THE EFFECTS OF SURFACTANTS ON THE MOTION AND TRANSPORT MECHANISMS OF A CONDENSING DROPLET IN A HIGH REYNOLDS-NUMBER FLOW

The motion and transport mechanisms of a condensing droplet initially contaminated with insoluble monolayer surfactant material are examined through a theoretical approach. The surface tension gradient force induced by the surfactant and the shear stress from the relative motion between droplet and its ambient vapor are evaluated on the droplet surface as major forces affecting the internal motion of the droplet. The strength of the internal motion ranges from one order of magnitude smaller than the free stream velocity for slight surfactant contamination to almost a complete stop in motion for high surfactant concentration. This work is pertinent to boiling heat transfer, two phase flow, combustion of fuel droplets, spray drying, and mass transfer.