Experimental investigation of the effect of nanofluids on the thermal resistance of a thermosiphon L-shape heat pipe at different angles

This study aims to experimentally investigate the effects of water/SiO2 nanofluids on the thermal resistance of an L-shaped heat pipe. A wide range of parameters such as different nanoparticle dimensions of 11-14 nm and 60-70 nm, weight concentrations of 0.1 and 0.5 wt%, two heat pipe angles of 0 and 90 degrees, three evaporator's volume fractions of 80%, 90% and 100% and three different heat input of 5, 10 and 15 W have been taken into account for conducting this study. The results showed that thermal resistance decreased with the increase in weight concentrations to 0.5 wt% while it increased with the angle reduction. The maximum reduction in thermal resistance which was 24% observed in the nanoparticle dimension of 11-14 nm, the heat input of 10 W, weight concentration of 0.5 wt%, heat pipe angle of 90 and 100% of evaporator's volume fraction. Also, 16% of reduction in thermal resistance was also observed in case of 11-14 nm, 10 W of heat input, weight concentration of 0.5 wt%, heat pipe angle of 0 and 90% of evaporator's volume fraction. Finally, according to the results, it was observed that the increase in nanoparticle dimension affects the thermal resistance increasingly.