Increasing the stability of nanofluids with cavitating flows in micro orifices

Abstract

One of the most critical challenges for nanofluids in practical applications is related to their stability and reusability since a gradual agglomeration of nanoparticles in nanofluids occurs with time and is accelerated by heating. In this study, we propose a technique to maintain the performance and stability of nanofluids with the use of cavitating flows through micro orifices to prevent agglomeration and sedimentation of nanoparticles, which will increase the durability of the nanofluids. γ-Al2O3 (gamma-alumina) nanoparticles with a mean diameter of 20 nm suspended in water were utilized. In the current approach, a flow restrictive element induces sudden pressure, which leads to cavitation bubbles downstream from the orifice. The emerging bubbles interact with the agglomerated structure of nanoparticles and decrease its size through hitting or shock waves generated by their collapse, thereby increasing the stability and reusability of nanofluids. The method does not involve any use of expensive surfactants or surface modifiers, which might alter the thermophysical properties of nanofluids, may adversely influence their performance and biocompatibility, and may limit their effectiveness.