Drop formation from flat tip nozzles in liquid-liquid system

Correct estimation of interfacial area for heat or mass transfer is of primary importance in liquid-liquid contacting systems. But the existing correlations for the estimation of the sizes of drops formed by nozzles at low flow rate are based on experimental data using nozzles with tips filed down to sharp or bevel or a very thin thickness, and the inside diameters are used as the characteristic diameters. These correlations would underestimate the size of aqueous drops formed from flat tip metallic nozzles considerably, because as the drops are detached from the nozzle tips, the liquid-liquid-solid contact lines are not just located at the inside edge of the opening. In this work, the formation of drops of aqueous., from flat tip stainless steel nozzles of various dimensions into solutions of NaCl and AlCl3 from flat tip stainless steel nozzles of various dimensions into a pool of n-dodecane was studied experimentally. It was found that the deviation of the estimated drop sizes by the correlation of Kagan et al. differs only slightly from that of Scheele and Meister. The deviations of the estimated values are not affected by the dissolved salts within the range of concentrations studied. And most importantly, the mean deviation of the correlation of Scheele and Meister can be reduced to a few percents if different characteristic diameters, d(n), are used in the computation: d(n)=O.D. for the cases of relatively large nozzles of about 1 cm O.D. with wall thickness between 0.098 and 0.170cm; d(n)=1.15xO.D. for small thin wall nozzles of O.D. < 0.35cm with wall thickness <0.036cm. (C) 2001 Elsevier Science Ltd.