Flashing liquids fragmentation: is there a hindered mass?
Résumé
We used a PDPA system in order to measure droplet size distribution inside flashing water jets at different temperatures (130-170°C), different pressures (0.5 - 1 MPa) and after two different nozzles (2 mm ID orifice; 2 mm ID - 100 mm long pipe).
Experimental size distirbution is compatible with literature data: mean diameter is generally between 60 and 100 µm. The new observation is that some dorplets (generally less than 5%) have diameters larger than 200 µm.
These large droplets account for more than 80% of the mass balance. They are observed whatever the inlet conditions, whatever the geometry of the exit nozzle (orifice or long pipe), whatever the distance from the orifice either on the jet axis or far from it.
These large droplets could result from an incompleteness of the flash fragmentation mechanism. But some questions remain unsloved: why do their diameters seem to be almost independent of the inlet conditions and also independent of the outlet geometry (orifice or pipe) evenif the fragmentation mechanism is probably different.