Experimental Investigation of Stability and Thermophysical Properties of <scp>CNT</scp> /Water Nanofluid Stabilized by Mixed Surfactant ( <scp>SDBS</scp> and Triton X‐100)

ABSTRACT Researchers have focused on replacing conventional fluid with nanofluid in heat transfer system to improve their efficiency. Carbon nanotubes (CNT) are known to improve the thermal properties of these fluids but their dispersion in aqueous medium is difficult. A stable nanofluid of CNT is prepared by using Triton X‐100, SDBS (Sodium dodecyl benzene sulfonate) and mixed surfactant at optimized ultrasonication time (180 min) and centrifugation time (120 min). CNT/surfactant ratio was also optimized for Triton X‐100 (1:1.5), SDBS (1:1.5) and mixed surfactant (1:1) based nanofluid. Stability of CNT nanofluid was analyzed by measuring absorbance and zeta potential. Nanofluid prepared with Triton X‐100, SDBS and mixed surfactant remained stable up to 180 days. Thermal conductivity of mixed surfactant‐based nanofluid was greater than that of individual surfactant‐based nanofluid. Thermal conductivity enhancement of Triton X‐100, SDBS and mixed surfactant‐based CNT nanofluid was found to be 54.47%, 56.14% and 77.35% as compared to basefluid, respectively. Based on this investigation, mixed surfactant‐based nanofluid is a more appropriate heat transfer fluid for solar harvesting system.