Development and assessment of a closed-loop pulsating heat pipe employing TiO2/SiO2 nanofluids utilizing metallic nanoparticles

• As an operating fluid, TiO 2 /SiO 2 nanofluid improves the efficiency of closed-loop pulsating heat pipes. • The presence of SiO 2 nanoparticles makes the TiO 2 /SiO 2 hybrid nanofluid unstable. • Compared to conventional fluids used in operations, the TiO 2 /SiO 2 hybrid nanofluid exhibits a reduced temperature resistance. • The increased amount of nanoparticles causes a boost in thermal conductivity. This study aims to investigate the potential improvements in Closed-Loop Pulsating Heat Pipes (CLPHPs) by utilizing hybrid nanofluids (HNFs) composed of metallic as well oxide nanoparticles. CLPHPs function through dual phase flow to transfer heat between evaporators and condensers, with their performance being heavily dependent on the thermal conductivity of the working fluid. This research examines the performance of CLPHPs using four different working fluids: titanium dioxide (TiO) and silicon dioxide (SiO) HNF, TiO 2 mono nano solvent, SiO 2 mono nano solution, and distilled water, across a range of operating conditions. A Closed-Loop Pulsating Heat Pipes was constructed and tested using four different working fluids. The study analyzed several operational parameters, including nanoparticle weight concentrations ranging from 0.2 % to 0.3 %, filling ratios between 60 % and 70 %, and heat inputs from 25 to 75 watts. The findings revealed that the TiO 2 /SiO 2 HNF reduced thermal resistance by 28 to 52 % compared to distilled water and by 15 to 40 % compared to mono nanofluids under identical operating conditions (filling proportion, nanoparticle concentration, as well heat input). These results indicate that the hybrid nanofluid significantly enhances heat transfer performance. The CLPHP filled with TiO 2 /SiO 2 HNF demonstrated optimal performance at a 70 % filling fraction and a nanoparticle weighted concentration of 0.3 %. Nevertheless, perpetuating solidity of TiO 2 /SiO 2 HNF remains a challenge, largely attributable to hydrophobic essence of SiO 2 nano components, which can affect their dispersion and long-term stability.