Effects of mixed anionic/cationic surfactants on ZnO nanofluid

Abstract

The thermal performance of the internal heat transfer fluid was an important factor affecting the heat transfer efficiency of the energy system. The metal oxide nanofluids with adding surfactants have proven to be an effective solution to enhance their stability and thermo-physical properties and prevent sedimentation of nanoparticles into the base fluid. The prime objective of the present work is to develop novel anionic/cationic mixed surfactants to enhance their dispersion in nanofluids and investigate their impact on the thermo-physical characteristics and stability of water-based ZnO nanofluids to be used in solar thermal systems. A two-step method was used to prepare ZnO nanofluids with mixed surfactant SDS/CTAB. Furthermore, its stability, thermophysical properties, and thermal performance enhancement ratio were investigated. ZnO nanofluids with mixed surfactant SDS/CTAB can maintain good dispersion stability for 7 days. The maximum thermal conductivity of ZnO nanofluids with mixed surfactant SDS/CTAB is 38 %. At 55 °C, 0.398 vol% ZnO nanofluids have a minimum viscosity of 0.645 mPa·s. Meanwhile, the performance enhancement ratio (PER) of ZnO nanofluids with different volume concentrations was less than 1.2, indicating good thermal performance.