This chapter explains the manner in which this new method, the “Flow Measurement Method Based on Reaction Force”, ensures flow measurement based on the measurement of the reaction force generated by the measured fluid.

The Method principle consists in the measurement of the fluid mass flow rate Q m by putting in evidence of the fluid reaction force F R =F R (Q m 2) that is proportional to Q m 2, and its measurement, directly or by its effects.

The Flow Measurement Method Based on Reaction Force provides for all types of reaction flowmeters, the F R generation by the same common specific configuration of the fluid-flowing path through the flowmeter, named “the reaction measurement system”, consisting of a pair of two distinct functional parts: the immobile “inlet tube”, and the potential mobile “reaction element” (reaction tube or reaction drum).

The measured fluid enters the flowmeter through the inlet tube, fixed rigidly to flowmeter housing, for all types of reaction flowmeters, and then is transferred, by a free coupling, to the reaction element that, under the reaction force effect, tends to rotate.

By balancing this tendency, F R measurement is ensured. Flow rate Q m is calculated by using its relationship with F R .