheap orifice plate.
In this regard, certain flowmeters stand above the rest: those with obstructionless flowtubes.
Magnetic and ultrasonic flowmeters have no obstructions whatsoever in the path of the flow. This
translates to (nearly) zero permanent pressure loss along the length of the tube, and therefore.
Thermal mass and straight-tube Coriolis flowmeters are nearly obstructionless, while vortex and
turbine meters are only slightly worse.