Particle Velocity Probes Anemometers and Sensors

Particle velocity measurement in multiphase systems can be approximately categorized as invasive (probes, impaction devices) and noninvasive (rings, coils, optical beams). Yan (1996) has further detailed particle velocity measurement according to (1) Doppler methods laser and microwave (2) Cross-correlations methods capacitance, electrodynamic, acoustic or 

The electronics utilized a charge sensing op-amp (operational amplifier) with rapid signal decay (circuit RC = 0.11 or 0.64 ms) that converted the charge disturbances at either end of the probe end into separate voltage 

An alternative and indirect approach to measuring particle velocity ud using particle charge is to measure the mass flux and the effective density of the dispersed phase (particles) and apply the relationship 

The effective density Pd ad of the dispersed phase is determined by a capacitance measurement of the solids voidage ad (with pd known). 

FIGURE 3-21 Computer output signals (right) from two pairs of coils (left) showing a correlation of signals for 450 pm glass particles in PVC pipe at upstream and downstream locations (Klinzinget. al. 1987). 

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