Thermal performances and characteristics of thermosyphon heat pipe using alumina nanofluids

The thermal performance of a double tube two-phase closed thermosyphon (DTTPCT) using alumina nanofluid as working fluid in startup, steady state and shut down modes has been experimentally and theoretically evaluated. Gamma-Alumina (γ-Al 2 O 3 ) nanoparticles with size of 40 nm were well dispersed, prepared and stabilized in distilled water base fluid at different particle concentrations.The axial wall temperature distribution, the nanofluid temperature along the thermosyphon, the thermal conductivity and overall heat transfer coefficient were investigated to propose the best combination of parameters by varying parameters such as concentration of nanoparticles, heat load on heat pipe. The effect of nanofluid volume fraction of 0.5%, 1.0%, 1.5%, and 2.0% with heat load of 500 W, 750 W, 1000 W and 1250 W on the overall thermal conductivity of the heat pipe were studied to evaluate the optimal thermal performance. The results indicate that the DTTPCT filled with alumina nanofluid in 2% volume fraction yields higher thermal performance when it is operated at 1000 W heat load. The experimental results show that the optimal thermal performance of TPCT filled with Al 2 O 3 /water nanofluid at a heat load of 1000 W is 3 times better than that of pipes using distilled water as the working fluid. Theoretical model describing both thermal performance and phase flow of the DTTPCT has been compared with the experimental results at start-up, steady-state and shut-down modes.