Low pressure hydrodynamic cavitating device for producing highly stable oil in water emulsion: Effect of geometry and cavitation number

In present work, the detailed geometrical analysis of hydrodynamic cavitating devices was carried out to investigate the effect of geometry (orifice and venturi of different shapes) and geometrical parameters on the formation and stability of mustard oil in water nanoemulsion. The optimization of geometrical parameters was carried out based on the lowest droplet size obtained and droplet size reduced per unit pass. It was observed that the single hole orifice plate of circular shape having lower perimeter and higher flow area than other orifice devices, was found to be an efficient device which produced emulsion of lowest droplet size i.e. 87 nm at an optimum C_V of 0.19 (10 bar optimum operating pressure) in 90 min of processing time. Moreover, it was found that the kinetic stability of the nanoemulsion assessed under centrifugal and thermal stress conditions remained unaffected by these forces. The prepared nanoemulsion using hydrodynamic cavitation (HC) was found to be physically stable up to 3 months indicating the potential of HC over high energy techniques for producing highly stable emulsion with droplet size below 100 nm on a large scale. Furthermore HC was found to be 11 times energy efficient than acoustic cavitation/ultrasonication for the preparation of nanoemulsion.