Kriti Singh¹, S. K. Sharma^1,, Shipra Mital Gupta²

The stability of nanofluid is the main challenge for their heat transfer applications. Stability means that dispersed solid nanoparticles in basefluid such as engine oil, ethylene glycol (EG), water do not aggregate at a significant rate. The addition of surfactant in basefluid is an excellent option to maintain the stability of nanofluid. This research’s major emphasis is in order to make stable nanofluid for thermal applications using different surfactants. Carbon nanotubes (CNT) nanoparticles are dispersed in water (DDW) with the help of SDS, GA and mixed surfactant (mixture of SDS and GA in 50:50 ratio) using a modified-two step method. Results showed that dispersion of CNT in basefluid was better at 1:1 surfactant/CNT ratio, 0.3 wt% of CNT concentration and 180 minutes (SDS), 150 minutes (GA), 90 minutes (mixed surfactant) ultrasonication time. Nanofluid prepared with SDS, GA and mixed surfactant were found to be stable upto about ~90 days, ~150 days and ~200 days, respectively. CNT nanofluid prepared with SDS, GA and mixed surfactant showed 33.9%, 46.3% and 54.3% enhancement in thermal conductivity as compared to DDW, respectively. According to the results, all three nanofluids can be used as a heat transfer fluid, but nanofluid prepared with mixed surfactant is more suitable because it showed higher thermal conductivity enhancement and better stability which are essential for heat transfer application.

stability, CNT nanofluid, surfactant, heat transfer, water, thermal conductivity