Experimental Studies on Drop Formation at the Tip of Melting Rods

Drop formation at the conical tips of melting rods has been experimentally studied using the transparent wax-alcohol/acetonitrile system. The effects of cone angle, rod diameter, immersion depth, and bath temperature on the detached drop mass have been studied over a wide range, besides recording useful qualitative information based on visual observation. The experimental results suggest that the phenomenon of drop formation at the tip of melting rods has a close parallel with the drop formation at conical tips, at least on a qualitative basis. However, the results could not be quantified owing to difficulties in characterizing the physical properties of the system, despite efforts to minimize them.

Flow of liquid/liquid dispersions in a Hele-Shaw cell

Flow of liquid/liquid dispersions have been investigated in a Hele-Shaw cell which contained a thin disk held between two parallel plates. This device offers a well defined flow field and also permits visual observation of the dispersed drop movement. The dispersed drops coalesce with the disk for the systems where the dispersed phase wets the disk surface. The dispersed phase accumulate at the downstream end of the disk and they detach from there as blobs. Through an accurate measurement of accumulated dispersed phase volume, the coalescence rate was determined. The coalescence efficiency in the Hele Shaw cell is determined by dividing the coalescence hate by the undisturbed flow rate of the dispersed phase through an area equal to the projected area of the disk on a plane normal to the flow direction. The coalescence efficiency first increases and then decreases with the flow rate of dispersion. The coalescence rate/disk dimensions increases with the decrease in the disk dimensions. The rate of coalescence increases with the increase in the dispersed drop diameter and it decreases with the increase in the continuous phase viscosity. The presence of surfactants reduces the coalescence rate. All these results are quantitatively explained through a model, which takes into account several important features like various mechanism of drainage, the roles of dispersion and continuous phase viscosities, and the drop deformation.