Heat transfer and flow characteristic of a flat confined loop thermosyphon with ternary hybrid nanofluids for electronic devices cooling

Abstract

The purpose of this study is to explore the feasibility of the application of ternary hybrid nanofluids in heat pipes and the effect mechanism of nanofluids on the operation performance of flat confined loop thermosiphon (FCLTS), which are also the novelty of this study. Al2O3:Cu:TiO2 ternary hybrid nanofluids with different mixing ratios and concentrations were prepared. The synergistic effect of thermal conductivity enhancement was analyzed to obtain the ternary hybrid nanofluids with the optimal mixing ratio of 4:2:4. Thermal performance of a FCLTS with Al2O3:Cu:TiO2 nanofluids was investigated. This study focused on the effect of nanofluid concentrations, heat loads and inclination angles. This study revealed a unique phenomenon that nanofluids could be cleverly attached to the upper heated surface of evaporator, i.e., above the liquid level, improving the wettability of the upper surface. The optimal inclination angle was 90° due to the gravity-assisted effect. In the coupling of assistance and resistance, the optimal concentration was 0.3 vol%. The lowest thermal resistance of 0.09 K/W and maximum heat transfer enhancement efficiency of 22.5 % were observed for nanofluids with concentration of 0.3 vol% at a heat load of 80 W and inclination angle of 90°. Compared with miniature loop heat pipe with single nanofluids or binary hybrid nanofluids in the literature, ternary hybrid nanofluids exhibit favorable heat transfer enhancement for FCLTS at lower cost. The research provides theoretical basis and technical support for heat pipe design.