Study of Parameters Affecting Size Distribution of Beads Produced from Electro-Spray of High Viscous Liquids

Abstract

<span style="font-family: TimesNewRomanPS-ItalicMT; font-size: 10pt; color: #000000; font-style: normal; font-variant: normal;"><em>Electro-Hydrodynamics (EHD) spray is an important process in many engineering</em> <span style="font-family: TimesNewRomanPS-ItalicMT; font-size: 10pt; color: #000000; font-style: normal; font-variant: normal;"><em>operations such as ink-jet printing, spray drying and atomization (liquid jet in air),</em> <span style="font-family: TimesNewRomanPS-ItalicMT; font-size: 10pt; color: #000000; font-style: normal; font-variant: normal;"><em>dispersion and emulsification (liquid jet in liquid). In this work the method of electrospray was employed to form droplets from a high viscous sodium-alginate solution</em> <span style="font-family: TimesNewRomanPS-ItalicMT; font-size: 10pt; color: #000000; font-style: normal; font-variant: normal;"><em>using constant DC voltage. The droplets were cured in calcium chloride solution to</em> <span style="font-family: TimesNewRomanPS-ItalicMT; font-size: 10pt; color: #000000; font-style: normal; font-variant: normal;"><em>produce solid beads. The main objective was to extend the knowledge of EHD spray to</em> <span style="font-family: TimesNewRomanPS-ItalicMT; font-size: 10pt; color: #000000; font-style: normal; font-variant: normal;"><em>high viscous and non-Newtonian liquids (1000-5000 mPa.s). However, the effects of</em> <span style="font-family: TimesNewRomanPS-ItalicMT; font-size: 10pt; color: #000000; font-style: normal; font-variant: normal;"><em>electric field strength, nozzle diameter, flow rate and concentration of liquid were</em> <span style="font-family: TimesNewRomanPS-ItalicMT; font-size: 10pt; color: #000000; font-style: normal; font-variant: normal;"><em>specifically investigated on the size of the beads. Among the parameters studied,</em> <span style="font-family: TimesNewRomanPS-ItalicMT; font-size: 10pt; color: #000000; font-style: normal; font-variant: normal;"><em>voltage had a pronounced effect on the size of the beads as compared to the flow rate,</em> <span style="font-family: TimesNewRomanPS-ItalicMT; font-size: 10pt; color: #000000; font-style: normal; font-variant: normal;"><em>the nozzle diameter and the concentration of alginate liquid. The size of beads was</em> <span style="font-family: TimesNewRomanPS-ItalicMT; font-size: 10pt; color: #000000; font-style: normal; font-variant: normal;"><em>reduced to a minimum value by increasing the voltage in the range of 0-10 kV.</em> <span style="font-family: TimesNewRomanPS-ItalicMT; font-size: 10pt; color: #000000; font-style: normal; font-variant: normal;"><em>However, within the middle part of this range, an unstable transition occurred from the</em> <span style="font-family: TimesNewRomanPS-ItalicMT; font-size: 10pt; color: #000000; font-style: normal; font-variant: normal;"><em>dripping mode to the jet mode where the size distribution was wide. Increasing the</em> <span style="font-family: TimesNewRomanPS-ItalicMT; font-size: 10pt; color: #000000; font-style: normal; font-variant: normal;"><em>height of fall of the droplets improved the sphericity of the beads, because of the</em> <span style="font-family: TimesNewRomanPS-ItalicMT; font-size: 10pt; color: #000000; font-style: normal; font-variant: normal;"><em>increase of flight time for the droplets to relax before gelation.</em> </span></span></span></span></span></span></span></span></span></span></span></span></span><br style="font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px;" /><br class="Apple-interchange-newline" /></span></span>