Current research on the Poly(N-isopropylacrylamide) (PNIPAM)-coated 30–40 nm silica particles (SiO₂) is integrated with deionized (DI) water via the ultrasonication method to overcome the variations in thermal conductivity, poor stability, and limited heat transfer with conventional DI water. During the investigation, the PNIPAM-coated SiO₂ concentration was varied at 0.2 vol%, 0.4 vol%, 0.6 vol%, and 0.8 vol% under forced convection. The thermal performance of heat transfer fluid (HTF) and the reduction of specific heat capacity were studied, and the results are compared with the base (DI water). The results showed that the DI water embedded with 0.6 vol% of PNIPAM-coated SiO₂ exhibited superior thermal performance, like enhanced thermal conductivity (0.706 W/mK at 80 °C), decreased specific heat (4107 J/kg · K), increased viscosity of 1.04 mPa·s, improved heat transfer coefficient of 500.4 W/m2.K, and enhanced stability (98%). Overall, the 0.6 vol% PNIPAM–SiO₂ nanofluid exhibited an optimal balance of high thermal conductivity, heat transfer performance, and stable dispersion, suggesting strong potential for advanced thermal management in heat exchangers and solar thermal systems.
Deepati et al. (Sun,) studied this question.